Theory of tokamak disruptions

Theoretical guidance is needed on two disruption questions: (1) When is a tokamak operating in a metastable state in which loss of control is credible (avoidance question)? (2) What is the worst credible level of destructive effects when plasma control lost and how can these effects be mitigated (effects question)? The success of ITER and the future of tokamaks as fusion systems depend on the precision with which these questions can be answered. Existing capabilities are far from those desired. Nevertheless, one can give physical constraints on the answers and scientific issues that must be addressed to provide reliable guidance. A theoretical program of moderate scale interacting with ongoing experiments could greatly advance the state of development of appropriate tools for simulating, avoiding, and mitigating disruptions.