A Hybrid Dilution Refrigerator as a Platform for Low-Vibration Quantum Imaging

Noise resulting from vibrations between a probe and a sample are oftentimes the leading source of error in microscopies using ultra-high precision probes, such as scanning SQUID microscopy. In our Bluefors LD250 dilution refrigerator, we have installed a helium battery that enables a hybrid cooling mode, in which cooling is possible for 2-4 hours without operation of the typical, vibration-causing pulse tube. We present here vibrational noise analysis using scanning SQUID images of local magnetic field sources and compare the vibrations in the normal cooling mode and the hybrid cooling mode. Our showcasing of specific material studies demonstrates the advantage of the new approach for quantum imaging at ultra-low temperatures.