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UBC Theses and Dissertations

Dynamics of a theta pinch discharge in a transverse magnetic field Lee, William Leung


The suppression of radial hydromagnetic oscillations of a theta pinch plasmoid produced in air has been investigated with magnetic probes and a framing camera. In the presence of essentially static and uniform magnetic bias fields (produced by Helmholtz coils) it was found that the oscillations are suppressed by a flip instability of the plasmoid and the direction of flip is controlled by the transverse magnetic field. Using the suppression of radial hydromagnetic oscillation as the criterion for flip, it is found experimentally that if [formula omitted] is greater than a critical value, then the plasma ring flips. [formula omitted] is the strength of the bias field perpendicular to the axis of the theta coil, 'a' the radius of the discharge vessel and 'p' is the gas pressure. The experimental results are interpreted in terms of a snowplough model for the discharge, in which the plasma current forms two concentric cylinders. The predictions of the theory agree with the experimental observations.

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