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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The impedance of a diode having an annular cathode and indented anode that terminates a coaxial MITL (magnetically insulated transmission line) is measured and compared with a semiempirical model developed from calculations made using the magic code. The measurements were made on the 16-Ω electron accelerator HELIA (high-energy linear induction accelerator) operating at 3 MV. The model agrees with the measurements within the 10% measuring error and shows that the diode operates in either a load- or line-dominated regime depending on AK (anode-cathode) gap spacing. In the load-dominated regime, which corresponds to small AK gaps, the diode impedance is controlled by an effective anode-cathode gap, and the flow is approximately axial. In the line-dominated regime, which corresponds to large AK gaps, the impedance is independent of the AK gap and corresponds to the impedance associated with the minimum current solution of the MITL, with the flow becoming more radial as the AK gap is increased.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A review of the diagnostics used at Sandia National Laboratories to measure the parameters of intense proton and lithium beams generated on the PBFA-II accelerator will be presented. These diagnostics consist of several types, namely: Kα x-ray pinhole cameras, a multiframe dE/dx ion pinhole camera, a p-i-n array ion pinhole camera, Thomson parabola spectrographs, a Rutherford magnetic spectrograph, plasma visible spectroscopy, and several nuclear activation diagnostics. These components, when taken together, enable a rather thorough description of the 5-MV, 10-TW ion beams presently being produced. A unique feature of these diagnostics is that they are capable of operating in hard (several MeV) x-ray bremsstrahlung backgrounds of some 109–1010 rad/s. Details of each diagnostic, its integration, data reduction procedures, and recent PBFA-II data will be discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2197-2197 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Pin plasma sources are used as x-ray backlights for an Al plasma produced by focusing 1.06-μm laser light to irradiances of 1012 W/cm−2. Spatially resolved absorption features of the helium- like states of ionization of the plasma allow ground-state densities of the helium and hydrogenlike stages to be measured. Comparison with simulations indicates the need for realistic opacity effects to produce a high enough state of ionization for the plasma temperature. Work 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
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1485-1487 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have measured time-resolved visible spectra emitted from a plasma formed when the output from a dye laser irradiates solid lithium. Such a plasma has potential as a source of lithium ions for ion-driven inertial confinement fusion, and it also provides a useful source for developing diagnostics. The laser delivered 0.5 J onto a 2–7-mm-diam spot, with a 900-ns pulse length. Experiments were performed with the wavelength tuned to the Li i 2s–2p resonance line at 6708 A(ring) and off resonance at 6728 A(ring). The target was a 500–1000-A(ring)-thick Li film, vacuum evaporated in situ onto a substrate. The light from the plasma was coupled into the entrance slit of a 1-m Czerny–Turner spectrograph, and the output from the spectrograph was focused onto the input slit of a streak camera. The electron density was obtained from Stark-broadened widths of Li i 2p–4d, 2p–5d, and 2p–4s, and H i 2p–4d. An irradiance of 2×106 W/cm2 at 6708 A(ring) resulted in a peak electron density of 3.9×1017 cm−3. The density decreased at lower irradiance, with an intensity threshold of 5×105 W/cm2 for producing an ionized plasma. The threshold for producing a plasma was higher with the laser tuned off resonance, although high-density lithium plasmas could still be formed at relatively low laser irradiance.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed a new ion pinhole camera to obtain energy density profiles of a focused multiterawatt ion beam as a function of ion energy. Beam ions that are elastically scattered from a thin gold foil are imaged through six baffled pinholes onto six separate areas of a sheet of CR-39 nuclear track detector. Each of the areas is covered by an aluminum range filter and records an image with a different lower bound on the ion energy. Subtracting images with adjacent cutoff energies results in images with upper and lower bounds on the ion energy. Ion images are read from the CR-39 with VERA, a fully automatic, image-processor-based nuclear track counting system. Images of the Particle Beam Fusion Accelerator-II (PBFA-II) proton beam have been obtained and show that the beam has been focused to achieve a horizontal FWHM of 5.7 mm and has delivered 9 kJ/cm2 to a target.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2729-2732 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report on the construction and testing of a 100-ps framing camera based on a gated microchannel plate. The gating is obtained by applying a fast voltage pulse directly across the microchannel plate detector. An infinite ground-plane microstrip transmission-line configuration is used. We have measured the transit time for electrons through the microchannel plate to be 150±35 ps and the rise and fall times of the detector to be less than 100 ps. The time resolution computed using the experimentally measured edge response times is less than 100 ps.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1939-1945 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The relationship between hydrodynamics and radiative energy loss from a gas puff Z pinch was studied using helium, krypton, and a helium–krypton mixture. The results show that radiation cooling enables the magnetic field to compress the plasma to a higher electron density and a smaller final radius. The data are consistent with a simple model describing the thermalization of the plasma on the axis of the pinch. The spectrum of the krypton radiation from the mixture was harder than from the pure krypton pinch. This may be important for application of the Z pinch as a radiation source.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 90 (1986), S. 4882-4887 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The cellular reactions of excised hypocotyl segments of 31 cultivars of Phaseolus vulgaris to infection by two races of Colletotrichum lindemuthianum were surveyed. Consistent differences in the extent of fungal development and host cell necrosis were used to establish six infection categories.Extreme susceptibility (category 5) involved initial formation of infection vesicles in living epidermal cells and a prolonged period of intracellular biotrophic development prior to necrotrophic growth and production of spreading lesions. Extreme resistance (category 0) involved rapid death and browning of penetrated epidermal cells, without formation of infection vesicles or a detectable biotrophic phase. Fungal growth and host necrosis were limited to single epidermal cells. Intermediate reactions (categories 1 to 4) initially resembled category 5, but after a biotrophic phase of varying duration, infected cells and some adjacent uninfected cells died and became brown, and fungal growth ceased. Symptoms ranged from flecks (small groups of dead cells) to large areas of necrosis (limited lesions). Similar intermediate reactions also occurred in normally susceptible hypocotyls which were transferred from 17 to 25°C, or which retained cotyledons.The finding that resistance is expressed at different stages of infection is discussed in relation to the regulation of cultivar specificity.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 469 (1986), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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