Fast Wave Heating in the NSTX-Upgrade Device
Authors: Nicola Bertelli. et. al.
Abstract:
NSTX-Upgrade will operate with toroidal magnetic fields (BT) up to 1 T, nearly twice the value used in the
experiments on NSTX, and the available NBI power will be doubled. The doubling of BT while retaining the 30 MHz RF
source frequency has moved the heating regime from the high harmonic fast wave (HHFW) regime used in NSTX to the
mid harmonic fast wave (MHFW) regime. By making use of the full wave code AORSA, this work shows that direct ion
damping (mainly by thermal ions localized at the 5th harmonic resonance) might be significant in NSTX-Upgrade under
TRANSP predicted full performance conditions and the electron and ion absorption is sensitive to the ratio of electron and
ion temperature. Launching at high toroidal wave number appears to be one way to significantly reduce the ion damping. By
using the extended AORSA code, which includes a detailed description of the scrape-off layer in the field solutions, we found
a large electric field amplitude outside of the last closed flux surface as previously seen in NSTX from AORSA simulations
(D. L. Green, et al, Phys. Rev. Lett. 107, 145001 (2011)). Preliminary results by introducing a collision damping in the scrapeoff
layer in the AORSA code to represent a damping process are presented, showing for the first time absorbed power in the
scrape-off layer.
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Submitted to: 20th Topical Conference on Radio Frequency Power in Plasmas, Sorrento, Italy, June 25-28, 2013)
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Download PPPL-4912 (pdf 274 KB 4 pp)
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