A Pragmatic Approach to Improving Spectral Resolution for Laser-induced Breakdown of Nuclear Materials

An immediate need exists for methods that would enable rapid, real-time characterization of nuclear materials. Laser-induced breakdown spectroscopy (LIBS) is an established optical emission spectroscopy technique that can potentially meet the requirements for rapid analysis with little to no sample preparation. Traditionally based on the measurement of element-specific emissions, LIBS has recently been successfully applied to determine the isotopic content of nuclear materials. However, since high spectral resolution is needed for isotopic measurements, large and costly components are typically required. Coupling a relatively inexpensive, compact Fabry-Perot (FP) etalon to a conventional spectrometer represents a pragmatic approach for obtaining high-resolution spectra for isotopic measurements. An FP etalon consists of two highly reflecting, semi-transparent mirrors that transmit specific wavelengths of light. A high-resolution LIBS emission spectrum can be reconstructed from the spatially encoded angular pattern of light transmitted through the etalon. Instrumental design and methods of data analysis are important considerations for achieving the high resolution and low limit of detection in this approach. The choice and layout of optical components impacts the resolution of the system and the data interpretation. The results of this work could lead to compact, low-cost, and high-resolution LIBS instruments with isotopic-measurement capability for fingerprinting nuclear materials.