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Proceedings Paper

Soft x-ray and EUV response of superconducting tunnel junctions: strong deviations from linearity
Author(s): Abel Poelaert; Alex G. Kozorezov; Anthony J. Peacock; K. Wigmore; Peter Verhoeve; Axel van Dordrecht; Alan Owens; Nicola Rando
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Paper Abstract

Nb-Al-AlOx-Al-Nb Superconducting Tunnel Junctions (SJT's) have been extensively investigated by a number of groups as potential next generation high resolution photon detectors for x-ray astronomy. The response of such devices has been studied from EUV to soft x-rays, using highly monochromatic synchrotron radiation. Based on the current understanding of the charge production and tunneling mechanisms in STJ's, it would be expected that at lower energies, the responsivity of the detector would increase as the role of self-recombination of charge carriers into Cooper pairs declines in importance. Here responsivity is simply defined as the measured charge per eV of photon energy deposited in the junction. This trend however was not observed till the lowest energies. Below a threshold energy the responsivity fell, reaching a minimum level, after which it became constant. This minimum level is lower than the responsivity at 6 keV, by a factor up to 5, leading to a clear mismatch between x-ray and EUV performance. This paper summarizes the observations, and presents quantitative explanations for the feature, based on the existence of local traps in the STJ.

Paper Details

Date Published: 10 November 1998
PDF: 12 pages
Proc. SPIE 3445, EUV, X-Ray, and Gamma-Ray Instrumentation for Astronomy IX, (10 November 1998); doi: 10.1117/12.330279
Show Author Affiliations
Abel Poelaert, European Space Agency/ESTEC (Netherlands)
Alex G. Kozorezov, Univ. of Lancaster (United Kingdom)
Anthony J. Peacock, European Space Agency/ESTEC (Netherlands)
K. Wigmore, Univ. of Lancaster (United Kingdom)
Peter Verhoeve, European Space Agency/ESTEC (Netherlands)
Axel van Dordrecht, European Space Agency/ESTEC (Netherlands)
Alan Owens, European Space Agency/ESTEC (Netherlands)
Nicola Rando, European Space Agency/ESTEC (Netherlands)

Published in SPIE Proceedings Vol. 3445:
EUV, X-Ray, and Gamma-Ray Instrumentation for Astronomy IX
Oswald H. W. Siegmund; Mark A. Gummin, Editor(s)

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