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Title: Investigation of EBW Thermal Emission and Mode Conversion Physics in H-Mode Plasmas on NSTX

Abstract

High β plasmas in the National Spherical Torus Experiment (NSTX) operate in the overdense regime, allowing the electron Bernstein wave (EBW) to propagate and be strongly absorbed/emitted at the electron cyclotron resonances. As such, EBWs may provide local electron heating and current drive. For these applications, efficient coupling between the EBWs and electromagnetic waves outside the plasma is needed. Thermal EBW emission (EBE) measurements, via oblique B-X-O double mode conversion, have been used to determine the EBW transmission efficiency for a wide range of plasma conditions on NSTX. Initial EBE measurements in H-mode plasmas exhibited strong emission before the L-H transition, but the emission rapidly decayed after the transition. EBE simulations show that collisional damping of the EBW prior to the mode conversion (MC) layer can significantly reduce the measured EBE for Te < 20 eV, explaining the observations. Lithium evaporation was used to reduce EBE collisional damping near the MC layer. As a result, the measured B-X-O transmission efficiency increased from < 10% (no Li) to 60% (with Li), consistent with EBE simulations.

Authors:
; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
959394
Report Number(s):
PPPL-4307
TRN: US0904761
DOE Contract Number:  
DE-ACO2-76CHO3073
Resource Type:
Conference
Resource Relation:
Conference: 15th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating, Yosemite, CA (March 10-13-08)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CYCLOTRON RESONANCE; CYCLOTRONS; DAMPING; ECR HEATING; EFFICIENCY; ELECTROMAGNETIC RADIATION; ELECTRONS; EVAPORATION; HEATING; LITHIUM; MODE CONVERSION; PHYSICS; PLASMA; NSTX

Citation Formats

Diem, S J, Efthimion, P C, Kugel, H W, LeBlanc, B P, Phillips, C K, Caughman, J B, Wilgen, J B, Harvey, R W, Preinhaelter, J, Urban, J, and Sabbagh, S A. Investigation of EBW Thermal Emission and Mode Conversion Physics in H-Mode Plasmas on NSTX. United States: N. p., 2008. Web.
Diem, S J, Efthimion, P C, Kugel, H W, LeBlanc, B P, Phillips, C K, Caughman, J B, Wilgen, J B, Harvey, R W, Preinhaelter, J, Urban, J, & Sabbagh, S A. Investigation of EBW Thermal Emission and Mode Conversion Physics in H-Mode Plasmas on NSTX. United States.
Diem, S J, Efthimion, P C, Kugel, H W, LeBlanc, B P, Phillips, C K, Caughman, J B, Wilgen, J B, Harvey, R W, Preinhaelter, J, Urban, J, and Sabbagh, S A. Thu . "Investigation of EBW Thermal Emission and Mode Conversion Physics in H-Mode Plasmas on NSTX". United States. https://www.osti.gov/servlets/purl/959394.
@article{osti_959394,
title = {Investigation of EBW Thermal Emission and Mode Conversion Physics in H-Mode Plasmas on NSTX},
author = {Diem, S J and Efthimion, P C and Kugel, H W and LeBlanc, B P and Phillips, C K and Caughman, J B and Wilgen, J B and Harvey, R W and Preinhaelter, J and Urban, J and Sabbagh, S A},
abstractNote = {High β plasmas in the National Spherical Torus Experiment (NSTX) operate in the overdense regime, allowing the electron Bernstein wave (EBW) to propagate and be strongly absorbed/emitted at the electron cyclotron resonances. As such, EBWs may provide local electron heating and current drive. For these applications, efficient coupling between the EBWs and electromagnetic waves outside the plasma is needed. Thermal EBW emission (EBE) measurements, via oblique B-X-O double mode conversion, have been used to determine the EBW transmission efficiency for a wide range of plasma conditions on NSTX. Initial EBE measurements in H-mode plasmas exhibited strong emission before the L-H transition, but the emission rapidly decayed after the transition. EBE simulations show that collisional damping of the EBW prior to the mode conversion (MC) layer can significantly reduce the measured EBE for Te < 20 eV, explaining the observations. Lithium evaporation was used to reduce EBE collisional damping near the MC layer. As a result, the measured B-X-O transmission efficiency increased from < 10% (no Li) to 60% (with Li), consistent with EBE simulations.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Mar 20 00:00:00 EDT 2008},
month = {Thu Mar 20 00:00:00 EDT 2008}
}

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