Direct Detection of Pu-242 with a Metallic Magnetic Calorimeter Gamma-Ray Detector

Abstract

Cryogenic high-resolution γ -ray detectors can improve the accuracy of non-destructive assay (NDA) of nuclear materials in cases where conventional highpurity germanium detectors are limited by line overlap or by the Compton background. We have improved the performance of gamma detectors based on metallic magnetic calorimeters (MMCs) by separating the 0.5 × 2 × 0.25 mm 3 Au absorber from the Au:Er sensor with sixteen 30-µm-diameter Au posts. This ensures that the entire γ -ray energy thermalizes in the absorber before heating the Au:Er sensor, and improves the energy resolution at 35 mK to as low as 90 eV FWHM at 60 keV. This energy resolution enables the direct detection of γ -rays from Pu-242, an isotope that cannot be measured by traditional NDA and whose concentration is therefore inferred through correlations with other Pu isotopes. The Pu-242 concentration of 11.11 ± 0.42 % measured by NDA with MMCs agrees with mass spectrometry results and exceeds the accuracy of correlation measurements.

Design, fabrication and characterization of a 64 pixel metallic magnetic calorimeter array with integrated, on-chip microwave SQUID multiplexer

“…Low-temperature microcalorimeters such as semiconductor thermistors [1], superconducting transition edge sensors (TESs) [2,3], magnetic penetration depth thermometers [4] and metallic magnetic calorimeters (MMCs) [4][5][6] are presently strongly advancing the state-of-the-art in single particle detection for various kinds of applications including atomic and nuclear physics [7][8][9][10][11], direct neutrino mass determination [12,13], searches for neutrinoless double beta decay [14,15], nuclear safeguards [16,17], Q-spectroscopy [18,19], radiation metrology [20][21][22][23], mass spectrometry [24], and material analysis [25,26]. In general, a microcalorimeter consists of an absorber for the particles to be detected that is in tight thermal contact with a highly sensitive thermometer monitoring the temperature change of the detector upon the absorption of an energetic particle.…”

Measurement of the electron capture probabilities of 55 Fe with a metallic magnetic calorimeter

“…Metallic magnetic calorimeters (Enss et al, 2000;Fleischmann et al, 2005) are a specific type of cryogenic detector that can be adapted to soft and hard X-ray (Porst et al, 2014;Bates et al, 2016), alpha (Jang et al, 2012), beta (Rotzinger et al, 2008), and optical photon detection. At the Laboratoire National Henri Becquerel (LNE-LNHB), they have been used so far for low energy beta spectrometry (Loidl et al, 2010), as well as for photon spectrometry below 100 keV (Rodrigues and Loidl, 2016).…”