PCGAP: Users Guide and Algorithm Description

Abstract

PCGAP is a software package, which was written to provide gamma-ray pulse height spectrum analysis on a personal computer platform using the Windows NT operating system. It is a collection of programs, which provide a wide range of operability extending from the single user environment to the general purpose counting room. Included in the package are necessary data structures and libraries used to compute quantitative radionuclide concentrations. PCGAP also contains techniques to decontaminate photopeak interferences; determine activity concentrations for radionuclides independent of their associated spectral photopeak size; and three methods to determine the energy scale of a spectrum.PCGAP performs a non-linear least squares fitting of a Gaussian function to spectral photopeaks. The fitting algorithm can fit up to five concurrent photopeaks using a common spectral background. The package includes a program that will automatically locate spectral photopeaks, fit them to a Gaussian function, identify the radionuclides associated with the found photopeaks, and compute a net activity concentration, and for an 8K spectrum do it in less than 30 seconds on a reasonably configured PC. PCGAP also includes a program which allows the operator to manually (using mouse clicks) identify photopeak locations, fit limits and background positions, initiate a fit to the photopeaks and then display the resulting Gaussian function forms. This interactive display function is particularly useful to resolve or properly fit photopeaks with complex adjacent structure and for photopeaks that are near the limit of detection.iv