Effect of RF heating on edge parameters in the TCA tokamak

Detailed scrape-off measurements during Alfvén wave heating experiments (PRF ~ 200 kW) in TCA are presented. The Measurements are performed by means of electrical probes and by deposition probes fixed onto the antennae. It is shown that different antenna designs strongly influence the behaviour of the boundary plasma. Even during low power RF heating experiments is it found that the plasma-antenna interaction leads to a non-Maxwellian plasma. Low frequency density fluctuations are associated with changes of the density and temperature profiles during RF. High frequency fluctuations at the driving frequency and their harmonics are observed.