7 research outputs found
RIMS analysis of ion induced fragmentation of molecules sputtered from an enriched U3O8 matrix
Quantifying Uranium Isotope Ratios Using Resonance Ionization Mass Spectrometry: The Influence of Laser Parameters on Relative Ionization Probability
Resonance Ionization Mass Spectrometry (RIMS) has been developed as a method to measure relative uranium isotope abundances. In this approach, RIMS is used as an element-selective ionization process to provide a distinction between uranium atoms and potential isobars without the aid of chemical purification and separation. We explore the laser parameters critical to the ionization process and their effects on the measured isotope ratio. Specifically, the use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of {sup 235}U/{sup 238}U ratios to decrease laser-induced isotopic fractionation. By broadening the bandwidth of the first laser in a 3-color, 3-photon ionization process from a bandwidth of 1.8 GHz to about 10 GHz, the variation in sequential relative isotope abundance measurements decreased from >10% to less than 0.5%. This procedure was demonstrated for the direct interrogation of uranium oxide targets with essentially no sample preparation. A rate equation model for predicting the relative ionization probability has been developed to study the effect of variation in laser parameters on the measured isotope ratio. This work demonstrates that RIMS can be used for the robust measurement of uranium isotope ratios
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Uranium Resonance Ionization Mass Spectrometry in Natural U-silicate
Effects of Plume Hydrodynamics and Oxidation on the Composition of a Condensing Laser-Induced Plasma
High-temperature
chemistry in laser ablation plumes leads to vapor-phase
speciation, which can induce chemical fractionation during condensation.
Using emission spectroscopy acquired after ablation of a SrZrO<sub>3</sub> target, we have experimentally observed the formation of
multiple molecular species (ZrO and SrO) as a function of time as
the laser ablation plume evolves. Although the stable oxides SrO and
ZrO<sub>2</sub> are both refractory, we observed emission from the
ZrO intermediate at earlier times than SrO. We deduced the time-scale
of oxygen entrainment into the laser ablation plume using an <sup>18</sup>O<sub>2</sub> environment by observing the in-growth of Zr<sup>18</sup>O in the emission spectra relative to Zr<sup>16</sup>O, which
was formed by reaction of Zr with <sup>16</sup>O from the target itself.
Using temporally resolved plume-imaging, we determined that ZrO formed
more readily at early times, volumetrically in the plume, while SrO
formed later in time, around the periphery. Using a simple temperature-dependent
reaction model, we have illustrated that the formation sequence of
these oxides subsequent to ablation is predictable to first order
Determination of Traces of Uranium and Thorium in Titanium and Copper Used for the Construction of the Russian Emission Detector 100 by Inductively Coupled Plasma Mass Spectrometry
Construction of a Modular Large-Area Neutron Detector for the NSCL
A collaboration of ten institutions, including a large number of undergraduate schools, proposed and constructed a highly efficient large-area neutron detector. The modular neutron array (MoNA) is designed to detect high-energy neutrons in experiments with fast rare isotopes at the National Superconducting Cyclotron Laboratory. It consists of 144 individual detector modules of plastic scintillator, is position sensitive, and features multi-hit capability. The MoNA project involves undergraduate students from the collaborating colleges and universities and gives them the possibility to take part in research at the forefront of nuclear physics. © 2005 Elsevier B.V. All rights reserved