Rydberg-positronium velocity and self-ionization studies in 1T magnetic field and cryogenic environment

TL;DR

This study measures the velocity and self-ionization of Rydberg-positronium in cryogenic and magnetic conditions, aiming to optimize antihydrogen production for antimatter research.

Contribution

It provides the first detailed velocity and ionization measurements of Rydberg-positronium in a cryogenic magnetic environment relevant to antihydrogen experiments.

Findings

Velocity measurements along two axes in cryogenic magnetic field

Quantification of self-ionization due to motional Stark effect

Discussion on optimizing Rydberg-positronium production for antihydrogen

Abstract

We characterized the pulsed Rydberg-positronium production inside the AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) apparatus in view of antihydrogen formation by means of a charge exchange reaction between cold antiprotons and slow Rydberg-positronium atoms. Velocity measurements on positronium along two axes in a cryogenic environment (10K) and in 1T magnetic field were performed. The velocimetry was done by MCP-imaging of photoionized positronium previously excited to the $n=3$ state. One direction of velocity was measured via Doppler-scan of this $n=3$-line, another direction perpendicular to the former by delaying the exciting laser pulses in a time-of-flight measurement. Self-ionization in the magnetic field due to motional Stark effect was also quantified by using the same MCP-imaging technique for Rydberg positronium with an effective principal quantum number $n_{eff}$ ranging between 14 and 22. We conclude with a discussion about the optimization of our experimental parameters for creating Rydberg-positronium in preparation for an efficient pulsed production of antihydrogen.