High Power Laser Science and Engineering, Volume. 6, Issue 2, 02000e17(2018)

A platform for high-repetition-rate laser experiments on the Large Plasma Device

D. B. Schaeffer*, L. R. Hofer, E. N. Knall, P. V. Heuer, C. G. Constantin, and C. Niemann
Author Affiliations
  • Department of Physics and Astronomy, University of California - Los Angeles, Los Angeles, CA 90095, USA
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    Figures & Tables(8)
    Schematic of the experimental setup in the LAPD. A high-repetition-rate laser hits a plastic target embedded in an ambient magnetized plasma. The target rotates and translates in between laser shots. The resulting interaction between the laser plasma and ambient plasma is scanned with magnetic flux (‘bdot’) probes and emissive Langmuir probes in two intersecting planes, – (blue) and – (gray). The location of the high-density ambient plasma at is shown in purple.
    Langmuir probe measurements of the initial electron density and temperature in the – plane. The target is located at .
    Composite plots of (a) the magnitude of the relative magnetic field and (b) the electrostatic potential in the – and – planes at the same time . Each plane is comprised of thousands of separate laser shots, showing a high degree of reproducibility. The target is located at .
    Time series of surface plots of in the – plane, where the vertical dimension (color) is the magnitude of . The target is at and the background field along .
    Time series of contour plots of in the – plane. The target is at .
    Measured and derived quantities in the – plane at time . (a) Measured vector magnetic field . (b) Vector electric field derived from the gradient of the measured electrostatic potential. (c) -component of the current density , derived from the measured magnetic field. (d) Charge density derived from the measured potential. (e) Profiles taken along in (a)–(d). Also shown in (a)–(d) is an image of plasma self-emission at the same time.
    Measured and derived quantities in the – plane at time . (a) -component of the measured relative magnetic field . (b) Vector electric field derived from the gradient of the measured electrostatic potential. (c) Vector current density , derived from the measured magnetic field. (d) Charge density derived from the measured potential. (e) Profiles taken along in (a)–(d). Also shown in (a)–(d) is an image of plasma self-emission at the same time.
    • Table 1. Typical experimental parameters. The collisional localization is taken with respect to the mean free path between laser-ablated C ions and ambient H ions.

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      Table 1. Typical experimental parameters. The collisional localization is taken with respect to the mean free path between laser-ablated C ions and ambient H ions.

      ParameterSymbolValue
      System size [cm]50
      Amb. magnetic field [G]250
      Amb. ele. density []
      Amb. ele. temperature [eV]10
      Amb. ion temperature [eV]1
      Amb. Alfvén speed []170
      Amb. sound speed []40
      Laser energy [J]20
      Laser intensity []
      Carbon ionization4
      Carbon gyroradius [cm]31
      Laser-plasma speed []250
      Magnetic localization0.6
      Collisional localization140
      Mach number6.3
      Alfvénic Mach number1.7
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    D. B. Schaeffer, L. R. Hofer, E. N. Knall, P. V. Heuer, C. G. Constantin, C. Niemann. A platform for high-repetition-rate laser experiments on the Large Plasma Device[J]. High Power Laser Science and Engineering, 2018, 6(2): 02000e17

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    Paper Information

    Received: Dec. 1, 2017

    Accepted: Feb. 6, 2018

    Published Online: Jul. 4, 2018

    The Author Email: D. B. Schaeffer (dschaeffer@physics.ucla.edu)

    DOI:10.1017/hpl.2018.11

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