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Your search keyword '"Witte, B. B. L."' showing total 17 results
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17 results on '"Witte, B. B. L."'

1. Setup for meV-resolution inelastic X-ray scattering measurements at the Matter in Extreme Conditions Endstation at the LCLS

Author

McBride, E. E., White, T. G., Descamps, A., Fletcher, L. B., Appel, K., Condamine, F., Curry, C. B., Dallari, F., Funk, S., Galtier, E., Gauthier, M., Goede, S., Kim, J. B., Lee, H. J., Ofori-Okai, B. K., Oliver, M., Rigby, A., Schoenwaelder, C., Sun, P., Tschentscher, Th., Witte, B. B. L., Zastrau, U., Gregori, G., Nagler, B., Hastings, J., Glenzer, S. H., and Monaco, G.

Subjects
Physics - Instrumentation and Detectors
Abstract

We describe a setup for performing inelastic X-ray scattering measurements at the Matter in Extreme Conditions (MEC) endstation of the Linac Coherent Light Source (LCLS). This technique is capable of performing high-, meV-resolution measurements of dynamic ion features in both crystalline and non-crystalline materials. A four-bounce silicon (533) monochromator was used in conjunction with three silicon (533) diced crystal analyzers to provide an energy resolution of ~50 meV over a range of ~500 meV in single shot measurements. In addition to the instrument resolution function, we demonstrate the measurement of longitudinal acoustic phonon modes in polycrystalline diamond. Furthermore, this setup may be combined with the high intensity laser drivers available at MEC to create warm dense matter, and subsequently measure ion acoustic modes., Comment: Proceedings for High Temperature Plasma Diagnostics

Published
2018
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5. Observing the onset of pressure-driven K-shell delocalization

Author

Döppner, T., primary, Bethkenhagen, M., additional, Kraus, D., additional, Neumayer, P., additional, Chapman, D. A., additional, Bachmann, B., additional, Baggott, R. A., additional, Böhme, M. P., additional, Divol, L., additional, Falcone, R. W., additional, Fletcher, L. B., additional, Landen, O. L., additional, MacDonald, M. J., additional, Saunders, A. M., additional, Schörner, M., additional, Sterne, P. A., additional, Vorberger, J., additional, Witte, B. B. L., additional, Yi, A., additional, Redmer, R., additional, Glenzer, S. H., additional, and Gericke, D. O., additional

Published
2023
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6. Observing the onset of pressure-driven K-shell delocalization

Author

Döppner, T., Bethkenhagen, M., (0000-0002-6350-4180) Kraus, D., Neumayer, P., Chapman, D. A., Bachmann, B., Baggott, R. A., (0000-0003-0290-3628) Böhme, M., Divol, L., Falcone, R. W., Fletcher, L. B., Landen, O. L., Macdonald, M. J., Saunders, A. M., Schörner, M., Sterne, P. A., (0000-0001-5926-9192) Vorberger, J., Witte, B. B. L., Yi, A., Redmer, R., Glenzer, S. H., Gericke, D. O., Döppner, T., Bethkenhagen, M., (0000-0002-6350-4180) Kraus, D., Neumayer, P., Chapman, D. A., Bachmann, B., Baggott, R. A., (0000-0003-0290-3628) Böhme, M., Divol, L., Falcone, R. W., Fletcher, L. B., Landen, O. L., Macdonald, M. J., Saunders, A. M., Schörner, M., Sterne, P. A., (0000-0001-5926-9192) Vorberger, J., Witte, B. B. L., Yi, A., Redmer, R., Glenzer, S. H., and Gericke, D. O.

Abstract

The gravitational pressure in many astrophysical objects exceeds one Gigabar (1 billion atmospheres) for a large part of their interior. At theses extreme conditions, matter is compressed to a state where the distance between nuclei becomes as small as the K-shell, containing the most tightly bound electrons, of light elements. These strong interactions of neighbouring particles modify existing bound states and, above a certain pressure, drive the electrons into a delocalised, conducting state. Both modified bound states and increased ionisation significantly affect the equation of state and radiation transport which, in turn, determine the evolution and structure of these objects. Still, our understanding of this transition is far from satisfying and, up to now, experimental data are sparse due to the extreme conditions required. Here, we report on an experiment that creates and diagnoses matter at pressures above 3 Gigabar by utilising the full capabilities of the National Ignition Facility where 184 laser beams were used to implode a beryllium shell, generating highly compressed states. Bright X-ray flashes enable precision radiography and X-ray Thomson scattering measurements revealing both the macroscopic and the microscopic state of the highly compressed beryllium. The inelastic scattering component shows clear signs of quantum degenerate electrons with the density reaching up to 30 times compression, and a temperature of around 2 million Kelvin. At the most extreme conditions, we also observe strongly reduced elastic scattering, which mainly originates from bound K-shell electrons. We attribute this reduction to the onset of delocalisation of the remaining K-shell electron. With this interpretation, the ion charge inferred from the scattering data agrees well with ab initio simulations, but it is significantly higher than widely used models predict. Our results yield a profound understanding of matter in the interior of brown and white dwarfs and will enhance

Published
2023

7. Ab initio study of shock-compressed copper

Author

Schörner, M., Witte, B. B. L., Baczewski, A. D., (0000-0001-9162-262X) Cangi, A., Redmer, R., Schörner, M., Witte, B. B. L., Baczewski, A. D., (0000-0001-9162-262X) Cangi, A., and Redmer, R.

Abstract

We investigate shock-compressed copper in the warm dense matter regime by means of density functional theory molecular dynamics simulations. We use neural-network-driven interatomic potentials to increase the size of the simulation box and extract thermodynamic properties in the hydrodynamic limit. We show the agreement of our simulation results with experimental data for solid copper at ambient conditions and liquid copper near the melting point under ambient pressure. Furthermore, a thorough analysis of the dynamic ion-ion structure factor in shock-compressed copper is performed and the adiabatic speed of sound is extracted and compared with experimental data.

