Confinement and manipulation of non-neutral plasmas using rotating wall electric fields

A "rotating wall" perturbation technique enables confinement of up to 3x10(9) electrons or 10(9) ions in Penning-Malmberg traps for periods of weeks. These rotating wall electric fields transfer torque to the particles by exciting Trivelpiece-Gould plasma modes with k(z)not equal 0 and m(theta)=1 or 2. Modes that rotate faster than the plasma column provide a positive torque that counteracts the background drags, resulting in radial plasma compression or steady-state confinement in near-thermal equilibrium states. Conversely, modes that rotate slower than the plasma provide a negative torque, and enhanced plasma expansion is observed. The observed Trivelpiece-Gould mode frequencies are well predicted by linear, infinite-length, guiding-center theory. (C) 2000 American Institute of Physics. [S1070- 664X(00)05407-0].