Modeling and Simulation Group Meeting

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Rethinking edge closures in 3D fixed-boundary magnetohydrodynamic equilibrium modeling

Speaker: Alan Kaptanoglu, NYU

Location: Warren Weaver Hall 517

Date: Thursday, April 30, 2026, 12:30 p.m.

Synopsis:

Outside the core of the plasma, the plasma current and pressure rapidly transition to zero in a scrape-off or edge region or plasma-vacuum interface. However, existing tools for fixed-boundary magnetohydrodynamic equilibria in 2D and 3D typically prescribe the computational boundary interior to this transition layer. We argue that: (1) a more realistic and robust assumption is to define the plasma boundary exterior to this transition layer, where J = p = 0, (2) without this boundary change, existing coil optimization routines for 3D toroidal equilibria (stellarators) should be changed to match free-boundary equilibrium requirements, and (3) that fixed-boundary calculations can be implemented to specify the computational boundary as an isobar of pressure rather than a flux surface. These choices are especially consequential for stellarators. We conclude with an implementation of  fixed-boundary MHD equilibrium calculations using magnetic relaxation with an isobar boundary surface.