利用超快电子探针诊断受激拉曼散射静电波的数值模拟

Numerical simulation on diagnosis of stimulated Raman scattered electrostatic wave using relativistic electron probe

利用二维粒子模拟程序EPOCH验证了超快电子束探针诊断受激拉曼散射产生的静电波的可行性。结果表明,电子束探针穿过静电波电场后会在电子束探针的横向上产生密度调制,密度调制呈周期性分布且沿静电波的传播方向移动,密度调制的波数对应静电波的波数且移动速度对应静电波的相速度,因此特定条件下可用于反推电子的温度、密度等信息。在诊断静电波的过程中,电子束探针的束长必须小于静电波的波长或者诊断设备的曝光时间必须小于静电波的周期。本研究提供了一种新型的直接诊断静电波和电子温度、密度的方法,对于推动受激拉曼散射等激光等离子体不稳定性的实验研究具有重要意义。

This paper uses the two-dimensional particle-in-cell simulation program EPOCH to verify the feasibility of the relativistic electron beam probe in diagnosing the electrostatic wave generated by stimulated Raman scattering.The results show that the electron beam probe will produce density modulation in the transverse direction of the electron beam probe after passing through the electrostatic wave’s electric field.The density modulation is periodically distributed and moves along the propagation direction of the electrostatic wave.The wavenumber of the density modulation corresponds to the wavenumber of the electrostatic wave.And the moving speed corresponds to the phase speed of the electrostatic wave,so it can be used to deduce the temperature and density of electrons under certain conditions.In the process of diagnosing electrostatic waves,the beam length of the electron beam probe must be shorter than the wavelength of the electrostatic wave or the exposure time of the diagnostic equipment must be less than the period of the electrostatic wave.The research in this paper provides a new method of directly diagnosing the temperature and density of electrostatic waves and electrons,which is of great significance for promoting the experimental research of stimulated Raman scattering and other laser plasma instabilities.