MARGINAL STABILITY EFFECTS AND PRESSURE PROFILE EVOLUTION IN AN EXTRAP Z-PINCH
Non-circular, Z-pinch discharges, generated in Extrap experiments, exhibit stability against global, fluid instabilities. In this paper we describe how marginally stable equilibria might develop in this Extrap configuration. An Extrap Z-pinch is a pinch discharge where the current channel has a characteristic non- circular cross-section achieved by bounding the discharge by a magnetic separatrix produced when a vacuum magnetic field, generated by currents in external conductors, combines with the self-magnetic field produced by the discharge current. The pinch boundary is changed from a free (plasma - vacuum) boundary to an interface between a high-beta pinch plasma and a low-beta plasma contained in the vacuum magnetic field. During the build-up of the discharge, unstable equilibria are initially produced. Fluctuations associated with these instabilities can lead to increased mass transport thus altering th equilibrium. The presence of the warm, low-beta plasma, scrape-off layer, which provides a boundary condition on the pinch, can make it possible for equilibrium profiles to evolve that are marginally stable against global fluid modes.
Bibliographic Reference: WRITE TO THE DEPARTMENT OF PLASMA PHYSICS AND FUSION RESEARCH, ROYAL INSTITUTE OF TECHNOLOGY, S-100 44 STOCKHOLM (SWEDEN), MENTIONING REPORT TRITA-PFU-85-11, 1985
Record Number: 1989124104000 / Last updated on: 1987-01-01
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