The Development Of The Surface Potential Measuring System Of Dielectric Under Eiectron Radiation And Thermal Cycle

The phenomenon of electrostatic discharge of dielectric in the aerospace environment is closely related to the surface potential distribution properties of dielectric,whether it is flashover along the vacuum interface with dielectric or breakdown caused by local field strength distortion.The multi-factor coupling of space electron irradiation,high vacuum and thermal cycling makes the mechanism of charge transport of the dielectric more complicated.It is difficult to obtain the surface potential distribution of the dielectric in the space environment by means of simulation.Therefore,the development of a surface potential measurement system combined electron irradiation and thermal cycling is of great significance to reveal the properties of potential distribution of dielectric in space environment,and also provides important data support for the study of charge transport mechanisms.In this paper,the work carried out for the development of a potential measurement system under electron irradiation and thermal cycling is as follows:Based on the working principle of the electron gun and the equation of electron motion trajectory the motion trajectory of the electrons in the electrostatic field and the electron energy are simulated,and the electron gun structure with an acceleration voltage of 1-10 kV is designed.At the same time,the vacuum system that satisfies the electron emission conditions was optimized.By designing an electron beam calibration test considering the secondary electron emission characteristics,the electron beam is calibrated to 0.07 nA/cm2-0.44 nA/cm2 when the input power is 80 W-120 W.The effectiveness of the developed electronic irradiation platform was verified.According to the design index of the vacuum thermal cycle test and the calculation of the vacuum heat leakage,the cold tank structure was optimized,and the thermal conductivity and thermal insulation performance of the temperature cycle test system were improved.A temperature control circuit was built,and a temperature cycle control program based on the Lab VIEW platform with hardware communication,data reading and writing,and temperature control functions was developed.It is verified by experiments that the system can achieve the function of accelerated thermal cycling at a temperature change rate of 10℃/min within-150℃ to+150℃ and the function of a simulated space thermal cycle function at a temperature change rate of 2℃/min within-29℃ to+71℃.A surface potential measurement platform of dielectric suitable for electron irradiation and temperature cycling was developed,and a shielding layer for the electrostatic probe was designed to reduce the interference of electron radiation on surface potential measurements.Developed the software for automatic measurement of surface potential under electron irradiation,and cooperated with the corresponding moving structure to realize automatic cycle measurement of surface potential.The surface potential distribution test of polyimide under different electron irradiation conditions and its interaction with thermal cycling was carried out,which verified the usability of the measurement system under different operating conditions,and preliminary obtained polyimide surface potential distribution properties under the electron irradiation and thermal cycling.