Optical spectroscopy of plasma impurities in a megajoule-class Dense Plasma Focus

POSTER

Abstract

A Dense Plasma Focus (DPF1) such as the MegaJOuLe Neutron Imaging Radiography2 (MJOLNIR) is a coaxial deuterium plasma railgun that ends in a z-pinch to produce energetic neutrons. Careful consideration must be given to tracking and maintaining plasma temperatures that maximize neutron yield. Plasma contamination is one mechanism for reducing temperature and thereby reducing fusion events. It has been shown that copper from the anode is sputtered into the plasma during a DPF shot3. However, certain dopants may also increase neutron yield given the proper conditions4. The spatiotemporal location of impurities can be monitored with a spectrometer and compared with numerical results to explore the effect on neutron yield. We present a multi-point, time-gated optical spectrometer capable of differentiating these various mechanisms. Simulations are used to determine laboratory placement of a linear, 27-fiber bundle plug outside the MJOLNIR target chamber. On the detector end a micro-channel plate (MCP) provides light amplification and can be gated for a minimum of 10 nanosecond, which resolves the microsecond DPF dynamics.

*Prepared by LLNL under Contract DE-AC52-07NA27344. And also supported by the University of Rochester’s Laboratory for Laser Energetics’ Horton Fellowship.

Publication: 1. J. W. Mather, "Investigation of the high-energy acceleration mode in the coaxial gun", Phys. Fluids, vol. 7, no. 11, pp. S28, 1964.
2. Schmidt, A., Anaya, E., Anderson, M., Angus, J., Chapman, S., Cooper, C., Drury, O., Goyon, C., Hawkins, S., Higginson, D., Holod, I., Koh, E., Link, A., Max, D., McMahon, M., Mitrani, J., Podpaly, Y., Povilus, A. and Van Lue, D., 2021. First Experiments and Radiographs on the MegaJOuLe Neutron Imaging Radiography (MJOLNIR) Dense Plasma Focus. IEEE Transactions on Plasma Science, 49(11), pp.3299-3306.
3. J. Appl. Phys. 124, 233301 (2018); https://doi.org/10.1063/1.5051665
4. R. Verma, P. Lee, S. Lee, S. V. Springham, T. L. Tan, R. S. Rawat, and M. Krishnan, " Order of magnitude enhancement in neutron emission with deuterium-krypton admixture operation in miniature plasma focus device," Appl. Phys. Lett. 93, 101501 (2008). https://doi.org/10.1063/1.2979683

Presenters

  • James Young

    • University of Rochester

Authors

  • James Young

    • University of Rochester

  • Clement S Goyon

    • Lawrence Livermore National Laboratory
    • Lawrence Livermore Natl Lab

  • Aduragbemi A Jibodu

    • Lawrence Livermore National Laboratory

  • Anthony J Link

    • Lawrence Livermore Natl Lab
    • Lawrence Livermore National Laboratory

  • Sheng Jiang

    • Lawrence Livermore Natl Lab
    • Lawrence Livermore National Laboratory

  • Paul C Campbell

    • Lawrence Livermore National Laboratory

  • Sophia V Rocco

    • Lawrence Livermore National Laboratory
    • Lawrence Livermore Natl Lab

  • Steven F Chapman

    • Lawrence Livermore National Laboratory
    • Lawrence Livermore National Lab
    • Lawrence Livermore Natl Lab
    • LLNL

  • Owen B Drury

    • Lawrence Livermore National Laboratory
    • Lawrence Livermore Natl Lab

  • Christopher M Cooper

    • Lawrence Livermore National Laboratory
    • Lawrence Livermore Natl Lab
    • Lawrence Livermore National Lab
    • LLNL

  • Pierre-Alexandre Gourdain

    • University of Rochester

  • Andrea E Schmidt

    • Lawrence Livermore National Laboratory