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  • 1
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    Optically isolated, 2 kHz repetition rate, 4 kV solid-state pulse trigger generator (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-03-06
    Description: This paper presents the design and operation characteristics of a solid-state high voltage pulse generator. Its primary utilization is aimed at triggering a gaseous spark gap with high repeatability. Specifically, the trigger generator is designed to achieve a risetime on the order of 0.1 kV/ns to trigger the first stage, trigatron spark gap of a 10-stage, 500 kV Marx generator. The major design components are comprised of a 60 W constant current DC-DC converter for high voltage charging, a single 4 kV thyristor, a step-up pulse transformer, and magnetic switch for pulse steepening. A risetime of
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Reductions in gas exchange of Populustremuloides caused by leaf aging and ozone exposure (1996)
    Canadian Science Publishing
    Details
    Publication Date: 1996-08-01
    Description: Declines in gas exchange of mature leaves of Populustremuloides Michx. (quaking aspen) seedlings under four O3 treatments were investigated in a 33-d study. Gas exchange fell gradually with time, but under O3 exposure declines were accelerated. Photosynthetic capacity, stomatal conductance, and carboxylation efficiency were highly correlated, suggesting a coordinated reduction in the physiological activity of stressed leaves. Intercellular CO2 was not significantly different among treatments, indicating that stomatal opening was not the primary factor in limiting photosynthesis. Analysis of A:Ci response curves revealed that stomatal limitation increased only slightly, while biochemical limitation more than doubled, reaching a maximum of 47.1% by the third week of fumigations. Number of surviving leaves, ratio of surviving leaves to leaves produced, and total leaf area declined with O3 exposure. Whole-plant response curves were less linear than curves for the oldest subset of leaves because new leaves were produced continuously during the study, resulting in within-plant variation in O3 exposure. Declines in photosynthesis were greater than leaf area losses when data were expressed as a percentage of the control treatment. These results indicate that exposure to O3 for a relatively short time severely limits plant carbon gain in a sensitive free-growing species like aspen.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 3
    Electronic Resource
    Electronic Resource
    Ignition and high gain with ultrapowerful lasersf| (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1626-1634 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrahigh intensity lasers can potentially be used in conjunction with conventional fusion lasers to ignite inertial confinement fusion (ICF) capsules with a total energy of a few tens of kilojoules of laser light, and can possibly lead to high gain with as little as 100 kJ. A scheme is proposed with three phases. First, a capsule is imploded as in the conventional approach to inertial fusion to assemble a high-density fuel configuration. Second, a hole is bored through the capsule corona composed of ablated material, as the critical density is pushed close to the high-density core of the capsule by the ponderomotive force associated with high-intensity laser light. Finally, the fuel is ignited by suprathermal electrons, produced in the high-intensity laser–plasma interactions, which then propagate from critical density to this high-density core. This new scheme also drastically reduces the difficulty of the implosion, and thereby allows lower quality fabrication and less stringent beam quality and symmetry requirements from the implosion driver. The difficulty of the fusion scheme is transferred to the technological difficulty of producing the ultrahigh-intensity laser and of transporting this energy to the fuel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870664
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of laser and conventional heating in thermoluminescence dosimetry dosemapping : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4898-4900 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new, laser-based system has been developed for rapid evaluation of monolithic thermoluminescence dosimetry (TLD) arrays. A precision-controlled CO2 laser is used to sequentially heat 1.5-mm-diam, 38-μm-thick TLDs, deposited on a 0.125-mm-thick polymer substrate in a 3 mm×3 mm grid. Array areas up to 30 cm×30 cm are used ((approximately-greater-than)10 000 TLD elements), with evaluation times of 45–90 min. Isodose contours and various analysis functions are available on the system-operating PC. This system allows for greatly expanded dosimetry compared to standard TLDs, simultaneously decreasing effort and record keeping. We compared the dosimetric characteristics of this system with standard techniques, using near Si-equivalent CaF2:Mn TLD elements, in a test with 19 MeV end-point x radiation. The results show the laser system performs as well as the standard system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143544
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  • 5
    Electronic Resource
    Electronic Resource
    High yield inertial confinement fusion target design for a z-pinch-driven hohlraum : The 40th annual meeting of the division of plasma physics of the american physical society (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 2129-2136 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Calculations are presented for a high yield inertial fusion design, employing indirect drive with a double-ended z-pinch-driven hohlraum radiation source. A high current (∼60 MA) accelerator implodes z pinches within an enclosing hohlraum. Radial spoke arrays and shine shields isolate the capsule from the pinch plasma, magnetic field, and direct x-ray shine. Our approach places minimal requirements on z-pinch uniformity and stability, usually problematic due to magneto-Rayleigh–Taylor instability. Large inhomogeneities of the pinch and spoke array may be present, but the hohlraum adequately smooths the radiation field at the capsule. Simultaneity and reproducibility of the pinch x-ray output to better than 7% are required, however, for good symmetry. Recent experiments suggest a pulse shaping technique, through implosion of a multishell z pinch. X-ray bursts are calculated and observed to occur at each shell collision. A capsule absorbing 1 MJ of x rays at a peak drive temperature of 210 eV is found to have adequate stability and to produce 400 MJ of yield. A larger capsule absorbs 2 MJ with a yield of 1200 MJ. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873464
