A plastic scintillator and HPGe β-γ coincidence detection system

Area of Science:

• Nuclear physics
• Environmental monitoring
• Analytical chemistry

Background:

• The International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) relies on specialist laboratories for radionuclide sample analysis, including xenon isotopes.
• Xenon fission product radionuclides (¹³³Xe, ¹³⁵Xe, ^131mXe, ^133mXe) are key indicators for detecting underground nuclear explosions.
• Current measurement techniques, such as beta-gamma coincidence spectrometry, offer high sensitivity but face challenges with metastable xenon isomers due to interferences.

Purpose of the Study:

• To evaluate a novel coincidence detector system for enhanced radioxenon measurement.
• To address challenges in detecting metastable xenon isomers (^131mXe, ^133mXe) and reduce interferences.
• To assess the performance of a new detector system for nuclear test monitoring.

Main Methods:

• Development and testing of a coincidence detector system combining a plastic scintillator gas cell and a large-crystal high-purity germanium (HPGe) detector.
• Measurement of synthetic radioxenon gas samples to determine system performance.
• Analysis of energy resolution, coincidence detection efficiency, Minimum Detectable Activity (MDA), and interference factors.

Main Results:

• The new detector system's energy resolution and coincidence detection efficiency were determined.
• Minimum Detectable Activity (MDA) and interference factors were quantified for the radioxenon isotopes.
• The system's performance was evaluated using synthetic radioxenon samples, providing data for further optimization.

Conclusions:

• The developed coincidence detector system shows promise for improving radioxenon detection capabilities.
• This system aims to reduce interferences and enhance the sensitivity of nuclear explosion monitoring.
• Further assessment of detector systems is crucial for advancing radionuclide laboratories supporting the CTBT.