Scintillation detectors for Rn222 in air and water.

Reports tests of a scintillation counter to detect Ra 222 in air and water. The counter consists of a spherical cavity coated with ZnS(Ag) powder, built in a lucite cylinder whose external surfaces, excepting the window which is put in contact with a photomultiplier, are made reflective with a special paint. The performance of the detector has been analysed with respect to size,efficiency, background, constant activity and constant concentration in the sample. Finds that for liquid samples, two different values for the diameter, 5 cm. and 7.5 cm. proved to be suitable, one for laboratory measurements and one for field measurements. For air samples, larger sizes appeared suitable even at low natural levels.