Measurement of temperature and density using non-collective X-ray Thomson scattering in pulsed power produced warm dense plasmas

Journal Article · 30 May 2018 · Scientific Reports

DOI: https://doi.org/10.1038/s41598-018-26608-w · OSTI ID:1466942

Valenzuela, J. C.  ^[1]; Krauland, C. ^[1]; Mariscal, D. ^[1]; Krasheninnikov, I. ^[1]; Niemann, C. ^[2]; Ma, T. ^[3]; Mabey, P. ^[4]; Gregori, G. ^[4]; Wiewior, P. ^[5]; Covington, A. M. ^[5]; Beg, F. N. ^[1]

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1. Univ. of California, San Diego, CA (United States). Center for Energy Research
2. Univ. of California, Los Angeles, CA (United States). Dept. of Physics and Astronomy
3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
4. Univ. of Oxford (United Kingdom). Dept. of Physics
5. Univ. of Nevada, Reno, NV (United States). Nevada Terawatt Facility, Dept. of Physics

We present the first experimental measurement of temperature and density of a warm dense plasma produced by a pulsed power driver at the Nevada Terawatt Facility (NTF). In the early phases of discharge, most of the mass remains in the core, and it has been challenging to diagnose with traditional methods, e.g. optical probing, because of the high density and low temperature. Accurate knowledge of the transport coefficients as well as the thermodynamic state of the plasma is important to precisely test or develop theoretical models. Here, we have used spectrally resolved non-collective X-ray Thomson scattering to characterize the dense core region. We used a graphite load driven by the Zebra current generator (0.6 MA in 200 ns rise time) and the Ti He-α line produced by irradiating a Ti target with the Leopard laser (30 J, 0.8 ns) as an X-ray probing source. Using this configuration, we obtained a signal-to-noise ratio ~2.5 for the scattered signal. Finally, by fitting the experimental data with predicted spectra, we measured T = 2±1.9 eV, ρ = 0.6±0.5 gr/cc, 70 ns into the current pulse. The complexity of the dense core is revealed by the electrons in the dense core that are found to be degenerate and weakly coupled, while the ions remain highly coupled.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-07NA27344; NA0001995; LFR-17-449059; EP/M022331; EP/N014472/1
• OSTI ID: 1466942
• Report Number(s): LLNL-JRNL-755378; 942273
• Journal Information: Scientific Reports, Vol. 8, Issue 1; ISSN 2045-2322
• Publisher: Nature Publishing GroupCopyright Statement
• Country of Publication: United States
• Language: English