Alpha particle emission from reference glass surfaces implanted with 210Po

Implanted long-lived radon decay products in glass surfaces have been used as a measure of past radon exposure in homes. Special track-etch devices (so-called 'retro-detectors') attached to the glass surface, have the ability to specifically measure the implanted activity of 210Po in situ. Calibrating these devices for 210Po is fairly straightforward, but the retro-detectors are also sensitive to the background activity of the glass substrate. Thus, for the successful calibration of retro-detectors, it is necessary to determine the complete alpha emission energy spectrum of the reference glass sheet utilised as a calibration pad. In order to achieve accurate knowledge of the alpha surface emission rate, we have combined several different approaches, i.e. alpha spectrometry of the pad surface with both surface-barrier and pulse-ionisation detectors, and activity determination of the glass matrix by means of radiochemical methods. The part of the alpha emission spectrum originating from the glass volume is then calculated theoretically and compared with experimental results.