Next Generation Detection Systems for Radioactive Material Analysis

Abstract

Compton Suppression techniques have been widely used to reduce the Minimum Detectable Activity of various radionuclides when performing gamma spectroscopy of environmental samples. This is achieved by utilising multiple detectors to reduce the contribution of photons that Compton Scatter out the detector crystal, only partially depositing their energy. Photons that are Compton Scattered out of the primary detector are captured by a surrounding detector, and the corresponding events vetoed from the final dataset using coincidence based fast-timing electronics. The current work presents the use of a LynxTM data acquisition module from Canberra Industries (USA) to collect data in 'List-Mode', where each event is time stamped for offline analysis. A post-processor developed to analyse such datasets allows the optimisation of the coincidence delay, and then identifies and suppresses events within this time window. This is the same process used in conventional systems with fast-timing electronics, however, in the work presented, data can be re-analysed using multiple time and energy windows. All data is also preserved and recorded (in traditional systems, coincident events are lost as they are vetoed in real time), and the results are achieved with a greatly simplified experimental setup. Monte-Carlo simulations of Compton Suppression systems have been completed to support the optimisation work, and are also presented here.