Published
2022

8. Ionization in high-density plasmas: an ab initio study for carbon at Gbar pressures

Author

Bethkenhagen, M., Witte, B. B. L., Röpke, G., Döppner, T., Kraus, D., Glenzer, S. H., and Redmer, R.

Abstract

We apply density functional theory molecular dynamics (DFT-MD) simulations to calculate the ionization degree of plasmas in the warm dense matter regime. Standard descriptions of the ionization potential depression (IPD) have been challenged recently by experiments approaching unprecedentedly high densities indicating that improved IPD models are required to describe warm dense matter. We propose a novel ab initio method to calculate the ionization degree directly from the dynamic electrical conductivity using the Thomas-Reiche-Kuhn (TRK) sum rule. This approach is demonstrated for carbon at a temperature of 100 eV and pressures in the Gbar range. We find substantial deviations from widely applied IPD models like Stewart-Pyatt and Ecker-Kröll implying that condensed matter and quantum effects like band structure and Pauli blocking need to be included explicitly in ionization models. Our results will help to precisely model matter under conditions occurring, e.g., during inertial confined fusion implosions or inside astrophysical objects such as brown dwarfs and low-mass stars.

Published
2020

9. Erratum: 'Setup for meV-resolution inelastic X-ray scattering measurements and X-ray diffraction at the Matter in Extreme Conditions endstation at the Linac Coherent Light Source' (Review Of Scientific Instruments (2018) 89 (10F104) DOI: 10.1063/1.5039329)

Author

Mcbride, E. E., White, T. G., Descamps, A., Fletcher, L. B., Appel, K., Condamine, F., Curry, C. B., Dallari, F., Funk, S., Galtier, E., Gamboa, E. J., Gauthier, M., Goede, S., Kim, J. B., Lee, H. J., Ofori-Okai, B. K., Oliver, M., Rigby, A., Schoenwaelder, C., Sun, P., Tschentscher, Th., Witte, B. B. L., Zastrau, U., Gregori, G., Nagler, B., Hastings, J., Glenzer, S. H., and Monaco, G.

Published
2018

11. Measurements of the momentum-dependence of plasmonic excitations in matter around 1 Mbar using an X-ray free electron laser

Author

Preston, T. R., primary, Appel, K., additional, Brambrink, E., additional, Chen, B., additional, Fletcher, L. B., additional, Fortmann-Grote, C., additional, Glenzer, S. H., additional, Granados, E., additional, Göde, S., additional, Konôpková, Z., additional, Lee, H. J., additional, Marquardt, H., additional, McBride, E. E., additional, Nagler, B., additional, Nakatsutsumi, M., additional, Sperling, P., additional, Witte, B. B. L., additional, and Zastrau, U., additional

Published
2019
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12. Erratum: “Setup for meV-resolution inelastic X-ray scattering measurements and X-ray diffraction at the Matter in Extreme Conditions endstation at the Linac Coherent Light Source” [Rev. Sci. Instrum. 89, 10F104 (2018)]

Author

McBride, E. E., primary, White, T. G., additional, Descamps, A., additional, Fletcher, L. B., additional, Appel, K., additional, Condamine, F., additional, Curry, C. B., additional, Dallari, F., additional, Funk, S., additional, Galtier, E., additional, Gamboa, E. J., additional, Gauthier, M., additional, Goede, S., additional, Kim, J. B., additional, Lee, H. J., additional, Ofori-Okai, B. K., additional, Oliver, M., additional, Rigby, A., additional, Schoenwaelder, C., additional, Sun, P., additional, Tschentscher, Th., additional, Witte, B. B. L., additional, Zastrau, U., additional, Gregori, G., additional, Nagler, B., additional, Hastings, J., additional, Glenzer, S. H., additional, and Monaco, G., additional

Published
2018
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13. Setup for meV-resolution inelastic X-ray scattering measurements and X-ray diffraction at the Matter in Extreme Conditions endstation at the Linac Coherent Light Source

Author

McBride, E. E., primary, White, T. G., additional, Descamps, A., additional, Fletcher, L. B., additional, Appel, K., additional, Condamine, F. P., additional, Curry, C. B., additional, Dallari, F., additional, Funk, S., additional, Galtier, E., additional, Gauthier, M., additional, Goede, S., additional, Kim, J. B., additional, Lee, H. J., additional, Ofori-Okai, B. K., additional, Oliver, M., additional, Rigby, A., additional, Schoenwaelder, C., additional, Sun, P., additional, Tschentscher, Th., additional, Witte, B. B. L., additional, Zastrau, U., additional, Gregori, G., additional, Nagler, B., additional, Hastings, J., additional, Glenzer, S. H., additional, and Monaco, G., additional

Published
2018
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17. Ab initio simulations of the dynamic ion structure factor of warm dense lithium.

Author

Witte, B. B. L., Shihab, M., Glenzer, S. H., and Redmer, R.

Subjects
*AB initio quantum chemistry methods, *LITHIUM, *IONIC structure
Abstract

We present molecular dynamics simulations based on finite-temperature density functional theory that determine self-consistently the dynamic ion structure factor and the electronic form factor in lithium. Our comprehensive data set allows for the calculation of the dispersion relation for collective excitations, the calculation of the sound velocity, and the determination of the ion feature from the total electronic form factor and the ion structure factor. The results are compared with available experimental x-ray and neutron scattering data. Good agreement is found for both the liquid metal and warm dense matter domain. Finally, we study the impact of possible target inhomogeneities on x-ray scattering spectra. [ABSTRACT FROM AUTHOR]

Published
2017
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