First high-power helicon results from DIII-D
R. I. Pinsker, B. Van Compernolle, Shawn Tang, Jeff Lestz, C.P. Moeller, C. C. Petty, Alexandre Dupuy, Jared Squire, A. M. Garofalo, M. Porkoláb, J. C. Rost, Seung-Gyou Baek, A. Nagy, Satyajit Chowdhury, N. A. Crocker, Genevieve DeGrandchamp, A.G. McLean, K. Gage, A. Marinoni, E. H. Martin, G. Ronchi, the DIII-D Team
Abstract
Abstract More than 0.6 MW of rf power at 476 MHz has been coupled to DIII-D plasmas by launching helicon (whistler) waves with a traveling-wave antenna (comb-line) in the fast-wave polarization (Van Compernolle et al 2021 Nucl. Fusion 61 116034) which resulted in the observation of electron heating of the core plasma with single-pass absorption based on ray-tracing in L-mode discharges. The coupling performance of the 1.5 m wide 30-element comb-line traveling-wave antenna has been consistent with expectations based on the 2015–2016 experiments on DIII-D with a low-power 12-element prototype (Pinsker et al 2018 Nucl. Fusion 58 106007). The conditioning process that was necessary to carry out high-power experiments is discussed; rf-specific impurities have not been observed. Parametric decay instabilities have been observed and are being investigated as a potential edge absorption mechanism (Porkolab et al 2023 AIP Conf. Proc. 2984 070004).