EXPERIMENTS ON LI-PELLET INJECTION INTO HELIOTRON-E

Li pellets of large size were injected into electron cyclotron resonan ce (ECR) heated plasmas and neutral beam injection (NBI) heated plasma s of Heliotron E. The discharge behaviour, pellet ablation and wall co nditioning were studied. The electron pressure is doubled after inject ion into the NBI plasma and remains unchanged in the case of ECR heati ng. This may be due to the energy exchange between the electrons and t hermal ions with the fast ions from the neutral beam. The observed dis crepancy between the experimental and modelled ablation rates may be c aused by both the plasma cooling due to pellet ablatant and the ablati on stimulated by the fast ions in the NBI-heated regime and by the fas t electrons in the ECR-heated regime. In preliminary experiments on wa ll conditioning by Li pellet injection, no improvement of plasma perfo rmance after Li pellet injection was observed in the divertor or limit er configuration, with the limiter radii r(L) = 24-25 cm.