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Energy and pitch distribution of naturally occurring, highly energized bulk ions in the RFP

Author: Jungha Kim
Requested Type: Poster Only
Submitted: 2014-05-30 22:31:47

Co-authors: J. K. Anderson, J. A. Reusch, S. J. Eilerman, W. J Capecchi

Contact Info:
University of Wisconsin-Madison
Chamberlin Hall 1150 Universit
Madison, Wisconsin   53706
United States

Abstract Text:
Magnetic reconnection events in the Reversed Field Pinch (RFP) are known to heat bulk ions. Recent experiments with injected test ions subject to an electric field generated during reconnection events indicate that ion runaway is an important mechanism for fast ions. This effect does not, however, explain the change in distribution of nearly Maxwellian bulk ions. When the Madison Symmetric Torus (MST) is operated near maximum current and low electron density, significant neutron flux is generated without the usage of neutral beam injection. The bulk ion distribution created in these plasmas is well-confined, presumably non-Maxwellian, and can be measured by the Advanced Neutral Particle Analyzer (ANPA). Measurements using the ANPA at both tangential and radial ports allow sampling of the bulk ion distribution at different viewing angles. Preliminary data show an energy distribution tail up to 20keV and a larger signal in the radial viewing port following a reconnection event, suggesting that the measured ions are mostly low pitch (ratio of parallel speed to total speed). The ions measured by the ANPA leave the plasma as neutrals after a charge exchange event, and their subsequent trajectories are very sensitive to the pitch and position of the ion before neutralization. Careful analysis of the full orbit, traced in three dimensions, identifies the types of ions that can be measured at both the radial and tangential viewing angles.

Characterization: 1.0

Comments:

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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