Density Profile and Fluctuation Measurements by Microwave Reflectometry on EAST

• Published in: Plasma science & technology Vol. 16; no. 4; pp. 311 - 315
• Main Author: 张寿彪 苛翔 凌必利 王嵎民 张涛 韩翔 刘子奚 布景亮 李建刚
• Format: Journal Article
• Language: English
• Published: 01.04.2014
• Subjects: Density; Dispersions; EAST装置; Evolution; Fluctuation; H模式放电; Microwaves; Reflectometry; Tokamak devices; Voltage controlled oscillators; Waveform generators; 任意波形发生器; 密度分布; 微波反射; 波动; 测量; 高时间分辨率
• ISSN: 1009-0630
• DOI: 10.1088/1009-0630/16/4/02

A microwave reflectometry system operating in the V-band frequency with extraor- dinary mode polarization has been developed on the EAST tokamak. The reflectometry system, using a voltage-controlled oscillator （VCO） source driven by an arbitrary waveform generator with high temporal resolution, can operate for the density profile measurement. The result of the bench test shows that the output frequency of the VCO has a linear dependence on time. The dispersion of reflectometry system is determined and reported in this paper. The evolution of a pedestal density profile during the L-H transition is observed by the reflectometry in H-mode discharges on EAST tokamak. A frequency synthesizer is used to replace the VCO as microwave source for density fluctuation measurements. The level of density fluctuation in the pedestal shows an abrupt decrease when the plasma enters into H-mode. A coherent mode with a frequency of about 100 kHz is observed and the mode frequency decreases gradually as the pedestal evolves.