When an X-ray beam illuminates a material’s surface, the backscattered photo-electrons are emitted from the surface and stimulate the system-generated electromagnetic pulse (SGEMP). With the increase in X-ray flux, the space charge-limited (SCL) effect occurs and a relatively thin layer develops near the emitting surface. The characteristic time is defined as the occurring time of the SCL effect. In this article, an accurate analytical equation is derived by applying the momentum conservation equation for the mono-energetic electrons and verified by the particle-in-cell (PIC) simulation. But for electrons with velocity distribution, the analytic equation using the average velocity approximation, instead of the exponential distribution, is not accurate, as the interaction between the low-energy and high-energy electrons is ignored. PIC simulation results show that the characteristic time of the SCL effect is longer by the PIC simulation than the average energy approximation when the average energy of the electrons is relatively low and vice versa.

中文翻译：

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SGEMP空间电荷限制效应特征时间计算

当 X 射线束照射材料表面时，背向散射的光电子从表面发射出来并激发系统产生的电磁脉冲 (SGEMP)。随着 X 射线通量的增加，空间电荷限制 (SCL) 效应发生并且在发射表面附近形成相对薄的层。特征时间定义为 SCL 效应的发生时间。在本文中，通过应用单能电子的动量守恒方程并通过粒子内粒子 (PIC) 模拟验证，推导出准确的解析方程。但是对于具有速度分布的电子，使用平均速度近似而不是指数分布的解析方程是不准确的，因为忽略了低能电子和高能电子之间的相互作用。