The influence of counting geometry and lining on the Compton continuum in well-type detectors

To demonstrate the influence of counting geometry on the performance of a well-type detector, as represented by the P/C- and P/T-ratio, Cs-137 and Co-60 sources were measured at 30 cm distance from the well and in the well; the latter both with and without a gold lining. Observed differences in the Compton continua are discussed. A significant increase in P/C- and P/T-ratios for Cs-137 is found when repositioning the source from 30 cm distance to a position in the well. For Co-60, only the P/T-ratio shows a similar behaviour. It is concluded that the detector performs best when counting the source in the well without a lining. It is also concluded that, even though the P/T-ratio is preferred as an index of performance, only mono gamma emitting radionuclides should be used when measuring P/C-ratios of a well-type detector.