Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Large array of multiplexed gamma-ray microcalorimeters for nuclear-materials analysis



W.Bertrand (Randy) Doriese, Joel Ullom, James A. Beall, William Duncan, S. L. Ferreira, Gene C. Hilton, Rob Horansky, Kent D. Irwin, John Mates, Carl D. Reintsema, Dan Schmidt, Leila R. Vale, Yizi Xu, Barry L. Zink, Michael W. Rabin, Minesh K. Bacrania, Stephen Lamont, Andrew Hoover, Clifford R. Rudy, Duc Vo, C. K. Stahle, Kevin R. Boyce, Larry E. Brown, Jonathan M. King, F. S. Porter


We are developing a gamma-ray spectrometer for the analysis of nuclear materials based on an array of superconducting transition-edge-sensor microcalorimeters. The instrument includes eight columns of time-division-SQUID multiplexing circuitry capable of reading out 256 sensors. Our most recent sensors are bulk (1.5 mm-square by 0.25 mm-thick) superconducting-Sn absorbers glued to Mo/Cu bilayer thermometers. When fully populated, the active area of the spectrometer will be 5.76 cm^2, and the maximum count rate of the array will approach 20 kHz. Thus, our spectrometer will be comparable to the state-of-the-art 100 keV high-purity-Ge detector in count rate and collecting area, but with an order of magnitude better energy resolution. Half the detectors will be optimized for operation up to 100 keV, and the other half for operation up to 200 keV. A version of the spectrometer with a partially populated detector array was delivered to Los Alamos in June, 2007. We describe the present status of that instrument. In addition, we review results from a prototype array of 14 detectors, which achieved 47 eV average energy resolution (full width at half maximum, at 103 keV) and 25 eV resolution in the best detector. An important application of this technology is determining the total Pu content in spent reactor fuel without detailed knowledge of the reactor''s operating history.
Proceedings Title
Journal Of Low Temperature Physics
Conference Dates
July 23-27, 2007
Conference Location
Paris, 1, FR
Conference Title
Low-Temperature Detectors 12


gamma-ray spectrometer, microcalorimeter, transition-edge sensor


Doriese, W. , Ullom, J. , Beall, J. , Duncan, W. , Ferreira, S. , Hilton, G. , Horansky, R. , Irwin, K. , Mates, J. , Reintsema, C. , Schmidt, D. , Vale, L. , Xu, Y. , Zink, B. , Rabin, M. , Bacrania, M. , Lamont, S. , Hoover, A. , Rudy, C. , Vo, D. , Stahle, C. , Boyce, K. , Brown, L. , King, J. and Porter, F. (2008), Large array of multiplexed gamma-ray microcalorimeters for nuclear-materials analysis, Journal Of Low Temperature Physics, Paris, 1, FR, [online], (Accessed May 30, 2023)
Created January 23, 2008, Updated October 12, 2021