Startup scenario development for SPARC

Time-dependent vacuum field calculations for the breakdown and burnthrough phase of a SPARC discharge have been completed to support design and procurement plans. Strong toroidal electric field required for robust breakdown and burnthrough (> 1 V/m) is achieved by commutating external resistance into the superconducting solenoid circuit for about 100ms. Scenarios utilizing only the superconducting magnet sets are found that produce the necessary field null quality and passive radial and vertical stability. Including the copper divertor coils in the scenario offers an avenue for achieving the required topology with faster Ip ramp rates. Constraints on the poloidal field null quality is more relaxed than similarly sized machines due to SPARC's increased toroidal field strength, such that the connection length criterion for breakdown is reasonably satisfied. The SPARC plasma initiation scenarios are qualified against existing tokamak databases and reduced models. This framework is used to design startup scenarios for a variety of operational constraints and goals.