Passive dosimeter for detection of radon, thoron and daughters thereof

Abstract

In a passive dosimeter for the detection of radon and/or thoron and their daughters and including a diffusion chamber having two end faces, a first radioactive decay detector composed of a nuclear track detector foil or an integrating .alpha.-detector sealing one end face of the chamber, and a filter transmissive for radon and/or thoron, whereby the detector provides an indication of radon and thoron decay and the resultant daughters, there is further provided a second chamber corresponding in structure to the diffusion chamber and having two end faces, with one end face of the second chamber being sealed by the side of the filter directed away from the diffusion chamber, and a second radioactive decay detector substantially identical to the first detector sealing the other end face of the second chamber, with passages being provided between the second chamber and the environment of the dosimeter for passage of gas with radon and thoron and daughters to be measured into the second chamber. When the detector is a nuclear track detector foil, selected levels of the energy of .alpha.-particles impinging on the foil during exposure to such particles can be identified by first chemically pre-etching the foil for removing a layer of foil material to a depth corresponding to a selected .alpha.-particle energy level, and then performing an electrochemical etching operation on the foil for rendering the .alpha.-particle impingement tracks in the foil visible.