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PUBLICATIONS

Measurement of 227Ac Impurity in 225Ac using Decay Energy Spectroscopy

Published

Author(s)

A. D. Tollefson, C. M. Smith, M. H. Carpenter, M. P. Croce, M. E. Fassbender, K. D. John, K. E. Koehler, L. M. Lilley, E. M. O'Brien, Daniel Schmidt, B. W. Stein, Joel Ullom, M. D. Yoho, D. J. Mercer

Abstract

225Ac is a valuable medical isotope for targeted alpha therapy, but 227Ac is an undesirable byproduct of an accelerator-based synthesis method under investigation. Sufficient detector sensitivity is critical for quantifying the trace impurity of 227Ac, which may be as small as 0.15 % by activity following chemical purification. Contemporary techniques are unable to achieve this sensitivity. Superconducting transition edge sensor (TES) microcalorimeters offer high resolution energy spectroscopy using the normal-to-superconducting phase transition to measure small changes in temperature. By embedding 225Ac production samples in a gold foil thermally coupled to a TES microcalorimeter we can measure the decay energies of the isotopes embedded in a 4π geometry. This technique, known as decay energy spectroscopy (DES), collapses several peaks from alpha decays into single Q-value peaks. In practice there are more complex factors in the interpretation of data using DES, which we will discuss herein. Using DES, the end-of-bombardment (EOB) 227Ac impurity was determined to be (0.142 +/- 0.005)%. This research has shown that DES can distinguish closely related isotopic features for relative activity ratio quantification due to its extremely high resolution.
Citation
Applied Radiation and Isotopes
Pub Type
Journals

Keywords

Actinium, decay energy spectroscopy, embedded radioisotope, isotope separation, medical isotope, microcalorimetry, radiopharmaceuticals, spectroscopy, transition edge sensor
Superconductors, Spectroscopy, Sensors, Chemical / Biological / Radiological / Nuclear / Explosives (CBRNE) and Biopharmaceuticals

Citation

Tollefson, A. , Smith, C. , Carpenter, M. , Croce, M. , Fassbender, M. , John, K. , Koehler, K. , Lilley, L. , O'Brien, E. , Schmidt, D. , Stein, B. , Ullom, J. , Yoho, M. and Mercer, D. (2021), Measurement of <sup>227</sup>Ac Impurity in <sup>225</sup>Ac using Decay Energy Spectroscopy, Applied Radiation and Isotopes (Accessed March 14, 2025)

Issues

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Created March 20, 2021, Updated February 24, 2025