A single-field-period quasi-isodynamic stellarator

Abstract

A single-field-period quasi-isodynamic stellarator configuration is presented. This configuration, which resembles a twisted strip, is obtained by the method of direct construction, that is, it is found via an expansion in the distance from the magnetic axis. Its discovery, however, relied on an additional step involving numerical optimization, performed within the space of near-axis configurations defined by a set of adjustable magnetic-field parameters. This optimization, completed in 30 seconds on a single cpu core using the SIMSOPT code, yields a solution with excellent confinement, as measured by the conventional figure of merit for neoclassical transport, effective ripple, at a modest aspect ratio of eight. The optimization parameters that led to this configuration are described, its confinement properties are assessed, and a set of magnetic-field coils is found. The resulting transport at low collisionality is much smaller than that of W7-X, and the device needs significantly fewer coils thanks to the reduced number of field periods.

13 pages, 9 figures

References in corpus (6)

• Near-Axis Expansion of Stellarator Equilibrium at Arbitrary Order in the Distance to the Axis
• Direct construction of stellarator-symmetric quasi-isodynamic magnetic configurations
• Figures of merit for stellarators near the magnetic axis
• Optimized quasisymmetric stellarators are consistent with the Garren-Boozer construction
• Proposal of A Linked Mirror Configuration for Magnetic Confinement Experiment
• Stellarator optimization for good magnetic surfaces at the same time as quasisymmetry

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• Constructing the space of quasisymmetric stellarators
• Magnetic Fields with General Omnigenity
• Higher order theory of quasi-isodynamicity near the magnetic axis of stellarators
• MONKES: a fast neoclassical code for the evaluation of monoenergetic transport coefficients
• Electron root optimisation for stellarator reactor designs
• Required toroidal confinement for fusion and omnigeneity
• Near-axis quasi-isodynamic database