MONTE-CARLO SIMULATIONS OF LOW-BACKGROUND DETECTORS

An implementation of the Electron Gamma Shower 4 code (EGS4)(1) has be en developed to allow convenient simulation of typical gamma ray measu rement systems. Coincidence gamma rays, beta spectra, and angular corr elations have been added to adequately simulate a complete nuclear dec ay and provide corrections to experimentally determined detector effic iencies. This code has been used to strip certain low-background spect ra for the purpose of extremely low-level assay. Monte Carlo calculati ons of this sort can be extremely successful since low background dete ctors are usually free of significant contributions from poorly locali zed radiation sources, such as cosmic muons, secondary cosmic neutrons , and radioactive construction or shielding materials. Previously, val idation of this code has been obtained from a series of comparisons be tween measurements and blind calculations(2). An example of the applic ation of this code to an exceedingly low background spectrum stripping will be presented.