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An all sodium iodide anticoincidence shielded total absorption spectrometer for low-level radionuclide analyses

1970; Elsevier BV; Volume: 83; Issue: 2 Linguagem: Inglês

10.1016/0029-554x(70)90471-4

1878-3759

N.A. Wogman,

Radiation Detection and Scintillator Technologies

Abstract An anticoincidence shielded gamma-ray spectrometer has been designed from a 34 cm dia. by 31 cm thick NaI(Tl) ingot which surrounds an 18 cm dia. by 22 cm thick NaI(Tl) principal detector. The spectrometer and the principal crystal are hermetically sealed in a single container. Low background construction materials, as well as low 40 K content phototubes, serve to reduce the background. The low 40 K phototubes reduced the 40 K detected by the principal crystal approximately twofold compared to standard glass phototubes. The background in the energy range from 0.1 to 3 MeV was reduced from two- to fivefold by the anticoincidence shield. The efficiency of the system for a point and a 70 ml source is approximately fivefold greater than that of a 7.5 cm dia. by 7.5 cm thick NaI(Tl) crystal. By means of the anticoincidence crystal, the Compton edge for 137 Cs was reduced by 2.5-fold to produce a peak-to-Compton edge ratio of approximately 160: 1. The system has been utilized for low-level radionuclide analyses of single gamma-ray emitters and has been compared to NaI(Tl) multidimensional and Ge(Li) gamma-ray spectrometers.