Plasma and Fusion Research

Volume 12, 1202041 (2017)

Rapid Communications

Observation of High Impurity Ion Temperatures in ECW/EBW Sustained Plasmas on LATE

Akira EJIRI, Hitoshi TANAKA¹⁾, Wataru TAKAHASHI, Akito SATO, Yuichi TAKASE, Naoto TSUJII, Masaki UCHIDA¹⁾ and Takashi MAEKAWA¹⁾

: Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8561, Japan
1): Graduate School of Energy Science, Kyoto University, Kyoto 606-8502, Japan

(Received 10 August 2017 / Accepted 5 September 2017 / Published 16 October 2017)

Abstract

Carbon and oxygen impurity line emissions from LATE spherical tokamak plasmas were measured using a visible spectrometer. A plasma current of approximately 10 kA was sustained by ECW/EBW with a frequency of 5 GHz and a power of 130 kW. Emissions of CIII (464.7 nm), OV (278.1 nm) and CV (227.1 nm) were observed, and the ion temperatures calculated from the Doppler broadening reached 40 ± 8, 110 ± 10 and 130 ± 30 eV, respectively. The high ion temperatures cannot be explained by collisional heating from electrons, suggesting that the ions are directly heated via unidentified mechanisms.

Keywords

electron cyclotron wave, electron Bernstein wave, current drive, spherical tokamak, ion temperature

DOI: 10.1585/pfr.12.1202041

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