n+^(233)U裂变碎片质量分布的唯象模型研究

Study on Mass Distribution of n+^(233)U Fission with Phenomenological Model

本模型基于裂变多通道无规颈断裂模型,考虑宏观液滴能、壳效应能以及壳效应与温度的关系,得到参数化的势能表示形式。通过拟合不同测量方法得到的实验数据(经过评价)获得3组模型参数。3组参数计算的碎片质量分布均很好地再现了不同能点的实验数据,除了基于动能法实验数据得到的参数外,其14 MeV的计算结果与实验数据符合较差。研究发现,不同入射中子能量的裂变碎片质量分布有4个主要交叉点,在交叉点之上的产额随入射中子能量增加减少,之下的产额则随入射中子能量上升;内侧(或外侧)的两个交叉点质量数之和近似等于裂变复合核的质量数;不同裂变系统的重峰左侧的交叉点都保持在132附近。

Present model was based upon Brosa model, where macro energy, shell effect energy and its decreasing with system temperature were considered and parameterized. 3 sets of model parameters were obtained by fitting to 3 groups of evaluated experimental data, respectively, where the groups were classified by measured method： radiochemistry （RA） method, double kinetic energy （KE） method, and both （ALL）. All the 3 sets of parameters could well reproduce the measured mass distributions on different energies, except the KE set on 14 MeV. The result shows the mass distributions mainly had 4 trend turning points, above which the yield decreasing and below which the yield increasing with energy The sum of the 1 st and 4th （or 2nd and 3rd） point positions was equal to the compound nuclei mass approximately. And the 3rd point was kept at ~ 132 constantly for different fission systems n ＋233 U, n ＋235 U, n ＋233 Pu.