Results of lower hybrid wave experiments using a dielectric loaded waveguide array antenna on TST-2

T. Wakatsuki, A. Ejiri, T. Shinya, Y. Takase, H. Furui, J. Hiratsuka, K. Imamura, T. Inada, H. Kakuda, H. Kasahara, Y. Nagashima, K. Nakamura, A. Nakanishi, T. Oosako, K. Saito, T. Seki, F. Shimpo, M. Sonehara, H. Togashi, S. TsudaN. Tsujii, T. Yamaguchi

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    1 Citation (Scopus)


    Lower hybrid current drive experiments were performed on the TST-2 spherical tokamak (R = 0.38 m, a = 0.25 m, Bt = 0.3 T, Ip = 0.1 MA). A waveguide array antenna consisting of four dielectric (alumina, εr = 10.0) loaded waveguides was used. The coupling characteristics were investigated over a wide range of input power (0.1 W - 40 kW). The reflection coefficient of this antenna increased when the input power exceeded approximately 1 kW. This result was compared with a numerical simulation based on the finite element method (FEM). The ponderomotive effect was calculated for the wave field calculated by COMSOL [1]. This calculation also showed variation of the reflection coefficient with the input power. Non-inductive plasma current start-up to 10 kA was demonstrated using 40 kW of lower hybrid wave (LHW) power. The current drive figure of merit (ηCD=IpneR/PRF) of this antenna was higher than that obtained using the combline antenna, which is designed to excite a travelling fast wave. The best current drive efficiency was obtained in the case in which the n (= ck/ω) spectrum of the excited LHW was peaked around 9 and the toroidal field was higher than in previous experiments.

    Original languageEnglish
    Title of host publicationRadiofrequency Power in Plasmas - Proceedings of the 20th Topical Conference
    PublisherAmerican Institute of Physics Inc.
    Number of pages4
    ISBN (Print)9780735412101
    Publication statusPublished - 2014
    Event20th Topical Conference on Radiofrequency Power in Plasmas - Sorrento, Italy
    Duration: Jun 25 2013Jun 28 2013

    Publication series

    NameAIP Conference Proceedings
    ISSN (Print)0094-243X
    ISSN (Electronic)1551-7616


    Other20th Topical Conference on Radiofrequency Power in Plasmas

    All Science Journal Classification (ASJC) codes

    • Physics and Astronomy(all)


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