2023 Rmatrix Workshop on Methods and Applications
from
Tuesday, 20 June 2023 (08:00)
to
Friday, 23 June 2023 (17:00)
Monday, 19 June 2023
Tuesday, 20 June 2023
08:30
08:30  09:00
09:00
Welcome

James deBoer
Carl Brune
Welcome
James deBoer
Carl Brune
09:00  09:15
09:15
Intro to Rmatrix

Mark Paris
Intro to Rmatrix
Mark Paris
09:15  10:30
10:30
10:30  11:00
11:00
SAMMY Calculations

Marco Pigni
SAMMY Calculations
Marco Pigni
11:00  12:00
12:00
12:00  12:30
12:30
Lunch
Lunch
12:30  14:00
14:00
The modified Rmatrix approach for nuclear astrophysics

Marco La Cognata
(
INFNLNS
)
The modified Rmatrix approach for nuclear astrophysics
Marco La Cognata
(
INFNLNS
)
14:00  14:30
In nuclear astrophysics, when approaching the Gamow window for chargedparticle fusion reactions, the signaltonoise ratio approaches zero due to vanishingly small cross sections and extrapolation, e.g., performing Rmatrix fits of ancillary data sets, is necessary. Even in those few case where underground measurements made it possible to approach and, sometimes, span the Gamow window, electron screening hides the true trend of the cross section, making extrapolation necessary anyway. Indirect methods have then introduced to reach astrophysical energies with no need of extrapolation. Among these, the Trojan Horse Method [1] has been introduced 30 years ago to determine the lowenergy trend of the astrophysical Sfactor for binary reactions (excluding radiative captures), by selecting the quasifree contribution to a reaction with three particles in the exit channel. In the case of resonant reactions, the astrophysical factor of the binary reaction of astrophysical interest is deduced from the triple different cross section of the quasifree reaction through the application of a modified Rmatrix approach [2]. In this presentation, we will discuss the basic equations of this approach, the analogies with the standard Rmatrix analysis, and present some case studies to illustrate advantages and drawbacks of the method. [1] Tumino, A., et al., Annual Review of Nuclear and Particle Science, Volume 71, pp. 345376, 2021 [2] Tribble, R. E., et al., Reports on Progress in Physics, Volume 77, Issue 10, article id. 106901, 2014
14:30
A ML approach to resonance spin group classification

David Brown
(
NNDC  Brookhaven National Laboratory
)
A ML approach to resonance spin group classification
David Brown
(
NNDC  Brookhaven National Laboratory
)
14:30  15:00
The performance of nuclear reactors and other nuclear systems depends on a precise understanding of the neutron interaction cross sections for materials used in these systems. These cross sections exhibit resonant structure whose shape is determined in part by the angularmomentum quantum numbers of the resonances. The correct assignment of the quantum numbers of neutron resonances is, therefore, paramount. In this project, we apply machine learning to automate the quantum number assignments using only the resonances’ energies and widths and not relying on detailed transmission or capture measurements. The classifier used for quantum number assignment is trained using stochastically generated resonance sequences whose distributions mimic those of real data. We explore the use of several physicsmotivated features for training our classifier. These features amount to outofdistribution tests of a given resonance’s widths and resonancepair spacings. We pay special attention to situations where either capture widths cannot be trusted for classification purposes or where there is insufficient information to classify resonances by the total spin J. We demonstrate the efficacy of our classification approach using simulated and actual 52Cr and 238U resonance data.
15:00
Making Rmatrix Evaluations for 3He+4He and p+6Li scattering for Data Libraries.

Ian Thompson
(
LLNL
)
Making Rmatrix Evaluations for 3He+4He and p+6Li scattering for Data Libraries.
Ian Thompson
(
LLNL
)
15:00  15:30
The existing ENDF/BVIII.0 data library only contains elastic scattering for 3He+4He scattering reaction. The evaluation for p+6Li scattering does contain an outgoing 3He+4He channel, but only up to 2.5 MeV lab proton energy. Since these two reactions have the same compound nucleus – 7Be – it should be possible to fit both reactions simultaneously using an Rmatrix parameter model that fits all reaction data that involves the same compound nucleus. Rmatrix models have parameters for each level: an energy, a spin and parity, and a partial width for every partial wave that couples to that spin and parity. When fitted to known data, including both angleintegrated data and angular cross sections from available experiments, and also total cross sections for incident neutrons, a model naturally predicts excitation functions at all energies for all included channels for angleintegrated and angular cross sections. Naturally these predictions will be most accurate in the regions of the data, in order avoid risky extrapolation. I report on recent work in fitting Rmatrix parameters for the 7Be compound system, in order to make candidate evaluations for both the 3He+4He and p+6Li incoming channels and thus make improvements to two evaluations for the forthcoming ENDF/BVIII.1 library. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DEAC5207NA27344.
15:30
15:30  16:00
16:00
Intro to EDA

