Measurements of radially and temporally distributed laser-induced plasma parameters

ORAL

Abstract

Laser-induced optical breakdown is generated in a mixture of ultra-high purity hydrogen and nitrogen gas inside a cell. The hydrogen and nitrogen gas mixture ratio is 9 to 1 at a pressure of 1.21 \textpm 0.03 \texttimes 10$^{\mathrm{5}}$ Pa. The radiation of a Q-switched Nd:YAG laser device, operated at its fundamental wavelength of 1064 nm, is focused to above threshold irradiance for generation of optical breakdown. For the determination of characteristic parameters of the transient micro-plasma in a gas mixture, spatially and temporally resolved line-of-sight spectra of hydrogen \textit{Balmer} series H$_{\mathrm{\alpha }}$ and H$_{\mathrm{\beta }}$ lines are recorded. The line-of-sight measurements are \textit{Abel} inverted to extract the radial distributions of electron number density and temperature. Slight asymmetries observed in the recorded data are also considered in the analysis. The plasma kernel expansion speeds of 2 \textpm 0.4 km/s and 1.5 \textpm 0.3 km/s are determined at the time delays of 100 ns and 200 ns, respectively. Shockwave expansion speeds are also determined for these time delays. Furthermore, the isentropic micro-plasma expansion model is discussed in the data analysis.

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Authors

  • Ghaneshwar Gautam

    Univ of Tennessee Space Inst

  • Jonathan Tan

    Duquesne University, Baker Hughes, Hampton University, Korea Research Institute of Standards and Science, Electronics and Telecommunications Research Institute, Texas Christian University, University of North Texas Health Science Center, Austin Peay State University, Virginia Military Institute, Pennsylvania State University, University of Virginia, Washington University, National Institute for Materials Science, Japan, Tokyo Metropolitan University, Japan, Univ of Kentucky, Argonne National Laboratory, Oak Ridge National Laboratory, Univ of Virginia, James Madison University, Department of Chemistry & Biochemistry, High Point University, Department of Chemistry, High Point University, Department of Physics, James Madison University, Department of Physics & Astronomy, Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, VA, Institute of Renewable Energy and Environment Technology, University of Bolton, Bolton, UK, Division of Materials Science and Engineering, Ames Laboratory, US Dept. of Energy, Ames, IA, Lehigh University, University of Pardubice, Universite de Rennes, Jan Dlugosz University, Translume, NSCL/FRIB, Duke University, University of Massachusetts - Amherst, University of St. Andrews, National Radio Astronomy Observatory, University of Florida, Yale University, None, Georgia College & State Univ, Georgia College & State University, National University of Sciences and Technology (NUST), Univ of Tennessee Space Inst, The University of Virginia, Chiang Mai University, DHA Suffa University, Faculty of Chemical Technology, University of Pardubice, Pardubice, Czech Republic, Department of Physics and Astronomy, Austin Peay State University, Clarksville, TN, United States, George Mason University, Northern Virginia Community College, Department of Physics, University of Virginia, Istanbul University, Georgia College and State University, University of Houston, Western Kentucky Univ, James Madison University, Virginia Polytechnic Institute and State University, Pontifica Universidad Catolica de Chile, Trent University, Univ of Arizona, Ohio State University, NRAO, University of Virginia/NRAO