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epr2014_rev2.pdf2014-08-20 14:05:06Andrew Seltzman

Electron Bernstein Wave Studies in MST

Author: Andrew H Seltzman
Requested Type: Poster Only
Submitted: 2014-05-30 14:18:46

Co-authors: J. K. Anderson, C. B. Forest, P. Nonn, M. Thomas

Contact Info:
University of Wisconsin Madison
1150 University Ave
Madison, Wi   53706

Abstract Text:
The overdense condition in an RFP prevents electromagnetic waves from propagating past the edge, however use of the electron Bernstein wave (EBW) has the potential to heat and drive current in the plasma. A 450kw RF source that generates 2ms pulses at 5.55GHz and an antenna system with suitable power handling capability has been constructed. Testing of an EBW waveguide antenna system for use in heating experiments is underway. Design and implementation of a suitable launch structure is challenging in the RFP for several reasons. Due to the magnetic field geometry, it is necessarily a low-field-side launch, the close-fitting conducting shell requires minimum port hole size, the port hole leads to local magnetic field perturbation that affects resonance condition, and there is a very small (zero) vacuum gap between the shell and plasma and hence substantial antenna-plasma interaction. The antenna structure consists of a cylindrical molybdenum antenna with a boron nitride cap and a quartz window followed by a cylindrical to rectangular transition. The waveguide is filled with pressurized SF6 to prevent arcing, while the antenna is maintained at machine vacuum. Testing of coupling into an over dense plasma at various powers and plasma currents has commenced. Use of a multi-cord soft x-ray camera and spectrum analyzer connected to a receiving probe antenna are used to look for evidence of electron heating and coupling effects. Power handling tests on the antenna are used to determine the maximum capabilities of the system without arcing.

Work supported by USDOE.

Characterization: 4.0

Place with MST posters

Workshop on Exploratory Topics in Plasma and Fusion Research (EPR) and US-Japan Compact Torus (CT) Workshop
August 5-8, 2014
Madison, Wisconsin

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