Characterization of an Expanding Plasma Generated in Laser-Ionized Helium

ORAL

Abstract

An 800 nm, 35 fs laser pulse is focused using f/20 optics into a jet of helium. The peak intensity exceeding $10^{16}$ W/cm$^2$ is well above the ionization threshold for helium. Subsequently, two weak probe pulses, one passing coaxially through the track of ionized plasma and the other to the side, create an interference pattern in the far field to reveal the optical path difference induced by the presence of the plasma. The probe pulses are systematically delayed over several nanoseconds to characterize how the central plasma density decreases as a function of time, owing to radial expansion of the plasma. The expansion rate is tied to the ionized electron temperature as well as the mass of the helium ions. The ion temperature and density place this plasma just inside the strongly coupled plasma regime. We show that the electron temperature increases with ionizing laser intensity.

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Authors

  • Nicholas Harrison

    None

  • John Colton

    Brigham Young University Dept. of Physics and Astronomy, Brigham Young University, None, The College of William and Mary/Jefferson Lab, Brigham Young University-Idaho, Blue Ridge Research and Consulting LLC, Air Force Research Laboratory - Wright Patterson Air Force Base, Brigham Young Univ - Provo, Blue Ridge Research and Consulting, University of Utah, SRI International, Utah State University, Utah Valley University, Los Alamos National Laboratory, Professor, Graduate, United States Air Force Academy, Arizona State Univ, SiO2 NanoTech, Entrepix Inc, AFRL, Advisor, Brigham Young University- Provo, University of New Mexico, Univ of Utah, University of Wisconsin -- Madison, New Mexico Tech Physics Dept., Retired, Department of Physics and Astronomy, University of Utah, Department of Physics \& Astronomy, University of Hawai'i, JILA and University of Colorado, Boulder, National Institute of Standards and Technology, Boulder, University of Colorado, Boulder, Lawrence Berkeley National Laboratory, National Institute of Standards and Technology, Space Dynamics Lab, New Mexico Tech, BYU Professor, Brigham Young University -- Provo, Northern Arizona University, University of Colorado Boulder, Colorado State University, University of Utah, Department of Physics, New Mexico State University

  • John Colton

    Brigham Young University Dept. of Physics and Astronomy, Brigham Young University, None, The College of William and Mary/Jefferson Lab, Brigham Young University-Idaho, Blue Ridge Research and Consulting LLC, Air Force Research Laboratory - Wright Patterson Air Force Base, Brigham Young Univ - Provo, Blue Ridge Research and Consulting, University of Utah, SRI International, Utah State University, Utah Valley University, Los Alamos National Laboratory, Professor, Graduate, United States Air Force Academy, Arizona State Univ, SiO2 NanoTech, Entrepix Inc, AFRL, Advisor, Brigham Young University- Provo, University of New Mexico, Univ of Utah, University of Wisconsin -- Madison, New Mexico Tech Physics Dept., Retired, Department of Physics and Astronomy, University of Utah, Department of Physics \& Astronomy, University of Hawai'i, JILA and University of Colorado, Boulder, National Institute of Standards and Technology, Boulder, University of Colorado, Boulder, Lawrence Berkeley National Laboratory, National Institute of Standards and Technology, Space Dynamics Lab, New Mexico Tech, BYU Professor, Brigham Young University -- Provo, Northern Arizona University, University of Colorado Boulder, Colorado State University, University of Utah, Department of Physics, New Mexico State University

  • John Colton

    Brigham Young University Dept. of Physics and Astronomy, Brigham Young University, None, The College of William and Mary/Jefferson Lab, Brigham Young University-Idaho, Blue Ridge Research and Consulting LLC, Air Force Research Laboratory - Wright Patterson Air Force Base, Brigham Young Univ - Provo, Blue Ridge Research and Consulting, University of Utah, SRI International, Utah State University, Utah Valley University, Los Alamos National Laboratory, Professor, Graduate, United States Air Force Academy, Arizona State Univ, SiO2 NanoTech, Entrepix Inc, AFRL, Advisor, Brigham Young University- Provo, University of New Mexico, Univ of Utah, University of Wisconsin -- Madison, New Mexico Tech Physics Dept., Retired, Department of Physics and Astronomy, University of Utah, Department of Physics \& Astronomy, University of Hawai'i, JILA and University of Colorado, Boulder, National Institute of Standards and Technology, Boulder, University of Colorado, Boulder, Lawrence Berkeley National Laboratory, National Institute of Standards and Technology, Space Dynamics Lab, New Mexico Tech, BYU Professor, Brigham Young University -- Provo, Northern Arizona University, University of Colorado Boulder, Colorado State University, University of Utah, Department of Physics, New Mexico State University