Investigating Low-Radioactivity Materials andDisequilibrium in the Uranium Decay Chains inthe Materials for Rare-Event Searches*

Investigating low-radioactivity materials and equilibrium/disequilibrium in ura-

nium decay chains in materials potentially used for rare-event search detectors

can help improve material selection and background control. Hundreds of po-

tential detector materials were assayed for measurement of radioactive contam-

ination using a High-Purity Germanium (HPGe) detector at Soudan Lab and

the Sudbury Neutrino Observatory (SNOLAB) by the Super Cryogenic Dark

Matter Search (SuperCDMS) Collaboration. Utilizing nuclear physics concepts

and machine-learning clustering algorithms, we identify low-radioactivity ma-

terial samples and investigate the equilibrium/disequilibrium in uranium decay

chains in the materials for which the measurements were available. The find-

ings of this study will be used to identify low-radioactivity materials, re-assay

the materials, and investigate the manufacturing processes that produced the

samples. This information will be used to improve the sensitivity of rare-event

search detector projects.