A compact Rn-220 reference chamber with constant temperature and humidity

A novel compact Rn-220 reference chamber with stable temperature and humidity control was successfully designed and developed to support radiation-related experimental studies. The device consists of a 200 L cylindrical sealed chamber made of 304 stainless-steel, providing excellent airtightness and corrosion resistance. Concentration levels inside the chamber were tested using both 36 and 9 thorium doped lantern mantles as radioactive sources. A tray containing iodine-free supersaturated salt solution was placed at the bottom to regulate humidity, while a fan positioned at the top ensured adequate air mixing at a circulation rate of 12 m³ min^-1. Experimental results indicated that the system could maintain a relative humidity of 73 ± 3%, while the temperature was stabilized at 31 ± 1 °C by an external air-conditioning system. Multi-point monitoring using a RAD7 radon detector indicated that the overall Rn-220 concentrations reached 166,700 ± 35,300 Bq m^-3 and 47,700 ± 12,400 Bq m^-3. The uncertainty of the 9 thorium doped lantern mantles configuration was 26.0%. Given the small vertical concentration difference across three heights with 9 thorium doped lantern mantles, this configuration was selected as the reference Rn-220 source. This compact Rn-220 reference chamber has potential applicability in instrument calibration and radiation-related studies.