The change in the safety factor profile at a sawtooth collapse

Perturbations of the electron density and the poloidal magnetic field induced by sawtooth instabilities are studied using interferometric and polarimetric data. The change in the safety factor profile at a sawtooth collapse is deduced. It is found that sawteeth do not lead to complete reconnection of the poloidal flux since ( Delta q0)collapse<1-q0. A comparison of the rate of change of q0 between sawteeth with field diffusion calculations assuming neo-classical resistivity also suggests that complete reconnection does not take place.