Record electron self-cooling in cold-electron bolometers with a hybrid superconductor-ferromagnetic nanoabsorber and traps

A V Gordeeva,A L Pankratov,A V Blagodatkin,D A Pimanov,L S Kuzmin,V O Zbrozhek,N G Pugach,A S Vasenko

doi:10.1038/s41598-020-78869-z

Abstract

The Cosmic Microwave Background (CMB) radiation is the only observable that allows studying the earliest stage of the Universe. Radioastronomy instruments for CMB investigation require low working temperatures around 100 mK to get the necessary sensitivity. On-chip electron cooling of receivers is a pathway for future space missions due to problems of dilution fridges at low gravity. Here, we demonstrate experimentally that in a Cold-Electron Bolometer (CEB) a theoretical limit of electron cooling down to 65 mK from phonon temperature of 300 mK can be reached. It is possible due to effective withdrawing of hot electrons from the tunnel barrier by double stock, special traps and suppression of Andreev Joule heating in hybrid Al/Fe normal nanoabsorber.

Highlights

The Cosmic Microwave Background (CMB) radiation is the only observable that allows studying the earliest stage of the Universe
Several models predict that the primordial gravitational waves can be detected in the form of a polarized signal in the CMB, the so-called “B-modes”, which have magnitude much below 0.1 μK
An alternative approach, motivated by the widespread use of 300 mK range 3 He cryostats for space applications, is an on-chip electron cooling of receivers using NIS (Normal metal–Insulator–Superconductor) tunnel junctions[10]

Summary

Introduction

The Cosmic Microwave Background (CMB) radiation is the only observable that allows studying the earliest stage of the Universe. We can measure the temperature and polarization of the photons generated about 370,000 years after the Big Bang (which corresponds to the cosmological red shift Z = 103 ) with high precision These photons might have imprints from even earlier times, left by the primordial gravitational waves when the Universe was about 10−37 s old[1,2,3]. To achieve the required sensitivity, radioastronomy instruments must be cooled below 100 mK4–6 Such temperatures are a serious challenge for space applications since the conventional closed-cycle dilution refrigerators require gravity for their operation. The open-cycle dilution refrigerator (OCDR) aboard the Planck s atellite[7] operated in zero gravity by ejecting the 3He/4He mixture into space The lifetime of this OCDR with 0.1 μW of cooling power at 100 mK was about two years. The electron and phonon subsystems can co-exist with different but well-defined temperatures

Methods

Findings

Conclusion