Community Research and Development Information Service - CORDIS

Abstract

Classical scaling laws are deduced for the equilibrium relations between pinch current J, pinch radius a, axial density n-o and temperature T-o of linear Z-pinches having a finite length L, as well as for toroidal Z-pinches having a large aspect ratio. In both cases the radius a is found to increase almost linearly with the current J at a fixed density n-o, and the temperature T-o to increase with J at fixed values of the radius a. In principle, anomalous transport can be simulated in a first approximation by multiplying the transport coefficients by corresponding numerical factors. At a fixed density n-o and a fixed external conductor current of an Extrap pinch, the radius a is found to increase more rapidly with J than the radius of the magnetic separatrix. Within the range of increasing pinch currents there are therefore three regimes of an Extrap system. For small J the system becomes unstable in the conventional way of unstabilized Z-pinches. For intermediate values of J, the magnetic surfaces become deformed by the external conductor field, and the constraints of this field combine with FLR and cold mantle effects to provide a macroscopically stable state. Finally, for sufficiently large currents J, i.e. when the pinch radius a approaches and even tends to exceed the separatrix radius, the system is expected to become ballooning unstable in regions of bad field line curvature. The present analysis thus provides relations between the basic pinch parameters which can be tested by experiments, and it also contributes to the understanding of Extrap stability in terms of increasing pinch currents.

Additional information

Authors: LEHNERT B ROYAL INSTITUTE OF TECHNOLOGY, STOCKHOLM (SWEDEN), ROYAL INSTITUTE OF TECHNOLOGY, STOCKHOLM (SWEDEN)
Bibliographic Reference: WRITE TO DEPARTMENT OF PLASMA PHYSICS AND FUSION RESEARCH, ROYAL INSTITUTE OF TECHNOLOGY, S-100 44 STOCKHOLM 70 (SWEDEN), MENTIONING REPORT TRITA-PFU-84-07, 1984
Record Number: 1989123019400 / Last updated on: 1987-01-01
Category: PUBLICATION
Available languages: en