Complex Gamma Ray Spectra Analysis

The gamma ray spectrometry laboratory of the University of Bucharest was designed for the analysis of low-level radioactivity samples. High efficiency shielded HPGe detectors are used. Efficiency calibration is achieved by complementing experimental calibration with Monte Carlo computation carried out using GESPECOR, also applied for the evaluation of coincidence summing corrections. Low detection and decision limits are challenging, and the method to respond to this situation is presented. Using a blank sample in the same experimental conditions as the actual sample turns out benefic for precise peak subtraction. Procedures for peak finding were developed, which include analysis of the peak area/FWHM ratios, hypergeometric alert, in order to establish confidence limits concerning the actual existence of a certain peak in the spectrum. The method is oriented to numeric solutions rather than developing complex fitting functions that might not be appropriate. Development of a software insuring retrospective predictability and asking for human intervention in controversial situations is in progress.