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Title: Electron Bernstein Wave Research on CDX-U and NSTX

Abstract

Mode-converted electron Bernstein waves (EBWs) potentially allow the measurement of local electron temperature (Te) and the implementation of local heating and current drive in spherical torus (ST) devices, which are not directly accessible to low harmonic electron cyclotron waves. This paper reports on the measurement of X-mode radiation mode-converted from EBWs observed normal to the magnetic field on the midplane of the Current Drive Experiment-Upgrade (CDX-U) and the National Spherical Torus Experiment (NSTX) spherical torus plasmas. The radiation temperature of the EBW emission was compared to Te measured by Thomson scattering and Langmuir probes. EBW mode-conversion efficiencies of over 20% were measured on both CDX-U and NSTX. Sudden increases of mode-conversion efficiency, of over a factor of three, were observed at high-confinement-mode transitions on NSTX, when the measured edge density profile steepened. The EBW mode-conversion efficiency was found to depend on the density gradient at the mode-conversion layer in the plasma scrape-off, consistent with theoretical predictions. The EBW emission source was determined by a perturbation technique to be localized at the electron cyclotron resonance layer and was successfully used for radial transport studies. Recently, a new in-vessel antenna and Langmuir probe array were installed on CDX-U to better characterize andmore » enhance the EBW mode-conversion process. The probe incorporates a local adjustable limiter to control and maximize the mode-conversion efficiency in front of the antenna by modifying the density profile in the plasma scrape-off where fundamental EBW mode conversion occurs. Initial results show that the mode-conversion efficiency can be increased to {approximately}100% when the local limiter is inserted near the mode-conversion layer. Plans for future EBW research, including EBW heating and current-drive studies, are discussed.« less

Authors:
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Publication Date:
Research Org.:
Princeton Plasma Physics Lab., NJ (US)
Sponsoring Org.:
USDOE Office of Energy Research (ER) (US)
OSTI Identifier:
784554
Report Number(s):
PPPL-3568
TRN: US0106119
DOE Contract Number:  
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 18 May 2001
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; EFFICIENCY; ELECTRON CYCLOTRON-RESONANCE; ELECTRON TEMPERATURE; LANGMUIR PROBE; MAGNETIC FIELDS; MODE CONVERSION; THOMSON SCATTERING; BERNSTEIN MODE; NSTX DEVICE; CDX-U SPHEROMAK

Citation Formats

Taylor, G., Efthimion, P.C., Jones, B., Hosea, J.C., Kaita, R., LeBlanc, B.P., Majeski, R., Munsat, T., Phillips, C.K., Spaleta, J., Wilson, J.R., Rasmussen, D., Bell, G., Bigelow, T.S., Carter, M.D., Swain, D.W., Wilgen, J.B., Ram, A.K., Bers, A., Harvey, R.W., and and Forest, C.B. Electron Bernstein Wave Research on CDX-U and NSTX. United States: N. p., 2001. Web. doi:10.2172/784554.
Taylor, G., Efthimion, P.C., Jones, B., Hosea, J.C., Kaita, R., LeBlanc, B.P., Majeski, R., Munsat, T., Phillips, C.K., Spaleta, J., Wilson, J.R., Rasmussen, D., Bell, G., Bigelow, T.S., Carter, M.D., Swain, D.W., Wilgen, J.B., Ram, A.K., Bers, A., Harvey, R.W., & and Forest, C.B. Electron Bernstein Wave Research on CDX-U and NSTX. United States. doi:10.2172/784554.
Taylor, G., Efthimion, P.C., Jones, B., Hosea, J.C., Kaita, R., LeBlanc, B.P., Majeski, R., Munsat, T., Phillips, C.K., Spaleta, J., Wilson, J.R., Rasmussen, D., Bell, G., Bigelow, T.S., Carter, M.D., Swain, D.W., Wilgen, J.B., Ram, A.K., Bers, A., Harvey, R.W., and and Forest, C.B. Fri . "Electron Bernstein Wave Research on CDX-U and NSTX". United States. doi:10.2172/784554. https://www.osti.gov/servlets/purl/784554.
@article{osti_784554,
title = {Electron Bernstein Wave Research on CDX-U and NSTX},
author = {Taylor, G. and Efthimion, P.C. and Jones, B. and Hosea, J.C. and Kaita, R. and LeBlanc, B.P. and Majeski, R. and Munsat, T. and Phillips, C.K. and Spaleta, J. and Wilson, J.R. and Rasmussen, D. and Bell, G. and Bigelow, T.S. and Carter, M.D. and Swain, D.W. and Wilgen, J.B. and Ram, A.K. and Bers, A. and Harvey, R.W. and and Forest, C.B.},
abstractNote = {Mode-converted electron Bernstein waves (EBWs) potentially allow the measurement of local electron temperature (Te) and the implementation of local heating and current drive in spherical torus (ST) devices, which are not directly accessible to low harmonic electron cyclotron waves. This paper reports on the measurement of X-mode radiation mode-converted from EBWs observed normal to the magnetic field on the midplane of the Current Drive Experiment-Upgrade (CDX-U) and the National Spherical Torus Experiment (NSTX) spherical torus plasmas. The radiation temperature of the EBW emission was compared to Te measured by Thomson scattering and Langmuir probes. EBW mode-conversion efficiencies of over 20% were measured on both CDX-U and NSTX. Sudden increases of mode-conversion efficiency, of over a factor of three, were observed at high-confinement-mode transitions on NSTX, when the measured edge density profile steepened. The EBW mode-conversion efficiency was found to depend on the density gradient at the mode-conversion layer in the plasma scrape-off, consistent with theoretical predictions. The EBW emission source was determined by a perturbation technique to be localized at the electron cyclotron resonance layer and was successfully used for radial transport studies. Recently, a new in-vessel antenna and Langmuir probe array were installed on CDX-U to better characterize and enhance the EBW mode-conversion process. The probe incorporates a local adjustable limiter to control and maximize the mode-conversion efficiency in front of the antenna by modifying the density profile in the plasma scrape-off where fundamental EBW mode conversion occurs. Initial results show that the mode-conversion efficiency can be increased to {approximately}100% when the local limiter is inserted near the mode-conversion layer. Plans for future EBW research, including EBW heating and current-drive studies, are discussed.},
doi = {10.2172/784554},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri May 18 00:00:00 EDT 2001},
month = {Fri May 18 00:00:00 EDT 2001}
}

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