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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

VISAR shock velocity compares well with hydrodynamic simulations up to 20 ns when the x-ray probe begins.We linearly extrapolate the mean velocity to obtain the average conditions during the x-ray probe. Uncertainty in shock velocity is estimated to be ±1 km s−1; uncertainty in timing is ±0.5 ns. Inset: raw VISAR streak for one of two streak cameras. The bright pulse early in time comes from the drive beam. Breakout of the shock from the aluminium pusher into the deuterium occurs near the end of the drive beam, and the decaying shock velocity in D2 is extracted from the fringes shifting in time.
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f3: VISAR shock velocity compares well with hydrodynamic simulations up to 20 ns when the x-ray probe begins.We linearly extrapolate the mean velocity to obtain the average conditions during the x-ray probe. Uncertainty in shock velocity is estimated to be ±1 km s−1; uncertainty in timing is ±0.5 ns. Inset: raw VISAR streak for one of two streak cameras. The bright pulse early in time comes from the drive beam. Breakout of the shock from the aluminium pusher into the deuterium occurs near the end of the drive beam, and the decaying shock velocity in D2 is extracted from the fringes shifting in time.

Mentions: Figure 3 shows a VISAR streak record along with the extracted shock velocities for high-power laser drive conditions. Also shown are simulation results from HYDRA, a radiation-hydrodynamics code widely used for modelling inertial confinement fusion and laser-plasma experiments43. HYDRA accurately reproduces the measured late-time shock velocities when scattering is performed. Stray light from the drive beam is visible for 2 ns early in the streak. Shock breakout from the Al pusher into D2 occurs near the end of the drive beam where a discontinuous fringe shift is visible. As the shock decays, a drop in signal amplitude is visible in the raw data, since reflectivity falls as shock pressure and ionization decrease. The peak velocity immediately following shock breakout from the pusher is 22 km s−1 with pressures near 50 GPa, which decays to 14±1 km s−1 and 15+3.5/−4.5 GPa at 21 ns, the centre of the 2-ns-long x-ray probe.


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)

VISAR shock velocity compares well with hydrodynamic simulations up to 20 ns when the x-ray probe begins.We linearly extrapolate the mean velocity to obtain the average conditions during the x-ray probe. Uncertainty in shock velocity is estimated to be ±1 km s−1; uncertainty in timing is ±0.5 ns. Inset: raw VISAR streak for one of two streak cameras. The bright pulse early in time comes from the drive beam. Breakout of the shock from the aluminium pusher into the deuterium occurs near the end of the drive beam, and the decaying shock velocity in D2 is extracted from the fringes shifting in time.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: VISAR shock velocity compares well with hydrodynamic simulations up to 20 ns when the x-ray probe begins.We linearly extrapolate the mean velocity to obtain the average conditions during the x-ray probe. Uncertainty in shock velocity is estimated to be ±1 km s−1; uncertainty in timing is ±0.5 ns. Inset: raw VISAR streak for one of two streak cameras. The bright pulse early in time comes from the drive beam. Breakout of the shock from the aluminium pusher into the deuterium occurs near the end of the drive beam, and the decaying shock velocity in D2 is extracted from the fringes shifting in time.
Mentions: Figure 3 shows a VISAR streak record along with the extracted shock velocities for high-power laser drive conditions. Also shown are simulation results from HYDRA, a radiation-hydrodynamics code widely used for modelling inertial confinement fusion and laser-plasma experiments43. HYDRA accurately reproduces the measured late-time shock velocities when scattering is performed. Stray light from the drive beam is visible for 2 ns early in the streak. Shock breakout from the Al pusher into D2 occurs near the end of the drive beam where a discontinuous fringe shift is visible. As the shock decays, a drop in signal amplitude is visible in the raw data, since reflectivity falls as shock pressure and ionization decrease. The peak velocity immediately following shock breakout from the pusher is 22 km s−1 with pressures near 50 GPa, which decays to 14±1 km s−1 and 15+3.5/−4.5 GPa at 21 ns, the centre of the 2-ns-long x-ray probe.

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