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Title: Observations of Anisotropic Ion Temperature in the NSTX Edge during RF Heating

Abstract

A new spectroscopic diagnostic with both toroidal and poloidal views has been implemented in the edge of the National Spherical Torus Experiment (NSTX). This edge rotation diagnostic (ERD) was designed to measure the velocity and temperature of ions. The intersection of the diagnostic sightlines with the intrinsic emission shell provides the localization of the measurement. There are 7 toroidally directed views and 6 poloidally directed views of the outboard plasma edge. The poloidal view is {approx}20 cm (toroidally) from the RF antenna, and the toroidal view is {approx}2 m away. The sightlines are nearly tangent to the flux surfaces. The C{sup 2+} triplet near 4651 {angstrom} and the He{sup +} line at 4685 {angstrom} are measured. In the results presented here, helium is the bulk, ''working'' ion of the discharge. The NSTX is a large spherical tokamak with a major radius of 0.85 m and a minor radius of 0.65 m. The outer walls and center-stack are lined with protective carbon tiles. Pulse lengths for these NSTX discharges are {approx} 600 ms, with an on-axis toroidal magnetic field of {approx} 0.3 T. The plasma current is 500 kA. The on-axis electron temperature and density are {le} 2 keV and {approx}more » 2 x 10{sup 19} m{sup -3}, respectively with {le} 4.3 MW of High Harmonic Fast Wave (HHFW) Radio Frequency (RF) auxiliary heating.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Princeton Plasma Physics Lab., Princeton, NJ (US)
Sponsoring Org.:
USDOE Office of Science (SC) (US)
OSTI Identifier:
828257
Report Number(s):
PPPL-3973
TRN: US0403884
DOE Contract Number:
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 28 Jun 2004
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 74 ATOMIC AND MOLECULAR PHYSICS; AUXILIARY HEATING; CARBON; ELECTRIC CURRENTS; ELECTRON TEMPERATURE; HARMONICS; HEATING; HELIUM I; ION TEMPERATURE; MAGNETIC FIELDS; MAGNETIC SURFACES; PLASMA; ROTATION; TRIPLETS; VELOCITY; EDGE PLASMA; ION HEATING; RF HEATING; WAVE INTERACTION, PLASMA

Citation Formats

T.M. Biewer, R.E. Bell, P.M. Ryan, and J.R. Wilson. Observations of Anisotropic Ion Temperature in the NSTX Edge during RF Heating. United States: N. p., 2004. Web. doi:10.2172/828257.
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T.M. Biewer, R.E. Bell, P.M. Ryan, & J.R. Wilson. Observations of Anisotropic Ion Temperature in the NSTX Edge during RF Heating. United States. doi:10.2172/828257.
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T.M. Biewer, R.E. Bell, P.M. Ryan, and J.R. Wilson. Mon . "Observations of Anisotropic Ion Temperature in the NSTX Edge during RF Heating". United States. doi:10.2172/828257. https://www.osti.gov/servlets/purl/828257.
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@article{osti_828257,
title = {Observations of Anisotropic Ion Temperature in the NSTX Edge during RF Heating},
author = {T.M. Biewer and R.E. Bell and P.M. Ryan and J.R. Wilson},
abstractNote = {A new spectroscopic diagnostic with both toroidal and poloidal views has been implemented in the edge of the National Spherical Torus Experiment (NSTX). This edge rotation diagnostic (ERD) was designed to measure the velocity and temperature of ions. The intersection of the diagnostic sightlines with the intrinsic emission shell provides the localization of the measurement. There are 7 toroidally directed views and 6 poloidally directed views of the outboard plasma edge. The poloidal view is {approx}20 cm (toroidally) from the RF antenna, and the toroidal view is {approx}2 m away. The sightlines are nearly tangent to the flux surfaces. The C{sup 2+} triplet near 4651 {angstrom} and the He{sup +} line at 4685 {angstrom} are measured. In the results presented here, helium is the bulk, ''working'' ion of the discharge. The NSTX is a large spherical tokamak with a major radius of 0.85 m and a minor radius of 0.65 m. The outer walls and center-stack are lined with protective carbon tiles. Pulse lengths for these NSTX discharges are {approx} 600 ms, with an on-axis toroidal magnetic field of {approx} 0.3 T. The plasma current is 500 kA. The on-axis electron temperature and density are {le} 2 keV and {approx} 2 x 10{sup 19} m{sup -3}, respectively with {le} 4.3 MW of High Harmonic Fast Wave (HHFW) Radio Frequency (RF) auxiliary heating.},
doi = {10.2172/828257},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jun 28 00:00:00 EDT 2004},
month = {Mon Jun 28 00:00:00 EDT 2004}
}
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Technical Report:
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DOI:  10.2172/828257
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  • ; ; ; ...
    A new spectroscopic diagnostic on the National Spherical Torus Experiment (NSTX) measures the velocity distribution of ions in the plasma edge with both poloidal and toroidal views. An anisotropic ion temperature is measured during the presence of high power HHFW RF heating in He plasmas, with the poloidal T(sub)i roughly twice the toroidal T(sub)i. Moreover, the measured spectral distribution suggests that two populations have temperatures of 500 eV and 50 eV with rotation velocities of -50 km/s and -10 km/s, respectively. This bi-modal distribution is observed in both the toroidal and poloidal views (in both He II and C IIImore » ions), and is well correlated with the period of RF power application to the plasma. The temperature of the edge ions is observed to increase with the applied RF power, which was scanned between 0 and 4.3MW. The ion heating mechanism from HHFW RF power has not yet been identified.« less

