The creation and first studies of electron plasmas in the Columbia non-neutral torus.

摘要

The Columbia Non-neutral Torus (CNT) is a simple stellarator designed to study non-neutral, partly neutral, and positron-electron plasmas on magnetic surfaces. This thesis describes computational work done to aid in the design of CNT, contributions to the field line mapping effort of CNT, methods developed to make measurements of pure-electron plasmas, and the first experimental plasma results in CNT.; A set of magnetic field line follower codes were developed and used to aid in the design of CNT, to determine the values of experimental parameters for optimized confinement properties, and to determine the error field sensitivity. This optimization led to an ultra-low aspect ratio, error field resilient stellarator design. Subsequent experimental field line mapping results confirmed the numerical predictions.; The plasma physics experiments described in this thesis explore the equilibrium of pure-electron plasmas confined on the magnetic surfaces of CNT. A comparison of the best measured confinement times with relevant time scales indicates these plasmas were in a macroscopically stable equilibrium and confinement is improved by the large electric fields provided by the plasma space charge. Other experiments indicate that confinement was limited by transport caused by the electrostatic perturbation from insulating rods on which the emitter and diagnostic filaments are mounted and by transport caused by neutrals.; Radial equilibrium potential, temperature, and density profiles have been measured for a variety of magnetic field strengths, emitter biases, and neutral pressures. Measured electron temperatures of approximately 5 eV and average densities of approximately 1012 m-3 indicate that relatively cold, small Debye length plasmas have been created. These plasmas satisfy the plasma criterion. The equilibrium is strongly dependent on the emitter bias. In contrast, no clear relationships between the equilibrium and magnetic field or neutral pressure have been discovered. Equilibrium reconstructions performed using the potential, temperature, and density profiles indicate that numerical results are consistent with the experimental ones.