Research Summaries

Back Resonance Ionization Mass Spectrometry for Post-Detonation Nuclear Forensics

Fiscal Year 2013
Division Graduate School of Engineering & Applied Science
Department Physics
Investigator(s) Smith, Craig F.
Sponsor Defense Threat Reduction Agency (DoD)
Summary Isotope ratio measurements of actinide elements provide essential information for nuclear detonation forensics. Current techniques require time-consuming sample preparation and separation chemistry. Resonance Ionization Mass Spectrometry (RIMS) has the potential to provide quantification within 1 - 2 hours after sample receipt. RIMS is a high-sensitivity, elementally selective, laser-based form of mass spectrometry that offers the potential to determine the isotopic composition of materials without sample preparation. Due to the elementally selective approach of RIMS, basic research on atomic spectroscopy and the probability for producing neutral atoms in the gas phase, must be studied element-by-element. The RIMS method has been developed for U, but other elements such as Pu, Am, Cm, Np, and Th, as well as important fission and activation products have not yet been studied for this application. Several significant questions concerning the application of this technique to post-detonation debris remain unexplored. We propose to focus on three areas. (1) What are the isotopic fractions that can be produced as neutral atoms in the gas phase when sampled from a solid silicate matrix? Can this be improved using alternative techniques? (2) What are the isotopic relative ionization probabilities under practical ionization conditions? What are the demands on laser performance required by the relative ionization probabilities? (3) Given these demands, what is the best laser system for applying RIMS to post-detonation debris? The studies proposed in this work represent basic research essential to determine the potential of RIMS to enable rapid and reliable measurement of isotope ratios from post-detonation materials.
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