Plasma and Fusion Research

Volume 7, 2402020 (2012)

Regular Articles

ECCD Experiment Using an Upgraded ECH System on LHD

Yasuo YOSHIMURA, Shin KUBO, Takashi SHIMOZUMA, Hiroe IGAMI, Hiromi TAKAHASHI, Masaki NISHIURA, Shinya OGASAWARA¹⁾, Ryohei MAKINO¹⁾, Katsumi IDA, Mikiro YOSHINUMA, Satoru SAKAKIBARA, Kenji TANAKA, Kazumichi NARIHARA, Takashi MUTOH, Hiroshi YAMADA, Kazunobu NAGASAKI²⁾, Nikolai B. MARUSHCHENKO³⁾ and Yuri TURKIN³⁾

: National Institute for Fusion Science, Toki 509-5292, Japan
1): Department of Energy and Technology, Nagoya University, Nagoya 464-8463, Japan
2): Institute of Advanced Energy, Kyoto University, Uji 611-0011, Japan
3): Max-Planck-Institut for Plasmaphysik, IPP-EURATOM Association, D-17491 Greifswald, Germany

(Received 9 December 2011 / Accepted 13 February 2012 / Published 15 March 2012)

Abstract

Electron cyclotron current drive (ECCD) is an attractive tool for controlling plasmas. In the large helical device (LHD), ECCD experiments have been performed by using an EC-wave power source, gyrotron, with a frequency of 84 GHz. The maximum driven current was ∼9 kA with 100 kW injection power to plasma and 8 s duration of EC-wave pulse. These years, high-power and long-pulse 77 GHz gyrotrons were newly installed. An ECCD experiment with 775 kW injection power was performed. The 77 GHz waves of 8 s pulse duration sustained the plasmas. The EC-wave beam direction was scanned toroidally, keeping the beam direction aiming at the magnetic axis in X-mode polarization. In spite of the change in the EC-wave beam direction, plasma parameters such as the line-average electron density, the central electron temperature and the plasma stored energy were kept nearly the same values for the discharges, ∼0.3 × 10¹⁹ m⁻³, ∼3 keV and ∼30 kJ, except for the plasma current. The plasma current showed a systematic change with the change in the beam direction for ECCD, and at an optimum direction with N_// ∼ −0.3, the plasma current reached its maximum, ∼40 kA. Also, current drive efficiency normalized with density and power was improved by 50% compared with that at the former 84 GHz ECCD experiment.

Keywords

electron cyclotron current drive, ECCD, plasma current, gyrotron, LHD, TRAVIS

DOI: 10.1585/pfr.7.2402020

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This paper may be cited as follows:

Yasuo YOSHIMURA, Shin KUBO, Takashi SHIMOZUMA, Hiroe IGAMI, Hiromi TAKAHASHI, Masaki NISHIURA, Shinya OGASAWARA, Ryohei MAKINO, Katsumi IDA, Mikiro YOSHINUMA, Satoru SAKAKIBARA, Kenji TANAKA, Kazumichi NARIHARA, Takashi MUTOH, Hiroshi YAMADA, Kazunobu NAGASAKI, Nikolai B. MARUSHCHENKO and Yuri TURKIN, Plasma Fusion Res. 7, 2402020 (2012).