An indirect method of obtaining a map of magnetic surfaces (and, in particular, of the q = 1 magnetic island) during sawtooth activity in tokamaks is proposed. It is applied to sawteeth observed in the TFR tokamak. The results seem to be in contradiction with the usual explanation of the internal disruption as due to the invasion of the whole interior of the discharge by a very large q = 1 island, but are compatible with a proposal made by Samain and Dubois, in which the disruption happens while the island width is still small compared to the radius of the q = 1 surface.
An investigation of coupling of the internal kink mode to error field correction coils in tokamaks