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

Abstract

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

6 pages, 8 figures