Lead-210 in SuperCDMS Copper

High-purity copper is an important structural material for the Super Cryogenic Dark Matter Search (SuperCDMS) at SNOLAB; it will be used to fabricate low-background detector housings for each of the experiment's germanium and silicon crystals, as well as a large cryostat. Owing to the high chemical purity available with commercially produced copper, specific activities of radiocontaminants (e.g. U and Th isotopes) in the bulk copper material are generally modest. However, recent studies have demonstrated surprisingly high levels of Pb-210 in the bulk material, far out of secular equilibrium with the U-238 parent. Further, exposure to atmospheric radon can result in radon daughters plating out onto the surfaces of fabricated copper parts, ultimately leading to the implantation of Pb-210. I will describe experiments performed to test copper-surface treatments, together with low-level radiopurity assay measurements, to assess Pb-210 mitigation effectiveness and to directly verify Pb-210 levels for the copper that SuperCDMS SNOLAB will use in its detector payload.