Fusion Science and Technology / Volume 51 / Number 2T / February 2007 / Pages 82-85
Technical Paper / Open Magnetic Systems for Plasma Confinement
Behavior of edge plasma and neutral particles are described based on visible measurement by using high-speed camera performed in the GAMMA 10 tandem mirror for the first time. In the central-cell midplane of GAMMA 10, two high-speed cameras (Ultima-SE, Photron Inc. and MEMRECAM fx-K4, NAC Inc.) were mounted and detailed time behavior of visible light emission from the plasma was investigated. In the standard plasma discharges heated by ion cyclotron range of frequency (ICRF) wave, a short gas puffing of hydrogen (3 ms) close to the central-cell midplane was carried out to illuminate the plasma periphery and the time evolution of visible light emission from the gas cloud was captured precisely. The time behavior of the emission cloud localized near the gas puff port was found to be similar to that of H line intensity measured nearby. The light emission on the central-cell limiter accompanied by central electron cyclotron heating (c-ECH) showed a rotation in the direction of the electron diamagnetic drift. the light emission also indicates another rotation mechanism, such as ExB drift at a plasma collapse. Fully three-dimensional neutral transport simulation using a Monte-Carlo code DEGAS is applied to gas puff imaging experiment and the simulation results qualitatively explained the experimental result.