Work

An asymptotic Grad–Shafranov equation for quasisymmetric stellarators

Year: 2024

Type: article

Abstract: A first-order model is derived for quasisymmetric stellarators where the vacuum field due to coils is dominant, but plasma-current-induced terms are not negligible and can contribute to magnetic differential equations, with $\beta$ of the order of the ratio induced to vacuum fields. Under these assumptions, it is proven that the aspect ratio must be large and a simple expression can be obtained for the lowest-order vacuum field. The first-order correction, which involves both vacuum and current-driven fields, is governed by a Grad–Shafranov equation and the requirement that flux surfaces exist. These two equations are not always consistent, and so this model is generally overconstrained, but special solutions exist that satisfy both equations simultaneously. One family of such solutions is the set of first-order near-axis solutions. Thus, the first-order near-axis model is a subset of the model presented here. Several other solutions outside the scope of the near-axis model are also found. A case study comparing one such solution to a VMEC-generated solution shows good agreement.

Source: Journal of Plasma Physics

DOI: 10.1017/s0022377824000916

Authors: Nikita Nikulsin, Wrick Sengupta, Rogerio Jorge, Amitava Bhattacharjee

Institutions: Princeton University, University of Wisconsin–Madison

Language: English

Topic: Magnetic confinement fusion research

Subfield: Nuclear and High Energy Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,450

Funders: U.S. Department of Energy, Simons Foundation, Simons Foundation Autism Research Initiative