전기 탐침을 이용한 KSTAR 경계 플라즈마의 천이거동 연구.

Abstract

Fast Reciprocating probe (FRP) and fixed Electrical probe arrays (EPAs) are used to analyze the edge plasmas during transient plasma discharges in the KSTAR (Korea Superconducting Tokamak Advanced Research) device. EPAs are made of carbon fiber composite with a dome shape structure, and extrude about 1mm from the surface of the background graphite tiles, which are exposed to the strongly magnetized plasma with the incident angle of the particles impinging on the probe angles from zero to nine degrees. They are installed in the limiter and divertor area of the KSTAR device, with a bias voltage of -315V in order to measure the ion saturation currents. The ion saturation currents from the probes could identify the Edge Localized Mode (ELM) phenomena comparing with D_alpha signals. From the distribution of the ion saturation current measured by EPAs during a diverted plasma discharge, it is found that two strike points move vertically upward at the inboard divertor and poloidally up and down at the central divertor, respectively. Radial profiles of plasma parameters such as electron temperature Te, plasma density ne, floating potential Vf and parallel flow velocity v// are measured by using the FRP at the scrape-off-layer (SOL) region in the middle plane of the KSTAR machine. The electron temperature measured by electric probes is compared with those by a Thomson scattering system at the edge region to validate the probe data. Dependence of the e-folding lengths ??ne and ??Te on global parameters such as plasma current, plasma density and toroidal field is investigated from the radial profile measurements during L and H mode discharges. Characteristics of ELM during H-mode discharge are investigated from both the FRP and EPA measurements.