NIFS-362

FULL TEXT (PDF, 796 KB)


Author(s):

V.D. Pustovitov

Title:

Suppression of Pfirsch-schluter Current by Vertical Magnetic Field in Stellarators

Date of publication:

June 1995

Key words:

stellarator, plasma equilibrium, Pfirsch-Schluter current, plasma column shift

Abstract:

This article is devoted to the problem whether it is possible to make stellarator configuration insensitive to plasma pressure using external vertical magnetic field as a control parameter. Conventional stellarators with a planar circular axis are analyzed. It is shown that for these systems the condition of Pfirsch-Schluter current suppression can be formulated as a two-dimensional equation with all values expressed through the vacuum magnetic field only. The major advantage of this formulation is that it allows to solve the problem without solving equilibrium equations. It is used as a basis to show that complete suppression of Pfirsch-Schluter current by means of the vertical field is possible, in principle, either in shear-free systems or in stellarators with l geq 3. In l=2 stellarators with a shear it is possible to get significant reduction of the current and to suppress pressure-induced plasma column shift. This can be called an integral independence on beta in contrast to the true local independence in other cases. In all cases large inward shift of plasma column is necessary. It is out of operational range in all existing devices except Heliotron E. In recent experiments in Heliotron E the state "integrally" independent on beta was almost achieved. The present study was stimulated by this result.

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