ICFN7
Sundial I and II
Sundial Beach Resort
*** Dear ICFN7 Colleagues,
As you have likely heard in the news, Sanibel Island has significant damage from hurricane Ian. Sundial management has just informed us that they will not be able to host a conference in November. They will begin working on refunding deposits, but please have patience as they have many issues to deal with. Our thoughts are with the people of Florida and we wish them a speedy recovery.
We have discussed options and we think that given the character of the meeting it would be best to postpone the conference and investigate holding it next year, perhaps at the Sundial. For now we will begin the process to refund your conference registrations. As further information becomes available, we will pass it along.
If you have any comments or suggestions, please email icfn7@frib.msu.edu. We would like to read them. ***
The 7th International Conference on "Fission and Properties of Neutron-Rich Nuclei" (ICFN7) will be held November 6th to November 12th, 2022 at the Sundial Beach Resort on Sanibel Island in Florida, United States. The conference is sponsored by the Facility for Rare Isotope Beams (FRIB), Vanderbilt University, and Los Alamos National Laboratory.
ICFN7 is the continuation of a long series of topical conferences on fission and properties of neutron-rich nuclei that started in 1997. The scope of ICFN7 will be similar to that of previous ones held in Scotland, and Sanibel Island in US. Invited and contributed speakers will present recent results of theoretical and experimental studies and future prospects in the following areas:
• Fission Modes and Reactions: Neutron-induced fission, photo-fission, charged particle-induced fission, Coulomb fission, fusion-fission.
• Fission Processes: Neutron and gamma multiplicities, energy spectra, prompt and beta-delayed emissions, fragment properties in energy and spin, fission fragment spectroscopy, cold fission, ternary fission, fission isomers, fission product yields.
• Properties of Neutron-rich Nuclei: Decay properties, masses, nuclear structure, nuclear astrophysics.
• Fragmentation and Accelerated Beams of Neutron-rich Nuclei: Coulomb excitation, transfer reactions, deep inelastic collisions and present and future facilities for rare isotope beams.
• Superheavy Elements: Current status of super heavy element research, decay spectroscopy, chemistry of SHE, production methods and current and future facilities.
The best way to reach Sanibel Island is to fly to the Southwest Florida International Airport (Fort Myers, Florida). The distance from the Southwest Florida International Airport to the Sundial Beach Resort (Sanibel Island, Florida) is 27 miles (see Google map ).
Delegates registration will start at 2:00 PM on Sunday, November 6, 2022.
- Aaina Thapa
- Adam Anthony
- Alexander Volya
- Alexandra Gade
- Alfredo Estrade
- Amy Lovell
- Anastasia Georgiadou
- Anatoli Afanasjev
- Ani Aprahamian
- Anjali Rani
- Anna Kwiatkowski
- ARIJIT SEN
- ARMEL MONIPANG MVOUING
- Artemis Spyrou
- Aurel Bulgac
- Benjamin Kay
- Bertis Rasco
- Bertis Rasco
- Betty Tsang
- Bradley Sherrill
- Carlos Bertulani
- Carolyn Raithel
- Charles Horowitz
- Chloé Fougères
- Christian Ross
- Christoph Duellmann
- Chun Yuen Tsang
- Dan Bardayan
- Daniel Lay
- Dariusz Seweryniak
- Daryl Hartley
- David Regnier
- Diego Ferney Rojas Gamboa
- Divya Arora
- Dongwi H Dongwi
- Elizabeth Deliyski
- EMANUELE VARDACI
- Enhong Wang
- Eric Flynn
- Erika Holmbeck
- Esther Leal Cidoncha
- Eun Jin In
- Filomena Nunes
- Forrest Friesen
- Fredrik Tovesson
- Gabriele-Elisabeth Koerner
- George Bertsch
- Gerd Roepke
- Gerhart Steinhilber
- Grigory Rogachev
- Guillaume Scamps
- Guy Savard
- Heather Crawford
- Heikki Penttilä
- Helena Albers
- Hideyuki Sakai
- Hiroyoshi Sakurai
- Ionel Stetcu
- Israel Mardor
- Jolie Cizewski
- Jorgen Randrup
- Jose Javier Dobon
- Joseph Hamilton
- Joseph Natowitz
- Julia Even
- Julien TAIEB
- Jutta Escher
- Kajol Chakraborty
- Kamila Zelga
- Kay Kolos
- Kazuki Okada
- Keegan Kelly
- Krzysztof Rykaczewski
- Kyle Beyer
- Kyle Brown
- Kyle Godbey
- Lee Riedinger
- Lucas Snyder
- Marc Verriere
- Maria Anastasiou
- Matthew Devlin
- Matthew Mumpower
- Michael Block
- Michael Wiescher
- Miguel Madurga Flores
- Nathan Giha
- Navin ALAHARI
- Nicholas Mendez
- Nicolas Schunck
- Nicole Vassh
- Nikolaos Patronis
- Nitin Sharma
- NORRIS JOHNSON
- Oleg Tarasov
- Pablo Giuliani
- Panagiotis Gastis
- Patrick Talou
- Paul Fallon
- Pierre Morfouace
- Radomira Lozeva
- Ramona Vogt
- Ranjan Sariyal
- Remco Zegers
- Richard Gumbel
- Robert Grzywacz
- Sait Umar
- Saori Pastore
- Satoshi Chiba
- Sean Finch
- Shruti -
- Soumik Bhattacharya
- Stefan Frauendorf
- Stephan Pomp
- Sylvester Agbemava
- Takaharu Otsuka
- Thomas Aumann
- Tsuyoshi Yaita
- Vibhuti Vashi
- Vincent Wende
- Vladimir Gudkov
- Walid Younes
- Walter Loveland
- William Walters
- Witold Nazarewicz
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Registration Sandpiper (Sundial Breach Resort)
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Introduction: Plenary Sundial I and II
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Sundial Beach Resort
1451 Middle Gulf Drive Sanibel, FL 33957-
08:15
Welcome 10mSpeaker: Bradley M. Sherrill (NSCL)
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08:25
Recent advances and future trends in fission physics 30m
Fission plays an important role in a wide range of applications: in nuclear astrophysics, as a mechanism for making elements far from stability for study in the laboratory, in the survival probability of superheavy elements, in the industrial production of energy, and as a prototypical example of large amplitude collective motion in quantum many body theory. Reconstructing in detail the sequence of events leading up to scission remains a challenge for both theorists and experimentalists. At the same time, the last few years have seen significant advances in the application of microscopic and macroscopic-microscopic approaches to fission, progress in computational methods, as well as new measurements that fill in crucial gaps in fission data and probe new regions of the nuclear chart relevant to this phenomenon. All in all, many critical open questions remain and fission continues to be a thriving area of study. In this talk I will discuss the status of the field and where we might be headed in light of the advent of new data and production techniques on the experimental side, and new advances in tools and methodologies on the theory and computational sides.
This work was supported by the US Nuclear Data Program at LBNL under contract DE-AC02-05CH11231 (LBNL).Speaker: Walid Younes (Lawrence Berkeley National Laboratory) -
08:55
Facility for Rare Isotope Beams Capabilities, Outlook, and International Context 30m
There are approximately 300 stable and 3,000 known unstable (rare) isotopes. Estimates are that over 7,000 different isotopes are bound by the nuclear force. It is now recognized that the properties of many yet undiscovered rare isotopes hold the key to understanding how to develop a comprehensive and predictive model of atomic nuclei, to accurately model a variety of astrophysical environments, and to understand the origin and history of elements in the Universe. Some of these isotopes also offer the possibility to study nature's underlying fundamental symmetries and to explore new societal applications of rare isotopes. This presentation will give a glimpse of the opportunities that arise at the Facility for Rare Isotope Beams (FRIB) which just went online at Michigan State University.
Speaker: Alexandra Gade (NSCL/MSU) -
09:25
Prospects for New Facilities Based on Multi-Nucleon Transfer Reactions 30m
Exploration of the nuclear landscape progresses via the ability to produce and isolate nuclei in new regions of the chart of nuclides. The existing radioactive beam facilities rely mainly on fragmentation, spallation, fusion-evaporation and fission reaction mechanisms to access the various areas of that chart. These reaction mechanisms each have strengths and weaknesses, both in production and associated separation capabilities, and together have been used to cover an impressive area of the nuclear chart. There remains however regions where none of these reaction mechanisms provide large enough production cross-sections to yield adequate access. This can be overcome by either building more and more powerful facilities using the same reaction mechanisms or looking for an alternate means of production with larger cross-sections.
The approach I will discuss uses multi-nucleon transfer reactions to access regions poorly populated by standard techniques. These reactions are most effective at energies slightly above the Coulomb barrier and occur when the surfaces of the nuclei graze each other, resulting in reaction products emitted over a large angular cone. So while the cross-sections offered by this approach are often very advantageous, the large emission cone makes the collection and separation of these recoils very challenging. This has limited the usefulness of these reactions in radioactive beam facilities so far but a number of efforts are taking place worldwide to harness their potential. An overview of these efforts will be presented, together with a more detailed look at a specific development, the N=126 factory, which is nearing completion at ATLAS. This facility will use the high intensity beams from ATLAS, combined to gas catcher technology similar to that developed for CARIBU to collect and separate the reaction products, to provide access to very neutron-rich isotopes outside of the fission peaks.
*This work was supported by the US DOE, Office of Nuclear Physics, under contract DE-AC02-06CH11357.
Speaker: Prof. Guy Savard (Argonne National Laboratory) -
09:55
How Close are We to a Predictive Model of Nuclei, Their Interactions, and Fission 30mSpeaker: Saori Pastore (Washington University in St Louis)
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Fission in astrophysics: potential observables and nuclear data needs 30m
Nicole Vassh1
1TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada
The field of nuclear astrophysics has grown tremendously within the last 65 years and has gained even more momentum recently given the dawn of new multi-messenger capabilities. We have now seen heavy element formation in the act via the signature of lanthanide elements on the observed light curve from the merger of two neutron stars. Such unprecedented abilities provide the opportunity to make big leaps in our understanding of the astrophysical origins of the elements if we can properly interpret such observables. An outstanding issue which directly impacts our interpretation of nucleosynthesis observables lies in modeling the production of actinides in astrophysics. For instance, it remains unknown how high of a mass number astrophysical environments are able to reach before the nucleosynthesis is terminated by fission. Stellar spectroscopy and meteorites have revealed the presence of uranium, thorium, plutonium, and curium, showing that astrophysical phenomena are capable of synthesizing up to at least atomic number 96 and mass number 247. But which astrophysical events are responsible for such heavy species? Although neutron star mergers are a viable candidate we currently have no direct evidence for actinide production in such environments. Using observables to unravel the mystery of the astrophysical sites of actinide production and their nucleosynthesis reach requires careful consideration of the impact of the nuclear physics uncertainties associated with the vastly uncharted territory of neutron-rich actinides. Recent work over the last few years has introduced several potential observable signatures of fission, from late-time fission heating effects on merger light curves, to MeV gamma-rays unique to the fission process, as well as hints of fission products in metal-poor star abundance patterns. I will discuss these potential fission observables with an emphasis on the impact of the unknown properties of neutron-rich actinides and highlight the nuclear data needed in order to move toward an understanding of the ultimate termination point of heavy element synthesis.*This work acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC) as well as support by the Fission In R-process Elements (FIRE) topical collaboration in nuclear theory, funded by the U.S. Department of Energy.
Speaker: Nicole Vassh (Triumf, CA)
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Coffee Break 30m Sundial I and II
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Sundial Beach Resort
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Fission I: Plenary Sundial I and II
Sundial I and II
Sundial Beach Resort
1451 Middle Gulf Drive Sanibel, FL 33957-
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Overview of the Experimental Fission Program at SOFIA GSI 25mSpeaker: Julien TAIEB (CEA)
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Theoretical description of fission yields: Toward a global model 25m
Recently, we have proposed a fast an efficient model of fission fragment distributions [Sadhukhan, Guliani, and Nazarewicz, Phys. Rev. C 105, 014619 (2022)]. The fission trajectories are obtained within the density functional theory framework, allowing for a microscopic determination of the most probable fission prefragment configurations. Mass and charge yield distributions are constructed by means of a statistical approach rooted in a microcanonical ensemble. The proposed hybrid model can reproduce experimental mass and charge fragment yields, including the odd-even staggering for a wide range of fissioning nuclei. Experimental isotopic yields can be described within a simple neutron evaporation scheme. We also explore fission fragment distributions of exotic neutron-rich and superheavy systems.
Speaker: Prof. Witold Nazarewicz (FRIB, MSU) -
12:15
The experimental fission program at n_ToF, CERN 25m
In this contribution the fission experimental programme at the CERN n_TOF facility will be presented. Neutron-induced fission reactions play a crucial role in a variety of fields of fundamental and applied nuclear science. Concerning basic nuclear physics research, they provide important information on the properties of nuclear matter, while in nuclear technology they are at the basis of present and future reactor designs. Furthermore, there is a renewed interest in fission reactions in nuclear astrophysics due to the important role of fission recycling in r-process nucleosynthesis.
Following the 2nd CERN Long Shutdown Period during the years 2019-2020, significant upgrades were realized at the n_TOF and our fission programme is ready to restart. The major upgrades will be presented along with available instrumentation. Additionally, lessons and gained experience from the previous studies within our facility will be discussed along with future measurements plans.Speaker: Prof. Nikolaos Patronis (1European Organization for Nuclear Research (CERN), Geneva, Switzerland) -
12:40
Energy Dependent Fission Product Yields from Neutron Induced Fission 25m
Energy Dependent Fission Product Yields from Neutron Induced Fission
Anton P. Tonchev1,4, Anthony Ramirez1, Ron Malone1, Jack A. Silano1, Roger Henderson1, Mark A. Stoyer1, Nicolas Schunck1, Matthew E. Gooden2, Jerry Wilhelmy2,
Werner Tornow3,4, Calvin R. Howell3,4, Sean Finch3,4, FNU Krishichayan3,41 Lawrence Livermore National Laboratory, Livermore, California 94550, USA
2 Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545, USA
3 Triangle Universities Nuclear Laboratory, Durham, North Carolina, 27708, USA
4 Department of Physics, Duke University, Durham North Carolina, 27708, USAFission product yields (FPY) are essential ingredients for addressing questions relevant to a range of basic and applied physics. Examples include the cosmic nucleosynthesis processes that created the elements from iron to uranium, decay heat release in nuclear reactors, reactor neutrino studies, radioisotope production, development of advanced reactor and transmutation systems, and many national security applications. While new applications will require accurate energy-dependent FPY data over a broad set of incident neutron energies, the current evaluated FPY data files contain only three energy points: thermal, fast, and 14-MeV incident energies. The goal of this study is to provide high-precision and energy dependent FPY data using monoenergetic neutron beams with energies between 0.5 and 15 MeV.
Absolute cumulative fission product yields have been determined for about 100 fission products representing 40 mass chains during neutron-induced fission of 235U, 238U, and 239Pu. Using rapid belt-driven irradiated target transfer system (RABITTS) [1] and irradiations with varying duration, gamma-ray decay history of fission products between 1 second to a few days have been measured. The number of fissions during the irradiation times was determined via a dual fission ionization chamber loaded with thin electroplated foils with the same actinide material. The obtained new FPY data provides a complete picture of the fission product yield landscape; from the initial distribution produced directly by fission, through the complex, time-dependent evolution of the yields from beta-decay and neutron emission [2]. This work also provides a unique capability to bridge short-lived fission product yields to our measured long-lived chain fission yields [3]. An overview of the recent experimental results obtained by the LLNL-LANL-TUNL collaboration will be presented. The FPY results will be discussed in terms of their energy and target-mass dependency.
[1] S. Finch et al., Nuc. Instrum. Meth A 1025, 166127 (2022).
[2] A. Tonchev et al., EPJ Web of Conference 239, 03001 (2020).
[3] M. Gooden et al., Nucl. Data Sheets 131, 319 (2016).This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.
Speaker: Anton Tonchev (Lawrence Livermore National Laboratory) -
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The Role of Angular Momentum in Fission 25m
The Role of Angular Momentum in Fission†
R. Vogt1
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2 and J. Randrup3
1Nuclear and Chemical Sciences Division,
Lawrence Livermore National Laboratory, Livermore, CA 94551, USA
2Physics and Astronomy Department, University of California at Davis, Davis, CA 95616, USA
3Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
The role of angular momentum in fission has generated a great deal of attention recently. Recent data
has shown that, while the fission fragment spins may be thought to emerge highly correlated, the resulting
measured fragment spins were shown to be largely uncorrelated. A number of theoretical treatments were
discussed at a workshop in Seattle in June 2022. This talk will summarize some of the advances presented
at that workshop, with some emphasis on the fission simulation model FREYA which is well suited for
studying the role of angular momentum in fission because it can easily simulate a variety of scenarios that
generate fragment spin and determine the observational consequences.
†The work of R.V. was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National
Laboratory under Contract DE-AC52-07NA27344. The work of J.R. was performed under the auspices of the U.S. Department
of Energy by Lawrence Berkeley National Laboratory under Contract DE-AC02-05CH11231.Speaker: Ramona Vogt (LBL )
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Hosted Lunch 1h Sundial I and II
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Neutron Rich I: Plenary Sundial I and II
Sundial I and II
Sundial Beach Resort
1451 Middle Gulf Drive Sanibel, FL 33957-
14:30
The Chi-Nu Project at Los Alamos National Laboratory 25m
Predictive capabilities for the behavior of nuclear systems driven by neutron-induced fission rely heavily on an accurate understanding of input nuclear data. The energy spectrum of neutrons promptly emitted from neutron-induced fission, i.e., the prompt fission neutron spectrum (PFNS), is of fundamental importance for these systems. Over the last decade the Chi-Nu experimental team at Los Alamos National Laboratory and Lawrence Livermore National Laboratory have developed a dedicated experimental campaign for high-precision, thoroughly-documented measurements of the PFNS as a continuous function of incident and outgoing neutron energy for neutron-induced fission of $^{239}$Pu, $^{235}$U, $^{238}$U, $^{240}$Pu, and more at the Los Alamos Neutron Science Center (LANSCE). Throughout the development of this project, new techniques for, e.g., random-coincidence background measurements and uncertainty quantification were established. Each experimental result form the Chi-Nu project is also reported with rigorously-defined covariance matrices correlating all measured outgoing neutron energies across all measured incident neutron energies, thereby enabling statements to be made regarding the energy dependence of the PFNS that are not possible with any other PFNS measurement to date. Lastly, the correlations between measurements on each isotope are explored as a part of the analysis of each new data set, which allows for accurate statements to be made regarding the ratios of the PFNS of each isotope to one another. All of these topics will be discussed with future plans for Chi-Nu measurements LANSCE.
Speaker: Dr Keegan Kelly (LANL) -
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Large scale collective motion at VAMOS++@GANIL: A laboratory for structure and reactions 25m
The GANIL facility provides a wide range of stable and short-lived unstable beams (ISOL and fragmentation) and more recently, intense beam of neutron has been added to this repertoire. Coupling these with a variety of unique and state-of-the-art equipment’s allows study of the evolution of the properties of the quantum many body system, the nucleus, as a function of the three axes of nuclear physics, namely excitation energy, angular momentum and isospin.
The upgraded VAriable MOde Acceptance Spectrometer (VAMOS++), one such device, is a versatile large acceptance spectrometer capable of isotopic identification and additionally measuring angular distributions of the reaction products ranging from low Z to fission fragments over a wide range of energies. VAMOS++ can be efficiently coupled with a large variety of -ray and charged particle detector arrays.
Here we will focus on the recent work at VAMOS++ using isotopically identified fission fragments. The talk will cover a few recent investigations addressing the evolution of nuclear structure as a function of spin and isospin, using a combination of AGATA and EXOGAM, and further insights into the dynamics of the fission process.
Speaker: Dr navin ALAHARI (GANIL) -
15:20
Observation of the tetra neutron in the p(p,alpha) reaction at large momentum transfer 25m
The experimental search for the existence of a tetra neutron state has a long history, and the situation remained unclear until recently, and a possible explanation of our experimental finding is still open. On the theoretical side, large efforts have been undertaken as well recently, with results and predictions scattering over wide range in energy, including the prediction for the non-existence of a bound or resonance state. The experimental challenge is to create an isolated 4-neutron system in the final state, without low-energy final-state interaction with other particles involved in the reaction. We have employed a new experimental approach for the search of a possible tetra neutron, the quasi free 8He(p,p alpha)4n reaction at high beam energy. The experiment selected the knockout of the alpha particle at very large momentum transfer, corresponding to 180° p-alpha scattering in the c.m. frame, separating the charged particles from the neutrons in momentum space.
The experiment has been carried out at the SAMURAI setup located at the RIBF. The scattered charged particles have been detected and momentum analyzed, from which the missing mass spectrum has been reconstructed in a wide energy window accepted by the experiment. In case of the absence of any interaction among the neutrons in the final state, a wide distribution centered around 30 MeV relative energy was expected, which reflects the internal relative motion of the neutrons in 8He. It was indeed found, that the largest fraction of the cross section corresponds to this shape. In addition, a well pronounced resonance-like peak at 2 MeV energy with a width of about 2 MeV has been observed with a larger than 5 sigma significance, providing clear evidence for strong four-neutron correlations in the final state. The results have been published recently in Nature [1]. The experiment and results will be presented and discussed.
[1] M. Duer et al., Nature 606 (2022) 678.
Speaker: Thomas Aumann (Technische Universität Darmstadt) -
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Measurement of beta-delayed neutron emission in r-process isotopes with BRIKEN 25m
The Beta-Delayed Neutrons at RIKEN (BRIKEN) collaboration has measured beta-delayed neutron emission probabilities and decay half-lives for some of the most unstable isotopes accessible to experiments. The results provide a wealth of information on the nuclear structure and decay properties of neutron-rich isotopes, and nuclear data critically needed for astrophysics models. The measurements are possible thanks to a high-efficiency neutron detector based on 3He proportional counters and the intense secondary beams available at the Rare Isotope Beam Factory (RIBF) in RIKEN. I will present recent results from BRIKEN experiments, focusing in measurements of mid-shell isotopes in the A=100 region and along the N=82 shell closure. I will discuss their impact in reducing the nuclear physics uncertainty in models of nucleosynthesis during the rapid neutron-capture process.
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Mass Measurements at TRIUMF 25mSpeaker: Anna Kwiatkowski (TRIUMF)
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Structure of $^{155}$Nd and $^{163}$Gd from $^{252}$Cf Spontaneous Fission 15m
A puzzle has arisen recently caused by the apparent shift in maximum deformation from the expected $_{66}$Dy isotopic chain to the $_{60}$Nd isotopic chain in the $82
Speaker: Dr Jonathan Eldridge (Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235) -
18:45
Reflection Asymmetric and Symmetric shape coexistence in 144Ba 15m
Level structures in neutron-rich 144Ba nucleus have been reinvestigated by measuring prompt 3 and 4 fold gamma rays emitted in the spontaneous fission fragments of 252Cf. The previous s = +1 octupole band structure with reflection asymmetric shape has been expanded. A new quadrupole band structure based on 3+ state with reflection symmetric shape has been identified. Decay pattern, angular correlation, internal conversion and systematics provide the evidence for the new band with quadrupole shape. Thus, the results show coexistence of reflection asymmetric and symmetric shapes in 144Ba. This is a first identification of such shape coexistence structure in nuclear structure. Projected shell model calculation has been performed to explain the 3+ quadrupole band structure and found in good agreement with experimental data.
Speaker: enhong wang (vanderbilt university) -
19:00
Isomeric states in 162,164Gd--evidence for the deformed shell gap 15m
Neutron-rich nuclei 162,164Eu were produced by bombarding a proton beam on a 238U target at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory and mass seperating the 162,164Eu products. New level schemes and new gamma ray transitions of the daughters 162,164Gd were identified from beta-decay spectroscopy studies. Halflives of the 162,164Eu were remeasured to clarify the previous ambiguous results. Two quasiparticle band structures were built and compared with neighboring nuclei. The beta and gamma bands were extended in 162Gd and a gamma band was extended in 164Gd. Halflives of the isomeric states at (6-) 1449 keV in 162Gd and (4-) 1096 keV in 164Gd were measured to be 99(3) microseconds and 0.56(3) microseconds, respectively. Projected shell model calculations were performed and found to be in good agreement with all of the experimental data.
Speaker: enhong wang (vanderbilt university) -
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IBM SU(3) symmetry versus BM rotor model 15m
Submission for
Sanibel international conference ICFN7 Nov. 2022IBM SU(3) symmetry versus BM rotor model
J .B. Gupta1 and J. H. Hamilton2
1Ramjas College, University of Delhi, Delhi-110007, India
2 Physics Department, Vanderbilt University, Nashville, TN 37235, U.S.AThe SU(3) symmetry in the interacting boson model sd IBM represent one of the three dynamical symmetry groups of the U(6) group G. It corresponds to the BM rotor model, but is not identical to it. We point out the common and contrasting features of the SU(3) symmetry from the rotor model. The K-independence of the Casimir operator of SU(3) symmetry leads to the degeneracy of the excited bands. The inadequacy of the SU(3) symmetry in representing the experimental band structure and the need of adding the PAIR term is discussed here. That also corrects the interband E2 transitions prohibited in the SU(3) representation. We show that the b softness of the nucleus affects the position of the b-band. This feature is missing from the exact SU(3) symmetry.
