Identification of waves in the lower-hybrid frequency range in the scrape-off layer plasma of Alcator C-Mod

We report polarization resolved measurements of the parallel refractive index $N_∥≡ck_∥/w$ of the driven RF waves in the lower hybrid (LH) range of frequencies are performed using arrays of RF magnetic probes in the scrape-off layer plasma of Alcator C-Mod. The measured $N_∥$ of the RF magnetic fiel...

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Bibliographic Details
Published in:Nuclear fusion 2016-12, Vol.57 (3)
Main Authors: Shinya, Takahiro, Gyou Baek, Seung, Wallace, Gregory M., Shiraiwa, Syun’ichi, Takase, Yuichi, Parker, Ronald R., Bonoli, Paul T., Brunner, Dan, Faust, Ian, LaBombard, Brian L., Wukitch, Steve
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
lower hybrid wave
SOL
tokamak
wave measurement
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Summary:We report polarization resolved measurements of the parallel refractive index $N_∥≡ck_∥/w$ of the driven RF waves in the lower hybrid (LH) range of frequencies are performed using arrays of RF magnetic probes in the scrape-off layer plasma of Alcator C-Mod. The measured $N_∥$ of the RF magnetic field component parallel to the background magnetic field is about –1.6, which corresponds to the peak of the launched LH $N_∥$ spectrum. Based on the wave dispersion relationship, this wave is identified as the LH slow wave. On the other hand, the RF magnetic field component perpendicular to the magnetic field is found to have a lower $N_∥$ of –1.2, and is detected only near the last closed flux surface. This wave is identified as the LH fast wave generated by slow-fast wave mode conversion.
ISSN:0029-5515
1741-4326