A stilbene - CdZnTe based radioxenon detection system.

Area of Science:

• Nuclear physics and instrumentation
• Environmental monitoring and detection
• Radiochemistry and nuclear forensics

Background:

• Atmospheric radioxenon monitoring is crucial for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) to detect nuclear events.
• Existing detection systems using plastic scintillators suffer from a significant memory effect, hindering accurate measurements.
• The memory effect can lead to false positives or mask subsequent events, impacting treaty verification.

Purpose of the Study:

• To design and evaluate a novel radioxenon detection system.
• To address the challenge of memory effect in radioxenon detection systems.
• To explore the efficacy of stilbene as a detection medium for radioxenon applications.

Main Methods:

• Development of a new detection system incorporating silicon photomultipliers, a stilbene gas cell, and a CdZnTe detector.
• Evaluation using xenon radioisotope samples produced at Oregon State University's TRIGA reactor.
• Collection of 48-hour background data and Minimum Detectable Concentration (MDC) calculations using the Region of Interest (ROI) approach.

Main Results:

• The new system achieved a Minimum Detectable Concentration (MDC) below 1 mBq/m³ for key radioxenon isotopes (¹³¹mXe, ¹³³Xe, ¹³³mXe), meeting CTBTO sensitivity requirements.
• The stilbene gas cell demonstrated a memory effect of 0.045 ± 0.017% for ¹³¹mXe, a two-order magnitude improvement over plastic scintillators.
• Performance was found to be comparable to existing state-of-the-art radioxenon detection systems.

Conclusions:

• The developed radioxenon detection system effectively minimizes the memory effect using a stilbene gas cell.
• This technology offers a significant improvement for atmospheric monitoring and nuclear event detection.
• The findings support the adoption of stilbene-based detection media for enhanced CTBTO monitoring capabilities.