Online monitoring of hydrogen processing using hollow-core waveguide-based Raman spectroscopy

Online monitoring of a process is essential for industrial scale production, in particular the separation and processing of tritium at the Savannah River Site in Aiken, SC. Current technologies that support hydrogen isotope quantification rely on single "grab samples" that are analyzed offline or active sampling from production. Here, we describe progress towards an online gas monitoring technique using hollow-core waveguide Raman spectroscopy. The system is being initially developed for use in hydrogen processing systems but will have wider applicability. Commercially available fibers are employed for the enhancement of collecting Raman scattered light through optical alignment and high-power visible laser systems. A 532nm diode pumped solid state laser system focuses light through a hollow core waveguide that is arranged as a flow cell for gaseous samples. Reverse-scattering detection is coupled to a Horiba iHR320 spectrometer (0.318m; 2400 lines/mm grating) and an air-cooled CCD detector (–60 °C). Gaseous samples include argon carrier gas with ammonia (NH3), methane (CH4), and nitrogen (N2) in addition to hydrogen isotopes (H2 and D2). We have demonstrated the ability to simultaneously measure H2, HD, and D2 with sensitivities and dynamic range from 100s to 10,000s of parts per million.