Plasma current start-up experiments using a dielectric-loaded waveguide array antenna in the TST-2 spherical tokamak

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, M. Sonehara, H. Togashi, S. Tsuda, N. TsujiiT. Yamaguchi

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    5 Citations (Scopus)

    Abstract

    Plasma current start-up and ramp-up using the lower hybrid wave (LHW) were investigated on the TST-2 spherical tokamak. The LHW was launched by a dielectric-loaded waveguide array (grill) antenna. The antenna-plasma coupling of this antenna deteriorates as the input power exceeds several kW. This deterioration is believed to be caused by the density depletion due to the ponderomotive force. This conjecture was confirmed by the measurement of density reduction and the result of a non-linear full wave numerical calculation based on the finite element method (FEM). The plasma current was started and ramped up to 10 kA using this antenna. The ability of this grill antenna to excite the LHW with different n = ck/ω was used to identify the most favourable n spectrum for plasma current ramp-up. It was found that effective current drive can be achieved by the LHW with n less than 6. However, even in this case, the energetic electrons which account for a large fraction of the driven current, are lost rapidly because the poloidal field generated by this level of plasma current is not sufficient to confine high energy electrons.

    Original languageEnglish
    Article number093014
    JournalNuclear Fusion
    Volume54
    Issue number9
    DOIs
    Publication statusPublished - Aug 19 2014

    All Science Journal Classification (ASJC) codes

    • Nuclear and High Energy Physics
    • Condensed Matter Physics

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    Wakatsuki, T., Ejiri, A., Shinya, T., Takase, Y., Furui, H., Hiratsuka, J., Imamura, K., Inada, T., Kakuda, H., Kasahara, H., Nagashima, Y., Nakamura, K., Nakanishi, A., Oosako, T., Saito, K., Seki, T., Sonehara, M., Togashi, H., Tsuda, S., ... Yamaguchi, T. (2014). Plasma current start-up experiments using a dielectric-loaded waveguide array antenna in the TST-2 spherical tokamak. Nuclear Fusion, 54(9), [093014]. https://doi.org/10.1088/0029-5515/54/9/093014