Toroidal Precession as a Geometric Phase
Authors: J.W. Burby and H. Qin
Abstract:
Toroidal precession is commonly understood as the orbit-averaged toroidal drift of
guiding centers in axisymmetric and quasisymmetric configurations. We give a new,
more natural description of precession as a geometric phase effect. In particular, we
show that the precession angle arises as the holonomy of a guiding center's poloidal
trajectory relative to a principal connection. The fact that this description is physically
appropriate is borne out with new, manifestly coordinate-independent expressions
for the precession angle that apply to all types of orbits in tokamaks and
quasisymmetric stellarators alike. We then describe how these expressions may be
fruitfully employed in numerical calculations of precession.
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Submitted to: Physics of Plasmas (September 2012)
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Download PPPL-4818 (pdf 732 KB 17 pp)
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