Cosmogenic Background Characterization for the Colorado Underground Research Institute (CURIE)

Cosmogenic particles produced in Earth's atmosphere present a dominant background in many experiments and equipment benchmarking efforts, especially for those requiring high levels of sensitivity. For such experiments and equipment testing, underground research facilities are an essential asset. These facilities are sought after due to the rock overburden which provides natural protection from ionizing cosmogenic radiation, such as the near-elimination of cosmogenic muons. Understanding the remaining cosmogenic backgrounds at these facilities is key in properly designing, developing, and analyzing experiments. For instance, ionizing radiation interacting with superconducting devices—such as qubits—leads to a burst of athermal phonons, consequently increasing the Bogoliubov quasiparticle population near Josephson junctions. These effects introduce correlated errors in both space and time in qubit arrays. One way to characterize and address this issue is to move to shallow underground facilities. In this talk, we present the cosmogenic muon background characterization for the new Colorado Underground Research InstitutE (CURIE) located in the Edgar Experimental Mine in Idaho Springs, CO. Our analysis yields an equivalent overburden of 415 meter-water-equivalent (m.w.e.), and a factor of 700x reduction compared to the sea-level muon flux. We also discuss the current status and ongoing efforts to fully characterize all expected sources of background radiation.