Current Profile Modification By Lower Hybrid Waves in Alcator C-Mod

POSTER

Abstract

Driving current off-axis is a prerequisite for realizing steady-state, high-performance Advanced Tokamak (AT) regimes. Lower Hybrid Current Drive (LHCD) is well suited for this purpose since the driven current is typically deposited beyond r/a = 0.5. An important step toward the goal of forming AT regimes with LHCD in Alcator C-Mod is validation of ray-tracing and full-wave codes regarding the location of the LH driven current. In LH experiments on C-Mod, bremsstrahlung produced by fast electrons carrying the RF-induced current indicates that the current is driven off-axis at a location determined by the parallel index of refraction. This is in qualitative agreement with expectation and is supported by indirect evidence such as decreased li, sawtooth stabilization, and changes in q(r) as inferred from MSE. The results will be compared with the predictions of ray-tracing (GENRAY) and full-wave codes (TORIC) coupled with Fokker-Planck codes that follow the self-consistent evolution of f(v).

Authors

  • R. Parker

    MIT PSFC, MIT

  • Paul Bonoli

    MIT PSFC, MIT - Plasma Science and Fusion Center, MIT

  • A.E. Hubbard

    MIT PSFC

  • J. Ko

    Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA, USA, MIT PSFC

  • M. Porkolab

    PSFC MIT, MIT PSFC, MIT, MIT, PSFC

  • A.E. Schmidt

    MIT PSFC

  • D. Terry

    MIT PSFC

  • G.M. Wallace

    MIT PSFC

  • S. Wolfe

    MIT PSFC

  • J.C. Wright

    MIT PSFC

  • Steve Scott

    Princeton Plasma Physics Laboratory, Princeton Plasma Physics Laboratory, Princeton, NJ, USA, PPPL

  • J.R. Wilson

    NSTX Team, PPPL, PPPL, NSTX Team, Princeton Plasma Physics Laboratory