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Superconducting tunnel junctions as detectors for high‐resolution x‐ray spectroscopy
Author(s) -
Huber M.,
Angloher G.,
Hollerith C.,
Ruedig A.,
Jochum J.,
Potzel W.,
Feilitzsch F. v.
Publication year - 2004
Publication title -
x‐ray spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.447
H-Index - 45
eISSN - 1097-4539
pISSN - 0049-8246
DOI - 10.1002/xrs.715
Subject(s) - detector , full width at half maximum , superconductivity , superconducting tunnel junction , absorption (acoustics) , quantum tunnelling , spectrometer , resolution (logic) , optoelectronics , materials science , electrode , physics , energy (signal processing) , x ray detector , quantum efficiency , optics , condensed matter physics , josephson effect , pi josephson junction , quantum mechanics , artificial intelligence , computer science
Abstract Superconducting tunnel junctions (STJs) are a type of cryogenic detector with a working temperature of about 100 mK. They allow the combination of low energy threshold, high quantum efficiency and good count rate capability with an excellent energy resolution; at an x‐ray energy of 5.9 keV an energy resolution of 10.8 eV (FWHM) has been achieved. The detector system described is based on STJs which consist of two superconducting Al electrodes separated by a thin dielectric tunnel barrier. The tunneling process of quasi‐particles created by deposition of energy in the electrodes leads to a detectable current signal. The STJ is equipped with a superconducting Pb absorber which is read out via phonons. The Pb absorber increases absorption efficiency (∼50% at 6 keV) and suppresses detector artefacts. The degeneration of Pb, most probably due to oxidation, is overcome by the introduction of a protective SiO layer on top of the absorber. This layer leads to a slight reduction of energy resolution. Nevertheless, a resolution of 9.7 eV at 1.7 keV and of ∼20 eV at 5.9 keV could be realized with a prototype detector. Currently this STJ‐based detector system is being incorporated into a prototype cryogenic spectrometer for XRF analysis. Copyright © 2004 John Wiley & Sons, Ltd.