Radial compression and inward transport of positron plasmas using a rotating electric field

It has recently been demonstrated that positron plasmas confined in a Penning-Malmberg trap can be compressed radially by applying a rotating electric field [Phys. Rev. Lett. 85, 1883 (2000)]. A more complete description of the original experiments is presented, together with the results of new measurements. Good coupling of the rotating electric field is observed over a broad range of frequencies. The heating caused by the rotating field is counteracted by cooling using a polyatomic gas. Rapid compression rates n/n similar to 15 s(-1) can be achieved, with central density increases of a factor of 20 or more. The good coupling and high compression rates can be explained in terms of excitation of heavily damped Trivelpiece-Gould modes, or alternatively as coupling directly to particle bounce resonances. Potential improvements and applications are discussed, including the production of high-density positron plasmas and brightness-enhanced positron beams. (C) 2001 American Institute of Physics.