OV / 4 - 5 1 Overview of Experimental Results on the HL - 2 A Tokamak

The physics experiments on the HL-2A tokamak have been focused on confinement improvement, particle and thermal transport, zonal flow and turbulence, filament characteristics, energetic particle induced modes, and plasma fueling efficiency since 2008. ELMy H-mode discharges are achieved using combination of NBI heating with ECRH. The power threshold is found to increase with decrease of density, almost independent of the launching order of the ECRH and NBI heating power. The pedestal density profiles in the H-mode discharges are measured. The particle outward convection is observed during pump-out transient phase with ECRH. The negative density perturbation (pump-out) is observed to propagate much faster than the positive one caused by out-gassing. The core electron thermal transport reduction triggered by far-axis ECRH switch-off is investigated. The coexistence of low frequency zonal flow (LFZF) and geodesic acoustic mode (GAM) is observed. The dependence of the intensities of LFZFs and GAMs on safety factor and ECRH power is identified. The 3D spatial features of plasma filaments are measured and large-scale structures along a magnetic field line analyzed for the first time. The beta-induced Alfvén eigenmodes (BAEs), excited by large magnetic islands (m-BAE) and by energetic electrons (e-BAE), are observed. The frequency of the beta-induced Alfvén acoustic eigenmode (BAAE) identified in experiment is in agreement with theoretical prediction. The results for the study of fueling efficiency and penetration characteristics of supersonic molecular beam injection (SMBI) are described.