Positron plasmas in the laboratory and the legacy of Cliff Surko.

What started as a novel idea for a tokamak diagnostic [1] eventually revolutionized low energy positron science. Here, we highlight the ways in which Cliff Surko and collaborators coupled early sources for low energy positrons with non-neutral plasma physics to develop the first buffer-gas-trap for positrons [2], and further, how unexpected challenges lead to opening a new experiment to study isolated matter-antimatter interactions. The broad range of physics enabled by these developments will be surveyed, including fundamental positron annihilation with atoms and molecules [3], the road to trapped antihydrogen, and novel confinement and manipulation techniques using non-neutral plasmas [4]. Finally, a look to the future, and how all of these ideas are being combined with the goal of studying a magnetized electron-positron pair plasma [5].

[1] Surko, C. M., et al. "Use of positrons to study transport in tokamak plasmas." RSI 57, 1862 (1986).

[2] Surko, C. M., et al. "Positron plasma in the laboratory." PRL 62, 901 (1989).

[3] Gribakin, G. F., et al. "Positron-molecule interactions: Resonant attachment, annihilation, and bound states." RMP 82, 2557 (2010).

[4] Danielson, J. R., et al. "Plasma and trap-based techniques for science with positrons." RMP 87, 247 (2015).

[5] Stoneking, M. R., et al. "A new frontier in laboratory physics: magnetized electron–positron plasmas." JPP 86, 155860601 (2020).