[Table of Contents]

Plasma and Fusion Research

Volume 6, 1402003 (2011)

Regular Articles


First Ohmic Discharge Assisted with RF Power in QUEST Spherical Tokamak
Osamu MITARAI, Kazuo NAKAMURA1), Saya TASHIMA1), Makoto HASEGAWA1), Hiroshi IDEI1), Mizuki SAKAMOTO1), Kazuaki HANADA1), Hideki ZUSHI1), Kohnosuke SATO1), Masaki ISHIGURO1), Hai Qing LIU1), Yuta HIGASHIZONO1), Aki HIGASHIJIMA1), Hisatoshi NAKASHIMA1), Shoji KAWASAKI1), Yuichi TAKASE2), Takashi MAEKAWA3) and Nobuhiro NISHINO4)
Liberal Arts Education Center, Kumamoto Campus, Tokai University, 9-1-1 Toroku, Kumamoto 862-8652, Japan
1)
Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan
2)
Graduate School of Frontier Sciences and Graduate School of Science, University of Tokyo, Kashiwa 277-85611, Japan
3)
Graduate School of Energy Science, Kyoto University, Kyoto 606-8502, Japan
4)
Department of Engineering, Hiroshima Univeristy, Higashi-Hiroshima 739-8527, Japan
(Received 23 October 2009 / Accepted 17 November 2010 / Published 8 February 2011)

Abstract

Ohmic plasma currents of up to 17 kA with a discharge duration of 0.32 s have been obtained in the Kyushu University Experiment with Steady-State Spherical Tokamak (QUEST) with the help of electron cyclotron wave (ECW) and cancellation coils (CCs). The CCs, originally installed to create a field null in the plasma breakdown phase, are essential for producing plasma current in QUEST. Although the ohmic coil current is initially biased and then reduced completely to zero to induce the plasma current in 15-20 ms, we demonstrate that the flat top of the plasma current exceeding 20 ms is maintained by the vertical field after the ohmic current is switched off. This type of operation is quite favorable for extending pulsed operation to the steady state by electron Bernstein wave current drive (EBCD).


Keywords

spherical tokamak, current start-up, ohmic clamp, cancellation coil, ECW, vertical field

DOI: 10.1585/pfr.6.1402003


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This paper may be cited as follows:

Osamu MITARAI, Kazuo NAKAMURA, Saya TASHIMA, Makoto HASEGAWA, Hiroshi IDEI, Mizuki SAKAMOTO, Kazuaki HANADA, Hideki ZUSHI, Kohnosuke SATO, Masaki ISHIGURO, Hai Qing LIU, Yuta HIGASHIZONO, Aki HIGASHIJIMA, Hisatoshi NAKASHIMA, Shoji KAWASAKI, Yuichi TAKASE, Takashi MAEKAWA and Nobuhiro NISHINO, Plasma Fusion Res. 6, 1402003 (2011).