Barium Fluoride as a Gamma Ray and Charged Particle Detector

"Pure" Barium Fluoride has been found to scintillate to gamma rays and alpha and beta particles. Pulse height of 10% relative to NaI(Tl), emission decay of 0.63 microseconds, fluorescence emission maximum at 3250A have been measured for currently available crystals of BaF2. This paper describes the scintillation performance and pertinent physical properties of BaF2 in relation to some of the commercially available scintillators -- NaI (Tl), CsI(Na), CsI(Tl) and CaF2 (Eu). The low solubility, non-hygroscopic nature and a comparable absorption for gamma rays are particular advantages of BaF2 over the alkali iodide scintillators. Transmission to its fluorescence emission, shorter decay time and a better photelectric absorption cross-section favor BaF2 over CaF2 scintillators. However, the scintillation pulse height of BaF2 is presently lower than the other scintillators, but it is still sufficiently large enough to observe a resolvable Cs137 662 Kev photopeak. The mechanism responsible for scintillation in BaF2 is not well understood at present. A preliminary investigation to understand this mechanism was undertaken in the form of adding impurities of various valencies to BaF2 and also studying the behavior of scintillation with temperature. The data seems to indicate that hole-centers may be playing a primary role in the scintillation emission. An understanding of the mechanism and the improvement and development of BaF2 as a scintillator has been an integral part of the High Z Scintillator Research program maintained for some time by Harshaw.