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arXiv · 2503.04934

Computation of generalised magnetic coordinates asymptotically close to the separatrix

Stuart Benjamin·Nikolas Logan·Christopher Hansen
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Abstract

Integrals to calculate generalised magnetic coordinates from an input magnetic flux function asymptotically close to the separatrix are presented, and implemented in the GPEC/DCON code suite. These integrals allow characterisation of the magnetic equilibrium of a diverted tokamak, in magnetic coordinates, arbitrarily close to the last closed flux surface, avoiding the numerical issues associated with calculating diverging field line integrals near a magnetic x-point. These methods provide an important first step in the development of robust asymptotic equilibrium behaviour for spectral 3D MHD codes at the separatrix.

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Stuart Benjamin, Nikolas Logan, Christopher Hansen. 2025-03-06. Computation of generalised magnetic coordinates asymptotically close to the separatrix. https://arxiv.org/abs/2503.04934

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