Mixing activity-calibrated and uncalibrated gamma-ray sources in efficiency calibration

A method to calibrate the absolute efficiency of HPGe detectors in a large energy range using both activity-calibrated and uncalibrated multienergy gamma-ray radioactive sources is presented. The adopted efficiency calibration function var epsilon(E) has the simple form ln var epsilon(E)=a0+a1 ln(E/EB)+a2 ln2(E/EB). Different parameters a0 are simultaneously fitted to the activity-calibrated and uncalibrated sources experimental efficiency data by the least-squares method. As an application example, the calibration of a HPGe detector in the 500 to 3500 keV energy range using a 207Bi activity calibrated source and one uncalibrated 56Co source is described.