Electrostatic fluctuation and fluctuation-induced particle flux during formation of the edge transport barrier in the JFT-2M tokamak

Full text: The potential and density fluctuations are measured in the edge region by a Heavy Ion Beam Probe (HIBP) in the JFT-2M tokamak. The particle flux induced by fluctuations is estimated with the HIBP, and seems to dominate the particle transport. It decreases at L-H transition because the potential and density fluctuation are suppressed. In the Ohmic and L-mode plasma, the particle flux shows intermittent behavior. At the same time, the coherent potential fluctuation appears. The frequency of the coherent mode is about 15 kHz and the poloidal mode number is less than or equal 8. On the other hand, no such coherent mode in the density fluctuation is observed. The characters may have a similarity to those of Geodesic Acoustic Mode (GAM) which is a kind of zonal flow. The period of the intermittent particle flux is comparable to that of the coherent mode, so the intermittent behavior of particle flux may relate to the coherent mode. (author)