Mark Paris
Intro to EDA
Mark Paris
16:00  17:00
17:00
Example calculations with AZURE2

Richard deBoer
(
University of Notre Dame
)
Example calculations with AZURE2
Richard deBoer
(
University of Notre Dame
)
17:00  18:00
I will give a short tutorial on the use of AZURE2 by demonstrating low energy $^{12}$C(p,p) and (p,$\gamma$) data as an example. I will briefly discuss how to get the code, its installation, where to get data to fit, data file formats, use of the GUI to build an example calculation, and how to look at the output. I’ll focus on common pitfalls in making these calculations.
18:00
18:00  19:30
Wednesday, 21 June 2023
08:30
08:30  09:00
09:00
Disentangling clustering phenomena in 12C and 16O

Kevin Ching Wei Li
(
Department of Physics, University of Oslo, N0316 Oslo, Norway
)
Disentangling clustering phenomena in 12C and 16O
Kevin Ching Wei Li
(
Department of Physics, University of Oslo, N0316 Oslo, Norway
)
09:00  09:30
$^{12}\textrm{C}$ remains at the forefront of nuclear structure studies as it is the predicted site of a wide range of interesting phenomena and is also astrophysically significant. The challenge of understanding the structure of $^{12}\textrm{C}$ thus endures as a litmus test of our ability to not only theoretically model nuclei, but to also phenomenologically analyse/interpret data. This talk will present recent work which aims to disentangle broad, intertwined contributions to the excitation spectrum of $^{12}\textrm{C}$, populated through inelastic scattering and transfer reactions (with preliminary results on $^{16}\textrm{O}$ also presented).
09:30
Rmatrix analysis of the $^{18}$O($\alpha$,$\alpha$) resonant elastic scattering and $^{22}$Ne structure

Grigory Rogachev
(
Texas A&M University
)
Aliya Nurmukhanbetova
(
Energetic Cosmos Laboratory, Nazarbayev University, Astana, Kazakhstan
)
Alexander Volya
(
Florida State University
)
Vladilen Goldberg
(
Texas A&M University
)
Rmatrix analysis of the $^{18}$O($\alpha$,$\alpha$) resonant elastic scattering and $^{22}$Ne structure
Grigory Rogachev
(
Texas A&M University
)
Aliya Nurmukhanbetova
(
Energetic Cosmos Laboratory, Nazarbayev University, Astana, Kazakhstan
)
Alexander Volya
(
Florida State University
)
Vladilen Goldberg
(
Texas A&M University
)
09:30  10:00
Low energy $^{18}$O+$\alpha$ interaction is expected to play an important role in astrophysical processes [1]. The $^{18}$O($\alpha$,$\gamma$) reaction synthesizes $^{22}$Ne, the main neutron source for the weak sprocess, and the reaction $^{18}$O($\alpha$,$n$) $^{21}$Ne with a neutron threshold of E$_\alpha$= 851 keV has been proposed as a weak neutron source in the production of $^{19}$F in TPAGB stars [1]. The properties of $^{22}$Ne states populated in the $^{18}$O+$\alpha$ resonant interaction are also of interest for cluster development in Ne region and, specifically, for understanding the influence of extra neutrons on alpha cluster structure in $^{20}$Ne [2]. The studies of $^{22}$Ne are also important for comparison of alpha cluster properties in mirror resonant reactions $^{18}$O+$\alpha$ and $^{18}$Ne+$\alpha$ [3]. The measurements for the $\alpha$+$^{18}$O elastic scattering were made in a broad energy interval in two old high energyresolution works [4,5] and in a relatively recent inverse kinematics publication [6]. None of these data was analyzed in the framework of Rmatrix theory. We performed measurements of the $\alpha$+$^{18}$O elastic scattering in the inverse kinematics at lower energy than it was in the reference [6] to enhance an influence of the states at a lower excitation energy, and we made the full Rmatrix analysis of all available data on the $\alpha$+$^{18}$O resonant elastic scattering in the energy region 1115 MeV excitation energy in $^{22}$Ne. We present theoretical predictions that are essential for understanding resonant structure at high excitation energy with high density of states and a few decay modes. We also present new data on the structure of the states in $^{22}$Ne in comparison with shell model predictions. We consider specific features of the experimental approaches important for the analysis and possible improvements of the AZURE code [7]. References: [1] A. Best et al.,Phys. Rev. C 87, 045806 (2013). [2] A. K. Nurmukhanbetova,et al.,Phys. Rev. C 100, 062802(R) (2019). [3] A. Volya et al.,Commun Phys 5, 322 (2022). [4] D. Powers et al.,Phys. Rev. 134, B1237 (1964). [5] S. Gorodetzky et al.,J. Phys. France 29, 271278 (1968). [6] V. Z. Goldberg et al.,Phys. Phys. Rev. C 69, 024602 (2004). [7]https://azure.nd.edu/login.php.
10:00
The impact of 16O(e,e'alpha)12C measurements on the astrophysical S factor for the 12C(alpha,gamma)16O reaction.

