Gradient-based optimization of 3D MHD equilibria

Abstract

Using recently developed adjoint methods for computing the shape derivatives of functions that depend on MHD equilibria (Antonsen et al. 2019; Paul et al. 2020), we present the first example of analytic gradient-based optimization of fixed-boundary stellarator equilibria. We take advantage of gradient information to optimize figures of merit of relevance for stellarator design, including the rotational transform, magnetic well, and quasisymmetry near the axis. With the application of the adjoint method, we reduce the number of equilibrium evaluations by the dimension of the optimization space ($\sim 50-500$) in comparison with a finite-difference gradient-based method. We discuss regularization objectives of relevance for fixed-boundary optimization, including a novel method that prevents self-intersection of the plasma boundary. We present several optimized equilibria, including a vacuum field with very low magnetic shear throughout the volume.

References in corpus (4)

• Necessary and Sufficient Conditions for Quasisymmetry
• Figures of merit for stellarators near the magnetic axis
• Adjoint approach to calculating shape gradients for three-dimensional magnetic confinement equilibria. Part II: Applications
• Computing the shape gradient of stellarator coil complexity with respect to the plasma boundary

Cited by in corpus (1)

• Computing the shape gradient of stellarator coil complexity with respect to the plasma boundary