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

We propose a new design for a solid-state microrefrigerator based on Normal-Insulator-Superconductor (NIS) tunnel junctions. These devices are a promising means of providing continuous refrigeration from 0.3 to 0.1 K without vibration or moving parts. Previously, the area and cooling power of NIS refrigerators have been limited by heating of the superconducting electrode. This problem can be overcome by using a superconducting single crystal as both the substrate and superconducting electrode of the NIS junction. In this paper, we briefly explain the benefits of our new design and describe experimental progress towards building such a device.