PARTICLE TRANSPORT STUDY OF ELECTRON CYCLOTRON HEATED PLASMAS IN HELIOTRON E

摘要

The particle transport in ECRH plasmas is investigated with edge fluctuation measurements. Both electrostatic and electromagnetic fluctuations are well correlated with the global particle confinement, <τ_p>, (∝ nl/H_α). It is found that the radial electric field increases positively just inside the last closed flux surface (LCFS) during the particle confinement degradation phase. A poloidally asymmetric potential distribution and E_θ are also observed near the LCFS, which is considered to be caused by the spatially asymmetric loss cone structure and the loss of ECRH generated energetic electrons. Pellet ablation, energy diffusion and pitch angle scattering of injected beam ions, and the rotation of MHD modes are studied to evaluate the density, energy and loss of suprathermal electrons. A transition to improved particle confinement has recently been observed for a combined edge/central heating scenario. The effects of trapped electron loss on particle confinement improvement are discussed.