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Title: Measurements of an expanding surface flashover plasma

A better understanding of vacuum surface flashover and the plasma produced by it is of importance for electron and ion sources, as well as advanced accelerators and other vacuum electronic devices. This article describes time-of-flight and biased-probe measurements made on the expanding plasma generated from a vacuum surface flashover discharge. The plasma expanded at velocities of 1.2–6.5 cm/μs, and had typical densities of 10{sup 10}–10{sup 12} cm{sup −3}. The expansion velocity of the plasma leading edge often exhibited a sharp increase at distances of about 50 mm from the discharge site. Comparison with biased-probe data suggests that, under most conditions, the plasma leading edge was dominated by negative ions, with the apparent increase in velocity being due to fast H{sup −} overtaking slower, heavier ions. In some cases, biased-probe data also showed abrupt discontinuities in the plasma energy distribution co-located with large changes in the intercepted plasma current, suggesting the presence of a shock in the leading edge of the expanding plasma.
Authors:
 [1]
  1. Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523 (United States)
Publication Date:
OSTI Identifier:
22275516
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 19; 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; ANIONS; COMPARATIVE EVALUATIONS; ELECTRIC CURRENTS; ELECTRONS; ENERGY SPECTRA; FLASHOVER; HEAVY IONS; PLASMA; PLASMA DENSITY; PLASMA DIAGNOSTICS; PLASMA EXPANSION; PROBES; TIME-OF-FLIGHT METHOD