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  • 1
    Digitale Medien
    Digitale Medien
    Prospects for fluorescence based imaging/visualization of hydrodynamic systems on the National Ignition Facility : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 663-666 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The next generation of large, high power lasers, such as the National Ignition Facility in the U.S., Laser Mega Joule in France or Helen Successor in the United Kingdom offers the prospect of x-ray fluorescence based diagnosis of hydrodynamic experiments. We discuss two promising techniques for pumping this fluorescence. One is to use a large fraction of these facilities' high power to efficiently make multi-kilovolt x rays which, in turn, causes dopants placed in experimental packages to fluoresce. The second technique is to use the sizable multi-kilovolt photon background that we expect to be present in many hohlraum based experiments, while the driving laser is on, to pump x-ray fluorescence. Here, the fluorescing medium could be a dopant in an experimental package or, possibly, a relatively thick slab of material in the hohlraum wall which could serve as a backlighter. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1149391
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  • 2
    Digitale Medien
    Digitale Medien
    Blast wave diagnostic for the Petawatt laser system : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 806-809 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We report on a diagnostic to measure the trajectory of a blast wave propagating through a plastic target 400 μm thick. This blast wave is generated by the irradiation of the front surface of the target with ∼400 J of 1 μm laser radiation in a 20 ps pulse focused to a ∼50 μm diameter spot, which produces an intensity in excess of 1018 W/cm2. These conditions approximate a point explosion and a blast wave is predicted to be generated with an initial pressure nearing 1 Gbar which decays as it travels approximately radially outward from the interaction region. We have utilized streaked optical pyrometry of the blast front to determine its time of arrival at the rear surface of the target. Applications of a self-similar Taylor–Sedov blast wave solution allows the amount of energy deposited to be estimated. The experiment, LASNEX design simulations and initial results are discussed. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1149277
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  • 3
    Digitale Medien
    Digitale Medien
    Recent progress in high-energy, high-resolution x-ray imaging techniques for application to the National Ignition Facility (invited) : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 525-529 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Multi-keV x-ray microscopy will be an important laser-produced plasma diagnostic at future megajoule facilities such as the National Ignition Facility (NIF). However, laser energies and plasma characteristics imply that x-ray microscopy will be more challenging at NIF than at existing facilities. In earlier work, we concluded that target-mounted pinholes and single spherical or toroidal crystals are good options for many x-ray microscopy applications at NIF. In this article, we review the experimental progress we have made investigating these systems on the Nova and Petawatt Laser Facilities. In particular, we have performed high-resolution, high-magnification target-mounted pinhole imaging of Nova implosions, and we have obtained promising preliminary spherical-crystal data from high-intensity Petawatt experiments. We are also designing a high-energy spherical-crystal imager for use on Nova experiments. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1149271
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  • 4
    Digitale Medien
    Digitale Medien
    Time-resolved x-ray imaging of high-power laser-irradiated underdense silica aerogels and agar foams (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 3820-3831 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: This article presents the results of experiments in which a high-power laser was used to irradiate low density (4–9 mg/cm3) silica aerogel and agar foam targets. The laser–solid interaction and energy transport through the material were monitored with time-resolved imaging diagnostics, and the data show the production and propagation of an x-ray emission front in the plasma. The emission-front trajectory data are found to be in significant disagreement with detailed simulations, which predict a much more rapid heating of the cold material, and the data suggest that this discrepancy is not explainable by target inhomogeneities. Evidence suggests that energy transport into the cold material may be dominated by thermal conduction; however, no completely satisfactory explanation for the discrepancies is identified, and further experimental and theoretical research is necessary in order to resolve this important problem in laser–plasma interaction physics. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871081
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  • 5
    Digitale Medien
    Digitale Medien
    Hot electron production and heating by hot electrons in fast ignitor research : The 39th annual meeting of division of plasma physics of APS (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1966-1972 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In an experimental study of the physics of fast ignition, the characteristics of the hot electron source at laser intensities up to 1020 W cm−2 have been measured and a diagnosis of the heating at depth by hot electrons has been initiated. Generation of hot electrons with more than 30% efficiency has been observed. Preliminary heating data suggest temperatures kT in the range 300–800 eV.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872867
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  • 6
    Digitale Medien
    Digitale Medien
    Dynamics of a multiple-pulse-driven x-ray laser plasma (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 606-613 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In this paper we describe experimental and computational studies of multiple-pulse-driven laser plasma, which is the gain medium for a neon-like yttrium x-ray laser. Near-field emission profiles have been measured both with and without reinjection of the x-ray laser photons to couple with the amplifying medium created by later pulses using an external multilayer mirror. From the temporal and spatial evolution of the near-field emission profiles we can examine the pulse-to-pulse variation of the x-ray laser plasma due to changes in the hydrodynamics, laser deposition, and the injecting of x-ray laser photons back into an amplifying x-ray laser plasma. Using a combination of radiation hydrodynamics, atomic kinetics, and ray propagation codes, reasonable agreement has been obtained between simulations and the experimental results. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871888
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  • 7
    Digitale Medien
