Speaker
Description
In this paper, we present new cross sections measurements of the 197Au(n,2n)196Au and 89Y(n,2n)88Y reactions induced by ~14MeV neutrons. These new measurements are determined with a relative activation method.
We irradiate foils targets of gold and yttrium with ~14MeV neutron flux produced using the SAMES neutron accelerator facility [1] at CEA of Valduc, through the d+t-> n14,7 MeV+α reaction. These experiments were performed from 2011 to 2014 at CEA. Activation products of interest 196Au and 88Y are measured by gamma spectrometry with a 2% precision (2σ).
Foils targets of gold and yttrium were also systematically co-located with reference foils of titanium and aluminum. Some activation products of titanium and aluminum are used to properly estimate the neutrons flux in the target: 24Na produced by the reaction 27Al(n,α)24Na, 48Sc produced by the reaction 48Ti(n,p)48Sc, 47Sc produced by the reaction 47Ti(n,p)47Sc and 46Sc produced by the reaction 46Ti(n,p)46Sc.
To deal with these measurements, we need to properly assess the neutron flux spectrum in the targets. This has been done with MCNP-5 [2] simulation code using a model of the SAMES accelerator and experimental set. The relative position of targets foils with respect to the head of accelerator lead to slight differences on neutron flux spectrum and mean energy (13.7 MeV, 13.9 MeV and 14.5 MeV). These configurations are taken into account in our simulations and used to assess our final results and associated uncertainties.
We finally assess cross-sections of interest by using IRDFF data for reference foils to normalize our work. We also obtain the uncertainties on these reference cross-sections by covariance propagation by an adjoint method [3] and/or EXFOR library experimental data [4].
Our results are plotted on the figure 1 below and compared with cross section from different international libraries including ENDF/B-VIII.0 [5,6]. Experimental points from EXFOR are added for comparison with our work.
We can see in this figure the huge consistency between our results on yttrium and main evaluations of related reaction cross section. The cross section shape correctly intersects our measurements within error bars.
[ See attached file]
Figure 1 : 89Y(n,2n)88Y and 197Au(n,2n)196Au reaction cross sections compared to our results
We can see slightly spread results on our gold measurements but relatively good agreement with ENDF/B-VIII.0 and JENDL-4.0 evaluations. We can see that CENDL-3.2 evaluation is not consistent with this new gold measurement.
Finally, our new measurements around 14MeV tend to confirm international evaluations of 89Y(n,2n)88Y cross sections and discriminate some 197Au(n,2n)196Au cross sections evaluations.
REFERENCES
- E. Bauge et al., Eur. Phys. J. A., 48, pp. 113-142 (2012).
- MCNP, A general Monte-Carlo N-particle Transport Code, Version 5, report LA-UR-03-1987, LANL Los Alamos (2003).
- J. Cartier, Proceeding of conference M&C 2009, Saratoga Springs USA (2009).
- EXFOR: Experimental nucl. data base, NEA/OECD Paris, http://www.nea.fr/dbdata/x4.
- D.A. Brown et al., ENDF/B-VIII.0: The 8th Major Release of the Nuclear Reaction Data Library with CIELO-project Cross Sections, New Standards and Thermal Scattering Data, Nuclear Data Sheets, Vol. 148, pp 1 – 142 (2018).
- M.B. Chadwick et al., Evaluated Iridium, Yttrium, and Thulium Cross Sections and Integral Validation Against Critical Assembly and Bethe Sphere Measurements, Nuclear Data Sheets, Vol.108, pp 2716 - 2741 (2007).