Detector for positronium temperature measurements by two-photon angular correlation

Abstract

We report on the design and characterization of a modular γ-ray detector assembly developed for accurate and efficient detection of coincident 511 keV back-to-back γ-rays following electron-positron annihilation. Each modular detector consists of 16 narrow lutetium yttrium oxyorthosilicate scintillators coupled to a multi-anode Hamamatsu H12700B photomultiplier tube. We discuss the operation and optimization of 511 keV γ-ray detection resulting from testing various scintillators and detector arrangements concluding with an estimate of the coincident 511 keV detection efficiency for the intended experiment and a preliminary test representing one-quarter of the completed array.

Conditions for obtaining positronium Bose–Einstein condensation in a micron-sized cavity

“…We conclude that a sizable fraction of the positrons that escape into the cavity will make Ps and that it should be possible to produce a high density collection of cold polarized triplet Ps that would form a BEC with a critical temperature of about 170 K. The presence of such a BEC would be identified by measuring the angular correlation of annihilation radiation with an angular resolution of 0.1 mrad [53].…”

Resonant shifts of positronium energy levels in MgO powder

“…The ability to measure Ps properties in various experimental environments will be critical for future experiments involving high-density Ps, such as studies of Ps 2 molecules [74], and to continue progress towards Ps BEC along the lines suggested by Platzman and Mills [13,17]. An optical measurement of the temperature of dense Ps confined in a cavity is probably not possible due to line narrowing [29], but the angular correlation of two-photon Ps annihilation radiation can be used [75].…”

Measurement of the annihilation decay rate of 2 3S1 positronium

“…In the absence of colder atoms, more extreme velocity selection may improve the experiment, but would require more efficient γ-ray detection. This would be possible if a large detector array were employed; for a modular system with many small detector segments that record individual decay events [45], which would remove the need to correct for solid angle variations, and improve the overall detection efficiency.…”