Limits...
Evidence for a glassy state in strongly driven carbon.

Brown CR, Gericke DO, Cammarata M, Cho BI, Döppner T, Engelhorn K, Förster E, Fortmann C, Fritz D, Galtier E, Glenzer SH, Harmand M, Heimann P, Kugland NL, Lamb DQ, Lee HJ, Lee RW, Lemke H, Makita M, Moinard A, Murphy CD, Nagler B, Neumayer P, Plagemann KU, Redmer R, Riley D, Rosmej FB, Sperling P, Toleikis S, Vinko SM, Vorberger J, White S, White TG, Wünsch K, Zastrau U, Zhu D, Tschentscher T, Gregori G - Sci Rep (2014)

Bottom Line: Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers.Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions.The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK [2] Plasma Physics Department, AWE plc., Aldermaston, Reading RG7 4PR, UK [3] Plasma Physics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK.

ABSTRACT
Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

No MeSH data available.


Related in: MedlinePlus

Experimental setup.This work was been performed at at the LCLS XPP instrument. A 300 fs long, 10 mJ Ti:Sapphire laser (operating at wavelength of 800 nm) was focused onto a 1 μm thick graphite foil, mounted on a rastering stage within a vacuum chamber, to a focal spot-size of 80 μm diameter resulting in an intensity on target of 1015 W/cm2. The shocked heated carbon foil was then illuminated by the FEL probe beam (operating at 8 keV, with ~1 mJ energy in a 80 fs long pulse) propagating nearly collinearly with the optical laser pulse. The x-ray spot size was around 20 μm diameter, focused using a series of beryllium refractive lenses. The inset shows the spectrum of the x-ray beam as it reaches the sample, as well as the measured scattering spectrum at θ = 50°. Temporal synchronization and spatial overlap of the optical and x ray beams was achieved through the use of optical damage shadowgraphy35. The scattered x-rays are collected using a highly oriented pyrolytic graphite (HOPG) crystal spectrometer in von Hàmos geometry. Details of the crystal spectrometer calibration are given in Ref. [23]. Data is then recorded onto a high quantum efficiency, high repetition rate pixel-array detector (CSPAD). An example of the raw data recorded on the detector is shown in the figure. The diffracted photon energy increases from bottom to top in the image. From the raw image, the spectrum was obtained by integrating along the non-dispersive direction, but only in a narrow central strip, as indicated in the figure. This is to minimize spectral broadening associated to crystal aberrations, as discussed in Ref. [23]. The spectrometer, including detector, was mounted to a six-axis robotic arm, enabling the angle at which the scattered radiation was measured to be varied during the experiment (θ = 20°, 35°, 50°, 130°). The HOPG crystal was large enough to collect rays from ±5° of the nominal scattering angle. The polarization of the x-ray beam was at 90° to the angle of scatter, maximizing the scattering efficiency and obviating any polarization effects on the scattered radiation.
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f1: Experimental setup.This work was been performed at at the LCLS XPP instrument. A 300 fs long, 10 mJ Ti:Sapphire laser (operating at wavelength of 800 nm) was focused onto a 1 μm thick graphite foil, mounted on a rastering stage within a vacuum chamber, to a focal spot-size of 80 μm diameter resulting in an intensity on target of 1015 W/cm2. The shocked heated carbon foil was then illuminated by the FEL probe beam (operating at 8 keV, with ~1 mJ energy in a 80 fs long pulse) propagating nearly collinearly with the optical laser pulse. The x-ray spot size was around 20 μm diameter, focused using a series of beryllium refractive lenses. The inset shows the spectrum of the x-ray beam as it reaches the sample, as well as the measured scattering spectrum at θ = 50°. Temporal synchronization and spatial overlap of the optical and x ray beams was achieved through the use of optical damage shadowgraphy35. The scattered x-rays are collected using a highly oriented pyrolytic graphite (HOPG) crystal spectrometer in von Hàmos geometry. Details of the crystal spectrometer calibration are given in Ref. [23]. Data is then recorded onto a high quantum efficiency, high repetition rate pixel-array detector (CSPAD). An example of the raw data recorded on the detector is shown in the figure. The diffracted photon energy increases from bottom to top in the image. From the raw image, the spectrum was obtained by integrating along the non-dispersive direction, but only in a narrow central strip, as indicated in the figure. This is to minimize spectral broadening associated to crystal aberrations, as discussed in Ref. [23]. The spectrometer, including detector, was mounted to a six-axis robotic arm, enabling the angle at which the scattered radiation was measured to be varied during the experiment (θ = 20°, 35°, 50°, 130°). The HOPG crystal was large enough to collect rays from ±5° of the nominal scattering angle. The polarization of the x-ray beam was at 90° to the angle of scatter, maximizing the scattering efficiency and obviating any polarization effects on the scattered radiation.

