Light Extraction Enhancement Techniques for Inorganic Scintillators

In several applications which rely on the use of ionizing radiation, scintillators play an important role in the detection chain. An efficient extraction and detection of the generated light is mandatory to provide sufficient information on the high energy particles interacting with the crystal itself. The amount of light extracted, as well as its temporal distribution, have a direct impact on the overall system performance. In positron emission tomography (PET), energy resolution and coincidence resolving time are two of the main parameters, which both depend on the amount of detected light. Furthermore, if pixelated crystals with sub-millimiter pitch are needed, such as in preclinical PET scanners, the use of conventional reflectors on the crystal pixel surface implies a dramatic reduction of the packing fraction, due to their thickness. In this work several light extraction techniques for the most used inorganic scintillators are presented and compared. A novel approach, using a combination of distributed Bragg reflectors, metal coatings, and photonic crystals, is also introduced. A maximum gain of ~40% on light extraction and ~18% on energy resolution was observed.