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  • 11
    Electronic Resource
    Electronic Resource
    Review of drive symmetry measurement and control experiments on the Nova laser system (invited) : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 672-677 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Good radiation drive symmetry is crucial for achieving ignition in laboratory inertial fusion experiments. X-ray drive symmetry in hohlraums has been the subject of investigation for more than four years and a great deal of progress has been made. Over the last two to three years, a concerted series of (indirect) drive symmetry experiments has been performed on the Nova laser system and is the subject of the present paper. The goals of this work have been to develop measurement techniques and to apply them to symmetry variation and control experiments. The principal diagnostic has utilized the symmetry signature impressed on the dense core of a target imploded by the hohlraum x-ray environment. The core is distorted by drive asymmetries and x-ray imaging of this core provides a mapping that can be compared with theoretical modeling and thus related to specific amounts of drive asymmetry. We will describe the instruments and measurement techniques used in these experiments and present representative data analysis. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146257
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  • 12
    Electronic Resource
    Electronic Resource
    Conversion efficiencies from laser-produced plasmas in the extreme ultraviolet regime (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2251-2258 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The conversion efficiency of spectral emission from laser-irradiated solid targets was investigated for short wavelength source development. The plasma brightness was quantified using absolutely calibrated detectors for 20 materials and spectra were obtained between 50 and 200 A(ring). Laser parameters such as wavelength, pulse length, intensity, and spot size were systematically varied to establish a comprehensive database for source optimization. Qualitative differences in the underlying dominant emission features as a function of atomic number and laser wavelength were observed that accounted for the relatively high spectral conversion efficiencies produced. In the specific case of Sn, a conversion efficiency greater than 0.8%/eV has been observed in the technologically important region of λ=134.0 A(ring) using a laser intensity of 1–2×1011 W/cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361149
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  • 13
    Electronic Resource
    Electronic Resource
    Characterization of a high-magnification x-ray microscope on Nova (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1852-1852 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have implemented a Wolter-type x-ray optic in a high- (22×) magnification microscope on Nova. We report on the on-line characterization of this system and show results from the several types of experiments performed. The point spread function, contrast transfer function at selected spatial frequencies, x-ray throughput, alignment accuracy, and field of view have all been measured as configured for Nova experiments. Such characterization may be used to remove the degradation introduced by the instrument. This work was performed under the auspices of the U.S. DOE by the Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140085
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  • 14
    Electronic Resource
    Electronic Resource
    Demonstration of reduced source size broadening with a Johann focusing elliptical spectrograph and theory of the second-order source broadening (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 1920-1925 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A Johann focusing elliptical spectrograph has been developed for the measurement of high-resolution x-ray spectra from a spatially extended source. The instrument was designed for the study of high-density, high-temperature plasmas produced by z-pinch implosion or ion-beam bombardment on pulsed-power accelerators. We have constructed and tested this instrument, and have demonstrated an improvement in resolution over what we obtain with a standard circular detector when viewing an extended source. Analytic results for the second-order source broadening due to a finite source size have been obtained and verified by ray tracing. Also given is a simple parametric equation for the Johann crossover curve in terms of either the ellipse sweep angle λ or the Bragg angle θB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141949
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  • 15
    Electronic Resource
    Electronic Resource
    Fluorescence measurements of the M-band photon emission from a laser-irradiated gold disk (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1476-1478 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Gold M-band x rays with energies above the sulfur K edge of 2.472 keV create sulfur Kα fluorescence with a quantum efficiency of 8.1%. The sulfur fluorescer was a 600×1500-μm rectangle about 1100 μm from the gold plate. It was 25 μm of C6H4S plastic shielded by 50 μm of beryllium. The absolute brightnesses of both the M-band spectrum and of the fluorescence line were measured by separate spectrographs. The spectrograph measuring the fluorescence did not have a direct line of sight to the hot gold. These measurements were made with 3512-A(ring) laser light irradiating the gold plate for 1 ns over a number of intensities between 2×1014 and 1015 W/cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139692
