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

Abstract

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.

Authors:
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  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
DOE Contract Number:  
AC02-09CH11466
Product Type:
Dataset
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Subject:
ICRF HHFW RF rectification Sheaths Divertor
Keywords:
ICRF HHFW RF rectification Sheaths Divertor
OSTI Identifier:
1367878
DOI:
10.11578/1367878

Citation Formats

Perkins, R.J., Hosea, J.C., Jaworski, M.A., Bell, R.E., Bertelli, N., Kramer, G.J., Roquemore, L., Taylor, G., and Wilson, J.R. The Role of Recti ed Currents in Far-Field RF Sheaths and in SOL Losses of HHFW Power on NSTX. United States: N. p., 2017. Web. doi:10.11578/1367878.
Perkins, R.J., Hosea, J.C., Jaworski, M.A., Bell, R.E., Bertelli, N., Kramer, G.J., Roquemore, L., Taylor, G., & Wilson, J.R. The Role of Recti ed Currents in Far-Field RF Sheaths and in SOL Losses of HHFW Power on NSTX. United States. doi:10.11578/1367878.
Perkins, R.J., Hosea, J.C., Jaworski, M.A., Bell, R.E., Bertelli, N., Kramer, G.J., Roquemore, L., Taylor, G., and Wilson, J.R. 2017. "The Role of Recti ed Currents in Far-Field RF Sheaths and in SOL Losses of HHFW Power on NSTX". United States. doi:10.11578/1367878. https://www.osti.gov/servlets/purl/1367878. Pub date:Mon May 01 00:00:00 EDT 2017
@article{osti_1367878,
title = {The Role of Recti ed Currents in Far-Field RF Sheaths and in SOL Losses of HHFW Power on NSTX},
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.},
abstractNote = {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.},
doi = {10.11578/1367878},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2017},
month = {5}
}

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