EFFICIENCIES AND PHOTOFRACTIONS FOR GAMMA RADIATION ON SODIUM IODIDE (THALLIUM ACTIVATED) CRYSTALS
Open Access
- 1 August 1958
- report
- Published by Office of Scientific and Technical Information (OSTI)
Abstract
The efficiencies and photofractions for monoenergetic garnma raps incident on sodium iodide (thallium activated) crystals have heen calculated by the Monte Carlo method. The calculations have been carried out for broad parallel-beam sources, point sources on the crystal axis, and disk sources, all for photon energies of 0.279, 0.861, 1.33, 2.82, and 4.45 Mev. The crystals considered were right circular cylinders with radii of radius, heights of 1.0, 2.0, 4.0, and 8.0 inches. The effect of the escape of annihilation gammas from the crystal was taken into account in the Monte Carlo calculation; however, no correction was made for escape of bremsstrahlung from secondary electrons and positrons. This latter correction is of importance only at the largest energies and for the smallest crystals where it affects the photofractions by a few per cent. (auth)Keywords
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