Alpha-recoil implantation probability in a glass surface from the decay of deposited polonium-218

In the indoor environment short-lived radon decay products deposit onto surfaces. Alpha decaying atoms obtain recoil energy enough to implant into the substrate. This hideaway phenomenon permits the use of implanted long-lived radon decay products as a measure of past radon exposures. Specifically flat glass surfaces has been used as radon retrospective monitors and thanks to the development of special track-etch devices (retro detectors) the implanted surface activity can be measured in-situ. In parallel with the use of these retro detectors in epidemiological studies, we have studied basic aspects of the alpha recoil process into glass surfaces during fully controlled conditions, a control that is not possible during authentic living conditions in a house. By radon exposures in a small wind-tunnel of volume 17 litres and large-area alpha spectrometry by means of a pulse ionization chamber, implantation of short-lived radon decay products during both
aerosol and non-aerosol conditions has been studied. In order to separate loosely attached surface activity from physically implanted activity, different cleaning regimes in between exposure and measurement have been applied. The preliminary results from these tests are that Pb-214, Bi-214 and Po-214 behaves differently against cleaning agents and that the surface activity can be categorized into three different groups, loosely attached activity, chemically bound activity and physically implanted activity. The implication of these findings on the use of glass sheets for radon epidemiological studies will be discussed.