Comparing Femtosecond Libs Uv-Vis Spectrum Of Trace Elements In Synthetic Nuclear Melt Glass And Trinitite For Nuclear Forensics

J. Daniel Hartman - University of Tennessee, Knoxville
Benjamin S. Jordan - University of Tennessee, Knoxville
Dean Forrest - University of Tennessee, Knoxville
Elijah J. Rosenburg - University of Tennessee, Knoxville
Howard L. Hall - University of Tennessee, Knoxville
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On July 16, 1945, the very first atomic (nuclear) bomb was detonated at the Trinity Test Site in Alamogordo, New Mexico. The sandy ground that surrounded the atomic bomb test site was heated to a temperature hotter than the sun and transformed into a geologic medium known as Trinitite (nuclear melt glass). Over 75 years and eight additional nuclear weapon possessing states later, the need to accurately ascertain the origins of nuclear weapons material in a timely manner (nuclear forensics) has never been more important. A surge in nuclear forensics research requiring trinitite over the past couple of decades led to a search for an accurate surrogate material. Recent work at the University of Tennessee Knoxville has resulted in the successful synthetization of nuclear melt glass, whose elemental composition closely resembles that of authentic Trinitite. This paper will introduce a novel comparison of the Ultraviolet-Visible spectrum (300-500 nm) of the Laser Induced Breakdown Spectroscopy (LIBS) of trace elements in synthetic (radioactive and non-radioactive) nuclear melt glass and authentic trinitite with a Femtosecond (Fs) laser. Accounting for the exception of the purposeful absence of uranium in the non-radioactive melt glass, unique characteristic peaks for all eleven elements which make up trinitite were found in each of the three various sample types and subsequently cross referenced through use of the U.S. National Institute of Standards and Technology (NIST) LIBS database and past published Fs-LIBS literature. For this stage of the research our goal was to evaluate the ability of Fs-LIBS to identify the presence of elements in the trinitite and synthetic melt-glass that are only trace constituents of the overall composition on the material. This research paper will compare the spectral responses of trinitite and synthetic melt glass and will foreshadow the challenges of developing Fs-LIBS to the point of being able to attribute the weapon to a source based on the Fs-LIBS analysis of the trinitite. Additionally, we will report on laboratory testing techniques that were developed to provide spectra with improved signal-to-noise-ratios and the additional work needed to fully explain the plasma physics that have driven this result.