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

Journal Article · 12 December 2016 · Nuclear Fusion

DOI: https://doi.org/10.1088/1741-4326/57/3/036005 · OSTI ID:1535578

Shinya, Takahiro ^[1]; Gyou Baek, Seung ^[2]; Wallace, Gregory M. ^[2]; Shiraiwa, Syun’ichi ^[2]; Takase, Yuichi ^[3]; Parker, Ronald R. ^[2]; Bonoli, Paul T. ^[2]; Brunner, Dan ^[2]; Faust, Ian ^[2]; LaBombard, Brian L. ^[2]; Wukitch, Steve

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1. University of Tokyo, Kashiwa (Japan); OSTI
2. Massachusetts Institute of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
3. University of Tokyo, Kashiwa (Japan)

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.

• Research Organization: Massachusetts Institute of Technology (MIT), Cambridge, MA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES)
• Grant/Contract Number: FC02-99ER54512
• OSTI ID: 1535578
• Journal Information: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 3 Vol. 57; ISSN 0029-5515
• Publisher: IOP ScienceCopyright Statement
• Country of Publication: United States
• Language: English