skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Edge loss of high-harmonic fast-wave heating power in NSTX: a cylindrical model

Abstract

Efficient high-harmonic fast-wave (HHFW) heating in the National Spherical Torus Experiment Upgrade (NSTX-U) would facilitate experiments in turbulence, transport, fast-ion studies, and more. However, previous HHFW operation in NSTX exhibited a large loss of fast-wave power to the divertor along the scrape-off layer field lines for edge densities above the fast-wave cutoff. It was postulated that the wave amplitude is enhanced in the scrapeoff layer due to cavity-like modes, and that these enhanced fields drive sheath losses through RF rectification. As part of ongoing work to confirm this hypothesis, we have developed a cylindrical cold-plasma model to identify and understand scenarios where a substantial fraction of wave power is confined to the plasma periphery. We previously identified a peculiar class of modes, named annulus resonances, that conduct approximately half of their wave power in the periphery and can also account for a significant fraction of the total wave power. Here, we study the influence of annulus resonances on wave field reconstructions and find instances where annulus-resonant modes dominate the spectrum and trap over half of the total wave power at the edge. The work is part of an ongoing effort to determine the mechanism underlying these scrape-off layer losses inmore » NSTX, identify optimal conditions for operation in NSTX-U, and predict whether similar losses occur for the ion-cyclotron minority heating scheme for both current experiments and future devices such as ITER.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
OSTI Identifier:
1393399
Grant/Contract Number:  
AC02-09CH11466
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 11; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ICRF; heating; tokamaks; edge loss; ANTENNA; DENSITY; PLASMA

Citation Formats

Perkins, R. J., Hosea, J. C., Bertelli, N., Taylor, G., and Wilson, J. R. Edge loss of high-harmonic fast-wave heating power in NSTX: a cylindrical model. United States: N. p., 2017. Web. https://doi.org/10.1088/1741-4326/aa7860.
Perkins, R. J., Hosea, J. C., Bertelli, N., Taylor, G., & Wilson, J. R. Edge loss of high-harmonic fast-wave heating power in NSTX: a cylindrical model. United States. https://doi.org/10.1088/1741-4326/aa7860
Perkins, R. J., Hosea, J. C., Bertelli, N., Taylor, G., and Wilson, J. R. Mon . "Edge loss of high-harmonic fast-wave heating power in NSTX: a cylindrical model". United States. https://doi.org/10.1088/1741-4326/aa7860. https://www.osti.gov/servlets/purl/1393399.
@article{osti_1393399,
title = {Edge loss of high-harmonic fast-wave heating power in NSTX: a cylindrical model},
author = {Perkins, R. J. and Hosea, J. C. and Bertelli, N. and Taylor, G. and Wilson, J. R.},
abstractNote = {Efficient high-harmonic fast-wave (HHFW) heating in the National Spherical Torus Experiment Upgrade (NSTX-U) would facilitate experiments in turbulence, transport, fast-ion studies, and more. However, previous HHFW operation in NSTX exhibited a large loss of fast-wave power to the divertor along the scrape-off layer field lines for edge densities above the fast-wave cutoff. It was postulated that the wave amplitude is enhanced in the scrapeoff layer due to cavity-like modes, and that these enhanced fields drive sheath losses through RF rectification. As part of ongoing work to confirm this hypothesis, we have developed a cylindrical cold-plasma model to identify and understand scenarios where a substantial fraction of wave power is confined to the plasma periphery. We previously identified a peculiar class of modes, named annulus resonances, that conduct approximately half of their wave power in the periphery and can also account for a significant fraction of the total wave power. Here, we study the influence of annulus resonances on wave field reconstructions and find instances where annulus-resonant modes dominate the spectrum and trap over half of the total wave power at the edge. The work is part of an ongoing effort to determine the mechanism underlying these scrape-off layer losses in NSTX, identify optimal conditions for operation in NSTX-U, and predict whether similar losses occur for the ion-cyclotron minority heating scheme for both current experiments and future devices such as ITER.},
doi = {10.1088/1741-4326/aa7860},
journal = {Nuclear Fusion},
number = 11,
volume = 57,
place = {United States},
year = {2017},
month = {9}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Save / Share:

Works referenced in this record:

Fast response of electron-scale turbulence to auxiliary heating cessation in National Spherical Torus Experiment
journal, November 2015

  • Ren, Y.; Wang, W. X.; LeBlanc, B. P.
  • Physics of Plasmas, Vol. 22, Issue 11
  • DOI: 10.1063/1.4935113

Tungsten impurity transport experiments in Alcator C-Mod to address high priority research and development for ITERa)
journal, May 2015

