Thermalization Rate of Positronium in Mesoporous Silica Thin Films Studied With Angular Correlation of Annihilation Radiation Spectrometry
Abstract
Positronium (Ps) continues to prove itself an ideal candidate for studying various topics in physics, from conducting a precise test of bound-state quantum electrodynamics theory to the creation of the first Ps Bose-Einstein Condensate. Positrons from a sodium-22 radioactive isotope are moderated, trapped, transported, and focused onto a small spot on a suitable target. Mesoporous silica thin film targets yield considerable positronium formation, thereafter magnetic quenching creates majority singlet-state Ps annihilating into two gamma rays with deviations from collinearity resolved to 0.1 mrad with an Angular Correlation of Annihilation Radiation (ACAR) spectrometer. The construction of said spectrometer is detailed, including the characterization of the detectors, power supply, and data collection devices used. The spectrometer will be used for measuring the thermalization rate of positronium as well as material defect studies.