Development of a silicon beta cell for radioxenon detection and the impact to environmental monitoring

Abstract:

Beta gamma detectors are utilized extensively for the detection of radioxenon for nuclear explosion monitoring. Traditional beta-gamma detection of radioxenon often utilizes a plastic scintillator beta cell and NaI gamma detector. Two areas of improvement for plastic scintillators are the sample carry-over (“memory effect”) and energy resolution. While the scintillator can be coated to remove the memory effect, the energy resolution must be improved with a different detector material. Silicon is the current leading candidate for the future beta cell material due to the much-improved energy resolution compared to plastic scintillators (factor of ~3x). PNNL is developing a silicon beta cell for use as a potential modular replacement within Xenon International (a next-generation radioxenon detection system currently undergoing acceptance testing for potential inclusion in the International Monitoring System). The beta cell utilizes four different silicon detectors to create an active volume for the radioxenon within an outer gas cell. Since there are four separate beta signals (compared to 1 for plastic scintillators), data acquisition modifications are required. In this presentation, we detail the advantages that can be achieved through the use of silicon detectors. Additionally, we will discuss design and testing of the silicon beta cell along with potential improvements in beta cell design. We will also discuss the required data acquisition and analysis updates needed to best utilize the silicon improvements to leverage the isotopic discrimination for background identification.