Figure 4 - uploaded by Nathan Tomlin
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14: (a) TES X-ray sensor integrated with NIS refrigerators (Bi absorber not shown). Four pairs of NIS refrigerators are located at the corners of a SiNx membrane (dashed outline). Y-shaped cold-ngers extend from the normal-metal of the NIS junctions onto the membrane and surround the TES. (b) False-color SEM image of membrane corner.
Source publication
Many cryogenic devices require temperatures near 100 mK for optimal
performance, such as thin-film, superconducting detectors. Examples
include the submillimeter SCUBA camera on the James Clerk Maxwell
Telescope, high-resolution X-ray sensors for semiconductor defect
analysis, and a planned satellite to search for polarization in the
cosmic microwa...
Citations
... where negative power means that the heat is taken out from the Normal metal. If we calculate the heat deposited in the superconductor, we find that: [46] Comparing to the N 1 − I − N 2 case, the electrical work supplied enables one to extract selectively high-energy quasi-particles out of the normal metal and deposit them in the superconductor as quasi-particle excitations (for V ∆ e ). The removal of those hot electrons cools the metal electrode in a manner analogous to cooling a cup of coffee by evaporation [60]. ...
... Although Pekola et al. tried to use mecanical masks [59], presenting a higher distance between the mask and the substrate, to obtain larger tunnel junctions. Researchers succeed in suspending a normal metal beam with tunnel junctions [49,37,47,48,46], the results are impressive but not a convincing solution to improve significatively electronic refrigeration with tunnel junction. We have devised a process to increase the size of junctions without increasing the surface between the copper and the wafer is called the over-etching technique. ...
Electronic cooling in Superconductor - Insulator - Normal metal (S-I-N) junction is based on the energy selectivity of electron tunneling induced by the superconductor energy gap. Nevertheless, the efficiency of coolers based on such junctions is usually significantly less than theoretically expected. After introducing the principle of superconducting micro-coolers, we present the fundamental limitations to electronic cooling. We focus on the different thermal couplings between electron and phonon thermal baths and the relaxation of hot quasi-particles deposited in the superconductor. We have designed an experiment to monitor independently electron and phonon temperatures. An electronic cooler was studied under out-of-equilibrium conditions, in both the cooling and the heating regimes. The results are interpreted using a thermal model, which takes into account the heat transfers between the electron, phonon and photon baths. In particular, the photonic heat flow related to the thermal noise arising in the circuit resistors can bring an additional heat contribution, depending on the transmission of the biasing circuit. Moreover, we investigate the enhancement of quasi-particles relaxation under magnetic field, leading to an enhanced quasi-particle relaxation. Finally we develop a process enabling to fabricate a S-I-N-I-S cooler with large junctions and a suspended Normal metal island decoupled from the substrate.
