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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

Experimental set-up and timing.(a) The copper target is held at 19 K, liquefying the deuterium that is filled into the central cavity. A drive laser is incident on a 2-mm-diameter Al pusher, launching a shock wave along the axis. A probe laser irradiates a Si3N4 foil, pumping the 2,005 eV Si Ly-α transition. X-rays scattered in the forward and backward directions are spectrally dispersed with highly oriented pyrolytic graphite (HOPG) crystals whose direct view of the laser-plasma is prevented by Ni shields. (b) Cross section of the target reservoir across the thickness of the target. The target is sealed with aluminium on the front surface and a transparent quartz rear window to allow the VISAR beam to probe shock evolution. (c) Schematic of laser beam timing showing the shock drive beam (red) of 2–6 ns preceding a 2-ns probe pulse. The probe is delayed by 10–20 ns, depending on drive intensity, to allow the shock front to advance into the x-ray spectrometer view. Shorter delay times yielded higher shock pressures. (d) HYDRA simulations of mass density evolving as a function of space and time, with a lineout at the x-ray probe time of 20 ns. The compressed D2 peak (ρShock=0.54 g cm−3) has traversed into the spectrometer field of view at t=20 ns when we make the x-ray measurement. The high-density peak lagging the D2 shock front is due to the aluminium pusher, but is shielded by the x-ray window.
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f2: Experimental set-up and timing.(a) The copper target is held at 19 K, liquefying the deuterium that is filled into the central cavity. A drive laser is incident on a 2-mm-diameter Al pusher, launching a shock wave along the axis. A probe laser irradiates a Si3N4 foil, pumping the 2,005 eV Si Ly-α transition. X-rays scattered in the forward and backward directions are spectrally dispersed with highly oriented pyrolytic graphite (HOPG) crystals whose direct view of the laser-plasma is prevented by Ni shields. (b) Cross section of the target reservoir across the thickness of the target. The target is sealed with aluminium on the front surface and a transparent quartz rear window to allow the VISAR beam to probe shock evolution. (c) Schematic of laser beam timing showing the shock drive beam (red) of 2–6 ns preceding a 2-ns probe pulse. The probe is delayed by 10–20 ns, depending on drive intensity, to allow the shock front to advance into the x-ray spectrometer view. Shorter delay times yielded higher shock pressures. (d) HYDRA simulations of mass density evolving as a function of space and time, with a lineout at the x-ray probe time of 20 ns. The compressed D2 peak (ρShock=0.54 g cm−3) has traversed into the spectrometer field of view at t=20 ns when we make the x-ray measurement. The high-density peak lagging the D2 shock front is due to the aluminium pusher, but is shielded by the x-ray window.

Mentions: A series of cryogenic experiments was performed at the Janus Laser Facility at the Lawrence Livermore National Laboratory, a schematic of which is shown in Fig. 2. A drive laser was focused onto a cryogenic target, launching a shock wave into liquid deuterium at an initial density ρ0=0.17±0.004 g cm−3. A second laser, incident on a Si3N4 foil fixed to the target at an intensity of 1 × 1014 W cm−2 and wavelength of 527 nm, created an intense x-ray source by pumping the 2 keV Ly-α line in Si (ref. 34; Supplementary Fig. 1 and Supplementary Methods). These photons were collimated through a 400-μm-diameter aperture in the target, timed to probe the shock as it reached the x-ray collection ports. The x-rays were scattered from the shock front and collected through 400 μm ports at 45° and 135° from the incident photons. The probe pulse was delayed 10–20 ns after the rise of the drive beam, allowing the shock to traverse a distance of 350 μm to reach the volume accessed by the x-ray diagnostic port. The fields of view of the spectrometers were shielded with Ni-coated cones (40° opening angle) from ambient x-ray emission and stray light from both laser beams. The radiation was collected and spectrally dispersed with highly ordered pyrolytic graphite crystal spectrometers35 curved at a 107-mm radius.


