Neoclassical Drift of Circulating Orbits Due toToroidal Electric Field in Tokamaks
Authors: Hong, Qin, Xiaoyin Guan and Nathaniel J. Fisch
Abstract:
In tokamaks,Ware pinch is a well known neoclassical effect for trapped
particles in response to a toroidal electric field. It is generally believed that
there exists no similar neoclassical effect for circulating particles without collisions.
However, this belief is erroneous, and misses an important effect. We show both
analytically and numerically that under the influence of a toroidal electric field
parallel to the current, the circulating orbits drift outward toward the outer wall
with a characteristic velocity O (ε -1) larger than the E X B velocity, where ε is the
inverse aspect-ratio of a tokamak. During a RF overdrive, the toroidal electric field
is anti-parallel to the current. As a consequence, all charged particles, including
backward runaway electrons, will drift inward towards the inner wall.
__________________________________________________
Submitted to: Nuclear Fusion (May 2011)
__________________________________________________
Download PPPL-4639 (pdf 841 KB 11 pp)
__________________________________________________