A buffer-gas trap for the NEPOMUC positron beam: optimization studies with electrons.

Buffer-gas traps (BGTs) use inelastic interactions with nitrogen and CF₄ molecules to capture and cool positrons from a continuous beam. These devices are invaluable for high-resolution studies of matter-antimatter interactions, antihydrogen research and positronium laser spectroscopy. We describe a project with the goal of producing a single-component plasma containing more than 10⁸ low-energy positrons in a BGT using the NEPOMUC (NEutron induced POsitron source MUniCh) high-intensity positron beam [1]. Details of the BGT are outlined and results are presented from experiments in which an electron beam, with a similar intensity and energy spread to the remoderated NEPOMUC beam, was used to create an electron plasma. Studies include rotating wall compression, stacking in a separate accumulator, and pulsed ejection into narrow electron beams. This trap system is a vital component of the APEX project, which aims to create a low-temperature electron–positron pair plasma.

[1] A. Deller et al., Journal of Plasma Physics 89, 935890602 (2023).