Observations of neutral depletion and plasma acceleration in a flowing high-power argon helicon plasma

Journal Article · Tue Jul 15 04:00:00 EDT 2008 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2950301· OSTI ID:21268944

Denning, C Mark; Wiebold, Matt; Scharer, John E ^[1]

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1. Electrical and Computer Engineering Department, University of Wisconsin-Madison, Engineering Research Building, 1500 Engineering Dr., Madison, Wisconsin 53704 (United States)

Neutral depletion effects are observed in a steady-state flowing argon helicon plasma with a magnetic nozzle for high rf input powers (up to 3 kW). Noninvasive diagnostics including 105 GHz microwave interferometry and optical spectroscopy with collisional-radiative modeling are used to measure the electron density (n{sub e}), electron temperature (T{sub e}), and neutral density (n{sub n}). A region of weak neutral depletion is observed upstream of the antenna where increasing rf power leads to increased electron density (up to n{sub e}=1.6x10{sup 13} cm{sup -3}) while T{sub e} remains essentially constant and low (1.7-2.0 eV). The downstream region exhibits profound neutral depletion (maximum 92% line-averaged ionization), where T{sub e} rises linearly with increasing rf power (up to 4.9 eV) and n{sub e} remains constrained (below 6.5x10{sup 12} cm{sup -3}). Flux considerations indicate accelerated plasma flow (Mach 0.24) through the antenna region due to an axial pressure gradient with reduced collisional drag from neutral depletion.

• OSTI ID: 21268944
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 7 Vol. 15; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ANTENNAS
ARGON
ELECTRON DENSITY
ELECTRON TEMPERATURE
INTERFEROMETRY
MICROWAVE RADIATION
NEUTRON SPECTROSCOPY
PLASMA ACCELERATION
PLASMA DIAGNOSTICS