David Potterveld
(
Argonne National Laboratory
)
The impact of 16O(e,e'alpha)12C measurements on the astrophysical S factor for the 12C(alpha,gamma)16O reaction.
David Potterveld
(
Argonne National Laboratory
)
10:00  10:30
The $^{12}{\rm C}(\alpha,\gamma)^{16}{\rm O}$ reaction (CTAG) has long been of intense interest because of its importance in stellar nuclear evolution. The small cross section at stellar energies cannot be directly measured in the lab. Cross sections must be measured at higher energies and extrapolated down using theory, usually expressed as an RMatrix model. Recently, measurements of $^{16}{\rm O}$ electrodisintegration cross sections near threshold have been proposed as a way to constrain the stellarenergy CTAG cross section. We have performed a Bayesian analysis of the existing CTAG world data combined with possible low and high energy electrodisintegration measurements to predict how much improvement can be expected. This work was performed using Azure2 as a calculational engine in a novel Monte Carlo integration technique that is superior to the ubiquitous Markov Chain Monte Carlo. We will show that feasible measurements at high energy can provide significant improvement comparable to that of measurements at the lowest practical energies.
10:30
10:30  11:00
11:00
Definite parametrization of Rmatrix cross sections

Pablo Ducru
Definite parametrization of Rmatrix cross sections
Pablo Ducru
11:00  11:30
**Definite formalism introduces new standard for nuclear cross section data.** Our common knowledge of nuclear reactions was build over a century of experimental campaigns, recording cross sections and fitting them with parametric models of quantum interactions. The resulting Rmatrix parameters are documented in and constitute the pillar of standard evaluated nuclear data libraries. Yet, though presently the standard, WignerEisenbud Rmatrix parameters are somewhat arbitrary quantities introduced for calculation and documentation. Building upon recent findings to go past the WignerEisenbud parameters, we introduce a [new Rmatrix formalism][1] based on fundamental physical quantities — the poles of the scattering matrix — and propose it as a new definite standard for nuclear cross sections. Critically, nuclear cross sections can now be fully described — with all their levels, resonances, and energy dependence — with a finite number of natural and invariant physical parameters (as many as the number of levels). [1]: https://doi.org/10.1103/PhysRevC.105.024601
11:30
Capture width distributions from the Atlas of Neutron Resonances

David Brown
(
NNDC  Brookhaven National Laboratory
)
Capture width distributions from the Atlas of Neutron Resonances
David Brown
(
NNDC  Brookhaven National Laboratory
)
11:30  12:00
Nuclear data is used for a variety of purposes in our daily life, from basic science to advanced usages like nuclear power. Below roughly 1 MeV incident energy, neutron cross sections show fluctuations, or resonances, whose energies and widths are not predictable. The resonances for a given nucleus can be summarized with a few parameters such as the average resonance spacing and the average widths of the resonance peaks. These averages are important input for nuclear reaction and structure models. The goal of my project is to study the average resonance capture widths and resonance spacings using the resonance data compiled in the *Atlas of Neutron Resonances*. As the provenance of these values in the published *Atlas of Neutron Resonances* is unclear, we refit the empirical cumulative level distributions for each possible spin group to extract the average spacings. Similarly, we refit the empirical capture width distributions to extract the average capture widths and the capture degrees of freedom. We discussed the implications of the obtained widths and capture degrees of freedom.
12:00
12:00  12:30
12:30
Lunch
Lunch
12:30  14:30
Thursday, 22 June 2023
08:30
08:30  09:00
09:00
Investigation of proposed threshold resonance in 6Li(p, γ)7Be reaction

