Adjoint methods for quasi-symmetry of vacuum fields on a surface. (21st February 2022)

• Record Type: Journal Article
• Authors: Nies, Richard; Paul, Elizabeth J.; Hudson, Stuart R.; Bhattacharjee, Amitava
• Is Part Of: Journal of plasma physics. Volume 88:Number 1(2022)
• Publication Date: 2022-02-21
• Subjects: fusion plasma -- plasma devices -- plasma confinement; Plasma (Ionized gases) -- Periodicals; 530.4405
• DOI: 10.1017/S0022377821001264
• Languages: English
• ISSNs: 0022-3778

Abstract

Abstract : Adjoint methods can speed up stellarator optimisation by providing gradient information more efficiently compared with finite-difference evaluations. Adjoint methods are herein applied to vacuum magnetic fields, with objective functions targeting quasi-symmetry and a rotational transform value on a surface. To measure quasi-symmetry, a novel way of evaluating approximate flux coordinates on a single flux surface without the assumption of a neighbourhood of flux surfaces is proposed. The shape gradients obtained from the adjoint formalism are evaluated numerically and verified against finite-difference evaluations.