LaBr3:Ce and NaI:Tl performance comparison for single photon emission detector

In this work, an experimental comparison of the capabilities of a scintillation detector based on a NaI:Tl and a LaBr3:Ce monolithic crystals is presented. The main advantage of LaBr3:Ce respect to NaI:Tl is its very high light yield (i.e. 63photons/keV versus 38photons/keV), allowing a considerable improvement of the statistical factor affecting light collection and, consequently, Spatial Resolution (SR) and Energy Resolution (ER). Nevertheless, the following results show that the improvement of the SR with the LaBr3:Ce is smaller than expected. As analyzed, it could be due to the LaBr3:Ce refractive index higher than the NaI:Tl one, that leads to a loss of scintillation light. In fact, the measurements produce similar imaging results (SR at crystal center is about 1.1mm for both crystals), while the ER is slightly better for the LaBr3:Ce, as expected (7.6% and 8.8% for LaBr3:Ce and NaI:Tl, respectively). This work encourages a further and more specific analysis about how the refractive index affects the amount and the shape of crystal light distribution.