Correlation ECE Measurement System for Electron Temperature Fluctuations in LHD

Abstract Understanding turbulence behavior in high-temperature plasmas is crucial for elucidating the mechanisms behind anomalous transport phenomena. The correlation electron cyclotron emission (cECE) technique is widely used to measure electron temperature fluctuations associated with turbulence in high-temperature plasmas. A new radial cECE system has been installed in the Large Helical Device (LHD), incorporating tunable bandpass filters (BPFs). Effective spectral decorrelation was obtained by increasing the center frequency separation between two BPFs. As an initial result using the cECE system, relatively low-coherence electron temperature fluctuations were observed in the LHD, with an estimated fluctuation level below 1%.