Improved Isotopic Analysis with a Large Array of Gamma-ray Microcalorimeters

Published

June 30, 2009

Author(s)

Nikhil Jethava, Joel N. Ullom, Douglas A. Bennett, William B. Doriese, James A. Beall, Gene C. Hilton, Robert D. Horansky, Kent D. Irwin, Eric Sassi

Abstract

We present results from the largest array of gamma-ray microcalorimeters operated to date. The microcalorimeters consist of Mo/Cu transition-edge sensors with attached Sn absorbers. The detector array contains 66 pixels each with an active area 2.25 mm2. Out of 66 pixels, 55 are active, and 31 were used to acquire a high statistics Pu gamma-ray spectrum. The energy resolution of the best 21 pixels was found to be 120 eV FWHM. The array is read out using time domain SQUID multiplexing. Here, we describe the multiplexing and present a high statistics Pu spectra. Because of the large collecting area of our array, the statistical error in the 240Pu line intensity is approximately 0.7 %, which is comparable to the systematic error in a measurement with a 500 eV germanium sensor. Hence, we have reached an important threshold for demonstrating improved isotopic measurements with microcalorimeter sensors. With straightforward improvements, we plan to achieve a resolution of about 50 eV FWHM with 256 multiplexed detectors. Finally, we present early estimates of on-chip heating within our sensor array.

Citation

IEEE Transactions on Applied Superconductivity

Volume

19

Issue

3

Pub Type

Journals

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Keywords

Transition Edge Sensor, gamma-ray microcalorimeter, SQUID multiplexing, plutonium isotopics.

Citation

Jethava, N. , Ullom, J. , Bennett, D. , Doriese, W. , Beall, J. , Hilton, G. , Horansky, R. , Irwin, K. and Sassi, E. (2009), Improved Isotopic Analysis with a Large Array of Gamma-ray Microcalorimeters, IEEE Transactions on Applied Superconductivity, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=33158 (Accessed October 27, 2025)