入射电子能量对低密度聚乙烯深层充电特性的影响

高能带电粒子与航天器介质材料相互作用引起的深层带电现象, 一直是威胁航天器安全运行的重要因素之一. 考虑入射电子在介质中的电荷沉积、能量沉积分布以及介质中的非线性暗电导和辐射诱导电导, 建立了介质深层充电的单极性电荷输运物理模型. 通过求解电荷连续性方程和泊松方程, 可以得出不同能量 (0.1–0.5 MeV) 电子辐射下, 低密度聚乙烯 (厚度为1 mm) 介质中的电荷输运特性. 计算结果表明, 不同能量的电子辐射下, 介质充电达到平衡时, 最大电场随入射能量的增加而减小; 同一能量辐射下, 最大电场随束流密度的增大而增加. 入射电子能量较低时 (≤ 0.3 MeV) , 最大电场随束流密度的变化趋势基本相同. 具体表现为: 当束流密度大于3× 10^-9 A/m²时, 最大场强超过击穿阈值2×10⁷ V/m, 发生静电放电 (ESD) 的可能性较大. 随着入射电子能量的增加, 发生静电放电 (ESD) 的临界束流密度增大, 在能量为0.4 MeV时, 临界束流密度为6×10^-8 A/m². 当能量大于等于0.5 MeV时, 在束流密度为10^-9–10^-6 A/m²的范围内, 均不会发生静电放电 (ESD) . 该物理模型对于深入研究深层充放电效应、评估航天器在空间环境下 深层带电程度及防护设计具有重要的意义.关键词：高能电子辐射低密度聚乙烯(LDPE)介质深层充电电导特性

Influence of radiation electron energy on deep dielectric charging characteristics of low density polyethylene

The interactions between high-energy charged particles and spacecraft insulating materials can cause deep dielectric charging and discharging, leading to spacecraft anomalies. In this paper, we establish a unipolar charge transport physical model of deep dielectric charging, according to the charge distribution and energy deposition of incident electrons and nonlinear dark conductivity and radiation induced conductivity (RIC) of material. Under the irradiation of electrons with different energies (from 0.1 to 0.5 MeV), the charge transport process of low density polyethylene (LDPE) can be obtained through solving the charge continuity equation and Poisson's equation. The calculation results show that the maximum electric field decreases with the increase of radiation electron energy. When radiation electron energy is less than 0.3 MeV, the distribution of the maximum electric field is similar to the change of the electron beam density. When the electron beam density is more than 3×10^-9 A/m², the maximum electric field will be greater than breakdown threshold (about 2×10⁷ V/m), and it has higher risk of electrostatic discharge (ESD). With the increase of incident electron energy, the critical electron beam density will increase. When the radiation electron energy is 0.4 MeV, the critical electron beam density is 6×10^-8 A/m². When the radiation electron energy is more than 0.5 MeV, it seems that no electrostatic discharge (ESD) will occur in a range from 10^-9 to 10^-6 A/m². The physical model has the great significance for further studying deep dielectric charging, evaluating the charged degree of spacecraft in space environment and designing protection devices.