Rohan T. Kapur, Pauli Kehayias, Sergey K. Tolpygo, A. Libson, George Haldeman, Collin N. Muniz, Alex Wynn, Nathaniel O’Connor, Neel Parmar, Ryan B. Johnson, Andrew C. Maccabe, John Cummings, Justin Mallek, Danielle Braje, Jennifer M. Schloss
Magnetic flux trapping is a significant hurdle limiting the reliability and scalability of superconducting electronics, yet tools for imaging flux vortices remain slow or insensitive. We present a cryogenic widefield NV-diamond magnetic microscope capable of rapid, micrometer-scale imaging of flux trapping in superconducting devices. Using this technique, we measure vortex expulsion fields in Nb thin films and patterned strips, revealing a crossover in expulsion behavior between $10$ and $20~μ$m strip widths. The observed scaling agrees with theoretical models and suggests the influence of film defects on vortex expulsion dynamics. This instrument enables high-throughput magnetic characterization of superconducting materials and circuits, providing new insight for flux mitigation strategies in scalable superconducting electronics.