Performance evaluation of a p-type co-axial HPGe detector: Long-term analysis of key parameters for gamma spectroscopy

Accurate determination of the parameters of each high purity germanium, HPGe detectors ensure the precision of quantitative results obtained from spectrum analysis. This study presents a comprehensive performance evaluation and long-term quality control assessment of a high-purity germanium (HPGe) gamma spectrometry system that has been operational for over 15 years. Key spectrometric measures were recorded, including energy resolution, peak shape ratios, asymmetry, peak-to-Compton ratio, relative efficiency, electronic noise, minimum detectable activity (MDA), and repeatability and reproducibility of the system. With the assistance of a calibrated source Co-60, the detector exhibited a commendable energy resolution of 2.01 keV (FWHM), along with good peak shape ratios (FWTM/FWHM = 1.73, FWFM/FWHM = 2.48) and a peak-to-Compton ratio of 52.2, indicating high resolution and zero spectral distortion. Relative detector efficiency was 33.88 % at 1332.5 keV, and electronic noise was negligible at 0.178 %. MDA for certain radionuclides was found to be in the range 0.048–0.605 Bq/kg, which showed good sensitivity even for low-activity peaks. Repeatability tests gave a coefficient of variation (%CV) less than 1 % for all peaks measured, while reproducibility was confirmed with t-test and F-test statistical tests. A Shewhart $\bar{X}$-control chart revealed that at all times in all cases, measurements were within control limits, though a slight downward trend in the last few years suggests potential need for recalibration or maintenance. The findings corroborate the sustained conformity of the system to ISO/IEC 17025 quality standards and its sufficiency for precise and trustworthy gamma-ray analysis in radionuclide quantification and environmental monitoring.