Parametric Decay Wave Observation in HFS X-Mode Injection in QUEST*)

Shinichiro Kojima, Hatem Elserafy, Kazuaki Hanada, Hiroshi Idei, Ryuya Ikezoe, Yoshihiko Nagashima, Makoto Hasegawa, Takumi Onchi, Kengoh Kuroda, Kazuo Nakamura, Takahiro Murakami, Masaharu Fukuyama, Ryoya Kato, Ryota Yoneda, Masayuki Ono, Akira Ejiri, Yuichi Takase, Sadayoshi Murakami

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1 Citation (Scopus)


The parametric decay wave (PDW) caused by three-wave parametric decay process was measured in a plasma-injecting X-mode electron cyclotron wave (ECW) from the high field side (HFS) of the Q-shu University Experimental Steady-State Spherical Tokamak (QUEST). The intensity of the low-frequency PDW on the HFS X-mode injection was significantly enhanced over the O-mode ECW injection from the low field side (LFS), where the mode conversion to electron Bernstein wave (EBW) was not expected. As the comparison was executed using plasmas with the same magnetic field and injection power, the wave injection method was considered as the primary cause of the difference in the PDWexcitation. The frequency range of the low-frequency PDWwas consistent with that of the lower hybrid wave (LHW) range, which was expected to be excited during the mode conversion to EBW. The low-frequency PDWintensity evolved in response to the plasma density, plasma current and injection power. This observation suggests that the low-frequency PDW intensity is a reliable indicator for the efficient mode conversion to EBW.

Original languageEnglish
Pages (from-to)2402063-1-2402063-6
JournalPlasma and Fusion Research
Publication statusPublished - 2020

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics


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