X-ray Measurements during Plasma Current Start-up Experiments using the lower hybrid wave on the TST-2 spherical tokamak

Takuma Wakatsuki, Akira Ejiri, Hidetoshi Kakuda, Yuichi Takase, Takanori Ambo, Hirokazu Furui, Takahiro Hashimoto, Junichi Hiratsuka, Hiroshi Kasahara, Kunihiko Kato, Ryuhei Kumazawa, Yoshihiko Nagashima, Kenji Saito, Takuya Sakamoto, Tetsuo Seki, Fujio Shimpo, Ryota Shino, Takahiro Shinya, Masateru Sonehara, Osamu WatanabeTakashi Yamaguchi, Charles P. Moeller

    Research output: Contribution to journalArticle

    4 Citations (Scopus)

    Abstract

    Non-inductive plasma current start-up experiments using RF power in the lower hybrid frequency range is being conducted on the TST-2 spherical tokamak. Plasma currents of up to 15 kA have been achieved. The effect of direct current drive can be seen by comparing the cases with co-drive and counter-drive. X-rays in various energy ranges were measured to investigate the interaction between the wave and the electrons. Soft X-ray (SX) measurements revealed that the perpendicular SX emission increased significantly as the plasma current increased, and that the tangential SX emission in the direction of RF drive was enhanced more strongly in the co-drive case compared to the counter-drive case. These observations imply that the fast electrons accelerated by the lower hybrid wave contribute to the plasma current. However, RF amplitude modulation experiments showed that the confinement time of these fast electrons are very short (less than 0.05 ms), much shorter than the collisional slowing down time. Hard X-ray spectral measurements showed that the radiation temperature of fast electrons in the co-direction for current drive was higher than that in the counter-direction. These observations are consistent with the existence of RF-driven fast electrons.

    Original languageEnglish
    JournalIEEJ Transactions on Fundamentals and Materials
    Volume132
    Issue number7
    DOIs
    Publication statusPublished - Oct 5 2012

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    Plasmas
    X rays
    Electrons
    Experiments
    Amplitude modulation
    Radiation
    Temperature

    All Science Journal Classification (ASJC) codes

    • Electrical and Electronic Engineering

    Cite this

    X-ray Measurements during Plasma Current Start-up Experiments using the lower hybrid wave on the TST-2 spherical tokamak. / Wakatsuki, Takuma; Ejiri, Akira; Kakuda, Hidetoshi; Takase, Yuichi; Ambo, Takanori; Furui, Hirokazu; Hashimoto, Takahiro; Hiratsuka, Junichi; Kasahara, Hiroshi; Kato, Kunihiko; Kumazawa, Ryuhei; Nagashima, Yoshihiko; Saito, Kenji; Sakamoto, Takuya; Seki, Tetsuo; Shimpo, Fujio; Shino, Ryota; Shinya, Takahiro; Sonehara, Masateru; Watanabe, Osamu; Yamaguchi, Takashi; Moeller, Charles P.

    In: IEEJ Transactions on Fundamentals and Materials, Vol. 132, No. 7, 05.10.2012.

    Research output: Contribution to journalArticle

    Wakatsuki, T, Ejiri, A, Kakuda, H, Takase, Y, Ambo, T, Furui, H, Hashimoto, T, Hiratsuka, J, Kasahara, H, Kato, K, Kumazawa, R, Nagashima, Y, Saito, K, Sakamoto, T, Seki, T, Shimpo, F, Shino, R, Shinya, T, Sonehara, M, Watanabe, O, Yamaguchi, T & Moeller, CP 2012, 'X-ray Measurements during Plasma Current Start-up Experiments using the lower hybrid wave on the TST-2 spherical tokamak', IEEJ Transactions on Fundamentals and Materials, vol. 132, no. 7. https://doi.org/10.1541/ieejfms.132.485
    Wakatsuki, Takuma ; Ejiri, Akira ; Kakuda, Hidetoshi ; Takase, Yuichi ; Ambo, Takanori ; Furui, Hirokazu ; Hashimoto, Takahiro ; Hiratsuka, Junichi ; Kasahara, Hiroshi ; Kato, Kunihiko ; Kumazawa, Ryuhei ; Nagashima, Yoshihiko ; Saito, Kenji ; Sakamoto, Takuya ; Seki, Tetsuo ; Shimpo, Fujio ; Shino, Ryota ; Shinya, Takahiro ; Sonehara, Masateru ; Watanabe, Osamu ; Yamaguchi, Takashi ; Moeller, Charles P. / X-ray Measurements during Plasma Current Start-up Experiments using the lower hybrid wave on the TST-2 spherical tokamak. In: IEEJ Transactions on Fundamentals and Materials. 2012 ; Vol. 132, No. 7.
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    abstract = "Non-inductive plasma current start-up experiments using RF power in the lower hybrid frequency range is being conducted on the TST-2 spherical tokamak. Plasma currents of up to 15 kA have been achieved. The effect of direct current drive can be seen by comparing the cases with co-drive and counter-drive. X-rays in various energy ranges were measured to investigate the interaction between the wave and the electrons. Soft X-ray (SX) measurements revealed that the perpendicular SX emission increased significantly as the plasma current increased, and that the tangential SX emission in the direction of RF drive was enhanced more strongly in the co-drive case compared to the counter-drive case. These observations imply that the fast electrons accelerated by the lower hybrid wave contribute to the plasma current. However, RF amplitude modulation experiments showed that the confinement time of these fast electrons are very short (less than 0.05 ms), much shorter than the collisional slowing down time. Hard X-ray spectral measurements showed that the radiation temperature of fast electrons in the co-direction for current drive was higher than that in the counter-direction. These observations are consistent with the existence of RF-driven fast electrons.",
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    AU - Ejiri, Akira

    AU - Kakuda, Hidetoshi

    AU - Takase, Yuichi

    AU - Ambo, Takanori

    AU - Furui, Hirokazu

    AU - Hashimoto, Takahiro

    AU - Hiratsuka, Junichi

    AU - Kasahara, Hiroshi

    AU - Kato, Kunihiko

    AU - Kumazawa, Ryuhei

    AU - Nagashima, Yoshihiko

    AU - Saito, Kenji

    AU - Sakamoto, Takuya

    AU - Seki, Tetsuo

    AU - Shimpo, Fujio

    AU - Shino, Ryota

    AU - Shinya, Takahiro

    AU - Sonehara, Masateru

    AU - Watanabe, Osamu

    AU - Yamaguchi, Takashi

    AU - Moeller, Charles P.

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