Regular and Stochastic Orbits of Ions in a Highly Prolate Field-reversed Configuration

Landsman, A.S. ; Cohen, S.A. ; Glasser, A.H.

Princeton University. Plasma Physics Laboratory.

关键词: Hamiltonian;    Breakdown;    70 Plasma Physics And Fusion Technology;    Elongation;    Field-Reversed Theta Pinch Devices;   

DOI  :  10.2172/820104
RP-ID  :  PPPL-3882
RP-ID  :  AC02-76CH03073
RP-ID  :  820104

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来源: UNT Digital Library

【 摘 要 】

Ion dynamics in a field-reversed configuration (FRC) are explored for a highly elongated device, with emphasis placed on ions having positive canonical angular momentum. Due to angular invariance, the equations of motion are that of a two degree of freedom system with spatial variables rho and xi. As a result of separation of time scales of motion, caused by large elongation, there is a conserved adiabatic invariant, J(sub)rho, which breaks down during the crossing of the phase-space separatrix. For integrable motion, which conserves J(sub)rho, an approximate one-dimensional effective potential was obtained by averaging over the fast radial motion. This averaged potential has the shape of either a double or single symmetric well centered about xi = 0. The condition for the approach to the separatrix and therefore the breakdown of the adiabatic invariance of J(sub)rho is derived and studied under variation of J(sub)rho and conserved angular momentum, pi(sub)phi. Since repeated violation of J(sub)rho results in chaotic motion, this condition can be used to predict whether an ion (or distribution of ions) with given initial conditions will undergo chaotic motion.