Evaluation of Z_eff Profile in Low-Density and High-T_i Discharges with Carbon Pellet Injection based on Space-Resolved EUV Spectroscopy in LHD

Abstract

Z_eff profile analysis has been carried out in a low-density and high-T_i discharge with carbon pellet injection. The evolution of the Z_eff profile shows a centrally peaked profile just after the pellet injection while the profile gradually returns to an original flat profile as a function of time. Comparison between the evolution of Z_eff and T_i profiles in the plasma center strongly suggests that there is a positive relation between Z_eff and T_i.