Measurement of the STS-6 counter efficiency to gamma radiation

Gamma radiation measurements by the STS-6 proportional counters in bad geometry at 0.1-2 MeV γ-radiation are presented to evaluating the efficiency of measurement of the decay product radiation. This efficiency is reduced to ''good'' geometry by introduction of an effective space angle with account of γ-radiation losses and absorption of compton electrons in the material of the counter walls. The counter efficiency for γ-radiation photons of the given energy was determined as a ratio of difference of the real counting rate and the background to the number of photons in the counter active volume. It ws considered in this case, that the active volume of the counter is such a volume, where the secondary charged particles are detected with 100; probability. The experiments in which the counter was placed at different distances from the source were conducted for identification of this volume. At 17 mm distance of the counter from the source the effective space angle of the counter constituted 0.36 sr and its dependence on the energy did not exceed 2%. The error of efficiency determination comprised the error of radiation dose determination, error of measuring the real counting rate, background counting rate with account of the error of ''dead'' time determination as well as the error of identification of the effective space angle and the error of calculating partial efficiencies for certain lines occurring at the decay of the given nuclide. The total error with account of the errors of determining the half-decay periods constituted 3%