Validation of the Digital Correlation ECE Measurement Technique using Low-Frequency Fluctuation in LHD

Takahashi, Hayato; Inagaki, S.; Tokuzawa, T.; Tamura, N.; Nagayama, Y.

doi:10.1585/pfr.11.2402072

Cited by 1 publication

(2 citation statements)

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“…Subsequently, two signals denoted as S 1 (t) and S 2 (t) at different center frequency are selected utilizing digital band-pass filters. The spectra-averaging based digital C-ECE method presented in [6] gives the number of individual sectors 𝑁 a dependence on video bandwidth. The sensitivity is limited to ∼0.8% according to equation (2.3).…”

Section: Digital C-ece Methodsmentioning

confidence: 99%

“…In the filter bank system, the IF signal from 0.5 to 6 GHz is processed by bandpass filters with passbands of 100 or 200 MHz according to the conventional C-ECE methodology. Simultaneously, the fast digitizer system is utilized for the application of the digital C-ECE technique [6]. Both receivers are eligible to measure the 2nd harmonics X-mode emission for half-field LHD shots, as well as the fundamental harmonics O-mode emission for full-field LHD shots.…”

Section: Jinst 18 C10007mentioning

confidence: 99%

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Development of correlation ECE system for electron temperature fluctuation measurement in LHD

Gong,

Nishiura,

Yanai

et al. 2023

J. Inst.

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Correlation-ECE (C-ECE) is a standard method for investigating turbulence driven transport. This method allows electron temperature fluctuations that contain information on turbulent transport and independent thermal noise. The turbulence feature is extracted from a correlation analysis from two close locations. The A C-ECE system is utilized on the large helical device (LHD) to measure emission within the frequency range of 74–79.6 GHz. This system employs the spectral decorrelation method and serves as a collective Thomson scattering diagnostic receiver in the LHD. The C-ECE receiver system is comprised of a filter bank system with 32 band-pass filters and a fast digitizer system operating at a sampling rate of 12.5 GHz in the intermediate frequency (IF) stage. This study presents initial experimental results on temperature fluctuation spectra in the LHD, obtained through the C-ECE system using a coherency-based analysis method. An MHD mode at 5 kHz is excited from the onset of neutral beam injection in a magnetic probe, and coherence spectra are obtained from two C-ECE receiver systems. The temperature fluctuation results are derived from the coherence spectrum after bias removal and indicate a level of approximately 3% in the frequency range of 0 to 400 kHz. Further investigations will be conducted to explore drift wave turbulence activities and reconstruct the radial profile of temperature fluctuation in the LHD using the C-ECE receiver systems.

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Section: Digital C-ece Methodsmentioning

confidence: 99%

Section: Jinst 18 C10007mentioning

confidence: 99%