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Fast ion beta limit measurements by collimated neutron detection in the MST

Author: William J Capecchi
Requested Type: Poster Only
Submitted: 2014-05-30 13:52:29

Co-authors: S.J.Eilerman, J.A.Reusch, J.J.Koliner, J.K.Anderson, L.Lin, J.Clark, D.Liu

Contact Info:
UW Madison
1150 University Ave
Madison, WI   53703
USA

Abstract Text:
Fast ion orbits in the reversed field pinch (RFP) magnetic configuration are well ordered and have low orbit loss, even considering the stochasticity of the magnetic field generated by multiple tearing modes. Purely classical TRANSP modeling of a 1MW tangentially injected hydrogen neutral beam in MST deuterium plasmas predicts a core-localized fast ion density that can be up to 25% of the electron density and a fast ion beta of many times the local thermal beta. However, neutral particle analysis (NPA) of an NBI-driven mode (presumably driven by a fast ion pressure gradient) clearly shows transport of core-localized fast ions and a saturated fast ion density. The TRANSP modeling is presumed valid until the onset of the bema driven mode and gives an initial estimate of the volume-averaged fast ion beta in the range of 1-2% (local core value up to 10%). The development of a collimated neutron detector for fusion product profile measurements will provide information on the energy and spatial distributions of fast ions which will allow for independent measurements of the fast ion beta to be compared with TRANSP modeling, as well as shed light on the behavior of fast ion transport during onset of NBI-driven modes. Upcoming experiments will further investigate the empirical fast ion beta limit through the use of a deuterium bema into deuterium plasma which will allow for the NPA and neutron flux signals to provide a local and global fast ion beta measurement respectively.

Characterization: 1.2,2.0

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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