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  • 16
    Electronic Resource
    Electronic Resource
    Fast Pb-glass neutron-to-light converter for ICF target burn history measurements : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3187-3189 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We are developing a streak-camera-based instrument to diagnose the fusion reaction rate (burn history) in laser-driven ICF targets filled with D-T fuel. Recently, we attempted measurements using the 16.7 MeV gamma ray emitted in the T(d,γ)5He fusion reaction. Pb glass acts as a gamma-ray-to-light converter. Gamma rays interact in the glass to form electron-position pairs that produce large amounts (1000 photons/gamma ray) of prompt (〈10 ps) Cerenkov light as they slow down. In our experimental instrument, an f/10 Cassegrain telescope optically couples light produced in the converter to a streak camera having 20 ps resolution. Experiments using high-yield (1013 D-T neutrons), direct-drive targets at Nova produced good signals with widths of 200 ps. Time-of-flight measurements show the signals to be induced by neutrons rather than by gamma rays. The Pb glass appears to act as a fast neutron-to-light converter. We continue to study the interaction process and the possibility of using the 16.7 MeV gamma rays for burn time measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141681
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  • 17
    Electronic Resource
    Electronic Resource
    Four-frame gated optical imager with 120-ps resolution (invited) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1457-1460 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article we describe the operation and applications of a framing camera capable of four separate two-dimensional images with each frame having a 120-ps gate width. Fast gating of a single frame is accomplished by using a wafer image intensifier tube in which the cathode is capacitively coupled to an external electrode placed outside of the photocathode of the tube. This electrode is then pulsed relative to the microchannel plate by a narrow (120-ps), high-voltage pulse. Multiple frames are obtained by using multiple gated tubes which share a single bias supply and pulser with relative gate times selected by the cable lengths between the tubes and the pulser. A beam-splitter system has been constructed which produces a separate image for each tube from a single scene. Applications of the framing camera to inertial confinement fusion experiments are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139687
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  • 18
    Electronic Resource
    Electronic Resource
    Four-frame gated Wolter x-ray microscope : Eighth topical conference on high-temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2759-2761 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A four-frame gated x-ray microscope has been developed for the study of inertial confinement fusion. Four x-ray images were obtained by introducing flat, grazing incidence mirrors into the converging annular ray bundle of a previously developed Wolter x-ray microscope system. Gated microchannel plate detectors and associated drive electronics were developed which can record a sequence of gated images of less than 100 ps duration, with an interframe timing accuracy of ±50 ps. The resulting diagnostic can record one time-resolved image and four gated images simultaneously. The system is described, and images of an imploding capsule are presented which demonstrate the unique capabilities of the instrument.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141822
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  • 19
    Electronic Resource
    Electronic Resource
    Line focus of an elliptic cone for an x-ray crystal spectrograph (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3738-3744 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The crystal in any flat crystal x-ray spectrograph with the film plane at any angle and any position may be bent sagittally into an elliptic conical shape such that a perfect line focus is formed on the film plane for a point source at a fixed location. However, for high spectral resolution, only a narrow strip along the cone can be utilized. This strip will be near the plane formed by the axis of the cone and the source point. The elliptic cone has mirror symmetry in this plane. The equation of this cone is determined and its properties are discussed. Any conical surface has zero intrinsic curvature since one of the two principal radii of curvature is zero, so it is no more difficult to bend a crystal to this shape than to a concave circular cylinder with the same principal radius of curvature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141546
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  • 20
    Electronic Resource
    Electronic Resource
    Reply to the comments of Simon and Short (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 1342-1343 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In their comment, Simon and Short argue that their enhanced plasma wave model remains a possible explanation of the data reported in a previous paper [Phys. Fluids 31, 3130 (1988)]. While their clarifications of this model do invalidate the single, numerical argument used in that paper to reject it, a number of reasons remain to be skeptical of this model. In the present reply, these reasons are summarized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858965
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