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

    Research output: Contribution to journalArticle

    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

    Fingerprint

    dielectric waveguides
    plasma currents
    antenna arrays
    antennas
    ramps
    plasma antennas
    ponderomotive forces
    deterioration
    high energy electrons
    finite element method
    depletion
    electrons

    All Science Journal Classification (ASJC) codes

    • Nuclear and High Energy Physics
    • Condensed Matter Physics

    Cite this

    Wakatsuki, T., Ejiri, A., Shinya, T., Takase, Y., Furui, H., Hiratsuka, J., ... 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

    Plasma current start-up experiments using a dielectric-loaded waveguide array antenna in the TST-2 spherical tokamak. / 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.; Tsujii, N.; Yamaguchi, T.

    In: Nuclear Fusion, Vol. 54, No. 9, 093014, 19.08.2014.

    Research output: Contribution to journalArticle

    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, Tsujii, N & Yamaguchi, T 2014, 'Plasma current start-up experiments using a dielectric-loaded waveguide array antenna in the TST-2 spherical tokamak', Nuclear Fusion, vol. 54, no. 9, 093014. https://doi.org/10.1088/0029-5515/54/9/093014
    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. ; Tsujii, N. ; Yamaguchi, T. / Plasma current start-up experiments using a dielectric-loaded waveguide array antenna in the TST-2 spherical tokamak. In: Nuclear Fusion. 2014 ; Vol. 54, No. 9.
    @article{0a9088fc90754a038fd03edf8637475b,
    title = "Plasma current start-up experiments using a dielectric-loaded waveguide array antenna in the TST-2 spherical tokamak",
    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.",
    author = "T. Wakatsuki and A. Ejiri and T. Shinya and Y. Takase and H. Furui and J. Hiratsuka and K. Imamura and T. Inada and H. Kakuda and H. Kasahara and Y. Nagashima and K. Nakamura and A. Nakanishi and T. Oosako and K. Saito and T. Seki and M. Sonehara and H. Togashi and S. Tsuda and N. Tsujii and T. Yamaguchi",
    year = "2014",
    month = "8",
    day = "19",
    doi = "10.1088/0029-5515/54/9/093014",
    language = "English",
    volume = "54",
    journal = "Nuclear Fusion",
    issn = "0029-5515",
    publisher = "IOP Publishing Ltd.",
    number = "9",

    }

    TY - JOUR

    T1 - Plasma current start-up experiments using a dielectric-loaded waveguide array antenna in the TST-2 spherical tokamak

    AU - Wakatsuki, T.

    AU - Ejiri, A.

    AU - Shinya, T.

    AU - Takase, Y.

    AU - Furui, H.

    AU - Hiratsuka, J.

    AU - Imamura, K.

    AU - Inada, T.

    AU - Kakuda, H.

    AU - Kasahara, H.

    AU - Nagashima, Y.

    AU - Nakamura, K.

    AU - Nakanishi, A.

    AU - Oosako, T.

    AU - Saito, K.

    AU - Seki, T.

    AU - Sonehara, M.

    AU - Togashi, H.

    AU - Tsuda, S.

    AU - Tsujii, N.

    AU - Yamaguchi, T.

    PY - 2014/8/19

    Y1 - 2014/8/19

    N2 - 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.

    AB - 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.

    UR - http://www.scopus.com/inward/record.url?scp=84929382015&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=84929382015&partnerID=8YFLogxK

    U2 - 10.1088/0029-5515/54/9/093014

    DO - 10.1088/0029-5515/54/9/093014

    M3 - Article

    AN - SCOPUS:84929382015

    VL - 54

    JO - Nuclear Fusion

    JF - Nuclear Fusion

    SN - 0029-5515

    IS - 9

    M1 - 093014

    ER -