Plasma and Fusion Research

Volume 16, 2405066 (2021)

Regular Articles

Development of the Molybdenum Millimeter Wave Target Tile for ECRH Antenna Alignment after the Evacuation in LHD
Hiroe IGAMI1), Ryoma YANAI1), Satoshi ITO1), Yasuo YOSHIMURA1), Shin KUBO1,2), Hiromi TAKAHASHI1,3), Takashi SHIMOZUMA1), Toru Ii TSUJIMURA1,3), Masaki NISHIURA1) and Yoshinori MIZUNO1)
1)
National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
2)
Nagoya University, Nagoya 464-8603, Japan
3)
SOKENDAI, (Graduate University for Advanced Studies), Toki 506-5292, Japan
(Received 7 December 2020 / Accepted 7 February 2021 / Published 7 June 2021)

Abstract

Alignment of the quasi-optical millimeter wave antenna for the electron cyclotron resonance heating (ECRH) can be required even after the evacuation of the vacuum vessel in fusion oriented plasma experimental devices. We developed a molybdenum millimeter wave target tile and installed it as one of the protection tiles of the vacuum vessel wall of the Large Helical Device (LHD) on the opposite side of the ECRH antennas. Inside the target tile, a sheathed thermocouple is mounted to measure the temperature increase during the millimeter wave injection toward this tile. In magnetic field configurations where neither the first nor the second electron cyclotron resonance (ECR) exists, the measured temperature increased sufficiently to be detected by the millimeter wave injection of approximately 100 kW for 0.1 s toward the target tile. Under the assumption that the distance between the target point that brings the largest temperature increase and the target point just above the thermocouple head gives the offset of the target point to be corrected, the offset of the antenna injection angle was confirmed with an accuracy of 0.4° with changing the target point shot by shot.

Keywords

ECRH, antenna alignment, millimeter wave target, thermal diffusion analysis

DOI: 10.1585/pfr.16.2405066

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