Study of plasma disruptions in JET and its implications on engineering requirements

The authors discuss the problems associated with the decay of the plasma current in JET (Joint European Torus) disruptions. It is noted that the slow mode of plasma current decay may offer the best chances of minimizing the forces in high current disruptions. However, the plasma position needs to be controlled during the decay of the plasma current. The radial field position can be controlled by a sufficiently fast vertical field amplifier. For the control of the vertical position the two problems to be solved are the magnetohydrodynamic perturbations of the magnetic signals and the increased vertical destabilization, which coincides in time with the measured energy quench. It has been demonstrated that a substantial reduction of the vessel forces can be achieved by reducing plasma elongation prior to the disruption