Investigation of statistical characterization of radial turbulence in the edge of HuanLiuqi-2A plasma with visible spectroscopy diagnostic.

The radial motion and structure of edge turbulence in the HuanLiuqi-2A tokamak [Y. Liu et al., Nucl. Fusion 45, S239 (2005)] was measured with visible spectroscopy diagnostic system; the radial turbulence propagation velocity and correlation length were evaluated by time-delay correlation technique and there were typically V_r=0.4-1 km/s and L_r=2-6 cm, respectively. The edge intermittent events accompanied with turbulence have been observed in plasma edge and propagated outward radially; especially through the scrape-off layer, the fluctuation signals of D_α exhibit strong asymmetric probability distribution functions (PDFs). Their propagation trajectories and radial velocity PDFs were inferred from a special correlation technique and the results indicated the radial velocity of intermittent event depends on its amplitude. Some comparisons with previous measurements and models were also presented. [ABSTRACT FROM AUTHOR]