Measurement of the size distribution of radon progeny aerosols using imaging plate

A new method for measuring size distribution of radon progeny aerosols was developed. The radon progeny aerosols collected with a low pressure impactor was measured by using imaging plates (IP) which have high sensitivity and high resolution. An alpha particle that incidence on IP can be observed as a spot on the graphic image. The activity of radon progeny was estimated from the number of these spots on IP. The validity of IP measurement method was confirmed by comparing with a conventional method using a ZnS(Ag) scintillation counter. With this method, the size distribution of thoron progeny aerosols could also be measured. The size distribution of radon progeny aerosols was measured by using three kinds of collecting plates, i.e., stainless steel plates, stainless steel plates coated with grease and fiberglass filters. The results of measurement were different between collecting plates. This may be due to the rebound of aerosols on the surface of collecting plate