Analysis of the Correlation Between Re Filament Surface Features and TIMS Performance
Technical Report,01 Sep 2018,01 Mar 2020
AIR FORCE INSTITUTE OF TECHNOLOGY WRIGHT-PATTERSON AFB OH WRIGHT-PATTERSON AFB United States
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Thermal Ionization Mass Spectrometry TIMS is an invaluable tool in nuclear forensics as it enables isotopic assays of actinides to be measured, permitting analysis to include special nuclear material isotopic assays, nuclear reactor monitoring, and treaty verification. In one method of measurement for the TIMS system, samples are deposited in solution form on high purity rhenium filaments. The filaments are heated to evaporate the solvent, and then further heated to cause sample ionization, permitting the sample to be transmitted through a magnetic field which separates ions based on mass to charge ratio into detectors for counting. Heavier ions will be deflected less by the magnetic field than lighter ions with equivalent charges. Critical to the function of TIMS is the rhenium filaments themselves any variability that suppresses ionization of the samples can lead to reduction in the number of ions detected. This research examines twenty-four filaments utilized in TIMS that have already been used for actinide analysis, with varying degrees of ionization efficiency. By examining the surface of the filaments using scanning electron microscopy SEM, energy-dispersive x-ray spectroscopy EDS, optical microscopy and electrical conductivity analysis, this research determined that there was correlation between filament shape and reported filament efficiency.
- Nuclear Physics and Elementary Particle Physics