An investigation into the cumulative breakdown process of polymethylmethacrylate in quasi-uniform electric field under nanosecond pulses

Zhao, Linjie; Su, Jiancang; Zhang, Xi Bo; Pan, Ya Feng; Wang, Li Min; Fang, Jin Peng; Sun, Xu Andy; Lui, Rui

doi:10.1063/1.4818437

Cited by 26 publications

(9 citation statements)

References 26 publications

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“…5(b) illustrates a space-charge field established above the dielectric surface. Consequently, the nonlinear space-charge field may exist at the dielectric-air interface for many HPM horn configurations during ultrafast HPM pulses and the mechanism is significantly different from the multipactor discharge [22][23][24][25][26] at the dielectric-vacuum interface of the HPM horn.…”

Section: Effects and Factors Of Surface Electron Emissionmentioning

confidence: 98%

Ultrafast high-power microwave window breakdown: Nonlinear and postpulse effects

et al. 2014

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The time- and space-dependent optical emissions of nanosecond high-power microwave discharges near a dielectric-air interface have been observed by nanosecond-response four-framing intensified-charged-coupled device cameras. The experimental observations indicate that plasma developed more intensely at the dielectric-air interface than at the free-space region with a higher electric-field amplitude. A thin layer of intense light emission above the dielectric was observed after the microwave pulse. The mechanisms of the breakdown phenomena are analyzed by a three-dimensional electromagnetic-field modeling and a two-dimensional electromagnetic particle-in-cell simulation, revealing the formation of a space-charge microwave sheath near the dielectric surface, accelerated by the normal components of the microwave field, significantly enhancing the local-field amplitude and hence ionization near the dielectric surface. The nonlinear positive feedback of ionization, higher electron mobility, and ultraviolet-driven photoemission due to the elevated electron temperature are crucial for achieving the ultrafast discharge. Following the high-power microwave pulse, the sheath sustains a glow discharge until the sheath collapses.

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Section: Effects and Factors Of Surface Electron Emissionmentioning

confidence: 98%

Ultrafast high-power microwave window breakdown: Nonlinear and postpulse effects

et al. 2014

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“…One rectangular waveguide connected the PS, and the other five ports were matched by HPM loads. The PS was then connected with a two-time flared circular horn with an aperture of 300 mm, where a periodic pattern surface was used to improve the breakdown threshold at the vacuum side of the dielectric window by suppressing multipactor discharge [28]- [31]. An SF6 gas-bag could be fixed outside the window to improve the air breakdown threshold [32], [33].…”

Section: B High Power Testsmentioning

confidence: 99%

A New Compact High-Power Microwave Phase Shifter

Chang

Guo

Tantawi

et al. 2015

IEEE Trans. Microwave Theory Techn.

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A new compact low-loss fast phase-shift high-power microwave (HPM) phase shifter (PS) is proposed, designed, and cold and high-power tested. Firstly, based on solving the scattering matrix and eigenvectors, we design a novel HPM dual circular polarizer, and then a dumbbell-like metal plug driven by a highspeed servomotor is used to slide a short circuit along the dual circular polarized port to adjust the output RF phase, which varies 180 by moving the plug with a quarter of the guided wavelength. The X-band PS has a total length of 9.5 cm and a power capacity achieved 300 MW at 30-ns HPM pulse. A fast phase shift of 310 was achieved within 0.1 s in test, a high precision of phase shift 1 can be realized, and the tested insertion loss was 0.15 dB.Index Terms-High power microwave (HPM), phase shifter (PS).

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“…Roth [10] and Chantrenne [11] first observed a bulk breakdown trace in a vacuum insulator ring, and they termed as the "worm-hole" effect due to a wormhole appearance, which means that the insulating material properties greatly determine whether bulk breakdown or flashover occurs. Afterwards, Liang et al [12,13] observed the same phenomenon under the application of impulses and considered that impulse waveform gives a great influence on the occurrence of the "worm-hole" phenomenon. Few literatures reported the effect of material ingredient and processing parameters on the flashover process which may be accompanied by the bulk breakdown due to "worm-hole" effect.…”

Section: Introductionmentioning

confidence: 95%

Wormholes effect in flashover process of alumina filled epoxy resin surfaces in SF<sub>6</sub>

Qin

et al. 2015

IEEE Trans. Dielect. Electr. Insul.

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Alumina filled epoxy resin is important insulating material, which discharge characteristics are greatly determined by its material properties. In this paper, the surface flashover characteristics of the epoxy resin with various alumina contents (250-400 phr) in 0.4 MPa SF6 are studied. The short-term and long-term withstand voltages and the application times are measured, and then the V-T characteristics are compared accordingly. The withstand voltage of the epoxy resin with certain alumina content decreases exponentially with time and the long-term withstand voltage is about 20-30% lower than the short-term withstand voltage. The discharge damages to alumina filled epoxy resin material are also studied through the carbonization traces and the microcosmic damage patterns. It is found that the epoxy resin with 350 phr alumina has the lowest short-term and long-term withstand voltages and most serious carbonizations according to the experimental results. The "wormholes" formation in the discharge and its effect in the flashover process are analyzed and discussed based on the carbonation traces and the microcosmic patterns. It is found that the flashover paths shift from creeping-discharge-based to bulk-breakdown-based due to wormholes effect with the increase of alumina content and the critical alumina content is about 300-350 phr.

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An investigation into the cumulative breakdown process of polymethylmethacrylate in quasi-uniform electric field under nanosecond pulses

Cited by 26 publications

References 26 publications

Ultrafast high-power microwave window breakdown: Nonlinear and postpulse effects

Ultrafast high-power microwave window breakdown: Nonlinear and postpulse effects

A New Compact High-Power Microwave Phase Shifter

Wormholes effect in flashover process of alumina filled epoxy resin surfaces in SF<sub>6</sub>

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