Using Measurements of the Trivelpiece-Gould Mode Dispersion Relation to Determine Temperature in Toroidal Pure-Electron Plasma

In the Lawrence Non-Neutral Torus II (LNT II), electron plasma is confined using a purely toroidal magnetic field (R₀ = 18 cm, B < 1 kG) for confinement times exceeding 1 second. The LNT II can be operated as a partial torus in which plasma is confined in C-shaped toroidal sectors or as a fully toroidal, closed trap. In the past, a plasma expansion method has been used to measure the temperatures of the electron plasma, which are approximately 2 eV. We attempt to measure the temperature a second way. We use the Trivelpiece-Gould wave dispersion relation. These waves propagate toroidally and are launched and detected from opposite ends of the plasma. Toroidally propagating bounded plasma waves exist below the plasma frequency due to the boundary conditions of the torus. The Trivelpiece-Gould mode has higher frequencies than the diocotron modes of plasma waves. Using this method, for a plasma frequency of 20 MHz, we expect to be able to measure differences in dispersion relation at different temperatures of frequencies in the range of 10 MHz.