Characterization of a low background counting facility at the Kimballton Underground Research Facility

We report on the characterization of a new low-background counting setup at the Kimballton Underground Research Facility in Virginia. The facility consists of a shielded, high-purity germanium detector deployed at a depth of approximately 300 meters water equivalent and equipped with a muon veto system. Exploiting gamma ray spectroscopy in a low cosmic-ray flux environment the facility can be used to screen materials for applications in low-background experiments, such as neutrinoless double-beta decay or dark matter searches. We present the efficiency of the detector calculated using a GEANT4 simulation, and the sensitivity to isotopes of common interest — $^{238}$U, $^{232}$Th and $^{40}$K. As the background goals in next-generation rare decay searches become ever-more stringent, high-sensitivity radiopurity screening facilities will continue to play an important role supporting this science.