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Title: Diagnostics of fast formation of distributed plasma discharges using X-band microwaves

We present measurements of high power (25.7 kW), pulsed (800 ns), X-band (9.382 GHz) microwave breakdown plasmas, including reflected power measurements, mixer reflected amplitude and phase measurements, optical emission spectroscopy (OES) measurements, and an analysis that estimates the average electron density and electron temperature. In addition, a six-region, 1-D model was used to determine plasma parameters and compare with the experimental results. The experimental results show that using a 43 Hz repetition rate with an 800 ns pulse, fast (<300 ns) breakdown occurs in neon measured between 50 Torr and 250 Torr, producing plasma that lasts for over 7 μs. It also leads to large microwave reflections (70%) and an on-axis transmission attenuation of −15 dB. Moreover, a comparison between a 1-D model and mixer measurements shows that at 100 Torr, the neon plasma electron density peaked at 2 × 10{sup 12} cm{sup −3}, and the electron temperature peaked at 2.5 eV assuming a Maxwellian distribution. The addition of 2% Ar in Ne reduced the breakdown time and allowed OES measurements to determine the effective electron temperature. OES measurements of mixed (Ne/Ar: 98/2) argon line ratios (420.1 nm/419.8 nm) were used to determine the average effective electron temperature T{sub e(eff)} = 1.2 eV, averaged over the entire 7μs plasma lifetime. They indicate that the electron energy distribution was not Maxwellianmore » but, instead, tended towards a Druyvesteyn character.« less
Authors:
; ; ;  [1]
  1. Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin 53705 (United States)
Publication Date:
OSTI Identifier:
22278060
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 6; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ARGON; COMPARATIVE EVALUATIONS; ELECTRIC DISCHARGES; ELECTRON DENSITY; ELECTRON TEMPERATURE; ELECTRONS; EMISSION SPECTROSCOPY; ENERGY SPECTRA; MICROWAVE RADIATION; NEON; PLASMA; PLASMA DIAGNOSTICS; PLASMA SIMULATION