    Digitale Medien
    Ultrafast (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser for the 1.3 μm wavelength regime (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2271-2273 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: (GaIn)(NAs) vertical-cavity surface-emitting lasers for room-temperature emission at 1.3 μm wavelength are designed and grown by metal-organic vapor-phase epitaxy using dimethylhydrazine and tertiarybutylarsine. Room-temperature operation at wavelengths up to 1.285 μm is achieved with low optical pumping thresholds between 1.6 and 2.0 kW/cm2. Stimulated emission dynamics after femtosecond optical pumping are measured and compare favorably with results on (GaIn)As/Ga(PAs)-based structures. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.123821
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  • 8
    Digitale Medien
    Digitale Medien
    The Effect of Timing of Rehabilitation Procedures on the Establishment of a Jarrah Forest After Bauxite Mining (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Restoration ecology 4 (1996), S. 0 
    Details
    ISSN: 1526-100X
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The restoration of the high botanical diversity of the premining jarrah (Eucalyptus marginata) forest is a major priority of rehabilitation following bauxite mining in southwestern Australia. This study investigated the effects of different ripping, seeding, and scarifying dates on the establishment of plants from propagules stored in the topsoil and from applied seed on areas being rehabilitated after mining. Seed stored in the topsoil, rather than applied seed, was the major contributor to plant diversity. Ripping late (April) or scarifying in June significantly reduced the number of species and numbers of individual plants that established from propagules in the topsoil. Species originating from broadcast seed were most numerous when the seed was broadcast in April or after scarifying in June. Scarifying before seeding, particularly in June, increased the establishment of species from the broadcast seed. To make best use of the applied seed, without jeopardizing the establishment of species from the topsoil, pits should be ripped and sown by April. We list a number of strategies that can help maximize plant numbers and botanical diversity on rehabilitated bauxite mines, which may also be of more general application for restoring the original native vegetation on disturbed sites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1526-100X.1996.tb00103.x
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  • 9
    Digitale Medien
    Digitale Medien
    Effects of Bauxite Mine Restoration Operations on Topsoil Seed Reserves in the Jarrah Forest of Western Australia (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Restoration ecology 4 (1996), S. 0 
    Details
    ISSN: 1526-100X
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: We studied the effects of soil handling operations during bauxite mining and restoration on the numbers and depth distribution of seed stored in the surface soil of the jarrah forest. Germinable seed stores were determined in four sites of undisturbed forest, these same sites after clearing and burning of forest residues, in the soil immediately following the construction of topsoil stockpiles, in the respread topsoil and then after deep ripping of the respread topsoil. Average density of germinable seed at four sites prior to disturbance was 352 m−2. After clearing and burning, the seed store had decreased to a mean 74% of the original forest soil seed store density. When the top-soil was stockpiled prior to respreading, the seed content was further reduced to 31% in freshly constructed stockpiles and had declined to 13% after 10 months in the stockpiles. After ripping of the respread topsoil the seed content was 16% of the original forest seed store density. In one site where the topsoil was directly stripped and respread with no period of stockpiling but with a period of fallow, the seed store was 32% after respreading and then increased to 53% of the original forest store after ripping. This increase may have been caused by an underestimate of the reserves due to insufficient heating of the samples to break dormancy in fire-requiring species. In the forest topsoils seed was concentrated in the upper few centimeters of the soil profile, whereas after the mining and restoration operations seed was evenly distributed throughout the returned soil profile to a depth of 20 cm. Small-seeded annual species, which were common in the forest seed store, were more sensitive to the soil handing operations and declined to very low numbers, whereas hard-seeded plant species such as Acacia spp. were less affected by the soil handling operations. Implications for bauxite mine revegetation operations include the recommendation that direct return of topsoil should be carried out wherever possible with a minimum delay between clearing, stripping, respreading, and ripping.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1526-100X.1996.tb00189.x
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  • 10
    Digitale Medien
    Digitale Medien
    The effect of bone drilling on pain in gonarthrosis (1995)
    Springer
    International orthopaedics 19 (1995), S. 12-15 
    Details
    ISSN: 1432-5195
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Résumé Vingt-sept cas d'arthrose légère ou modérée du genou, diagnostiqués par arthroscopie et traités par forage, ont été revus avec un recul moyen de 4 ans (de 2 à 7 ans). La douleur, évaluée selon la cotation VAS, était diminuée pendant 24 mois en moyenne (1 à 76) dans les deux tiers des cas. Les résultats étaient meilleurs chez les patients présentant une arthrose globale que chez ceux atteints d'une arthrose uni-compartimentale. Ils étaient obtenus aussi bien dans les cas douloureux au repos (n=39) que dans ceux douloureux lors de la mobilisation du genou (n=14). Les complications ont été exceptionnelles (n=1). La douleur était diminuée dans une proportion significativement supérieure dans les genoux traités par forage que dans un groupe de contrôle de 16 cas, n'ayant subi qu'une arthroscopie à visée diagnostique (p=0.006). Le forage est un procédé sûr, n'entraînant que de rares complications. Il est indiqué dans le traitement des douleurs du genou chez les patients ayant une arthrose légère ou modérée, lorsque des interventions plus importantes ne sont ni nécessaires, ni réalisables.
    Notizen: Summary Seventy-seven patients with mild to moderate gonarthrosis of the knee were treated by subchondral bone drilling, and followed for from 2 to 7 years. Patients with generalised arthrosis benefited more than those with unicompartmental involvement. Pain, assessed by a visual analogue scale, was significantly reduced compared with a control group of 16 patients who had a diagnostic arthroscopy only. Drilling is a safe procedure with few complications and can be used in patients when more extensive surgery is not yet indicated or possible.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00184908
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