The application of Fourier analysis of the azimuthal field distribution to a study of equilibria and instabilities in a toroidal pinch discharge

Abstract

The equilibrium displacement of a current-carrying plasma column in a torus has been determined from measurements of the first-order Fourier component of the azimuthal field using coils with the number of turns per unit length varying sinusoidally. The displacement cannot be obtained directly if currents flow outside the plasma column, but an independent measurement of the displacement then yields information about the current distribution. Parameters associated with helical equilibria and instabilities such as growth, radius and wavelength are obtained from the Fourier components.