Scanning superconducting quantum interference device microscope in a dilution refrigerator

We report on a scanning superconducting quantum interference device microscope operating at temperatures down to 20 mK in a dilution refrigerator. The instrument is designed for studying quantum mechanical coherence effects in mesoscopic systems and investigating magnetic effects on a mesoscopic length scale in novel materials. We have demonstrated the low-temperature operating capabilities of the instrument by studying superconducting tin disks and the superconducting transition of a thin-film tungsten sample and vortices in the same film. Looking forward, we discuss the applicability of the instrument to measurements of persistent currents in normal-metal rings.