Speaker: J .B. Gupta ( Ramjas College, University of Delhi ) -
19:30
Binary fragmentation studies of super-heavy element $^{280}$Cn (Z=112) using $^{48}$Ti +$^{232}$Th reaction at 280 MeV energy 15m
The study of fission dynamics in the actinide region has gained a lot of importance because it can be helpful in providing crucial information about the challenges en route during the formation of superheavy nuclei. Although the intricate process involved in the collective re-arrangement of nuclear fission dynamics is still a unconfirmed topic. In the recent years synthesis of SHE is being done both by using cold (where one of the reaction partners is spherical $^{208}$Pb or $^{209}$Bi) and hot (using $^{48}$Ca induced actinide target) fusion reactions [1]. Due to low rate of production, experiments on the synthesis of new elements need to last many months. Therefore one of the major challenge is to explore various initial conditions that will favour the production of SHE. Such a search could be tracked experimentally by detecting ERs, but it might be time-consuming and not always feasible. An alternative approach is to study those processes in detail that act against the CN formation, like fusion-fission (FF) and quasi-fission (QF), and gain insight on their properties and occurrence. The present experiment is an attempt to study fission dynamics of a superheavy system $^{280}$Cn (Z=112) using a deformed target $^{232}$Th. The main aim of this study is to evaluate the reaction of $^{48}$Ti + $^{232}$Th as a possible candidate for the synthesis of element with Z=112. Anomalies in the various experimental results such as broad mass distribution, large angular anisotropy, correlation between the mass and emission angle of the fission fragments have contributed to the onset of QF [2]. Hence it is challenging to disentangle both the processes of FF and QF and these studies encourage additional research to explore the various aspects of the reaction dynamics of SHE. With this motivation an experiment was performed using the 15UD Pelletron + LINAC accelerator facility of Inter University Accelerator Centre (IUAC), New Delhi where pulsed beam of $^{48}$Ti with beam intensity 0.2 pnA and 250 ns repetition rate was bombarded onto a 250 μg/cm$^{2}$ of $^{232}$Th target (having 80 μg/cm$^{2}$ flourine backing). The target was mounted on the target ladder with fluorine backing facing the beam at the center of scattering chamber of the National Array of Neutron Detector (NAND) facility and measurements were carried out at laboratory energy of 280 MeV. Two multiwire proportional counters (MWPCs) with active area of (10×20cm$^{2}$) were used for the detection of fission fragments and they were placed at fission fragment folding angle of ± 66°. The fission detectors were mounted on movable arms on each side of the beam axis at a distance of 25 cm from the center of the target inside the chamber. This symmetric positioning of the MWPCs allowed the registration of elastically scattered, symmetric and asymmetric fragments from the compound system. For the data analysis the position signals are calibrated using the known positions of the edges of illuminated areas of the MWPC and then calibrated positions are being transformed into polar (θ) and azimuthal (Φ) angles. The obtained θ$_{1}$ and θ$_{2}$ spectra from both detectors are added to get the folding angle distribution. Measurement of Φ of the fission fragments provides a check of the co-planarity of the emission which depicts characteristics of binary events (full-momentum transfer events). A detailed analysis of this reaction is in progress. The correlations between the fragment mass and the TKE will be obtained through two-body kinematics and mass-energy, mass-angle distribution of the fragments will be presented in the conference.
References
1.Y.T. Oganessian et al., Phys.Rev. C 70, 064609 (2004)
2. E.M. Kozulin et al., Physical Review C 99,014616 (2019)Speaker: Ms Shruti - (Department of Physics, Panjab University, Chandigarh -160014, India) -
19:45
Spin distribution measurements in the mass region A∼190 15m
Spin distribution measurements are one of the important aspects of heavy-ion induced studies. These measurements hold the information on maximum angular momentum that a nucleus can hold. Evaporation residue gated spin distribution in this mass region also becomes important because they help us to understand the dynamics of heavy-ion induced fusion-fission process. With knowledge gained from this study can be further used to understand more complex and short lived heavy and superheavy elements. In the present case, $^{32}$S +$^{154}$Sm was chosen to study because of the deformation properties ($\beta_2$=0.339) of the target. These measurements were carried out using HYbrid Recoil Mass Analyser (HYRA) in gas mode coupled with TIFR 4$\pi$ spin-spectrometer. $^{32}$S pulsed beam from 15 UD Pelletron + LINAC accelerator facility at IUAC(Inter-University Accelerator Facility), New Delhi with an average current of $\sim$ 0.5 - 1 pnA was bombarded on $^{154}$Sm target of thickness 118$\mu$gm/cm$^2$ with carbon capping and backing of 25$\mu$gm/cm$^2$ and 10$\mu$gm/cm$^2$ respectively.
\begin{figure}[h!]
\centering
\includegraphics[width=12cm]{fig_4.eps}
\caption{ER-gated $\gamma$-multiplicity distributions for $^{32}$S +$^{154}$Sm at
different E$_{lab}$ energies.}
\label{fig_1}
\end{figure}
Raw fold distributions were ER-gated to remove statistical and nonrotating $\gamma$ rays contributions. Realistic simulations of spectrometer were carried out using Geant4 and fold distribution for different multiplicities were generated i.e for a given gamma multiplicity M, distribution in fold k. Fold distribution P(k) probability can be given by:
$P(k) = \sum_{M_{\gamma=0}}^{\infty}R(k,M_{\gamma}) P(M_{\gamma})$
where R(k, M$_\gamma$) is the response function, in other words, it is the probability of firing k detectors out of N detectors for M uncorrelated $\gamma$ rays and P(M$\gamma$) is the probability of multiplicity distribution. Experimental fold data is used to extract multiplicity as well as spin distribution of $^{186}$Pt$^*$. Response function was generated using Geant4 simulations using exact geometry of spin-spectrometer. We have convoluted experimental fold data with R(M$_\gamma$,k) to get the multiplicity distribution as shown in fig 1 (with error bars). Theoretical calculations are in progress and along with calculations, additional results will be presented at the conference.Speaker: Ranjan Sariyal -
20:00
Fusion and multi-nucleon transfer reaction dynamics 15m
The study of heavy-ion collisions around the Coulomb barrier offers an excellent opportunity to explore several spectacular effects which leads to a better understanding of reaction mechanisms as well as the sub-lime effects of nuclear structure. The fusion and Multi-Nucleon Transfer (MNT) reactions have been found to be elemental for the synthesis of exotic nuclei away from the valley of stability. These studies can be extrapolated further to extreme lower energies, where the reaction dynamics can shed some light on the astrophysical significance of the heavy ion reactions in nucleosynthesis [1]. The fusion cross sections at the sub-barrier energies have been found to be significantly enhanced as compared to one - dimensional barrier penetration model (1-D BPM) calculations. The coupling of various internal degrees of freedom with the relative motion viz. static deformation, surface vibrations, and nucleon transfer channels have been employed to explain the experimentally obtained fusion cross sections [2]. The unambiguous influence of MNT on the sub-barrier fusion enhancement is still not properly understood. Therefore, to elucidate the aforementioned aspects of the heavy ion reaction dynamics, fusion and its complementary, quasi-elastic excitation function measurements have been performed for 28Si + 116,120,124Sn systems using Recoil Mass Separator (RMS), Heavy Ion Reaction Analyzer (HIRA) at Inter-University Accelerator Centre (IUAC) New Delhi, India [3]. The fusion cross sections for all three Sn isotopes are significantly enhanced over the predictions of 1-D BPM calculations. The Coupled-channels framework using CCFULL has been employed to explain the underlying reaction mechanism [4]. The significance of MNT channels at sub-barrier energies have been highlighted in the coupled-channel calculations. The fusion and quasi-elastic barrier distribution have also been extracted from the experimental data to reveal the identity of various channels coupled in the reaction. Detailed analysis and results will be presented during the conference.
- C L Jiang et al., Phys. Rev. Lett. 89, 052701 (2002).
- B. B. Back, H. Esbensen, C. L. Jiang, and K. E. Rehm, Rev. Mod. Phys. 86, 317
(2014). - A. Sinha, N. Madhavan, J. Das, P. Sugathan, D. Kataria, A. Patro, and G. Mehta,
Nucl. Instrum. Methods Phys. Res., Sect. A 339, 543 (1994). - K. Hagino, N. Rowley, and A. Kruppa, Comput. Phys. Commun. 123, 143 (1999).
Speaker: Ms Anjali Rani (Department of Physics & Astrophysics, University of Delhi, New Delhi-110007, India) -
20:15
$\beta$ and $\beta$-n Decay of $^{125}$Ag and $^{127}$Ag 15m
The $\beta$-decay of $^{125m,125,127}$Ag into levels in Cd was investigated at the Holifield Radioactive Ion Beam Facility (HRIBF) at ORNL. Uranium-238 targets were bombarded with 50-MeV protons with an intensity of 15 $\mu$A, and the induced fission products were mass separated ($\delta$M/M = 10,000) and deposited on a moving tape in the center of the VANDLE array consisting of $\gamma$-detectors and plastic scintillators.
A partial decay scheme has been assigned for both $\beta$-decay of the (9/2+) ground state of $^{125}$Ag (consisting of 72 $\gamma$'s from 47 levels) and its low-lying (1/2-) isomer (consisting of 16 $\gamma$'s from 14 levels). The energy of the low-lying (11/2-) isomeric state in #^{125}$Cd is assigned as 188.5(2) keV. In both the isomer and ground state, evidence for -delayed neutron emission was observed, with the resulting branching ratios of 4.6(12)% for the isomer, and 1.2(2)% for the ground state [1]. New information on the $\beta$-decay of $^{127}$Ag into levels in $^{127}$Cd was also observed and a partial decay scheme has been proposed. There is evidence for $\beta$-delayed neutron emission via observation of the decay of $^{126}$Cd. The branching ratios for $\beta$-n from $^{127}$Ag will be discussed and new level scheme will be presented.
*This work has been supported by the U. S. Department of Energy, Office of Nuclear Physics DE-AC02-05CH11231, DOE-AC05-00OR22725, DE-FG05-88ER40407, DE-FG02-96ER40983, DE-FG02-96ER41006, DE-SC00144448
[1]. J. C. Batchelder, et al., Phys. Rev. C. 104, 024308 (2021).Speaker: Dr Jon Batchelder (University of California) -
20:15
Average neutron multiplicity measurements for $^{32}$S+ $^{194,198}$ Pt → $^{226,230}$ Pu* systems with lab energy ranging from 173 MeV-203 MeV 15m
The intricate process involved in the collective re-arrangement of nuclear fission dynamics is still an unconfirmed topic. A few systematic studies are present in the literature related to neutron multiplicities where the experimental data covers wide range of mass and energy. Pre-scission neutrons are extensively studied to understand fusion-fission dynamics involved in the population of heavy and super-heavy nuclei. The main advantage of using this probe is the absence of coulomb barrier and also it serves as a clock for the measurement of time-scale of the reaction. With the advent of heavy-ion accelerators and heavy-ion beams it has become possible to look for a diversity of possibilities of entrance channel parameters such as excitation energy, angular momentum and target-projectile mass asymmetry of the reaction channel. Present study is based on the average neutron multiplicity measurements for $^{226,230}$Pu (Z=94) compound nuclei populated by $^{32}$ S+ $^{194,198}$ Pt reactions. The experiment was carried out using 15UD Pelletron + LINAC accelerator of IUAC, New Delhi where pulsed beam of $^{32}$S in the lab energy range of 173-203 MeV was bombarded on $^{194,198}$ Pt targets resulting in the formation of the compound nuclei $^{226,230}$Pu. Pt targets (rolled foils of $^{194}$Pt and $^{198}$Pt having thickness of 1.7 mg/cm$^{2}$ and 2.1 mg/cm$^{2}$ resp.) were mounted on the target ladder and kept at the center of the scattering chamber vertically to the beam axis. The fission fragments were measured in coincidence using a pair of position-sensitive multiwire proportional counter of active area (20×10) cm$^{2}$. The forward MWPC (along the beam axis) was kept on movable arm inside the chamber at a distance of 25 cm and the backward MWPC was placed at a distance of 21 cm. Both forward and backward angle detectors were centered at 40° and 104° resp. and were operated at 4 mbar pressure of isobutane gas during the whole experiment. A silicon surface barrier detector kept at 12.5° w.r.t. beam direction inside the chamber was used for the normalization of beam flux.
In the past few years similar kind of measurements were carried but with the lighter systems of $^{16,18}$O + $^{194,198}$Pt→$^{210,212,214,216}$Rn [1], $^{19}$F + $^{194,196,198}$Pt→$^{213,215,217}$Fr [2] and $^{12}$C + $^{194}$Pt →$^{206}$Po [3] and they studied effect of N/Z, shell closure on nuclear dissipation and shell correction energies at saddle point using pre-scission neutron multiplicity. These experiments were focused on the study of dynamics of fusion-fission only as these are lighter systems. Presently performed experiment of $^{32}$ S+ $^{194,198}$ Pt → $^{226,230}$Pu* is a representative case of investigation of average neutron multiplicity at different lab energies of 173 MeV, 178 MeV, 183MeV, 193 MeV and 203 MeV. The motivation behind this work is to get deep insight of the dynamics of not only fusion-fission processes but also on the non-compound nuclear processes like quasi-fission. Also it will involve the study of entrance channel effects, shell closure effects and determination of the timescale of quasi-fission and fusion-fission component. This further will help in the optimal selection of target-projectile combinations and bombarding energies to maximize the formation probability of heavy and super-heavy nuclei as ER. For the data acquisition VME based controller ROSE and NiasMARS software were used. The data analysis is being done using ROOT software package. For the extraction of neutron energy pulse shape discrimination based on zero-cross over technique and TOF method were used for the discrimination of neutrons and gamma rays. TOF spectra were calibrated using a precise time calibrator and prompt gamma peak as a time reference and then it was gated with neutrons and fission events. The calibrated and gated neutron timing was then converted into neutron energy. Position calibration was performed in the next step and these calibrated positions were then converted into polar (ө) and azimuthal (Φ) angles in order to obtain folding angle distribution. The theta and phi so obtained are plotted against each other in order to distinguish the non-compound nucleus processes from the full momentum transfer FMT events coming from binary fragments.References:
1. R.Sandal et al., PRC 87,014604 (2013)
2. Varinderjit et al., PRC 87,064601 (2013)
3. Golda at al., NPA 913 (2013) 157-169Speaker: Ms Shruti - (Department of Physics, Panjab University, Chandigarh -160014, India) -
20:15
Bound State of Cu Isotopes in Spin and Pseudospin Symmetry 15m
N. Malekinezhad, M. R. Shojaei
aDepartment of Physics, Shahrood University of Technology, P.O. Box 3619995161-316, Shahrood, Iran.
E-mail: malekinezhadnasrin@gmail.com
shojaei_11151@yahoo.comThe non-relativistic motion of the nucleus in the Schrodinger equation and the relativistic motion in the Dirac and Klein-Gordon equations have long been known to be essential tools for studying atoms, nuclei, and molecules and their spectral behaviors. In recent studies, there has been more interest in the Dirac equation. The Dirac equation is introduced as a relativistic equation to describe the motion of spin-1/2 particles, which plays a key role for relativistic particles in nuclear physics, atomic and molecular physics, quantum chemistry, condensed matter, high energy physics, and particle physics. So, in nuclear physics, the motion of nucleons in nuclei is propagated like relativistic fermionic quasi-particles, then one is considered with spin and pseudospin symmetry for aligned spin and unaligned spin. In this study, we investigated the Dirac equation with the proposed potential using the Parametric Nikiforov-Uvarov method, which is based on solving the polynomial of hypergeometrics. We have calculated the wave function and energy for Cu isotopes. Our results of spin and pseudospin symmetry have been compared with experimental results.
Speaker: nasrin malekinezhad (shahrood university of technology) -
20:15
Connecting Stellar Observations to Properties of Heavy Nuclei 15m
Connecting Stellar Observations to Properties of Heavy Nuclei
Erika M. Holmbeck1,2,3
1Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101, USA
2Joint Institute for Nuclear Astrophysics -- Center for the Evolution of the Elements (JINA-CEE), 640 S Shaw Ln., East Lansing, MI 48824, USA
3Hubble FellowNucleosynthesis by rapid neutron capture (the r-process) accounts for the abundance of about half the trans-iron elements found in the Solar System. While the Solar abundance pattern provides impeccable detail for nucleosynthesis simulations to compare to, the multi-origin nature of the elements in the Solar System muddles site-specific details about the r-process, and therefore properties of nuclei derived from comparisons with the Solar System abundances. On the other hand, signatures of r-process production can be the dominant source of the heavy elements in metal-poor stars. These stars offer a clearer signature of r-process production with increasing confidence that the heavy elements in one star are wholly or mostly attributed to one astrophysical r-process site. This talk will discuss how properties of heavy nuclei (especially fissioning nuclei) can imprint their signatures onto stars, and how we can use those stars to in turn study heavy elements outside of the lab. From these stars, we can learn about properties ranging from the fission fragment distribution of heavy nuclei to the fundamental nuclear equation of state.
Support for this work was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51481.001 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555.
Speaker: Erika Holmbeck (Carnegie Institution for Science & JINA-CEE) -
20:15
Correlation Experiments in Photofission 15m
Photon-induced nuclear fission provides unique information about the nuclear fission process due to their selectivity on excitations of low multipolarity. In particular, fission induced by quasi-monochromatic polarized photons allows determining transition states and channels through which fission proceeds, learning about the nuclear energy landscape around the multi-humped fission barrier. To this end, mass, total kinetic energy and polar as well as azimuthal angular distributions of the fission fragments were measured simultaneously using a position-sensitive twin Frisch-grid ionization chamber [1]. We present results of a pioneering 238U(𝛾,f) experiment at the High-Intensity 𝛾-Ray Source (HI𝛾S) at Triangle Universities Nuclear Laboratory (TUNL) at an excitation energy of 11.2 MeV [2] as well as first data from a follow-up 234U(𝛾,f) experiment investigating excitation energies near the fission barrier.
Supported by HMWK (LOEWE Cluster Nuclear Photonics)
[1] A. Göök et al., Nucl. Instrum. Methods A 830, 366 (2016);
M.Peck et al., EPJ Web of Conferences 239, 05011 (2020)
[2] M. Peck, Dissertation, TU Darmstadt (2020).Speaker: Vincent Wende (Institut für Kernphysik, Fachbereich Physik, Technische Universität Darmstadt, 64289 Darmstadt, Germany) -
20:15
Decay Studies of Neutron Rich Isotopes at FRIB 15m
With the opening of the Facility for Rare Isotope Beams (FRIB) earlier this year, experiments have begun to study exotic neutron rich nuclei with the FRIB Decay Station Initiator (FDSi) [1], with first results obtained in the N=28 island of inversion [2]. The FDSi consists of two focal planes, one for discrete spectroscopy measurements using a hemisphere of gamma ray detectors and a second side for neutron detection with time-of-flight detectors. The second focal plane performs total absorption measurements with the Modular Total Absorption Spectrometer (MTAS) [3]. Due to the large number of detectors, multiple data acquisition systems are used and combined to consistently measure the events and provide the ability to measure neutron-gamma competition. Commissioning experiments have taken place to demonstrate the ability of the decay station to measure exotic nuclei in both focal planes within the same experiment, while minimizing the amount of time used for switching between the focal planes.
Experiments with highly energetic radioactive beam require a dedicated implantation detector in both focal planes to stop the beam and then measure the subsequent decays. In the discrete focal plane, a fast scintillator is coupled to a multi-anode photomultiplier tube for high resolution timing measurements with the neutron detector array [4]. A new implant detector was constructed for use inside MTAS, which used an inorganic scintillator coupled to a silicon photomultiplier array. This allowed for millimeter position resolution when measuring the implantation events and the decay events. This good position resolution greatly reduces background when correlating between implants and decays. I will present the operational principles, design of the detector illustrated with the results obtained during first FDSi experiments.
This work was supported by NNSA DOE DE-NA0003899 and DOE DE-FG02-96ER40983.
1. https://fds.ornl.gov/initiator/
2. H.Crawford et al. submitted to PRL
3. M. Karny et al., NIM A 836, 83-90 (2016).
4. R. Yokoyama et al., NIM A 937, 93-97 (2019).Speaker: Ian Cox (University of Tennessee, Knoxville) -
20:15
Dynamical pair production at sub-barrier energies 15m
Dynamical pair production at sub-barrier energies
Thomas Settlemyre1, Aldo Bonasera2, and Hua Zheng3
1Cyclotron Institute, Texas A&M University, College Station, Texas 77843, USA
2Laboratori Nazionali del Sud, INFN, via Santa Sofia, 62, 95123 Catania, Italy
3School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710119, ChinaIn the collision of two heavy ions the strong repulsion coming from the Coulomb field is enough to produce e+e- pair(s) from vacuum fluctuations [1]. The energy is provided by the kinetic energy of the ions and the Coulomb interaction at the production point. If, for instance the electron is located at the center of mass (C.M.) of the two ions moving along the z-axis, and the positron at a distance x from the electron, the ions can be accelerated towards each other since the Coulomb barrier is lowered by the presence of the electron. This screening may result in an increase of the fusion probability of light ions above the adiabatic limit. We also consider this mechanism in the case of fission.
This research was funded in part by the United States Department of Energy under Grant # DE-FG03-93ER40773 and the NNSA Grant No. DENA0003841 (CENTAUR) and by the National Natural Science Foundation of China (Grant Nos. 11905120 and 11947416).
- A. Bonasera, T. Settlemyre, and H. Zheng, arXiv:2207.06900 [nucl-th]
Speaker: Thomas Settlemyre (TAMU) -
20:15
FINE STRUCTURE OF β-DECAY STRENGTH FUNCTION 15m
The $\beta$-decay strength function $S_{\beta}(E)$ governs [1,2] the nuclear energy distribution of elementary charge-exchange excitations and their combinations like proton particle $({\pi}p)$-neutron hole $({\nu}h)$ coupled into a spin-parity $I^{\pi}$: $[{\pi}p \otimes {\nu}h]I^{\pi}$ and neutron particle $({\nu}p)$-proton hole $({\pi}h)$ coupled into a spin-parity $I^{\pi}: [{\nu}p \otimes {\pi}h]I^{\pi}$. The strength function of Fermi-type $\beta$-transitions takes into account excitations $[{\pi}p \otimes {\nu}h]0^{+}$ or $[{\nu}p \otimes {\pi}h]0^{+}$. Since isospin is a quite good quantum number, the strength of the Fermi-type transitions is concentrated in the region of the isobar-analogue resonance ($IAR$). The strength function for $\beta$-transitions of the Gamow–Teller ($GT$) type describes excitations $[{\pi}p \otimes {\nu}h]1^{+}$ or $[{\nu}p \otimes {\pi}h]1^{+}$. At excitation energies $ E $ smaller than $Q_{\beta}$ (total $\beta$-decay energy), $S_{\beta}(E)$ determines the characters of the $\beta$-decay. For higher excitation energies that cannot be reached with the $\beta$-decay, $S_{\beta}(E)$ determines the charge exchange nuclear reaction cross sections, which depend on the nuclear matrix elements of the $\beta$-decay type.
Successful applications of the total absorption $\gamma$-spectroscopy ($TAGS$) for $S_{\beta}(E)$ resonance structure study, methods of $TAGS$ spectra interpretation, and results of analysis of $S_{\beta}(E)$ structure for the $GT$ $\beta^{+}/EC$ and $GT$ $\beta^{-}$-decays were summarized in [1]. Development of experimental technique allows application of methods of nuclear spectroscopy with high energy resolution for $S_{\beta}(E)$ fine structure measurement [2-4]. First results of the $S_{\beta}(E)$ fine structure study were summarized in [2]. The combination of the $TAGS$ with high resolution $\gamma$-spectroscopy may be applied for detailed decay schemes construction [2]. It was shown [2-4] that the high-resolution nuclear spectroscopy methods give conclusive evidence of the resonance structure of $S_{\beta}(E)$ for $GT$ and first-forbidden ($FF$) $\beta$-transitions in spherical, deformed, and transition nuclei. High-resolution nuclear spectroscopy methods [2-5] made it possible to demonstrate experimentally the reveal splitting of the peak in the $S_{\beta}(E)$ for the $GT$ $\beta^{+}/EC$-decay of the deformed nuclei into two components.
Resonance structure of the $S_{\beta}(E)$ for $\beta$-decay of halo nuclei was analyzed in [6-8]. It was shown that when the parent nucleus has $nn$ Borromean halo structure, then after $GT$ $\beta^{-}$ -decay of parent state or after $M1$ $\gamma$-decay of $IAR$ the states with $np$ tango halo structure or mixed $np$ tango + $nn$ Borromean halo structure can be populated.
Our estimation [7] demonstrated that the value $Z/N \approx 0.6$ corresponds to the Wigner’s spin-isospin $SU(4)$ symmetry region.
In this report the fine structure of $S_{\beta}(E)$ is analysed. Resonance structure of $S_{\beta}(E)$ for $GT$ and $FF$ $\beta$-decays, structure of $S_{\beta}(E)$ for halo nuclei, quenching [8] of the weak axial-vector constant ${{g_{A}}^{eff}}$, splitting of the peaks in $S_{\beta}(E)$ for deformed nuclei connected with the anisotropy of oscillations of proton holes against neutrons (peaks in $S_{\beta}(E)$ of $GT$ $ \beta^{+}/EC $-decay) or of protons against neutron holes (peaks in $S_{\beta}(E)$ of $GT$ $\beta^{-}$-decay), and different manifestations of the $SU(4)$ symmetry are discussed.- Yu.V. Naumov, A.A. Bykov, I.N. Izosimov, Sov. J. Part. Nucl., $\textbf{14}$, 175(1983).
