[Table of Contents]

Plasma and Fusion Research

Volume 8, 2402069 (2013)

Regular Articles

Optimization of Megawatt 77-GHz Gyrotron Operation for Collective Thomson Scattering in LHD
Shinya OGASAWARA1), Shin KUBO1,2), Masaki NISHIURA2), Yoshinori TATEMATSU3), Teruo SAITO3), Kenji TANAKA2), Takashi SHIMOZUMA2), Yasuo YOSHIMURA2), Hiroe IGAMI2), Hiromi TAKAHASHI2), Satoshi ITO2), Ryohei MAKINO1), Sakuji KOBAYASHI2), Yoshinori MIZUNO2), Kohta OKADA2), Ryutaro MINAMI4), Tsuyoshi KARIYA4) and Tsuyoshi IMAI4)
1)
Department of Energy Engineering and Science, Nagoya University, Nagoya 464-8463, Japan
2)
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
3)
Research Center for Development of FIR, University of Fukui, Fukui 910-8507, Japan
4)
Plasma Research Center, University of Tsukuba, Tsukuba 305-8577, Japan
(Received 13 December 2012 / Accepted 21 February 2013 / Published 22 May 2013)

Abstract

To establish a method for suppressing the spurious radiation that interferes with collective Thomson scattering measurements with less degradation of the main mode output power, the frequency evolution, and the output power of the megawatt 77-GHz gyrotron were measured during operation under optimized parameters. According to a mode competition calculation, the main mode output power may be increased by setting a lower gyrotron anode voltage at a higher magnetic field strength in the gyrotron resonator. Although the output power increased from 300 kW to 530 kW without any spurious radiation when the optimized operational parameters were used, the output power was about 50% of that at a lower magnetic field strength, and thus the output pulse width was limited to 60 ms. When an approach using the optimized operational parameters and a PIN switch was applied, the output power increased to 800 kW without any harmful spurious radiation effect and the pulse width was expanded to 2 s.

Keywords

collective Thomson scattering, gyrotron, ECRH, LHD, ECE, mode competition

DOI: 10.1585/pfr.8.2402069

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References

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This paper may be cited as follows:

Shinya OGASAWARA, Shin KUBO, Masaki NISHIURA, Yoshinori TATEMATSU, Teruo SAITO, Kenji TANAKA, Takashi SHIMOZUMA, Yasuo YOSHIMURA, Hiroe IGAMI, Hiromi TAKAHASHI, Satoshi ITO, Ryohei MAKINO, Sakuji KOBAYASHI, Yoshinori MIZUNO, Kohta OKADA, Ryutaro MINAMI, Tsuyoshi KARIYA and Tsuyoshi IMAI, Plasma Fusion Res. 8, 2402069 (2013).