Secondary Electron Emission and Trap State In Situ Combined (SETiC) Measurement for Spacecraft ESD Protection

Spacecraft charging and electrostatic discharge (ESD) arise when its components are exposed to space plasmas and beams, posing severe risks to onboard electronic, communication, insulation and power systems. Secondary electron emission (SEE) and trap state (TS) are two critical and interrelated properties of spacecraft materials that govern the surface charging and ESD behaviors. However, in existing studies, SEE and TS are typically measured separately under different experimental conditions, making it difficult to establish a direct correlation between these two coupled quantities. Here, a state-of-the-art secondary electron emission and trap state in-situ combined (SETiC) measurement instrument is developed, across a wide range of temperature (153-573 K), electron energy (20 eV-50 keV), and under high vacuum conditions (~10-6Pa). The key design includes a cylindrical SETiC measurement chamber with three measurement positions, a moveable, four-layer spherical collector driven by a four-axis translation stage, and a temperature control system consisting of cryogenic and filament heating systems. TS density and energy level distributions are assessed via the isothermal surface potential decay method. The main SETiC measurement chamber is connected to an auxiliary chamber for real-time spacecraft charging and ESD experiment, via a transfer chamber and magnetic couplings. The proposed SETiC technique provides rapid, accurate SEE-TS measurement for a variety of spacecraft materials, supporting modeling of spacecraft charging and ESD, as well as the development of advanced ESD protection strategies.