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Search Publications by: Todd Williamson (Fed)

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Displaying 1 - 8 of 8

Uranium Particle Age Dating, Aggregation, and Model Age Best Estimators

June 9, 2025
Author(s)
Evan Groopman, Todd Williamson, Timothy Pope, Michael Bronikowski, Spencer M. Scott, Matthew Wellons
We present important aspects of uranium particle age dating by Large-Geometry Secondary Ion Mass Spectrometry (LG-SIMS) that can introduce bias and increase model age uncertainties, especially for small, young, and/or low-enriched particles. This metrology

Dual-Field Multicollector LG-SIMS Analysis of Mixed U-Pu Reference Particles

June 6, 2025
Author(s)
Evan Groopman, Todd Williamson, Kyle Samperton, Spencer M. Scott, Bryan Foley, Michael Bronikowski, George King, Matthew Wellons
In this study, we demonstrate a new dual-field multicollector protocol for magnetic sector large-geometry secondary ion mass spectrometry that enables concurrent analysis of U and Pu isotopes. We apply this analysis protocol to recently produced mixed U-Pu

Magnetic Characterization of Electrodeposited Pt1-xNix Alloy Films: Influence of Deposition Potential and the Presence of Boric Acid

September 21, 2022
Author(s)
Eric Rus, Eduardo De Lima Correa, Evan Groopman, Todd Williamson, Hussein Hijazi, Leila Kasaei, Leonard Feldman, Cindi L. Dennis, Thomas P. Moffat
Pt1-xNix (x = 0.25 to 0.92) thin films were examined for possible application as temperature sensing magnetic reporters. The alloys were prepared by charge-limited potentiostatic electrodeposition from aqueous chloride-based solutions in the presence and

Improved Uranium Particle Analysis by SIMS using O3- Primary Ions

September 6, 2022
Author(s)
Evan Groopman, Todd Williamson, David S. Simons
We have investigated the use of negative molecular oxygen primary ion beams (i.e., O2- and O3-) to determine the benefits of using such beams for uranium particle SIMS analyses. Typically, O- is the most practical negative primary ion species for both age

MULTI-COLLECTOR CONFIGURATION CONSIDERATIONS AND SUBSTRATE RELATIVE SENSITIVITY FACTOR EFFECTS FOR AGE-DATING MEASUREMENTS OF PARTICLES BY LARGE GEOMETRY SECONDARY ION MASS SPECTROMETRY

October 1, 2021
Author(s)
Todd Williamson, David S. Simons, John D. Fassett
Chronometry (a.k.a age-dating, AD) of materials by bulk mass spectrometric methods is a well-established technique based on analysis protocols that have been used in geological fields and by the non-proliferation communities for many years. Recently, it
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