Advances in the SPARC and ARC projects at Commonwealth Fusion Systems

Commonwealth Fusion Systems and its partners have advanced the construction and assembly of the SPARC tokamak, on track for operations in 2026, and are proceeding with conceptual design of the ARC fusion power plant, aiming for operations in the early 2030s. The SPARC tokamak (B_T = 12.2 T, R₀ = 1.85 m, a = 0.57 m, designed to achieve Q ≈ 11) is under construction in Devens, Massachusetts. CFS has begun building and testing the toroidal field coils, the poloidal field coils, and the central solenoid for SPARC. Major supporting systems such as cryogenics, tritium handling, and ICRH heating are being installed and commissioned and will fully operate for a dry dress rehearsal (DDR) before SPARC operations. The plant and plasma control systems based on the in-house neutrino framework are continually tested against hardware-in-the-loop (HITL) simulations in preparation for operation. Integrated core and edge physics analysis of SPARC has focused on preparation for the first campaign goal of Q > 1 in an ICRH-heated L-mode. In parallel, as a participant in the DOE Milestone Program, CFS has continued to advance the design of the ARC power plant. This work includes physics analysis of performance and stability, as well as advancing R&D and engineering design. This talk presents an overview of progress on both SPARC and ARC.