Effect of Test Mass Position on the UV Discharge Rate of Space Inertial Sensor

The free-floating test mass (TM) inside the space inertial sensor will be charged from cosmic radiation, limiting the sensitivity of gravitational wave detections. Previous studies propose contactless charge control by using the UV light, but the effect of TM position has not been analyzed. This study quantitatively evaluates the effect of TM position on discharge rate based on finite element simulation. The results show that the relative change in discharge rate remains within 1% under the maximum offsets of the TM position when electrode and housing (EH) illumination and the maximum relative change in discharge rate are approximately 3% in the presence of a −0.1-mm translational offset of the TM along the Z-axis under TM illumination. This study investigates the effect of the TM position on UV discharging, which provides a theoretical foundation of high-precision charge control for space inertial sensors.