Dr. Pareshkumar Prajapati
(
Manipal Academy of Higher Education, Manipal  576104
)
Investigation of proposed threshold resonance in 6Li(p, γ)7Be reaction
Dr. Pareshkumar Prajapati
(
Manipal Academy of Higher Education, Manipal  576104
)
09:00  09:30
The abundance of lithium in the universe is a complex topic involving all three main nucleosynthesis processes [1]. The 6Li (p, γ)7Be crosssection influences a variety of astrophysical scenarios, including bigbang and stellar nucleosynthesis. The 6Li(p, γ)7Be reaction has been studied extensively using direct [2] and indirect methods [3]. The lowenergy trend of its crosssection remains uncertain as different measurements have reported conflicting results. In particular, the existence of a positive parity state (3/2+) of 7Be at center of mass energy 195 keV [4] is still matter of debate. In view of this, we have performed a detailed Rmatrix analysis on 3He(α, γ)7Be and 6Li (p, γ)7Be reactions. In the Rmatrix formalism, both capture and scattering data sets have been utilized to check the existence of resonance like structure at center of mass energy 195 keV. References: 1. J. A. Johnson, Science 363, 474 (2019) 2. D. Piatti et al, Phys. Rev. C 102, 052802 (R) (2020) 3. G. G. Kiss et al, Phys. Rev. C 104, 015807 (2021) 4. J. J. He et al, Phys. Lett. B 725, 287 (2013)
09:30
Direct measurement of 19F(p,a)16O reaction cross section

Teodora Madgearu
(
ELINP
)
Direct measurement of 19F(p,a)16O reaction cross section
Teodora Madgearu
(
ELINP
)
09:30  10:00
The 19F(p,a)16O reaction plays a significant role in the production of fluorine in asymptotic giant branch (AGB) stars. The cross sections for different reaction channels are crucial input parameters for stellar models, and their accuracy has a significant impact on the predicted yields of fluorine in AGB stars. The a0 channel of the 19F(p,a)16O reaction has relatively large uncertainties in the cross section. New experimental data and Rmatrix calculations including world data are necessary for improving the accuracy of the reaction rates. In a recent study, Lombardo et al. used Rmatrix calculations to estimate the reaction rate of the a0 channel in the 19F(p,a)16O reaction, and found that the current uncertainties in the cross section are dominated by the uncertainty in the resonance strength. New experimental data on the a0 channel has become available this year which could be used to refine the Rmatrix calculations. This would have important implications for our understanding of the chemical evolution of galaxies and the nucleosynthesis of light elements in the universe. In this work, we present a new Rmatrix calculation of the a0 channel in the 19F(p,a)16O reaction, taking into account the latest experimental data. The AZURE2 code was used to perform the calculations.
10:00
An indepth Rmatrix analysis of the proton capture on carbon isotopes

Jakub Skowronski
(
Università degli Studi di Padova
)
An indepth Rmatrix analysis of the proton capture on carbon isotopes
Jakub Skowronski
(
Università degli Studi di Padova
)
10:00  10:30
Since the 12C/13C ratio in the stellar atmosphere is an important indicator of the stellar nucleosynthesis, both the 12C(p,g)13N and 13C(p,g)14N reactions are crucial elements that can help improving the stellar models. More specifically, the 12C/13C ratio could be used to constrain the mixing models inside AGB stars. In a recent study at the Laboratory for Underground Nuclear Astrophysics (LUNA), both reactions have been studied using different types of solid targets, and employing complementary detection techniques. The new datasets and their deviation with respect to the literature imposed the necessity of a new reaction rate evaluation. To achieve this, new Rmatrix fits were carefully performed for both reactions, taking into account all the literature data. Both the frequentist and bayesian models were employed to study the differences between the two approaches and to assess the best way of dealing with systematic uncertainties.
10:30
10:30  11:00
11:00
Study of the 34Ar(a,p)37K reaction rate and its effects on Xray Burst Stellar Models

Amber LauerColes
(
Brookhaven National Laboratory
)
Study of the 34Ar(a,p)37K reaction rate and its effects on Xray Burst Stellar Models
Amber LauerColes
(
Brookhaven National Laboratory
)
11:00  11:30
The rate of the reaction $^{34}$Ar$(\alpha, p)^{37}$K, as one of the last reactions in the socalled $(\alpha, p)$ process, may influence the shape of the TypeI Xray Burst light curve, as shown in recent XRB stellar modelling studies. Type I XRay bursts (XRBs) are energetic stellar explosions that occur on the surface of a neutron star in an accreting binary system with a lowmass H/Herich companion. Due to the extreme thermodynamic conditions a thinshell instability can cause a Heflash in the surface nucleosynthesis, resulting in thermonuclear runaway. This is accompanied by a burst of photons in the Xray spectrum, referred to as a ”light curve”. In addition, under the "waiting point" phenomenon, nucleosynthesis may stall with a corresponding stall in the accompanying XRB light curve. As such an $(\alpha,p)$ reaction which has become energetically favored during the extreme thermodynamics of the burst may bypass this waiting point despite its normally low cross section, reigniting the burst and escaping the stall. This work discusses the results of an experiment to study resonances of the $^{38}$K compound nucleus of the $(\alpha, p)$ reaction on the $^{34}$Ar nucleus via proton scattering on $^{37}$K. The resonant reaction rate is dependent on the features of resonances in the Gamow energy window for the XRB. This talk will review the entire process, especially highlighting the unique Rmatrix analysis with the AZURE2 software package to constrain the reaction rate. The newly estimated rate was applied to XRB models built using Modules for Experiments in Stellar Astrophysics (MESA), to examine its impact on observables, including the light curve and abundances.
11:30
Shedding light on 17O(n,α)14C reaction at astrophysical energies with Trojan Horse Method and Asymptotic Normalization Coefficient

