Temperature dependence of a superconducting tunnel junction x-ray detector

Lawrence J. Hiller, Simon E. Labov, Carl A. Mears, Andrew T. Barfknecht, Matthias Frank, Harrie Netel, Mark A. Lindeman

Research output: Chapter in Book/Report/Conference proceedingConference contribution

6 Scopus citations


Superconducting tunnel junctions can be used as part of a high-resolution, energy-dispersive x- ray detector. The energy of the absorbed x ray is used to break superconducting electron pairs, producing on the order of 10 6 excitations, called quasiparticles. The number of quasiparticles produced is proportional to the energy of the absorbed x ray. When a bias voltage is maintained across the barrier, these quasiparticles produce a net tunneling current. Either the peak tunneling current or the total tunneled charge may be measured to determine the energy of the absorbed x ray. The tunneling rate, and therefore the signal, is enhanced by the use of a quasiparticle trap near the tunnel barrier. The trapping efficiency is improved by decreasing the energy gap, though this reduces the maximum temperature at which the device may operate. In our niobium/aluminum configuration, we can very the energy gap in the trapping layer by varying its thickness. This paper examines the performance of two devices with 50 nm aluminum traps at temperatures ranging from 100 mK to 700 mK. We found that this device has a very good energy resolution of about 12 eV FWHM at 1 keV. This energy resolution is independent of temperature for much of this temperature range.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsOswald H. Siegmund, John V. Vallerga
Number of pages7
StatePublished - Dec 1 1995
Externally publishedYes
EventEUV, X-Ray, and Gamma-Ray Instrumentation for Astronomy VI - San Diego, CA, USA
Duration: Jul 12 1995Jul 14 1995


OtherEUV, X-Ray, and Gamma-Ray Instrumentation for Astronomy VI
CitySan Diego, CA, USA

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics


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