Non-linear behaviour in tokamaks

From the many non-linear processes occurring in tokamaks we have chosen three quite different phenomena. Firstly, the problem of fast instabilities which is quite subtle and requires some new thinking. Secondly disruptions, which are found to be rather complex. Although explanations have been provided for some of the features, the initial energy quench does not appear to be consistent with existing theoretical models. Finally, an analysis of the Kadomtsev reconnection model leads to doubts about the applicability of the resistive Ohm's law and suggests that the effect of electron inertia would be predominant. (author)