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Abstract

It is shown that the oscillations, observed numerically, in the growth rates of ballooning modes in a low-magnetic-shear tokamak can be understood qualitatively as partly due to interference between different WKB branches of the modes and partly due to movement of rational surfaces through the unstable region. This is described quantitatively by an equation formally similar to the Schroedinger equation with a periodic potential, derived using a new reciprocal space ballooning representation. The new ballooning representation needs no assumption about the largeness of "it n/", though the Schr"odinger equation itself is derived by treating "it n/" formally as large. The Schr"odinger equation provides a unified formalism for treating all regimes of magnetic shear, including the case of very weak shear.

Additional information

Authors: DEWAR R L CENTRE DE RECHERECHES EN PHYSIQUE DES PLASMAS, ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE, CH, CENTRE DE RECHERECHES EN PHYSIQUE DES PLASMAS, ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE, CH
Bibliographic Reference: WORKSHOP ON THEORY OF FUSION PLASMAS, VARENNA/I, AUG. 24-28, 1987, PUBL. 1987, BY: SOCIETA ITALIANA DI FISICA
Record Number: 1989126085000 / Last updated on: 1989-05-01
Category: PUBLICATION
Available languages: en