Rydberg positronium injection of electrons and positrons into a levitated dipole trap

A neutral-beam injection scheme for magnetically trapping electrons and positrons is proposed. Pulsed lasers excite positronium (Ps) to long-lived Rydberg states that drift at speeds of $|\overrightarrow{v}|\sim {10}^5$   $\text{m}{\text{s}}^{-1}$ into the magnetic field of a levitated superconducting coil. The electric field experienced in the reference frame of the rapidly moving atoms is sufficient to ionize a significant portion of the loosely bound Ps. The released electrons and positrons are confined to the poloidal magnetic field lines that wrap around the coil. Rydberg positronium injection (RPI) does not perturb the confinement volume and ensures local charge symmetry. The technique provides equal, low temperatures for the electron and positron distributions, as well as smooth, inwardly peaked density profiles. The range of populated field lines depends on the Ps velocity distribution and the ionization threshold of the Rydberg state. Monte Carlo simulations are used to evaluate the $e^{+}$ efficiency of RPI for the APEX (A Positron-Electron eXperiment) levitated dipole.