Plasma equilibrium in an ℓ = 3 stellarator with a transverse correcting field

Abstract

A description is given of theoretical and experimental research into the possibility of using, an automatically regulated transverse field to increase the gas-kinetic pressure limit of the plasma in an fi = 3 stellarator. In terms of a simplified theoretical model the various laws governing the control of a transverse field by means of feedback are analysed. It is shown that a control system based on magnetic measurements can provide the accuracy required for maintaining an equilibrium close to optimum. Experimental data relating to equilibrium effects obtained on the Uragan stellarator are in close agreement with theory.

Determination of plasma shift in a stellarator from magnetic measurements

“…What, one may ask, can be gained from knowing only 8\J/ without any additional information. This question is an essential one for right appraisal of the experimental methods used in Uragantype stellarators to determine plasma shift [5] and energy content [6,7] from 6^.…”

“…In Ref. [5] the shift A b was calculated with the formula A b /b = const 6^/Bj. As we can see now, this formula does not work for small values of B,/B*, and for large values it is not accurate enough.…”

“…The magnetic measurement technique developed for tokamaks can also be applied to stellarators, as is done in the Uragan facilities [5][6][7]. Therefore, the problem of providing a strict theory of magnetic measurements for stellarators arises.…”

“…In this paper, we present such a calculation for an ordinary stellarator with a plasma column of 'average' circular cross-section, and we consider the problem of determining the position of the plasma column from poloidal magnetic flux and field measurements. Previously, some evaluations of the relationships between measured values and equilibrium parameters have been made [5][6][7], but they are contradictory, and in the tokamak limit they yield inaccurate results. Our calculation is based on fairly general assumptions, and its results are universally applicable and valid both for stellarators and for tokamaks.…”