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

Radiation hydrodynamic simulations.Numerical simulations of the optical laser interaction with the solid carbon foil are performed using the code nym36. The simulations have been done in cylindrical 2D symmetry, using an inverse bremsstrahlung model for laser absorption and flux-limited diffusion for hot-electron transport. nym simulations do not include the effect of hot electron production at the laser spot nor the FEL heating. Panel a: contour plot of the mass density at t = 40 ps; Panel b: electron temperature at t = 40 ps after optical laser arrival time.
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f2: Radiation hydrodynamic simulations.Numerical simulations of the optical laser interaction with the solid carbon foil are performed using the code nym36. The simulations have been done in cylindrical 2D symmetry, using an inverse bremsstrahlung model for laser absorption and flux-limited diffusion for hot-electron transport. nym simulations do not include the effect of hot electron production at the laser spot nor the FEL heating. Panel a: contour plot of the mass density at t = 40 ps; Panel b: electron temperature at t = 40 ps after optical laser arrival time.

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)

Radiation hydrodynamic simulations.Numerical simulations of the optical laser interaction with the solid carbon foil are performed using the code nym36. The simulations have been done in cylindrical 2D symmetry, using an inverse bremsstrahlung model for laser absorption and flux-limited diffusion for hot-electron transport. nym simulations do not include the effect of hot electron production at the laser spot nor the FEL heating. Panel a: contour plot of the mass density at t = 40 ps; Panel b: electron temperature at t = 40 ps after optical laser arrival time.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4048912&req=5

f2: Radiation hydrodynamic simulations.Numerical simulations of the optical laser interaction with the solid carbon foil are performed using the code nym36. The simulations have been done in cylindrical 2D symmetry, using an inverse bremsstrahlung model for laser absorption and flux-limited diffusion for hot-electron transport. nym simulations do not include the effect of hot electron production at the laser spot nor the FEL heating. Panel a: contour plot of the mass density at t = 40 ps; Panel b: electron temperature at t = 40 ps after optical laser arrival time.
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