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150 results on '"Wark, J.S."'

5. Opacity effects in a solid-density aluminium plasma created by photo-excitation with an X-ray laser

Author

Rackstraw, D.S., Vinko, S.M., Ciricosta, O., Cho, B.I., Engelhorn, K., Chung, H.-K., Brown, C.R.D., Burian, T., Chalupský, J., Falcone, R.W., Graves, C., Hájková, V., Higginbotham, A., Juha, L., Krzywinski, J., Lee, H.J., Messerschmidt, M., Murphy, C., Ping, Y., Scherz, A., Schlotter, W., Toleikis, S., Turner, J.J., Vysin, L., Wang, T., Wu, B., Zastrau, U., Zhu, D., Nagler, B., Lee, R.W., Heimann, P.A., and Wark, J.S.

Published
2014
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8. Creation and diagnosis of a solid-density plasma with an X-ray free-electron laser

Author

Vinko, S.M., Ciricosta, O., Cho, B.I., Engelhorn, K., Chung, H.-K., Brown, C.R.D., Burian, T., Chalupsky, J., Falcone, R.W., Graves, C., Hajkova, V., Higginbotham, A., Juha, L., Krzywinski, J., Lee, H.J., Messerschmidt, M., Murphy, C.D., Ping, Y., Scherz, A., Schlotter, W., Toleikis, S., Turner, J.J., Vysin, L., Wang, T., Wu, B., Zastrau, U., Zhu, D., Lee, R.W., Heimann, P.A., Nagler, B., and Wark, J.S.

Subjects
X-ray lasers -- Usage, Free electron lasers -- Usage, Plasma (Ionized gases) -- Origin -- Chemical properties -- Atomic properties, High temperature plasmas -- Origin -- Chemical properties -- Atomic properties, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Matter with a high energy density (> [10.sup.5] joules per [cm.sup.3]) is prevalent throughout the Universe, being present in all types of stars (1) and towards the centre of the giant planets (2,3); it is also relevant for inertial confinement fusion (4). Its thermodynamic and transport properties are challenging to measure, requiring the creation of sufficiently long-lived samples at homogeneous temperatures and densities (5,6). With the advent of the Linac Coherent Light Source (LCLS) X-ray laser (7), high-intensity radiation (>[10.sup.17] watts per [cm.sup.2], previously the domain of optical lasers) can be produced at X-ray wavelengths. The interaction of single atoms with such intense X-rays has recently been investigated (8). An understanding of the contrasting case of intense X-ray interaction with dense systems is important from a fundamental viewpoint and for applications. Here we report the experimental creation of a solid-density plasma at temperatures in excess of [10.sup.6] kelvin on inertial-confinement time-scales using an X-ray free-electron laser. We discuss the pertinent physics of the intense X-ray-matter interactions, and illustrate the importance of electron-ion collisions. Detailed simulations of the interaction process conducted with a radiative-collisional code show good qualitative agreement with the experimental results. We obtain insights into the evolution of the charge state distribution of the system, the electron density and temperature, and the timescales of collisional processes. Our results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological systems, material science investigations, and the study of matter in extreme conditions., The experiment was performed at the LCLS soft X-ray materials science instrument (SXR), where a 1.0-µm-thick aluminium (Al) foil was irradiated with 80-fs X-ray pulses at photon energies in the [...]

Published
2012
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10. Atomic-scale visualization of inertial dynamics

Author

Lindenberg, A.M., Larsson, J., Sokolowski-Tinten, K., Gaffney, K.J., Blome, C., Synnergren, O., Sheppard, J., Caleman, C., MacPhee, A.G., Weinstein, D., Lowney, D.P., Allison, T.K., Matthews, T., Falcone, R.W., Cavalieri, A.L., Fritz, D.M., Lee, S.H., Bucksbaum, P.H., Reis, D.A., Rudati, J., Fuoss, P.H., Kao, C.C., Siddons, D.P., Pahl, R., Als-Nielsen, J., Duesterer, S., Ischebeck, R., Schlarb, H., Schulte-Schrepping, H., Tschentscher, Th., Schneider, J., von der Linde, D., Hignette, O., Sette, F., Chapman, H.N., Lee, R.W., Hansen, T.N., Techert, S., Wark, J.S., Bergh, M., Huldt, G., van der Spoel, D., Timneanu, N., Hajdu, J., Akre, R.A., Bong, E., Krejcik, P., Arthur, J., Brennan, S., Luening, K., and Hastings, J.B.

