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X-ray scattering measurements of dissociation-induced metallization of dynamically compressed deuterium.

Davis P, Döppner T, Rygg JR, Fortmann C, Divol L, Pak A, Fletcher L, Becker A, Holst B, Sperling P, Redmer R, Desjarlais MP, Celliers P, Collins GW, Landen OL, Falcone RW, Glenzer SH - Nat Commun (2016)

Bottom Line: Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades.Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium.Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us to extract ionization state as a function of compression.

View Article: PubMed Central - PubMed

Affiliation: University of California, Berkeley, California 94720, USA.

ABSTRACT
Hydrogen, the simplest element in the universe, has a surprisingly complex phase diagram. Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades. While sophisticated static experiments have probed hydrogen's structure at ever higher pressures, studies examining the higher-temperature regime using dynamic compression have mostly been limited to optical measurement techniques. Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium. Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us to extract ionization state as a function of compression. The onset of ionization occurs close in pressure to where density functional theory-molecular dynamics (DFT-MD) simulations show molecular dissociation, suggesting hydrogen transitions from a molecular and insulating fluid to a conducting state without passing through an intermediate atomic phase.

No MeSH data available.


Related in: MedlinePlus

Average ionization of D2 plotted as a function of compression along the single-shock Hugoniot.Values of ionization inferred from plasmon measurements are shown as red squares, measurements using Compton scattering are shown as blue circles, and pressures from quotidian EOS (QEOS) are indicated for each data point. Ionization degree calculated with Thomas–Fermi theory is shown as a dashed line, while average-atom calculations are shown between a lower bound of Te=0.1 eV and an upper bound of Te=0.5 eV as a shaded region. The dark red line shows the molecular dissociation fraction calculated from density functional molecular dynamics simulations along the principal Hugoniot and the dotted line shows a similar dissociation calculation with the chemical picture code FVT. Measurements indicate a sharp increase in ionization near 3 × compression, consistent with the DFT-MD calculated dissociated fraction.
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f6: Average ionization of D2 plotted as a function of compression along the single-shock Hugoniot.Values of ionization inferred from plasmon measurements are shown as red squares, measurements using Compton scattering are shown as blue circles, and pressures from quotidian EOS (QEOS) are indicated for each data point. Ionization degree calculated with Thomas–Fermi theory is shown as a dashed line, while average-atom calculations are shown between a lower bound of Te=0.1 eV and an upper bound of Te=0.5 eV as a shaded region. The dark red line shows the molecular dissociation fraction calculated from density functional molecular dynamics simulations along the principal Hugoniot and the dotted line shows a similar dissociation calculation with the chemical picture code FVT. Measurements indicate a sharp increase in ionization near 3 × compression, consistent with the DFT-MD calculated dissociated fraction.

Mentions: Figure 6 summarizes measurements of ionization across several shock-drive and probe delay conditions producing compressions between ρ/ρ0=2.8 and ρ/ρ0=4.05. Measured ionization states for both forward and backscattered configurations are shown as a function of compression, along with predicted ionizations from several models. The compression values for the backscattering data points and the lowest compression case, where velocity measurements are not possible below the onset of optical reflectivity, were determined using hydrodynamic calculations benchmarked to VISAR measurements. The error bars in compression for these points include a 20% uncertainty in drive intensity and uncertainty between EOS models at the relevant pressures. The data indicate a sharp onset of ionization between 3 and 3.5 times compression.


X-ray scattering measurements of dissociation-induced metallization of dynamically compressed deuterium.

Davis P, Döppner T, Rygg JR, Fortmann C, Divol L, Pak A, Fletcher L, Becker A, Holst B, Sperling P, Redmer R, Desjarlais MP, Celliers P, Collins GW, Landen OL, Falcone RW, Glenzer SH - Nat Commun (2016)

Average ionization of D2 plotted as a function of compression along the single-shock Hugoniot.Values of ionization inferred from plasmon measurements are shown as red squares, measurements using Compton scattering are shown as blue circles, and pressures from quotidian EOS (QEOS) are indicated for each data point. Ionization degree calculated with Thomas–Fermi theory is shown as a dashed line, while average-atom calculations are shown between a lower bound of Te=0.1 eV and an upper bound of Te=0.5 eV as a shaded region. The dark red line shows the molecular dissociation fraction calculated from density functional molecular dynamics simulations along the principal Hugoniot and the dotted line shows a similar dissociation calculation with the chemical picture code FVT. Measurements indicate a sharp increase in ionization near 3 × compression, consistent with the DFT-MD calculated dissociated fraction.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835540&req=5

f6: Average ionization of D2 plotted as a function of compression along the single-shock Hugoniot.Values of ionization inferred from plasmon measurements are shown as red squares, measurements using Compton scattering are shown as blue circles, and pressures from quotidian EOS (QEOS) are indicated for each data point. Ionization degree calculated with Thomas–Fermi theory is shown as a dashed line, while average-atom calculations are shown between a lower bound of Te=0.1 eV and an upper bound of Te=0.5 eV as a shaded region. The dark red line shows the molecular dissociation fraction calculated from density functional molecular dynamics simulations along the principal Hugoniot and the dotted line shows a similar dissociation calculation with the chemical picture code FVT. Measurements indicate a sharp increase in ionization near 3 × compression, consistent with the DFT-MD calculated dissociated fraction.
Mentions: Figure 6 summarizes measurements of ionization across several shock-drive and probe delay conditions producing compressions between ρ/ρ0=2.8 and ρ/ρ0=4.05. Measured ionization states for both forward and backscattered configurations are shown as a function of compression, along with predicted ionizations from several models. The compression values for the backscattering data points and the lowest compression case, where velocity measurements are not possible below the onset of optical reflectivity, were determined using hydrodynamic calculations benchmarked to VISAR measurements. The error bars in compression for these points include a 20% uncertainty in drive intensity and uncertainty between EOS models at the relevant pressures. The data indicate a sharp onset of ionization between 3 and 3.5 times compression.

Bottom Line: Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades.Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium.Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us to extract ionization state as a function of compression.

View Article: PubMed Central - PubMed

Affiliation: University of California, Berkeley, California 94720, USA.

ABSTRACT
Hydrogen, the simplest element in the universe, has a surprisingly complex phase diagram. Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades. While sophisticated static experiments have probed hydrogen's structure at ever higher pressures, studies examining the higher-temperature regime using dynamic compression have mostly been limited to optical measurement techniques. Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium. Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us to extract ionization state as a function of compression. The onset of ionization occurs close in pressure to where density functional theory-molecular dynamics (DFT-MD) simulations show molecular dissociation, suggesting hydrogen transitions from a molecular and insulating fluid to a conducting state without passing through an intermediate atomic phase.

No MeSH data available.


Related in: MedlinePlus