Observation of the ELM activity in the far SOL region of KSTAR tokamak plamsa using probe diagnostics

摘要

Edge characteristics of a tokamak plasma are of interest due to their importance in ITER (international thermonuclear experimental reactor). Especially, the particle flux and temperature after the ELM (edge localized mode) crash are of interest. In 2011 KSTAR campaign, plasma parameters such as the ion flux and electron temperature were measured at the far scrape-off layer (far-SOL) of tokamak plasma by using electrical probe diagnostics. The distance between SOL and the position of the probe was ∼40cm. The ion flux and electron temperature were similar with those of core mm interferometer and the edge ECE diagnostic results. The results show good correlation with edge H-alpha signals measured by a filterscope which represent characteristic behavior of the edge plasma such as ELM. Note that the measurement location of H-alpha signals is placed different from the position of the electrical probe. In order to see the exact correlation, a photo diode with an H-alpha filter is installed inside the probe in 2012 KSTAR campaign. As a result, correlations between electrical and H-alpha signals are measured at the same poloidal and toroidal position. The far-SOL characteristics such as the ion flux and electron temperature were calculated from electrical signals. This paper reports the experimental findings on the edge plasma characteristics during ELMs which could give a clue for the far-SOL particle transport.