A PRELIMINARY INVESTIGATION FOR THE USE OF DIGITAL GAMMA-GAMMA COINCIDENCE SPECTROMETRY TO DETECT ²³⁹Pu

Abstract

Gamma-ray spectrometry is one of the most effective ways to determine the activity of 239 Pu, depending on activity levels. However, often high backgrounds in complex spectra with low amounts of 239 Pu can increase detection limits. The effectiveness of the use of gamma-gamma spectrometry in the characterization of 239 Pu is studied for the first time. Using the XIA Pixie-16 digital pulse processor, gamma-gamma coincidences were measured to study the unshielded background radiation as a function of the source to detector distance, and gating of several gamma-rays from 239 Pu. The Poisson distribution of the acquired pulses has been also verified. In addition, measurements demonstrated that the background radiation is strongly reduced, meaning gamma-gamma spectroscopy can be very effective to avoid the usual lead shielding. Other measurements were taken to assure Poisson statistics were attained in the digital system. Preliminary measurements revealed 3 orders of magnitude background reduction for the measurement of 239 Pu using gated gamma-rays.