Modeling Results for Proposed NSTX 28 GHz and EBWH System
Authors: G. TAYLOR, S.J. DIEM, R.A. ELLIS, E. FREDD, N. GREENOUGH, J.C. HOSEA, J.B. WILGEN, R.W. HARVEY, A.P. SMIRNOV, J. PREINHAELTER, J. URBAN, and A.K. RAM
Abstract:
A 28 GHz electron cyclotron heating (ECH) and electron Bernstein wave heating (EBWH) system has been proposed for installation on the National Spherical Torus
Experiment (NSTX). A 350 kW gyrotron connected to a fixed horn antenna is proposed for ECH-assisted solenoid-free plasma startup. Modeling predicts strong first pass on-axis EC absorption, even for low electron temperature, Te ~ 20 eV, Coaxial Helicity Injection (CHI) startup plasmas. ECH will heat the CHI plasma to Te ~ 300 eV, providing a suitable target plasma for 30 MHz high-harmonic fast wave heating. A second gyrotron and steered O-X-B mirror launcher is proposed for EBWH experiments. Radiometric measurements of thermal EBW emission detected via B-X-O coupling on NSTX support implementation of the proposed system. 80% B-X-O coupling efficiency was measured in L-mode plasmas and 60% B-X-O coupling efficiency was recently measured in H-mode plasmas conditioned with evaporated lithium. Modeling predicts local on-axis EBW heating and current drive using 28 GHz power in β ~ 20% NSTX plasmas should be possible, with current drive efficiencies ~ 40 kA/MW.
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Presented at: 15th Joint Workshop on Electgron Cyclotron Emission and Electron Cyclotron Resonance Heating, Yosemite, CA (March 10-13-08)
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Download PPPL-4306 (pdf 853Kb)
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