Performance and fabrication of thin film NaI(Tl) scintillators for use on imaging photomultiplier tubes

This paper describes the preparation and performance of thin film NaI(Tl) scintillators using two techniques, standard bulk load evaporation (BLE) in which a single resistance-heated boat contains the total source quantity, and powder flash evaporation (PFE). Using PFE, a film's characteristics can be easily reproduced, and the relative light yield can be predicted by controlling the substrate temperature, the boat temperature, and the composition of the source. The authors have made PFE films with homogeneous thallium concentration which surpass the highest light yield they measured for two commercially available single crystal NaI(Tl) scintillators and for BLE films with optimized light yield. They discuss the parameters that control the film's light yield and the predicted detection efficiency of an x-ray detector using these films coupled to an imaging phototube