Progress towards the trapping and accumulation of large numbers of positrons.

The APEX collaboration aims to produce neutral pair plasmas, composed of equal quantities of electrons and positrons, magnetically confined in two different traps: a levitated dipole and a stellarator. More than $10^10$ positrons are needed to achieve a short-Debye-length plasma with a volume of 10 L and a temperature of $< 1$~eV. This necessitates new advances in positron accumulation and storage. These advances are enabled by non-neutral plasma techniques developed for the manipulation and control of single-species plasmas. Here we report on progress in developing antimatter traps to achieve the required number of positrons for the pair-plasma experiment. A multi-stage buffer-gas-trap (BGT) will be used for the efficient trapping of the high-flux positron beam from the NEPOMUC high-flux positron source in Munich, Germany. A continuous beam of positrons from NEPOMUC will be magnetically guided into a low-pressure molecular gas, where inelastic collisions enable efficient positron capture (maximum expected accumulation $< 10^9$ positrons). Accumulation of larger numbers of positrons will be achieved in a separate multicell Penning-Malmberg trap in UHV and a 5 T magnetic field that is currently under development.