Determination of magnetic forces in tokamaks during axisymmetric plasma disruptions

Methods are developed to infer estimates of plasma parameters from measurements of the dynamic response (e.g. displacements and support forces at critical locations) of the structure of a tokamak undergoing plasma disruptions. Simplified lumped-parameter models, based upon dynamic finite element (FE) calculations, are used to describe the mechanical response of the structure of the JET tokamak to transient forces generated during axisymmetric disruptions. These are then used in dynamic simulations, driven by parametrically-represented magnetic forces, where parameters include amplitude, duration and point of application. Estimates for these parameters are then obtained by finding values, which give the best fit, in a statistical sense, between the model's predictions of dynamic response to the measured response of the structure. These methods can then be used to help guide mechanical design of new machines so that structural loadings remain tolerable throughout the operational envelope.