Mentions: To overcome these limitations, we used here two nearly collinear laser beams to create a unique dense matter regime in an experiment performed at the Linac Coherent Light Source14. First we illuminated a 1 μm thin graphite foil with an optical laser (see Figure 1 for details of the experimental setup). The laser was focused with a relatively large focal spot of 80 μm diameter and a moderate intensity of ~1015 W/cm2. The corresponding ablation pressure of ~30 Mbar15 launches a shock wave through the carbon sample. The shock compresses the sample to densities of ρ ~ 2.5–5 g/cm3 and heats it to temperatures T ~ 5, 000–10, 000 K, inducing the carbon to melt (see also Ref. [2] for the high pressure phase diagram of carbon). Figure 2 shows an example for the density and temperature profiles after 40 ps as obtained from modelling the radiation driven hydrodynamics. After a time of t ~ 40–50 ps, the shock reaches the opposite side of the foil and breaks out. This long wavelength, optical laser also produces a large number of nonthermal electrons having a high-energy tail with a temperature of ~7.5–14 keV16. These electrons will significantly enhance the ionization degree of the carbon sample by electron impact.


Evidence for a glassy state in strongly driven carbon.

Brown CR, Gericke DO, Cammarata M, Cho BI, Döppner T, Engelhorn K, Förster E, Fortmann C, Fritz D, Galtier E, Glenzer SH, Harmand M, Heimann P, Kugland NL, Lamb DQ, Lee HJ, Lee RW, Lemke H, Makita M, Moinard A, Murphy CD, Nagler B, Neumayer P, Plagemann KU, Redmer R, Riley D, Rosmej FB, Sperling P, Toleikis S, Vinko SM, Vorberger J, White S, White TG, Wünsch K, Zastrau U, Zhu D, Tschentscher T, Gregori G - Sci Rep (2014)

Experimental setup.This work was been performed at at the LCLS XPP instrument. A 300 fs long, 10 mJ Ti:Sapphire laser (operating at wavelength of 800 nm) was focused onto a 1 μm thick graphite foil, mounted on a rastering stage within a vacuum chamber, to a focal spot-size of 80 μm diameter resulting in an intensity on target of 1015 W/cm2. The shocked heated carbon foil was then illuminated by the FEL probe beam (operating at 8 keV, with ~1 mJ energy in a 80 fs long pulse) propagating nearly collinearly with the optical laser pulse. The x-ray spot size was around 20 μm diameter, focused using a series of beryllium refractive lenses. The inset shows the spectrum of the x-ray beam as it reaches the sample, as well as the measured scattering spectrum at θ = 50°. Temporal synchronization and spatial overlap of the optical and x ray beams was achieved through the use of optical damage shadowgraphy35. The scattered x-rays are collected using a highly oriented pyrolytic graphite (HOPG) crystal spectrometer in von Hàmos geometry. Details of the crystal spectrometer calibration are given in Ref. [23]. Data is then recorded onto a high quantum efficiency, high repetition rate pixel-array detector (CSPAD). An example of the raw data recorded on the detector is shown in the figure. The diffracted photon energy increases from bottom to top in the image. From the raw image, the spectrum was obtained by integrating along the non-dispersive direction, but only in a narrow central strip, as indicated in the figure. This is to minimize spectral broadening associated to crystal aberrations, as discussed in Ref. [23]. The spectrometer, including detector, was mounted to a six-axis robotic arm, enabling the angle at which the scattered radiation was measured to be varied during the experiment (θ = 20°, 35°, 50°, 130°). The HOPG crystal was large enough to collect rays from ±5° of the nominal scattering angle. The polarization of the x-ray beam was at 90° to the angle of scatter, maximizing the scattering efficiency and obviating any polarization effects on the scattered radiation.
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Related In: Results  -  Collection

