Study On The Vacuum Surface Flashover Characteristics Of Polyimide At Cryogenic Temperature

With the rapid development of superconducting technology and aerospace technology, dielectric electrical properties at low temperature especially in areas of liquid nitrogen and liquid helium temperature receiving more and more attention, Currently polyimide and some other polymer materials are widely used in superconducting magnet systems, but the research for it at Cryogenic temperature in vacuum is rarely carried out,it didn’t show the mechanism how the temperature affect the flashover. So cryogenic temperature polyimide vacuum surface flashover research it has very important significance.On the basis of the existing cryogenic insulating material electrical properties testing device, improved high-voltage test equipment, improved test pressure introducing device, enrich the means of observation, observation of experimental phenomena using electrical signals and optical signalsUsing cryogenic insulating material electrical properties testing device, in the range of 25K-300K temperature zone, test the polyimide material at different temperatures, different pressure mode and different lighting conditions, through the polyimide amine material under low temperature vacuum surface flashover research, made the following conclusions.(1)Under the pressure of different ways polyimide vacuum surface flashover characteristic that the pressure test can be used to explain ETPR model, while the other three press-SEEA model more in line with that in the vacuum surface flashover test boosting process there is always the polarization process, the polarization process will affect the flashover occurs hypothesis model.(2)Studied temperature range 25K-300K polyimide vacuum surface flashover characteristics found adsorbed gas has an indispensable role in the flashover process. Polyimide material is present a minimum flashover voltage value at 225K, the reason is a polyimide material when the temperature of the y relaxation most intense. By changing the electrode electron emission, gas adsorption and dielectric parameters, the influence of temperature on the flashover in vacuum is complicated.(3)Polyimide under vacuum of different lighting conditions flashover test, explore the case having a free photoelectrons in the environment, flashover voltage variation, according to SEEA model, considered the main reason for this change is that the initial electron obtained way richer, and analyzes the reasons the test signal generating light in advance.