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Primary activity measurement of an Am-241 solution using microgram inkjet gravimetry
and decay energy spectrometry
Ryan P. Fitzgerald, Bradley Alpert, Denis E. Bergeron, Max Carlson, Richard Essex, Sean
Jollota, Kelsey Morgan, Shin Muramoto, Svetlana Nour, Galen O’Neil, Daniel R. Schmidt,
Gordon Shaw, Daniel Swetz, and R. Michael Verkouteren
National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD USA
Keywords
radionuclide metrology; quantitative analysis; radioactivity; decay energy spectrometry;
cryogenic calorimetry; inkjet gravimetry; transition edge sensor; TES
Abstract
We demonstrate a method for radionuclide assay that is spectroscopic with 100 % counting
efficiency for alpha decay. Advancing both cryogenic decay energy spectrometry (DES) and
drop-on-demand inkjet metrology, a solution of Am-241 was assayed for massic activity (of
order 100 kBq/g) with a relative combined standard uncertainty less than 1 %. We implement
live-timed counting, spectroscopic analysis, validation by liquid scintillation (LS) counting, and
confirmation of quantitative solution transfer. Experimental DES spectra are well modeled with a
Monte Carlo simulation. The model was further used to simulate Pu-238 and Pu-240 impurities,
calculate detection limits, and demonstrate the potential for tracer-free multi-nuclide analysis,
which will be valuable for new cancer therapeutics based on decay chains, Standard Reference
Materials (SRMs) containing impurities, and more widely in nuclear energy, environmental
monitoring, security, and forensics.
