Roles of turbulence and E×B flow shear during nonlocal transport on the HL-2A tokamak

In this work, nonlocal experiments with repetitive supersonic molecular beam injection (SMBI) have been carried out on the HL-2A tokamak. The plasma rotation and turbulent structures during nonlocal response are reported by a multi-channel Doppler backscattering reflectometer. The correlations of the turbulent structures, plasma rotation and their association with the strength of the nonlocal effect are studied. It is found that the plasma rotation has a significant increase at the transient Te transition region (r/a ~0.5). The high frequency fluctuation (~100 kHz) is significantly decreased and the low frequency fluctuation (~10 kHz) is increased. The increase of the plasma rotation and suppression of high frequency fluctuation around the Te transition region suggest that the E×B flow shear may play crucial roles during the nonlocal response.