Full energy peak efficiency of a clover detector in direct and add-back modes at different source to detector distances: a comparative study

A comparative study of the effect of true coincidence summing (TCS) on the full-energy peak efficiency calibration of a clover HPGe detector, for direct and add-back modes of operation, has been done at different source-to-detector distances (d). The detector response was simulated using the Geant4 toolkit. The TCS correction factors determined by both experimental and analytical methods have been found to agree well with each other. The clover detector in add-back mode exhibits larger summing corrections than the direct mode for the same distance d. The distance d below which the summing correction becomes significant for the add-back mode of measurement is found to be higher than the corresponding distance for the direct mode of measurement for a clover detector.