- I.N. Izosimov, et al, Phys. Part. Nucl., $\textbf{42}$, 1804(2011). DOI: 10.1134/S1063779611060049
- I.N. Izosimov, et al, Phys. At. Nucl., $\textbf{75}$, 1324(2012). DOI: 10.1134/S1063778812110099
- I.N. Izosimov, et al, Phys. Part. Nucl. Lett., $\textbf{15}$, 298(2018). DOI: 10.1134/S1547477118030081
- I.N. Izosimov, et al, JPS Conf. Proc., $\textbf{23}$, 013004 (2018). DOI: 10.7566/JPSCP.23.013004
- I.N. Izosimov, JPS Conf. Proc., $\textbf{23}$, 013005 (2018). DOI: 10.7566/JPSCP.23.013005
- I.N. Izosimov, Phys. Part. Nucl. Lett., $\textbf{15}$, 621(2018). DOI: 10.1134/S1547477118060092
- I.N. Izosimov, Phys. Part. Nucl. Lett., $\textbf{16}$, 754(2019). DOI: 10.1134/S1547477119060207
Speaker: Dr Igor Izosimov (Joint Institute for Nuclear Research) -
20:15
Fission Dynamics of nuclei near the Pb shell closure region 15m
Fission dynamics of compound nuclei, primarily a collective phenomena, is elucidated through two intertwined aspects, the macroscopic (liquid drop) and the microscopic (shell) effects. Unanticipated observations of mass-asymmetric fission in 180Hg [1] and multimodal fission in 194,196Po, 202Rn [2] have led to the prediction of a new island of mass-asymmetric fission around the Pb region [3]. In present work, the fission dynamics of 203,205Bi nuclei populated via 19F + 184,186W reactions has been implored through mass distribution and neutron multiplicity measurements. The experiment has been performed using the 15UD Pelletron+LINAC accelerator facility at Inter University Accelerator Centre (IUAC), New Delhi. The fragment mass distribution of excited 203,205Bi nuclei (80-110 MeV) have been extracted through two large area (20*10 cm2) Multi-Wire Proportional Counters (MWPCs) kept at folding angles. Eighty organic liquid scintillators placed in the NAND detector array [4] at IUAC have been used to measure both pre- as well as post-scission components of neutron multiplicity. The underestimation of experimental pre-scission neutron multiplicities compared to Bohr-Wheeler fission width [5] indicates towards the dissipative nature of fission. Signatures of asymmetric fission have been observed from mass distribution of both 203,205Bi at lowest excitation energy of 80 MeV (~55 MeV above the saddle point) only, the fission-mode being symmetric at higher excitation energies. The agreement between experimental fragment mass width (σm) with saddle point model [6] at all excitation energies recedes the contribution of quasi-fission for the observed asymmetry. Further, the experimental mass asymmetry ratio agrees with the predictions of the semi-empirical model GEF [7]. 2-D Langevin model calculations have been initiated to understand the role of shape dependent dissipation strength and shell effects in the observed mass asymmetry.
- A.N. Andreyev et al., Phys. Rev. Lett. 105, 252502 (2010).
- L. Ghys et al., Phys. Rev. C 90, 041301 (2014).
- P. Möller and J. Randrup, Phys. Rev. C 91, 044316 (2015).
- N. Saneesh et al., Nucl. Ins. and Meth. in Phys. Res. A 986, 164754 (2021).
- N Bohr and J A Wheeler, Phys. Rev. 56, 426 (1939).
- B. B. Back et al., Phys. Rev. C 53, 4 (1996).
- K. H. Schmidt et al., Nucl. Data Sheets 131, 107 (2016)
Speaker: Ms K. Chakraborty (Department of Physics & Astrophysics, University of Delhi, New Delhi-110007, India) -
20:15
Low-spin structures in the 206Tl and 205Pb nuclei investigated in thermal neutron capture reactions 15m
Nuclei from the regions of doubly-closed shells are considered an excellent ground for studying both a) the couplings between valence nucleons - this provides information on the effective nucleon-nucleon interaction and, b) couplings of the valence nucleons with core excitations, what may be used as a unique test of various effective interactions.
$^{206}$Tl, having one-proton-hole and one-neutron-hole with respect to the $^{208}$Pb core, was populated in a thermal neutron capture reaction $^{205}$Tl(n,gamma)$^{206}$Tl at Institut Laue-Langevin in Grenoble (France). The gamma decay from the capture state was studied using the HPGe multidetector FIPPS array consisting of 8 Ge clovers. The results of the gamma-coincidence analysis will be presented: 21 low-spin excited states were observed in $^{206}$Tl, 8 of them were newly established. The analysis of gamma-ray angular correlations provided information about transitions multipolarities, which significantly helped with spin-parity assignments. The level structure of $^{206}$Tl was compared to the results of shell-model calculations. The large number of low-spin states populated in neutron capture reactions on $^{205}$Tl, arising from one proton-hole and one neutron-hole excitations, can be used as a very good testing ground for the old and newly developed shell-model interactions in the south-west quadrant of the nuclear chart with respect to $^{208}$Pb. It will allow to benchmark the two-body matrix elements of the residual interaction in this important region of the nuclear chart.
In turn, the $^{205}$Pb nucleus has three neutron-holes with respect to the $^{208}$Pb core, which makes it even more demanding testing field for the shell-model calculations. In longer perspective the studies of its structure would also stimulate the works on the shell-model description with a term coming from three-body forces in the region of heavier masses nuclei. The decay of the capture state in $^{205}$Pb populated at ILL in $^{204}$Pb(n,gamma)$^{205}$Pb reaction was investigated using FIPPS array coupled to the 7 HPGe clovers from IFIN Bucharest. The preliminary results of double and triple gamma-coincidence analysis will be presented.
Speaker: Natalia Cieplicka-Orynczak (IFJ PAN Krakow) -
20:15
Magnetic rotational band in 61Ni 15m
The Ni nuclei, with magic number $Z=28$, is considered as an interesting platform to study the evolution of shapes of nuclei as a function of neutron number. From the spherical shapes in $^56$Ni(N=28) and $^68$Ni(N=40) to the exhibition of super deformed bands in $^{63}$Ni[1] at high spin, different types of structure have been reported. Having the major shell closure at $Z=28$, the low lying states of $^{61}$Ni are expected to be associated with near spherical shape. With a little excitation energy, one proton can be excited to $1p_{3/2}/1f_{5/2}$ creating a hole at high-$j$ $1f_{7/2}$ orbital and one neutron can be excited to high-$j$ $1g_{9/2}$ orbital. This configuration is ideal to form a shears band with a near spherical core. Recently, the magnetic rotational (MR) band has been reported in $^{60}$Ni[2] and $^{62}$Co[3]. Therefore, neighboring to $^{60}$Ni, MR bands are also expected to be present in $^{61}$Ni.
The reaction $^{50}Ti(^{14}C,3n)^{61}Ni$ populates the high spin states of $^{61}$Ni (thin $^{50}Ti$ enriched foil) at 40 MeV beam energy from the 9 MV Tandem at FSU. The FSU array of 6 BGO shielded clover & 3 single crystal HPGe detectors, placed at 3 different angles; 90$^{o}$, 45$^o$ and 135$^o$, are used to detect the de-excited γ-rays. With γ−γ coincidence analysis, DCO ratio and polarization measurements the level scheme for $^{61}$Ni has been considerably extended with respect to the last work on $^{61}$Ni[4] up to 13 MeV and 35/2ℏ spin with the observation of 78 new transitions and 31 new levels with definite spin-parity. We have observed 2 dipole (M1) bands and 2 quadrupole (E2) bands for the first time in $^{61}$Ni. The low lying negative parity states of the $^{61}$Ni are well reproduced by shell model calculation involving $\nu p_{3/2}$, $\nu f_{5/2}$, $\nu p_{1/2}$ and $\nu g_{9/2}$ orbitals. The positive parity states indicate the occupancy of neutron particle in shape driving $\nu g_{9/2}$ which induce deformation in the system. The higher lying regular E2 structures are interpreted as rotational bands with small deformation. The positive parity dipole (M1) bands are matched beautifully with the semi classical description of shears mechanism and shows consistent interaction strength per particle-hole pair in this mass region.
- M. Albers et. al., Phys. Rev. C 80, 054314 (2013).
- D. A. Torres et. al., Phys. Rev. C 78, 054318 (2008).
- N. Sensharma et. al. Phys. Rev. C 105, 044315 (2022).
- S. Samanta et. al., Phys. Rev. C 99, 014315 (2019).
Speaker: Soumik Bhattacharya (Florida State University) -
20:15
Many-Body Tunneling Models for Nuclear Fission 15m
Many-body tunneling involving strongly interacting particles is still not completely understood. The nuclear fission process is one example of many-body decay that can be represented as a tunneling process within the space of collective variables [1]. Using realistic potential energy surfaces obtained with the Hartree-Fock-Bogoliubov theory, we apply the nudged elastic band approach to collective action minimization in two- and three-dimensional collective spaces to identify exit points that characterize the most probable spontaneous fission modes [2]. While grid-based approaches to spontaneous fission require a priori choice of collective variables and can be computationally expensive, imaginary time mean field theory offers a promising alternative description of nuclear fission without large grid-based calculations of the collective space [3,4,5]. We explore imaginary time mean field theory as a possible alternative to grid-based descriptions of nuclear fission and explore methods for solving the mean field equations in imaginary time.
This work was supported in part by the National Science Foundation under Grant No. PHY-1430152 (JINA Center for the Evolution of the Elements) and the U.S. Department of Energy under Award Number DOE-DE-NA0004074 (NNSA, the Stewardship Science Academic Alliances program).
[1] T. Kindo, A. Iwamoto. "Methods for the calculation of the fission half-life in the multi-dimensional space." Physics Letters B 225, no. 3 (1989): 203-207.
[2] E. Flynn, D. Lay, S. Agbemava, P. Giuliani, K. Godbey, W. Nazarewicz, and J. Sadhukhan. "Nudged elastic band approach to nuclear fission pathways." Physical Review C 105, no. 5 (2022): 054302.
[3] S. Levit., J. W. Negele, and Z. Paltiel. "Barrier penetration and spontaneous fission in the time-dependent mean-field approximation." Physical Review C 22, no. 5 (1980): 1979.
[4] J. Skalski, "Nuclear fission with mean-field instantons." Physical Review C 77, no. 6 (2008): 064610.
[5] S. Levit., "Variational approach to tunneling dynamics. Application to hot superfluid fermi systems. Spontaneous and induced fission." Physics Letters B 813 (2021): 136042.Speaker: Eric Flynn (FRIB/NSCL Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.) -
20:15
Microscopic description of the onset of triaxiality in neutron-rich Ru and Mo isotopes 15m
see attachment
Speaker: Stefan Frauendorf (University Notre Dame) -
20:15
MULTIMODAL FISSION: MICROSCOPIC STUDIES OF SPONTANEOUS FISSION 15m
Fission is a fundamental nuclear decay that plays an important role in many areas of science. Recently, important progress has been made in microscopic modeling of the dynamics of spontaneous and induced fission based on the nuclear density functional theory (DFT) [1].
For this study, we investigate multi-modal fission pathways using nuclear DFT with several energy density functionals (EDF). The multidimensionally constrained calculations of the collective potential and the nonperturbative inertia tensors are performed in the frameworks of the axial reflection-asymmetric Hartree-Fock Bogoliubov theory. We consider two Skyrme (UNEDF1 and SkM*) and one Gogny (D1S) EDFs. The collective least action in two- and three-dimensional collective spaces is determined using the nudged elastic band method [2]. The spontaneous fission of selected Th, Fm, Sg, and Og isotopes is investigated. To distinguish between fission pathways corresponding to different fragment geometries, we computed the collective potential in (Q20, Q30) and (Q20, Q40) multidimensional collective space, see [3]. For several nuclei we found a competition between symmetric compact, symmetric-elongated and asymmetric-elongated fission pathways [4], suggesting a possible impact of multidimensional calculations in the estimation of fission fragments distributions.
This work was supported by the U.S. Department of Energy under Award No. DOE-DE-NA0002847 (NNSA, the Stewardship Science Academic Alliances program), DESC0013365 (Office of Science), and DE-SC0018083 (Office of Science, NUCLEI SciDAC-4 Collaboration)
[1] M. Bender et al., J. Phys. G 47, 113002 (2020).
[2] E. Flynn, D. Lay, S. Agbemava, P. Giuliani, K. Godbey, W. Nazarewicz, and J. Sadhukhan Phys. Rev. C 105, 054302 (2022).
[3] A. Zdeb, M. Warda, L. M. Robledo, Phys. Rev. C 104, 014610 (2021).
[4] A. Staszczak, A. Baran, J. Dobaczewski, and W. Nazarewicz Phys. Rev. C 80, 014309 (2009).Speaker: Sylvester Agbemava (FRIB) -
20:15
New transitions and levels for 163Gd and 163Tb obtained from β decay studies 15m
Neutron rich nuclei in the mass region around A=160 have been and will continue to be of interest for the study of nuclear structure because of the rapid onset of deformation between 88 and 90 neutrons. The observation of detailed changes in nuclear structures within this mass region has provided and will continue to provide insight into the nuclear force. Investigations of γ-rays emitted following $^{163}$Eu β-decay to $^{163}$Gd, and subsequently to $^{163}$Tb, have been performed for evaluation of the nuclear structure of $^{163}$Gd and $^{163}$Tb. Data were collected at the LeRIBSS station of the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory with an array of four Clover HPGe detectors for γ-rays and two plastic scintillators for β detection. The γ-rays were identified as belonging to $^{163}$Gd, and $^{163}$Tb via mass selection and γ-γ-β, γ-γ, or γ-xray coincidence. In total 107 new γ-ray transitions were observed in $^{163}$Gd from 53 newly identified levels, constituting the first identification of the structure of $^{163}$Gd. In total 39 new γ-ray transitions were observed in $^{163}$Tb from 15 newly identified levels and 12 previously identified levels. Previously identified unplaced transitions in $^{163}$Tb have been placed within the known level scheme of $^{163}$Tb and additional states and transitions have been identified. The structure of $^{163}$Gd has been evaluated in comparison to Projected Shell Model, and Potential Energy Surface calculations were carried out for both $^{163}$Gd and $^{163}$Tb.
Speaker: Dr Christopher Zachary (Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235) -
20:15
Probing the open nuclear quantum system description by investigating the decays of stretched resonances* 15m
The structures of stretched excitations are dominated by a single particle-hole component for which the excited particle and the residual hole couple to the maximal possible spin value available on their respective shells. In light nuclei they appear as high-lying resonances resulting from the $p_{3/2} \rightarrow d_{5/2}$ stretched transitions. Due to the expected low density of other one-particle-one-hole configurations of high angular momenta in this energy region, their configurations should be relatively simple. Therefore, their theoretical analysis could provide clean information about the role of continuum couplings in stretched excitations. The direct measurement of stretched states decay paths, which are poorly known thus far, should provide data which can be used as a very demanding test of state-of-the-art theory approaches, like for example, Gamow Shell Model (GSM).
The results of the first experimental studies on the decay of the 21.47-MeV stretched resonance in $^{13}$C will be presented. It was investigated in a $^{13}$C(p,p’) experiment at 135 MeV proton energy, performed at the Cyclotron Centre Bronowice (CCB) at IFJ PAN in Kraków. The detection setup consisted of: i) the KRATTA telescope array for detection of scattered protons, ii) two clusters of the PARIS scintillator array and four LaBr$_3$ detectors for gamma-ray measurement, and iii) a thick DSSD detector for light charged particles detection. The information on the proton and neutron decay branches from the 21.47-MeV state in $^{13}$C was obtained by measuring the protons inelastically scattered on a $^{13}$C target in coincidence with gamma rays from daughter nuclei and charged particles, from the resonance decay. The experimental results were compared with theoretical calculations from the GSM, extended to describe stretched resonances in p-shell nuclei. A very good agreement obtained between the measured and predicted properties of the 21.47-MeV state in $^{13}$C demonstrated the high quality of the GSM calculations.
*This work was supported by the Polish National Science Centre, Poland under research project No. 2020/39/D/ST2/03443
Speaker: Natalia Cieplicka-Orynczak (IFJ PAN Krakow) -
20:15
Search for Time-Reversal Invariance Violation: why heavy nuclei are better? 15m
Searches for electric dipole moments (EDMs) in atomic and molecular systems may provide better sensitivity to Time Reversal Invariance Violating (TRIV) interactions than neutron EDM due to enhancement factors related to complex structure of the system. We consider advantages and disadvantages of many-body nucleon system for the search for TRIV interactions in neutron scattering on heavy nuclei. The absence of final state interactions for the set of specific observables makes these experiments complementary to neutron and atomic electric dipole moment (EDM) measurements. Moreover, in neutron scattering the observables are not a static parameter, as EDM, which leads to an additional enchantment factors for TRIV interactions. Based on these observations we show that neutron scattering experiments at new high flux Spallation Neutron Sources can open new paradigm in the search for TRIV in hadronic interactions and essentially improve the current limits on these TRIV interactions obtained from neutron and atomic EDMs.
Acknowledgment: This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics program under Award No. DE-SC0020687.
Speaker: Prof. Vladimir Gudkov (University of South Carolina) -
20:15
Sequential decay analysis of 235U(nth,f) reaction using quantum mechanical fragmentation approach 15m
The theoretical and experimental observations conclude that the nuclei belonging to heavy and super heavy mass region may dissociate into two or three fragments at ground state as well as excited state. Two or three body decay depends on different nuclear properties such as shape, size, magicity etc. It was observed by Swiatecki et al.[1] that the fissility parameter can play a decisive factor for the emergence of binary or ternary division of the parent nucleus. The shape effects of the nuclei are studied in [2] and the possibility of two or three necks is investigated. The concept of two necks represent the emission of three fragments along the fission axis and process is known as collinear cluster tripartition (CCT). An experimental attempt to study CCT mode was made by Pyatkov et al. [3] using 235U(nth,f) reaction where two of the fragments were detected and third fragment was identified by using the missing mass method. In this experiment, heavy Sn isotopes along with Ni or Ge was detected at the two ends and it was concluded that CCT may proceed via a sequential binary decay mechanism.
In the present work, quantum mechanical fragmentation theory (QMFT)[4-6] based methodology is applied to study as an the sequential decay mechanism of 235U(nth,f) reaction. The Excitation energy of the fission fragments is calculated using energy dependent level density parameter. The excitation energy dependent fragmentation potential is calculated and most probable decay channel is identified. The barrier characteristics of the identified decay channel are analyzed. The shared excitation energy of the fission fragments is calculated using the level density parameter and secondary decay of the identified heavy fragment is worked out. The comparison of the identified fragments in sequential process is made with the available experimental result.References
1. W.J. Swiatecki, Proceedings of the Second UN Conference on the Peaceful Uses of Atomic Energy, Geneva, 1958, 15 (United Nations, Geneva, 1958).
2. V.M. Strutinsky et al., Nucl. Phys. 46, 639 (1963).
3. Yu.V. Pyatkov et al., Eur. Phys. J. A 45, 29 (2010).
4. R. K. Gupta, W. Scheid, and W. Greiner, Phys. Rev. Lett. 35, 353 (1975).
5. A Kaur, N Sharma and M. K. Sharma, Phys. Rev. C,103 034618 (2021).
6. N. Sharma, A. Kaur and M. K. Sharma, Phys. Rev. C,102 064603 (2020).Speaker: Mr Nitin Sharma (School of Physics and Materials Science, Thapar Institute of Engineering and Technology, Patiala, 147004, Punjab, India ) -
20:15
The puzzle of Sr-Zr, Mo and Ru n-capture elements in stars 15m
Observations of anomalously large abundances of stable Sr, Y, Zr, Mo, and Ru in some ultra-metal-poor (UMP) stars [1] as well as in the Galactic disk [2,3], as compared to heavier neutron-capture elements in the Solar System, have brought about new questions regarding the nucleosynthesis processes behind the production of those nuclei.
Comparison of observations with Galactic evolution models shows that Canonical stellar sources of heavy elements, such as the s-process in massive stars and AGB stars or the r-process, do not appear to produce a sufficient amount of these elements.
One of the problems for studying the nucleosynthesis of these elements is the lack of experimental information on most of the nuclei involved. Also, the role of the fission recycling of heavy and super heavy elements not studied yet will contribute to the abundance of these elements.
I will present a review of high-resolution stellar spectra information available as well as the Galactic Chemical Evolution models used to describe the observations. Also, I’ll review available nuclear data and theoretical prescriptions for nuclear masses, half-lives, Pn, etc, highlighting the necessity of the refinement of the nuclear data in order to solve the puzzle of the production of light n-capture elements.
Finally, I’ll present the experimental results obtained on the mass region A=88-90 by means of βγ and βγγ spectroscopy using the reaction 235U(n,f) at ILL [4] which contributes to the synthesis of the neutron-rich Sr, Y, and Zr.
References
[1] J. J. Cowan, I. U. Roederer, C. Sneden, and J.E. Lawler. r-Process Abundance Signatures in Metal-Poor Halo Stars. Carnegie Observatories Astrophysics Series, Vol.5: RR Lyrae Stars, Metal-Poor Stars, and the Galaxy ed. A. McWilliam (Pasadena: Carnegie Observatories) (2011).
[2] T Mishenin, M Pignatari, T Gorbaneva, C Travaglio, B Côté, F-K Thielemann, C Soubiran. Enrichment of the Galactic disc with neutron capture elements: Sr, Monthly Notices of the Royal Astronomical Society, Volume 484, Issue 3, April 2019, Pages 3846–3864, https://doi.org/10.1093/mnras/stz178
[3] T Mishenina, M Pignatari, T Gorbaneva, C Travaglio, B Côté, F-K Thielemann, C Soubiran, Enrichment of the Galactic disc with neutron-capture elements: Mo and Ru, Monthly Notices of the Royal Astronomical Society, Volume 489, Issue 2, October 2019, Pages 1697–1708, https://doi.org/10.1093/mnras/stz2202
[4] Experiment 3-01-642 ILL. DOI: 10.5291/ILL-DATA.3-01-642Speaker: Dr Teresa Kurtukian-Nieto (Univ. Bordeaux, CNRS, LP2I Bordeaux, UMR 5797, F-33170 Gradignan, France) -
20:15
Thermally enhanced alpha and cluster decay rates 15m
Thermally enhanced alpha and cluster decay rates
D. F. Rojas-Gamboa1, N. G. Kelkar1, and O. L. Caballero2
1Departamento de Física, Universidad de los Andes, Carrera 1 No. 18 A - 10, Bogotá, 111711, Colombia
2Department of Physics, University of Guelph, Guelph, ON N1G 2W1, CanadaIn a reaction network for the evolution of nuclear abundances, the thermal excitations of nuclei are usually taken into account in the production reactions and their reverse reaction rates. However, the alpha decay rates are taken to be those corresponding to the terrestrial decays of ground state nuclei and the cluster decays are neglected. We formulate a universal decay law (UDL) for the half-lives in these decays in terms of the basic information of the parent nucleus, the daughter nucleus, and the emitted particle [1], to investigate the alpha and cluster decay of excited heavy nuclei. The cluster decay half-lives are found to decrease when the difference between the excitation energies of the parent and daughter nuclei, ∆E^>0, increases, with the reduction being a few orders of magnitude for higher values of ∆E^ [2]. This can be of importance for nucleosynthesis calculations of heavy elements formed in extremely hot environments, as well as in highly energetic heavy-ion collisions. The UDL for excited nuclei is used to provide an estimate of the enhancement in the cluster decay rates of thermally excited nuclei such as those produced in r-process nucleosynthesis. The alpha and cluster formation probabilities are also investigated based on the UDL.
D.F.R-G. thanks the Faculty of Science, Universidad de Los Andes, Colombia, for financial support through Grant No. INV-2021-126-2314.
- Qi, C. et al., Phys. Rev. Lett. 103, 072501 (2009).
- Rojas-Gamboa, D., Kelkar, N. G. and Caballero, O. Nuc. Phys. A. 1028, 122524 (2022).
- Sandulescu, A. et al., Sov. J. Part. Nucl. 11:6, (1980).
- Rose, H. J. and Jones, G. A., Nature 307, 245-247 (1984).
- Ward, R. A. and Fowler, W. A., Astrophys. J. 238, 266-286 (1980).
Speaker: Diego Ferney Rojas Gamboa (Departamento de Física, Universidad de los Andes,) -
20:15
Towards the establishment of an electrofission experiment at the S-DALINAC 15m
To account for the observed abundances of heavy elements, the rapid-neutron capture process is essential [1]. It was first proposed more than six decades ago, but is still not completely understood. The r-process is thought to occur in very neutron rich environments such as neutron star mergers, where the fission yields play an important role in determination of the final abundances, in particular for mass numbers above 100. The fission yields depend on the excitation energy of the compound nucleus, which is not well studied. To increase our understanding of fission processes in the actinide region, a new setup to perform electron-induced fission is in development at the S-DALINAC electron accelerator at the Technische Universität Darmstadt. Scattered electrons will be detected with the large acceptance quadrupole-clam-shell spectrometer providing a precise measurement of the excitation energy of the nucleus. Combining this established setup with fission fragment detectors allows for a coincident measurement of fission fragments with a good mass resolution as a function of the excitation energy. The coincident detection will be realized using a start detector which provides the timing information of the scattered electron and a set of fission fragment detector modules (FFDM) placed around the actinide target. Each FFDM consists of a thin electron-emitting foil coupled to an electrostatic mirror and a micro channel plate detector for generation of the stop signal and a silicon strip detector which will act as a calorimeter providing a measurement of the kinetic energy of the fission fragment. The masses of the fission fragments will then be determined case-by-case from their individual times-of-flight and their kinetic energies. In this talk, the design of the setup and initial tests of key components will be presented.
