Characterization of Phoswich Well Detectors for Radioxenon Monitoring

Devices to measure the amount of radioactive xenon in the atmosphere have been installed in several locations around the world as part of the International Monitoring System to detect nuclear weapons testing. These devices extract small samples of xenon from large volumes of air and look for characteristic radioxenon isotopes emitting beta and gamma radiation in coincidence. To detect these coincidences, they currently employ a complex system of separate beta and gamma detectors which is very sensitive, but which requires careful calibration and gain matching of several detectors and photomultiplier tubes to achieve desired detection limits. An alternative to separate beta and gamma detectors is the use of a single phoswich detector in which beta-gamma coincidences are detected by pulse shape analysis. The phoswich detector consists of a plastic scintillator (absorbing betas) optically coupled to a CsI(Tl) scintillator (absorbing gammas) and thus requires only a single photomultiplier tube and electronics readout channel, greatly simplifying setup and calibration. In this paper, we present the results from an experimental evaluation of two phoswich well detector prototypes, including energy resolution, 2 D beta/gamma energy histograms from a variety of test sources, and background count rates. From these measurements, we derive detector properties such as coincidence detection efficiency, background rejection and the ability to separate beta only, gamma only, and coincidence events. We will further discuss setup and calibration procedures and compare them to those for existing detector systems.
Related Articles
Network Time Synchronization of the Readout Electronics for a New Radioactive Gas Detection System
In systems with multiple radiation detectors, time synchronization of the data collected from different detectors is essential to reconstruct multidetector events such as scattering and coincidences. In cases where the number of detectors exceeds the readout channels...
Electronics Upgrades to the Green Is Clean Phoswich Detector Systems and Programmatic Implementation at LANL – Phase II Completion – 18403
Los Alamos National Laboratory (LANL) radiological facilities produce low-density room trash that, in many cases, is not contaminated with radioactivity. It has been estimated that 50 to 90% of low-density room trash is free of radioactive contamination and eligible...
New Algorithms for Improved Digital Pulse Arrival Timing With Sub-GSps ADCs
The ability to measure pulse times of arrival with resolutions at or below 100 ps is becoming increasingly desirable in various fields, typically for signals originating from photon detectors such as photomultiplier tubes (PMTs) or silicon photo-multipliers. Achieving...