  • ; ; ; ...
    A new spectroscopic diagnostic on the National Spherical Torus Experiment (NSTX) measures the velocity distribution of ions in the plasma edge with both poloidal and toroidal views. An anisotropic ion temperature is measured during the presence of 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 are present and have temperatures of 500 eV and 50 eV with rotation velocities of -50 km/s and -10 km/s, respectively. This bi-modal distribution is observed in both the toroidal and poloidal viewsmore » (in 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 edge ions is observed to increase with the applied RF power, which was scanned between 0 and 4.3 MW. The ion heating mechanism is likely to be ion-Bernstein waves (IBW) from nonlinear decay of the launched HHFW.« less

  • ; ; ; ...
    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-modalmore » 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.« less

  • ; ; ; ...
    Edge measurements have been conducted on the PLT tokamak under a variety of operating conditions in order to ascertain the relevant processes at work in coupling rf power to plasmas. The edge density is found to increase significantly with the application of ICRF, and electron heating occurs in the vicinity of the Faraday shield surrounding the antenna. Spectroscopic measurements indicate that the energized antenna is a significant particle source. The relative increase of metallic impurities was found to be /approximately/2.7 times larger than the corresponding increase in deuterium. In addition, the relative increase of deuterium and impurities was /approximately/3--4 timesmore » greater at the energized antenna than at other locations around the torus. Model calculations show that for deuterium released from the Faraday shield, the D/sub ..cap alpha../ emission is localized radially to a region within 4 cm of the antenna. A correlation was found between the edge density and the D/sub ..cap alpha../ intensity that justifies its use as a measure of the particle source rate. 26 refs., 14 figs.« less

  • ;
    Measurements of ion temperatures in the ATC Tokamak by means of Doppler broadening of various ion lines are described, and typical results presented for the various auxiliary heating experiments: compression, neutral beam, lower hybrid and ion cyclotron frequency heating. Radial resolution of the temperature measurements is achieved by utilizing spectrum lines of ions of different ionization potentials: OVII lambda 1623A, CV lambda 2271A and CIV lambda 1548A, which are emitted from regions of different electron temperature. Measurement at a given radial location is performed as a function of time by repeated scanning of the line contour in times 1.5 tomore » 3.0 msec. The results indicate variations of heating efficiency with location and with power input level.« less