厚靶轫致辐射在粒子输运模拟中的实现与验证

The Implementation and Verification of the Thick-Target Bremsstrahlung in the Particle Transportation Simulation

为提升自行开发的粒子输运蒙特卡罗模拟软件PHEN对电子输运模拟的处理能力,根据厚靶轫致辐射(thick-target bremsstrahlung,TTB)模型,在PHEN中加入了自编的TTB模块,分析了加入TTB模块后PHEN的模拟计算速度、TTB模块生成的轫致辐射光子能量及TTB模块模拟电子输运的适用范围。通过与MCNP中轫致辐射截面及电子射程的对比,验证了TTB模块模拟电子输运的正确性。计算了加入TTB模块前后正电子湮没峰计数的变化,用于判断使用TTB模块模拟的合理性。计算结果表明:当材料尺寸小于电子在材料中的射程时,TTB模型不考虑电子输运的计算结果是不合理的,应采用压缩历史算法处理电子输运;当材料尺寸大于电子在材料中的射程时,TTB模型计算速度快,计算结果与压缩历史算法的计算结果吻合较好,可用厚靶轫致辐射处理电子输运。

To enhance the processing capability of electron transportation simulation with PHEN （the transportation program of photon, haon, electron, and neutron）, the TTB module was compiled for PHEN based on the TTB （thick-target bremsstrahlung） model. The simulating speed of TTB module, the energy of the bremsstrahlung photon generated by TTB module, and the scope of application of TTB module were analyzed. The TTB module was verified by comparing the bremsstrahlung cross-section and electron range with those given by MCNP. The count of positron annihilation peak was calculated to estimate the simulation results. The calculation result shows that TTB model is irrational as it does not include the electron transport when the medium size is less than the electron range in the medium, and the simulation result of TTB module fits well with the simulation result of the compression history method, and the simulating speed of TTB module is faster than that of the compression history method when the medium size is greater than the electron range in the medium.