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arXiv · 1702.06425

Magnetic cooling for microkelvin nanoelectronics on a cryofree platform

Mario Palma·Dario Maradan·Lucas Casparis·Tai-Min Liu·Florian Froning·Dominik M. Zumbühl
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Abstract

We present a parallel network of 16 demagnetization refrigerators mounted on a cryofree dilution refrigerator aimed to cool nanoelectronic devices to sub-millikelvin temperatures. To measure the refrigerator temperature, the thermal motion of electrons in a Ag wire -- thermalized by a spot-weld to one of the Cu nuclear refrigerators -- is inductively picked-up by a superconducting gradiometer and amplified by a SQUID mounted at 4 K. The noise thermometer as well as other thermometers are used to characterize the performance of the system, finding magnetic field independent heat-leaks of a few nW/mol, cold times of several days below 1 mK, and a lowest temperature of 150 microK of one of the nuclear stages in a final field of 80 mT, close to the intrinsic SQUID noise of about 100 microK. A simple thermal model of the system capturing the nuclear refrigerator, heat leaks, as well as thermal and Korringa links describes the main features very well, including rather high refrigerator efficiencies typically above 80%.

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Mario Palma, Dario Maradan, Lucas Casparis, Tai-Min Liu, Florian Froning, Dominik M. Zumbühl. 2017-02-21. Magnetic cooling for microkelvin nanoelectronics on a cryofree platform. https://doi.org/10.1063/1.4979929

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