Identification of Pb-210 and Po-210 in the bulk of copper samples with a low-background alpha particle counter

We established a method to assay Pb-210 and Po-210 contaminations in the bulk of copper samples using a low-background alpha particle counter. The achieved sensitivity for the Pb-210 and Po-210 contaminations reaches a few mBq/kg. Due to this high sensitivity, the Pb-210 and Po-210 contaminations in oxygen free copper bulk were identified and measured for the first time. The Pb-210 contaminations of our oxygen free copper samples were 17-40 mBq/kg. Based on our investigation of copper samples in each production step, the (21)0Pb in oxygen free copper was understood to be a small residual of an electrolysis process. This method to measure bulk contaminations of Pb-210 and Po-210 could be applied to other materials.