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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

Phase diagram of hydrogen.Displayed are the melting line53 (orange), the isentropes of Jupiter223 (black) and the Brown Dwarf Gliese-229b (ref. 54) (brown), the principal Hugoniot curve (magenta) and results for the first-order liquid–liquid (plasma phase) transition (green21 and blue22) together with predictions at which P–T points the system is dissociated by 50% (ref. 55) (red).
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f1: Phase diagram of hydrogen.Displayed are the melting line53 (orange), the isentropes of Jupiter223 (black) and the Brown Dwarf Gliese-229b (ref. 54) (brown), the principal Hugoniot curve (magenta) and results for the first-order liquid–liquid (plasma phase) transition (green21 and blue22) together with predictions at which P–T points the system is dissociated by 50% (ref. 55) (red).

Mentions: Dynamic experiments along the principal Hugoniot result in target conditions far from the region where a first-order liquid–liquid phase transition from molecular to conducting fluids has been predicted2122. We illustrate this in the hydrogen phase diagram shown in Fig. 1, which shows that most parts of the interiors of brown dwarfs (Gliese-229b, shown in brown) and giant planets (Jupiter, shown in black) are also at off-Hugoniot states. However, the P - T range of our experiments covers one of the most interesting parts of the Jovian interior. The flattening of the isentrope at ∼25 GPa is due to the dissociation of the hydrogen molecules. As shown by French et al.23, this is accompanied by a drastic increase in the dc electrical conductivity which represents a continuous nonmetal-to-metal transition. This result is validated with the x-ray scattering measurements presented in this study, where we find that the average ionization becomes significant just at this point on the Hugoniot curve, and coincident with dissociation. This is of great importance for planetary physics when validating equation of state (EOS) data that are used for interior223 and dynamo models24.


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)

Phase diagram of hydrogen.Displayed are the melting line53 (orange), the isentropes of Jupiter223 (black) and the Brown Dwarf Gliese-229b (ref. 54) (brown), the principal Hugoniot curve (magenta) and results for the first-order liquid–liquid (plasma phase) transition (green21 and blue22) together with predictions at which P–T points the system is dissociated by 50% (ref. 55) (red).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Phase diagram of hydrogen.Displayed are the melting line53 (orange), the isentropes of Jupiter223 (black) and the Brown Dwarf Gliese-229b (ref. 54) (brown), the principal Hugoniot curve (magenta) and results for the first-order liquid–liquid (plasma phase) transition (green21 and blue22) together with predictions at which P–T points the system is dissociated by 50% (ref. 55) (red).
Mentions: Dynamic experiments along the principal Hugoniot result in target conditions far from the region where a first-order liquid–liquid phase transition from molecular to conducting fluids has been predicted2122. We illustrate this in the hydrogen phase diagram shown in Fig. 1, which shows that most parts of the interiors of brown dwarfs (Gliese-229b, shown in brown) and giant planets (Jupiter, shown in black) are also at off-Hugoniot states. However, the P - T range of our experiments covers one of the most interesting parts of the Jovian interior. The flattening of the isentrope at ∼25 GPa is due to the dissociation of the hydrogen molecules. As shown by French et al.23, this is accompanied by a drastic increase in the dc electrical conductivity which represents a continuous nonmetal-to-metal transition. This result is validated with the x-ray scattering measurements presented in this study, where we find that the average ionization becomes significant just at this point on the Hugoniot curve, and coincident with dissociation. This is of great importance for planetary physics when validating equation of state (EOS) data that are used for interior223 and dynamo models24.

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