Theoretical and experimental studies on internal charging/discharging phenomena occurring spacecraft material

为了模拟空间辐射环境，安装了高真空室(2002)和电子枪(2003)。对Kapton和Teflon等几种介质材料进行了电子辐照试验，利用本课题组先前开发的测量技术获得了材料内部的电荷分布。对用于太阳能电池板盖板玻璃的玻璃材料也进行了试验。结果表明，介质材料内部存在一个电荷密度峰，电子辐照产生了较高的电场和电势。电荷的穿透深度随着入射电子能量的增加而加深。玻璃材料内部的电荷密度分布随组成的不同而不同，但这种分布与成分之间的明确关系尚未揭示。将使用所获得的数据来组织内部收费数据库。在理论方面，基于量子理论的考虑，建立了入射电子与构成介质材料的原子碰撞的物理模型。利用蒙特卡罗方法对该模型进行了数值模拟。根据统计估计跟踪注入到材料表面的每个电子，并对捕获的电子进行计数以构建电荷密度分布。2002年安装了一台基于PC的并行计算机来执行这一计算，因为这种类型的模拟需要巨大的内存和高CPU性能。模拟结果显示了电子的积累过程，但没有得到与实验结果相一致的电荷分布的定量结果。详细的研究表明，在碰撞过程中发生了过度电离，从而在辐照表面附近观察到了正电荷。

In order to simulate the space radiation environment, the high vacuum chamber (2002) and the electron gun (2003) were installed. Electron irradiation tests on several dielectric materials such as Kapton and Teflon were carried out and the charge distributions inside the materials were obtained using the measurement technique previously developed by the present research group. Tests on glass material used for the cover glass on solar panels were also carried out. The results indicate that there exists a peak of charge density inside the dielectric material and high electric field and electric potential are induced due to the electron irradiation. The penetration depth of the charge becomes deeper as the incident electron energy increases. The charge density profiles inside glass materials vary according to the composition, but clear relationship between the profile and the component has not been revealed. The internal charging database is going to be organized using the data obtained. As for theoretical point of view, the physical model for collision between incoming electrons and atoms consisting the dielectric material was constructed based on consideration of the quantum theory. Numerical simulations based on the model were carried out using the Monte-Carlo methodology. Each electron injected onto the material surface is tracked based on the statistical estimations, and the trapped electrons are counted to construct charge density distribution. A PC-based parallel computer was installed in 2002 to execute this calculation because this type of simulation requires huge memories and high CPU performance. The simulation results show the electron accumulation process, but quantitative agreement of charge profile compared to that obtained by the experiments were not obtained. The detailed investigation clarified that the excessive ionization occurred among the collision processes and thus the positive charge near the irradiated surface were observed.