Evaluation of the total photoabsorption cross sections for actinides from photofission data and model calculations
Evaluation of the total photoabsorption cross sections for actinides from photofission data and model calculations
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根据光裂变数据和模型计算评估锕系元素的总光吸收截面
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
I. Strakovsky
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作者：
I. Pshenichnov;B. Berman;W. Briscoe;C. Cetina;G. Feldman;P. Heimberg;A. S. Iljinov;I. Strakovsky
用RELDIS蒙特-卡罗程序计算了237-Np，233，235，238-U，232-Th和nat-Pb吸收能量从68 MeV到3.77 GeV的光子后的裂变几率。该代码实现了中能光核反应的级联蒸发裂变模型。它包括核内核子光反应中的多粒子产生，预平衡发射，以及通过蒸发，裂变和多重碎裂过程的竞争激发剩余核的统计衰变。计算表明，在GeV能量范围内，裂变过程并不是整个光吸收截面的唯一原因，甚至对于锕系元素也是如此：232-Th约占55-70%，238-U约占70-80%，233-U、235-U和237-Np约占80-95%。这是因为在GeV光子能量下由深光子学产生的某些剩余核具有相对较低的裂变概率。利用萨斯喀彻温实验室和杰斐逊实验室最近获得的237-Np和233，235，238-U的光裂变截面的实验数据和我们计算的裂变几率，我们推断了这四个核的总光吸收截面。由此得到的每个核子的横截面在形状和大小上彼此一致。然而，与以前测量的从C到Pb的原子核的总光吸收截面数据在量值上的不一致，使人们对所有原子核的每个核子的光吸收截面的"通用曲线“的概念提出了质疑。
We have calculated the fission probabilities for 237-Np, 233,235,238-U, 232-Th, and nat-Pb following the absorption of photons with energies from 68 MeV to 3.77 GeV using the RELDIS Monte-Carlo code. This code implements the cascade-evaporation-fission model of intermediate-energy photonuclear reactions. It includes multiparticle production in photoreactions on intranuclear nucleons, pre-equilibrium emission, and the statistical decay of excited residual nuclei via competition of evaporation, fission, and multifragmentation processes. The calculations show that in the GeV energy region the fission process is not solely responsible for the entire total photoabsorption cross section, even for the actinides: ~55-70% for 232-Th, ~70-80% for 238-U, and ~80-95% for 233-U, 235-U, and 237-Np. This is because certain residual nuclei that are created by deep photospallation at GeV photon energies have relatively low fission probabilities. Using the recent experimental data on photofission cross sections for 237-Np and 233,235,238-U from the Saskatchewan and Jefferson Laboratories and our calculated fission probabilities, we infer the total photoabsorption cross sections for these four nuclei. The resulting cross sections per nucleon agree in shape and in magnitude with each other. However, disagreement in magnitude with total-photoabsorption cross-section data from previous measurements for nuclei from C to Pb calls into question the concept of a ``Universal Curve' for the photoabsorption cross section per nucleon for all nuclei.