Preparation of a radon-free thoron source for a thoron calibration chamber

During long-term radon/thoron surveys, solid-state nuclear track detectors (SSNTDs) are commonly used. For the application of these integral devices, it is important to solve the commensurate calibration. At the calibration process, radon can be interfering with thoron; therefore, radon-free thoron atmosphere is required for the accurate calibration. In this study, radon-free thoron source with a high emanation capability was prepared by chemical separation of 228 Ac. Based on the results of this and the previously performed experiments, a method combines precipitation with FeCl 3 and embedding into ceramic matrix containing low feldspar content and heat treatment on 200 °C has been proposed.