PARTICLE BALANCE STUDIES IN TEXTOR DURING EXPERIMENTS OF PELLET INJECTION, HELIUM INJECTION, AND ICR-HEATING

Analysis based on the particle conservation law has been carried out t o observe the global fuelling process in tokamak discharges. The respo nse of the net recycling flux from the first wall is investigated in t he tokamak TEXTOR, using calibrated signals of the gas feed rate, the neutral gas pressure in the vessel, the total amount of electrons, and the particle removal rates by the ALT-II belt-pump limiter and by a m ain pump unit. Net absorption (pumping) of hydrogen by the wall is obs erved for almost all tokamak discharges since a new wall conditioning technique called siliconisation is employed. The net absorption or fue lling depending on the discharge condition influenced by injection of pellets, by helium gas injection combined with neutral beam injection, and by rf heating can be interpreted in terms of the particle-induced desorption effect with depth profile taken into consideration.