- J. J. Cowan et al., Rev. Mod. Phys. 93, 015002 (2021)
Speaker: Mr Gerhart Steinhilber (Technische Universität Darmstadt) -
20:15
Uncertainty Quantification of Optical Models in Fission Fragment De-excitation 15m
Kyle Beyer (1), Cole D. Pruitt (2), and Brian Kiedrowski (1)
(1) University of Michigan, Department of Nuclear Engineering and Radiological Sciences,
2355 Bonisteel Blvd, 1906 Cooley Bldg, Ann Arbor, Michigan 48109-2104(2) Lawrence Livermore National Laboratory
7000 East Ave, Livermore, CA 94550Fission event generators are used to study event-by-event correlations of emitted radiation in fission. These signals are important both in nuclear nonproliferation and safeguards, as well as in probing poorly understood aspects of fission, such as fission fragment excitation energy and angular momentum sharing. In Monte-Carlo Hauser Feshbach fission fragment de-excitation, phenomenological optical models are used in simulating neutron emission from the fragments. Because such models are trained on experimental scattering data on β-stable targets, using them for fission fragment de-excitation requires extrapolation to neutron-rich regions, where their reliability is unknown.
There is evidence presented in a forthcoming publication [1] that two workhorse optical models, Chapel-Hill 89 (CH89) and Koning-Delaroche (KD), more accurately reproduce their training data when fit using Markov-Chain Monte Carlo (MCMC) and robust outlier rejection, rather than with the original chi-squared methodologies. The additional advantage of MCMC is that it provides posterior distributions for the parameters conditional on the experimental training data. In this work, we propagate these new parameter distributions through CGMF, a Monte-Carlo Hauser-Feshbach fission event generator, to determine the new CGMF predictions, with uncertainties, of fission observables, for spontaneous fission of 252Cf and thermal neutron induced fission of 235U [2]. We construct resulting uncertainty distributions for observables including neutron and gamma multiplicity distributions and energy spectra.
A current objective of ab-initio nuclear theory is the construction of global microscopic optical potentials that don’t rely on a limited isotopic region of measured cross sections, and can accurately describe neutron-rich isotopes [3]. Recently, one such model, the WLH model, has been derived from chiral effective field theory [4]. We add this model to CGMF, and propagate its theoretical uncertainties through to the fission observables, comparing its performance to the phenomenological models.
This work was funded by the Consortium for Monitoring, Technology, and
Verification under Department of Energy National Nuclear Security Administration
award number DE-NA0003920 and performed under the auspices of the
U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.-
Pruitt, C. D. et al, “Uncertainty-Quantified Phenomenological
Optical Potentials for Single-Nucleon Scattering”, LLNL release
number LLNL-JRNL-835671-DRAFT (to be published). -
Talou, Patrick et al, "Fission fragment decay simulations with the CGMF code", Computer Physics Communications 269, 108087 (2021).
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Johnson, Calvin W. et al, "White paper: from bound states to the continuum", Journal of Physics G: Nuclear and Particle Physics 47, 123001 (2020)
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Whitehead, T. R. et al, "Global Microscopic Description of Nucleon-Nucleus Scattering with Quantified Uncertainties", Physical Review Letters 127, 182502. (2021)
Speaker: Kyle Beyer (University of Michigan) -
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Fission II: Plenary Sundial I and II
Sundial I and II
Sundial Beach Resort
1451 Middle Gulf Drive Sanibel, FL 33957-
08:30
Unraveling The Many Facets of Fission Dynamics: A Real-Time Quantum Approach 25m
Unraveling The Many Facets of Fission Dynamics:
A Real-Time Quantum ApproachAurel Bulgac*, Department of Physics, University of Washington, Seattle, WA 98195
When comparing nuclear fission at the venerable age of almost 84 years old with other quantum many-body systems (superconductivity, superfluidity, quantum Hall effect, fractional quantum Hall effect, magnetism, etc.) it is surprising to find out how little is known and microscopically justified for this complex quantum non-equilibrium process.
In the last decade a significant advance was achieved in modeling and disentangling aspects of fission, by means of a pure quantum approach. The level of agreement with observations, without the resort to any unverified theoretical assumptions, uncontrolled numerical approximations, or phenomenology and incorporating only the basic input needed to reproduce most of the well-known properties of nuclei, is surprisingly good. The theoretical framework requires only eight input parameters at most: the nuclear saturation density and energy, surface tension, the symmetry energy and its density dependence to a lesser degree, proton charge, the spin-orbit and the nuclear pairing interaction strengths. Some of our foremost theoretical findings are: i) the strongly-damped character of the large amplitude collective motion beyond the outer saddle-point, ii) the fission fragment excitation energies and its sharing mechanism, and the somewhat surprising excitation energy exchange mechanism between the fission fragments before the fission fragments are fully accelerated, iii) the intrinsic fission fragment spins and their unexpected correlation character, iv) the nature and the properties of the non-equilibrium neutrons emitted before the fission fragments are fully accelerated, v) the strongly damped character of the fission fragment shape evolution after they are spatially separated, vi) the total kinetic energy of the fission fragments, vii) and the evolution of these properties with the initial excitation energy of the compound nucleus.
Figure 1 Spatial profile of the ``scission" neutron number density distribution (left panel) of the heavy (HFF on the left) and light (LFF on the right) fission fragment and their excitation energies (right panel) before full acceleration. In the left panel the line lines show the neutron number densities of the fission fragments at the level 0.01 fm-3. The colorbar in the left panel is for the neutron velocity in units of speed of light.
*These results were obtained in collaboration with I. Stetcu (LANL), S. Jin (UW), I. Abdurrahman (UW), K.J. Roche (PNNL), K. Godbey (Texas A&M and MSU), P. Magierski (Warsaw UT), N. Schunck (LLNL).Speaker: Prof. Aurel Bulgac (University of Washington) -
08:55
A recent progress of dynamical treatment of nuclear fission 25m
We have been conducting researches in many aspects of nuclear fission. Among them, a dynamical description of nuclear fission in terms of multidimensional Langevin equations has seen a reasonable success in explanation of the systematical and anomalous trends of distributions of fission fragment mass, total kinetic energy (TKE), and deformations. Especially, correlations of these observables have allowed us to elucidate subtle competition among the classical and quantal aspects of nuclei that influence the complicated nuclear fission process. In the present talk, I will explain our resent progress in this direction, namely, application of the methodology to the region of superheavy nuclei, to a series of Uranium nuclei from the proton drip to the neutron drip
line, and energy dependence of the TKE for actinide nuclei. In the superheavy nuclei, a new mode, super-asymmetric mode influenced by the shell of 208Pb, is clearly seen, and positions of the peaks of the mass distributions differ strongly with those deduced by experiment. For Uranium, the mass-TKE-Q20 distributions of fission fragments change in a complicated manner as a function of the mass number of the fissionning nucleus, and we have good interpretation of this change. Finally, we found that the decrease of the TKE of fission fragments as a function of the excitation energy could be understood as the change of the deformation of the heavy fragments in the standard mode, and it dominated a change induced by the increased fraction of the superlong component.Speaker: Satoshi Chiba (Tokyo Institute of Technology) -
09:20
Mapping the fission modes in the neutron-deficient region, from Pt up to Th isotopes with the R3B/SOFIA setup 25m
The low energy fission in the actinide region is known to be mainly asymmetric, driven by structure effects of the nascent fragments [1]. Moreover, we know that there is a transition from asymmetric to symmetric splitting for Thorium isotopes. It was assumed that this latter split would be the main fission mode for lighter nuclei. Unexpectedly, an asymmetric split of the $^{180}$Hg nucleus was observed by Andreyev et al. [2]. This observation triggered a lot of theoretical and experimental work, and further studies in this region confirmed the unexpected asymmetric fission mode [3, 4], which seems to characterize the fission of neutron-deficient nuclei in the sub-lead region.
In order to map this new island of asymmetric fission, a dedicated experiment has been performed at R3B. Using inverse kinematics at relativistic energies with the state-of-the-art SOFIA setup [5], an extraordinary number of fissioning systems have been measured. More than 100 secondary beams from $^{177}$Pt up to $^{221}$Pa, mapping the neutron-deficient region, have been produced and identified through the FRS at GSI. The two fission fragments from the Coulomb-excitation-induced fission of the secondary beam were fully identified at the same time using the unique capabilities of the SOFIA setup at R3B.
For the first time, new charge and mass distributions of the fission fragments have been measured with very high resolution and unprecedented statistics. These outstanding results bring a global and coherent view of the fission process in the neutron-deficient region and set limits on the island of asymmetry.
After detailing the experimental apparatus, the fission-fragment isotopic yields will be discussed and compared to theoretical models.References
[1] G. Scamps and C. Simenel, Nature 564, 382-385 (2018).
[2] A. N. Andreyev et al., Phys. Rev. Lett. 105, 252502 (2010).
[3] M. Warda et al., Phys. Rev. C 86, 024601 (2012).
[4] K. Nishio et al., Phys. Lett. B 748, 89-94 (2015).
[5] A. Chatillon et al., Phys. Rev. Lett. 124, 202502 (2020).Speaker: Pierre Morfouace (CEA) -
09:45
Experimental Prompt Fission Neutron Spectrum Ratios for the Major Actinides 25m
Prompt fission neutron energies play an important role in criticality, and measurements, calculations, and evaluations of them have been of interest, particularly for neutron-induced fission, for some time [1]. The Chi-Nu project at the Los Alamos Neutron Science Center has conducted a series of measurements of the prompt fission neutron spectra for neutron-induced fission, with the most complete description possible of the uncertainties involved. This campaign of measurements has now measured such prompt fission neutron spectra for neutron-induced fission of all of the three major actinides: 239Pu and 235,238U [2-5]. These measurements used essentially the same experimental set up, incoming and outgoing neutron energy ranges, data reduction and analysis methods. This situation allows for improved comparisons of the ratios of the measured prompt fission spectra of these nuclei, for which a number of the highly correlated systematic uncertainties of the measurements largely cancel in the ratios of the resulting prompt fission neutron spectra.
We will present and discuss these PFNS ratios, from Chi-Nu, compared to previous measurements and predictions from various evaluations and models. In addition, future measurements of minor actinide neutron-induced fission and spontaneous fission PFNS will be discussed.*Los Alamos National Laboratory is operated by Triad National Security, LLC, for the National Nuclear Security Administration of the U.S. Department of Energy (Contract No. 89233218CNA000001). Work at Lawrence Livermore National Laboratory was performed under Contract No. DE-AC52-07NA27344.
- See, for example, R Capote, Y-J Chen, et al., Nucl. Data Sheets 131, 1 (2016).
- KJ Kelly, M Devlin, JM O’Donnell, et al., Phys. Rev. C 102, 034601 (2020).
- KJ Kelly, T Kawano, JM O’Donnell, et al., Phys. Rev. Lett. 122, 072503 (2019).
- KJ Kelly, JA Gomez, M Devlin, et al., Phys. Rev. C 105, 044615 (2022).
- KJ Kelly, et al., to be published.
Speaker: Matthew Devlin (Los Alamos National Laboratory) -
10:10
Machine learning collective coordinates of the fission process 25m
Since its discovery, the fission process has been widely described in terms of a few collective coordinates often related to the shape of the nuclear density. As a matter of fact, theoretical approaches estimating a potential energy surface (PES) in a few-dimensional collective space are at the heart of our state-of-the art predictions of the fission yields and the spontaneous fission half-lives.
A widespread implementation of this idea relies on the nuclear Density Functional Theory (DFT). In this framework, the collective coordinates take the form of constraints in the Hartree-Fock-Bogoliubov equations which are associated to a set of ad hoc observables such as the multipole moments of the system. This method performs well at producing adiabatic potential landscapes but is plagued by a known technical issue: the mapping from the collective coordinate (e.g. the deformation) to its associated nuclear state (obtained from the Hartree-Fock-Bogoliubov solver) may not be continuous. The presence of such discontinuities impacts the predictions of fission half-lives and may even prevent studies of the fission dynamics within the time dependent generator coordinate method.
In this presentation I will highlight the development of a novel method to define and compute a set of collective variables suited to describe nuclear deformations in the DFT framework. This method leverages dimension reduction algorithms coming from the field of machine learning such as the auto-encoder. I will emphasize a proof of principle of this method applied to 16O as well as the future road map toward its application to a full-scale fission study.
Speaker: David Regnier
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Fission III: Plenary Sundial I and II
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Photon Cascades from Spinning Fission Fragments 25mSpeaker: Jorgen Randrup (LBNL)
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Isomeric yield ratios obtained via mass measurement techniques for studies of angular momentum generation in fission 25m
Isomeric yield ratios obtained via mass measurement techniques for studies of angular momentum generation in fission
Stephan Pomp1, S. Cannarozzo1, Z. Gao1, A. Al-Adili1, M. Lantz1, A. Solders1, the IGISOL/JYFLTRAP team2, and the FRS Ion Catcher collaboration3
1Uppsala University, Uppsala, Sweden
2University of Jyväskylä, Jyväskylä, Finland
3GSI, Darmstadt, GermanyOne of the open problems in nuclear fission is the origin of the large angular momenta observed in fission fragments [1]. Jon Wilson and co-workers recently published a study suggesting that the fragment spins are generated post-scission and independent of the fissioning system [2]. The latter finds partial support in a recent compilation and evaluation of isomeric yield ratios (IYR) [3]. However, these new results are still under some debate and have been discussed, e.g., at the recent hybrid workshop on Fission Fragment Angular Momenta, hosted by the University of Washington in Seattle [4].
We address this challenging problem by measuring isomeric yield ratios (IYR). We use the latest experimental advances in nuclear mass spectrometry to measure IYR by direct ion counting. The relative population of the different spin states can then used to extrapolate back to the angular momentum of the fission fragment right after scission has occurred.
We have performed a series of measurements of IYR for fission products from 232Th(p,f) and 238U(p,f) at 25 MeV at IGISOL in Jyväskylä, Finland. We also performed a prelimary study of IYR in natU(n,f). First results are reported in Refs [5,6]. Using the Phase-Imaging Ion-Cyclotron-Resonance (PI-ICR) technique [7], allows resolving metastable states with excitations energies as low as a few tens of keV. This opens the possibility for detailed studies of IYR over several neighboring isotopes, mapping, e.g., the 132Sn region. We have carried out a study on odd-mass Cd and In isotopes [8] and, recently, obtained 18 more IYR from 238U(p,f) in the same mass region. Preliminary results have been presented at ND2022 [9].
One interesting result was the behavior of the IYR and the deduced Jrms for the In isotopes. We found that the IYR (defined as population of high-spin state over the sum of the population of both isomeric states) decreases as one moves towards higher masses. This means also that Jrms decreases when moving from 119In to 129In. This behavior is also strongly correlated with the isotopes’ quadrupole moments.
We present the measurement technique, the results obtained so far and describe current work and future plans. One issue we currently address is the impact of initial angular momentum, i.e., the angular momentum of the fissioning system. To this end we are currently performing measurements at the MR-TOF system installed at the FRS Ion Catcher at GSI [10], Germany, to study IYR from 252Cf(sf). There, we will, in 2023, also obtain IYR from 248Cm(sf). Moving, on the other hand, to higher initial spin, we will later this year measure IYR from 232Th(,f) at 30 MeV, again at IGISOL/JYFLTRAP.
The presented work is supported by the Swedish Research Council and the European Union’s Horizon 2020 research and innovation programme under grant agreement no 847552 (SANDA), and the Euratom research and training programme 2014-2018
under grant agreement no 847594 (ARIEL).- J.B. Wilhemy et al., Phys. Rev. C 5, 2041 (1972).
- J. Wilson et al., Nature 590, 566 (2021).
- C.J. Sears et al., Nuclear Data Sheets 173, 118 (2021).
- See https://indico.in2p3.fr/event/26459/
- V. Rakopoulos et al., Phys. Rev. C 98, 024612 (2018).
- A. Mattera et al., Eur. Phys. J. A 54, 33 (2018).
- S. Eliseev et al., Phys. Rev. Lett 110, 082501 (2013).
- V. Rakopoulos et al., Phys. Rev. C 99, 014617 (2019)..
- Z. Gao et al., to appear in the Proceedings of the 15th International Conference on Nuclear Data for Science and Technology (ND2022).
- I. Mardor et al., EPJ Web of Conferences 239, 02004 (2020).
Speaker: Stephan Pomp (Uppsala University, Sweden) -
11:55
Precise measurements of gamma-ray intensities for long-lived fission products 25m
We recently demonstrated a new experimental approach to precisely determine the gamma-ray intensities following the beta decay of long-lived fission products. For national-security applications, such as stockpile stewardship and nuclear forensics, one of the most straightforward and reliable ways to determine the number of fissions that occurred in a chain reaction is done via detection of the emitted gamma rays. The focus of this talk is on recent measurements to improve the nuclear-decay data for the fission products 95Zr, 144Ce, and 147Nd. For these isotopes, and many other fission products, the gamma-ray intensities are desired to high precision for these national-security applications. Our approach consists of implanting fission-product samples into a thin carbon foil using low-energy mass-separated ion beams from the CARIBU facility and then performing beta counting using a custom-made 4-pi gas proportional counter in coincidence with gamma-ray spectroscopy using the precisely-calibrated HPGe detector at Texas A&M University. Recent results for 95Zr, 144Ce, and 147Nd will be presented and future plans will be discussed.
This work was supported under Contract DE-AC52-07NA27344 (LLNL), Office of Nuclear Physics Contract DE-AC02-06CH11357 (ANL), and DE-FG03-93ER40773 (Texas A&M).
Speaker: Kay Kolos (LLNL) -
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Saturation of γ-Ray Multiplicity with Fission Fragment Excitation Energy 20m
New experimental results on the dependence of mean γ-ray multiplicity on the total excitation energy of fission fragments are presented. The measurement setup consists of a twin-Frisch gridded ionization chamber (TFGIC) containing a $^{252}$Cf(sf) source, surrounded by a spherical array of 40 trans-stilbene scintillator detectors. Fragment properties are measured with the TFGIC using the 2E method [1] which provides masses, total kinetic energy, and polar emission angles relative to the TFGIC’s symmetry axis, while prompt fission neutrons and γ rays from the fragments are measured with the scintillator array. Preliminary results indicate that the γ-ray multiplicity increases with increasing total fragment excitation energy and eventually reaches a plateau at some saturation energy. We find that the energies of these positively correlated γ rays are characteristic of stretched quadrupole transitions in the de-exciting fragments [2]. We interpret this γ-ray multiplicity plateau as an angular momentum saturation effect and examine how the saturation energy depends on the fragment mass split.
This work was in part supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE 1256260. This work was in part supported by the Office of Defense Nuclear Nonproliferation Research & Development (DNN R&D), National Nuclear Security Administration, US Department of Energy. This work was funded in-part by the Consortium for Monitoring, Technology, and Verification under Department of Energy National Nuclear Security Administration award number DE-NA0003920. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract Number DE-AC02-06CH11357.
- C. Budtz-Jørgensen, H.H. Knitter, Nucl. Phys. A 490, 307 (1988).
- S. Marin et al., Phys. Rev. C 104, 024602 (2021).
Speaker: Nathan Giha (University of Michigan) -
12:40
Measurements of neutron- and photon-induced fission product yields at TUNL 20m
A joint TUNL-LLNL-LANL collaboration was formed to measure absolute fission product yields from $^{235}$U, $^{238}$U, and $^{239}$Pu. Our goal is to study the energy evolution of fission products by using mono-energetic neutrons from 0.5 to 14.8 MeV [1] and mono-energetic photons from 8 to 15.5 MeV [2]. Measurements are conducted using the activation technique, where fission products are identified and quantified via γ-ray spectroscopy with HPGe detectors. By utilizing a series of different activation times, and a new rapid transfer system [3], we have measured fission products with half-lives from seconds to months.
This work was supported in part by the National Nuclear Security Administration Stewardship Science Academic Alliances, United States grant no. DE-NA0003884, DE-NA0003887, and the U.S. Department of Energy, Office of Nuclear Physics, United States , under grant no. DE-FG02-97ER41033. The work was performed under the auspices of the US Department of Energy by Los Alamos National Laboratory under Contract No. 89233218CNA000001 and Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.
- M.E. Gooden et al., Nucl. Data Sheets 131, 319 (2016).
- Krishichayan et al., Phys. Rev. C, 100 014608 (2019).
- S.W. Finch et al., Nucl. Instrum. Meth A. 1025, 166127 (2022).
Speaker: Sean Finch (Duke University) -
13:00
Fission product yields from mass measurements using the energy-velocity method 20m
Independent Fission Product Yields (IFPY), i.e., yields of fission products right after the prompt neutron emission but before beta decay, are imperative for fundamental physics and nuclear applications. Currently, there is a significant deficiency in IFPY data for incident neutron energies in the MeV range, therefore, developing reliable tools and methods for the measurement of such critical physical quantities is particularly important. The Spectrometer for Ion Determination in fission Research (SPIDER), was developed at Alamos Neutron Science Center (LANSCE) for measuring IFPYs from neutron-induced fission using the double-energy double-velocity method, eventually spanning from thermal up to 20 MeV in incident neutron energy. SPIDER has recently undergone various improvements for increasing the fidelity of the extracted data. In particular, a gamma-ray tagging system has been implemented for improving the accuracy of the mass calibration by measuring strong gamma-ray transitions from isotopes of known mass. In this presentation, an overview of the upgraded SPIDER system and preliminary results from IFPY measurements on $^{252}$Cf(sf), $^{235}$U(n$_{th}$,f), and $^{239}$Pu(n$_{th}$,f) will be discussed.
*This work was performed under the auspices of the US Department of Energy through the Los Alamos National Laboratory. Los Alamos National Laboratory is operated by Triad National Security, LLC, for the National Nuclear Security Administration of the US Department of Energy (Contract No.89233218CNA000001). (LA-UR-22-27609)
Speaker: Panagiotis Gastis (Los Alamos National Laboratory)
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Hosted Lunch 1h 10m Sundial I and II
Sundial I and II
Sundial Beach Resort
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Fission IV: Parallel Sundial I (Sundial Beach Resort)
Sundial I
Sundial Beach Resort
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Informing CGMF with microscopic input 20m
Developed at Los Alamos National Laboratory, CGMF is an open-source code used for determining prompt neutron and gamma-ray properties, including correlations between different observables. Based on a Monte-Carlo implementation of Hauser-Feshbach statistical model of neutron-induced reactions, the code simulates in competition the neutron and gamma emissions from fission fragments, which are assumed to be compound nuclei. As it is the case with the phenomenological approaches, the outcome of the simulations depends on many parameters that determine the fission fragments’ nuclear structure, and on other critical inputs into such simulations like the pre-neutron emission fission fragment yields as well as their kinetic energy, excitation energies, spin, and parity distributions of the fission fragments. For all these quantities only incomplete (e.g., mass/charge yields) or indirect information (e.g., initial angular distribution, or sharing of TXE) exists, which significantly increases the uncertainties possibly reducing the predictive power of the model. In this contribution, I will talk about our efforts to use results from microscopic calculations to inform CGMF. In particular I will concentrate on using information from time-dependent superfluid local density approximation for excitation energy sharing and spin distributions.
Speaker: Ionel Stetcu (Los Alamos National Laboratory) -
14:50
Some Aspects in the A~100 Nuclei Research from 252Cf Spontaneous Fission 20m
Some Aspects in the A~100 Nuclei Research from 252Cf Spontaneous Fission
Enhong Wang1, Y.X. Luo1, J.H. Hamilton1, S.J. Zhu2, B.M.Musangu1, A.V. Ramayya1, J.O. Rasmussen3, S. Jehangir4, G. H. Bhat5,6, J. A. Sheikh6,7, S. Frauendorf8, Y.X. Liu9, Y.Sun10, F.R. Xu11 and Y. Shi11
1Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235
2Department of Physics, Tsinghua University, Beijing 100084, China
3Lawrence Berkeley National Laboratory, Berkeley, CA 94720
4Department of Physics, National Institute of Technology, Srinagar, 190 006, India
5Department of Physics, SP College Srinagar, 190 001, India
6Cluster University Srinagar, Jammu and Kashmir, Gogji Bagh, 190 008, India
7Department of Physics, University of Kashmir, Srinagar, 190 006, India
8Department of Physics,University of Notre Dame, Notre Dame, IN 46556
9School of Science, Huzhou Teachers College, Huzhou 313000, China
10Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, China
11Department of Physics, Beijing University, Beijing 100871, ChinaRecent measurements of the prompt triple --and four fold --- coincidence data emitted in the spontaneous fission fragments of 252Cf using Gammasphere detector array are presented. Fission fragments of 252Cf in the A~100 range lie in the triaxial region. Moreover, maximum triaxial deformation was predicted in Ru nuclei. Recently, Coulomb excitation experiment on 110Ru provided strong evidence for triaxial shape. One and two phonon vibrational bands were identified and extended in neutron rich 102,104,106,108Mo, 110,112Ru, 114Pd. For odd-A nuclei in this region, the first such bands was identified in 105Mo, and followed by 103,105Nb, 103,107Mo, 107,109Tc. Those bands in 102-108Mo show very good systematics and are well reproduced by triaxial projected shell model (TPSM). Possible 3 phonon vibrational bands were proposed in 103,105Nb and 104Mo. Odd parity chiral doublet bands were identified in 104,106Mo, 110,112Ru. These doublet bands show almost degenerate energy levels (100-200 keV) and similar moments of inertia. The tilted axis cranking calculations indicate that the chiral doublets in 104,106Mo originate from the h11/2 quasineutron and a pseudo spin pair of (d5/2 g7/2) quasineutrons. The TPSM calculations on the geometries of the chirality show changes from chiral vibration to static chirality and back to chiral vibration with increasing spin. The wobbling motions were identified in the large triaxial deformed 112Ru and 114Pd from the sign of the signature splitting in the vibrational bands. Comparison with the neighboring Ru and Pd nuclei implies the transition from non-wobbling N=64 isotones to the N = 66 transitional isotones and to the onset of wobbling in the N = 68 isotones. The total Routhian surface (TRS) calculations indicate a shape evolution of the 112-118Pd, where the nuclei shape changes from triaxial prolate via triaxial oblate to nearly oblate, and back to less negative with increasing neutron number.
