Speaker
Description
Toroidal magnetic confinement fusion experiments require a rotational transform
to achieve adequate confinement. This rotational transform can be achieved
via any combination of internal plasma currents, torsion of the magnetic axis,
and the toroidal rotation of the plasma cross section. Internal currents can lead
to current-driven instabilities, and therefore the first stellarators employed magnetic
axis torsion in a figure-8 form to provide their rotational transform [1].
These early configurations were unstable, however, and the figure-8 stellarator
was abandoned in favor of the toroidally-shaped tokamaks and classical stellarators.
As a result, nearly every simulation and analysis framework for magnetic
fusion experiments has been written assuming a toroidal geometry. Recently,
however, advancements in near-axis theory [2] and equilibrium reconstruction
codes [3] have renewed the interest in configurations unrealizable by traditional
simulation and analysis frameworks [4].
Here we demonstrate the capability of the BSTING project [5, 6] to simulate
global fluid transport and turbulence a generalized frame. We utilize a hot-ion
turbulence model within the Hermes-3 family of multifluid models [7], which provides
an inherent flexibility of model fidelity. As a proof-of-principle, transport
characteristics of an optimized quasi-isodynamic figure-8 stellarator [4] are presented.
It is determined that the figure-8 indicates strong ballooning transport
in high-curvature regions, with radial heat and particle flux bands extending
into zero-curvature regions. A comparison of the turbulent flux with known
turbulence scalings, as well as how the flux compares to that in conventional
stellarator geometries is provided.