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Title: The influence of ions and the induced secondary emission on the nanosecond high-gradient microwave breakdown at metal surface

Abstract

The mechanism of ultrafast breakdown at metal/vacuum interface in the high-power microwave waveguides is studied. In order to realize the nanosecond discharge, the required ambient gas pressure above the metal surface is approximately calculated as high as several Torr due to the low ionization-rate for high-energy electrons and short pulse. The local high pressure may come from the evaporated microscopic protrusions due to Joule heating and gas desorption. Besides, ions accelerated by the ambient space charge field could obtain sufficient high energy to collide and sputter the metal atoms to increase the ambient pressure. The positive feedbacks during the rapid discharge are studied by particle-in-cell simulation. The relatively high-energy ions could generate secondary electrons. It is shown that, as the positive feedback, the secondary electrons induce the gas desorption and stronger ionization, resulting in ion and electron density increasing as well as sheath field further increasing. As a result, more higher-energy ions bombard metal surface, leading to higher secondary electron yield and higher density plasma generated to cut off the microwave transmission finally. These nonlinear courses realize the ultrafast discharge in waveguides.

Authors:
 [1];  [2];  [3]; ; ; ; ; ; ;  [1]
  1. Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024 (China)
  2. (China)
  3. Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an, Shaanxi 710049 (China)
Publication Date:
OSTI Identifier:
22490951
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 6; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BREAKDOWN; DESORPTION; ELECTRON DENSITY; ELECTRONS; IONIZATION; JOULE HEATING; METALS; MICROWAVE RADIATION; PLASMA DENSITY; PLASMA SIMULATION; PRESSURE RANGE MEGA PA 10-100; SECONDARY EMISSION; SPACE CHARGE; SPUTTERING; SURFACES; TRANSMISSION; WAVEGUIDES

Citation Formats

Chang, C., Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, Liu, C. L., Chen, C. H., Sun, J., Liu, Y. S., Guo, L. T., Cao, Y. B., Wang, Y., and Song, Z. M. The influence of ions and the induced secondary emission on the nanosecond high-gradient microwave breakdown at metal surface. United States: N. p., 2015. Web. doi:10.1063/1.4922759.
Chang, C., Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, Liu, C. L., Chen, C. H., Sun, J., Liu, Y. S., Guo, L. T., Cao, Y. B., Wang, Y., & Song, Z. M. The influence of ions and the induced secondary emission on the nanosecond high-gradient microwave breakdown at metal surface. United States. doi:10.1063/1.4922759.
Chang, C., Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, Liu, C. L., Chen, C. H., Sun, J., Liu, Y. S., Guo, L. T., Cao, Y. B., Wang, Y., and Song, Z. M. Mon . "The influence of ions and the induced secondary emission on the nanosecond high-gradient microwave breakdown at metal surface". United States. doi:10.1063/1.4922759.
@article{osti_22490951,
title = {The influence of ions and the induced secondary emission on the nanosecond high-gradient microwave breakdown at metal surface},
author = {Chang, C. and Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an, Shaanxi 710049 and Liu, C. L. and Chen, C. H. and Sun, J. and Liu, Y. S. and Guo, L. T. and Cao, Y. B. and Wang, Y. and Song, Z. M.},
abstractNote = {The mechanism of ultrafast breakdown at metal/vacuum interface in the high-power microwave waveguides is studied. In order to realize the nanosecond discharge, the required ambient gas pressure above the metal surface is approximately calculated as high as several Torr due to the low ionization-rate for high-energy electrons and short pulse. The local high pressure may come from the evaporated microscopic protrusions due to Joule heating and gas desorption. Besides, ions accelerated by the ambient space charge field could obtain sufficient high energy to collide and sputter the metal atoms to increase the ambient pressure. The positive feedbacks during the rapid discharge are studied by particle-in-cell simulation. The relatively high-energy ions could generate secondary electrons. It is shown that, as the positive feedback, the secondary electrons induce the gas desorption and stronger ionization, resulting in ion and electron density increasing as well as sheath field further increasing. As a result, more higher-energy ions bombard metal surface, leading to higher secondary electron yield and higher density plasma generated to cut off the microwave transmission finally. These nonlinear courses realize the ultrafast discharge in waveguides.},
doi = {10.1063/1.4922759},
journal = {Physics of Plasmas},
number = 6,
volume = 22,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}
  • Dielectric window breakdown, whose mechanism is not thoroughly understood, is a major factor of limiting the transmission and radiation of high-power microwave on the order of 1 GW. In this paper, a one-dimensional fluid-like sheath model is developed to investigate the sheath structures formed at different gas pressures. The dominant processes during the surface flashover are isolated by this model. In vacuum, electron multipactor is self-sustained by secondary electron emission, a positive space-charge potential is formed on the dielectric surface. With increasing gas pressure, electron-neutral ionization prevails against secondary electron emission. The multipactor effect is suppressed by the shielding ofmore » plasma electrons. This leads to the sheath potential changing gradually from a positive space-charge potential to a negative space-charge potential. For argon gas pressure lower than 14 Torr, the sheath is space charge limited. A potential minimum could be formed in front of the dielectric which traps secondary electrons emitted from the wall. With the higher argon gas pressure, the number density of ions becomes comparable to that of electrons, all surface produced electrons are accelerated toward the presheath region. Therefore, the normal sheath is formed and the resulting surface flashover on the dielectric surface becomes rf-driven volumetric breakdown.« less
  • Abstract not provided.
  • We demonstrate that nonequilibrium carrier dynamics play a significant role in nanosecond laser-induced electron emission from semiconductor surfaces. Surface emission current and electron yields due to thermionic and photoelectric effects are calculated for a 2 ns laser pulse irradiation, with fluences below the threshold for melting. The photoelectric effect is found to dominate electron emission only at low fluences, whereas thermionic emission from interband absorption is responsible for electron emission at high incident fluences. The results present a satisfactory interpretation of experimental observations for nanosecond laser-induced electron emission from silicon. {copyright} {ital 1998 American Institute of Physics.}