Optimized Stellarators for Fusion Pilot Plants

Aaron Bader, University of Wisconsin-Madison

Stellarators offer an inherently steady state reactor concept with low recirculating power. Because stellarators do not rely on plasma current for confinement, they are not susceptible to current driven disruptions. Stellarators are also capable of operating at high density, and can perform stably beyond ideal MHD stability limits. Because stellarator configurations have magnetic fields imposed mainly by external coils, there is significant freedom to tailor the confinement properties to the device needs. Only in the last few decades has theoretical knowledge of stellarator confinement advanced so as to produce optimized configurations. This talk will focus on how these devices are optimized, both for the current optimized experiments that exist today, and for future experiments, pilot plants, and reactor concepts.  Six topical areas, identified as key physics gaps for stellarators, are discussed: turbulent transport optimization by design, energetic particle transport, divertor performance, impurity transport, MHD stability, and coil design. The talk will conclude with a perspective for a stellarator pilot plant in both a high-risk short-term scenario and a lower-risk, longer-term scenario.