Edge Electrostatic Fluctuation Characteristics in the Sino-United Spherical Tokamak

Edge plasma parameters, including electron temperature T_e, density n_e, plasma potential Ф_p , radial electric field E_r and the corresponding fluctuations in the Sino-United Spherical Tokamak, have been systematically measured with Langmuir probe arrays. Wavenumber spectrum analyses show that edge fluctuations have a radial propagation character of the drift wave turbulence, with a characteristic radial phase velocity v_phr ～ 0.7 km.s^-1 in the scrape-off layer and vsuB>phr ～ 0.9-1.4km.s^-1 in the plasma edge.