Giovanni Luca Guardo
Shedding light on 17O(n,α)14C reaction at astrophysical energies with Trojan Horse Method and Asymptotic Normalization Coefficient
Giovanni Luca Guardo
11:30  12:00
The 17O(n,α)14C reaction is considered in astrophysical codes for its role in the astro physically relevant ”s(slow)process” since it could act as a possible “neutronpoison” for the neutron induced nucleosynthesis thus influencing the final stellar abundances of some elements such as Fe, Ni or Sr. Thus, its reaction rate must be known in the energy region of interest for astrophysics, going from few keV’s up to about 400 keV. At such energies, the intermediate 17O+n→18O nucleus presents four excited levels (8038, 8125, 8213, and 8282 keV’s) affecting the magnitude of the 17O+n cross section at astrophysical energies because of the neutron emission threshold at 8044 keV for 18O. Although the role of the two 8213 keV (Jπ=2+) and 8282 keV (Jπ=3−) was already investigated in the direct measurements, insufficient informations are up to now available about the 8125 keV (Jπ=5−) resonant level, thus requiring a detailed experiment. Indirect methods have been largely proved in the past as a complementary way of accreting our knowledge about nuclear structure and lowenergy cross section measurements. Among these, the neutron induced reaction cross section appear to be of particular interest since their role both for unstable and stable beams. In view of this, we report here the combined study of the 17O(n,α)14C accomplished by the Trojan Horse Method (THM) and the Asymptotic Normalization Coefficient (ANC) method. The low lying resonances 8038, 8125, 8213, and 8282 keV in 18O are studied and Γn are derived by applying the modified Rmatrix approach. A comparison with direct measurements and recent THM experimental data is presented. The independent ANC investigation corroborate our previous THM results, confirms the consistence of the two indirect investigation and shows new frontiers also in view of neutron induced reactions with radioactive ion beams.
12:00
12:00  12:30
12:30
Lunch
Lunch
12:30  14:30
14:30
Measurement and Rmatrix analysis of the 7Be + n reactions updating the primordial lithium abundance

Seiya Hayakawa
(
Center for Nuclear Study, the University of Tokyo
)
Measurement and Rmatrix analysis of the 7Be + n reactions updating the primordial lithium abundance
Seiya Hayakawa
(
Center for Nuclear Study, the University of Tokyo
)
14:30  15:00
The cosmological lithium problem has been known as the outstanding discrepancy of primordial lithium abundances between observations and theoretical predictions. We have measured key nuclear reactions which act to reduce $^7$Li during the big bang nucleosynthesis (BBN), namely, $^7$Be$(n,p)^7$Li and $^7$Be$(n,\alpha)^4$He. We also performed Rmatrix fits to data sets including both the previous and present cross sections of the $(n,p_0)$, $(n,p_1)$ and $(n,\alpha)$ reaction channels based on the resonances at known excited levels. This analysis resulted in an improved uncertainty evaluation of the $(n,p_0)$ cross section, and the firstever quantification of the $(n,p_1)$ contribution in the BBN energy region. The updated $(n,p_0) + (n,p_1)$ reaction rate offers nonnegligible reduction in the primordial $^7$Li abundance prediction, which reduces the discrepancy in the lithium problem.
15:00
RMatrix analysis of the neutroninduced cross sections on $^{147,149}$Sm and $^{143}$Nd measured at LANSCE

