摘要：
本文基于核内级联物理过程,采用Monte Carlo方法发展了一款质子、中子以及π介子的粒子输运程序。基本物理模型基于适当简化和核内级联Bertini模型,同时借鉴了INCL模型质心系下的角微分分布以克服Bertini模型之不足,即采用Monte Carlo方法模拟核子与核子、核子与π介子间的弹性散射、非弹性散射等过程,粒子相互作用时,核子密度随半径变化且作用截面参考Bertini模型22类实验截面数据,出射粒子散射角在质心系下的抽样遵从INCL模型所确定的微分分布。可模拟45—3500 MeV的中子、质子或2500 MeV以下π介子引起的核内级联过程。入射粒子能量在60—378 MeV范围内反应截面理论计算值与已有实验数据、以及在65—3000 MeV较宽能区范围内反应截面、出射粒子增殖比、微分截面和剩余核等计算结果与MCNPX, GEANT 4和PHITS模拟结果符合较好。%The Monte Carlo intra-nuclear cascade program CBIM has been developed for describing spallation reactions involving protons, neutrons and pions on complex nuclei. In order to describe cascade process, several simplifications and assumptions are made in the following: firstly, neither reaction, nor reflection, nor refraction, nor ionization will be taken into account before the incident particle enters into the target nucleus; secondly, target nucleus is regarded as being spherical and the atom number should be greater than 2;thirdly, the knocked nucleon is determined by cross section sampling;finally, in the center-of-mass frame, the scattering angle is sampled based on differential cross section distribution. The basis physics model is based on the above assumptions and Bertini intra-nuclear cascade model; meanwhile, nucleon-nucleon angle differential distributions of INCL in the center-of-mass frame are introduced to overcome the shortage of Bertini model. The interactions between nucleon and nucleon or between nucleon and pion, such as elastic scattering, pion production and charge exchange, are included in the code. In the particles collision, the nucleon density changes with the target nucleus radius;and the interaction cross sections refer to 22 kinds of experimental cross sections in Bertini model. The intra-nuclear cascades induced by 45–3500 MeV neutron, proton or pion below 2500 MeV can be simulated by this code. Finally, comparisons between experimental reaction cross section over the energy range 60–378 MeV, and some simulation results by MCNPX, GEANT4 and PHITS over the energy range 65–3000 MeV show that they are in reasonable agreement with the CBIM results over the broad energy range considered.
