About the seminar:
I will discuss the evolution and application of laser-based diagnostic methods to a wide range of challenging environments across Sandia’s national-security mission space. Diagnostic approaches include: coherent anti-Stokes Raman scattering (CARS), a workhorse tool for temperature/species/pressure measurements that is emphasized throughout; “seedless” molecular tagging velocimetries using nascent species; and laser-induced incandescence for soot-particle measurements. Three consistent themes are emphasized: (1) the evolution of pulsed laser sources; (2) challenging “real-world” measurement environments; and (3) multi-parameter measurements across a wide application space. Successful applications using well-established 10-Hz, nanosecond-pulsed lasers include temperature and species detection in meter-scale sooting flames, and in the extreme 6000 K environment presented by materials testing in an inductively coupled plasma torch. Advantages of transform-limited femtosecond laser pulses for hybrid frequency/time spectroscopy are introduced, and these ultrashort pulses are demonstrated for simultaneous temperature/pressure/velocity data in compressible flows, and temperature/species detection in extremely hostile energetics applications. Modern burst-mode laser systems offer high-speed acquisition rates of 100s of kHz to 1 MHz—far outpacing repetitively pulsed laser sources. Development of tunable burst-mode-pumped sources in our lab is reviewed, and high-speed, 100-kHz thermometry and velocimetry are demonstrated in the nonequilibrium flow presented by Sandia’s free-piston shock tunnel. The talk concludes with a discussion of our current Sandia/Illinois collaboration for CARS measurements in the unique Plasmatron-X facility and a summary of ideas for joint work in areas such as propulsion and combustion, fluid mechanics, hypersonics, and energetics.
Sean Kearney is a Distinguished Member of the Technical Staff in Sandia’s Engineering Sciences Center, where he has worked since 1999 to develop and apply laser-based diagnostics to a wide variety of national-security mission areas, including as nuclear safety, combustion, hypersonics, microsystems, and energetic materials. His current research interests are focused on application of a wide variety of established and evolutionary laser sources for diagnostics in hypersonics and energetics applications. He holds a Bachelor of Science degree in Mechanical Engineering from Clarkson University and Mechanical Engineering M.S. and Ph.D. degrees from the University of Illinois at Urbana-Champaign. He is the current vice-chair of the Gordon Research Conference in Laser Diagnostics for Energy and Reacting Flow. Sean is active in the Optical Society of America (OSA) and is an Associate Fellow of the American Institute of Aeronautics and Astronautics (AIAA), where he currently serves as chair of AIAA’s Aerodynamic Measurement Technology (AMT) Technical Committee.