Plans for managing accidental reattachment PFC heat loads in SPARC

High performance pulses in SPARC will nominally run in a detached plasma state, where the heat and particle fluxes to the Plasma Facing Components (PFCs) are reduced sufficiently to keep the machine within its operational limits. However, in some cases a high degree of detachment may be difficult to maintain and the plasma may transiently reattach to the divertor targets. These transient attached scenarios will require diagnostics to quickly identify the reattachment event and for the Plasma Control System (PCS) to return the plasma to an actively stable detached configuration before the PFCs exceed their allowable engineering limits. If this cannot be achieved, then the PCS should end the pulse.

This work will provide an overview of the planned detection and mitigation operational strategies for reattachment events in SPARC. Predictions of the reattachment timescales will be compared with estimates for various actuator responses such as impurity seeding or strike point sweeping. HEAT predictions of the time varying heat loads (stress, temperature, tungsten recrystallization) for the 3D PFC geometry during the reattachment event will be presented. It will be shown that the SPARC PCS can respond fast enough to keep the PFCs within their allowable operational budgets.