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The positron-electron pair annihilation in two photons is known for itsnumerous applications using PET scanners. The decay of Positronium (Ps) from astandard sealed source in more than two photons is less likely but can beobserved with a relatively simple setup. The main goal of this experiment wasto verify momentum and total angular momentum conservation principles atsubatomic level through the Ps annihilation. The two spin configurations of Psare produced with a beta+ source. The decay modes are identified usinggamma-ray spectroscopy techniques in a double and triple coincidence setup.Three germanium detectors (or two HPGe and one NaI(Tl) detectors) and a digitalelectronic system are required.

Observation of triple-photon decay in positron-electron pair annihilation: a triple coincidence setup for the undergraduate laboratory