ELM Control Physics with Impurity Seeding and LHCD in the HL- 2A Tokamak

ELM control with impurity seeding and lower hybrid current drive (LHCD) have been achieved in the HL-2A tokamak. The divertor peak heat load released by ELM has been significantly reduced during the mitigation phase. It has been found that the mitigation of ELMs in these experiments is due to the pedestal turbulence enhancement generated by the external source induced. The E×B velocity shear induced by LHCD and impurity seeding modifies the turbulence radial wavenumber (kr) spectrum by varying the averaged radial wavenumber from large negative value to zero, reducing the turbulence dissipation term (~kr ). A modified turbulence spectral shift model has been used to simulate the experimental observations. A critical growth rate γ0 for the turbulence regulation is identified in this model and experimentally determined. Good agreement has been found between experiment and theory for the regulation of the turbulence intensity by its averaged radial wavenumber.