Speaker: Enhong Wang1 Enhong Wang1 (Vanderbilt University) -
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Anomalous neutron yields confirmed for Ba-Mo and newly observed for Ce-Zr from spontaneous fission of $^{252}$Cf 20m
We reinvestigated the neutron multiplicity yields of Ba-Mo, Ce-Zr, Te-Pd, and Nd-Sr from the spontaneous fission of $^{252}$Cf; by (i) using both $\gamma$-$\gamma$-$\gamma$-$\gamma$ and $\gamma$-$\gamma$-$\gamma$ coincidence data, (ii) using up to date level scheme structures, and (iii) cross-checking analogous energy transitions in multiple isotopes, we have achieved higher precision than previous analyses. Particular attention was given to the Ba-Mo pairs where our results clearly confirm that the Ba-Mo yield data have a second hot fission mode where 8, 9, 10, and now 11 neutron evaporation channels are observed. These are the first observations of the 11 neutron channel. These 8-11 neutron channels are observed for the first time in the Ce-Zr pairs, but are not observed in other fission pairs. The measured intensities of the second mode in Ba-Mo and Ce-Zr pairs are $\sim$1.5(4)$\%$ and $\sim$1.0(3)$\%$, respectively. These high neutron number evaporation modes can be an indication of hyperdeformation and/or octupole deformation in $^{143-145}$Ba and in $^{146,148}$Ce at scission to give rise to such high neutron multiplicities.
Speaker: Dr Brooks M. Musangu (Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA) -
15:30
Isotopic fission yields and mass measurements from 252Cf spontaneous fission at the FRS Ion Catcher 20m
Measurements of independent isotopic fission yields (IIFYs) provide access to the probability distribution of fission products, which contribute to understanding nuclear fission in more depth than mass yield distributions. Better knowledge of fission has wide implications, including the abundance of elements through nucleosynthesis, nuclear structure and reactions, and nuclear waste management and safety [1].
We present the first results of a novel method for measuring IIFYs of spontaneous fission (SF) via direct mass measurements [2], at the FRS Ion Catcher (FRS-IC) at GSI [3]. Fission products were generated from a $^{252}$Cf source installed in the cryogenic stopping cell (CSC) [4], and were identified and counted with the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) [5] of the FRS-IC, utilizing well-established measurement and data analysis methods [6]. The MR-TOF-MS resolves isobars unambiguously, even with limited statistics, and its non-scanning nature ensures minimal relative systematic uncertainties amongst fission products.
Our high-accuracy mass results constitute by themselves new important data, as they include first direct mass measurements in the N≈90 and Z=56-62 region. We compare our results to previous indirect measurements and to AME2020 [7].
The analysis for extracting IIFYs includes isotope-dependent efficiency corrections for all components of the FRS-IC. In particular, we applied a self-consistent technique that takes into account the element-dependent survival efficiencies in the CSC, due to chemical reactions with the buffer gas.
Our IIFY results, which cover several tens of fission products in the less-accessible high-mass peak down to fission yields at the level of 10-5, are generally similar to those of ENDF/B-VII.0 [8]. Nevertheless, they reveal some structures that are not observed in the database smooth trends.
These are the first results of a planned campaign to investigate IIFY distributions of spontaneous fission at the FRS-IC. Upcoming experiments will extend our results to wider Z and N ranges, lower fission yields, and other spontaneously-fissioning actinides.- Dimitriou et al., IAEA Report INDC(NDS)-0713 (2016)
- Mardor et al., EPJ Web of Conferences 239, 02004 (2020)
- W. R. Plass et al., Nucl. Inst. Meth. B 317, 457 (2013)
- M. Ranjan et al., Nucl. Inst. Meth. A 770, 87 (2015)
- T. Dickel et al., Nucl. Inst. Meth. A 777, 172 (2015)
- S. Ayet San Andres et al., Phys. Rev. C 99, 064313 (2019)
- M. Wang et al., Chinese Phys. C 45 030003 (2021)
- ENDF/B-VII.0 data extracted from: National Nuclear Data Center, NuDat 3 database, https://www.nndc.bnl.gov/nudat3/
Speaker: Israel Mardor (Tel Aviv University) -
15:50
Fission as Access to Spectroscopy Around 132Sn 20m
see attached
Speaker: Radomira Lozeva (IJCLab, CNRS/IN2P3) -
16:10
FISSION PRODUCT YIELDS DETERMINED FROM GAMMA-RAY SPECTROSCOPY USING THE GODIVA IV CRITICAL ASSEMBLY 20m
The last major evaluation of fission product yields from actinides was a compendium put together in 1994. It forms the basis for the current fission product yields for various incident neutron energies on actinide isotopes (ie: U235, U238). In 2010, the Godiva critical assembly was re-commissioned by the Department of Energy, led by Los Alamos National Laboratory, at the National Criticality Experiments Research Center in Nevada. This critical assembly can be used as a source of pulsed fission spectrum neutrons to activate and fission sample of material placed in the core of the critical assembly. After irradiation, the material is then retrieved from the critical assembly and time dependent gamma-ray spectroscopy data was collected in list mode. Using the characteristics gamma-rays from known isotopes we can determine the fission product yields for numerous isotopes. The nature of the time dependent spectroscopy allows the confirmation of the half-life of each identified isotope. To date, U235, U238, Pu239, Np237 and U233 fission product yields have been measured using this approach. This method confirms that there are no gamma-ray interferences underlying the gamma-ray peak of interest. Various time scales of fission product isotopes necessitate the use of different approaches to retrieve samples which are currently being developed. The experimental method, facilities, results and new developments will be presented and discussed.
This work was funded by the Office of Defense Nuclear Nonproliferation Research and Development within the U.S. Department of Energy’s National Nuclear Security
Administration by Lawrence Livermore National Laboratory under Contract No DE-AC52-07NA27344. The U.S. Department of Energy’s Nuclear Criticality Safety Programs National Criticality Experiments Research Center (NCERC), utilized in this work, is supported by the National Nuclear Security Administration’s Office of the Chief of Defense Nuclear Safety, NA-511.- A.S. Tamashiro et al., Np237 Fission Spectrum Cumulative Fission Product Yield Measurement Using Godiva IV Critical Assembly, Nuclear Data Sheets, submitted July 2022
- A.S. Tamashiro et al., Pu239 Fission Spectrum Cumulative Fission Product Yield Measurement Using Godiva IV Critical Assembly, Nuclear Data Sheets, submitted July 2022
Speaker: J.T. Harke (LLNL)
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Neutron Rich II: Parallel Sundial I and II
Sundial I and II
Sundial Beach Resort
1451 Middle Gulf Drive Sanibel, FL 33957-
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HIGH-SPIN LEVEL STRUCTURES OF NEUTRON-RICH As Se AND ADJACENT NUCLEI WITH 46≤N≤50 20m
HIGH-SPIN LEVEL STRUCTURES OF NEUTRON-RICH As Se AND ADJACENT NUCLEI WITH 46≤N≤50
William B Walters
Dept. of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742The theoretical groundwork for interpretation of the structures of neutron rich Ni, Cu, Zn, Ga, Ge, As, Se and Br N = 50 isotones was laid by my colleague Xiangdong Ji and the late Hobson Wildenthal [1] who correctly indicated an f5/2 ground state for 79Cu long before Franchoo et al., reported supporting data with the identification of the monopole shift for 69,71,73Cu. [2]. New data will be presented that provides insight into the position of the g9/2 proton state as the Fermi level moves from Z = 28 to Z = 50. These data have an impact on identifying the location of neutron 1 particle-2-hole structures, including high-spin levels associated with the established 583-keV d5/2 state in 83Se. Evolution of level structures in the 80,82,84Se46,48,50 nuclei will include both multi-nucleon transfer and capture-gamma data from the cold-neutron beam at the NIST reactor. New high-spin data will be presented for odd-mass N = 47 and N = 49 79,81Ge nuclei that can be interpreted in the light of the recent measurement of the quadrupole moment of 80Ge by Rhodes et al. [3]. For those interested in the structure of 80Ge, support for placing the position of the 2-neutron-hole-2 proton 10+ level at 4951 keV will be presented. New data for the N = 46 isotone, 79As, includes two high-spin sequences that appear to have different shapes. One is built on the g9/2 proton particle state that appears to be oblate, and another on the f5/2 proton hole state that appears to be prolate.
This work was supported in part by the US Department of Energy, Office of Nuclear Physics, under Grant No. DE-FG02-94ER40834 and Contract No. DE-AC02-06CH11357, and used resources of ANLs ATLAS facility, which is a DOE Office of Science User Facility. Involvement of the following people has been invaluable: C. J. Chiara, A. D. Ayangeakaa, A. M. Forney, N. Hoteling, R.V.F. Janssens, B. A. Brown, J. Purcell, I. Stefanescu, M. P. Carpenter, D. Seweryniak, A. A. Hecht, J. Sethi, J. Harker, B. Cummings, M. Waite, A. Hutchison, N. Sharp, R. Bindel, L. M. Fraile, S. Sekal, J. Greene, M. Alcorta, G. Gürdal, C. R. Hoffman, B. P. Kay F. G. Kondev, T. Lauritsen, C. J. Lister, E. A. McCutchan, A. M. Rogers, B. Fornal, R. Broda, W. Królas, J. Wrzesiński, and T. Pawłat.
Particular appreciation is accorded the late Shaofei Zhu for his many contributions to this and numerous other Gammasphere undertakings.[1] X. Ji and B. H. Wildenthal, Phys. Rev. C 37, 1256 (1988); C 40, 389 (1989).
[2] S. Franchoo et al., Phys. Rev. Lett. 81, 3100 (1998); Phys. Rev. C 64, 054308 (2001).
[3] D. Rhodes et al., Phys. Rev. C 105, 024325 (2022).Speaker: Prof. William Walters (Maryland) -
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Nuclear moments of indium isotopes reveal abrupt change at magic number 82 20m
In this contribution, we present measurements of the nuclear magnetic dipole moments and nuclear electric quadrupole moments of the 113-131In isotope chain, performed using the Collinear Resonance Laser Spectroscopy experiment at ISOLDE, CERN.
We show that the electromagnetic properties of the neutron-rich indium isotopes significantly differ at N = 82 compared to N < 82, despite the single unpaired proton dominating the behaviour of this complex many-body system. This challenges our previous understanding of these isotopes, which were considered a textbook example for the dominance of single-particle properties in nuclei [1, 2].
To investigate the microscopic origin of our experimental results, we performed a combined effort with developments in two complementary nuclear many-body methods: ab-initio valence space in-medium similarity normalization group [3,4] and density functional theory [5].
When compared with our experimental results, contributions from previously poorly constrained time-odd channels [6,7], and many-body currents [8] are found to be important, demonstrating electromagnetic properties of ‘proton-hole’ isotopes around magic shell closures at extreme proton-to-neutron ratios can give us crucial insights.
Speaker: Dr Adam Vernon (Massachusetts Institute of Technology) -
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Less is More: Enabling Uncertainty Quantification and Large Scale Studies in Nuclear Physics Through Dimensionality Reduction 20m
We present the reduced basis method (RBM) - a dimensionality reduction technique - as a tool for developing emulators for equations with tunable parameters within the context of the nuclear many-body problem. The RBM uses a basis expansion informed by a set of solutions for a few values of the model parameters and then projects the equations over a well-chosen low-dimensional subspace. We have connected some of the results in the eigenvector continuation literature to the formalism of RBMs and showed how RBMs can be applied to a broader set of problems. We apply the RBM to nuclear density functional theory for Skyrme type interactions as well as relativistic mean field models. The outstanding performance of the approach, together with its straightforward implementation, show promise for its application to the emulation of computationally demanding calculations, including Bayesian uncertainty quantification and large scale systematic studies of nuclear dynamics.
Speaker: Pablo Giuliani (Michigan State University) -
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Exploring Nuclear Dynamics Beyond Mean-Field 20m
Atomic nuclei are remarkable mesoscopic systems where single nucleon excitations coexist and interact with numerous collective features such as pairing correlations, clustering, shape dynamics, and collectivities related to decay.
In this work we report our recent progress in studies of coherent and chaotic excitations in nuclear medium. We discuss pairing and many-body correlations, formation of mean field and asymptotic normalization of single-particle and cluster reaction channels. Emergence of nuclear collectivities and interplay between them are among questions of interest. Broad range of model studies and realistic examples will be presented.
This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics under Award Number DE-SC0009883.
Speaker: Alexander Volya (Florida State University) -
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Structure of neutron unbound nuclei 13Be and 10Li 20m
see attachment
Speaker: Grigory Rogachev (Texas A&M University) -
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Revisiting the β-delayed neutron emission of neutron-rich As isotopes with MONSTER 20m
A better quantitative understanding of β-delayed neutron emission rates and spectra is relevant for nuclear structure, astrophysics, and reactor applications: β-delayed neutrons provide valuable information on the β-decay process, are needed in network calculations for understanding the stellar nucleosynthesis process, and can improve the understanding of the kinematics and safety of new reactor concepts loaded with new types of fuels. The field has experienced an increased activity during the last decades [1] thanks to the advances in nuclear experimental techniques and the radioactive ion beam facilities. More accurate measurements of β-delayed neutron emission properties like the emission probability, β-feeding, and energy spectrum from individual precursors are being made with advanced neutron detectors [2, 3, 4], digital data acquisition systems [5], and high intensity ion beams [6, 7, 8, 9].
The β-delayed neutron emission in the $^{85,86}$As decays has been measured at the Ion Guide Isotope Separator On-Line (IGISOL) facility [9] of the JYFL Accelerator Laboratory of the University of Jyväskylä. The $^{85,86}$As isotopes were produced by proton-induced fission reactions in 238U, separated from the rest of the fission fragments with IGISOL, and implanted onto a tape. The complete decays have been studied with the help of a complex setup which consists of a plastic scintillator detector for the emitted β-particles, a HPGe Clover and four LaBr3 detectors for the emitted γ-rays, and the MOdular Neutron SpectromeTER (MONSTER) [4, 10] for the detection of the emitted neutrons. MONSTER consists of an array of 48 cylindrical cells of 200 mm diameter and 50 mm height, filled with BC501A or EJ301 scintillating liquid. Each cell is coupled through a light guide of 31 mm thickness to a R4144 or R11833 PMT. The neutron energy is determined by the time-of-flight technique, using the signals from the plastic detector and MONSTER as the start and stop signals, respectively.
In this conference, we report the results obtained from the measurement at JYFL. The β-delayed neutron energy distribution of the $^{85,86}$As β-decays has been determined by unfolding the time-of-flight spectrum with the iterative Bayesian unfolding method [11], and their partial branching ratios to the excited states in the final nucleus by applying β-n-γ coincidences. We also compare the results of this work to existing data [12, 13].
- P. Dimitriou et al., Nuclear Data Sheets 173, 144-238 (2021).
- A. Buţă et al., Nucl. Instrum. and Methods A 455, 412-423 (2000).
- C. Matei et al., Proceedings of the 10th International Symposium on Nuclei in the Cosmos, 138, Proceedings of Science, 1-5 (2008).
- A.R. Garcia et al., JINST 7, C05012 (2012).
- D. Villamarin et al., In preparation.
- W.F. Henning et al., GSI publication, (2001).
- H. Okuno et al., Prog. Theor. Exp. Phys., 03C002 (2012).
- R. Catherall et al., Nucl. Instrum. and Methods B 317, 204-207 (2013).
- I.D. Moore et al., Nucl. Instrum. and Methods B 317, 208 (2013).
- T. Martinez et al., Nuclear Data Sheets 120, 78 (2014).
- G. D’Agostini, Nucl. Instrum. and Methods A 362, 487-498 (1995).
- K.-L. Kratz et al., Nucl. Phys. A 317, 335 (1979).
- D. Rudstam et al., Data and Nucl. Data Tables 53, 1 (1993).
Speaker: Mr Alberto Pérez de Rada Fiol (CIEMAT)
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Coffee Break 30m Sundial I and II
Sundial I and II
Sundial Beach Resort
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Fission V: Invited Sundial I and II
Sundial I and II
Sundial Beach Resort
1451 Middle Gulf Drive Sanibel, FL 33957-
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The role of octupole deformed shell on fission of actinides and in the mercury region 25m
Nuclear fission of heavy (actinide) nuclei results predominantly in asymmetric mass-splits. Without quantum shells, which can give extra binding energy to these mass-asymmetric shapes, the nuclei would fission symmetrically. The strongest shell effects are in spherical nuclei, so naturally, the spherical "doubly-magic" 132Sn nucleus, was expected to play a major role.
However, systematic studies of fission have shown that the heavy fragments are distributed around Z=52 to 56, indicating that 132Sn is not the only driver. Reconciling the strong spherical shell effects at Z=50 with the different Z values of fission fragments observed in nature has been a longstanding puzzle. Here, we show that the final mass asymmetry of the fragments is determined by the extra stability of octupole (pear-shaped) deformations which have been recently found experimentally around 144Ba (Z=56), one of the very few nuclei with shell-stabilized octupole deformation. Using a modern quantum many-body model of superfluid fission dynamics, we found that heavy fission fragments are produced predominantly with 52-56 protons, associated with significant octupole deformation acquired on the way to fission. These octupole shapes favouring asymmetric fission are induced by deformed shells at Z=52 and 56 [1]. In contrast, spherical "magic" nuclei are very resistant to octupole deformation, which hinders their production as fission fragments.
These findings also explain surprising recent observations of asymmetric fission of lighter than lead nuclei. Such as the discovery that 180Hg fission is mass asymmetric instead of being symmetric with two semi-magic 90Zr fragments [2]. To test the universality of the octupole effect on fisison, we investigate with the constraint Hartree-Fock + BCS approach the effect of quadrupole and octupole deformations on the fission asymmetry of elements around 180Hg. The density at the scission as well as the neutron localisation function from which quantum shell signatures can be investigated show clearly an octupole deformation of the fragments[3].
[1] G. Scamps and C. Simenel, Nature 564, 382–385 (2018).
[2] A. N. Andreyev, Phys. Rev. Lett. 105, 252502 (2010).
[3] G. Scamps and C. Simenel, Effect of shell structure on the fission of sub-lead nuclei, Phys. Rev. C 100, 041602(R) (2019).Speaker: Guillaume Scamps (University of Washington) -
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Recent Progress in the Microscopic Description of Neutron-Induced Fission 25mSpeaker: Nicolas Schunck (LLNL)
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Measuring pre-actinide fission charge distributions via light ion induced fusion-fission with heavy rare isotope beams 20m
Prompted by the discovery of an unexpected region of asymmetric, beta-delayed fission in the neutron deficient mercury region, we have developed the capability to fuse neutron-deficient rare isotope beams on 4He within the Active-Target Time Projection Chamber (AT-TPC)[1] and measure their charge distributions.
First measurements with this technique have been performed with neutron deficient beams in the pre-actinide region at the National Superconducting Cyclotron Laboratory. The isotopes were produced by projectile fragmentation of a stable 208Pb beam, identified with a new HEavy Isotope Tagger (HEIST) [2] and then transmitted to the AT-TPC. The 4He counter gas in the AT-TPC provides the target nuclei for fusion-fission reactions and serves as the fission fragment detector. This allows for the separation of fission events from other reactions, and enables the identification of the charge of the fission fragments through their stopping power.
In this talk, we present first results for the measured nuclei. We also discuss the potential for extending these measurements at FRIB to neutron deficient 184Pb.
We would like to acknowledge support from Michigan State University, the U.S. Department of Energy (Grant No. DE-NA0003908).
1. J. Bradt et al., Nucl. Instrum. Methods Phys. Res. A, 875 (2017).
2. A.K. Anthony et al., Rev. Sci. Instrum. 93, 013306 (2022).Speaker: Adam Anthony (MSU/FRIB) -
18:10
Application of Cassini shape parameterization to five-dimensional Langevin approach to fission 20m
The Cassini shape parameterization has been applied to describe the nuclear shape in a static approach to fission1, and more recently, it was used to predict the fragment mass distribution (FMD) for the fission of super-heavy nuclei using an improved scission-point model2. In the latter calculations, the main fission coordinate α is fixed at a value corresponding to pre-scission shape, and the deformation potential is minimized with respect to four Cassini parameters α1, α3, α4, and α6: mass asymmetry, shape asymmetry, quadrupole deformation of fragments, and octupole deformation of fragments, respectively. However, the dynamical simulation of the fission process with the time evolution of α and {αn} has not been realized so far. As a next step, it is logical to use the generalized Cassini ovals also in the frame of a dynamical approach and this is the goal of the present study.
We therefore solve the five-dimensional (5D) Langevin equation with the following Cassi-ni parameters: α, α1, α3, α4, α6. Figure 1 shows the FMD for the 14 MeV neutron-induced fission of 235U calculated by the Langevin equations and measured3. It also shows the results of the Langevin calculations in the 3D space {α, α1, α4} and the 4D space {α, α1, α3, α4} to understand the role of α3 and α6. By including the shape asymmetry α3, the peak position moves from 95+141 to 100+136, which better reproduces the experimental data. The remaining discrepancy may be due to more neutrons emitted from the light fragment and to the neglect of 2nd chance fission. The inclusion of α6 shows only a small change compared to the 4D result. It should be reminded that α6 was found to be important for describing the isotopic change of FMD in spontaneous fission of Fm isotopes4. We conclude that the five Cassini parameters {α, α1, α3, α4, α6} are essential in describing the fission of actinide and super-heavy nuclei.
References
1. V. V. Pashkevich, Nucl Phys. A 169, 275 (1971).
2. N. Carjan, F. A. Ivanyuk and Yu. Ts. Oganessian, Phys. Rev. C 99, 064606 (2019).
3. K. Shibata et al., J. Nucl. Sci. Technol. 48 (1), 1-30 (2011).
4. K. Okada, T. Wada and N. Carjan, ND2022 (Online, July 25, 2022).Speaker: Mr Kazuki Okada (Kansai University) -
18:10
Role of entrance channel magicity in fusion fission dynamics 20m
The role of shell closures of target-projectile combinations in fusion fission dynamics has been explored in an experimental campaign carried out at the accelerator facilities in India. Fission fragments from 224Th populated using the reactions 16O + 208Pb (both the target & projectiles doubly magic), 18O + 206Pb (both proton shell closed) and 19F + 205Tl (no shell closures), have been detected using MWPC and fission fragment mass and total kinetic energy distributions have been analysed. A correlation is observed in the width of the fission fragment mass distributions with the entrance channel magicity (Nm, defined as the number of magic numbers involved with target and projectile). For the reaction 16O + 208Pb ( Nm=4) the width of the mass distributions was found to be the widest. Similar correlation has been observed in the mean total kinetic energy distribution of the fission fragments at an excitation energy of around 35 MeV. A quantitative analysis of the fraction of asymmetric component in the fission fragment mass distribution shows a trend with the entrance channel magicity of the reaction. Since the reactions have low entrance channel charge products ZPZT<800, quasi fission maybe improbable and the asymmetric component of the mass distribution is correlated to be governed by the shell effect in the dynamics. Such results have a profound impact in our present understanding of fusion fission dynamics and may aid in the judicious selection of target-projectile combinations for super heavy element (SHE) synthesis.
Speaker: Mr A. Sen (Variable Energy Cyclotron Centre)
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Facilities Sundial I and II
Sundial I and II
Sundial Beach Resort
1451 Middle Gulf Drive Sanibel, FL 33957-
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Physics perspectives and highlights of FAIR 25m
The accelerator facility for Antiproton and Ion Research FAIR, one of the largest research infrastructures in Europe, is currently being built adjacent to the campus of GSI, Helmholtzzentrum für Schwerionenforschung, in Darmstadt. A suit of accelerators and storage rings will offer excellent research opportunities in hadron and nuclear physics, in atomic physics and nuclear astrophysics as well as in applied sciences like materials research, plasma physics and radiation biophysics with applications towards novel medical treatments and space science. FAIR is an international facility with 10 partner countries. More than 2500 scientists and engineers from more than 50 countries are involved in the preparation and definition of the research at FAIR. Science of FAIR is organized in four pillars: PANDA is a large experimental set-up to study proton-antiproton collisions; NUSTAR represents the nuclear structure, nuclear reaction and astrophysics community and is focused on the exotic isotope facility Super-FRS; CBM stands for the exploitation of dense baryonic matter with heavy ion collisions, and atomic physics, plasma physics, biophysics and materials science are gathered within the APPA pillar. While the full potential of FAIR can only be exploited once the accelerators have been constructed and become operational, some of the experimental instrumentations are already available and are being utilized in a dedicated research program FAIR Phase-0 at GSI, exploiting the upgraded accelerator chain at GSI, and the international collaborations are intensively preparing the Day-1 program at FAIR.
The scientific potential of FAIR will be presented in this talk and the status of the construction will be summarized with a special focus on the activities and the scientific results of FAIR Phase-0.
Speaker: H.M. Albers (GSI) -
08:50
Neutron rich nuclei and fission studies at the IGISOL facility 25m
The Ion Guide Isotope Separator On-Line (IGISOL) facility at the Accelerator Laboratory of the University of Jyväskylä (JYFL-ACCLAB) has since 1984 utilized particle induced fission as means to produce neutron-rich nuclei for various spectroscopy studies and mass measurements [1]. Committed research work include β- and β -ɣ spectroscopy, total absorption ɣ-ray spectroscopy (TAGS), β-delayed neutron spectroscopy, and collinear laser spectroscopy. Examples of each kind studies can be found in references [2-6]. In addition, fission yields (FY) and isomeric yield ratios (IYR) have been measured using the IGISOL facility [7-9].
