Exploring the Effect of Environmental Factors on Radon Plate-out

Radon is an inert, radioactive gas that occurs naturally and disperses quickly. As it decays, the resulting daughters can “plate out” (stick) on surfaces, which can contaminate important components in dark matter experiments. Subsequent decays can create backgrounds that mimic signals, so it is imperative to minimize the amount of radon that plates out. To conduct studies on radon plate-out, a Pylon RN-1025 flow-through source was used to create a calibrated radon environment. These studies showed a rational relationship between airflow through the source and radon concentration in the exposure chamber. A flow of 4 SCFH through the source was found to be the optimal flow to use for plate-out tests as it provided a high equilibrium concentration of 1270-1390 Bq/m3 while still overpressuring the system. Initial tests have shown an activity of roughly 0.044±0.002 Bq after correcting for detector efficiency. However, additional trials and calculations are needed for confirmation. Future tests will be performed to determine the effect of wind speeds on the radon plate-out efficiency.