Time-Dependent Simulations of Fast-Wave Heated High-Non-Inductive-Fraction H-Mode Plasmas in the National Spherical Torus Experiment Upgrade

¹ Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA
² William E. Boeing Department of Aeronautics and Astronautics, University of Washington, Seattle, Washington 98195, USA

^* Corresponding author: gtaylor@pppl.gov

Published online: 23 October 2017

Abstract

30 MHz fast-wave heating may be an effective tool for non-inductively ramping low-current plasmas to a level suitable for initiating up to 12 MW of neutral beam injection on the National Spherical Tokamak Experiment Upgrade (NSTX-U). Previously on NSTX 30 MHz fast wave heating was shown to efficiently and rapidly heat electrons; at the NSTX maximum axial toroidal magnetic field (B_T(0)) of 0.55 T, 1.4 MW of 30 MHz heating increased the central electron temperature from 0.2 to 2 keV in 30 ms and generated an H-mode plasma with a non-inductive fraction (f_NI) ∼ 0.7 at a plasma current (I_p) of 300 kA. NSTX-U will operate at B_T(0) up to 1 T, with up to 4 MW of 30 MHz power (P_rf). Predictive TRANSP free boundary transport simulations, using the TORIC full wave spectral code to calculate the fast-wave heating and current drive, have been run for NSTX-U I_p = 300 kA H-mode plasmas. Favorable scaling of f_NI with 30 MHz heating power is predicted, with f_NI ≥ 1 for P_rf ≥ 2 MW.