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Title: High efficiency off-axis current drive by high frequency fast waves

Modeling work shows that current drive can be done off-axis with high efficiency, as required for FNSF and DEMO, by using very high harmonic fast waves (“helicons” or “whistlers”). The modeling indicates that plasmas with high electron beta are needed in order for the current drive to take place off-axis, making DIII-D a highly suitable test vehicle for this process. The calculations show that the driven current is not very sensitive to the launched value of n{sub ∥}, a result that can be understood from examination of the evolution of n{sub ∥} as the waves propagate in the plasma. Because of this insensitivity, relatively large values (∼3) of n{sub ∥} can be launched, thereby avoiding some of the problems with mode conversion in the boundary found in some previous experiments. Use of a traveling wave antenna provides a very narrow n{sub ∥} spectrum, which also helps avoid mode conversion.
Authors:
; ;  [1] ; ;  [2]
  1. General Atomics, PO Box 85608, San Diego, California 92186-5608 (United States)
  2. Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (United States)
Publication Date:
OSTI Identifier:
22264087
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1580; Journal Issue: 1; Conference: 20. topical conference on radiofrequency power in plasmas, Sorrento (Italy), 25-28 Jun 2013; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DOUBLET-3 DEVICE; EFFICIENCY; MODE CONVERSION; PLASMA; SIMULATION; SPECTRA; TRAVELLING WAVES