Subjects
Phase transformations (Statistical physics) -- Research -- Speed -- Observations, Science and technology
Abstract

The motion of atoms on interatornic potential energy surfaces is fundamental to the dynamics of liquids and solids. An accelerator-based source of femtosecond x-ray pulses allowed us to follow directly atomic displacements on an optically modified energy landscape, leading eventually to the transition from crystalline solid to disordered liquid. We show that, to first order in time, the dynamics are inertial, and we place constraints on the shape and curvature of the transition-state potential energy surface. Our measurements point toward analogies between this nonequilibrium phase transition and the short-time dynamics intrinsic to equilibrium liquids., In a crystal at room temperature, vibrational excitations, or phonons, only slightly perturb the crystalline order. In contrast, liquids explore a wide range of configurations set by the topology of [...]

Published
2005

15. Optimization of double pulse pumping for Ni-like Sm x-ray lasers

Author

Lin, J.Y., Tallents, G.J., Smith, R., MacPhee, A.G., Wolfrum, E., Zhang, J., eker, G., Lewis, C.L.S., Keenan, R., Neely, D., O'Rourke, R.M.N., Pert, G.J., Pestehe, S.J., and Wark, J.S.

Subjects
X-ray lasers -- Research, Samarium -- Analysis, Plasma (Ionized gases) -- Research, Physics
Abstract

A study was conducted to analyze double pulse pumping of the nickel-like samarium x-ray laser at 7.3 nm. The ratio of the prepulse to main pulse irradiance was determined using two fast photodiodes in the laser control region. A keV crystal spectrometer was then utilized to examine the degree of ionization of the x-ray lasing plasma. Results indicated that the the x-ray laser pumped by double drive pulses is an efficient and bright x-ray source at short wavelength.

Published
1999

16. A saturated X-ray laser beam at 7 nanometers

Author

Zhang, J., MacPhee, A.G., Lin, J., Wolfrum, E., Smith, R., Danson, C., Key, M.H., Neely, D., Nilsen, J., Pert, G.J., Tallents, G.J., and Wark, J.S.

Subjects
X-ray lasers -- Research, Laser beams -- Research, Science and technology, Research
Abstract

A saturated nickel-like samarium x-ray laser beam at 7 nanometers has been demonstrated with an output energy of 0.3 millijoule in 50-picosecond pulses, demonstrating that saturated operation of a laser at wavelengths shorter than 10 nanometers can be achieved. The narrow divergence, short wavelength, short pulse duration, high efficiency, and high brightness of this samarium laser make it an ideal candidate for many x-ray laser applications., An important objective in the development of x-ray lasers is to deliver a coherent, saturated output at wavelengths shorter than 10 nm (1). Such saturated x-ray lasers are required for [...]

Published
1997

31. Studies of the fast ignition route to inertial confinement fusion at the Rutherford Appleton Laboratory

Author

Norreys, P.A, Bakarezos, M, Barringer, L, Borghesi, M, Beg, F.N, Bell, A.R, Castro-Colins, M, Chambers, D, Dangor, A.E, Danson, C.N, Djaoui, A, Fews, A.P, Galliard, R, Gibbon, P, Gizzi, L, Glinsky, M.E, Hammel, B.A, Key, M.H, Lee, P, Loukakos, P, MacKinnon, A.J, Meyer, C, Meyer-ter-Vehn, J, Moustaizis, S, Preston, S.G, Pukhov, A, Rose, S.J, Tatarakis, M, Wark, J.S, Willi, O, Zepf, M, and Zhang, J

Published
1999
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33. Picosecond X-ray studies of coherent folded phonons in a multiple quantum well

Author

Sondhauss, Peter, Larsson, Jörgen, Harbst, Michael, Naylor, G.A., Plech, A, Scheidt, K, Synnergren, Ola, Wulff, M, and Wark, J.S

Subjects
Condensed Matter::Materials Science, Condensed Matter::Superconductivity, Atom and Molecular Physics and Optics, Physical Sciences, Physics::Optics, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Natural Sciences
Abstract

Coherent folded acoustic phonons in a multilayered GaSb/InAs epitaxial heterostructure were generated by femtosecond laser pulses and studied by means of ultrafast x-ray diffraction. Coherent phonons excited simultaneously in the fundamental acoustic branch and the first back-folded branch were detected. This represents the first clear evidence for phonon branch folding based directly on the atomic motion to which x-ray diffraction is sensitive. From a comparison of the measured phonon-modulated x-ray reflectivity with simulations, evidence was found for a reduction of the laser penetration depth. This reduction can be explained by the self-modulation of the refractive index due to photogenerated free carriers.

