基于Geant4模拟的康普顿散射研究

The research of Compton scattering based on Geant4 simulation

摘要:

在暗物质直接探测实验当中，高能gamma射线是重要的本底来源之一. 高能光子由于康普顿散射的原因会在高纯锗探测器中会产生低能本底. CDMSlite实验中发现低能区域的康普顿能谱存在康普顿台阶，脉冲近似(Impulse Approximation, IA)理论解释了台阶出现的原因是原子中电子处于束缚状态，它使用散射函数来描述电子的束缚效应. 为了探究这些台阶与散射函数以及入射能量之间的关系，我们使用Geant4程序对康普顿散射中的康普顿台阶进行了研究. 研究发现随着初始光子能量增高，K壳层与L壳层的康普顿台阶会变得越来越平缓，直至斜率趋近于零.

Abstract:

High-energy gamma ray is one of the most important sources of radiation background in direct dark matter detection experiments. High-energy photons produce a low-energy radiation background in high-purity germanium detectors due to Compton scattering. The CDMSlite experiment demonstrates that the Compton steps exist in the Compton spectrum of the low-energy region. The Impulse Approximation (IA) theory explains that the reason for the steps is the electrons in the atom being in a bound state, and uses a scattering function to describe the binding effect of electrons. To explore the relationships between these steps and the scattering function and incident energy, we use the Geant4 program to study the Compton steps in Compton scattering. It is found that as the initial photon energy increases, the Compton steps of the K-shell and the L-shell become more and more gradual until the slope approaches zero.