Investigation of toroidal rotation modulation and momentum transport with electrode biasing in J-TEXT tokamak

The toroidal rotation modulation and momentum transport have been investigated in the J-TEXT tokamak using a modulated electrode biasing (EB) along with measurements of the toroidal rotation (V-phi) by a spectrometer and a Langmuir-Mach probe array. The amplitude A(v) and phase delay phi(v) (relative to the phase of the biasing current, I-EB) of the rotation modulation are extracted through sine-fitting approaches. It is found that the A(v) increases with increasing I-EB and the phi(v) becomes larger when the modulation frequency increases. It has been estimated that the momentum transport time across a radial range from r/a similar to 0.9 to 0.65 is about 10 ms, shorter than the half of modulation period (similar to 30 ms). Using the perturbation analysis technique, the toroidal momentum transport coefficients, including momentum diffusivity chi(phi) and convective velocity V-conv, have been calculated and an inward pinch effect has been observed. In addition, the impact of the EB on the ion temperature and intrinsic rotation and the toroidal rotation difference between impurity and main ions are analyzed and discussed.