Speaker
Description
This study optimizes the performance of a stainless-steel, 2π windowless large-area multi-wire proportional counter at the National Ionizing Radiation Standard Laboratory (NRSL) in Taiwan. Featuring a 100 mm× 150 mm effective area and a NIM-standard analog processing chain, the system utilizes P-10 gas for particle detection via ionization and charge multiplication. By employing absolute measurement techniques, the apparatus ensures metrological consistency with ISO 8769 and facilitates the precise traceability transfer of surface emission rates.
The implementation of dynamic flow equilibrium combined with real-time barometric compensation ensures an ultra-stable analog measurement environment, mitigating environmental perturbations. A custom high-precision flow meter regulates the P-10 flow field to purge electronegative impurities, alleviating pulse degradation and substantially boosting the SNR. Concurrently, a water-sealed bubble meter and a digital monitoring interface stabilize the chamber pressure at a constant 1 atm. This setup neutralizes atmospheric interference on gas gain, curtailing the uncertainty associated with voltage settings to 0.04%. For low-energy beta emitters like C-14, this precise pressure regulation prevents gain shifts, preserving the total measurement uncertainty within a stringent 0.6% (k=2). Furthermore, optimal impedance matching and 5.9 keV peak calibration guarantee a minimized plateau slope (< 0.5% / 100 V) and superior low-energy noise discrimination.
Empirical evaluations demonstrate that measurement deviations for Am-241 and Sr-90/Y-90 standard sources are consistently sustained within 1.0% relative to reference values. A comprehensive analysis of long-term monitoring data yields a combined stability of 0.25%, substantiating exceptional metrological equivalence. The system establishes a robust and comprehensive traceability chain that secures the technical consistency of national radiation monitoring, affirming full synchronization with international metrological and safety standards.
Keywords: 2π windowless large-area multi-wire proportional counter; dynamic flow equilibrium; real-time barometric compensation; water-sealed bubble meter