EXPERIMENTAL-DETERMINATION OF THE ALPHA-ENERGY WINDOW IN MAKROFOL ETCHED TRACK DETECTORS FOR THE SEPARATE MEASUREMENT OF THE RADON DECAY PRODUCT PO-214 IN AIR

The measurement of the ratio of the alpha activity concentrations of P o-214 and Rn-222 in air has been found to be a suitable method for est imating a mean equilibrium factor after long-term irradiation periods. Rn-222 can be measured, for instance, by means of an alpha sensitive detector within a diffusion chamber. In order to detect the alpha part icles emitted by Po-214 in air, a detector is needed which is sensitiv e only within an alpha energy window between 6.1 and 7.5 MeV. Using Ma krofol-DE etched track detectors such an energy window can be produced by a suitably selected etching regime consisting of a chemical pre-et ching and a subsequent electrochemical etching. The present paper desc ribes the variation and optimisation of the etching parameters with th e aim of generating an alpha energy window within the given alpha ener gy thresholds. In a first test detectors have been exposed in a radon atmosphere with known activity concentration of Po-214.