Response of AlphaGUARD PQ2000 radon detector to 220Rn in diffusion mode

Background222Rn/220Rn and their daughters are widely present in the atmosphere and indoor environment. The presence of high-concentration 220Rn can affect the accuracy of 222Rn concentration measurements.PurposeThis study aims to measure radon concentration more accurately by investigating the variation in the response coefficients of the AlphaGUARD PQ2000 radon monitor to 220Rn under thoron gas concentrations with different wind speeds and directions within a standard radon chamber.MethodsThe single-scintillation proportional counter flow gas static method was employed to determine the thoron concentration in this study. Firstly, a self-made and stable high emissivity solid 220Rn source at the University of South China was applied to the generation of 220Rn gas in the chamber, a temperature and humidity control system was adopted to regulate the inside temperature and humidity of 220Rn whilst the wind speed was controlled by changing the operating frequency of the variable frequency fan. Then, the readings of the AlphaGUARD PQ2000 were observed at various wind speeds and directions under controlled temperature and humidity conditions. Subsequently, the response coefficients of the AlphaGUARD PQ2000 to thoron in diffusion mode were calculated according the observed results.ResultsWhen the wind speed increases from 0.05 m·s-1 to 3.50 m·s-1, the response coefficient of AlphaGUARD PQ2000 to 220Rn increases from 0.044 to 0.126. When there is no wind, the response coefficient is 0.049. When the wind speed is fixed at 0.71 m·s-1 and the angle between the wind direction and AlphaGUARD PQ2000 diffusion window changes from 0° to 180°, the response coefficient decreases from 0.083 to 0.051. When the wind speed is fixed at 1.43 m·s-1 and the angle between the wind direction and AlphaGUARD PQ2000 diffusion window changed from 0° to 180°, the response coefficient is reduced from 0.115 to 0.081.ConclusionsThe response coefficients obtained in this study can provide a reference for correcting the interference of 220Rn in the measurement results of the diffusion mode of the AlphaGUARD PQ2000 radon detector.