Effects of auxiliary heating on dc electric fields in the TEXTOR boundary

Abstract The generation of d.c. electric fields in the TEXTOR edge (inside the last closed flux surface) and scrape-off layer (SOL) during auxiliary heating has been studied using electric probes and spectroscopy. Peak radial and poloidal electric fields in the edge during neutral injection are 5 kV/m and 3 kV/m respectively while little effect is seen in the SOL. ICRH alters the radial electric field in the edge, and generates large (8 kV/m) fields in the SOL. These modifications depend sensitively on the limiter-antenna configuration. Large poloidal electric fields of 2 kV/m are also generated in the SOL, but nearly vanish in the edge. Spectroscopic measurements of changes in poloidal rotation in the edge are in agreement with the probe measurements in neutral beam heated discharges. Profile modifications due to the electric fields are observed. The radial particle velocities corresponding to the measured poloidal electric fields exceed by many times the diffusive velocity, particularly during ICRH, suggesting that convective flows may be important.