Published
2005

35. Ultrafast structural changes measured by time-resolved X-ray diffraction

Author

Physics Department and Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, MI 48109, USA, US, Physics Department, University of California at Berkeley, Berkeley, CA 94720, USA (E-mail: jorgen@physics.berkeley.edu), US, Physics Department, Clarendon Laboratory, University of Oxford, Oxford OX13PU, UK, UK, Advanced Light Source, Accelerator and Fusion Research Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA, US, Lawrence Livermore National Laboratory, Livermore, CA 94551, USA, US, Ann Arbor, Wark, J.S., Heimann, P.A., Padmore, H.A., Schuck, P.J., Lindenberg, A.M., Lee, R.W., Falcone, R.W., Bucksbaum, Philip H., Larsson, J., Physics Department and Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, MI 48109, USA, US, Physics Department, University of California at Berkeley, Berkeley, CA 94720, USA (E-mail: jorgen@physics.berkeley.edu), US, Physics Department, Clarendon Laboratory, University of Oxford, Oxford OX13PU, UK, UK, Advanced Light Source, Accelerator and Fusion Research Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA, US, Lawrence Livermore National Laboratory, Livermore, CA 94551, USA, US, Ann Arbor, Wark, J.S., Heimann, P.A., Padmore, H.A., Schuck, P.J., Lindenberg, A.M., Lee, R.W., Falcone, R.W., Bucksbaum, Philip H., and Larsson, J.

Published
2006

36. Picosecond X-ray diffraction studies of laser-excited acoustic phonons in InSb

Author

Department of Physics, The University of Michigan, Ann Arbor, MI 48109, USA, US, Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, UK, GB, Department of Physics, University of California, Berkeley, CA 94720, USA, US, Atomic Physics Division, Lund Institute of Technology, P.O. Box 118, 22100 Lund, Sweden, SE, European Synchrotron Radiation Facility, Grenoble, 38043, France, FR, Ann Arbor, Scheidt, K., Wark, J.S., Missalla, T., Lindenberg, A.M., Sondhauss, P., Wulff, M., Bucksbaum, Philip H., Naylor, G., Sj??gren, A., Falcone, R.W., Reis, D.A., Larsson, J., Allen, Ace, Department of Physics, The University of Michigan, Ann Arbor, MI 48109, USA, US, Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, UK, GB, Department of Physics, University of California, Berkeley, CA 94720, USA, US, Atomic Physics Division, Lund Institute of Technology, P.O. Box 118, 22100 Lund, Sweden, SE, European Synchrotron Radiation Facility, Grenoble, 38043, France, FR, Ann Arbor, Scheidt, K., Wark, J.S., Missalla, T., Lindenberg, A.M., Sondhauss, P., Wulff, M., Bucksbaum, Philip H., Naylor, G., Sj??gren, A., Falcone, R.W., Reis, D.A., Larsson, J., and Allen, Ace

Abstract

We have employed time-resolved X-ray diffraction with picosecond temporal resolution to measure the time-dependent rocking curves of laser-irradiated asymmetrically cut single InSb crystals. Coherent acoustic phonons were excited in the crystals by irradiation with 800-nm, 100-fs laser pulses at irradiances between 0.25 and 12??mJ/cm 2 . The induced time-dependent strain profiles (corresponding to the coherent phonons) were monitored by diffracting collimated, monochromatic pulses of X-rays from the irradiated crystals. Recording of the diffracted radiation with a fast low-jitter X-ray streak camera resulted in an overall temporal resolution of better than 2??ps. The strain associated with the coherent phonons modifies the rocking curve of the crystal in a time-dependent manner, and the rocking curve is recorded by keeping the angle of incidence of the X-rays upon the crystal fixed, but varying the energy of the incident X-rays around a central energy of 8.453??keV (corresponding to the peak of the rocking curve of the unperturbed crystal). The observed time-dependent diffraction from the irradiated crystals is in reasonable agreement with simulations over a wide range of energies from the unperturbed rocking-curve peak.

Published
2006

37. Opportunities and challenges using short-pulse X-ray sources.

Author

Larsson, J., Synnergren, O., Hansen, T.N., Sokolowski-Tinten, K., Werin, S., Caleman, Carl, Hajdu, J., Shepherd, J., Wark, J.S., Lindenberg, A.M., Gaffney, K.J., Hastings, J.B., Larsson, J., Synnergren, O., Hansen, T.N., Sokolowski-Tinten, K., Werin, S., Caleman, Carl, Hajdu, J., Shepherd, J., Wark, J.S., Lindenberg, A.M., Gaffney, K.J., and Hastings, J.B.

Abstract

Free-electron lasers will change the way we carry out time-resolved X-ray experiments. At present date, we use laser-produced plasma sources or synchrotron radiation. Laser-produced plasma sources have short pulses, but unfortunately large pulse-to-pulse fluctuations and large divergence. Synchrotron radiation from third generation source provide collimated and stable beams, but unfortunately long pulses. This means that either the timeresolution is limited to 100 ps or rather complex set-ups involving slicing or streak cameras are needed. Hard X-ray free-electron lasers will combine the best properties of present-day sources and increase the number of photons by many orders of magnitude. Already today, a precursor to the free-electron lasers has been built at Stanford Linear Accelerator Centre (SLAC). The Sub-Picosecond Photon Source (SPPS) has already shown the opportunities and challenges of using short-pulse X-ray sources.

