Electron Bernstein Wave Research on NSTX and CDX-U
Authors: G. Taylor, P.C. Efthimion, B. Jones, G.L. Bell, A. Bers, T.S. Bigelow, M.D. Carter, R.W. Harvey, A.K. Ram, D.A. Rasmussen, A.P. Smirnov, J.B. Wilgen, and J.R. Wilson
Date of PPPL Report: June 2003
Presented at: the 15th Topical Confrence on Radio Frequency Power in Plasmas, Grand Teton National Park, Moran, Wyoming, May 19-21, 2003
Studies of thermally emitted electron Bernstein waves (EBWs) on CDX-U and NSTX, via mode conversion (MC) to electromagnetic radiation, support the use of EBWs to measure the Te profile and provide local electron heating and current drive (CD) in overdense spherical torus plasmas. An X-mode antenna with radially adjustable limiters successfully controlled EBW MC on CDX-U and enhanced MC efficiency to ~ 100%. So far the X-mode MC efficiency on NSTX has been increased by a similar technique to 40-50% and future experiments are focused on achieving greater than or equal to 80% MC. MC efficiencies on both machines agree well with theoretical predictions. Ray tracing and Fokker-Planck modeling for NSTX equilibria are being conducted to support the design of a 3 MW, 15 GHz EBW heating and CD system for NSTX to assist non-inductive plasma startup, current ramp up, and to provide local electron heating and CD in high beta NSTX plasmas.