Surface Structure Research Of Electrified Test Mass In Charge Management

Gravitational reference sensor,also known as inertial sensor（GRS）is a key payload for space gravitational wave detection,which serves as a reference for inertial flight and optical inspection,it requires acceleration noise perturbation better than3×10^-15m/s²/Hz^1/2.As the core of an inertial sensor,the test mass is suspended freely without contact in the electrode cage and is subject to the accumulation of charge on the surface by energetic particles in space.The charged test mass interacts with the magnetic and space electric fields and is disturbed by the Lorentz force and electrostatic force,so the charge on the surface needs to be managed or suppressed.The role of the charge management system is to control the amount of charge on the surface of the inspection mass,thereby reducing acceleration noise due to charge-related interference.According to the requirement of noise index allocation,the amount of residual charge on the test quality surface should be controlled at the level of 10^-13C.The use of ultraviolet discharge to achieve contactless electrostatic control is an effective way to achieve charge control,and the use of ultraviolet light-emitting diodes（UV-LED）is the main development direction for the application of charge management technology.In the thesis,the structural design of the charge management load and the performance study of the coating are investigated.Finally,experimental verification of the alternating current（AC）charge control method is carried out,key research elements include:（1）Design of charge management structure unit for cubic star to verify charge management provide technology for actual microsatellite piggyback,it is the first cubic star structure used in the space gravitational wave detection mission in China.The main role of the load is based on UV-LED light source high-frequency alternating charge management technology for on-orbit verification,through theoretical calculations and simulation of the load is continuously optimized.This thesis completes the optimal design of the load structure and carries out ground test experiments.（2）Study of the load test mass（TM）and the surface film layer of the electrodes to compare and optimise the selection of coating for charge control by the photoelectric effect.The paper investigates different coating materials and parameter properties for inspection quality surfaces.Two verified Au,Nb coatings and two Si C,Ti C coatings are selected for the experiments.The results showed that all four materials can be used as a choice for the occurrence of photoelectric effect coatings,the Au is preferred as the coating choice because of its higher work function than the other three and its own stable performance.（3）Experimental verification of the AC charge control method using UV-LED,using two Au-plated plates to simulate inspection quality and electrode charging and discharging experiments.The results show that the AC charge control method can achieve the inspection quality charging and discharging very well.Under a vacuum of3.2×10^-4Pa,the results show that the charging and discharging process from±5 V to 0V is achieved on the surface of the test mass at different duty cycles,and the charging and discharging rate varies linearly with the duty cycle,the charging rate is greater than the discharging rate.To provide management control method support for subsequent space validation charge management experiment construction.