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Title: Edge Ion Heating by Launched High Harmonic Fast Waves in NSTX

Abstract

A new spectroscopic diagnostic on the National Spherical Torus Experiment (NSTX) measures the velocity distribution of ions in the plasma edge simultaneously along both poloidal and toroidal views. An anisotropic ion temperature is measured during high-power high harmonic fast wave (HHFW) radio-frequency (rf) heating in helium plasmas, with the poloidal ion temperature roughly twice the toroidal ion temperature. Moreover, the measured spectral distribution suggests that two populations of ions are present and have temperatures of typically 500 eV and 50 eV with rotation velocities of -50 km/s and -10 km/s, respectively (predominantly perpendicular to the local magnetic field). This bi-modal distribution is observed in both the toroidal and poloidal views (for both He{sup +} and C{sup 2+} ions), and is well correlated with the period of rf power application to the plasma. The temperature of the hot component is observed to increase with the applied rf power, which was scanned between 0 and 4.3 MW . The 30 MHz HHFW launched by the NSTX antenna is expected and observed to heat core electrons, but plasma ions do not resonate with the launched wave, which is typically at >10th harmonic of the ion cyclotron frequency in the region of observation. Amore » likely ion heating mechanism is parametric decay of the launched HHFW into an Ion Bernstein Wave (IBW). The presence of the IBW in NSTX plasmas during HHFW application has been directly confirmed with probe measurements. IBW heating occurs in the perpendicular ion distribution, consistent with the toroidal and poloidal observations. Calculations of IBW propagation indicate that multiple waves could be created in the parametric decay process, and that most of the IBW power would be absorbed in the outer 10 to 20 cm of the plasma, predominantly on fully stripped ions. These predictions are in qualitative agreement with the observations, and must be accounted for when calculating the energy budget of the plasma.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Princeton Plasma Physics Lab., Princeton, NJ (US)
Sponsoring Org.:
USDOE Office of Science (SC) (US)
OSTI Identifier:
836477
Report Number(s):
PPPL-4027
TRN: US0500628
DOE Contract Number:  
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Dec 2004
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANTENNAS; CYCLOTRON FREQUENCY; DECAY; DISTRIBUTION; ECOSYSTEMS; ELECTRONS; ENERGY BALANCE; HARMONICS; HEATING; HELIUM; ION TEMPERATURE; PROBES; ROTATION; VELOCITY; EDGE PLASMA; HEATING ICRF; ION HEATING; RF HEATING

Citation Formats

T.M. Biewer, R.E. Bell, S.J. Diem, C.K. Phillips, J.R. Wilson, and P.M. Ryan. Edge Ion Heating by Launched High Harmonic Fast Waves in NSTX. United States: N. p., 2004. Web. doi:10.2172/836477.
T.M. Biewer, R.E. Bell, S.J. Diem, C.K. Phillips, J.R. Wilson, & P.M. Ryan. Edge Ion Heating by Launched High Harmonic Fast Waves in NSTX. United States. doi:10.2172/836477.
T.M. Biewer, R.E. Bell, S.J. Diem, C.K. Phillips, J.R. Wilson, and P.M. Ryan. Wed . "Edge Ion Heating by Launched High Harmonic Fast Waves in NSTX". United States. doi:10.2172/836477. https://www.osti.gov/servlets/purl/836477.
@article{osti_836477,
title = {Edge Ion Heating by Launched High Harmonic Fast Waves in NSTX},
author = {T.M. Biewer and R.E. Bell and S.J. Diem and C.K. Phillips and J.R. Wilson and P.M. Ryan},
abstractNote = {A new spectroscopic diagnostic on the National Spherical Torus Experiment (NSTX) measures the velocity distribution of ions in the plasma edge simultaneously along both poloidal and toroidal views. An anisotropic ion temperature is measured during high-power high harmonic fast wave (HHFW) radio-frequency (rf) heating in helium plasmas, with the poloidal ion temperature roughly twice the toroidal ion temperature. Moreover, the measured spectral distribution suggests that two populations of ions are present and have temperatures of typically 500 eV and 50 eV with rotation velocities of -50 km/s and -10 km/s, respectively (predominantly perpendicular to the local magnetic field). This bi-modal distribution is observed in both the toroidal and poloidal views (for both He{sup +} and C{sup 2+} ions), and is well correlated with the period of rf power application to the plasma. The temperature of the hot component is observed to increase with the applied rf power, which was scanned between 0 and 4.3 MW . The 30 MHz HHFW launched by the NSTX antenna is expected and observed to heat core electrons, but plasma ions do not resonate with the launched wave, which is typically at >10th harmonic of the ion cyclotron frequency in the region of observation. A likely ion heating mechanism is parametric decay of the launched HHFW into an Ion Bernstein Wave (IBW). The presence of the IBW in NSTX plasmas during HHFW application has been directly confirmed with probe measurements. IBW heating occurs in the perpendicular ion distribution, consistent with the toroidal and poloidal observations. Calculations of IBW propagation indicate that multiple waves could be created in the parametric decay process, and that most of the IBW power would be absorbed in the outer 10 to 20 cm of the plasma, predominantly on fully stripped ions. These predictions are in qualitative agreement with the observations, and must be accounted for when calculating the energy budget of the plasma.},
doi = {10.2172/836477},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Dec 01 00:00:00 EST 2004},
month = {Wed Dec 01 00:00:00 EST 2004}
}

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