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Title: Fast excitation of geodesic acoustic mode by energetic particle beams

A new mechanism for geodesic acoustic mode (GAM) excitation by a not fully slowed down energetic particle (EP) beam is analyzed to explain experimental observations in Large Helical Device. It is shown that the positive velocity space gradient near the lower-energy end of the EP distribution function can strongly drive the GAM unstable. The new features of this EP-induced GAM (EGAM) are: (1) no instability threshold in the pitch angle; (2) the EGAM frequency can be higher than the local GAM frequency; and (3) the instability growth rate is much larger than that driven by a fully slowed down EP beam.
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  1. Institute of Physics, Chinese Academy of Science, Beijing (China)
  2. Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou (China)
  3. ENEA C. R. Frascati, C.P. 65, 00044 Frascati (Italy)
  4. (China)
Publication Date:
OSTI Identifier:
22489989
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 12; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; DISTRIBUTION FUNCTIONS; EXCITATION; GEODESICS; INCLINATION; INSTABILITY GROWTH RATES; LHD DEVICE; MATHEMATICAL SPACE; PARTICLE BEAMS; SOUND WAVES; VELOCITY