Plasma and Fusion Research

Volume 14, 1205038 (2019)

Rapid Communications

HFS Injection of X-Mode for EBW Conversion in QUEST
Hatem ELSERAFY, Kazuaki HANADA1), Kengoh KURODA1), Hiroshi IDEI1), Ryota YONEDA2), Canbin HUANG1), Shinichiro KOJIMA, Makoto HASEGAWA1), Yoshihiko NAGASHIMA1), Takumi ONCHI1), Ryuya IKEZOE1), Aki HIGASHIJIMA1), Takahiro NAGATA1), Shoji KAWASAKI1), Shun SHIMABUKURO1), Nicola BERTELLI3) and Masayuki ONO3)
IGSES, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
1)
TRIAM, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
2)
National Institute for Fusion Science, Toki 509-5292, Japan
3)
Princeton Plasma Physics Laboratory, Princeton, NJ 08540, USA
(Received 7 December 2018 / Accepted 7 January 2019 / Published 22 March 2019)

Abstract

High field side (HFS) injection of eXtra-ordinary X-mode for electron Bernstein wave (EBW) conversion was conducted in the QUEST tokamak. Radio frequency (RF; 8.2 GHz) power was delivered from the low field side (LFS) to the high field side HFS through waveguides, and from the HFS placed 20 cm above the mid-plane of the vacuum vessel. The aim was to compare the RF launches from the LFS and HFS. The plasma brightness, measured by a fast camera, as well as the Hα signal captured along the mid-plane, was noticeably higher in the HFS launch than in the LFS launch. The HFS injection achieved a plasma current of approximately 130 A, versus 35A in the LFS injection. The electron density ne predicted from the position of the upper hybrid resonance agreed with the line-averaged ne measured by an interferometer, confirming the effective conversion and subsequent damping of the EBW mode. The RF leakage of the HFS injection was less than one-sixth that of the LFS injection. These results indicate that HFS delivers better RF coupling and conversion efficiency to EBW than LFS injection. Such efficient plasma heating via EBW will significantly enhance the plasma production.

Keywords

HFS launch, EBW, plasma production

DOI: 10.1585/pfr.14.1205038

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