Scintillation Spectrometer with an Anticoincidence Annulus of NaI(Tl)

Abstract

In the scintillation spectrometer described, the main detecting crystal of NaI(Tl) is enveloped by a hollow cylinder of NaI(Tl) in anticoincidence with the main crystal. This system completely suppresses the peaks associated with the escape of the two quanta from the annihilation following pair production, and it reduces the Compton background by a factor of 7 for 4.43-Mev gamma rays and by a factor of 5 for those of 6.1 Mev.