Geant4 simulation of fast electron bremsstrahlung imaging at the HL-3 tokamak

A simulation for calculating fast-electron bremsstrahlung in the HL-3 tokamak based on the Monte Carlo simulation code Geant4 is developed, in which the plasma geometry and forward scattering of fast-electron bremsstrahlung are considered. The preliminary calculation results indicate that the HXR energy deposition on the detector is symmetrically distributed, even though the plasma distribution is asymmetric owing to the toroidal effect. These simulation results are helpful in constructing the relationship between the energy deposition on the detector and parameter distribution on the plasma cross section during HL-3 experiments. This is beneficial for the reconstruction of the fast-electron distribution function and for optimizing the design of the HXR-imaging system.

本研究开发了一套基于蒙特卡洛模拟程序Geant4的HL-3托卡马克快电子轫致辐射（fast-electron bremsstrahlung）计算模拟框架，其中考虑了等离子体几何构型与快电子轫致辐射的前向散射效应。初步计算结果显示，尽管环向效应导致等离子体分布呈现非对称性，但探测器上的硬X射线（Hard X-ray, HXR）能量沉积呈现对称分布。上述模拟结果有助于建立HL-3实验中探测器能量沉积与等离子体截面参数分布之间的关联关系，可为快电子分布函数的重构以及硬X射线成像系统的优化设计提供支撑。