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Title: First Direct Observation of Runaway-Electron-Driven Whistler Waves in Tokamaks

DIII-D experiments at low density (n e ~10 19 m -3) have directly measured whistler waves in the 100– 200 MHz range excited by multi-MeV runaway electrons. Whistler activity is correlated with runaway intensity (hard x-ray emission level), occurs in novel discrete frequency bands, and exhibits nonlinear limitcycle- like behavior. The measured frequencies scale with the magnetic field strength and electron density as expected from the whistler dispersion relation. The modes are stabilized with increasing magnetic field, which is consistent with wave-particle resonance mechanisms. The mode amplitudes show intermittent time variations correlated with changes in the electron cyclotron emission that follow predator-prey cycles. These can be interpreted as wave-induced pitch angle scattering of moderate energy runaways. The tokamak runaway-whistler mechanisms have parallels to whistler phenomena in ionospheric plasmas. The observations also open new directions for the modeling and active control of runaway electrons in tokamaks.
Authors:
 [1] ;  [2] ;  [3] ;  [2] ;  [4] ;  [3] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [7] ;  [8] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of California, Irvine, CA (United States)
  3. General Atomics, San Diego, CA (United States)
  4. Oak Ridge Associated Univ., Oak Ridge, TN (United States)
  5. Univ. of California, San Diego, CA (United States)
  6. Univ. of Texas, Austin, TX (United States)
  7. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  8. XCEL Engineering, Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
FC02-04ER54698; FG02-07ER54917; SC0016268; AC05-060R23100; FG03-94ER54271; AC02-09CH11466; AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 120; Journal Issue: 15; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
General Atomics, San Diego, CA (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
OSTI Identifier:
1437151
Alternate Identifier(s):
OSTI ID: 1432738