An Experimental Study of Waves in a Toroidal Electron Plasma

Electron plasma is confined using a purely toroidal magnetic field ($R_{o}=$ 18 cm, $B <$ 550 G) for times ($\sim $1 s) that are much longer than any of the dynamical timescales of the system. Wave dynamics are compared for two experimental regimes: 1) a toroidal arc (or bent Penning-Malmberg trap) and 2) a fully toroidal trap in which the no electrostatic fields are used for confinement. Damping of the $m$=1 ($k$=0) diocotron mode is explored to assess the extent to which rotational and/or magnetic pumping transport mechanisms are operative. The frequency of the $m$=2 ($k$=0) diocotron mode is used to directly measure the transport rate and determine its scaling with control parameters. Resonant standing wave plasma modes ($m=$0) are excited in order to determine the Trivelpiece-Gould dispersion relation and identify toroidal and thermal effects.