Improvements in the absolute standardization of large-area reference sources

Area of Science:

• Nuclear instrumentation
• Metrology
• Radiation detection

Background:

• Gas-flow proportional counters are crucial for radioactivity measurements.
• Accurate standardization of large-area reference sources requires understanding counter sensitivity to environmental factors.
• Variations in applied voltage, gas purity, flow rate, pressure, and temperature can impact measurement precision.

Purpose of the Study:

• To analyze the efficiency sensitivity of gas-flow proportional counters to key influence quantities.
• To apply this analysis for the absolute standardization of large-area reference sources.
• To improve measurement accuracy and reproducibility through optimized counter operation and gain stabilization.

Main Methods:

• Developed a simple gas-gain model to analyze counter efficiency sensitivity.
• Evaluated measurement uncertainty by considering fluctuations in applied anode voltage, gas purity, gas-flow rate, ambient pressure, and temperature.
• Implemented a cleaning procedure and a gain stabilization technique for the counters.

Main Results:

• Measurement uncertainty was found to be small under normal operating conditions.
• Accidental or large changes in influence quantities can lead to significant measurement errors.
• The implemented procedures resulted in measurement uncertainties below 0.55% and reproducibility better than 0.42%.

Conclusions:

• The gas-gain model effectively predicts counter behavior and aids in standardization.
• Optimized operating conditions and gain stabilization are essential for high-accuracy measurements with gas-flow proportional counters.
• The developed methods significantly enhance the absolute standardization of large-area reference sources.