The spectral response of superconducting tunnel junction X-ray detectors

Stephan Friedrich, Rolf Fliegauf, Matthias Frank, Markus Veldkamp, Simon Labov, Burkhard Beckhoff, Gerhard Ulm

Research output: Contribution to journalConference articlepeer-review

8 Scopus citations


The Advanced Detector Group at LLNL is developing superconducting Nb-Al-AlOx-Al-Nb tunnel junction detector arrays for high-resolution soft X-ray spectrometry. We have characterized the detector response function in the energy range between 50 and 2000 eV with monochromatic X-rays, in collaboration with the Physikalisch-Technische Bundesanstalt Laboratory at the BESSY II electron storage ring. The detectors have an energy resolution between 7 and 15 eV FWHM in that energy range, and a count rate capability of ∼10,000 counts/s per detector pixel. In addition, the detector response function exhibits several spectral artifacts, and although their magnitude is only on the order of 1% of the main line, they can reduce the sensitivity for X-ray analysis of dilute specimens if they overlap with the correspondingly weak emission lines. We have characterized these artifacts by scanning a collimated synchrotron radiation beam across the detector area. We identify their origin due to X-ray absorption at locations other than the main Nb absorber film, and outline future detector designs to reduce the artifacts and thereby extend the spectrometer sensitivity.


  • STJ line shapes
  • STJ response functions
  • Superconducting devices
  • Superconducting tunnel junctions
  • Synchrotron detectors
  • X-ray spectrometers

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Instrumentation


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