Cryogenics

Summary

Low temperatures suppress noise and make quantum phenomena accessible. As a result, cryogenics play a crucial role in precision measurements.

Description

Micrograph showing thin-film payload (orange) cooled by four pairs of tunnel junctions located at each corner of the payload.

Almost all the devices developed by the Quantum Sensors Group work at temperatures below liquid helium (4 Kelvin at the elevation of Boulder Colorado). Sometimes, it is necessary to develop specialized cryogenics to test the devices, or to facilitate their dissemination to outside users. The Quantum Sensors Group designs and builds a wide range of refrigerators. Some of the refrigerators are macroscopic and others are thin film circuitry based on the quantum tunneling of electrons through thin insulating barriers.

Major Accomplishments

Compact, extremely low power cryocooler capable of refrigeration from 300 K to temperatures below 2K.

• In the 1990s, development and commercialization of two-stage adiabatic demagnetization refrigerators precooled by liquid nitrogen and helium.  These refrigerators played an important role in the development of TES detectors because they allowed rapid testing of prototype devices. Some of this work is described in Wollman, D. A. et al, Journal of Microscopy 188 (3), 196-223 (1997).
• In the 2000s, development and commercialization of two-stage adiabatic demagnetization refrigerators precooled by pulse tube cryocoolers. These refrigerators are now widely used outside NIST.  They have played an important role in the spread of cryogenic sensors outside low temperature laboratories because of their robustness and ease-of-use. Some of this work is described in Bennett, D. A. et al, Review of Scientific Instruments 83, 093113 (2012).
• In the 2010s, development and commercialization of single-stage adiabatic demagnetization refrigerators precooled by helium-3 sorption units and pulse tube cryocoolers.  These refrigerators are compatible with larger sensor assemblies and the coaxial cabling needed for emerging microwave readout techniques.
• Development of on-chip, solid-state refrigerators based on quantum tunneling through Normal-Insulator-Superconductor (NIS) tunnel junctions. NIST invented NIS refrigerators in 1994 and continues to pursue this unusual technology. Past milestones include achieving useful temperature reductions and cooling powers in one device and the cooling of a transition-edge sensor x-ray detector. Refrigeration of a macroscopic copper stage is described in Zhang, X. Physical Review Applied 4, 024006 (2015).
• Development of a compact, three-stage pulse tube cryocooler capable of reaching temperatures below 10K.
• Development of a compact, extremely low power cryocooler capable of reaching temperatures below 2K based on a three-stage pulse tube and a helium-4 Joule-Thomson loop. This work is described in Kotsubo, V. et al, IEEE Transactions on Applied Superconductivity 27, 9500405 (2017).