Transient behavior of the Ignitor plasma chamber under vertical displacement and halo current event

Abstract

Given the new plasma disruption scenarios that envisage the production of a significant, nonaxisymmetric halo current during the current quench following a typical vertical displacement event (VDE), the structural integrity of the Ignitor plasma chamber (PC) has been verified by means of a dynamic elastic-plastic analysis. Since the analysis is non-linear and the various load components are distributed with different periodicity, the modeling of the entire (360/spl deg/) PC structure has been necessary, and the loads have been applied simultaneously. Thus the Ignitor PC has been demonstrated to be capable of withstanding, according to the ASME III code rules, several thousands of cycles under plasma disruption conditions, involving an average halo current of 3 MA, i.e. 25% of the nominal plasma current, with a toroidal peaking factor of 2. The halo current value has been assumed on the basis of relevant experimental data. The main results of the analysis demonstrate how the elastic-plastic approach could mitigate the structural requirements for the Ignitor PC. In fact, the maximum plastic deformation is below 0.5% and the maximum permanent displacement is below 2 mm.