SPARC Divertor Mission, Physics and Engineering Basis

A subset of the physics and engineering basis for the plasma facing components (PFCs) in the SPARC tokamak are presented.  Designs are shown that support weakly dissipative commissioning scenarios, moderately dissipative, P_RAD,DIV/P_SOL ~ 0.5, high power, P_α+P_ext = 41 MW, Q_fus > 2 plasmas, and a range of highly dissipative configurations that can be used to accomplish SPARC’s advanced divertor mission.  Metrics for selection of plasma facing material are summarized, describing SPARC’s decision to operate with all tungsten-based PFCs.  Heat load specifications for quasi steady-state heat flux, ELMs and disruptions are presented, along with relevant results of high heat flux tungsten exposure tests and finite-element simulations of tile concepts.  Disruption electromagnetic load specifications for tiles are also discussed.  The goals of the SPARC advanced divertor mission are summarized, which take the form of seven open questions necessary to answer to inform ARC design.  The diagnostics that support this mission are highlighted, emphasizing minimum viable requirements.  SOLPS-ITER simulations of fully-detached, Ne-seeded SPARC plasmas are used to help scope the dynamic ranges needed for diagnostic design.