The presentation gives an overview on the current status of the fission related work at the IGISOL facility, focusing in particular on the recent technical developments such as the commissioning of the Multireflection Time-Of-Flight (MR-TOF) device and the performance of the new sputtered uranium targets [10]. In addition, the developments for fission yield measurements will be discussed.
- I.D. Moore, P. Dendooven & J. Ärje, Hyperfine Interact 223, 17–62 (2014).
- M. Vilen et al., Phys. Rev. C 105, 034312 (2022).
- J. Kurpeta et al., Phys. Rev. C 105, 034316 (2022).
- V. Guadilla et al., Phys. Rev. Lett. 122, 042502 (2019).
- R. Caballero-Folch et al., Phys. Rev. C 98, 034310 (2018).
- L. J. Vormawah et al., Phys. Rev. A 97, 042504 (2018).
- H. Penttilä et al., Eur. Phys. J. A, 52 (2016) 104.
- V. Rakopoulos et al., Phys. Rev. C 99, 014617 (2019).
- A. Al-Adili et al., EPJ Web of Conferences 256, 00002 (2021).
- H. Penttilä et al., in Proc. European Research Reactor Conference RRFM 2021, https://www.euronuclear.org/scientific-resources/conference-proceedings/.
Speaker: Heikki Penttilä -
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Status of GRETA and Results from GRETINA 25mSpeaker: Paul Fallon (Lawrence Berkeley National Laboratory)
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The gamma-ray tracking array AGATA at LNL 25m
The gamma-ray tracking array AGATA at LNL
Gamma-ray spectroscopy represents one of the most powerful methods to study nuclear structure since a large fraction of the de-excitation of the excited nuclear levels goes via gamma emission. The precise measurement of the gamma rays emitted from nuclear levels can provide a large amount of information of the nuclear structure of the specific nucleus under study. The continuous improvement in germanium gamma-array performances and in their associated instrumentation has allowed an enormous increase of the experimental sensitivity. The current forefront Ge gamma-array in Europe is AGATA [1] which is based on the new concept of gamma-ray tracking. It can identify the gamma interaction points (pulse shape analysis) and of reconstructing via software the trajectories of the individual photons (gamma-ray tracking). The state-of-the-art gamma-ray tracking AGATA array had it first implementation at Laboratori Nazionali di Legnaro (LNL) in 2009 with 5 AGATA triple Clusters, the so called AGATA demonstrator [2]. The AGATA gamma spectrometer has return to LNL with the new 2$\pi$ solid angular coverage configuration. The first physics campaign started in spring 2022 where AGATA was coupled to the magnetic spectrometer PRISMA and other compatible ancillary detectors. In this presentation, a review on the achievements in nuclear structure physics and future physics campaigns with the gamma-ray tracking AGATA will be discussed.
[1] A. Akkoyun et al., NIM A 668, 26 (2012).
[2] A. Gadea, et al., NIM A 654, 88 (2011).Speaker: Jose Javier Valiente Dobon (lnl infn it) -
10:05
First experiments at the Super Heavy Element Factory at Dubna 25m
First experiments at the Super Heavy Element Factory at Dubna
Krzysztof P. Rykaczewski
Physics Division, ORNL
The Super Heavy Element Factory [1] has been built and commissioned at the Joint Institute for Nuclear Research (JINR) at Dubna (Russia). It accommodates the new heavy ion cyclotron DC-280 [2] coupled to the new gas filled separator DGFRS-2 [3]. The DGFRS-2 transmission of about 60% was established using several hot fusion reactions.
Number of experiments was performed already with actinide targets and an intense 48Ca beam, up to 6.8 part*microAmp [4]. New results include tens of decay chains of Z=115 moscovium nuclei including a new isotope 286Mc [5] synthesized at the rare 5n evaporation channel. New data on Spontaneous Fission activities have been obtained including a new isotope 264Lr [5] observed at the end of the long 288Mc decay chain. The 288Mc has now the best studied super heavy isotope decay sequence with over 200 chains recorded to date worldwide.
The selected results and their importance will be presented and discussed.
ORNL co-authors were supported by the U.S. DOE Office of Nuclear Physics under DOE Contract No. DE-AC05-00OR22725 with UT Battelle, LLC.
[1] S. Dmitriev, M. Itkis, Yu. Ts. Oganessian, EPJ Web Conf. 131 (08001) (2016) 1–6, http://dx.doi.org/10.1051/epjconf/201613108001.
[2] G.G. Gulbekian, S.N. Dmitriev, M.G. Itkis, Yu. Ts. Oganessian et al.,
Phys. Part. Nuclei Lett. 16 (6) (2019) 866–875,
http://dx.doi.org/10.1134/S1547477119060177
[3] Yu. Ts. Oganessian, V.K. Utyonkov, A.G. Popeko et al., NIM A 1033, 166640, 2022.
[4] Yu. Ts. Oganessian, V.K. Utyonkov, D. Ibadullayev et al., Phys. Rev. C, in press.
[5] Yu. Ts. Oganessian, V.K. Utyonkov et al., submitted to Phys. Rev. C (2022).Speaker: Krzysztof Rykaczewski ( Physics Division, ORNL)
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Sundial Beach Resort
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Superheavy Elements Sundial I and II
Sundial I and II
Sundial Beach Resort
1451 Middle Gulf Drive Sanibel, FL 33957-
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Recent Results from Superheavy Element Searches at RIKEN 25mSpeaker: Hideyuki Sakai (RIKEN Nishina Center)
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Recent Results from AGFA on Heavy Elements 25m
In-beam, K-isomer, $\gamma$-decay and spontaneous fission spectroscopy of trans-fermium nuclei provide a stringent test of nuclear models which are used to describe the heaviest known nuclei. To extend these studies to heavier, more proton-rich, odd-A, odd-odd nuclei, the Argonne Gas-filled Fragment Analyzer (AGFA) was constructed. During the talk, recent decay and isomer spectroscopy experiments with AGFA in stand-alone mode and in-beam spectroscopy experiments with AGFA coupled to Gammasphere will be reviewed. Among others, the observation of the ground-state rotational band in the fissile nucleus $^{254}$Rf, and the discovery of the new isotope $^{251}$Lr will be presented. The impact of these results on shape evolution in this region of nuclei will be discussed. Plans for studies of heavy nuclei with AGFA will be also presented.
This material is based upon work supported by the U.S Department of Energy, Office of Science, Office of Nuclear Physics, under contract number DE-AC02-06CH11357. This research used resources of ANL's ATLAS facility, which is a DOE Office of Science User Facility.
Speaker: Dariusz Seweryniak (Argonne National Laboratory) -
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Recent Results from the BGS and FIONA 25m
The search for new elements has netted us six additions to the periodic table within the last decade and more than 50 isotopes of these elements. All of these new superheavy elements (SHE) must be formed one-atom-at-a-time in complete-fusion evaporation reaction. Once formed, the atoms typically exist for just seconds or less before they decay into other elements. Since discovering these elements, the field has made great gains in understanding the alpha or spontaneous fission decay properties of these elements, and even some experiments have begun to investigate the nuclear structure of the SHE. However, there is much that is still unknown, from the proton and neutron numbers to nuclear shapes, nuclear structure, and the impact of relativistic effects on the chemistry of SHE.
At Lawrence Berkeley National Laboratory we utilize the Berkeley Gas-filled Separator (BGS) and then new mass analyzer, FIONA to begin probing these very questions. The goal of BGS+FIONA is to provide a M/deltaM separation of ~300 and transport nuclear reaction products to a shielded detector station on the tens of milliseconds timescale. Recently, FIONA has been used to investigate new neutron-deficient isotopes, of interest due to their potential electron-capture delayed fission decay, and the chemistry of the heaviest elements. Here I will present on recent experiments and discuss ongoing upgrades to the BGS and FIONA that will allow for even more experiments in the future.
Speaker: Jacklyn Gates (Lawrence Berkeley National Laboratory) -
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Laser spectroscopy and high-precision mass measurements of heavy elements at GSI 25m
In recent years the investigation of atomic and nuclear properties of very heavy and super heavy elements at GSI has been extended in recent years. New technological and methodological developments enabled laser spectroscopy in the heavy actinides and high-precision mass measurements up to the superheavy elements dubnium. Thanks to the supreme mass resolving power of the Penning-trap setup SHIPTRAP even low-lying and long-lived isomeric states were studied. Laser spectroscopy studies provided among others data on the shape and size of very heavy nuclei obtained from hyperfine spectroscopy and isotope-shift measurements.The combination of theses often complementary techniques provide a more comprehensive picture of the nuclear structure evolution in the heaviest nuclei where the repulsive Coulomb force and the attractive nuclear force have a similar strength. In this contribution I will introduce the key techniques and provide recent results obtained in the FAIR phase-0 beam times at GSI in 2020-2022.
Speaker: Michael Block (GSI / HIM / JGU) -
12:40
Es Break in Actinide Hydration Structure 25m
A systematic Actinide Contraction of the ionic radius is generally observed for all elements belonging to the actinide series. In the case of a trivalent actinide ion, filling the inner 5f orbitals with one electron in an atomic numbering order in the electron configuration of [Rn]5fn (n = 0 - 14) results in an ion radius contraction of approximately 1.6%. Understanding such a systematic change is extremely important for elucidating the coordination structure, the electron configuration, the effects of relativistic effects, and so on. Here, we reported the hydration bond distance of trivalent Einsteinium (Es) for the first time in the solution state and found an unexpected contraction of the ionic radius of about 3.7% from Cf3+, the so-called "Einsteinium Break". In comparison with the nuclear shielding constant of Slater's f-orbital electrons, it was found for the first time that this contraction corresponds to a decrease of about one f-orbital electron in the shielding capacity of hydrated Es3+, and from the comparison of ionic radii based on theoretical calculations, it is presumed that the contraction is due to a change in electron configuration, such as f-d promotion. The chemical reactions of heavy elements may involve complex interactions that have not yet been elucidated, such as orbital and spin interactions due to relativistic effects. Further elucidation of this phenomenon will lead to a deeper understanding of the diversity of chemical reactions of heavy elements.
Speaker: Dr Tsuyoshi Yaita (Japan Atomic Energy Agency) -
13:05
Chemical studies of the heaviest known elements: nihonium (element 113), flerovium (element 114), and moscovium (element 115) 25m
All elements up to oganesson (element 118) have been discovered and officially accepted, filling up the 7th period of the periodic table of chemical elements. Experimental chemical investigations of the heaviest elements have also made tremendous progress in the last decades. Currently, the focus is on copernicium (Cn, element 112), nihonium (Nh, element 113), flerovium (Fl, element 114), and mocovium (Mc, element 115). Relativistic effects render Cn, Nh, and Fl more chemically inert than their lighter homologs due to the energetic stabilization and spatial contraction of the outermost 7s1/2 and 7p1/2 orbitals, which was realized already in the 1970s [1] and is confirmed in more current state-of-the-art molecular, cluster, and solid-state relativistic calculations (cf., e.g., [2]). Experimentally, such effects are explored using gas phase chromatographic techniques, which allow studying single atoms of these elements and probing their volatility and reactivity towards hetero-surfaces like silicon oxide or gold, also in relation to the properties of their lighter homologs as well as the noble gas radon [3,4].
Whereas the chemical properties of Cn have been reproducibly studied [4] and shown that the trend in adsorption strength on a Au surface established by the lighter group-12 homologs is followed by Cn [5], only fragmentary and unconfirmed information mostly gained in studies that suffered from considerable background is available on Nh [4,6]. For the past ten years, Fl has been in the focus of chemical studies, yet its chemical character is not clear. Results obtained at FLNR Dubna [7] and at GSI [8] were interpreted to point at a noble-gas-like and a metallic character, respectively. In the course to settling the question, the safe identification of its nuclear decay chains has proven to be difficult [4]. As was demonstrated [8,9], the coupling of chemistry setups to an electromagnetic separator provides the necessary suppression of the primary beam and of the products of multi-nucleon transfer reactions, and thus a gain in sensitivity for the unambiguous identification of single atoms of the heaviest elements. This facilitates studies of chemical properties and even of the exploration of nuclear properties of superheavy elements in chemistry experiments [9].
At GSI Darmstadt, the gas filled TransActinide Separator and Chemistry Apparatus (TASCA) serving as a physical preseparator, along with its ancillary systems including the Cryo-Online Multidetector for Physics and Chemistry of Transactinides (COMPACT) and its upgraded version miniCOMPACT [6,11] have been used continuously improved during the last decade, e.g. [8,10]. The current focus of the superheavy element chemistry experiments behind TASCA is on nihonium, flerovium, and moscovium, using isotopes with half-lives down to 0.2 s. At the conference, further experimental data on Fl as well as first data on Mc and its daughter Nh gained more recently at GSI Darmstadt will be discussed. To progress to the next heavier element, livermorium (Lv, element 116), developments towards a faster technique based on electrical field guidance rather than gas-flow extraction to transport the species of interest to the gas chromatography and detection system have started [11]. Preparatory experiments were performed at Texas A&M University and at GSI Darmstadt and show the path forward to chemical studies of yet heavier elements.
References:
[1] Keller OL et al. (1970) J. Phys. Chem. 74:1127; Pitzer KS (1975) J. Chem. Phys. 63:1032.
[2] Pershina V (2019) Radiochim. Acta 107:833; Trombach L et al. (2019) PCCP 21:18048.
[3] Türler A and Pershina V (2013) Chem. Rev. 113:1237.
[4] Türler A et al. (2015) Nucl. Phys. A 944:640.
[5] Eichler R et al. (2008) Angew. Chem. Int. Ed. 47:3262.
[6] Yakushev A et al. (2021) Front. Chem. 9:753738.
[7] Eichler R et al. (2010) Radiochim. Acta 98:133.
[8] Yakushev A et al. (2014) Inorg. Chem. 53:1624; Düllmann ChE et al. (2022) Radiochim. Acta 110:417
[9] Even J et al. (2014) Science 345:1491; Even J et al. (2015) J. Radioanal. Nucl. Chem. 303:2457.
[10] Lens L et al. (2018) Radiochim. Acta 106:949.
[11] Götz S et al. (2021) Nucl. Instrum. Meth. B 507:27.Speaker: Christoph Duellmann (JGU Mainz / GSI Darmstadt / HIM Mainz)
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Neutron Rich III: Plenary Sundial I and II
Sundial I and II
Sundial Beach Resort
1451 Middle Gulf Drive Sanibel, FL 33957-
08:30
Studies of Weakly-Bound, Neutron-Rich Nuclei using SOLARIS* 25m
The availability of intense (>105 pps) beams of long-lived radioisotopes at energies just above the Coulomb barrier at the ReA facility at the National Superconducting Cyclotron Laboratory, and the newly implemented SOLARIS spectrometer led to a 2021 campaign of experiments to study varied aspects of nuclear structure in neutron-rich nuclei.
The N = 18 nucleus, 32Si, has single-neutron excitations in the f7/2, p3/2, and p1/2 orbitals; however, their binding energies are unknown. The neutron-adding (d,p) reaction selectively populates these excitations. Using SOLARIS and a 32Si beam from ReA, the energies and single-particle strength of these excitations have been determined. These data inform a global picture of f and p excitations in nuclei with N = 16, 18, and 20 (plus a neutron) as these excitations move toward the weak binding limit and the island of inversion.
A further experiment revisited the classic study of the 10Be(t,p)12Be reaction, but in inverse kinematics. A complete description of the structure of 12Be remains elusive. At higher beam energy and with the advantages of detecting recoils of both 12Be and 10,11Be populated in reactions above one and two neutron separation energies, the solenoidal-spectrometer technique reveals new insights into the structure of 12Be. A brief overview of the SOLARIS spectrometer and the 2021 campaign will accompany the discussion of these new results.
*This material is based upon work supported by NSF’s National Superconducting Cyclotron Laboratory, which is a major facility fully funded by the National Science Foundation under award PHY-1565546; the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract Number DE-AC02-06CH11357 (Argonne) and Award Number DE-SC0014552 (UConn); the Spanish Ministerio de Econom ́ıa y Competitividad through the Programmes “Ram ́on y Cajal” with the grant number RYC2019-028438-I; the U. K. Science and Technology Facilities Council (Grant No. ST/P004423/1); and the International Technology Center Pacific (ITC-PAC) under Contract No. FA520919PA138. SOLARIS is funded by the DOE Office of Science under the FRIB Cooperative Agreement DE-SC0000661. The isotopes used in this research were supplied by the U.S. Department of Energy Isotope Program, managed by the Office of Isotope R&D and Production, and by the Paul Scherrer Institute, Switzerland.
Speaker: Benjamin Kay (Argonne National Laboratory) -
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Knockout Reactions to Study Neutron-Rich Nuclei 25mSpeaker: Heather Crawford (Lawrence Berkeley National Laboratory)
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The Surprising Structure of 40Mg 25mSpeaker: Takaharu Otsuka (University of Tokyo)
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Studies On Multinucleon Transfer Reactions As An Alternative Method For Superheavy Elements Creation. 25m
Searching for superheavy elements (SHE) has been the subject of research for many years. At this time all discovered SHE were produced in the complete fusion reaction. It is expected that the cross-section for the new SHE production is on the order of tens of femto barns. That, together with technical barriers, like the need for high-intensity beams and suitably thick targets, creates a limitation for the complete fusion technique to be used in further research.
The aim of this presentation is to introduce a possible alternative experimental technique of SHE production, the multinucleon transfer method (MNT). This method besides less strict conditions for the reaction to take place also opens the possibility of neutron-rich nuclei creation, which allows to study it in respect of creating both short- (with a lifetime of the order of ns) and long-lived (with a lifetime of order the of years) nuclei. It is a valuable asset in terms of reaching an island of stability.
Studies of the MNT reactions at the Cyclotron Institute at TAMU have a long history [1-6]. In most recent experiments, the MNT mechanism was studied on several reactions, including 197Au+232Th (7.5 A.MeV) and 197Au+197Au (8.63 A.MeV). All experiments were focused on searching α decay chains (with at least 2 α particles in one 2 μs - long time window). Experiments were conducted on a dedicated detector setup, which was using silicon and YAP detecting modules. Results obtained from the analysis of the collected during these experiments data will be presented.
Acknowledgment for the entire SJY group for active involvement in all experiments. This research is supported by the United States Department of Energy under Grant DE-FG02-93ER40773.
1. Z. Majka, et al. Acta Phys. Pol B, 45, No. 2:279, 2014.
2. A. Wieloch, et. al. EPJ Web of Conferences, 117, 2016.
3. Z. Majka, et. al. Acta Phys. Pol. B, 49, No. 10:1801, 2018
4. S. Wuenschel, et. al. Phys. Rev. C 97, 064602
5. K. Zelga PHD dissertation, Jagiellonian University, 2020.
6. K. Zelga, et. al. Acta Phys. Pol. B 50, 579, 2019Speaker: Dr Kamila Zelga (Cyclotron Institute, Texas A&M University) -
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Investigation of Neutron-Rich, Rare-Earth Nuclei* 25m
A program of study has been ongoing at Argonne National Laboratory to investigate
nuclei in the neutron-rich, rare-earth region through various experimental methods. The motivation of this work is to 1) deliver relevant information (masses and lifetimes) of isotopes that may help nuclear astrophysicists better understand the Rare-Earth Peak (REP) found in the mass abundance distribution and 2) explore nuclear structure effects (such as deformed subshell gaps and the presence of isomers) as the systems become more neutron rich. The combination of the CARIBU source with the Canadian Penning Trap has produced many new masses of ground states, as well as of long-lived isomers. The presence of these isomers has led to subsequent beta-decay experiments, utilizing the CARIBU source, in order to measure the half lives as well as to explore the excited levels in the daughter nuclei. In fact, high-spin, beta-decaying isomers found in some of the odd-odd nuclei have led to the population of some intriguing states in the even-even daughter nuclei. Finally, multinucleon transfer reactions can also produce neutron-rich isotopes that cannot come from sources. Evidence of a Z = 60 deformed subshell gap will be presented based on work from a 160Gd beam bombarding a 154Sm target at an energy just above the Coulomb barrier.*Acknowledgments: This work is funded by the National Science Foundation under
Grants No. PHY-1907409 (USNA) & No. PHY-0754674 (FSU), the US Department of
Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357 (ANL),
DE-FG02-97ER41041 (UNC), DE-FG02-97ER41033 (TUNL), as well as the UK
Science and Technology Facilities Council. This research used resources of Argonne National Laboratory’s ATLAS facility, which is a DOE Office of Science User Facility.Speaker: Daryl Hartley (US Naval Academy)
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Fission VI: Invited Sundial I and II
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Uncertainty quantification for fission fragment initial conditions 25m
Uncertainty quantification has been growing in prominence over the last several years, especially in a range of nuclear theory communities, from ab initio to phenomenological models and effective field theories to density functional theories. Most of this uncertainty quantification has been focused on parametric uncertainties that arise from fitting to experimental data and how these uncertainties propagate through models, but investigations are also underway to understand the impact of model truncation, model forms, and the type of data included in the optimization. While many applications are updating their uncertainty quantification from 2 minimization and covariance propagation to a full Bayesian Monte Carlo, the computational cost of this method can make this type of analysis prohibitively expensive for large-scale models.
One such model is the Monte Carlo, Hauser-Feshbach fission fragment decay code, CGMF, developed at LANL [1]. CGMF calculates the emission of prompt neutrons and rays on an event-by-event basis, conserving energy, momentum, spin, and parity with each emission. To perform the Hauser-Feshbach decay, information about the fission fragment is needed, namely initial distributions in mass, charge, total kinetic energy, spin, and parity. Although there is a wealth of research into microscopic and microscopic-macroscopic calculations of these initial conditions, typically, the distributions are parametrized and fit to experimental data, either directly or indirectly. This procedure has been used to fit the fission fragment initial conditions in the released version of CGMF. The challenge with this procedure is that much of the data that are needed to constrain the fission fragment initial conditions are reconstructed from measured observables after prompt neutron and -ray emission, and the reconstruction is often based on calculations. Therefore, it is particularly important to include well-quantified uncertainties on the model calculations. In this work, we show our first studies to construct parametric uncertainties on the fission fragment initial conditions and their propagation to prompt fission observables.
LA-UR-22-27617
*This work was performed under the auspice of the U.S. Department of Energy by Los Alamos National Laboratory under Contract 89233218CNA000001 and was supported by the Laboratory Directed Research and Development program of Los Alamos National Laboratory.
- P. Talou, et al., Comp. Phys. Commun. 269, 108087 (2021).
Speaker: Amy Lovell (Los Alamos National Laboratory) -
11:30
Neural Networks as Emulators for DFT Calculations 20m
Neural Networks as Emulators for DFT Calculations
Daniel Lay${}^{1,2}$, Eric Flynn${}^{1,2}$, Samuel Giuliani$^3$, Witold Nazarewicz$^{1,2}$, Leo Neufcourt$^1$
$^1$Facility for Rare Isotope Beams, Michigan State University, East Lansing, Michigan 48824, USA.
$^2$Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA.
$^3$Department of Theoretical Physics, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
Fission lifetimes and fragment yields are important inputs to properly modeling r-process nucleosynthesis [1]. Fission is well described using the framework of nuclear density functional theory (DFT) [2]. In DFT, we treat fission as a tunneling problem in the collective space, first by constructing the energy as a function of the collective coordinates (the potential energy surface, PES), and then finding the least action path(s) using the WKB approximation [3,4,5]. Due to the number of DFT calculations required to construct the PES, carrying out DFT studies for all nuclei in the relevant region of the nuclear chart is prohibitively expensive. To that end, we have studied the use of neural networks as an emulator for the PES. We find that the difference between the DFT energy and the emulated energy is typically below 1 MeV, and even lower in the regions of the PES relevant for fission. We also compare the least action path(s) found using both surfaces, and find general agreement between them.
This work was supported by the U.S. Department of Energy under Award Numbers DOE-DE-NA0004074 (NNSA, the Stewardship Science Academic Alliances program). This work has been supported by the “María Zambrano” Grant No. CA3/RSUE/2021-00423 from the UAM financed by the Spanish Ministry of Universities and the “European Union NextGenerationEU” program; and by the MINECO Grant No. PGC2018-094583-B-I00.
[1] S. A. Giuliani et al. “Fission and the r-process nucleosynthesis of translead nuclei in neutron star mergers,” Phys. Rev. C 102, 045804 (2020).
[2] M. Bender, P.-H. Heenen, and P.-G. Reinhard, “Self-consistent mean-field models for nuclear structure,” Rev. Mod. Phys. 75, 121–180 (2003).
[3] P. L. Kapur and R. Peierls, “Penetration into potential barriers in several dimensions,” Proc. R. Soc. A 163, 606–610 (1937).
[4] N. Schunck and L. M. Robledo, “Microscopic theory of nuclear fission: a review,” Rep. Prog. Phys. 79, 116301 (2016).
[5] J. Sadhukhan, S.A. Giuliani, Z. Matheson, and W. Nazarewicz, “Efficient method for estimation of fission fragment yields of r-process nuclei,” Phys. Rev. C 101, 065803 (2020).
Speaker: Daniel Lay (Michigan State University/FRIB) -
11:50
Dynamics of Fission Pathways 20m
While the importance of nuclear fission as a many-body decay process is well-established, a full understanding of the myriad pathways explored by fissioning systems has remained elusive. Each of these pathways explored by the compound nuclei can result in vast differences in the fission products and directly influences the charge, masses, energies, and angular momenta of the outgoing fragments. In this talk we discuss both a constrained Hartree-Fock-Bogoliubov approach to exploring the (potentially many) discrete pathways through multidimensional collective spaces [1] as well as a real-time approach to exploring asymmetric fission channels via time-dependent density functional theory [2]. Through these complementary approaches we explore briefly the impact on fission lifetimes and fragment production, discuss potential next steps for the study of fission pathways, and attempt to obtain a deeper insight into the complex many-body dynamics of nuclear fission.
