Relations among potential change, fluctuation change and transport-barrier in the JFT-2M tokamak

摘要

Potential and density/temperature fluctuations at the L-H transition are measured by the heavy ion beam probe on JFT-2M. It has been observed that the timescale of the potential change is as fast as 10-100 μs when the input power (P_in) is larger than the L-H threshold power (P_th). When P_in~P_th, the confinement is improved gradually step by step with sawtooth crashes. After a few Sawtooth crashes, the potential drops rapidly to the level of the ELM free H mode.