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A broadband superconducting detector suitable for use in large arrays


Cryogenic detectors are extremely sensitive and have a wide variety of applications1,2,3 (particularly in astronomy4,5,6,7,8), 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 missions7 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.

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Figure 1: An illustration of the detection principle.
Figure 2: A microscope photograph of the device tested.
Figure 3: The microwave measurement set-up and the phase calibration of the detector. A low-phase noise microwave synthesizer (right inset) generates the fixed-frequency signal used to excite the detector, which is cooled in a dilution refrigerator.
Figure 4: Single-photon X-ray pulses measured at 70 and 300 mK.
Figure 5: A plot of the noise measured for the test device; several other devices have given similar results.


  1. Newbury, D. et al. The approaching revolution in X-ray microanalysis: The microcalorimeter energy dispersive spectrometer. J. Radioanal. Nucl. Chem. 244, 627–635 (2000)

    Article  CAS  Google Scholar 

  2. Booth, N., Cabrera, B. & Fiorini, E. Low-temperature particle detectors. Annu. Rev. Nucl. Part. Sci. 46, 471–532 (1996)

    Article  ADS  CAS  Google Scholar 

  3. Saab, T. et al. Deployment of the first CDMS II ZIP detectors at the Stanford Underground Facility. Nucl. Phys. B 110, 100–102 (2002)

    Article  CAS  Google Scholar 

  4. Peacock, A. et al. Single optical photon detection with a superconducting tunnel junction. Nature 381, 135–137 (1996)

    Article  ADS  CAS  Google Scholar 

  5. Cabrera, B. et al. Detection of single infrared, optical, and ultraviolet photons using superconducting transition edge sensors. Appl. Phys. Lett. 73, 735–737 (1998)

    Article  ADS  CAS  Google Scholar 

  6. Lee, S., Gildemeister, J., Holmes, W., Lee, A. & Richards, P. Voltage-biased superconducting transition-edge bolometer with strong electrothermal feedback operated at 370 mK. Appl. Opt. 37, 3391–3397 (1998)

    Article  ADS  CAS  Google Scholar 

  7. de Korte, P. Cryogenic imaging spectrometers for X-ray astronomy. Nucl. Instrum. Meth. A 444(1–2), 163–169 (2000)

    Article  ADS  CAS  Google Scholar 

  8. Rando, N. et al. S-cam: A spectrophotometer for optical astronomy: Performance and latest results. Rev. Sci. Instrum. 71(12), 4582–4591 (2000)

    Article  ADS  CAS  Google Scholar 

  9. Twerenbold, D. Giaever-type superconducting tunneling junctions as high-resolution X-ray-detectors. Europhys. Lett. 1(5), 209–214 (1986)

    Article  ADS  CAS  Google Scholar 

  10. Kraus, H. et al. High-resolution X-ray-detection with superconducting tunnel-junctions. Europhys. Lett. 1(4), 161–166 (1986)

    Article  ADS  CAS  Google Scholar 

  11. Irwin, K., Hilton, G., Wollman, D. & Martinis, J. X-ray detection using a superconducting transition-edge sensor microcalorimeter with electrothermal feedback. Appl. Phys. Lett. 69(13), 1945–1947 (1996)

    Article  ADS  CAS  Google Scholar 

  12. Irwin, K. et al. A Mo-Cu superconducting transition-edge microcalorimeter with 4.5 eV energy resolution at 6 keV. Nucl. Instrum. Meth. A 444, 184–187 (2000)

    Article  ADS  CAS  Google Scholar 

  13. Angloher, G. et al. Energy resolution of 12 eV at 5.9 keV from Al superconducting tunnel junction detectors. J. Appl. Phys. 89, 1425–1429 (2001)

    Article  ADS  CAS  Google Scholar 

  14. Li, L. et al. Improved energy resolution of X-ray single photon imaging spectrometers using superconducting tunnel junctions. J. Appl. Phys. 90, 3645–3647 (2001)

