Studies of < j x b > Current Drive in a Conventional Plasma Torus

Author: Michael James Dutch

Dutch, Michael James, 1988 Studies of < j x b > Current Drive in a Conventional Plasma Torus, Flinders University, School of Chemical and Physical Sciences

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Abstract

This thesis describes experimental and theoretical studies of conventional toroidal plasma equilibria which have been generated and maintained by the application of an external travelling electromagnetic wave. The experimental work was performed in several devices using an argon plasma. The plasma was embedded in a steady toroidal magnetic field for stability. A steady vertical magnetic field was applied for equilibrium. The travelling radio-frequency (RF) magnetic field was produced by feeding RF currents, dephased by 900, through coil structures wound around the outside of the toroidal Pyrex glass vacuum vessel. The majority of the experiments were performed with m=1 helical coil structures. Discharges produced with the same conditions of filling pressure and applied toroidal and vertical magnetic fields were very reproducible. The discharges were maintained for the entire duration of the RF pulse. Extensive miniature magnetic probe measurements were undertaken to examine in detail the magnetic structure of discharges produced under various experimental conditions. Two-dimensional polynomial smoothing techniques were used on the magnetic probe data to derive contours of constant poloidal magnetic flux and toroidal current density. A theoretical description of continuous current drive using external m=1 helical coil structures has been developed for an infinitely long plasma cylinder. The theory is based on earlier treatments of transverse rotating magnetic field current drive in a plasma cylinder. In these analyses, the < jxb > non-linear Hall term in Ohm's law is identified as the source of the electromotive force which drives the steady plasma currents. The theory developed in this thesis has been applied to the appropriate experimentally observed plasma/field configurations to yield quantitative estimates of the (volume averaged) electron density, ne, electron temperature, Te and the electron-ion momentum transfer collision frequency, vei, in the plasma.

Keywords: Nonlinear Hall effect current drive,Rotating magnetic field,helical windings,travelling wave,radio-frequency,RF current drive,double helix current drive,rhythmac,rotamak,plasma physics
Subject: Physics thesis

Thesis type: Doctor of Philosophy
Completed: 1988
School: School of Chemical and Physical Sciences
Supervisor: Dr A Lance McCarthy