RECENT TRANSPORT EXPERIMENTS IN W7-AS ON THE STELLARATOR-TOKAMAK COMPARISON

Parameter scans in density, heating power and isotope mass have been c arried out in W7-AS. ECRH at a frequency of 140 GHz has allowed to stu dy the density scaling of the energy confinement time of ECRH plasmas up to densities of 10(20) m(-3). In power scans it has been tried to r elate the power degradation of the energy confinement to a local plasm a parameter. Transport analyses using power balance an heat wave techn iques indicate that the transport coefficient does not depend on the e lectron temperature or related parameters. This observation can be rec onciled with power degradation if the transport coefficient is formall y allowed to vary with changes in the heating power on a faster than t he diffusive time scale. Such a transport process describes also the o bservations in the dynamic phases following large changes in the heati ng power.