Estimation of surface flashover threshold in vacuum: from multipactor to discharge plasma

Abstract

We propose a novel theoretical formula to estimate the surface flashover threshold in vacuum using the intrinsic properties of dielectric material as well as dielectric-vacuum configuration. The method is based on an above-surface model called secondary electron emission avalanche (SEEA), where flashover development can be divided into multipactor discharge, outgassing and an ionization avalanche which eventually leads to a plasma discharge. The transition from SEE-dominated regime to discharge plasma is supposed to be of significance where gas breakdown takes place within a nonuniform desorbed gas cloud in the vicinity of dielectric surface. Flashover occurs when specific space charge multiplication is achieved, yielding the critical pressure and breakdown voltage. The depiction of previous stages involves the secondary electron emission of dielectric materials, desorption and diffusion of adsorbed gas, ambient temperature, electrode structure, etc. Both particle-in-cell simulation and experiment data can corroborate the obtained theoretical results.

Modelling vacuum flashover mitigation with complex surface microstructure: mechanism and application

“…The theoretical flashover voltage has also been discussed as shown in (2) [17] V flashover = 3π 8 1 − e −3 P crit − kTn 0 kTε 0 γ 2Dlm e A 0…”

“…Due to fast electrons produced by the backscattering, the average electron velocity of SEs becomes higher, which leads to a greater charge density at the equilibrium state. The formula of the average charge density is shown in (1) [17].…”

“…Previous researchers have studied the flashover mechanism by the simulation as well as the theoretical work, here brief summaries of flashover stages and theoretical progresses are provided [8, 17, 33, 34]. A flashover process can be divided into three stages.…”

“…It has been known that the surface treatment, like surface roughness, fluorination and grooves, can significantly affect the formation of the surface discharge [14][15][16]. The multipactor and charging behaviours on a plain surface have been recently studied by Sun et al [17] showing that the secondary emission yield (SEY) curve of the material has a remarkable impact on the average charge density and the flashover voltage. Various methods have been used to suppress the charge accumulation as well as the surface flashover process.…”

UV-cured nanocomposite coating for surface charging mitigation and breakdown strength enhancement: exploring the combination of surface topographical structure and perfluorooctyl chain

“…We believe that this signicant suppression of surface charging in vacuum is an extremely important property for electrical/electronic equipment where SEE dominates the discharge process. 36 This journal is © The Royal Society of Chemistry 2020…”