Positron trapping in a magnetic mirror configuration

In a first step towards generating an electron-positron plasma, a proof-of-principle experiment is reported in which externally injected slow positrons and electrons are trapped in a magnetic mirror configuration by electron (positron) cyclotron resonance heating. Positrons with an average injection energy of 1 eV from a 0.6 mCi Na-22 source/moderator combination are demonstrated to be trapped in the mirror. With a primary flux of 5.3 × 102 moderated positrons/s, an estimated equilibrium density of 2 × 102 cm−3 is obtained in a 20 cm3 volume. With an appropriate increase of the injected slow positron flux, densities in the 107 cm−3 range can be expected. In replacing the positron source with a small electron gun, a trapped electron density of 3 × 108 cm−3 in the same volume was obtained.