We describe a workflow that is able to approximate basic machine parameters (including but not limited to plasma current IP, major radius R0, toroidal magnetic field B0, fusion power Pfusion) based on the choice of maximum field BTF,max on the in-board leg of the toroidal field (TF) coil of a spherical tokamak (ST) fusion power plant (FPP), its aspect ratio A, the distance between the in-board TF leg and the plasma edge and a limited set of plasma physics parameters typical for an ST FPP. Together with an estimation of the electrical power exported as a function of the fusion gain Q, this allows the mapping of the parameter space where such power plants can be compact while still being commercially viable.
