DC surface flashover characteristics of polyimide in vacuum under electron beam irradiation

Abstract

In order to avoid the surface discharge of sensitive components on spacecraft, it is very important to understand the mechanism of surface flashover characteristics of the insulator materials, such as polyimide (PI). This paper studied the influence of electron beam irradiation on the negative polarity dc surface flashover characteristics of PI plate specimen in vacuum. Results showed that the flashover voltage under 0.5-40 keV electron beam irradiation is enhanced compared to none irradiation situation. The flashover voltage increased at first then decreased with the increase of the electron beam energy, reaching maximum at 20 keV. And under the constant electron beam energy irradiation, the voltage decreased with the increase of the beam density. The experiments suggest that the negative space charge of cathode triple junction (CTJ), radiation-induced conductivity (RIC) and radiation degradation are important reasons for the rise of flashover voltage under various radiation electron beam energy. Besides, the low energy primary electrons play critical roles in the reduction of surface flashover voltage under different beam density.

Improvement of surface flashover in vacuum

“…Fujii et al study the surface flashover characteristics of printed circuit boards in aircraft and believe that the increase in electron beam energy would cause the surface flashover voltage to decrease [110,111]. Zheng X. et al also study the impact of different energy electron beams on the surface flashover characteristics and think that the space negative charge of CTJ, radiation-induced conductivity and radiation degradation are the important factors to enhance surface flashover voltage under different radiation electron beam energies [112][113][114]. At the same time, electron beam irradiation treatment can also be used as a treatment method for insulator surface to improve surface flashover voltage, when irradiation conditions are appropriate in certain range.…”

Radiation electron trajectory modulated DC surface flashover of polyimide in vacuum

“…Some irradiation electrons can deposit in the surface layer of dielectric which called the deposited electrons, while others continuously irradiate the dielectric surface which called the kinetic electrons [11,17]. For these two types of electrons, several experimental investigations concerning the surface flashover properties under various energies, fluxes and incident angles of electron irradiation were carried out [11,[18][19][20]. It was found that the deposited electrons establish the self-built electric field.…”

Deposition of SiCxHyOzthin film on epoxy resin by nanosecond pulsed APPJ for improving the surface insulating performance

“…A substantial number of researches have been demonstrated that the surface modification can accelerate the surface charge dissipation and improve the insulation properties of epoxy resin [6][7][8][9][10]. The surface modification can be achieved by many chemical or physical methods, including direct fluorination [11][12][13], nanoparticles doping [14,15], electron beam irradiation [16,17], heat treatment [18] and Cr 2 O 3 coating treatment [7], etc. However, above methods are still difficult to be widely used in industrial applications due to expensive equipment, complex processes or exhaust gas emission.…”