A stilbene - CdZnTe based radioxenon detection system

Atmospheric monitoring of radioxenon is one of the most widely used methods by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) to detect elevated levels of ^131mXe, ^133/133mXe, and ¹³⁵Xe. The ratios of these radionuclides help discriminate between peaceful use of nuclear technology and nuclear weapon explosions. Radioxenon detection systems often use plastic scintillators in the capacity of an electron detector and a gas cell, plastic gas cells are responsible for introducing high memory effect in these systems. This work presents the design of a new detection system for radioxenon monitoring that utilizes silicon photomultipliers, a stilbene gas cell, and a CdZnTe detector. This detector was evaluated using xenon radioisotope samples produced in the TRIGA reactor at Oregon State University. A 48-h background was collected and calculations of the Minimum Detectable Concentration (MDC) were carried out using the Region of Interest (ROI) approach. An MDC of less than 1 mBq/m³ was obtained for ^131mXe, ¹³³Xe, and ^133mXe in accordance with the sensitivity limits set by the CTBTO and performs respectably when compared to state-of-the-art radioxenon detection systems. Using ^131mXe, this study indicates that the stilbene gas cell exhibits a memory effect of 0.045 ± 0.017%, this is almost a two-order magnitude improvement compared to plastic scintillators. The primary purpose of this work is to explore the use of new stilbene detection media for radioxenon application and addressing the problem of memory effect.