Effect of wall boundary on the scrape-off layer losses of high harmonic fast wave in NSTX and NSTX-U

We perform numerical simulations of high harmonic fast waves (HHFWs) in the scrape-off-layer (SOL) of National Spherical Torus Experiment (NSTX)/NSTX-U using a recently developed 2D full wave code. We particularly show that a realistic NSTX SOL boundary can significantly affect HHFW propagation and...

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Bibliographic Details
Published in:Physics of plasmas 2019-06, Vol.26 (6)
Main Authors: Kim, Eun-Hwa, Bertelli, Nicola, Ono, Masayuki, Valeo, Ernest J., Hosea, Joel C., Perkins, Rory J.
Format: Article
Language:English
Subjects:
Antennas
Computer simulation
Electron density
Plasma physics
Power loss
Toruses
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Summary:We perform numerical simulations of high harmonic fast waves (HHFWs) in the scrape-off-layer (SOL) of National Spherical Torus Experiment (NSTX)/NSTX-U using a recently developed 2D full wave code. We particularly show that a realistic NSTX SOL boundary can significantly affect HHFW propagation and power losses in the SOL. In NSTX SOL boundaries, HHFW is easily localized near the antenna and propagates less to the SOL, and thus, less power is lost to the SOL. We also show that the lower SOL power losses occur when the SOL volume is smaller and the distance between the last closed flux surface and the antenna is shorter. We investigate the effect of electron density in front of the antenna and the ambient magnetic field strengths on the SOL power losses as well. Showing consistency with the experiments, SOL losses are minimized when the SOL density is near the critical density where the fast wave cutoff is open, and the plasma is strongly magnetized.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.5091579