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Title: Impact of central ECCD on steady-state hybrid scenario in DIII-D

“Steady-state” hybrid plasmas in DIII-D with zero surface loop voltage have been maintained for up to two current relaxation times using 3.4 MW of central electron cyclotron current drive (ECCD). In addition to driving ≈0.2 MA of plasma current, central ECCD leads to significant changes in Alfvén eigenmode (AE) activity and thermal transport. For neutral-beam-only heating, strong AE activity is observed that causes a ∼35% degradation in the neutron rate. With central ECCD this AE activity is suppressed, replaced by a bursty energetic particle mode that appears more benign as the neutron rate is closer to the classical value. The electron thermal diffusivity increases by ≈50% for 2.4 MW of ECCD compared to neutral-beam-only cases. Fortunately, the global thermal confinement factor remains the same (H{sub 98y2}=1.4) as the higher thermal transport for P{sub EC}=2.4 MW hybrids is offset by the decreased fast ion transport resulting from AE suppression.
Authors:
; ; ; ;  [1] ; ;  [2] ;  [3] ;  [4] ;  [5]
  1. General Atomics, P.O. Box 85608, San Diego, CA (United States)
  2. Princeton Plasma Physics Laboratory, Princeton, NJ (United States)
  3. Princeton University, Princeton, NJ (United States)
  4. University of Wisconsin - Madison, Madison, WI (United States)
  5. Columbia University, New York, NY (United States)
Publication Date:
OSTI Identifier:
22496225
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1689; Journal Issue: 1; Conference: 21. topical conference on radio frequency power in plasmas, Lake Arrowhead, CA (United States), 27-29 Apr 2015; Other Information: (c) 2015 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; ALFVEN WAVES; BEAMS; COMPARATIVE EVALUATIONS; DOUBLET-3 DEVICE; ECR CURRENT DRIVE; EIGENFREQUENCY; ELECTRIC CURRENTS; ELECTRIC POTENTIAL; ELECTRONS; HEAT TRANSFER; ICR HEATING; INHIBITION; NEUTRONS; PARTICLES; PLASMA; STEADY-STATE CONDITIONS; THERMAL DIFFUSIVITY