Edge localised asymmetric radiative phenomena in RFX

Measurements performed with a high resolution tomography system have shown that the total radiation patterns in the RFX plasmas are characterised by remarkable structures, localised in the edge and asymmetric, both in the toroidal and in the poloidal directions. The main source of symmetry breaking in the toroidal direction is mode locking i.e. unstable MHD modes lock in phase and to the wall during the setting-up of the magnetic configuration and produce a toroidally localised macroscopic distortion of the plasma surface with enhanced plasma wall interaction. In this paper the toroidal and poloidal structure of the stationary emissivity profiles in the locked mode region will be presented and its correlation with the local position and shape of the magnetic perturbation will be highlighted, thus giving a more complete picture of the locked mode structure in particular at the plasma edge. (C) 1999 Elsevier Science B.V. All rights reserved.