A movable graphite limiter with an internal heater has been installed in the heliotron/torsatron type compact helical system (CHS). Comparing discharges with and without the limiter the origin of major impurities and the role of the limiter are discussed. Infrared TV measurements reveal that there are two hot spots on the limiter due to heat loading and their temperatures depend on the electron density and/or the magnetic field direction. Limiter temperature dependence of measured CH/Hγ, CI, CII, OII, CH+3, OV and total radiation loss is compared. From these experiments it is concluded that CH4 molecules produced chemically on the limiter are presumed to recycle rapidly near the limiter and both carbon and oxygen impurities result probably from CO produced chemically on the limiter with oxygen which is predominant in CHS and originates mostly from the first wall. At surface temperatures above 900 ° C the limiter effect on impurities is observable in the main plasma.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- Materials Science(all)
- Nuclear Energy and Engineering