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Title: Emissive sheath measurements in the afterglow of a radio frequency plasma

The difference between the plasma potential and the floating potential of a highly emissive planar surface was measured in the afterglow of a radio frequency discharge. A Langmuir probe was used to measure the electron temperature and an emissive probe was used to measure the spatial distribution of the potential using the inflection point in the limit of zero emission technique. Time-resolved measurements were made using the slow-sweep method, a technique for measuring time-resolved current-voltage traces. This was the first time the inflection point in the limit of zero emission was used to make time-resolved measurements. Measurements of the potential profile of the presheath indicate that the potential penetrated approximately 50% farther into the plasma when a surface was emitting electrons. The experiments confirmed a recent kinetic theory of emissive sheaths, demonstrating that late in the afterglow as the plasma electron temperature approached the emitted electron temperature, the emissive sheath potential shrank to zero. However, the difference between the plasma potential and the floating potential of a highly emissive planar surface data appeared to be much less sensitive to the electron temperature ratio than the theory predicts.
Authors:
;  [1] ; ;  [2] ;  [3]
  1. Nuclear Engineering and Engineering Physics, University of Wisconsin—Madison, Madison, Wisconsin 53706 (United States)
  2. Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)
  3. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States)
Publication Date:
OSTI Identifier:
22252125
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 21; Journal Issue: 1; 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; AFTERGLOW; APPROXIMATIONS; ELECTRON TEMPERATURE; LANGMUIR PROBE; PLASMA; PLASMA POTENTIAL; POTENTIALS; RADIOWAVE RADIATION; SPATIAL DISTRIBUTION; SURFACES; TIME RESOLUTION