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

A ‘‘rotating wall’’ perturbation technique enables confinement of up to 3310 electrons or 10 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 kzÞ0 and mu51 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. © 2000 American Institute of Physics. @S1070-664X~00!05407-0#