Cryogenic detectors are extremely sensitive and have a wide variety of applications (particularly in astronomy), but are difficult to integrate into large arrays like a modern CCD (charge-coupled device) camera. As current detectors of the cosmic microwave background (CMB) already have sensitivities comparable to the noise arising from the random arrival of CMB photons, the further gains in sensitivity needed to probe the very early Universe will have to arise from large arrays. A similar situation is encountered at other wavelengths. Single-pixel X-ray detectors now have a resolving power of ΔE < 5 eV for single 6-keV photons, and future X-ray astronomy missions anticipate the need for 1,000-pixel arrays. Here we report the demonstration of a superconducting detector that is easily fabricated and can readily be incorporated into such an array. Its sensitivity is already within an order of magnitude of that needed for CMB observations, and its energy resolution is similarly close to the targets required for future X-ray astronomy missions.

A broadband superconducting detector suitable for use in large arrays

Superconducting detectors will play an increasingly significant role in astrophysics, especially at millimeter through far-IR wavelengths, where the scientific opportunities include key problems in astronomy and cosmology. Superconducting detectors offer many benefits: outstanding sensitivity, lithographic fabrication, and large array sizes, especially through the recent development of multiplexing techniques. This paper describes the scientific opportunities, the basic physics of these devices, the techniques for radiation coupling, and reviews the recent progress in direct detectors, such as transition-edge bolometers, and the work on tunnel junction (superconductor-insulator-superconductor) and hot-electron mixers.

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Superconducting detectors and mixers for millimeter and submillimeter astrophysics

Quasiparticle trapping in a superconductive detector system exhibiting high energy and position resolution

▪ Abstract The need for very good energy resolution in experiments in particle and astroparticle physics and the need to detect very small energy depositions are the major motivations for the development of low-temperature particle detectors. Because the energy quanta associated with superconductors and lattice vibrations (phonons) are more than one hundred times smaller, substantial improvements have been obtained in energy resolution and in sensitivity over conventional detectors. Furthermore, these detection schemes permit tailoring of target or absorber materials to match the physics requirements. In this article, the basic physics principles behind various methods of detecting excitations induced by particle interactions in bulk single-crystal materials at low temperatures are reviewed. We also present an overview of progress toward implementation of particle physics experiments, such as detection of low-energy neutrinos, search for dark-matter particles, search for neutrino-less double β decay, and ...

Low-temperature particle detectors

In a superconducting detector, the energy resolution is expected to be superior than in a semiconductor detector, owing to the thousand times smaller energy gap Δ. The performance of Sn/Sn‐oxide/Sn tunneling junctions (operated in the Giaever mode at T=0.32 K) exposed to 6‐keV x‐ray photons of a 55Fe source is presented. The best energy resolution observed is 67 eV (FWHM). Extrapolating to vanishing electronic noise, an intrinsic resolution of 0.7% (FWHM) is obtained. This is an order of magnitude worse than expected from the statistics of the 2.5×106 primary electron charges produced, and is believed to be due to geometrical effects in the films. The energy response of the detector is nonlinear, owing to the self‐recombination of the free charge carriers. At a fixed bias voltage, the pulses generated in either film of the junction were observed to have the same sign. If the junctions are evaporated onto a silicon substrate, most of the pulses originate, via phonon backscattering, from x‐ray photons inter...

Superconducting Sn/Sn-oxide/Sn tunneling junctions as high-resolution x-ray detectors

Thin-film superconducting tunnel junctions (Sn/SnOx/Sn) operated at a temperature of 0.3 K were irradiated by a 55Fe X-ray source. Pulses due to photo-absorption in the devices were observed and the Mn Kα, Kβ lines at 5.89 keV and 6.49 keV, respectively, could clearly be resolved by pulse-height analysis. An energy resolution of ΔE(FWHM) = 250 eV was obtained in the first tests reported here. Improvements may be possible by straightforward techniques.

https://iopscience.iop.org/article/10.1209/0295-5075/1/4/002/pdf

E. Umlauf

Papers

High-Resolution X-Ray Detection with Superconducting Tunnel Junctions