High-resolution gamma-ray spectrometers using bulk absorbers coupled to Mo/Cu multilayer superconducting transition-edge sensors

In x-ray and gamma-ray spectroscopy, it is desirable to have detectors with high energy resolution and high absorption efficiency. At LLNL, we have developed superconducting tunnel junction-based single photon x-ray detectors with thin film absorbers that have achieved these goals for photon energies up to 1 keV. However, for energies above 1 keV, the absorption efficiency of these thin-film detectors decreases drastically. We are developing the use of high-purity superconducting bulk materials as microcalorimeter absorbers for high-energy x-rays and gamma rays. The increase in absorber temperature due to incident photons is sensed by a superconducting transition- edge sensor (TES) composed of a Mo/Cu multilayer thin film. Films of Mo and Cu are mutually insoluble and therefore very stable and can be annealed. The multilayer structure allows scaling in thickness to optimize heat capacity and normal state resistance. We measured an energy resolution of 70 eV for 60 keV incident gamma-rays with a 1 X 1 X 0.25 mm3 Sn absorber. We present x-ray and gamma-ray results from this detector design with an Sn absorber. We also propose the use of an active negative feedback voltage bias to improve the performance of our detector and show preliminary results.

[1]  A. Monfardini,et al.  High Energy Resolution Bolometers for Nuclear Physics and X-Ray Spectroscopy , 1999 .

[2]  K. Irwin.  Phonon-mediated particle detection using superconducting tungsten transition-edge sensors , 1995 .

[3]  Troy W. Barbee,et al.  Gamma-ray spectrometers using a bulk Sn absorber coupled to a Mo/Cu multilayer superconducting transition edge sensor , 1999 .

[4]  P. Egelhof,et al.  Low-temperature X-ray detectors for precise Lamb shift measurements on hydrogen-like heavy ions , 2000 .

[5]  S. Moseley,et al.  Thermal detectors as X-ray spectrometers , 1984 .

[6]  Sae Woo Nam,et al.  A new biasing technique for transition edge sensors with electrothermal feedback , 1999, IEEE Transactions on Applied Superconductivity.

[7]  Simon E. Labov,et al.  Analysis of pulse shape from a high-resolution superconducting tunnel junction X-ray spectrometer , 1996 .

[8]  G. Knoll.  Radiation detection and measurement , 1979 .

[9]  Eric H. Silver,et al.  First Use of NTD Germanium‐Based Microcalorimeters For High‐Resolution, Broadband X‐Ray Microanalysis , 1997 .

[10]  C. A. Swenson.  Linear thermal expansivity (1.5–300 K) and heat capacity (1.2–90 K) of Stycast 2850FT , 1997 .

[11]  Mark A. Lindeman,et al.  Microcalorimetry and the transition-edge sensor , 2000 .

[12]  G. Hilton,et al.  X‐ray detection using a superconducting transition‐edge sensor microcalorimeter with electrothermal feedback , 1996 .

[13]  P. L. Richards,et al.  Measurements of thermal transport in low stress silicon nitride films , 1998 .

[14]  Simon E. Labov,et al.  Energy resolution and high count rate performance of superconducting tunnel junction x-ray spectrometers , 1998 .