Conceptual magnet design study for fusion nuclear science facility

The Fusion Nuclear Science Facility (FNSF) is a nuclear confinement device to provide the integrated fusion environment with fusion reactor components. The FNSF is the stepping stone to bridge the technical gaps of burning plasma and nuclear science between the International Thermal Nuclear Experimental Reactor (ITER), currently under construction in the south of France, and the demonstration power plant (DEMO). For the next-step fusion reactors, resistive copper magnet cannot be a sustainable solution due to large power consumption in coils of large size needed. Both Low temperature superconductor (LTS) and high temperature superconductor (HTS) are considered for the FNSF magnet design based on the state-of-the-art fusion superconducting magnet technology. Input parameters to FNSF magnet design include magnetic field of 7.5 T at plasma center with a major radius of 4.8 m and minor radius of 1.2 m, and a peak field of over 16 T on the TF coils. The high magnetic field can be achieved by using the high performance ternary Restack Rod Process (RRP) Nb₃Sn strands for toroidal field (TF) magnets and a high aspect ratio rectangular cable-in-conduit conductor (CICC) design. The conductor design concept and TF coil winding pack composition and dimension are discussed based on the horizontal maintenance scheme. Neutron radiation limits for the LTS and HTS conductors and electrical insulation materials are reviewed based on the available materials previously tested. The material radiation limits for FNSF magnets are defined as part of the conceptual design studies. The global structural analysis of FNSF magnets based on the radial build was performed to validate feasibility for the plant layout toward horizontal maintenance and global structural integrity of its magnet system.