Physics and systems design analyses for spherical torus (ST) based VNS

Physics and systems design analyses are carried out to estimate the desired fusion core parameters for an ST based Volume Neutron Source (ST-VNS) that utilizes a single-turn toroidal field coil (TFC). A design with a major radius R₀=1.07 m is estimated to have large margins in physics, technology, and engineering for the initial operation at moderate performance (neutron wall load, W_λ =0.5-2.0 MW/m²). The VNS therefore begins with technologies already assumed in the ITER EDA, and the relatively conservative physics to be tested initially by the ST proof-of-principle experiments presently being built. Given continued advances in technology via the VNS and in physics via the ST experiments, the design should permit upgrades to test components and operation at the level of future Pilot Plant and Power Plants (W_L=5 MW/m²). This approach to VNS places premium on modular components and remote maintenance, encourages continued innovation and optimization in ST fusion and plasma science, and enhances the practicality of the ST pathway to fusion power