This work was supported by the U.S. Department of Energy under Award Nos. DE-NA0004074 (NNSA, the Stewardship Science Academic Alliances program), DE-SC0013365 (Office of Science), DE-SC0018083 (Office of Science, NUCLEI SciDAC-4 Collaboration), DE-SC0013847 (Office of Science) and the Australian Research Council Discovery Project (project number DP190100256).
- E. Flynn, D. Lay, S. Agbemava, P. Giuliani, K. Godbey, W. Nazarewicz, and J. Sadhukhan, Phys. Rev. C 105, 054302 (2022).
- C. Simenel, P. McGlynn, A.S. Umar, and K. Godbey, Phys. Lett. B 822, 136648 (2021).
Speaker: Dr Kyle Godbey (FRIB) -
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Total kinetic energy release in the fast neutron induced fission of actinide nuclei 20m
Over 80 % of the energy release in fission is in the form of the kinetic energy of the fission fragments. We have used the LANSCE facility at Los Alamos to measure the total kinetic energy release in the fast neutron (En=1-100 MeV) fission of 232Th[1], 235U[2], 237Np[3], 239Pu[4], 240Pu, and 242Pu. The neutron energies were deduced from time of flight measurements and the fragment energies were measured using arrays of Si detectors. Vapor deposited targets were used to lessen impurities in the targets and to provide thin, uniform actinide deposits. Corrections were made to the data for the pulse height defect and the fragment energy loss in the target and its backing.
The resulting TKE distributions were Gaussian in shape and could be fitted with 2nd order polynomials. Comparisons of the variation of the TKE with increases in neutron energy for all the systems studied revealed similar patterns for each system with small offsets between the systems.
The variation of the TKE with neutron energy was compared to the GEF, CGMF and other models. The measurements reported herein agreed (within uncertainties) with other measurements. The dependence of the TKE upon neutron energy is similar for all systems studied and in general agreement with the GEF model. Comparisons were also made, where possible, with the predictions of the CGMF model. Comparisons of the deduced fragment masses with these models were also made.
*We gratefully acknowledge the financial support of the Stockpile Stewardship Academic Alliance, the U.S. Dept of Energy, Office of Nuclear Physics and the Lawrence Livermore National Laboratory
1. J. King, et al., Eur. Phys. J. A 53, 238 (2017)
2. R. Yanez et al., Nucl. Phys. A 970, 65 (2018)
3. A. Pica et al., Phys. Rev. C 102, 064612 (2020)
3. A. Chemey, Eur. Phys. J. A. 56, 297 (2020).Speaker: Walter Loveland (Oregon State University) -
12:30
Fully microscopic description of odd-mass fissioning systems 20m
The nuclear fission process has been known for over eighty years, yet its description in a consistent theoretical framework is still lacking. Fully microscopic descriptions of the fission process are a promising route that allows us to build a theory of fission directly related to in-medium nuclear forces. So far, microscopic methods have been applied exclusively on even-even isotopes due to the simplifications enabled by the time-reversal symmetry. For the first time, we have extended the theoretical framework to describe odd-mass nuclei. To validate our approach, we computed the time evolution of the shape deformation of fissioning nuclei using the time-dependent generator coordinate method with the Gaussian overlap approximation (TDGCM+GOA) in the isotopic chain $^{236,237,238,239}$U. We extracted the fission-fragment mass and charge distributions before neutron and gamma evaporation. We used these initial distributions as inputs to the statistical deexcitation code FREYA and extracted the independent and cumulative fission product yields for these isotopes.
Acknowledgements This work was supported in part by the NUCLEI SciDAC-4 collaboration DE-SC001822 and was performed under the auspices of the U.S.\ Department of Energy by Lawrence Livermore National Laboratory (LLNL) under Contract DE-AC52-07NA27344.
LLNL-ABS-836803
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Fission modes in the decay of 176,180Hg formed in the reactions 64,68Zn+112Sn at energies around the Coulomb barrier 20m
The study of the fission process is considered presently mostly important not only for searching pathways to synthesize new superheavy elements and to predict their stability against fission, but also for the direct impact on the understanding of the fission recycling process in r-process of nucleosynthesis. A description of the fission process with reliable predictive power is therefore needed, in particular for low-energy fission where the fission fragments mass distributions are strongly sensitive to microscopic effects. Many observations strongly support the hypothesis that nuclei may fission through several independent fission modes (multimodal fission) corresponding to different prescission shapes and fission paths in a multidimensional potential-energy landscape, in which shell effects are dominant.
Mass distributions are usually predominantly symmetric or asymmetric with the yields being single or double humped, respectively. However, in several cases a mixture of two modes is observed.
The dominance of asymmetric fission occurs in most of the actinide region beyond A = 226 up to about 256Fm and is attributed to the strong shell structure of the nascent fission fragments, near the doubly magic 132Sn. The unexpected asymmetric character of the mass distribution found in the fission of 180Hg at low excitation energy has shown the importance of studying the preactinide region and has triggered the interest of studying neighboring isotopes. In particular, a new contiguous region of asymmetric fission separated from the classical location of asymmetric fission in the actinides by an extended area of symmetric fission has been predicted.
In such a framework, we will propose our study on the nuclei 176,180Hg. Binary fission fragments formed in the reactions 64,68Zn + 112Sn 176,180Hg at different excitation energies around the Coulomb barrier were detected using the double-arm time-of-flight technique using the spectrometer CORSET. The experiment was performed at JYFL (Jyvaskyla, Finland). We will present an analysis of the Mass-TKE distributions in terms of fission modes.Speaker: Prof. Emanuele Vardaci (University of Naples "Federico II" and INFN)
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Theory of Barrier-Top Dynamics in Fission 25m
During the last several years we have been developing models and computational tools to describe low-energy fission in a configuration-interaction representation. The approach can be viewed as a generalization of the Generator Coordinate Method that allows many configurations to contribute to the dynamics but avoids the construction of a many-dimensional Schroedinger equation. The main physical ingredients of the theory are: the fission path and its potential energy surface, the level densities of reference configurations along the PES, and the residual interactions between the nucleons in their orbitals. In the past we have constructed simple models in this scheme to make contact with the traditional transition-state dynamics [1] and to test the reliability of a number of assumptions that are commonly made. These include the adiabatic approximation for spontaneous fission[2], the neglect of configurations not active in the dynamic evolution[1], and the assumed validity of the standard Porter-Thomas formula for width fluctuations[3].
We report here our first results applying the theory to more realistic Hamiltonians, focusing on the fission reaction 235-U(n,f) induced by low-energy neutrons.
The single-particle properties of the configurations are taken from deformed
Woods-Saxon or Gogny treatments of the mean-field Hamiltonians. The nucleon-nucleon interactions are taken from the pairing systematics and calculated diabatic interactions. We believe the theory is sufficiently realistic to calculate the energy dependence of the transmission coefficient that can be compared with the standard parameterization in the fission data literature[4]. The main physical property we calculate in this work is the fission/capture branching ratio.- G.F. Bertsch and K. Hagino, J. Phys. Soc. Japan 90 114005 (2021).
- K. Hagino and G.F. Bertsch, Phys. Rev. C 102 024316 (2020).
- K. Hagino and G.F. Bertsch, Phys. Rev. E 104 L052104 (2021).
- R. Capote, et al., Nuclear Data Sheets 110 3107 (2009).
Speaker: Prof. George Bertsch (University of Washington) -
14:55
Shell effects in quasifission and implications for fission 25m
Quasifission reactions have been of great interest in recent years particularly in connections with the formation of superheavy elements and a source for producing neutron rich nuclei. Such reactions proceed through regions of periodic table where the dynamical evolution of quantal shell effects influence the formation of final fragments. The time-dependent density functional theory (TDDFT) has been found to be an excellent theoretical tool to study these reactions microscopically [1-5]. In this talk we discuss the recent results for quasifission reactions obtained using the TDDFT. In, particular we focus on the observed shell effects in these calculations and their relevance and/or relationship for shell effects in fission dynamics.
- C. Simenel, P. McGlynn, A.S. Umar, and K. Godbey, Phys. Lett. B 822, 136648 (2021)
- C. Simenel and A. S. Umar, Prog. Part. Nucl. Phys. 103, 19 (2018)
- C. Simenel, K. Godbey, and A. S. Umar, Phys. Rev. Lett. 124,
212504 (2020) - K. Godbey, C. Simenel, and A. S. Umar, Phys. Rev. C 101, 034602 (2020)
- K. Godbey, A. S. Umar, and C. Simenel, Phys. Rev. C 100, 024610 (2019)
Speaker: Prof. Sait Umar (Vanderbilt University) -
15:20
Towards a Langevin Model for the Stochastic Dynamics of Nuclear Fission 20m
A robust description of the process of nuclear fission is essential to many research domains ranging from nuclear energy, national security, and nuclear data. However, owing to the nuclear many-body problem, a description of fission based on nucleon-nucleon interactions is unfeasible given current computational limitations, which has led to a number of alternative methods that greatly reduce the overall complexity of this difficult problem. In this work, we present results of recent efforts to model the process of nuclear fission from the perspective of a microscopic-macroscopic model of the atomic nucleus, where fission proceeds from an initially excited state to scission as a stochastic process according to a progression of increasingly sophisticated treatments of the stochastic dynamics. In contrast with our past work, which has treated fission in the strongly-damped limit described by a random-walk process, this approach furnishes the kinetic energies associated with the nascent fragments, which is subsequently used to model the de-excitation properties of fission fragments.
Speaker: Trevor Sprouse (Los Alamos National Laboratory) -
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Study of abrasion-fission mechanism at intermediate energies in the context of drip-line search 20m
The availability of heavy-ion beams at high-intensity, coupled to sensitive, large solid-angle acceptance spectrometers has enabled a detailed examination of the reaction residues produced in induced-fission reactions. Fission fragment production was studied using a uranium beam provided by the Coupled Cyclotron Facility (CCF) at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. The uranium beam was extracted from the K1200 cyclotron with an energy E = 80 MeV/u, and was delivered directly to the production target located at the pivot point of the S800 magnetic spectrograph [1]. Cross sections were obtained following yield measurements performed for the principal charge states of the identified fission fragments and a detailed analysis of the ion transmission. A full kinematic analysis of the fission fragments has been performed using the LISE++ software package [2,3], where the trajectory of an ion passing through the spectrometer can be reconstructed based upon measurements at the focal plane. Results compare favorably with predictions obtained with the LISE++ three-fission progenitor (3EER) model [4].
Deduction of fissile nuclei (fissioning projectile-like prefragments) is discussed in the context of drip-line search assuming abrasion-fission of a primary 238U beam to be a first production step to reach very neutron rich nuclei in region 25 ≤ Z ≤ 70.
This work was supported by the US National Science Foundation under Grants No. PHY-11-02511, No. PHY-15-65546, and No. PHY-20-12040.
- D. Bazin et al., Nucl. Instr. and Meth. in Phys. Res. B 204, 629 (2003).
- O.B. Tarasov and D. Bazin, Nucl. Inst. And Meth. in Phys. Res B 376, 185 (2016)
- O.B. Tarasov and D. Bazin, Nucl. Inst. And Meth. in Phys. Res B 266, 4657 (2008).
- O.B. Tarasov, Tech. Rep. MSUCL1300, NSCL, Michigan State,
https://lise.nscl.msu.edu/7_5/lise++_7_5.pdf
Speaker: Dr Oleg B. Tarasov (FRIB / MSU)
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Radioactive Beams with the New TriSol Separator* 25m
The production of beams of radioactive nuclei has resulted in opportunities for addressing many open questions in nuclear structure, nuclear astrophysics, and fundamental symmetries. For over three decades, the TwinSol separator at the University of Notre Dame has produced high-quality in-flight radioactive beams of both proton-rich and neutron-rich nuclei [1]. The TwinSol separator was recently upgraded by adding additional elements: a dipole magnet, and a third solenoid. This new TriSol separator will improve the quality and purity of future radioactive beams. This improvement will enable the use of heavier beams and address beam contamination that has hindered past experiments. The current status and capabilities of TriSol and the first experiments using the upgraded device will be presented.
*Work supported in part by the National Science foundation and the University of Notre Dame.
[1] M. Y. Lee et al., TwinSol: A dual superconducting solenoid system for low-energy radioactive nuclear beam research, AIP Conf. Proc. 392 (1997) 397-400. doi:10.1063/1.52712.
Speaker: Dan Bardayan (University of Notre Dame) -
14:55
The NEXT step to the neutron-rich side 25m
Neutron-rich, heavy, EXotic nuclei around the neutron shell closure at N=126 and in the transfermium region are accessible via multinucleon Transfer reactions which feature relative high cross-sections. However, the wide angular distributions of the multinucleon transfer products lead to experimental challenges in the separation and identification of the transfer products.
In order to overcome these obstacles, we are building the NEXT experiment [1] at the AGOR facility in Groningen. The AGOR cyclotron is capable to deliver high intense heavy ion beams at energies suited for transfer reactions. The production target for the transfer reactions is placed inside a 3-T solenoid magnet. The bore of the solenoid is 157-cm long and 86-cm wide. Within this volume the transfer products are separated according to their magnetic rigidities. We developed a Python code to optimize the layout of the solenoid separator for highest ion transmission and background suppression based on two model reactions Xe-136 +Pt-198 and Ca-48 +Cf-251. The isotopes of interest are focused by the magnet onto a gas catcher where they are slowed down. From the gas catcher the ions are transferred and bunched by a newly developed stacked-ring ion guide [2] into a Multi-Reflection Time-of-Flight Mass Spectrometer (MR-ToF MS) [3]. The MR-ToF MS provides isobaric separation and allows for precision mass measurements. Thus, background free spectroscopy will be feasible.
In the contribution, I will present an overview of the NEXT setup, its current status and the planned experimental program.[1] J. Even, X. Chen, A. Soylu, P. Fischer, A. Karpov, V. Saiko, J. Saren, M. Schlaich, T. Schlathölter, L. Schweikhard, J. Uusitalo, and F. Wienholtz, The NEXT Project: Towards Production and Investigation of Neutron-Rich Heavy Nuclides, Atoms 10, 59 (2022).
[2] X. Chen, J. Even, P. Fischer, M. Schlaich, T. Schlathölter, L. Schweikhard, and A. Soylu, Stacked-Ring Ion Guide for Cooling and Bunching Rare Isotopes, Int. J. Mass Spectrom. 477, 116856 (2022).
[3] M. Schlaich, Development and Characterization of a Multi-Reflection Time-of-Flight Mass Spectrometer for the Offline Ion Source of PUMA, Master’s thesis, Technische Universität Darmstadt, (2021).Speaker: Julia Even (University of Groningen) -
15:20
Neutron inelastic scattering on 238U with GENESIS at LBNL 20m
A better understanding of neutron inelastic scattering on fissioning isotopes is crucial due to their broad use in applications. Inaccuracies between previously measured experimental data [1,2,3] and the theoretical approaches of the inelastic channel may lead to inadequate reliability in the models. Our goal is to improve the $^{238}$U(n, n'γ) cross-section via neutron-γ coincidences using the Gamma Energy Neutron Energy Spectrometer for Inelastic Scattering (GENESIS) at Lawrence Berkeley National Laboratory’s (LBNL) 88-Inch Cyclotron. GENESIS provides the unique capability of measuring correlated neutron and high-resolution γ-ray data while simultaneously measuring the neutron energy and flux. Through the excitation distribution of the neutrons, we look into the consistency of the results with previous γ-ray measurements, highlighting actual γ-ray cascade issues, involving both discrete and quasi-continuum states. Initial results of $^{238}$U(n, n’γ) will be presented, confirming the promising avenue of neutron-γ coincidences for neutron inelastic cross-section measurements.
This work has been performed under the auspices of the U.S. Department of Energy by Lawrence Berkeley National Laboratory under contract No. DE-AC02-05CH1123 and Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.
1. D. K. Olsen et al., Conf. on Nucl. Cross Sections F. Techn. (Knoxville 1979)
2. N. Fotiades et al., Phys. Rev. C 69, 024601 (2004)
3. A. Hutcheson et al. Phys. Rev. C 80, 014603 (2009)Speaker: Anastasia Georgiadou (University of California – Berkeley Department of Nuclear Engineering, Berkeley, CA 94709, USA) -
15:40
Probing binding energy and size of hypertriton with heavy ion collisions 20m
The hypertriton is predicted to have a small binding energy (a weighted average of 170 keV), consistent with a large matter radius (~ 10 fm) and similar to historical 11Li halo discovered more than 35 years ago. But the experimental values of the binding energy of the hypertriton range from 50 to 500 keV. In this work I discuss the electromagnetic response and interaction radius of the hypertriton and how high energy heavy ion collisions (~ 1 - 2 GeV/nucleon) can help achieving a higher accuracy for the determination of its binding energy.
Speaker: Prof. Carlos Bertulani (Texas A&M University-Commerce)
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The NIFFTE fission Time Projection Chamber 25m
The goal of the Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) is to measure fission cross sections with unprecedented precision. The tracking capabilities of this device allow for the full reconstruction of charged particles produced by neutron beam induced fission from a thin central target. The wealth of information gained from this approach allowed cross section systematics to be studied in detail and allowed for a variety of other measurements to be performed. Here we present a brief history of this unique instrument and a variety of results including fission anisotropy, linear momentum transfer, independent elemental fission product yields, and fission cross sections.
Speaker: Lucas Snyder (LLNL) -
16:55
Measuring the 235U(n,f)/6Li(n,t) cross section ratio in the NIFFTE fissionTPC 20m
Neutron-induced reactions are important to our understanding of fundamental nuclear physics as well as nuclear applications. Due to their impact on a wide range of nuclear physics applications, it has become important to better understand the probability such reactions occur and try to minimize their uncertainties. In particular, there is a need for precision neutron-induced fission cross section measurements on actinides. Neutron-induced fission cross sections are typically measured as ratios, relative to a well-known cross section standard. The $^{235}$U(n,f) is a well measured standard, often used as a reference on cross section ratio measurements of other actinides. However, some light particle reactions are also well-known and their use as reference can provide information to remove shared systematic uncertainties that are present in an actinide-only ratio measurement. The NIFFTE collaboration's fission time projection chamber (fissionTPC) is a charged particle tracker designed for precision measurements of neutron-induced fission reactions. Detailed 3D track reconstruction of the reaction products enables evaluation of systematic effects and corresponding uncertainties which are less directly accessible by other measurement techniques. This work focuses on the recent measurement of the $^{235}$U(n,f) using as a reference the light-ion standard $^6$Li(n,t) reaction. Preliminary data of the $^{235}$U(n,f)/$^6$Li(n,t) measurement conducted at the Los Alamos Neutron Science Center will be presented.
LLNL-ABS-836692: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Speakers: Dr Maria Anastasiou (Lawrence Livermore National Laboratory), NIFFTE Collaboration -
17:15
Measurement of the 233U capture to fission ratio at LANSCE 20m
Uranium-233 has played an important role in critical assembly experiments going back to the 50's and 60's, including experiments from the Falstaff Program. The thorium fuel cycle has been proposed as an alternative to the uranium fuel cycle due to its reduced amount of transuranium elements. $^{232}$Th is more abundant in nature than uranium, and decays in the thorium fuel cycle into the fissile isotope $^{233}$U producing a large number of neutrons, enough to maintain the chain reaction. For this reason, the thorium fuel cycle may be used for thermal breeder reactors and fast reactors.
Quality nuclear data are needed to study the neutron-induced reactions on this isotope. The experimental $^{233}$U(n,γ) cross section data available in the literature are scarce and were measured decades ago. An accurate measurement of the $^{233}$U(n,γ) cross section is required by the NCSP (Nuclear Criticality Safety Program) to complete the neutron-induced cross section data. Measurements of the $^{233}$U(n,γ) reaction data were made in 2020 and 2021 at the Los Alamos Neutron Science Center (LANSCE) at Los Alamos National Laboratory (LANL) using the Detector for Advanced Neutron Capture Experiments (DANCE) combined with the NEUtron detector array at dANCE (NEUANCE).
Because $^{233}$U fission is around one order of magnitude more likely than capture, an accurate measurement of the $^{233}$U capture cross section relies on the discrimination between the gammas produced in capture and fission reactions. In this measurement, NEUANCE tagged fission neutrons while DANCE detected both capture and fission gammas. Coincidences between NEUANCE and DANCE are reconstructed during analysis.
This measurement will provide the capture to fission ratio, reducing the uncertainties with respect to an absolute measurement of the cross section by eliminating experimental complications like self-absorption, beam/target overlap and non-uniformities. In this talk, I will discuss the new $^{233}$U capture to fission ratio result in addition to the measurement technique, the DANCE and NEUANCE detector system for capture and fission measurements, and potential other applications of the instruments.
Speaker: Esther Leal Cidoncha (LANL) -
17:35
Study of Prompt Photofission Neutrons from Several Actinides 20m
The multiplicity and energy spectra of prompt fission neutrons from photofission of
235U, 238U, and 239Pu were measured with 13.5 MeV incident photons.
Measurements were taken with a 1 m flight path and a relatively sparse array of
BC501A/EJ301 scintillators such that multiple scattering effects between detectors were
minimal. The targets were mounted in ionization chambers to tag fission events. Data
and related GEANT4 simulation results will be presented.
This work is supported in part by the NNSA under grant No. DE-NA0003887 and by the
US department of energy under grant No. DE-FG02-97ER41033.Speaker: F.Q.L Friesen (Triangle Universities Nuclear Laboratory, Duke University)
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10 Years of ORNL Modular Total Absorption Spectroscopy 25m
The Modular Total Absorption Spectrometer (MTAS) [1] was built and commissioned at Oak Ridge National Laboratory just over ten years ago. In the decade since, many experiments that impact a wide range of fundamental and applied physics topics have been reported with MTAS [2-6].
MTAS is a NaI based detector array made of 19 different modules with a total mass of about 1 ton and an almost 4pi solid angle coverage. The total efficiency of MTAS is near 99% with peak efficiencies of over 80% for 1 MeV gamma rays. This high efficiency detector array was designed for and can be used to identify complex beta-decay feeding patterns of neutron-rich fission products. In addition MTAS is capable of identifying other decay channels of neutron-rich fission products such as direct to ground-state decay branches and beta-delayed neutron emission branches. Precise knowledge of beta-decay feeding patterns impacts many aspects of reactor based physics, such as accurately modeling reactor decay heat and simulating reactors as an antineutrino source for fundamental physics.Selected MTAS results from over the last decade and their impacts will be presented.
ORNL co-authors were supported by the U.S. DOE Office of Nuclear Physics under DOE Contract No. DE-AC05-00OR22725 with UT Battelle, LLC.
[1] M. Karny, et al., Nuclear Instruments and Methods A, 836 (2016)
[2] B.C. Rasco, et al., Phys. Rev. Lett., 117 (2016)
[3] A. Fijalkowska, et al., Phys. Rev. Lett., 119 (2017)
[4] B.C. Rasco, et al., Phys. Rev.C, 95 (2017)
[5] P. Shuai, et al., Phys. Rev.C, 105 (2022)
[6] B.C. Rasco, et al., Phys. Rev.C, 105 (2022)Speaker: Dr Bertis Rasco (ORNL) -
16:55
The decay of 133In, a rosetta stone for the r-process nuclei 20m
Studying the $\beta$ decay of indium-133 is of great significance for both nuclear structure and astrophysics. On one hand, $^{133}$In is a perfect $\beta$-decay demonstrator of $r$-process nuclei in the vicinity of $N=82$ owing to its extreme neutron-proton asymmetry and thus large Q$_\beta$ windows. On the other hand, its decay daughter, $^{133}$Sn, is simple in its structure due to its proximity to the doubly magic $^{132}$Sn. Thus, a measurement of the $\beta$-strength function of $^{133}$In unravels extensive details on how the $r$-process nuclei decay, benchmarking the state-of-the-art nuclear models with a simple representation. This is extremely crucial for the nuclear models in evaluating their prediction power in more exotic regions that are out of experimental reach.
The experiment was conducted at the ISOLDE decay station (IDS). The new neutron time-of-flight array, INDIe [1-3], was built at IDS to measure neutron emissions from the neutron unbound states in $^{133}$Sn following the $^{133}$In $\beta$ decay. Several strong and isolated neutron resonances were observed below Ex=6 MeV, including the previously observed state at Ex=3.56 MeV [4-6]. More importantly, we quantified precisely the single GT strength of the $\nu$g$_{7/2}\rightarrow\pi$g$_{9/2}$ transformation which dominates the $\beta$ decay of a large number of exotic nuclei to the southeast of $^{132}$Sn. In this contribution, we will present our latest results regarding the excitation energies, branching ratios, and log$ft$ of a series of neutron unbound states newly observed in the $^{133}$Sn. Our experimental findings were compared to the large-scale shell-model calculations involving several different effective nucleon-nucleon potentials, such as N3LO [7] and VMU [8]. The comparison suggests the proton excitation across the $Z=50$ shell gap plays an important role to understand the GT strength quantitatively in this region.
[1] W.A. Peters et al., Nucl. Inst. Meth. A 836, 122 (2016).
[2] S.V. Paulauskas et al., Nucl. Inst. Meth. A 737, 22 (2014).
[3] R. Lica et al., in preparation.
[4] P. Hoff et al., Phys. Rev. Lett. 77, 1020 (1996).
[5] V. Vaquero et al., Phys. Rev. Lett. 118, 202502 (2017).
[6] M. Piersa et al., Phys. Rev. C 99, 024304 (2019).
[7] D.R. Entem, et al., Phys. Rev. C 68, 041001 (2003).
