Combined Langmuir-magnetic probe measurements of type-I ELMy filaments in the EAST tokamak

Detailed investigations on the filamentary structures associated with the type-I edge-localized modes (ELMs) should be helpful for protecting the materials of a plasma-facing wall on a future large device. Related experiments have been carefully conducted in the Experimental Advanced Superconducting Tokamak (EAST) using combined Langmuir-magnetic probes. The experimental results indicate that the radially outward velocity of type-I ELMy filaments can be up to 1.7 km s^-1 in the far scrape-off layer (SOL) region. It is remarkable that the electron temperature of these filaments is detected to be ～50 eV, corresponding to a fraction of 1/6 to the temperature near the pedestal top, while the density (~3 ×10 ¹⁹ m ^-3) of these filaments could be approximate to the line-averaged density. In addition, associated magnetic fluctuations have been clearly observed at the same time, which show good agreement with the density perturbations. A localized current on the order of ～100 kA could be estimated within the filaments.