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 sou rce 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 t emperature, and the composition of the source. We have made PFE films with homogeneous thallium concentration which surpass the highest ligh t yield we measured for two commercially available single crystal NaI( Tl) scintillators and for BLE films with optimized light yield. We dis cuss the parameters that control the film's light yield and the predic ted detection efficiency of an x-ray detector using these films couple d to an imaging phototube.