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Title: Penetration of lower hybrid current drive waves in tokamaks

Lower hybrid (LH) ray propagation in toroidal plasma is shown to be controlled by combination of the azimuthal spectrum launched by the antenna, the poloidal variation of the magnetic field, and the scattering of the waves by the drift wave fluctuations. The width of the poloidal and radial radio frequency wave spectrum increases rapidly as the rays penetrate into higher density and scatter from the drift waves. The electron temperature gradient (ETG) spectrum is particularly effective in scattering the LH waves due to its comparable wavelengths and phase velocities. ETG turbulence is also driven by the radial gradient of the electron current profile giving rise to an anomalous viscosity spreading the LH driven plasma currents. The LH wave scattering is derived from a Fokker-Planck equation for the distribution of the ray trajectories with diffusivities derived from the drift wave fluctuations. The condition for chaotic diffusion for the rays is derived. The evolution of the poloidal and radial mode number spectrum of the lower hybrid waves are both on the antenna spectrum and the spectrum of the drift waves. Antennas launching higher poloidal mode number spectra drive off-axis current density profiles producing negative central shear [RS] plasmas with improved thermal confinementmore » from ETG transport. Core plasma current drive requires antennas with low azimuthal mode spectra peaked at m = 0 azimuthal mode numbers.« less
Authors:
 [1] ;  [2] ; ; ; ; ;  [3]
  1. The University of Texas at Austin, Austin, Texas 78712 (United States)
  2. (France)
  3. CEA, IRFM, F-13108 Saint-Paul-Lez Durance (France)
Publication Date:
OSTI Identifier:
22218428
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 20; Journal Issue: 11; Other Information: (c) 2013 © 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; COMPARATIVE EVALUATIONS; CURRENT DENSITY; ELECTRIC CURRENTS; ELECTRON TEMPERATURE; ELECTRONS; FOKKER-PLANCK EQUATION; ION TEMPERATURE; LOWER HYBRID CURRENT DRIVE; LOWER HYBRID HEATING; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PHASE VELOCITY; PLASMA CONFINEMENT; PLASMA DRIFT; PLASMA SIMULATION; SHEAR; TEMPERATURE GRADIENTS; TOKAMAK DEVICES; VISCOSITY; WAVE PROPAGATION