Analytical approach for radioactivity correlation of disc sources with HPGe detector efficiency

• We examine changes in the detector efficiency depended on source diameter and source detector separation.
• The concept of a double point detector model approach (DPDM) was used.
• Used the efficiency transfer factor for cases of sources with different geometry, transfer from a point source to a disc source.
• The dependence of the count rates on the efficiency estimate.

The HPGe detector efficiency is measured as a function of source to detector separation using disc sources of 131I with diameter ranging from 10 to 400 mm. Detector efficiencies are characterized using single photon point-like standard sources at different distances; the calculated efficiencies for disc sources were analyzed by utilizing the double point detector model (DPDM) and the efficiency transfer method. The developed approach provided satisfactory results. The axial variation and radial dependence for disc sources efficiency determination in gamma-ray spectrometry were described with both gamma ray standard sources and measured samples as their extended sources.