The time behaviour of impurities in the HL-1 tokamak

During HL-1 Tokamak discharges, the major gaseous impurities from the wall, CH4, CO, CO2, and H2O, were observed with a remote controled quadrupol mass spectrometer of SZ-001 type. The mass spectra has multipeak shape. Each component has a special characteristic time. The partial pressure increases with the increase of plasma current and the decrease of limiter radius. These effects are especially striking with puffing gas. CO released principally during the discharge, and CH4 after the discharge. With continuous gas filling, the time behaviour of the gaseous impurities at the gas filling side of the torus differs from that at the opposite side. After Taylor discharge cleaning of 30000 shorts, there was still a lot of C, O impurities on the SS movable limiter