Energy confinement and high-k turbulence on HT-7 tokamak

A CO2 collective scattering system has been developed to measure medium and high-k density fluctuation on HT-7 tokamak. Energy confinement and high-k density fluctuation are studied in ohmic discharges. The saturation of confinement was observed at approximately n¯e>2.5×1019 m−3. For kθ=23 cm−1 turbulence, it is found that fluctuation levels have great increase for n¯e>2.5×1019 m−3, and simultaneously a high frequency turbulence feature appear in the frequency spectra. For kθ=14 cm−1 turbulence, it is observed that fluctuation levels have no changes in uncertainties and the spectra are similar at all discharges in this experiment.