Optimization of etching conditions of CDs/DVDs used as detectors for 222Rn

• The etching regime of CDs/DVDs used as radon detectors is optimized.
• Optimum depth and high voltage for electrochemical etching are obtained.
• The influence of the temperature uncertainty and the high voltage instability on the accuracy is studied.
• The range of the CD/DVD method is expanded by two orders of magnitude.

To use the combination of the high radon absorption ability of the polycarbonate material of CDs/DVDs with its track-etch properties for retrospective radon measurements in dwellings was first proposed in 2001. Since then the applications of this method have expanded significantly, including measurements of high radon concentrations, e.g. in soil gas, underground mines, radon spas and buildings with exceptionally high radon levels. As the method employs electrochemical etching of alpha-tracks at a certain depth beneath the disk surface, saturation at high track density might occur. In this report we explore how the depth at which the alpha-tracks are etched and the voltage applied for electrochemical etching can be varied, in order to expand the range of the method towards high radon concentrations and to achieve the best accuracy. As a result, optimized regimes for etching CDs/DVDs are proposed and the expanded range of the method estimated.