An inexpensive radon scintillation cell

The modified cell described is made up of 6 separate parts which can be assembled or dismantled easily and are standardised for interchangeability. The volume is 150 cm3. The phosphor coating is on a silicone grease base. Before sampling the cell is evacuated through a hypodermic needle through a rubber stopper. Sampling is done through a filter holder with a similar needle. Decoupling of the cell from the counting system automatically cuts off the high voltage supply to the photomultiplier. No separate enclosure is required to shield against background light. Counting efficiency (76.1 +- 1.1%) does not change with time and use. Sensitivity of the cell is shown as a function of background count rate and counting duration. A 10 min. counting duration is adequate for routine monitoring in U mines. The cell is light and sturdy and costs less than US$12. (U.K.)