W-band millimeter-wave back-scattering system for high wavenumber turbulence measurements in LHD

A 90 GHz W-band millimeter-wave back-scattering system is designed and installed for measuring electron scale turbulence (k⊥ρs ∼ 40). A metal lens relay antenna is used for in-vessel beam focusing, and a beam diameter of less than 40 mm is achieved in the plasma core region. This antenna can be stee...

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Bibliographic Details
Published in:Review of scientific instruments 2021-04, Vol.92 (4), p.043536-043536
Main Authors: Tokuzawa, T., Tanaka, K., Tsujimura, T., Kubo, S., Emoto, M., Inagaki, S., Ida, K., Yoshinuma, M., Watanabe, K. Y., Tsuchiya, H., Ejiri, A., Saito, T., Yamamoto, K.
Format: Article
Language:English
Subjects:
Antennas
Background noise
Corrugated waveguides
Diameters
Millimeter waves
Scattering
Scientific apparatus & instruments
Transmission loss
Turbulence
Wavelengths
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Summary:A 90 GHz W-band millimeter-wave back-scattering system is designed and installed for measuring electron scale turbulence (k⊥ρs ∼ 40). A metal lens relay antenna is used for in-vessel beam focusing, and a beam diameter of less than 40 mm is achieved in the plasma core region. This antenna can be steered at an angle of 159° ± 6°, which almost covers the plasma radius. The estimated size of the scattering volume is ∼105 mm at the edge and 135 mm at the core, respectively. A 60 m corrugated waveguide is used to achieve a low transmission loss of ∼8 dB. A heterodyne detection system for millimeter-wave circuits with probing power modulation can distinguish the scattered signal from background noise.
ISSN:0034-6748
1089-7623
DOI:10.1063/5.0043474