Aspects of plasma-wall interaction in the ASDEX divertor experiment

ASDEX (Axially SymmetriC Divertor Experiment) is a large tokamak now under construction at IPP Garching. The main parameters are: major radius 1.65 m, plasma radius 0.4 m, toroidal field on axis 2.8 T and plasma current 500 kA. The experiment is scheduled to go into operation in about two years. The first aim of the experiment is to test the divertor action, i.e. plasma stability without material limiter and reduction of impurity influx. Since the divertor will essentially be of the unload-type, the latter problem should be solved by reducing wall bombardment. On the premises of sufficient stability the plasma-wall interaction will occur on the divertor slits, in the main divertor chamber and (with refuelling) on the wall owing to charge exchange neutrals. Plans for surface studies are being discussed.