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Reflectometry for Density Fluctuation and Profile Measurements in TST-2

Takuma YAMADA, Akira EJIRI¹⁾, Yoshiyuki SHIMADA¹⁾, Takuya OOSAKO¹⁾, Jiro TSUJIMURA¹⁾, Yuichi TAKASE¹⁾, Yuuki TORII²⁾, Makoto SASAKI³⁾, Hiroshi TOJO¹⁾, Tetsuya MASUDA¹⁾, Hideo NUGA³⁾, Nobuyuki SUMITOMO³⁾, Soichiro KAINAGA³⁾ and Junichi SUGIYAMA¹⁾

Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan

1)

Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8561, Japan

2)

High Temperature Plasma Center, The University of Tokyo, Kashiwa 277-8568, Japan

3)

Graduate School of Science, The University of Tokyo, Bunkyo 113-0033, Japan

(Received 4 December 2006 / Accepted 7 March 2007 / Published 20 November 2007)

Abstract

A reflectometer in Ka-band was designed, constructed and applied to the TST-2 spherical tokamak in order to detect density fluctuations induced by the radio frequency (RF) heating wave, and to measure the density profile. The optics of the reflectometer consists of two concave mirrors to make a small microwave beam spot inside the plasma. Using Kirchhoff integration, the parameters of the optics were optimized to achieve a high throughput (i.e. the ratio of the received to the launched powers) in various measurement conditions. Using the reflectometer, the density fluctuations in the frequency range of RF were detected and the electric field excited by RF (21 MHz/260 kW) was estimated to be about 1.3 kV/m.

Copyright (c) 2007 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

reflectometry, spherical tokamak, high harmonic fast wave, heating, density fluctuation

DOI: 10.1585/pfr.2.S1037

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This paper may be cited as follows:

Takuma YAMADA, Akira EJIRI, Yoshiyuki SHIMADA, Takuya OOSAKO, Jiro TSUJIMURA, Yuichi TAKASE, Yuuki TORII, Makoto SASAKI, Hiroshi TOJO, Tetsuya MASUDA, Hideo NUGA, Nobuyuki SUMITOMO, Soichiro KAINAGA and Junichi SUGIYAMA, Plasma Fusion Res. 2, S1037 (2007).