Impact of resonant magnetic perturbation on blob motion and structure using a gas puff imaging diagnostic on the HL-2A tokamak

Abstract

The impact of resonant magnetic perturbations (RMP) on blobs’ motions and structures in the SOL on the HL-2A tokamak is studied using a gas puff imaging diagnostic. Ellipse fitting is applied to study the structure and motion of blobs quantitatively. The radial locations, amplitudes and the scale sizes of blobs are obtained based on the fitted ellipse. Furthermore, based on the measurement of blob location, the radial and poloidal velocities of blobs are calculated. With the application of RMP, the edge poloidal shear flow is significantly weakened and the kr-kθ spectrum shifts from wider and less stretched to tilted. The application of RMP also causes the detected blob location to be much further into the far SOL and increases the blob amplitude. Blob’s poloidal velocity in the SOL is slowed. Larger size and longer lifetime of blobs are observed with RMP. With the application of RMP, stronger amplitude and larger size of blobs are detected in far SOL and they may cause more serious erosion problem to the first wall.

Gas puff imaging measurements during resonant magnetic perturbations on the HL-2A tokamak

“…According to the explanation, the displacement of inversion point is due to the accumulation effect of electron loss, which charges the edge electric potential positively. Figure 7 There are many possible factors affecting the frequency range of turbulence fluctuations, like the nonlinear energy transfer from higher frequency turbulence to lower frequency turbulence, larger turbulence structure [24] and the displacement of shear layer with the application of RMP. Future work will be focused on the detailed study of the turbulence frequency changes with RMP and the comparison between the experimental observations with the simulation work is being done.…”