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.