Tokamak disruptions and edge current

The thermal decay phase of a disruption in fusion toroidal development devices is thought to be a large edge radial current. How a disruption occurs, the reason for variations in the severity of the disruption, the justification for the fast decay of energy, the similarities between a disruption and a sawtooth crash, and, most importantly, methods of preventing a disruption or limiting its damage to a tolerable value are explained. The author suggests that the radial current in the edge circuit can produce the large forces observed in the structures, as well as cause the severe arc damages that have been observed. This current in the vessel structure flows at approximately 90° with respect to the toroidal field; thus, the JXB force is high enough to account for previous damage on many tokamaks. It is proposed that disruptions can be easily eliminated or their damage reduced to negligible values. It is also proposed that the control of the edge radial current component will result in many other very important improvements in tokamak operations, including a much improved confinement time