Efficiency Calculation of Gamma Detectors by Monte Carlo Methods

γ-Ray spectrometry is a powerful nondestructive multielemental analysis technique. Its quantitative application requires efficiency calibration. Among the methods available for the computation of the efficiency calibration curve, Monte Carlo simulation is ever increasing in popularity. The need for Monte Carlo simulation is the consequence of the inability of experimental calibration to cope with the broader scope and measuring configurations (shape, volume, and matrices of the samples), with the enhanced coincidence-summing nuclide specific effects (favored by the current tendency to use high-efficiency detectors) and with the desired performance parameters (detection limit and uncertainty) met in present-day applications of γ-ray spectrometry. The availability of a variety of Monte Carlo packages that can be applied to efficiency computation, several of them user friendly indeed, enlarged the class of potential users of this method. While experimental calibration remains the preferred method in the case of point sources and specific volume sources, such as solutions, it is the flexibility of Monte Carlo calculation that can provide a comprehensive calibration of γ-ray detectors for a broad range of applications. In this article, the principles of Monte Carlo method are introduced, the applications to detector simulation are presented, and the solutions of typical problems in the calibration of γ-spectrometry systems are reviewed.