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)

Experimental set-up and timing.(a) The copper target is held at 19 K, liquefying the deuterium that is filled into the central cavity. A drive laser is incident on a 2-mm-diameter Al pusher, launching a shock wave along the axis. A probe laser irradiates a Si3N4 foil, pumping the 2,005 eV Si Ly-α transition. X-rays scattered in the forward and backward directions are spectrally dispersed with highly oriented pyrolytic graphite (HOPG) crystals whose direct view of the laser-plasma is prevented by Ni shields. (b) Cross section of the target reservoir across the thickness of the target. The target is sealed with aluminium on the front surface and a transparent quartz rear window to allow the VISAR beam to probe shock evolution. (c) Schematic of laser beam timing showing the shock drive beam (red) of 2–6 ns preceding a 2-ns probe pulse. The probe is delayed by 10–20 ns, depending on drive intensity, to allow the shock front to advance into the x-ray spectrometer view. Shorter delay times yielded higher shock pressures. (d) HYDRA simulations of mass density evolving as a function of space and time, with a lineout at the x-ray probe time of 20 ns. The compressed D2 peak (ρShock=0.54 g cm−3) has traversed into the spectrometer field of view at t=20 ns when we make the x-ray measurement. The high-density peak lagging the D2 shock front is due to the aluminium pusher, but is shielded by the x-ray window.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Experimental set-up and timing.(a) The copper target is held at 19 K, liquefying the deuterium that is filled into the central cavity. A drive laser is incident on a 2-mm-diameter Al pusher, launching a shock wave along the axis. A probe laser irradiates a Si3N4 foil, pumping the 2,005 eV Si Ly-α transition. X-rays scattered in the forward and backward directions are spectrally dispersed with highly oriented pyrolytic graphite (HOPG) crystals whose direct view of the laser-plasma is prevented by Ni shields. (b) Cross section of the target reservoir across the thickness of the target. The target is sealed with aluminium on the front surface and a transparent quartz rear window to allow the VISAR beam to probe shock evolution. (c) Schematic of laser beam timing showing the shock drive beam (red) of 2–6 ns preceding a 2-ns probe pulse. The probe is delayed by 10–20 ns, depending on drive intensity, to allow the shock front to advance into the x-ray spectrometer view. Shorter delay times yielded higher shock pressures. (d) HYDRA simulations of mass density evolving as a function of space and time, with a lineout at the x-ray probe time of 20 ns. The compressed D2 peak (ρShock=0.54 g cm−3) has traversed into the spectrometer field of view at t=20 ns when we make the x-ray measurement. The high-density peak lagging the D2 shock front is due to the aluminium pusher, but is shielded by the x-ray window.
Mentions: A series of cryogenic experiments was performed at the Janus Laser Facility at the Lawrence Livermore National Laboratory, a schematic of which is shown in Fig. 2. A drive laser was focused onto a cryogenic target, launching a shock wave into liquid deuterium at an initial density ρ0=0.17±0.004 g cm−3. A second laser, incident on a Si3N4 foil fixed to the target at an intensity of 1 × 1014 W cm−2 and wavelength of 527 nm, created an intense x-ray source by pumping the 2 keV Ly-α line in Si (ref. 34; Supplementary Fig. 1 and Supplementary Methods). These photons were collimated through a 400-μm-diameter aperture in the target, timed to probe the shock as it reached the x-ray collection ports. The x-rays were scattered from the shock front and collected through 400 μm ports at 45° and 135° from the incident photons. The probe pulse was delayed 10–20 ns after the rise of the drive beam, allowing the shock to traverse a distance of 350 μm to reach the volume accessed by the x-ray diagnostic port. The fields of view of the spectrometers were shielded with Ni-coated cones (40° opening angle) from ambient x-ray emission and stray light from both laser beams. The radiation was collected and spectrally dispersed with highly ordered pyrolytic graphite crystal spectrometers35 curved at a 107-mm radius.

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