Lower hybrid current drive in a high density diverted tokamak

  • G. M. Wallace
  • , A. E. Hubbard
  • , S. Shiraiwa
  • , P. T. Bonoli
  • , I. C. Faust
  • , R. W. Harvey
  • , J. W. Hughes
  • , B. L. Labombard
  • , C. Lau
  • , O. Meneghini
  • , R. R. Parker
  • , M. L. Reinke
  • , A. E. Schmidt
  • , A. P. Smirnov
  • , J. L. Terry
  • , D. G. Whyte
  • , J. R. Wilson
  • , J. C. Wright
  • , S. J. Wukitch

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

Experimental observations of LHCD at high density (n̄ e> 10 20m -3) on the Alcator C-Mod tokamak are presented in this paper. Bremsstrahlung emission from relativistic fast electrons in the core plasma drops sharply in single null discharges well below the density limit previously observed on limited tokamaks (ω/ω LH∼2). Modeling and experimental evidence suggest that the absence of LH driven fast electrons at high density may be due to collisional absorption in the scrape off layer. Experiments show that the expected current drive density dependence is recovered for inner wall limited discharges across the range of densities scanned (0.5×10 20m -3<n̄ e<1. 5×10 20m -3). Increasing T e in the periphery of the plasma (0.8<r/a<1.0) also results in a modest increase in non-thermal electron emission at high n̄ e. Ray tracing/Fokker-Planck simulations of these discharges predict the observed sensitivity to plasma position when the effects of collisional absorption in the SOL are included in the model.

Original languageEnglish
Title of host publicationRadio Frequency Power in Plasmas - Proceedings of the 19th Topical Conference
Pages419-422
Number of pages4
DOIs
StatePublished - 2011
Externally publishedYes
Event19th Topical Conference on Radio Frequency Power in Plasmas - Newport, RI, United States
Duration: Jun 1 2011Jul 3 2011

Publication series

NameAIP Conference Proceedings
Volume1406
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Conference

Conference19th Topical Conference on Radio Frequency Power in Plasmas
Country/TerritoryUnited States
CityNewport, RI
Period06/1/1107/3/11

Keywords

  • Lower hybrid current drive
  • collisional absorption
  • density limit
  • ray tracing
  • scrape off layer

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