Esther Leal Cidoncha
(
LANL
)
RMatrix analysis of the neutroninduced cross sections on $^{147,149}$Sm and $^{143}$Nd measured at LANSCE
Esther Leal Cidoncha
(
LANL
)
15:00  15:30
The RMatrix code SAMMY [1] was used to analyze the neutroninduced cross section data on $^{147,149}$Sm and $^{143}$Nd measured at LANSCE and previous measurements on $^{143}$Nd [2] in order to understand how the new data impact the criticality benchmark discrepancies identified in [3]. The $^{147,149}$Sm transmission and capture cross sections were measured using the Device for Indirect Capture Experiments on Radionuclides (DICER) and the Detector for Advanced Neutron Capture Experiments (DANCE) respectively. Although $^{147}$Sm was not a concern in [3], it was included in the analysis because the DICER $^{147}$Sm sample contained a small amount of $^{149}$Sm and it allows us to better characterize the $^{149}$Sm resonances near 0.097 and 0.87 eV. The capture cross section on $^{143}$Nd was measured with DANCE. Separated spin capture data on $^{143}$Nd and $^{147,149}$Sm were calculated following the procedure from [4]. The total cross section data from [2] are unclear as to the proper sample thickness for the RMatrix analysis, so the impact of this uncertainty was explored. [1] N. M. Larson, UPDATED USERS GUIDE FOR SAMMY: MULTILEVEL RMATRIX FITS TO NEUTRON DATA USING BAYES EQUATIONS, ORNL/TM9179/R8, ENDF364/R2 (2008). [2] H. Tellier, PROPRIETES DES NIVEAUX INDUITS PAR LES NEUTRONS DE RESONANCE DANS LES ISOTOPES STABLES DU NEODYME, CEAN1459 (1971). [3] L. C. Leal et al., Assessment of Fission Product CrossSection Data for Burnup Credit Applications, ORNL/TM2005/65. [4] P. Koehler et al., Phys. Rev. C 76, 025804 (2007).
15:30
Measuring 23Na(p, γ)24Mg Direct Capture Reaction Rate using (3He,d) Spectroscopy

Kaixin Song
Measuring 23Na(p, γ)24Mg Direct Capture Reaction Rate using (3He,d) Spectroscopy
Kaixin Song
15:30  16:00
The reaction rates of a sodium destruction reaction 23Na(p,γ)24Mg play an important role while suffering from large uncertainties in hydrogen burning temperatures. We performed a 23Na(3He,d) measurement in angular range of 5°≤θlab≤21° at E(3He)=21MeV using the Enge Splitpole Spectrograph at Triangle Universities Nuclear Laboratory. Energy states below the 23Na + p threshold in 24Mg were examined. For those states, spectroscopic factors were extracted with rigorous uncertainties using Bayesian MCMC and DWBA method. We used those to calculate the most updated direct capture cross sections and reaction rates for 23Na(p,γ)24Mg. The ANCs for each state were also calculated and used to compare with results from Rmatrix studies.
16:00
16:00  16:30
16:30
Rmatrix analysis of 19F(α,n)22Na reaction

Paraskevi Dimitriou
(
International Atomic Energy Agency
)
Rmatrix analysis of 19F(α,n)22Na reaction
Paraskevi Dimitriou
(
International Atomic Energy Agency
)
16:30  17:00
(alpha,n) reactions at low energies up to 10 MeV are relevant for a wide range of applications including the reactor fuel cycle, spent fuel management, nonproliferation, fusion technologies, low background experiments, and nuclear astrophysics. All these applications depend on accurate and precise experimental data that are incorporated in reliable evaluated libraries. However, in regard to (α,n) data, the evaluated libraries are either incomplete or outdated. We report on our efforts to evaluate the 19F(α,n)22Na reaction at energies up to 9 MeV using Rmatrix analysis.
17:00
Rmatrix analysis of $^{9}$Be($\alpha$,n)$^{12}$C reaction and determination of reaction rate

