Counting Efficiency of Co 56,Co 58 and Co 60 with 2 Counters and 3 Counting Technics

Abstract

Summary

A NaI well scintillation counter and a beaker adapted to fit on and around the NaI well as well as a plastic well scintillation counter, were used to compare efficiency of Co⁵⁶, Co⁵⁸ and Co⁶⁰ function of volume. The plastic well counter is as efficient for Co⁵⁶ as the NaI well and more efficient for Co⁵⁸ and Co⁶⁰ than the NaI well for small volumes (1-4 ml). For intermediate volumes (4-250 ml) the plastic well is the more efficient and the efficiency is almost independent of sample volume from 10-100 ml. Mice or small rats up to about 75 g and tissue samples can be counted in the plastic well without correction for geometry. The efficiency of 250 ml in the plastic scintillation counter is 22.6, 11.6 and 18.3% for Co⁵⁶, Co⁵⁸ and Co⁶⁰ respectively and 7.8, 3.5, and 3.8% respectively for 1000 ml using the beaker on the NaI well. The choice of instrument for counting large volumes is discussed.