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f1: Experimental setup.This work was been performed at at the LCLS XPP instrument. A 300 fs long, 10 mJ Ti:Sapphire laser (operating at wavelength of 800 nm) was focused onto a 1 μm thick graphite foil, mounted on a rastering stage within a vacuum chamber, to a focal spot-size of 80 μm diameter resulting in an intensity on target of 1015 W/cm2. The shocked heated carbon foil was then illuminated by the FEL probe beam (operating at 8 keV, with ~1 mJ energy in a 80 fs long pulse) propagating nearly collinearly with the optical laser pulse. The x-ray spot size was around 20 μm diameter, focused using a series of beryllium refractive lenses. The inset shows the spectrum of the x-ray beam as it reaches the sample, as well as the measured scattering spectrum at θ = 50°. Temporal synchronization and spatial overlap of the optical and x ray beams was achieved through the use of optical damage shadowgraphy35. The scattered x-rays are collected using a highly oriented pyrolytic graphite (HOPG) crystal spectrometer in von Hàmos geometry. Details of the crystal spectrometer calibration are given in Ref. [23]. Data is then recorded onto a high quantum efficiency, high repetition rate pixel-array detector (CSPAD). An example of the raw data recorded on the detector is shown in the figure. The diffracted photon energy increases from bottom to top in the image. From the raw image, the spectrum was obtained by integrating along the non-dispersive direction, but only in a narrow central strip, as indicated in the figure. This is to minimize spectral broadening associated to crystal aberrations, as discussed in Ref. [23]. The spectrometer, including detector, was mounted to a six-axis robotic arm, enabling the angle at which the scattered radiation was measured to be varied during the experiment (θ = 20°, 35°, 50°, 130°). The HOPG crystal was large enough to collect rays from ±5° of the nominal scattering angle. The polarization of the x-ray beam was at 90° to the angle of scatter, maximizing the scattering efficiency and obviating any polarization effects on the scattered radiation.
Mentions: To overcome these limitations, we used here two nearly collinear laser beams to create a unique dense matter regime in an experiment performed at the Linac Coherent Light Source14. First we illuminated a 1 μm thin graphite foil with an optical laser (see Figure 1 for details of the experimental setup). The laser was focused with a relatively large focal spot of 80 μm diameter and a moderate intensity of ~1015 W/cm2. The corresponding ablation pressure of ~30 Mbar15 launches a shock wave through the carbon sample. The shock compresses the sample to densities of ρ ~ 2.5–5 g/cm3 and heats it to temperatures T ~ 5, 000–10, 000 K, inducing the carbon to melt (see also Ref. [2] for the high pressure phase diagram of carbon). Figure 2 shows an example for the density and temperature profiles after 40 ps as obtained from modelling the radiation driven hydrodynamics. After a time of t ~ 40–50 ps, the shock reaches the opposite side of the foil and breaks out. This long wavelength, optical laser also produces a large number of nonthermal electrons having a high-energy tail with a temperature of ~7.5–14 keV16. These electrons will significantly enhance the ionization degree of the carbon sample by electron impact.

Bottom Line: Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers.Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions.The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK [2] Plasma Physics Department, AWE plc., Aldermaston, Reading RG7 4PR, UK [3] Plasma Physics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK.

ABSTRACT
Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

No MeSH data available.


Related in: MedlinePlus