X射线照射金属腔体后，会在内部空间中发射出大量光电子，从而产生很强的系统电磁脉冲(SGEMP)。激光惯性约束聚变(ICF)装置内的X射线环境非常复杂，在靶室内工作的诊断设备即使有良好的电磁屏蔽，仍会面临严重的SGEMP干扰。以神光-III(SG-III)装置靶室内部的X射线环境为背景，采用时偏时域有限差分(FDTD)方法和粒子模拟(PIC)方法对二维圆柱腔体模型内部的SGEMP进行数值模拟。针对电磁场的振荡现象，在传统的粒子模拟算法基础上采用时偏方法进行滤波，去除了高频误差对计算的影响，结果更加准确。最后，得到的SG-III装置靶室内SGEMP干扰约为1.5 MV/m。

When the X-ray irradiates metal cavities, a large number of photoelectrons will be emitted into the internal space, resulting a strong System Generated Electromagnetic Pulse(SGEMP). The X-ray environment within laser Inertial Confinement Fusion(ICF) facilities is very complicated, so diagnostics working in target chamber area will face severe SGEMP interference even with good electromagnetic shielding. In light of the X-ray environment inside target chamber of Shenguang-III (SG-III) laser facility, a numerical simulation of the EM field inside a two-dimensional cylindrical cavity model is completed with the time-biased Finite-Difference Time-Domain(FDTD) and Particle-In-Cell(PIC) methods. As for the oscillation of electromagnetic field, based on the classic PIC method, the time-biased arithmetic is utilized to filter the waveform. Therefore, the influence of high-frequency error on the calculation result is removed, and the simulation would be more accurate. Finally, the SGEMP interference in the SG-III laser facility is estimated to be about 1.5 MV/m.