Suprita Chakraborty
(
B.A.V Girls
)
Rmatrix analysis of $^{9}$Be($\alpha$,n)$^{12}$C reaction and determination of reaction rate
Suprita Chakraborty
(
B.A.V Girls
)
17:00  17:30
$^{12}$C is the seed nucleus for the formation of next heavier nuclei in the supernovae ejecta, which are the inputs of succeeding rapid neutron capture process. The nucleus $^{12}$C is mostly formed by triplealpha process in our universe. Modern research shows that the nucleosynthesis at the astrophysical site of typeII supernova produces significant amount of $^{12}$C through the neutron catalyzed reaction $^{4}$He($\alpha$n,$\gamma$)$^{9}$Be($\alpha$,n)$^{12}$C in neutron and alpharich hot bubble region. In this region, the neutron catalyzed reaction $^{4}$He($\alpha$ n,$\gamma$)$^{9}$Be($\alpha$,n)$^{12}$C occurs 40 times faster than the triplealpha reaction. Considering the importance of $^{9}$Be($\alpha$,n)$^{12}$C reaction for the production of $^{12}$C in supernovae ejecta, in this present work we have performed a simultaneous phenomenological Rmatrix analysis of the data of three different exit channels formed due to the collision of $\alpha$ and $^{9}$Be nucleus. The aim is to find out the reaction rate of $^{9}$Be($\alpha$,n)$^{12}$C reaction at the relevant temperature more precisely than the previous works. The experimental data of the main reaction channel $^{9}$Be($\alpha$,n)$^{12}$C have been taken from Kunz *et al*. [phys.Rev.C **53**, 5 (1996)] and Wrean *et al*. [Phys. Rev. C **49**, 1205 (1994)] and elastic data of exit channel have been taken from Halt *et al*. [Observation and analysis of elastic neutron scattering from $ ^{12} $C Proc. Conf. on Nuclear Cross Sections and Technology (Washington, DC) SP425 VolI, pp 246–9 (1975)], Schwartz *et al*.[National Burenu of Standards Report, NBS138, (1974).] and Lister *et al*. [Phys.Rev **143**, 745 (1966)]. Also we have included the data of reverse reaction of $^{9}$Be($\alpha$,n)$^{12}$C. The experimental data of $^{12}$C(n,$\alpha$)$^{9}Be$ have been taken from Kuvin and Lee *et al*. [Phys. Rev. C **104**, 014603 (2021)] and Giorginis *et al*. [EXFOR]. Apart from the astrophysical interest, another objective of choosing this system is to find out the unknown spin parities of some of the resonances theoretically using Rmatrix fitting process. We have fitted altogether twenty five resonances. As the separation energy of neutron is lower than $ \alpha $ so first $8$ resonances are used to fit the elastic data of exit channel. We have fitted the data of reaction channel $^{9}$Be($\alpha$,n)$^{12}$C from $E_{c.m}=0.16$ MeV to $2.5$ MeV. To fit the data of this reaction channel we needed $11$ resonances. Additional $6$ resonances are needed to describe the experimental data of $^{12}$C(n,$\alpha$)$^{9}Be$ as the data set of Kuvin and Lee *et al*. is extended up to $E_{x}=14.6$ MeV. To fit the elastic data we had to incorporate $4$ background poles at excitation energy $E_{x}=20$ MeV. However no background pole is needed to fit the reaction channel. From a preliminary investigation we obtained the spin parity of the resonance at $E_{x}=11.748$ is $1/2^{+}$. Finally reaction rate has been evaluated. At lower temperature region below T$_{9}=0.1$ our value is $10$ to $15$ times higher than Fowler *et al*. [At. Data Nucl. Data Tables **40**, 283 (1988)]. Also our value of reaction rate at low energy region is larger than that obtained by Kunz *et al*. The probable reason of obtaining a high value is the estimation of sharper resonance at $E_{x}=10.753$ MeV than Kunz *et al*.. Also we have planned to extend our fitting by incorporating the elastic data of entrance channel in our simultaneous Rmatrix analysis. Our work is in progress and will be presented.
17:30
17:30  18:00
18:00
18:00  22:00
Friday, 23 June 2023
08:30
08:30  09:00
09:00
Approximation of RMatrix Resonance Parameter Sensitivities Using The Windowed Multipole Method

Matthew Lazaric
(
University of New Mexico
)
Approximation of RMatrix Resonance Parameter Sensitivities Using The Windowed Multipole Method
Matthew Lazaric
(
University of New Mexico
)
09:00  09:30
The goal of this work is to develop a method of approximating RMatrix resonance parameter sensitivities for use in future sensitivity analysis studies. The inclusion of resonance parameters and resonance parameter covariances has been increasing with each subsequent release of ENDF/B. From these resonance parameters and their associated covariances, nuclear data evaluation codes can uniquely determine the expected value and variance of the cross section within a given energy range. Quantifying the impact that a lone resonance parameter has on the entire cross section space using standard Rmatrix methods has been shown to be both computationally expensive and time consuming due to the sheer number of resonance parameters in modern evaluations. This research aims to investigate the use of the Windowed Multipole method of evaluating cross sections to approximate Rmatrix resonance parameter sensitivities. This method was chosen because it can produce analytic cross section sensitivities to both pole parameters and temperature onthefly, allowing for the approximation of both level energy and resonance width sensitivities. This research compares analytic sensitivity profiles generated by the Windowed multipole method against those generated numerically and investigates the impact of the differences on cross section uncertainty.
09:30
Deep learning application on the Rmatrix phenomenology

