New development of microstack insulator technology

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.

Section: Assumption and Possible Discrepancymentioning

confidence: 99%

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

Sun¹,

Song²,

Guo³

et al. 2018

“…After 30 min of plasma treatment in figure 7(d), the electric field was uniformly distributed between the electrodes, and the highest field intensity dropped to 5 × 10 6 V m −1 , which contributed to the enhancement of flashover voltage. However, when the surface resistivity of PTFE is lower, a larger leakage current will be generated, which will not only intensify the surface discharge, but also promote the gas desorption on the dielectric surface by current heating [46], thus accelerating the development of surface flashover. Therefore, DC flashover voltage had less promotion after plasma treatment, which changed little and became stable when the treatment time was 32 min and 48 min.…”

Section: Discussionmentioning

confidence: 99%

Improvement of surface insulating performance for polytetrafluoroethylene film by atmospheric pressure plasma deposition

Ren

Chen

Wang

et al. 2023

The surface flashover phenomenon across vacuum-dielectric interface severely limits the service life and operational reliability of high voltage electrical equipment. The surface modification by atmospheric pressure plasma treatment is a promising method to improve the surface insulating performance of polymers. In order to explore the effect mechanism of plasma processing on the vacuum flashover characteristics of polymer materials, the atmospheric pressure plasma deposition was used to treat polytetrafluoroethylene (PTFE) film. The surface parameters under different processing conditions, such as surface chemical composition, surface resistivity, surface charge decay and trap distribution, were tested and analyzed. The space charge distribution of PTFE and the flashover voltage in vacuum were measured. The results show that Si-O-Si and Si-OH groups are introduced on the surface of PTFE, and the characteristic peaks of PTFE are gradually weakened with the increase of processing time. The surface trap density increases and more traps with lower energy level arise with longer processing time. The plasma deposition changes the space charge distribution in PTFE body, and leads to positive charge accumulation inside the sample. The flashover field strength respectively increases by 15% and 70% in direct current (DC) voltage and microsecond pulse voltage afrter plasma deposition. The rapid dissipation of surface charge is the main reason for pulse flashover voltage enhancement, while the increase of surface leakage current due to lower surface resistivity and space charge accumulation in PTFE body make the DC flashover voltage reach the saturation point. Therefore the surface insulating and body performance of polymer materials after plasma modification processing should be considered comprehensively based on different applications.

“…For another, electron-induced outgassing during flashover process might be impactful. The source of released gases during flashover includes the desorbed gas from the surface of insulator and electrode, the evaporation or decomposition of high polymer material, and the escape of the dissolved gases [31]. For organic insulators, the additional hydrocarbons were found which they attributed to decomposition of the insulator surface layers [14,32].…”

Section: Modulation Of DC Surface Flashover In Vacuum By Electron Tra...mentioning

confidence: 99%

Radiation electron trajectory modulated DC surface flashover of polyimide in vacuum

Wang¹,

Zheng²,

Li³

et al. 2022

Improving surface flashover voltage on vacuum-dielectric interface irradiated by electrons is a long-standing challenge for developing high-voltage and high-power spacecraft technology. The basic issue is understanding the role of radiation electrons in the process of surface flashover. In this paper, a “3-segment” curve concerning the surface flashover properties under electron irradiation is discovered experimentally. As the gap distance of electrodes increase, the surface flashover voltage of polyimide during electron irradiation presents a trend of firstly increasing, then decreasing, and finally stabilizing. According to the simulation of the trajectory distribution for kinetic electrons, this trend is found to correspond with three typical stages respectively. In stage A, the kinetic electrons are completely deflected and the varying electrode parameters mainly affect the electric field distribution. In stage B, the kinetic electrons can irradiate the part of polyimide. The promoting effect of those electrons on flashover process enhance with the enlargement of the irradiated region. In stage C, trajectories are no longer seriously deflected and the role of kinetic electrons do not vary with electrode parameters. Combining with the results above, a model with combined effects of both kinetic and deposited electrons on surface flashover in vacuum is thus proposed, base on which the guidance for the methods of improving surface flashover voltage during electron irradiation is provided.