Plasma and Fusion Research

Volume 17, 2405009 (2022)

Regular Articles

Upgrade of ICRF Antennas by Utilizing Impedance Transformers in LHD
Kenji SAITO1,2), Tetsuo SEKI1), Hiroshi KASAHARA1), Ryosuke SEKI1,2), Shuji KAMIO1), Goro NOMURA1) and Motonari KANDA1)
1)
National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
2)
Department of Fusion Science, The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu 509-5292, Japan
(Received 26 December 2021 / Accepted 2 February 2022 / Published 18 March 2022)

Abstract

For the high-power and long-pulse ion cyclotron range of frequencies (ICRF) heating of plasma in the Large Helical Device (LHD), two types of ICRF antennas are used. One is the Field-Aligned-Impedance-Transforming (FAIT) antenna. It has an In-Vessel Impedance Transformer (IVIT) in the vacuum region of the antenna and shows the possibility of high-power injection despite the short antenna head. To enhance the performance more, an Ex-Vessel Impedance Transformer (EVIT) was attached outside the LHD vacuum vessel. As a result, the injectable power increased. The other is the Handshake form (HAS) antenna. Plasma can be efficiently heated by adjusting the phase difference between currents in straps. However, the injectable power from the HAS antenna was originally small. Therefore, later an EVIT was attached to it. Moreover, the transmission line in the vacuum region was remodeled to form an IVIT. By utilizing these impedance transformers, the performance of the HAS antenna was drastically improved.

Keywords

ICRF heating, FAIT antenna, HAS antenna, IVIT, EVIT, LHD

DOI: 10.1585/pfr.17.2405009

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