[8] T. Otsuka et al., Phys. Rev. Lett. 104, 012501 (2010).Speaker: Dr Zhengyu Xu (University of Tennessee, Knoxville) -
17:15
Beta- decay of exotic P, S and Cl isotopes around N=28 with Tz from 11/2 to 7 20m
Phosphorus, Sulphur and Chlorine isotopes with neutron number around 28 belong to a region of deformation and shape co-existence inspite of accepted N=28 shell gap, mainly because of the quenching of the N = 28 shell gap at this high isospin and the near degeneracy of the proton “sd” s_1/2 and d_3/2 orbitals. At these extreme values of isospin, microscopic structural effects, such as the nuclear shell quenching or deformation can modify the shape of the Gamow Teller (GT) strength function affecting the beta decay properties, like half-life, beta-delayed neutron emission (P_n) and the contribution of First Forbidden (FF) transitions. To study these, beta decay of isotopes at and beyond N=28 namely, 42−44P, 43−46S and 45−47Cl, were studied following the fragmentation of 48Ca (140MeV/u) at the National Superconducting Cyclotron Laboratory using a 40x40 DSSD implant detector coupled to a clover array for detecting implants, decay events and beta-delayed gamma rays. Half-life and new level schemes have been obtained for the daughter nuclei. A systematic analysis reveals sudden jumps in the P_n values, for example, the P_n for 42P is less than 50% but for 43P we find it to be 100% but not so for 44P (T_z = 7) and significant impact of FF with explicit population of low-lying excited states in the daughter nucleus. Details of the analysis and new results will be discussed in the context of state of art shell model calculations. This work is supported by the U.S. National Science Foundation under Grant No. PHY-2012522 (FSU).
Speakers: Dr Vandana Tripathi (Department of Physics, Florida State University, Tallahassee, 32306 Florida USA), S. Bhattacharya (Department of Physics, Florida State University, Tallahassee, 32306 Florida USA) -
17:35
New isomeric transition in $^{36}$Mg: Bridging the N=20 and N=28 islands of inversion 20m
The N=20 island of inversion, so called due to the disappearance of the N=20 magic number, has consistently been one of the most exciting nuclear regions since its discovery 30 years ago. Since then, further experimental and theoretical studies have explained the origin of this anomaly from the presence of deformed two-particle two-hole components in the ground state wavefunctions of nuclei in the island of inversion. This apparently paradoxical situation for nuclei close to a magic number was resolved once nuclear interactions were derived with realistic quadrupole terms (see e.g. [1]). More recently, the observation of the first 2+ state in N=28 40Mg at low energy suggests the N=28 neutron magic number also disappears for magnesium isotopes [2]. For the magnesium isotopes in between, even though there is ample evidence of deformation [3], this can be explained without invoking quadrupole-driven "inversion", but due to the increasing occupation of the valence subshell.
The prompt gamma decay of 35 to 38 magnesium isotopes was studied at the National Superconducting Cyclotron Facility, using a 3 clover array of High Purity Germanium detectors. We observed a new isomeric gamma transition at 168 keV in 36Mg, with a half-life of T={120-500}(40)(+800)(-20) ns. We propose it corresponds to the transition between a new 0+(2) state and the previously known first 2+ state[4]. Our calculations of 36Mg using the SDPF-U-MIX interaction interpret the observed low energy of the second 0+ state due the small energy separation (pre-diagonalization) between spherical and deformed configurations. This makes 36Mg the crossing point between dominant ground state deformed/superdeformed configuration in (32,34)Mg and dominant spherical configuration in 38Mg. We conclude 36Mg bridges the N=20 and N=28 islands of inversion within the so-called Big Island of Deformation encompassing both [1].
[1] E. Caurier, F. Nowacki, and A. Poves. Phys. Rev. C 90, 7 (2014).
[2] H.L Crawaford et al., Phys. Rev. Lett. 122, 2 (2019).
[3] F. Nowacki, A. Obertelli, A. Poves, Progress in Particle and Nuclear Physics 120, 103866 (2021).
[4] A. Gade et al., Phys. Rev. Lett. 99, 8 (2007).Speaker: Miguel Madurga Flores (University of Tennessee)
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Astrophysics: Plenary Sundial I and II
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Rare Isotope Beam Factory at RIKEN 25mSpeaker: Dr Hiroyoshi Sakurai (RIKEN)
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Neutron Star Properties from LIGO and NICER Results 25mSpeaker: Carolyn Raithel (IAS / Princeton)
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The Nuclear Equation of State from Experiments and Astrophysical observations 25m
Abstract: An equation of state of nuclear matter relates states observables such as energy, pressure, temperature and density. The nuclear equation of state is important in determining the existence and properties of nuclei as well as complex astrophysical objects such as neutron stars. Even though nuclei and neutron stars differ in sizes by 18 orders of magnitude and the maximum density for each object differs by one order of magnitude, they are governed by the same equation of state. Recent advances in astrophysics observations of gravitational waves from neutron star mergers from LIGO/VIRGO as well as radii measurements from NICER allow us to combine these data with those from nuclear structure and nuclear reaction experiments. In the talk, I will present an improved understanding of the Equation of State of neutron rich matter as well as neutron star matter using Bayesian analysis applied to the combined astrophysical and terrestrial constraints. This work is supported in part by the U.S. Department of Energy (Office of Science) under Grant Nos. DESC0014530.
Speaker: Chun Yuen Tsang (Kent State University) -
09:45
GW170817, fission, and a smoking gun 25m
The GW170817b event showed the synthesis of the elements in the making by the emission of visible light. The process however went into the IR region by the time the synthesis reached Lu. The question of whether the process continued to the actinides is expected but there is no direct evidence. Fission has been studies in nuclear physics for 80 years or more but the prospect of exotic fission for very neutron rich nuclei has remained on the theoretical frame only. My talk will present a potential smoking gun for the process.
Speaker: Prof. Ani Aprahamian -
10:10
Impact of nuclear uncertainties in the r-process nucleosynthesis of heavy elements 25m
The rapid neutron capture process, or r process, is responsible for the production of about half of the elements heavier than iron found in nature, including the heaviest uranium and thorium [1, 2]. During the r process, several thousands of neutron-rich nuclei are synthesized in few seconds, powering an electromagnetic transient known as kilonova. Since most of such exotic nuclei have never been experimentally observed due to their exceedingly short half-lives, the estimation of abundances and kilonova light curves must rely upon the theoretical predictions of nuclear properties [3, 4].
During this talk, I will present calculations of nuclear properties and stellar reaction rates obtained within the energy density functional (EDF) framework. Several EDF parametrizations have been employed in order to asses the impact of systematic uncertainties in the r process nucleosynthesis. In particular, I will focus on the nucleosynthesis of translead elements in the merger of two neutron stars, and the role that nuclear masses, beta decays and fission play in shaping the r-process abundances and kilonova light curves.
This work has been supported by the “María Zambrano” Grant No. CA3/RSUE/2021-00423 from the UAM financed by the Spanish Ministry of Universities and the “European Union NextGenerationEU” program; and by the MINECO Grant No. PGC2018-094583-B-I00.
- E. M. Burbidge, G. R. Burbidge, W. A. Fowler, and F. Hoyle, Rev. Mod. Phys. 29, 547 (1957).
- A. G. W. Cameron, Publ. Astron. Soc. Pacific 69, 201 (1957).
- C. J. Horowitz, et al., J. Phys. G Nucl. Part. Phys. 46, 083001 (2019).
- J. J. Cowan, et al., Rev. Mod. Phys. 93, 015002 (2021).
Speaker: Samuel A. Giuliani (Universidad Autónoma de Madrid)
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Astrophysics Sundial I and II
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Neutron Sources for the i- and n- Process 25m
The i- and the n-process are neutron capture processes which may take place in early generation massive stars and core collapse supernova events. The neutron production by the classical neutron sources such as 13C(a,n) and 22Ne(a,n) is largely enhanced by deep convective or shockfront driven dynamic events. Depending on the initial abundance distribution, a network of neutron source may generate an intense neutron flux, driving the neutron induced reaction path beyond the range of stable isotopes. The associated abundance pattern for the i-process has been identified in early generation carbon enhanced metal poor stars, the n-process might be an alternative or complementary mechanism for the weak r-process in core collapse supernovae. This talk will focus on recent study of some of the reaction mechanisms driving the production of the high neutron flux necessary for these processes to operate.
Speaker: Michael Wiescher (University of Notre Dame) -
11:30
Understanding 22Na cosmic abundance: femtosecond lifetime measurements in 23Mg 25m
Simulations of explosive nucleosynthesis in novae predict the production of the radioisotope 22Na. Its half-life of 2.6 yr makes it a very interesting astronomical observable by allowing space and time correlations with the astrophysical object. Its gamma-ray line at 1.275 MeV has not been observed yet by the gamma-ray space observatories. This radioisotope should bring constraints on nova models. It may also help to explain abnormal 22Ne abundance observed in presolar grains and in cosmic rays. Hence accurate yields of 22Na are required. At peak nova temperatures, the main destruction reaction 22Na(p,𝛾)23Mg has been found dominated by a resonance at Er=0.204 MeV corresponding to the Ex=7.785 MeV excited state in 23Mg. However, the different measurements of the strength of this resonance disagree by more than a factor 3, see Ref. [1, 2].
An experiment was performed at GANIL facility to measure both the lifetime and the proton branching ratio of the key state at Ex=7.785 MeV. The principle of the experiment is based on the one used in Ref. [3]. With a beam energy of 4.6 MeV/u, the reaction 3He(24Mg,𝛼)23Mg* populated the state of interest. This reaction was measured with particle detectors (magnetic spectrometer VAMOS++, silicon detector SPIDER) and gamma tracking spectrometer AGATA. The expected time resolution with AGATA high space and energy resolutions is 1 fs. Several Doppler based methods were used to analyse the lineshape of 𝛾-ray peaks with a new simulation code EVASIONS.
Our new results will be presented. Doppler shifted 𝛾-ray spectra from 23Mg states were improved by imposing coincidences with the excitation energies reconstructed with VAMOS. This ensured to suppress the feeding from higher states. Lifetimes in 23Mg were measured with a new approach. Proton emitted from unbound states in 23Mg were also identified. With an higher precision on the measured lifetime and proton branching ratio of the key state, a new value of the resonance strength 𝜔𝛾 was obtained, it is below the sensitivity limit of the direct measurement experiments. The 22Na(p,𝛾)23Mg thermonuclear rate has been so reevaluated with the statistical Monte Carlo approach. The amount of 22Na ejected during novae will be discussed as a tool for better understanding the underlying novae properties. The detectability limit of 22Na from novae and the observation frequency of such events will also be discussed with respect to the next generation of gamma-ray space telescopes.
References
[1] A.L. Sallaska et al., Phys. Rev. L 105, 152501 (2010).
[2] F. Stegmuller et al., Nuc. Phys. A 601, 168-180 (1996).
[3] O.S. Kirsebom et al., Phys. Rev. C 93, 1025802 (2016).Speaker: Chloé Fougères (Argonne National Laboratory) -
11:55
Fission modeling for the astrophysical r-process 25m
The astrophysical rapid neutron capture (r-) process is thought to be responsible for the production of all of the observed thorium, uranium and plutonium in the cosmos. Many properties of the heaviest nuclei remain unmeasured, thus simulations of the r-process must rely on theory. Fission modeling, in the form of fragment yields, reaction rates and branching ratios, play an especially crucial role in determining the final outcomes of the heaviest nuclei and for the lighter fission product region. We review recent global calculations of fission properties based on theoretical modeling capabilities at Los Alamos, discuss their impact in the r-process and summarize our important results.
Speaker: Dr Matthew Mumpower (Los Alamos National Laboratory) -
12:20
Igniting SN-Ia supernovae with a natural fission chain reaction 20m
Type-Ia supernovae (SN Ia) are powerful stellar explosions that provide important distance indicators in cosmology. Recently, we proposed a new SN Ia mechanism that involves a nuclear fission chain reaction in an isolated white dwarf (WD) [PRL 126, 1311010]. The first solids that form as a WD starts to freeze are actinide rich and potentially support a fission chain reaction. In a WD plasma, melting points scale as Z^5/3 so actinides are expected to freeze first. In this talk we present fission chain reaction network calculations and new thermal diffusion simulations and find at high densities, above about 6x10^8$ g/cm$^3, that the fission heating can ignite carbon burning. This could produce a SN Ia or another kind of astrophysical transient.
Speaker: C. J. Horowitz (Indiana University) -
12:40
Employing ternary fission of 242Pu as a probe of neutron star matter 20m
Detailed assessments of the ability of recent theoretical approaches to modeling existing experimental data for ternary fission confirm earlier indications that the dominant mode of cluster formation in ternary fission is clusterization in very neutron rich, very low density, essentially chemically equilibrated, nucleonic matter [1-3]. An extended study and comparison of these approaches applied to ternary fission yields in the thermal neutron induced reaction 241Pu(n,f) 242Pu [4,5] was recently undertaken to refine the characterization of the source matter. The resonance gas approximation has been improved taking in-medium effects on the binding energies into account. A temperature of 1.25 MeV, density of 6.6 x 10-5 nucleons/ fm3 and proton fraction Yp = 0.036 are found to provide a good representation of yields of the ternary emitted light particles and clusters. In particular, results for Z= 1 and 2 isotopes are presentestrong textd. Isotopes with larger Z are discussed, and the role of Pauli blocking is shown. The derived properties are comparable to that predicted for the crystalline region in neutron star skins.
[1] J. B. Natowitz, H. Pais, G. Röpke, J. Gauthier, K. Hagel, M. Barbui, and R. Wada, Phys. Rev. C 102, 064621 (2020).
[2] G. Röpke, J. B. Natowitz, and H. Pais, Eur. Phys. J. A 56, 238 (2020).
[3] G. Röpke, J. B. Natowitz, and H. Pais, Phys. Rev. C 103, L061601 (2021).
[4] U. Koester et al., Nucl. Phys. A652, 371 (1999).
[5] A. S. Vorobyev et al., J. Expt. and Theor. Phys. 127, 659 (2018).Speaker: Prof. Gerd Roepke (University of Rostock, Institute of Physics) -
13:00
Fission properties for fission cycling regions of the r-process: the results, issues and uncertainty quantifications. 20m
The r process is responsible for the synthesis of approximately half of the nuclei in nature beyond Fe and it is the only process which leads to the creation of nuclei heavier than Bi [1]. Fission becomes important in the r process simulations for the neutron-to-seed ratios which are large enough to produce fissioning nuclei. It leads to the termination of the hot r process by means of fission cycling, which returns matter to lighter nuclei, and defines its strength [1,2]. In addition, it defines the possibility of the formation of neutron-rich superheavy nuclei in the r process.
A systematic investigation of the ground-state and fission properties of even-even actinides and superheavy nuclei with Z = 90–120 from the two-proton up to two-neutron drip lines with proper assessment of systematic theoretical uncertainties has been performed for the first time in the framework of covariant density functional theory (CDFT) [2]. These results provide a necessary theoretical input for the r-process modeling in heavy nuclei and, in particular, for the study of fission cycling. Four state-of-the-art globally tested covariant energy density functionals (CEDFs), namely, DD-PC1, DD-ME2, NL3*, and PC-PK1, representing the major classes of the CDFT models are employed in the present paper. Ground-state deformations, binding energies, two-neutron separation energies, $\alpha$-decay $Q_{\alpha}$ values and half-lives, and the heights of fission barriers have been calculated for all these nuclei in the axial relativistic Hartree-Bogoliubov approach with quadrupole and octupole deformations taken into account. The role of triaxial deformation has been studied for selected set of the nuclei. Theoretical uncertainties in these physical observables and their evolution as a function of proton and neutron numbers have been quantified and their major sources have been identified. Spherical shell closures at Z = 120, N = 184, and N = 258 and the structure of the single-particle (especially, high-j) states in their vicinities as well as nuclear matter properties of employed CEDFs are two major factors contributing to theoretical uncertainties. However, different physical observables are affected in a different way by these two factors. For example, theoretical uncertainties in calculated ground-state deformations are affected mostly by the former factor, while theoretical uncertainties in fission barriers depend on both of these factors.
In addition, recent global studies of separable pairing interaction reveal pronounced isospin dependence of neutron pairing [3]. Such dependence has been ignored in previous studies of the fission barriers in the fission cycling regions. However, the analysis of selected nuclei in these regions indicates substantial increase of fission barriers in very neutron-rich nuclei when it is taken into account [4]. The work on further studies of fission barriers in fission cycling regions is in progress and new results will be presented.
[1] S. Goriely, Eur. Phys. J. A51, 22 (2015).
[2] A.Taninah, S.E.Agbemava, and A.V.Afanasjev, Phys. Rev. C 102, 054330 (2020).
[3] S.Teeti and A.V.Afanasjev, Phys. Rev. C 103, 034310 (2021).
[4] A.V.Afanasjev and A. Taninah, Eur. Phys. J Web of Conferences 260, 03001 (2022)Speaker: Prof. Anatoli Afanasjev (Mississippi State University)
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Neutron Rich V: Plenary Sundial I and II
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Reactions with exotic nuclei and theoretical uncertainties 25m
Reactions with exotic nuclei and theoretical uncertainties
F.M. Nunes
Michigan State UniversityReaction theory is an essential element to study the properties of rare isotopes. Yet until recently, methods used to estimate uncertainties in reaction theories were ambiguous. Over the last decade, significant effort has been dedicated to quantifying uncertainties using Bayesian Statistics. In [1,2,3,4] we have quantified uncertainties in the effective interactions used in reaction theories and propagated those to a variety of reaction observables. It is now possible to obtain probability distributions for the parameters of the model. More importantly, it is now possible to make predictions of confidence intervals for reaction observables. Recently we have expanded the study to more complex reactions, by developing emulators which are fast and inexpensive [5]. We are now able to quantify uncertainties in reactions involving the breakup of halo nuclei. We have also used a variety of statistical tools to determine which observables are best to constrain specific parameters and determine which data provides maximum information [6].
In this presentation, we will provide an overview of these recent developments and provide an outlook on promising future developments.
[1] G.B. King et al., Phys. Rev. Lett. 122, 232502 (2019)
[2] A. Lovell et al., J. Phys. G 48, 014001 (2020)
[3] M. Catacora-Rios et al., Phys. Rev. C 100, 064615 (2019)
[4] T. Whitehead et al., Phys. Rev. C 105, 054611 (2022)
[5] O. Surer et al., Phys. Rev. C 106, 024607 (2022)
[6] M. Catacora-Rios et al., Phys. Rev. C 104, 064611 (2021)Speaker: Filomena Nunes (FRIB/MSU) -
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Theory of Surrogate Reactions 25mSpeaker: Jutta Escher (Lawrence Livermore National Laboratory)
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Informing neutron capture on A≈80 fission fragments 25m
Understanding neutron capture on mass ≈80 fission fragments is important for understanding weak r-process nucleosynthesis that could occur in supernova explosions. In these nuclei near the N=50 neutron shell closure, neutron capture is a competition between direct capture and statistical processes that proceed via a compound nucleus. Direct (and semi-direct that proceeds via the giant dipole resonance) (DSD) neutron capture depends on the excitation energies and spectroscopic factors of specific low angular momentum states. Near the N=50 shell closure, DSD capture depends on the 3s1/2 and 2d5/2 configurations above the shell gap and proceeds via p-wave capture. Because of the low-level density near the neutron separation energy, statistical processes probably do not contribute until higher neutron energies; however, details of the competition between these processes is unknown.
Surman and colleagues [1] have predicted that unknown (n,gamma) cross sections on the fission fragment 80Ge could have a significant impact on understanding weak r-process nucleosynthesis. To deduce the DSD capture on N≈50 neutron-rich nuclei, the spectroscopic factors of the low-lying 1/2+ and 5/2+ states need to be deduced. The (d,p) reaction with 80Ge beams has been measured near the Coulomb barrier [2]. However, with this low-energy beam, there are large uncertainties in the spectroscopic factors of the low-lying 1/2+ and 5/2+ states because of the unknown bound-state potential. By measuring the (d,p) reaction with 86Kr [3] and 84Se [4,5] beams at two energies, near the Coulomb barrier and with ≈40 MeV/u beams, we have demonstrated that we can reduce the uncertainties in these spectroscopic factors. To inform the competition between DSD and statistical neutron capture requires measurements of decay gamma radiation in coincidence with (d,p) reaction protons. We are approved to measure the (d,p gamma) reaction with ≈40 MeV/u 80Ge beams at FRIB and would use charged-particle – gamma-ray coincidence techniques developed with stable beams to realize this measurement.
The present talk will give an overview of the previous measurements of (d,p) and (d,p gamma) reactions with A≈80 fission fragment beams that inform the expected efficacy of the proposed 80Ge beam measurement to inform (n,gamma) rates. We will summarize how measuring the (d,p) reaction at two very different beam energies constrains the spectroscopic factors needed for DSD calculations. We will also summarize the successful deployment of the coupling of the Oak Ridge Rutgers University Barrel Array (ORRUBA) to the GRETINA array of gamma-ray detectors and how this configuration would be modified for measurements at FRIB.
The critical role of the GODDESS collaboration, in particular S.D. Pain, A. Ratkiewciz, H.E. Sims, and D. Walter, is acknowledged. This work is supported in part by the National Science Foundation and the U.S. Department of Energy.
[1] R. Surman et al., AIP Advances 4, 041008 (2014).
[2] S. Ahn et al., Phys. Rev. C 100, 044613 (2019)
[3] D. Walter et al., Phys. Rev. C 99, 054625 (2019).
[4] J.S. Thomas et al., Phys. Rev C 76, 044302 (2007).
[5] H.E. Sims Ph.D. dissertation (Rutgers University 2020) and to be published.
Speaker: Jolie Cizewski (Rutgers University) -
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Statistical and shell effects in beta-delayed neutron emission 25m
With access to very neutron-rich isotopes, the neutron emission from excited states populated after beta decay becomes a dominant deexcitation mode. The neutron energy measurement informs about beta-decay strength distribution, which is driven by shell effects. The neutron emission is thought to be a result of statistical emission. Measurements performed in regions of 54Ca, 78Ni and 132Sn were performed with neutron arrays BRIKEN [1] and VANDLE [2]. BRIKEN experiments provided information on single and two-neutron emissions, which is essential for r-process modeling [3]. VANDLE experiments are also sensitive to neutron energies that directly enabled beta-decay strength distribution measurement. Surprisingly, we have also found evidence for non-statistical neutron emission in several cases, which was deduced from neutron and gamma-ray spectroscopy. It forced us to revisit a conventional picture of neutron emission thought to proceed via a compound nucleus phase. A model which connects nuclear structure and neutron emission was developed to explain the observed phenomenon [4].
[1] A. Tarifeño-Saldivia et al 2017 JINST 12 P04006
[2] W. A. Peters et al., Nucl. Instrum. Methods Phys. Res. A 836, 122 (2016).
[3] R. Yokoyama et al., Phys. Rev. C 100 (2019) 031302(R).
[4] J. Heideman et al. submittedSpeaker: Robert Grzywacz (University of Tennessee) -
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Multi-Proton Decay of the Lightest Isotopes 25mSpeaker: Prof. Kyle Brown (FRIB/MSU)
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Reflections on Fission 30mSpeaker: Patrick Talou (Los Alamos National Laboratory)
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Educator and Researcher Extraordinaire 30m
The accomplishments of a physicist over a long career can be measured by the large number of publications, invited talks, and funded grants. Professor Joseph Hamilton’s 64-year career is amazingly accomplished by all of these measures, including over 1000 publications. Beyond these normal barometers of excellence are the equally important areas of mentorship and teaching of students, and Joe’s career is unmatched in these ways also.
The mentorship numbers are stunning: around 100 graduate students with Vanderbilt degrees, 120 postdocs, 10,000 non-science students taught. For decades Joe taught an extremely popular physics course for non-science majors. His passion for physics and his knack for showmanship in demonstrations made him an extremely popular teacher in a discipline not known for attracting the masses.
As one of his early grad students, I benefited greatly from Joe’s mentorship and partnership in various phases of his career and mine. He educated many students in research as he progressed through five phases of his amazingly productive career in nuclear structure physics. The first 15 years of his career utilized radioactive decay, resulting in 133 publications, the first one in 1956. Initially these experiments were performed at Vanderbilt, but then I was the first of a series of Joe’s students that worked on dissertation research at Oak Ridge National Laboratory. The second phase focused on accelerator-based experiments at ORNL, most with his former grad school (Indiana) colleague Russell Robinson.
The third phase of Joe’s career focused on the radioactive decay of nuclei far from stability, primarily focused on new consortia and instruments he led at ORNL. The UNISOR collaboration of 11 universities resulted in a mass separator installed on-line at the Oak Ridge Isochronous Cyclotron with the first experiment in 1972 and 20 years of research. To reach nuclei farther from stability, Joe led a big effort to build the Recoil Mass Spectrometer at ORNL, and UNISOR evolved into UNIRIB with the development of radioactive beams.
Perhaps the most prolific phase of Joe’s career involved studies of the spontaneous fission of 252Cf located in Gammasphere, resulting in 380 papers, including 39 letter articles. Joe and his many colleagues studied 187 nuclei producing new insights on the fission process and the level structures of over 90 neutron-rich nuclei.
The fifth phase of his long research career focused on super-heavy nuclei. Joe put together the consortium that produced 249Bk (in the ORNL reactor) made into a target for six months of running time at the Dubna accelerator. Elements 117 and 118 were discovered, and the former was named after Joe’s home state – Tennessine. An amazing capstone of an amazing career.
Speaker: Prof. Lee Riedinger (University of Tennessee) -
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Reflections on a Career in Nuclear Science and Other Things 30mSpeaker: Joseph Hamilton
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