A new idea for a solid-state microrefrigerator operating near 100 mK

We propose a new design for solid-state microrefrigerator based on Normal-I nsulator-Superconductor (NIS) tunnel junctions. These devices are a promisi ng means of providing continuous refrigeration from 0.3 to 0.1 K without vi bration or moving parts. Previously, the area and cooling power of NIS refr igerators have been limited by heating of the superconducting electrode. Th is problem can be overcome by using a superconducting single crystal as bot h the substrate and superconducting electrode of the NIS junction. In this paper, we briefly explain the benefits of our new design and describe exper imental progress towards building such a device.