Injection and confinement of positron bunches in a magnetic dipole trap.

We demonstrate the efficient injection of a pulsed positron beam into a magnetic dipole trap and investigate the ensuing particle dynamics in the inhomogeneous electric and magnetic fields. Bunches of ∼10^{5}e^{+} were transferred from a buffer-gas trap into the field of a permanent magnet using a lossless E×B drift technique. The Δt≈0.2µs pulses were short compared to the toroidal rotation period, τ_{d}≈16µs, and e^{+} confinement time, τ_{c}≈0.6 s. The redistribution dynamics were studied by measuring the delayed γ-ray emission as the trap was emptied. This work extends the record for the number of low-energy positrons held in a dipole trap by two orders of magnitude and represents a significant advance toward the confinement of an electron-positron pair plasma.