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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

Measured backscattering spectrum with theoretical fits.Fits are shown for target conditions of Te=0.15 eV and ρ/ρ0=3.2. (a) Four ionization states corresponding to Z=0.1 (blue), 0.15 (red), 0.25 (green) and 0.5 (yellow) are shown, with a best fit found for ne=2.4 × 1022 cm−3 and Z=0.15±0.08. (b) Theoretical fits for Z=0.15 using the SP (red) and EK (blue) models for ionization potential depression. Solid lines correspond to the total spectrum and dashed to the elastic and bound-free scattering contributions without free–free scattering. Both models result in best fit values for ionization of Z=0.15.
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f5: Measured backscattering spectrum with theoretical fits.Fits are shown for target conditions of Te=0.15 eV and ρ/ρ0=3.2. (a) Four ionization states corresponding to Z=0.1 (blue), 0.15 (red), 0.25 (green) and 0.5 (yellow) are shown, with a best fit found for ne=2.4 × 1022 cm−3 and Z=0.15±0.08. (b) Theoretical fits for Z=0.15 using the SP (red) and EK (blue) models for ionization potential depression. Solid lines correspond to the total spectrum and dashed to the elastic and bound-free scattering contributions without free–free scattering. Both models result in best fit values for ionization of Z=0.15.

Mentions: Figure 5 shows the 135° backscattered spectrum from another shot using a 4-ns laser drive, and a probe beam delay of 15 ns. HYDRA calculations using an intensity profile matched to the velocity measurements shown above predict pressures of 16 GPa and compressions of 3.2+0.2/−0.4, producing target conditions very close to those achieved in the plasmon scattering case. The ratio of elastic to inelastic scattering is strongly dependent on the ionization of the target; with increasing average ionization, the inelastic scattering contribution from free electrons grows relative to the remaining elastic signal. Fits are shown in Fig. 5a for ionizations Z=0.1–0.5 and a best fit is achieved for ne=2.4 × 1022 cm−3. This corresponds Z=0.15±0.08, in good agreement with the plasmon data. At these conditions, the scattering parameter is α=0.63.


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)

Measured backscattering spectrum with theoretical fits.Fits are shown for target conditions of Te=0.15 eV and ρ/ρ0=3.2. (a) Four ionization states corresponding to Z=0.1 (blue), 0.15 (red), 0.25 (green) and 0.5 (yellow) are shown, with a best fit found for ne=2.4 × 1022 cm−3 and Z=0.15±0.08. (b) Theoretical fits for Z=0.15 using the SP (red) and EK (blue) models for ionization potential depression. Solid lines correspond to the total spectrum and dashed to the elastic and bound-free scattering contributions without free–free scattering. Both models result in best fit values for ionization of Z=0.15.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: Measured backscattering spectrum with theoretical fits.Fits are shown for target conditions of Te=0.15 eV and ρ/ρ0=3.2. (a) Four ionization states corresponding to Z=0.1 (blue), 0.15 (red), 0.25 (green) and 0.5 (yellow) are shown, with a best fit found for ne=2.4 × 1022 cm−3 and Z=0.15±0.08. (b) Theoretical fits for Z=0.15 using the SP (red) and EK (blue) models for ionization potential depression. Solid lines correspond to the total spectrum and dashed to the elastic and bound-free scattering contributions without free–free scattering. Both models result in best fit values for ionization of Z=0.15.
Mentions: Figure 5 shows the 135° backscattered spectrum from another shot using a 4-ns laser drive, and a probe beam delay of 15 ns. HYDRA calculations using an intensity profile matched to the velocity measurements shown above predict pressures of 16 GPa and compressions of 3.2+0.2/−0.4, producing target conditions very close to those achieved in the plasmon scattering case. The ratio of elastic to inelastic scattering is strongly dependent on the ionization of the target; with increasing average ionization, the inelastic scattering contribution from free electrons grows relative to the remaining elastic signal. Fits are shown in Fig. 5a for ionizations Z=0.1–0.5 and a best fit is achieved for ne=2.4 × 1022 cm−3. This corresponds Z=0.15±0.08, in good agreement with the plasmon data. At these conditions, the scattering parameter is α=0.63.

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