Fusion Nuclear Science Facility Design Points

A Fusion Nuclear Science Facility (FNSF) is needed to fill the gaps between ITER and current experiments and a fusion demonstration power plant (DEMO). Characteristics should be neutron flux at the outboard midplane of 1-2 MW/m$^2$, continuous operation for periods up to two weeks, a goal of a duty factor of 0.3 on a year and fluences of 3-6 MW-yr/m$^2$ in ten years of operation to enable development of blankets suitable for tritium, electricity, and hydrogen production. Systems code analysis that implements constant physics and technology assumptions over a wide range of aspect ratio has been updated for more detailed design considerations and neutronics calculations. Conventional copper-coil tokamaks with inboard breeding/shielding and an OH solenoid optimize at high aspect ratio with devices between DIII-D and JET in size. Removal of the inboard breeding/shielding and OH coil results in the distinct ST branch with devices about half the size and $A < 1.8$. All these devices are generally $Q < 5$ but possible avenues to higher $Q$ will be discussed.