An improved numerical method to compute neutron/gamma deexcitation cascades starting from a high spin state
Numerous nuclear processes involve the deexcitation of a compound nucleus through the emission of several neutrons, gammarays and/or conversion electrons. The characteristics of such a deexcitation are commonly derived from a total statistical framework often called “Hauser–Feshbach” method. In this work, we highlight a numerical limitation of this kind of method in the case of the deexcitation of a high spin initial state. To circumvent this issue, an improved technique called the Fluctuating Structure Properties (FSP) method is presented. Two FSP algorithms are derived and benchmarked on the calculation of the total radiative width for a thermal neutron capture on ^{238}U. We compare the standard method with these FSP algorithms for the prediction of particle multiplicities in the deexcitation of a high spin level of ^{143}Ba. The gamma multiplicity turns out to be very sensitive to the numerical method. The bias between the two techniques can reach 1.5 γγ/cascade. Lastly, the uncertainty of these calculations coming from the lack of knowledge on nuclear structure is estimated via the FSP method.
 Authors:

^{[1]};
^{[2]};
^{[2]}
 CEA, DEN, DER, SPRC, Saint Paul lez Durance (France); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
 CEA, DEN, DER, SPRC, Saint Paul lez Durance (France)
 Publication Date:
 Report Number(s):
 LLNLJRNL668707
Journal ID: ISSN 00104655
 Grant/Contract Number:
 AC5207NA27344
 Type:
 Accepted Manuscript
 Journal Name:
 Computer Physics Communications
 Additional Journal Information:
 Journal Volume: 201; Journal Issue: C; Journal ID: ISSN 00104655
 Publisher:
 Elsevier
 Research Org:
 Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
 Sponsoring Org:
 USDOE
 Country of Publication:
 United States
 Language:
 English
 Subject:
 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Hauser–Feshbach; statistical model; deexcitation; cascade; FIFRELIN
 OSTI Identifier:
 1342046
 Alternate Identifier(s):
 OSTI ID: 1247062
Regnier, D., Litaize, O., and Serot, O.. An improved numerical method to compute neutron/gamma deexcitation cascades starting from a high spin state. United States: N. p.,
Web. doi:10.1016/j.cpc.2015.12.007.
Regnier, D., Litaize, O., & Serot, O.. An improved numerical method to compute neutron/gamma deexcitation cascades starting from a high spin state. United States. doi:10.1016/j.cpc.2015.12.007.
Regnier, D., Litaize, O., and Serot, O.. 2015.
"An improved numerical method to compute neutron/gamma deexcitation cascades starting from a high spin state". United States.
doi:10.1016/j.cpc.2015.12.007. https://www.osti.gov/servlets/purl/1342046.
@article{osti_1342046,
title = {An improved numerical method to compute neutron/gamma deexcitation cascades starting from a high spin state},
author = {Regnier, D. and Litaize, O. and Serot, O.},
abstractNote = {Numerous nuclear processes involve the deexcitation of a compound nucleus through the emission of several neutrons, gammarays and/or conversion electrons. The characteristics of such a deexcitation are commonly derived from a total statistical framework often called “Hauser–Feshbach” method. In this work, we highlight a numerical limitation of this kind of method in the case of the deexcitation of a high spin initial state. To circumvent this issue, an improved technique called the Fluctuating Structure Properties (FSP) method is presented. Two FSP algorithms are derived and benchmarked on the calculation of the total radiative width for a thermal neutron capture on 238U. We compare the standard method with these FSP algorithms for the prediction of particle multiplicities in the deexcitation of a high spin level of 143Ba. The gamma multiplicity turns out to be very sensitive to the numerical method. The bias between the two techniques can reach 1.5 γγ/cascade. Lastly, the uncertainty of these calculations coming from the lack of knowledge on nuclear structure is estimated via the FSP method.},
doi = {10.1016/j.cpc.2015.12.007},
journal = {Computer Physics Communications},
number = C,
volume = 201,
place = {United States},
year = {2015},
month = {12}
}