Chanhee (Ben) Kim
(
Sungkyunkwan Univ.
)
Deep learning application on the Rmatrix phenomenology
Chanhee (Ben) Kim
(
Sungkyunkwan Univ.
)
09:30  10:00
While the Rmatrix phenomenology is dominantly used in nuclear physics, it contains two categories of unobservable parameters  channel radius and background poles. These parameters sometimes lead to ambiguities in the Rmatrix fits of experimental data. Here, we propose a method to tackle this challenge using deep learning techniques. We train a customized deep learning model to predict the physical objects, such as resonance properties, from the observational data without the information on the channel radius and background poles. After training, the model only requires the measurement data to extract resonance parameters. We demonstrate this method with data from the measurement of 12C+p elastic scattering. Results also indicate that the Rmatrix analysis using deep learning techniques has some advantages over conventional methods in terms of speed, uncertainty quantification, etc.
10:00
10:00  10:30
10:30
Deep underground laboratory measurement of $^{13}$C($\alpha$,n)$^{16}$O in the Gamow windows of the s and iprocesses

Xiaodong Tang
(
Institute of Modern Physics, CAS
)
Deep underground laboratory measurement of $^{13}$C($\alpha$,n)$^{16}$O in the Gamow windows of the s and iprocesses
Xiaodong Tang
(
Institute of Modern Physics, CAS
)
10:30  11:00
The $^{13}$C($\alpha$,n)$^{16}$O reaction is the main neutron source for the slowneutroncapture (s) process in Asymptotic Giant Branch stars and for the intermediate (i) process. Direct measurements at astrophysical energies in aboveground laboratories are hindered by the extremely small cross sections and vast cosmicray induced background. We performed the first consistent direct measurement in the range of E$_{\rm c.m.}$ =0.24 MeV to 1.9 MeV using the accelerators at the China JinPing underground Laboratory (CJPL) and Sichuan University. Our measurement covers almost the entire iprocess Gamow window in which the large uncertainty of the previous experiments has been reduced from 60% down to 15%, eliminates the large systematic uncertainty in the extrapolation arising from the inconsistency of existing data sets, and provides a more reliable reaction rate for the studies of the s and iprocesses along with the first direct determination of the $\alpha$strength for the nearthreshold state.
11:00
Monte Carlo R matrix analysis of the lowenergy 13C(a,n)16O cross section

Andreas Best
(
University of Naples Federico II
)
Monte Carlo R matrix analysis of the lowenergy 13C(a,n)16O cross section
Andreas Best
(
University of Naples Federico II
)
11:00  11:30
The reaction 13C(a,n)16O is the main neutron source of the astrophysical s process, and its cross section needs to be known in the energy range 150230 keV to accurately model stellar nucleosynthesis. Due to the low cross section at these energies a direct measurement is very challenging, and up to now there is still some extrapolation required. The main components that influence the cross section behaviour is a nearthreshold 1/2+ state and a 3.2+ state at about 7.21 MeV. Further complications arise from differences between normalisations of higherenergy data. We present a Monte Carlo analysis based on Azure2 of the lowenergy cross section including a new data set measured by the LUNA collaboration that reached the Gamow energy range. An outlook at further work including other recent data and covering a larger energy range is presented.
11:30
Rmatrix analysis of 8Be System

Som Paneru
(
Los Alamos National Laboratory
)
Rmatrix analysis of 8Be System
Som Paneru
(
Los Alamos National Laboratory
)
11:30  12:00
Deuteroninduced reactions on 6Li are important for nuclear structure studies and for nuclear applications. Even after several measurements of 6Li(d,n)7Be reaction in the past, the partial cross section information for 6Li(d,n)7Be reaction is lacking as there are discrepancies between various Rmatrix evaluations. To address these discrepancies, a new measurement of 6Li(d,n)7Be was performed at University of Notre Dame in collaboration with Oak Ridge National Laboratory and University of Notre Dame to obtain neutron angular distributions. In addition to neutrons, this experiment simultaneously measured the various reactions products from different reaction channels, including charged particles, and gammas, which would aid in better determination of angleintegrated partial cross sections. The experimental details and preliminary results from the ongoing analysis will be discussed. In addition, a multichannel Rmatrix analysis is performed to fit the data for 6Li(d,n0,1)7Be, 6Li(d,p0,1)7Li, 6Li(d,d)6Li, a(a,a)a, 7Li(p,a)a, and 7Li(p,n)7Be channels simultaneously using phenomenological Rmatrix code AZURE2. All these channels form 8Be compound nucleus. The details of the Rmatrix analysis and preliminary results will be presented and compared with the EDA fit that is used for the current ENDF/B evaluation.
12:00
12:00  12:30
12:30
Lunch
Lunch
12:30  14:30