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arXiv 2109.08178nucl-exnucl-th
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融合诊断用$^{86}$ Kr截面的评价

Evaluation of $^{86}$Kr Cross Sections For Use in Fusion Diagnostics

M. Vorabbi, G. P. A. Nobre, D. A. Brown, A. M. Lewis, E. Rubino, S. Mughabghab

摘要:

劳伦斯利弗莫尔国家实验室的国家点火装置使用$^{86}$ Kr作为诊断工具来测量聚变反应产生的中子通量。由于氪是化学惰性的,它可以被直接注入燃料舱,反应产物可以被测量以确定聚变中子的通量。$^{86}$ Kr截面也为s过程中的$^{85}$ Kr分支点和恒星中的中子通量提供了模型约束。在这项工作中,有关$^{86}$ Kr的中子产生、辐射捕获、非弹性散射和总截面的实验数据与快区核反应代码EMPIRE和新的共振区评估结合使用,以产生对$^{86}$ Kr的中子诱导反应的新评估。对于EMPIRE计算,我们拟合的光学模型势高达12兆电子伏,同时再现的实验数据的总截面和主要的非弹性伽马跃迁从$2^+$状态的$0^+$基态。对于12 MeV以上的能量,由于总截面数据中的大的波动和不确定性,我们倾向于采用Koning-Delaroche全局球光学模型势。通过这些模型和对$^{86}$ Kr结构的修正,评估的截面与实验数据相匹配。新的评价已提交,以纳入ENDF/B核反应库的下一个版本。

英文摘要:

The National Ignition Facility at Lawrence Livermore National Laboratory uses $^{86}$Kr as a diagnostic tool to measure the neutron flux produced by fusion reactions. As krypton is chemically inert, it can be implanted directly into the fuel capsule, and the reaction products can be measured to determine the flux of fusion neutrons. $^{86}$Kr cross sections also provide model constraints for the $^{85}$Kr branching point in the s-process and the neutron flux in stars. In this work, experimental data on the neutron production, radiative capture, inelastic scattering, and total cross sections of $^{86}$Kr were used in conjunction with the fast region nuclear reaction code EMPIRE and a new resonance-region evaluation to produce a new evaluation of neutron-induced reactions on $^{86}$Kr. For the EMPIRE calculations, we fitted the optical model potential up to 12 MeV to simultaneously reproduce the experimental data for the total cross section and the main inelastic gamma transition from the $2^+$ state to the $0^+$ ground state. For energies above 12 MeV, due to large fluctuations and uncertainties in the total cross section data, we preferred to adopt the Koning-Delaroche global spherical optical model potential. With these models and corrections to the structure of $^{86}$Kr, the evaluated cross sections matched the experimental data. The new evaluation has been submitted for incorporation in the next release of the ENDF/B nuclear reaction library.

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