Experimental studies on the angular distribution of scintillation light from small BGO crystals

The angular distribution of light emitted when a 511 keV gamma ray impinges on a small 2 × 2 × 20 mm BGO scintillation crystal is calculated by Monte-Carlo simulation and experimentally verified via its intensity distribution on a CCD sensor at various distances. Direct comparison of calculated and experimental images confirms that the angular distribution of the scintillation light is Lambertian with an index of directivity between 0.8 and 1.0. The long-term goal of our project is the construction of a dual positron emission tomography (PET) — magnetic resonance imaging (MRI) scanner. Accurate knowledge of the angular distribution of light emitted from small crystals is crucial for the implementation of fibre-optic bundles that will efficiently transport the scintillation light out of the high magnetic field and constrained spatial volume of the MRI magnet bore, to a convenient and low-field region meters away.