Observation of Low Frequency Ion Mode Turbulence in Tokamak Plasma

Features of a low frequency ion mode were observed together with the electron drift wave type fluctuations by a Langmuir probe array in the bulk plasma inside the velocity shear layer in the KT-5C tokamak. The measured ion mode wavenumber, scaling of the ion mode with chord-averaged density, and the estimated η_i value suggest that the observed ion mode may be the theoretically predicted η_i mode driven by ion temperature gradient.