    Article  ADS  CAS  Google Scholar 

  15. Chervenak, J. et al. Superconducting multiplexer for arrays of transition edge sensors. Appl. Phys. Lett. 74, 4043–4045 (1999)

    Article  ADS  CAS  Google Scholar 

  16. Yoon, J. et al. Single superconducting quantum interference device multiplexer for arrays of low-temperature sensors. Appl. Phys. Lett. 78, 371–373 (2001)

    Article  ADS  CAS  Google Scholar 

  17. Mazin, B. A., Day, P. K., Leduc, H. G., Vayonakis, A. & Zmuidzinas, J. Superconducting kinetic inductance photon detectors. Proc. SPIE 4849, 283–293 (2002)

    Article  ADS  Google Scholar 

  18. Tinkham, M. Introduction to Superconductivity, 2nd edn (McGraw-Hill, New York, 1996)

    Google Scholar 

  19. Kozorezov, A. G. et al. Quasiparticle-phonon downconversion in nonequilibrium superconductors. Phys. Rev. B 61 (May), 11807–11819 (2000)

    Article  ADS  CAS  Google Scholar 

  20. Mattis, D. C. & Bardeen, J. Theory of the anomalous skin effect in normal and superconducting metals. Phys. Rev. 111, 412–417 (1958)

    Article  ADS  Google Scholar 

  21. Moseley, S., Mather, J. & McCammon, D. Thermal detectors as x-ray spectrometers. J. Appl. Phys. 56, 1257–1262 (1984)

    Article  ADS  CAS  Google Scholar 

  22. Wilson, C., Frunzio, L. & Prober, D. Time-resolved measurements of thermodynamic fluctuations of the particle number in a nondegenerate Fermi gas. Phys. Rev. Lett. 87, 067004 (2001)

    Article  ADS  CAS  Google Scholar 

  23. Sergeev, A., Mitin, V. & Karasik, B. Ultrasensitive hot-electron kinetic-inductance detectors operating well below the superconducting transition. Appl. Phys. Lett. 80, 817–819 (2002)

    Article  ADS  CAS  Google Scholar 

  24. Zmuidzinas, J. & LeDuc, H. G. Quasi-optical slot antenna SIS mixers. IEEE Trans. Microwave Theory Tech. MTT-40, 1797–1804 (1992)

    Article  ADS  Google Scholar 

  25. Li, L., Frunzio, L., Wilson, C. & Prober, D. Quasiparticle nonequilibrium dynamics in a superconducting Ta film. J. Appl. Phys. 93, 1137–1141 (2003)

    Article  ADS  CAS  Google Scholar 

  26. Chang, W. Inductance of a superconducting strip transmission-line. J. Appl. Phys. 50, 8129–8134 (1979)

    Article  ADS  Google Scholar 

  27. McMillan, W. Transition temperature of strong-coupled superconductors. Phys. Rev. 167, 331–334 (1968)

    Article  ADS  CAS  Google Scholar 

  28. Wells, G. L., Jackson, J. E. & Mitchell, E. N. Superconducting tunneling in single-crystal and polycrystal films of aluminum. Phys. Rev. B 1, 3636–3644 (1970)

    Article  ADS  Google Scholar 

  29. Kaplan, S. et al. Quasiparticle and phonon lifetimes in superconductors. Phys. Rev. B 14, 4854–4873 (1976)

    Article  ADS  CAS  Google Scholar 

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This work has been supported in part by NASA (Aerospace Technology Enterprise), the JPL Director's Research and Development Fund, and the Caltech President's Fund. We are grateful for the support of A. Lidow, Caltech Trustee.

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Correspondence to Peter K. Day.

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Day, P., LeDuc, H., Mazin, B. et al. A broadband superconducting detector suitable for use in large arrays. Nature 425, 817–821 (2003).

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