电子辐射下聚酰亚胺原位空间电荷的特性表征及机理研究

Space charge of dielectrics under electron irradiation is a key scientific issue for spacecraft charging and discharging phenomena. However, few types of research focus on the in-situ space charge behavior of dielectrics under space irradiation. The accurate characterization and properties of in-situ space charge in dielectrics are still lacking. This project proposes an investigation on the characterization of in-situ space charge and mechanism for polyimide under space electron irradiation. Based on pulsed electro-acoustic (PEA) principle, the in-situ space charge measurement platform would be designed and constructed. The output reference signal would be obtained by pulsed electron irradiation with low energy. Then the calibration of space charge distribution can be acquired using the reference signal and signal processing. After that, we obtain the favorable characterized results of space charge distribution under electron irradiation. The space charge properties of polyimide are studied by this measurement platform under and after irradiation, respectively. Then we can obtain the influence of the electron energy and density on the space charge accumulation/dissipation, electric field and potential properties. Through the quantum chemical calculation derived from the density functional theory (DFT), the electronic structure, including energy level, electric potential, localized state and trapping level of polyimide can be analyzed. Later, we can study the influence of chemical structure variation by electron irradiation on the localized state and trap information of polyimide. Incorporation of trap-controlled charge transport model of dielectric material, we try to clarify the space charge mechanism in polyimide under electron irradiation. This project can provide a theoretical basis and experimental support for the suppression of internal dielectric charging/discharging in space environment.

电子辐射下介质材料的空间电荷是航天器充放电的关键科学问题。然而目前辐射下介质原位空间电荷的研究鲜有报道，缺乏准确有效的原位空间电荷表征和特性研究，严重制约了对航天器介质充放电的深入认识。本项目围绕电子辐射下聚酰亚胺原位空间电荷的特性表征和机理展开研究，基于脉冲电声测试原理，设计并搭建电子辐射下原位空间电荷的测试和分析平台；通过真空环境中施加低能脉冲电子辐射获取参考信号并进行校准，获得良好的电子辐射下空间电荷表征结果。研究电子辐射期间和辐射后聚酰亚胺的空间电荷分布特性；获得电子辐射对其空间电荷积聚/消散、电场和电位的影响。通过基于密度泛函理论的量子化学计算方法获得聚酰亚胺的电子结构，研究其能级和电势分布，分析和获得电子辐射对聚酰亚胺微观局域态和陷阱能级的影响；结合介质材料陷阱调制的电荷输运模型，揭示电子辐射下聚酰亚胺的空间电荷机理，为抑制空间环境中航天器介质充放电提供理论基础和实验依据。

项目研究围绕太空环境下卫星介质材料在电子辐射下的充放电研究背景，针对电子辐射下介质材料的空间电荷关键科学问题，开展电子辐射下聚酰亚胺原位空间电荷的特性表征和机理研究。.本项目提出了聚酰亚胺介质材料电子辐射下的原位空间电荷表征方法，难点是电子辐射下PEA 测试装置的结构优化、信号校准和空间电荷分布信号处理方法，以及空间电荷积聚和消散的机理，采用了预加直流偏置和低能脉冲电子束的方法获得了聚酰亚胺的电子辐射的参考信号，解决了电子辐射下聚酰亚胺介质材料原位空间电荷分布的测试难题。通过测试平台研究获得电子辐射下聚酰亚胺的空间电荷积聚和消散特性；采用量子化学计算获得电子辐射对介质微观局域态或陷阱特性的影响，结合电荷输运模型，揭示电子辐射下聚酰亚胺的空间电荷机理。取得主要成果有：.（1）设计制造了电子辐射下原位PEA测试装置，优化了测试结构，实现了电子辐射下的原位空间电荷测试；.（2）采用高电压环电极和预加直流偏置的方法获得了聚酰亚胺空间电荷分布的参考信号；进行了测试信号的校准；.（3）搭建了采用脉冲电子束获得参考信号的电子辐射下原位PEA测试平台，获得了良好的空间电荷参考信号；.（4）测试分析了不同电子能量和束流下聚酰亚胺介质材料的空间电荷分布特性，获得了电子能量、束流密度对空间电荷积聚和消散的影响规律；.（5）研究了聚酰亚胺分子链的能级分布、电子密度分布和局域态特性，获得了聚酰亚胺本征化学基团引入的陷阱局域态特性，分析了陷阱深度对空间电荷的影响机理。.研究成果对测试和分析卫星介质材料高能电子辐射下空间电荷分布，研究介质材料深层带电特性，理解介质材料辐射下电荷积聚、衰减、电场畸变和电导特性具有重要的理论意义。项目提出的测试方法可准确测试辐射下介质内部电荷分布，用于研究辐射下带电特性，指导材料改性和开放，为抑制空间环境中航天器介质充放电提供理论基础和实验依据。