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Title: Full-wave Electromagnetic Field Simulations of Lower Hybrid Waves in Tokamaks

The most common method for treating wave propagation in tokamaks in the lower hybrid range of frequencies (LHRF) has been toroidal ray tracing, owing to the short wavelengths (relative to the system size) found in this regime. Although this technique provides an accurate description of 2D and 3D plasma inhomogeneity effects on wave propagation, the approach neglects important effects related to focusing, diffraction, and finite extent of the RF launcher. Also, the method breaks down at plasma cutoffs and caustics. Recent adaptation of full-wave electromagnetic field solvers to massively parallel computers has made it possible to accurately resolve wave phenomena in the LHRF. One such solver, the TORIC code, has been modified to simulate LH waves by implementing boundary conditions appropriate for coupling the fast electromagnetic and the slow electrostatic waves in the LHRF. In this frequency regime the plasma conductivity operator can be formulated in the limits of unmagnetized ions and strongly magnetized electrons, resulting in a relatively simple and explicit form. Simulations have been done for parameters typical of the planned LHRF experiments on Alcator C-Mod, demonstrating fully resolved fast and slow LH wave fields using a Maxwellian non-relativistic plasma dielectric. Significant spectral broadening of the injected wavemore » spectrum and focusing of the wave fields have been found, especially at caustic surfaces. Comparisons with toroidal ray tracing have also been done and differences between the approaches have been found, especially for cases where wave caustics form. The possible role of this diffraction-induced spectral broadening in filling the spectral gap in LH heating and current drive will be discussed.« less
Authors:
;  [1] ;  [2] ;  [3] ; ; ; ;  [4] ; ;  [5] ;  [6] ; ;  [7] ;  [8]
  1. MIT - Plasma Science and Fusion Center Cambridge, MA 02139 (United States)
  2. Institute fuer Plasma Physik Garching (Germany)
  3. Computer Science and Mathematics Division, Oak Ridge National Lab Oak Ridge, TN (United States)
  4. Oak Ridge National Laboratory -- Oak Ridge, TN (United States)
  5. Princeton Plasma Physics Laboratory - Princeton, New Jersey (United States)
  6. CompX - Del Mar, CA (United States)
  7. Lodestar Research Corporation - Boulder, CO (United States)
  8. ATK-Mission Research Corp. - Newington, VA (United States)
Publication Date:
OSTI Identifier:
20726328
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 787; Journal Issue: 1; Conference: 16. topical conference on radio frequency power in plasmas, Park City, UT (United States), 11-13 Apr 2005; Other Information: DOI: 10.1063/1.2098242; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALCATOR DEVICE; BOUNDARY CONDITIONS; COMPARATIVE EVALUATIONS; COUPLING; DIFFRACTION; ELECTRIC CURRENTS; ELECTROMAGNETIC FIELDS; ELECTROMAGNETIC RADIATION; ELECTRONS; LINE BROADENING; LOWER HYBRID CURRENT DRIVE; LOWER HYBRID HEATING; PLASMA SIMULATION; PLASMA WAVES; RELATIVISTIC PLASMA; SURFACES; WAVE PROPAGATION; WAVELENGTHS