Detection of a new parametric decay instability branch in TST-2 during high harmonic fast wave heating

Y. Adachi, A. Ejiri, Y. Takase, O. Watanabe, T. Oosako, H. Tojo, S. Kainaga, T. Masuda, M. Sasaki, J. Sugiyama, T. Yamaguchi

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Abstract

Parametric decay instability (PDI) is often observed in the TST-2 spherical tokamak during high harmonic fast wave heating by rf pickup probes. The frequency spectrum exhibits lower and upper sideband peaks in addition to the pump wave at f0 =21 MHz. Two types of PDI are observed. One is the well-known decay into the ion-cyclotron quasimode (n fci) and the ion Bernstein wave (f0 -n fci). The other is a newly found decay with the sideband frequency between f0 and f0 - fci. The frequency difference between this sideband and the pump increases in proportion to Bt. Moreover, high-speed visible light measuring systems with photomultiplier tubes or hybrid photodetectors viewing the plasma core detected oscillation of light emission at around f0.

Original languageEnglish
Article number10F507
JournalReview of Scientific Instruments
Volume79
Issue number10
DOIs
Publication statusPublished - Nov 10 2008
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Instrumentation

Cite this

Adachi, Y., Ejiri, A., Takase, Y., Watanabe, O., Oosako, T., Tojo, H., ... Yamaguchi, T. (2008). Detection of a new parametric decay instability branch in TST-2 during high harmonic fast wave heating. Review of Scientific Instruments, 79(10), [10F507]. https://doi.org/10.1063/1.2955574