QPS Transport Physics Flexibility Using Variable Coil Currents

An important goal for a stellarator design is to incorporate enough flexibility to experimentally test a range of physics issues. The proposed Quasi-Poloidal Stellarator device achieves this by allowing independently variable currents in the modular, vertical field, and toroidal coil sets. Numerical optimizations and modeling show that this can allow significant tests of neoclassical cross-field transport rates, reduced poloidal flow damping (relative to the tokamak), and magnetic island width control. This flexibility is achieved in a unique, very low aspect ratio (R₀/<a> = 2.7) two-field period (racetrack-shaped) configuration that generates rotational transform from a combination of internal plasma currents and external shaping.