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Title: Spherical ion oscillations in a positive polarity gridded inertial-electrostatic confinement device

A pulsed, positive polarity gridded inertial electrostatic confinement device has been investigated experimentally, using a differential emissive probe and potential traces as primary diagnostics. Large amplitude oscillations in the plasma current and plasma potential were observed within a microsecond of the discharge onset, which are indicative of coherent ion oscillations about a temporarily confined excess of recirculating electron space charge. The magnitude of the depth of the potential well in the established virtual cathode was determined using a differential emissive Langmuir probe, which correlated well to the potential well inferred from the ion oscillation frequency for both hydrogen and argon experiments. It was found that the timescale for ion oscillation dispersion is strongly dependent on the neutral gas density, and weakly dependent on the peak anode voltage. The cessation of the oscillations was found to be due to charge exchange processes converting ions to high velocity neutrals, causing the abrupt de-coherence of the oscillations through an avalanche dispersion in phase space.
Authors:
;  [1]
  1. Plasma Physics, School of Physics, University of Sydney, Camperdown, New South Wales 2006 (Australia)
Publication Date:
OSTI Identifier:
22227958
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 20; Journal Issue: 7; Other Information: (c) 2013 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; CHARGE EXCHANGE; ELECTRIC CURRENTS; ELECTRIC DISCHARGES; ELECTRONS; HYDROGEN; INERTIAL CONFINEMENT; IONS; LANGMUIR PROBE; OSCILLATIONS; PHASE SPACE; PLASMA DENSITY; PLASMA POTENTIAL; PLASMA PRODUCTION; PLASMA WAVES; SPACE CHARGE; SPHERICAL CONFIGURATION