STOCHASTIC STABILITY OF A TOKAMAK WITH ARBITRARY CROSS-SECTION
The destruction of magnetic surfaces of a plasma torus has often been considered as the main mechanism of anomalous energy loss in a fusion machine; indeed the observed MHD activity of a Tokamak indicates that some of the magnetic flux surfaces which can be calculated from static equilibrium codes are not real. However, stable parts of the plasma torus may still confine the unstable inner part, so it is important to know the stability property of the entire cross section of an ideal static equilibrium in order to judge its resistance against perturbations. The degree of resistance can be expressed by a set of critical magnetic fluctuations which would just destroy a given set of flux surfaces, similar to KAM surfaces in Hamiltonian mechanics. In earlier work, the theoretical basis has not been sufficiently developed for such a calculation: The flux surfaces have been defined by r = const. - which is true only near the magnetic axis r = O - and toroidal effects are not easily included though it is known that they play an important role. Recently the theoretical framework has been enlarged by considering a non - Hamiltonian description of magnetic field line flow, but also a Hamiltonian description is possible and will be considered here. The resulting formula for critical fluctuations will be applied to equilibrium curves of JET; a preliminary figure is shown here.
Bibliographic Reference: COURSE AND WORKSHOP ON BASIC PHYSICAL PROCESSES OF TOROIDAL FUSION PLASMAS, VARENNA (ITALY), AUG. 26-SEPT. 3, 1985 VOL. I, PP. 383-388 EUR 10418 EN (1986) FS, VOL. I AND VOL. II, 733 P., BFR 3600 FOR BOTH VOLUMES, EUROFFICE, LUXEMBOURG, POB 1003
Record Number: 1989125078300 / Last updated on: 1987-12-01
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