Published
2005
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38. Clocking femtosecond X-rays

Author

Cavalieri, A.L., Fritz, D.M., Lee, S.H., Bucksbaum, P.H., Reis, D.A., Mills, D.M., Pahl, R, Rudati, J, Fuoss, P.H., Stephenson, G.B., Lowney, D.P., MacPhee, A.G., Weinstein, D, Falcone, R.W., Als-Nielsen, J, Blome, C, Ischebeck, R, Schlarb, H, Tschenscher, Th, Schneider, J, Sokolowski-Tinten, K, Chapman, H.N., Lee, R.W., Hansen, Tue, Synnergren, Ola, Larsson, Jörgen, Teschert, S, Sheppard, J, Wark, J.S., Bergh, M, Caleman, C, Huldt, G, van der Spoel, D, Timneanu, N, Hajdu, J, Bong, E, Emma, P, Krejicik, P, Arthur, J, Brennan, S, Gaffney, K.J., Lindenberg, A.M., Hastings, J.B., Cavalieri, A.L., Fritz, D.M., Lee, S.H., Bucksbaum, P.H., Reis, D.A., Mills, D.M., Pahl, R, Rudati, J, Fuoss, P.H., Stephenson, G.B., Lowney, D.P., MacPhee, A.G., Weinstein, D, Falcone, R.W., Als-Nielsen, J, Blome, C, Ischebeck, R, Schlarb, H, Tschenscher, Th, Schneider, J, Sokolowski-Tinten, K, Chapman, H.N., Lee, R.W., Hansen, Tue, Synnergren, Ola, Larsson, Jörgen, Teschert, S, Sheppard, J, Wark, J.S., Bergh, M, Caleman, C, Huldt, G, van der Spoel, D, Timneanu, N, Hajdu, J, Bong, E, Emma, P, Krejicik, P, Arthur, J, Brennan, S, Gaffney, K.J., Lindenberg, A.M., and Hastings, J.B.

Abstract

Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms.

Published
2005

39. XUV spectroscopic characterization of warm dense aluminum plasmas generated by the free-electron-laser FLASH

Author

Zastrau, U., primary, Burian, T., additional, Chalupsky, J., additional, Döppner, T., additional, Dzelzainis, T.W.J., additional, Fäustlin, R.R., additional, Fortmann, C., additional, Galtier, E., additional, Glenzer, S.H., additional, Gregori, G., additional, Juha, L., additional, Lee, H.J., additional, Lee, R.W., additional, Lewis, C.L.S., additional, Medvedev, N., additional, Nagler, B., additional, Nelson, A.J., additional, Riley, D., additional, Rosmej, F.B., additional, Toleikis, S., additional, Tschentscher, T., additional, Uschmann, I., additional, Vinko, S.M., additional, Wark, J.S., additional, Whitcher, T., additional, and Förster, E., additional

Published
2012
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40. Soft x-ray free electron laser microfocus for exploring matter under extreme conditions

Author

Nelson, A. J., primary, Toleikis, S., additional, Chapman, H., additional, Bajt, S., additional, Krzywinski, J., additional, Chalupsky, J., additional, Juha, L., additional, Cihelka, J., additional, Hajkova, V., additional, Vysin, L., additional, Burian, T., additional, Kozlova, M., additional, Fäustlin, R.R., additional, Nagler, B., additional, Vinko, S.M., additional, Whitcher, T., additional, Dzelzainis, T., additional, Renner, O., additional, Saksl, K., additional, Khorsand, A. R., additional, Heimann, P. A., additional, Sobierajski, R., additional, Klinger, D., additional, Jurek, M., additional, Pelka, J., additional, Iwan, B., additional, Andreasson, J., additional, Timneanu, N., additional, Fajardo, M., additional, Wark, J.S., additional, Riley, D., additional, Tschentscher, T., additional, Hajdu, J., additional, and Lee, R. W., additional

Published
2009
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41. In situ diffraction measurements of lattice response due to shock loading, including direct observation of the α–ε phase transition in iron

Author

Kalantar, D.H., primary, Collins, G.W., additional, Colvin, J.D., additional, Eggert, J.H., additional, Hawreliak, J., additional, Lorenzana, H.E., additional, Meyers, M.A., additional, Minich, R.W., additional, Rosolankova, K., additional, Schneider, M.S., additional, Stölken, J.S., additional, and Wark, J.S., additional

Published
2006
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46. High pressure solid state experiments on the nova laser

Author

Kalantar, D.H., primary, Remington, B.A., additional, Chandler, E.A., additional, Colvin, J.D., additional, Gold, D.M., additional, Mikaelian, K.O., additional, Weber, S.V., additional, Wiley, L.G., additional, Wark, J.S., additional, Hauer, A.A., additional, and Meyers, M.A., additional

Published
1999
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