Zero-current high-beta stellarator equilibria with rotational transform profile control

Abstract
Zero-current high-beta equilibria for a stellarator device are calculated using the averaging method. It is found that, by shaping the vertical field, the rotational transform can be controlled in an approximate way as beta is increased. At the same time, the Pfirsch-Schlüter currents are reduced – with no modification of the magnetic well. This permits access to the high-beta regime with more favourable rotational transform profiles. Results are presented for the Advanced Toroidal Facility (ATF) device.