Microwave Characterization of Gamma Ray Irradiated Thin Film Embedded and Non-embedded Nb Resonators

Abstract Gamma radiation effects on superconducting microwave transmission line structures, which may find use in future radiation challenging environments, such as satellites or accelerators have been investigated. Two versions of weakly coupled through-type Nb microstrip transmission line resonator material stack-ups were explored. In one version, the Nb signal trace was encapsulated with 20 µm of HD-4110 and in the other version the top Nb was not encapsulated. Exposure of the resonators to gamma radiation was performed for 28 days at room temperature in a sealed vacuum chamber using Co-60 as the gamma radiation source. The quality factors of the resonators were extracted at various cryogenic temperatures below the critical temperature of Nb and resonant frequencies up to 20 GHz. A large dose of gamma radiation used in this work showed a small change in the Nb superconducting properties.