Characterization of Cryogenic Material Properties of 3-D-Printed Superconducting Niobium Using a 3-D Lumped Element Microwave Cavity

We present an experimental characterization of the electrical properties of 3-D-printed niobium. The study was performed by inserting a 3-D-printed Nb post inside an aluminum cylindrical cavity, forming a 3-D lumped element reentrant microwave cavity resonator. The resonator was cooled to temperatures below the critical temperature of niobium (9.25 K) and then aluminum (1.2 K) while measuring the quality factors of the electromagnetic resonances. This was then compared with finite element analysis of the cavity and a measurement of the same cavity with an aluminum post of similar dimensions and frequency, to extract the surface resistance of the niobium post. The 3-D-printed niobium exhibited a transition to the superconducting state below 9.25 K, as well as a surface resistance of 3.1 ± 0.54 × 10-4 Ω. This value was comparable to many samples of traditionally machined niobium previously studied without specialized surface treatment. Furthermore, this study demonstrates a simple new method for characterizing the material properties of a relatively small and geometrically simple sample of the superconductor, which could be easily applied to other materials, particularly 3-D-printed materials. Further research and development in additive manufacturing may see the application of 3-D-printed niobium in not only superconducting cavity designs but also in the innovative technology of the future.