Effects of negative and positive bias voltages on turbulence characteristics in J-TEXT tokamak

Abstract

The effects of positive and negative bias voltages on the turbulence characteristics in edge plasmas of J-TEXT are studied using Langmuir probe arrays. The experimental results illustrate that the turbulent particle transport fluxes are suppressed in both positive and negative bias cases, while the suppression mechanisms are quite different. For the positive bias (+300 V), the long-range correlation (LRC) structures with frequencies of about 10 ~ 30 kHz are generated, which are beneficial for the turbulent transport suppression. In the -300 V bias case, no LRCs appear, while a strong mean flow shear exists which can reduce the amplitudes of potential and density fluctuations and thus decreases the turbulent transport.