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SUMMARY:Modeling the energy dependence of the 237-Np(n\,f) reaction cross-
 section in the 0.1–30 MeV range
DTSTART;VALUE=DATE-TIME:20261027T151000Z
DTEND;VALUE=DATE-TIME:20261027T151500Z
DTSTAMP;VALUE=DATE-TIME:20261022T104629Z
UID:indico-contribution-6439@cern.ch
DESCRIPTION:Speakers: Ksenia Enenko (National Research Nuclear University 
 MEPhI)\nA general understanding has emerged regarding the processes govern
 ing a wide range of nuclear reactions\, particularly fission—see\, for e
 xample\, the review in [1]. Based on this understanding\, computer codes h
 ave been developed to calculate total and partial cross-sections for the i
 nteraction of nuclei with light nuclear particles\, specifically neutrons.
  All such codes rely on models describing various stages of the reaction\,
  and each model involves specific parameters. Typically\, however\, only s
 ome of these parameters can be fixed\, while the values of others remain u
 ncertain.\nIn this work\, we calculate the fission cross-section of the 23
 7-Np nucleus as a function of incident neutron energy in the 0.1–30 MeV 
 range and compare the results with experimental data [2–4]. This reactio
 n was selected because recent work [5] provided additional information on 
 the process—specifically\, measurements of fission fragment angular anis
 otropy in the 0.4–200 MeV range. Reference [5] also presented a novel me
 thod for calculating angular anisotropy and demonstrated that a joint comp
 arison of calculated and measured values for both the fission cross-sectio
 n and angular anisotropy will allow obtaining additional information about
  the fission process. However\, the authors of [5] were unable to reproduc
 e the observed dependence of the fission cross-section on incident neutron
  energy in certain energy intervals.\nIn the present work\, the open-sourc
 e code TALYS (version 2.2) [6] was used to model the 237-Np(n\,f) reaction
  for incident neutron energies ranging from 0.1 to 30 MeV. The complexity 
 of modeling fission arises from the fact that\, in addition to the optical
  model and level-density model parameters built into the code\, we must al
 so consider parameters defining the shapes of fission barriers and nuclear
  characteristics at those barriers. Typically\, calculations performed in 
 TALYS using default parameters fail to accurately reproduce the energy dep
 endence of the fission cross-section. This case turned out to be exactly l
 ike this. Therefore\, in this work\, the parameters that determine both th
 e shape of the double-humped fission barriers of Np isotopes with mass num
 bers from 238 to 235\, as well as the collective increase in the level den
 sity and the shape of the nuclei on the humps of the barriers of these sam
 e isotopes\, were varied. This approach enabled us to reproduce the experi
 mentally observed energy dependence of the fission cross-section with high
  accuracy. The resulting parameter values can be incorporated into models 
 describing the angular anisotropy of fission fragments in the ²³⁷Np(n\
 ,f) reaction\, thereby yielding new insights into the characteristics of t
 ransition states at the fission barriers.\n\n1. Capote R. et al. Nuclear D
 ata Sheets\, v. 110\, p. 3107 (2009).\n2. Shcherbakov O.A. et al. JNST\, v
 . 39\, suppl. 2\, p. 230 (2002).\n3. Paradela C. et al. PRC\, v. 82\, 0346
 01 (2010).\n4. Vorobyev A.S. et al. Bull. Russ. Acad. Sci.: Phys.\, v. 89\
 , p. 1329 (2025).\n5. Vorobyev A.S. et al. JETP Letters\, v. 110\, p. 242 
 (2019).\n6. Koning A.J.\, Hilaire S.\, Goriely S. EPJA\, v. 59\, p. 131 (2
 023).\n\nhttps://indico.particle.mephi.ru/event/626/contributions/6439/
LOCATION:Sevastopol hotel Conference Hall 1
URL:https://indico.particle.mephi.ru/event/626/contributions/6439/
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