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Title: Behavior of Small-Scale Density Fluctuations in Discharges with Off-Axis Electron-Cyclotron Resonance Heating in the T-10 Tokamak

Abstract

In experiments on off-axis electron-cyclotron resonance heating in the T-10 tokamak, a steep gradient of the electron temperature was observed to form for a short time at a relative radius of {rho} {approx_equal} 0.25 after the heating power was switched off. Small-scale fluctuations of the electron density were studied with the help of correlation reflectometry. It was found that, in a narrow region near {rho} {approx_equal} 0.25, the amplitude of the density fluctuations was two times lower than that in the ohmic heating phase. Quasi-coherent fluctuations were suppressed over a period of time during which the steep temperature gradient existed. Measurements of the poloidal rotation velocity of turbulent fluctuations show that there is no velocity shear after the heating is switched off. An analysis of the linear growth rates of instabilities shows that the ion-temperature-gradient mode is unstable at {rho} {approx_equal} 0.25 throughout the entire discharge phase. The effect observed can be explained by an increase in the distance between the rational surfaces near the radius at which the safety factor is q = 1 due to the temporary flattening of the q profile after the off-axis electron-cyclotron resonance heating is switched off.

Authors:
; ;  [1]
  1. Institute of Nuclear Fusion, Russian Research Centre Kurchatov Institute, pl. Kurchatova 1, Moscow, 123182 (Russian Federation)
Publication Date:
OSTI Identifier:
20718864
Resource Type:
Journal Article
Resource Relation:
Journal Name: Plasma Physics Reports; Journal Volume: 31; Journal Issue: 12; Other Information: Translated from Fizika Plazmy, ISSN 0367-2921, 31, 1059-1067 (No. 12, 2005); DOI: 10.1134/1.2147644; (c) 2005 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA); TN:
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AMPLITUDES; CORRELATIONS; ECR HEATING; ELECTRIC DISCHARGES; ELECTRON DENSITY; ELECTRON TEMPERATURE; FLUCTUATIONS; ION TEMPERATURE; MODE RATIONAL SURFACES; PLASMA; PLASMA CONFINEMENT; PLASMA DENSITY; PLASMA DIAGNOSTICS; PLASMA INSTABILITY; RF SYSTEMS; SHEAR; T-10 TOKAMAK; TEMPERATURE GRADIENTS; TURBULENCE

Citation Formats

Shelukhin, D.A., Vershkov, V.A., and Razumova, K.A. Behavior of Small-Scale Density Fluctuations in Discharges with Off-Axis Electron-Cyclotron Resonance Heating in the T-10 Tokamak. United States: N. p., 2005. Web. doi:10.1134/1.2147644.
Shelukhin, D.A., Vershkov, V.A., & Razumova, K.A. Behavior of Small-Scale Density Fluctuations in Discharges with Off-Axis Electron-Cyclotron Resonance Heating in the T-10 Tokamak. United States. doi:10.1134/1.2147644.
Shelukhin, D.A., Vershkov, V.A., and Razumova, K.A. Thu . "Behavior of Small-Scale Density Fluctuations in Discharges with Off-Axis Electron-Cyclotron Resonance Heating in the T-10 Tokamak". United States. doi:10.1134/1.2147644.
@article{osti_20718864,
title = {Behavior of Small-Scale Density Fluctuations in Discharges with Off-Axis Electron-Cyclotron Resonance Heating in the T-10 Tokamak},
author = {Shelukhin, D.A. and Vershkov, V.A. and Razumova, K.A.},
abstractNote = {In experiments on off-axis electron-cyclotron resonance heating in the T-10 tokamak, a steep gradient of the electron temperature was observed to form for a short time at a relative radius of {rho} {approx_equal} 0.25 after the heating power was switched off. Small-scale fluctuations of the electron density were studied with the help of correlation reflectometry. It was found that, in a narrow region near {rho} {approx_equal} 0.25, the amplitude of the density fluctuations was two times lower than that in the ohmic heating phase. Quasi-coherent fluctuations were suppressed over a period of time during which the steep temperature gradient existed. Measurements of the poloidal rotation velocity of turbulent fluctuations show that there is no velocity shear after the heating is switched off. An analysis of the linear growth rates of instabilities shows that the ion-temperature-gradient mode is unstable at {rho} {approx_equal} 0.25 throughout the entire discharge phase. The effect observed can be explained by an increase in the distance between the rational surfaces near the radius at which the safety factor is q = 1 due to the temporary flattening of the q profile after the off-axis electron-cyclotron resonance heating is switched off.},
doi = {10.1134/1.2147644},
journal = {Plasma Physics Reports},
number = 12,
volume = 31,
place = {United States},
year = {Thu Dec 15 00:00:00 EST 2005},
month = {Thu Dec 15 00:00:00 EST 2005}
}
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