Efficiency calibration and self-attenuation correction in radioxenon measurement using β-γ coincidence method

Area of Science:

• Nuclear physics
• Environmental monitoring
• Radiochemistry

Background:

• Radioactive noble gases, specifically xenon isotopes (131mXe, 133mXe, 133Xe, 135Xe), are critical indicators for detecting underground nuclear tests.
• The Comprehensive Nuclear-Test-Ban Treaty (CTBT) relies on precise monitoring of these isotopes.
• Beta-gamma coincidence techniques enhance detection sensitivity but are affected by self-attenuation in gaseous matrices like xenon, nitrogen, and helium.

Purpose of the Study:

• To enhance the accuracy of radioxenon isotope measurements for CTBT compliance.
• To develop and validate methods for correcting self-attenuation effects in gaseous samples.
• To improve the overall sensitivity and reliability of nuclear test monitoring.

Main Methods:

• Detection efficiencies for X-rays and gamma rays were determined using a simulated gas calibration source with a low-density sponge matrix.
• Detection efficiencies for beta particles and conversion electrons (CEs) were calibrated by measuring radioxenon samples.
• Self-attenuation correction factors for X-rays and gamma rays were calculated using the Geant4 simulation method.
• Self-attenuation correction factors for beta particles and CEs were determined by analyzing radioxenon samples of varying volumes and gas compositions (xenon, nitrogen, helium).

Main Results:

• Established accurate methods for deriving detection efficiencies of various radiation types from radioxenon isotopes.
• Quantified self-attenuation correction factors for X-rays, gamma rays, beta particles, and CEs in different gaseous matrices.
• Demonstrated a significant improvement in measurement accuracy by applying these correction factors.

Conclusions:

• The developed methods effectively address self-attenuation in radioxenon measurements, crucial for nuclear test monitoring.
• Accurate quantification of xenon isotopes is achievable even in complex gas mixtures, enhancing CTBT verification capabilities.
• This work provides a robust framework for improving the precision of atmospheric monitoring for nuclear non-proliferation.