The Role of Recti ed Currents in Far-Field RF Sheaths and in SOL Losses of HHFW Power on NSTX

Perkins, R. J. ; Hosea, J. C. ; Jaworski, M. A. ; Bell, R. E. ; Bertelli, N. ; Kramer, G. J. ; Roquemore, L. ; Taylor, G. ; Wilson, J. R.
Issue date: 2017
Creative Commons Attribution 4.0 International (CC BY)
Cite as:
Perkins, R. J., Hosea, J. C., Jaworski, M. A., Bell, R. E., Bertelli, N., Kramer, G. J., Roquemore, L., Taylor, G., & Wilson, J. R. (2017). The Role of Recti ed Currents in Far-Field RF Sheaths and in SOL Losses of HHFW Power on NSTX [Data set]. Princeton Plasma Physics Laboratory, Princeton University.
  author      = {Perkins, R. J. and
                Hosea, J. C. and
                Jaworski, M. A. and
                Bell, R. E. and
                Bertelli, N. and
                Kramer, G. J. and
                Roquemore, L. and
                Taylor, G. and
                Wilson, J. R.},
  title       = {{The Role of Recti ed Currents in Far-Fie
                ld RF Sheaths and in SOL Losses of HHFW
                Power on NSTX}},
  publisher   = {{Princeton Plasma Physics Laboratory, Pri
                nceton University}},
  year        = 2017,
  url         = {}

Radio-frequency (RF) rectification is an important sheath phenomenon for wave heating of plasma in fusion devices and is proposed to be the mechanism responsible for converting highharmonic fast-wave (HHFW) power in the National Spherical Torus eXperiment (NSTX) into a heat ux to the divertor. RF rectification has two aspects: current rectification and voltage recti- fication, and, while the latter is emphasized in many application, we demonstrate the importance of current rectification in analysis of the NSTX divertor during HHFW heating. When rectified currents are accounted for in first-principle models for the heat ux to the tiles, we predict a sizeable enhancement for the heat ux in the presence of an RF field: for one case studied, the predicted heat ux increases from 0:103 MW=m2 to 0:209 MW=m2. We also demonstrate how this rectification scales with injected HHFW power by tracking probe characteristics during a HHFW power ramp; the rectified current may be clamped at a certain level. This work is important for minimizing SOL losses of HHFW power in NSTX-U but may also have implications for near-field studies of ICRF antennae: ignoring rectified current may lead to underestimated heat uxes and overestimated rectified voltages.

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