Fast dynamics of type I ELM and transport of ELM pulse in JT-60U

Simultaneous fast ELM measurements using reflectometer, interferometers, Dα intensity and magnetic probe reveal the detailed characteristics of type I ELMs. From the phase signal of the reflectometer indicating the radial movement of the cut-off layer, four different phases in an ELM event and radial extent of the collapse of density pedestal up to twice the pedestal width were observed. Detailed edge density measurements at high-and low-field side consistently demonstrate the asymmetry of collapse of density pedestal due to type I ELM, which is localized at the low-field side (LFS) midplane. Expelled particles from LFS midplane were measured by using LFS midplane and X-point Mach probes together with IRTV. Time delay of the enhanced ion saturation current between the two probes, and time constant of the peak heat load and the enhancement of the plasma flow toward divertor target suggest that the convective plasma flow provides large contribution to the ELM heat load. (author)