Stochastic and a posteriori optimization to mitigate coil manufacturing errors in stellarator design. (1st October 2022)

• Record Type: Journal Article
• Authors: Wechsung, Florian; Giuliani, Andrew; Landreman, Matt; Cerfon, Antoine; Stadler, Georg
• Is Part Of: Plasma physics and controlled fusion. Volume 64:Number 10(2022)
• Publication Date: 2022-10-01
• Subjects: stellarator -- coil design -- stochastic optimization -- manufacturing errors; Plasma (Ionized gases) -- Periodicals; Controlled fusion -- Periodicals; 530.44
• DOI: 10.1088/1361-6587/ac89ee
• Languages: English
• ISSNs: 0741-3335

Abstract

Abstract: It was recently shown in Wechsung et al (2022 Proc. Natl Acad. Sci. USA 119 e2202084119) that there exist electromagnetic coils that generate magnetic fields, which are excellent approximations to quasi-symmetric fields and have very good particle confinement properties. Using a Gaussian process-based model for coil perturbations, we investigate the impact of manufacturing errors on the performance of these coils. We show that even fairly small errors result in noticeable performance degradation. While stochastic optimization yields minor improvements, it is not possible to mitigate these errors significantly. As an alternative to stochastic optimization, we then formulate a new optimization problem for computing optimal adjustments of the coil positions and currents without changing the shapes of the coil. These a-posteriori adjustments are able to reduce the impact of coil errors by an order of magnitude, providing a new perspective for dealing with manufacturing tolerances in stellarator design.