On the asymptotic equilibrium of a rapidly-rotating Mirror Plasma

Due to the success of the Maryland Centrifugal Experiment (MCX) [R. F. Ellis et. al. PoP 8, 2057

(2000) & PoP 12, 055704 (2005)] and initial theoretical analyses, the Centrifugal Mirror concept is being

further explored by the construction of the Centrifugal Mirror Fusion Experiment (CMFX) [C. Romero-Talamas,

this conference] at the University of Maryland. This prompts a deeper inquiry into the underlying confinement and

stability properties of centrifugal mirrors as a class of devices. Future, reactor-grade, centrifugal plasmas will operate

at high Mach numbers (M ≳ 5), which provides a potential expansion parameter for simplifying their physics.

In this work we present a class of axisymettric magnetic equilibria for these devices, derived in the rapidly-rotating

large-Mach-number limit. The prototypical equilibrium is comprised of a narrow layer of plasma and an exterior

vacuum field. In the layer, the equilbrium is characterised by the balance between centrifugal forces and magnetic

tension. We provide detailed expressions for the structure of the equilibrium in the plasma layer, and explore whether

further nested layers, driven by plasma pressure, can form. These equilibria exhibit many commonalities with equilibria

used for studying astrophysical disks. By exploring the coupling to the exterior vacuum solution we can study the

transition of these equilibria from mirror-like, where all the field lines are open, to FRC-like, where regions of closed

flux appear between the plasma and the symmettry axis. This may provide a hard limit on the rotation speed

achievable in future experiments. These equilibria naturally extend to a sequence of thin disks

spaced along the axial direction. Finally, we examine the stability of these equilibria and explore how more elongated

mirror configurations may naturally collapse into the thin disks presented here.