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Title: Transition of window breakdown from vacuum multipactor discharge to rf plasma

Abstract

In high-power microwave systems, the transition of window breakdown from single surface vacuum multipactor discharge to rf plasma with increasing gas pressure is investigated using particle-in-cell simulations. An intermediate pressure regime where multipactor discharge and rf plasma coexist was found. The pressure range where the multipactor can be maintained is summarized in the plot of the secondary electron emission yield as a function of the gas pressure. As the gas pressure increases, electron-neutral collisions prevail against secondary electron emissions and the electron energy probability function changes from the bi-Maxwellian at low pressures to Druyvesteyn at high pressures as a result of the change in electron heating and cooling processes. The discharge formation time in argon, neon, and xenon is shown for different gas pressures. Different scaling laws in the discharge formation time are presented at low and high pressures, respectively.

Authors:
;  [1]
  1. Department of Nuclear Engineering, University of California, Berkeley, California 94720-1730 (United States)
Publication Date:
OSTI Identifier:
20860468
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 13; Journal Issue: 12; Other Information: DOI: 10.1063/1.2403782; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ARGON; ELECTRON COLLISIONS; ELECTRON EMISSION; ELECTRONS; HIGH-FREQUENCY DISCHARGES; MICROWAVE RADIATION; NEON; PLASMA; PLASMA PRESSURE; PLASMA SIMULATION; PROBABILITY; SCALING LAWS; XENON

Citation Formats

Kim, H. C., and Verboncoeur, J. P.. Transition of window breakdown from vacuum multipactor discharge to rf plasma. United States: N. p., 2006. Web. doi:10.1063/1.2403782.
Kim, H. C., & Verboncoeur, J. P.. Transition of window breakdown from vacuum multipactor discharge to rf plasma. United States. doi:10.1063/1.2403782.
Kim, H. C., and Verboncoeur, J. P.. Fri . "Transition of window breakdown from vacuum multipactor discharge to rf plasma". United States. doi:10.1063/1.2403782.
@article{osti_20860468,
title = {Transition of window breakdown from vacuum multipactor discharge to rf plasma},
author = {Kim, H. C. and Verboncoeur, J. P.},
abstractNote = {In high-power microwave systems, the transition of window breakdown from single surface vacuum multipactor discharge to rf plasma with increasing gas pressure is investigated using particle-in-cell simulations. An intermediate pressure regime where multipactor discharge and rf plasma coexist was found. The pressure range where the multipactor can be maintained is summarized in the plot of the secondary electron emission yield as a function of the gas pressure. As the gas pressure increases, electron-neutral collisions prevail against secondary electron emissions and the electron energy probability function changes from the bi-Maxwellian at low pressures to Druyvesteyn at high pressures as a result of the change in electron heating and cooling processes. The discharge formation time in argon, neon, and xenon is shown for different gas pressures. Different scaling laws in the discharge formation time are presented at low and high pressures, respectively.},
doi = {10.1063/1.2403782},
journal = {Physics of Plasmas},
number = 12,
volume = 13,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}
  • This paper analyzes the effects of the rf magnetic field and partial reflection of the circularly polarized electromagnetic wave on multipactor discharge on a dielectric. A statistical theory (taking into account the velocity spread of injected electrons) is constructed to evaluate the multipactor induced breakdown and saturation level. It is concluded that the spread of initial velocities considerably changes the condition for multipactor initiation in comparison with the dynamic approach. This effect is especially strong for the case of relatively low rf electric field amplitude (when the transit time essentially exceeds the rf period) and leads to the oscillation suppressionmore » of effective electron yield and to an increase in the threshold of multipactor growth. It is established that the rf magnetic field eliminates the upper boundary of the susceptibility diagram, while the low boundary almost remains unchanged. It is also found that the presence of partial reflection causes degradation of the saturation level (in comparison with the nonreflecting case) and results in decreasing of the characteristic time required to achieve the steady state.« less
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  • We are exploring a new approach for heavy-ion beam injection (e.g., into the relativistic heavy-ion collider at BNL), as well as new sources of intense high charge state ions to be mounted on a relatively low voltage platform for high energy ion implantation. While conventional metal vapor vacuum arc (Mevva) ion sources can produce up to hundreds of milliamps or more of several-times-ionized metal ions (e.g., U3+), the recent results from Batalin {ital et al.} indicate that the addition of an energetic electron beam may lead to considerably higher charge states. An alternative way to produce the electron beam ismore » where a Z-discharge plasma is used to enhance multiple ionization. As the vacuum arc plasma plume expands into a magnetized drift region, a Z-discharge is triggered in the drifting metal plasma. The ions are then extracted and analyzed using a time-of-flight system. We report initial results using these schemes with applied discharge and electron beam voltages from 1 to 2 kV. {copyright} {ital 1998 American Institute of Physics.}« less
  • The scaling laws for the initiation time of radio frequency (rf) window breakdown are constructed for three gases: Ar, Xe, and Ne. They apply to the vacuum, to the multipactor-triggered regime, and to the collisional rf plasma regime, and they are corroborated by computer simulations of these three gases over a wide range of pressures. This work elucidates the key factors that are needed for the prediction of rf window breakdown in complex gases, such as air, at various pressures.