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Improvement in Flexibility of ECCD by Upgraded ECH Antenna System on LHD

Yasuo YOSHIMURA, Yoshiro NARUSHIMA, Shin KUBO, Takashi SHIMOZUMA, Hiroe IGAMI, Hiromi TAKAHASHI, Toru I. TSUJIMURA, Ryohei MAKINO, Satoshi ITO, Kota OKADA, Sakuji KOBAYASHI, Yoshinori MIZUNO, Yuki GOTO¹⁾, Ryuichi SAKAMOTO, Akira EJIRI²⁾, Takashi MUTOH, Hiroshi YAMADA, Akio KOMORI, Yasuhiko TAKEIRI and the LHD Experiment Group

National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan

1)

Graduate School of Engineering, Nagoya University, Nagoya 464-8601, Japan

2)

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

(Received 29 November 2015 / Accepted 23 February 2016 / Published 15 April 2016)

Abstract

The power injection system for electron cyclotron heating (ECH) and electron cyclotron current drive (ECCD) was modified and upgraded. An outside horizontal port 2-O on the Large Helical Device (LHD) was furnished with two antenna systems for the EC-waves of the frequencies of 77 and 154 GHz, respectively. In addition to them, two new antenna systems for 77 and 154 GHz waves were installed in the 2-O port. Each antenna in the 2-O port has wide range of EC-wave beam direction control so that these are suitable for ECCD which requires toroidally oblique EC-wave beam injection. In the LHD 18th experimental campaign in 2014-2015, an ECCD experiment with second harmonic resonance condition, on-axis magnetic field of 1.375 T for 77 GHz waves, was performed in which some combination patterns of two 77 GHz ECCDs were applied. The discharges of dual co- and dual counter-ECCDs showed remarkable plasma currents of ∼±26 kA in both of the co- and counter-directions, by 6 s pulse duration and injection powers of 366 and 365 kW. The new antenna has nearly the same capability for ECCD with that of the existing antenna. The improvement in the flexibility of the ways of applying plural ECCDs will offer a highly useful tool for investigations on the phenomena concerning with the plasma current such as magnetohydro-dynamics.

Copyright (c) 2016 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

electron cyclotron current drive, ECCD, LHD

DOI: 10.1585/pfr.11.2402036

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