  • Loarte, A.; Reinke, M. L.; Polevoi, A. R.
  • Physics of Plasmas, Vol. 22, Issue 5
  • DOI: 10.1063/1.4921253

Optimization of ICRH for core impurity control in JET-ILW
journal, February 2016


HHFW Heating Efficiency on NSTX versus B[sub Φ] and Antenna k[sub ∥]
conference, January 2007

  • Hosea, J.; Bell, R.; Bernabei, S.
  • RADIO FREQUENCY POWER IN PLASMAS: 17th Topical Conference on Radio Frequency Power in Plasmas, AIP Conference Proceedings
  • DOI: 10.1063/1.2800453

High harmonic fast wave heating efficiency enhancement and current drive at longer wavelength on the National Spherical Torus Experiment
journal, May 2008

  • Hosea, J.; Bell, R. E.; LeBlanc, B. P.
  • Physics of Plasmas, Vol. 15, Issue 5
  • DOI: 10.1063/1.2837051

Operating The Upgraded NSTX HHFW Antenna Array In An Environment With Li-coated Surfaces
conference, January 2011

  • Ryan, P. M.; Ellis, R.; Hosea, J. C.
  • RADIO FREQUENCY POWER IN PLASMAS: Proceedings of the 19th Topical Conference, AIP Conference Proceedings
  • DOI: 10.1063/1.3664938

Recent Fast Wave Coupling and Heating Studies on NSTX, with Possible Implications for ITER
conference, January 2009

  • Hosea, J. C.; Bell, R. E.; Feibush, E.
  • RADIO FREQUENCY POWER IN PLASMAS: Proceedings of the 18th Topical Conference, AIP Conference Proceedings
  • DOI: 10.1063/1.3273706

High-Harmonic Fast-Wave Power Flow along Magnetic Field Lines in the Scrape-Off Layer of NSTX
journal, July 2012


Simulation of high-power electromagnetic wave heating in the ITER burning plasma
journal, July 2008

  • Jaeger, E. F.; Berry, L. A.; D’Azevedo, E. F.
  • Physics of Plasmas, Vol. 15, Issue 7
  • DOI: 10.1063/1.2959128

Predicting High Harmonic Ion Cyclotron Heating Efficiency in Tokamak Plasmas
journal, September 2011


Full wave simulations of fast wave heating losses in the scrape-off layer of NSTX and NSTX-U
journal, May 2014


Advances in high-harmonic fast wave physics in the National Spherical Torus Experiment
journal, May 2010

  • Taylor, G.; Bell, R. E.; Hosea, J. C.
  • Physics of Plasmas, Vol. 17, Issue 5
  • DOI: 10.1063/1.3371956

Resonance in fast-wave amplitude in the periphery of cylindrical plasmas and application to edge losses of wave heating power in tokamaks
journal, July 2016

  • Perkins, R. J.; Hosea, J. C.; Bertelli, N.
  • Physics of Plasmas, Vol. 23, Issue 7
  • DOI: 10.1063/1.4954899

ICRF-edge and surface interactions
journal, August 2011


Particle transport in the scrape-off layer and its relationship to discharge density limit in Alcator C-Mod
journal, May 2001

  • LaBombard, B.; Boivin, R. L.; Greenwald, M.
  • Physics of Plasmas, Vol. 8, Issue 5
  • DOI: 10.1063/1.1352596

Edge transport studies in the edge and scrape-off layer of the National Spherical Torus Experiment with Langmuir probes
journal, April 2014

  • Boedo, J. A.; Myra, J. R.; Zweben, S.
  • Physics of Plasmas, Vol. 21, Issue 4
  • DOI: 10.1063/1.4873390

Numerical modeling of the coupling of an ICRH antenna with a plasma with self-consistent antenna currents
journal, July 2002


RF current distribution and topology of RF sheath potentials in front of ICRF antennae
journal, July 2005


High harmonic fast waves in high beta plasmas
journal, November 1995


Spectral effects on fast wave core heating and current drive
journal, June 2009


High Harmonic Fast Wave Current Drive Experiments on NSTX
conference, January 2003

  • Ryan, P. M.
  • RADIO FREQUENCY POWER IN PLASMAS: 15th Topical Conference on Radio Frequency Power in Plasmas, AIP Conference Proceedings
  • DOI: 10.1063/1.1638029

    Works referencing / citing this record:

    Effect of wall boundary on the scrape-off layer losses of high harmonic fast wave in NSTX and NSTX-U
    journal, June 2019

    • Kim, Eun-Hwa; Bertelli, Nicola; Ono, Masayuki
    • Physics of Plasmas, Vol. 26, Issue 6
    • DOI: 10.1063/1.5091579