Observation of Trivelpiece-Gould modes in toroidal pure electron plasma

Non-neutral (electron) plasma are confined in the Lawrence Non-neutral Torus II (major radius = 17.4 cm, minor radius = 1.27 cm, B $\sim $ 550 G) with a purely toroidal magnetic field. The plasma is diagnosed by measuring the flow of image charge to and from isolated sectors of the fully segmented conducting boundary. Long confinement times ($>$300 ms) in both partial (270$^{\circ}$ arc) and fully toroidal traps indicate the production of nearly steady-state conditions and permit study of intrinsic toroidal effects on dynamics and transport. We report the first observations of Trivelpiece-Gould modes (space-charge waves) [A.W. Trivelpiece and R.W. Gould, J. Appl. Phys. \textbf{30}, 1784 (1959)] with poloidal mode number $m$=0 in toroidal non-neutral plasma. The fundamental mode at 1.3 MHz and the first few harmonics are excited with a tone burst in partially toroidal conditions. We also report on attempts to observe Trivelpiece-Gould modes in plasma confined in a fully toroidal trap, and on attempts to use numerical modeling to identify toroidal effects on these modes. This work is supported by the National Science Foundation Grant PHY-0812893.