Apparatus for Positronium Production via Rydberg Cesium Charge-Exchange

This dissertation outlines research conducted with positrons towards the production of positronium via charge-exchange with Rydberg cesium atoms. Positronium is a purely leptonic atomic system that is ideal for tests of quantum electrodynamics (QED) theory. A frozen neon crystal moderator produces low-energy positrons from a radioactive source that are magnetically guided towards a buffer-gas accumulator. The buffer-gas accumulator has been optimized to store large numbers of positrons (>40 million in 2 minutes) for a long time to perform a variety of experiments. The 200 meV energy width of the accumulated positrons is suitable for charge-exchange experiments. The positrons are then magnetically guided through a 90 bend towards an apparatus where charge-exchange takes place.

The experimental techniques to produce and detect Rydberg positronium are described and the progress is presented. A data acquisition system has been developed to detect positron signatures based on the coincidence-timing of back-to-back annihilations on a single-event basis where time and energy analysis cuts allow strict criteria to distinguish signal from background.

The long-term goal of the research program is to perform precision spectroscopy of the internal structure of Rydberg positronium. These measurements can be used to determine fundamental constants of nature and to test QED theory. A deviation from the QED predictions can be an indication of physics beyond the Standard Model. Physics beyond the Standard Model can provide a solution to unsolved problems, such as the matter-antimatter imbalance that is observed today.