真空电子辐射环境中聚酰亚胺表面-表层电子行为及沿面放电机理研究

Surface discharge of dielectric material in vacuum electron radiation environment is a key scientific issue which restricts the development of spacecraft. However, surface discharge properties and mechanism under electron radiation are not detailed, owing to the complexity of surface discharge phenomenon. In the project, surface discharge mechanism of polyimide in the vacuum electron radiation environment has been explored from the perspective of the coupling of surface moving electrons (the initial electrons, the secondary electrons and the incident moving electrons) and surface-layer deposited electrons. Firstly, the influence of surface-layer deposited electrons on surface moving electrons and surface discharge have been studied by presetting quantitative electrons to the surface-layer and measuring the in-situ surface potential, radiation-induced conductivity and surface discharge voltage. By controlling the incident electron energy, beam current, time and sample temperature, surface discharge voltage of the dielectric during radiation has been measured, and the influence of surface moving electrons and surface-layer deposited electrons on surface discharge have been studied. Furtherly, the physical processes of surface electron behavior, surface-layer electron behavior and their coupling during surface discharge are analyzed theoretically, and the electron coupling model between dielectric surface and surface layer has been established. On this basis, effect of electron coupling between surface and surface-layer on surface discharge has been illuminated, and surface discharge mechanism in electron radiation environment has been revealed. The work will provide theoretical foundation for improving the surface flashover performance of dielectric in space radiation environment.

空间电子辐射环境中介质沿面放电是制约航天器发展的关键问题之一。然而电子辐射环境中沿面放电现象较为复杂，其特性和机理尚不完全清楚。本项目从介质表面运动电子（初始电子、二次电子和入射运动电子）和表层沉积电子耦合的角度，探讨电子辐射环境中聚酰亚胺沿面放电机理。通过向介质表层预置定量电子，测量辐射后原位表面电位、辐射诱导电导和沿面放电电压，研究表层沉积电子对表面运动电子及沿面放电的影响；通过控制入射电子能量、束流、时间和试样温度，测量辐射期间介质的沿面放电电压，研究表面运动电子和表层沉积电子对沿面放电的共同影响；理论分析沿面放电起始和发展过程中表面运动电子行为、表层沉积电子行为及二者耦合的物理过程，建立电子束/温度共同影响下介质表面-表层电子耦合模型；在此基础上，阐明表面-表层电子耦合对沿面放电的影响机制，揭示电子辐射环境中介质沿面放电机理，为空间辐射环境中沿面放电性能提升提供理论基础和实验依据。

空间电子束辐射下绝缘介质电荷沉积及放电问题是制约航天器发展的关键问题。不同于传统的真空沿面放电，真空电子束辐射环境中介质的沿面放电过程较为复杂，影响因素较多，导致其特性和机制尚不完全清楚。从本质上认识和理解多类别电荷耦合对沿面放电的影响机制，揭示其作用机理，对于空间绝缘介质沿面放电抑制措施的研究具有重要意义。本项目围绕空间辐照环境下绝缘介质电荷特性和放电问题，从模型和实验方面开展了相关研究工作。首先研究了电子束辐照下绝缘介质电荷沉积模型和特性研究，包括：建立了电子束辐照下聚合物介质电荷传导和沉积模型，计算分析了不同类型绝缘材料的电荷沉积分布；其次，采用空间电子辐射模拟系统对试样进行辐照处理，对比研究了电子束辐射前后聚酰亚胺的微观结构、介电性能、电荷传导特性和空间电荷特性，获得了电子束辐射对聚酰亚胺介电常数、介质损耗、沉积电荷、电荷传导和闪络电压等绝缘参数的演变规律；再次，研究了聚酰亚胺的表面陷阱特性，采用电晕充电和表面电位衰减法，结合等温表面电位衰减模型，计算分析了聚酰亚胺表面陷阱能级分布，并通过改变充电电压极性以及幅值，研究了电子陷阱和空穴陷阱特征；进一步，研究了聚酰亚胺表面电荷积聚对沿面放电的影响，分析了介质表面积聚电荷极性和数量对沿面闪络电压的影响规律；最后，拓展研究了绝缘隔板对“棒-板”间隙放电特性的试验及电场仿真，获得了绝缘隔板尺寸、位置、厚度、表面状态等对绝缘系统放电电压额影响，通过建立等尺寸几何模型，仿真计算了不同条件下绝缘系统的电场分布特性。本研究对于空间绝缘介质沿面闪络性能提升和绝缘材料抗内带电研究具有重要的意义。