Atom Probe Mass Spectrometry of Uranium Isotopic Reference Materials
Frederick Meisenkothen, Mark McLean, Irina Kalish, Daniel V. Samarov, Eric B. Steel
Atom probe tomography (APT) has the highest spatial resolution of any mass spectrometry technique, permitting chemically and isotopically resolved images to be recorded at near-atomic length scales. The technique also has a combined ionization efficiency and detection efficiency that can approach 80%, in contrast to other mass spectrometry techniques, such as secondary ion mass spectrometry and thermal ionization mass spectrometry, which typically have a combined efficiency of a few percent. APT is, thus, becoming increasingly attractive for analysis applications requiring small volumes of material and sub-micron length scales, such as geological materials and geochronology; nuclear fuels and nuclear forensics, semiconductor materials, and meteoritic materials. However, there is an open question within the atom probe community as to the reliability of atom probe isotopic and elemental analyses. Using our proposed analysis guidelines, in conjunction with an empirical calibration curve and a machine learning-based adaptive peak fitting algorithm, we demonstrate accurate and reproducible uranium isotopic analyses, via atom probe mass spectrometry, on U3O8 isotopic reference materials. By using isotopic reference materials, each measured isotopic abundance value could be directly compared to a known certified reference value to permit a quantitative statement of accuracy. The isotopic abundance measurements for 235U and 238U in each individual APT sample were consistently within ± 1.5 % relative to the known reference values. The achieved accuracy and reproducibility were consistent with measurements limited primarily by Poisson counting statistics, i.e., the number of uranium atoms recorded.
, McLean, M.
, Kalish, I.
, Samarov, D.
and Steel, E.
Atom Probe Mass Spectrometry of Uranium Isotopic Reference Materials, Analytical Chemistry, [online], https://doi.org/10.1021/acs.analchem.0c02273
(Accessed July 27, 2021)