Compression of trapped positrons in a single particle regime by a rotating electric field

Abstract

Positrons confined in a cylindrical Penning trap are compressed radially by applying a rotating electric field. Previous experiments were conducted with large numbers of positrons in the plasma state. Compression of small numbers of positrons in the single particle regime is reported for the first time. For low values of applied rf amplitude, the compression occurs in a narrow band of frequencies centered on the axial bounce frequency. For larger amplitudes, the compression extends to a broad range of frequencies below the bounce frequency. Under certain conditions, very rapid compression can be obtained and central density doubling times of only a few milliseconds have been observed. Possible models for the effect are discussed. Potential application to the production of brightness enhanced positron beams is described.