Speaker
Description
The Chi-Nu project at the Los Alamos Neutron Science Center (LANSCE) continues to measure Prompt Fission Neutron Spectra (PFNS) as accurately and completely as possible, with fully understood uncertainties including uncertainty correlations. These measurements use the LANSCE/WNR white-spectrum neutron beam and cover incident neutron energies from below 1 MeV to 20 MeV, and were originally focussed on the major actinides. However, the program has grown to include PFNS measurements for neutron-induced fission of $^{240}$Pu, as well as some spontaneous fissioning nuclei. Two neutron detector arrays are used, combined with multi-cell Parallel Plate Avalanche Counters[3] or a single-cell fission chamber (for $^{242}$Pu) for fission detection. Detailed Monte Carlo simulations of the experimental setup were used to model the neutron response and determine PFNS for each case, as a function of incident neutron energy for the neutron-induced cases. The experimental details are discussed in detail in Ref. [1].
To date, Chi-Nu PFNS data have been reported on neutron-induced fission of $^{239}$Pu[1] and $^{235}$U[2], and data on neutron-induced fission of $^{238}$U and spontaneous fission of $^{242}$Pu and $^{240}$Pu have been taken. These data will be presented and compared with prior data and current evaluations. All of these data sets were taken using similar detector arrangements and analysis methods, so comparisons of the PFNS of the various isotopes can be made with improved accuracy, as some of the uncertainties are similar in all cases. We will discuss a few such comparisons. Such comparisons will also be discussed and compared to evaluations and integral experiment results.
This work is supported by the U.S. Department of Energy under Contracts No. 89233218CNA000001 (LANL) and DE-AC52-07NA27344 (LLNL).
[1] K.J. Kelly, et al., Phys. Rev. C 102, 034615 (2020).
[2] M. Devlin, et al., Nucl. Data Sheets 148, 322 (2018).
[3] C.-Y. Wu, et al., Nucl. Instr. And Meth. A794, 76 (2015).
LA-UR-21-29659