Scape-off-layer and divertor modelling is being employed to study a wide range of SPARC operations, including early SPARC campaigns, SPARC advanced divertor experiments, and divertor power asymmetries and drift effects in SPARC. A variety of divertor topologies are being explored that SPARC can test, from a standard divertor, X-divertors, and the X-point target divertor currently conceptualised for ARC. Gas and impurity radiator injection consistent with SPARC’s hardware design are utilised to find dissipate divertor regimes, to characterise experiments within PFC material limits to meet SPARC’s milestones and that can inform an ARC-class divertor design.
The divertor is a key component of a tokamak fusion device, in terms of handling both particle and power exhaust. The divertor targets – specifically armoured plates where the plasma makes contact with the vessel components – need to have heat fluxes/temperatures kept below key material limits to avoid damage from erosion/melting (and subsequent core contamination). Failure of the divertor components can potentially lead to costly delays/repairs, or even failure of the device as a whole. However, the divertor power exhaust problem remains unsolved in the fusion community, and viable solutions need to be identified for future reactors to be a success. Advanced magnetic divertor configurations are studied as advantageous potential solutions, including double-nulls, long-legs and magnetic field flaring with secondary divertor X-points. SPARC will serve to test a variety of physics and technology requirements necessary for the follow-on ARC reactor, including a dedicated Advanced Divertor Mission, where it can test a variety of configurations in ARC-relevant conditions. Due to the high-field and compact nature of SPARC, divertor and PFC power loading will be a significant challenge for its experiments – therefore, power exhaust mitigation strategies need to be studied and understood ahead of SPARC operations.
Large-scale edge plasma simulation codes such as SOLPS-ITER and SOLEDGE2D are utilized for this work.