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  • 6
    Electronic Resource
    Electronic Resource
    Electron, photon, and ion beams from the relativistic interaction of Petawatt laser pulses with solid targets : The 41st annual meeting of the division of plasma physics of the american physical society (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 2076-2082 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In recent Petawatt laser experiments at Lawrence Livermore National Laboratory, several hundred joules of 1 μm laser light in 0.5–5.0-ps pulses with intensities up to 3×1020 W cm−2 were incident on solid targets and produced a strongly relativistic interaction. The energy content, spectra, and angular patterns of the photon, electron, and ion radiations have all been diagnosed in a number of ways, including several novel (to laser physics) nuclear activation techniques. About 40%–50% of the laser energy is converted to broadly beamed hot electrons. Their beam centroid direction varies from shot to shot, but the resulting bremsstrahlung beam has a consistent width. Extraordinarily luminous ion beams (primarily protons) almost precisely normal to the rear of various targets are seen—up to 3×1013 protons with kTion∼several MeV representing ∼6% of the laser energy. Ion energies up to at least 55 MeV are observed. The ions appear to originate from the rear target surfaces. The edge of the ion beam is very sharp, and collimation increases with ion energy. At the highest energies, a narrow feature appears in the ion spectra, and the apparent size of the emitting spot is smaller than the full back surface area. Any ion emission from the front of the targets is much less than from the rear and is not sharply beamed. The hot electrons generate a Debye sheath with electrostatic fields of order MV per micron, which apparently accelerate the ions. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874030
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  • 7
    Electronic Resource
    Electronic Resource
    Energy transfer between crossing laser beams (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 382-385 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Induced scattering between crossing laser beams is considered, including the effects of long-wavelength modulations in the plasma. This fundamental process can impact the choice of beam-smoothing techniques for laser-driven hohlraums. Study of this process is an ideal way to quantify stimulated scattering instabilities, since one can independently vary the intensity, polarization, and frequency separation of the crossing beams. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871863
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of film development on uniformity and modulation transfer function of the gated/fast x-ray imagers data : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 521-524 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have been investigating the different phenomena that affect the modulation transfer function response of the gated x-ray imagers and fast x-ray imagers that we use to record subnanosecond x-ray images at different laser facilities. As part of that investigation, we noticed that there is definite nonuniformity to the recorded images, even when the incident radiation was uniform. After a significant effort to track down that effect we found that the automatic developing processors, which process the film along the length of the roll, cause the effect. Manual development, which depends primarily on transverse agitation in the developer, and automatic processors that do not use a feed mechanism but emulate this agitation, do not introduce such artifacts. We recommend that for absolutely critical missions, such as target symmetry measurements, certain automatic machines should not be used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1310585
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  • 9
    Electronic Resource
    Electronic Resource
    Quantitative x-ray imager (abstract) : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 705-705 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report on development of a quantitative x-ray imager (QXI) for the national Inertial Confinement Fusion Program. Included in this development is a study of photocathode response as a function of photon energy, 2–17.5 keV, which is related to diagnostic development on the National Ignition Facility (NIF). The QXI is defined as being a quantative imager due to the repeated characterization. This instrument is systematically checked out, electronically as well as its photocathode x-ray response, both on a direct current and pulsed x-ray sources, before and after its use on a shot campaign. The QXI is a gated x-ray imager1 used for a variety of experiments conducted in the Inertial Confinement Fusion and Radiation Physics Program. The camera was assembled in Los Alamos and has been under development since 1997 and has now become the workhorse framing camera by the program. The electronics were built by Grant Applied Physics of San Fransisco, CA.2 The QXI has been used at the LANL Trident, LLNL Nova, and University of Rochester Laboratory OMEGA laser facilities. The camera consists of a grated microchannel plate (MCP), a phosphor coated fiberoptic faceplate coupled to film for data readout, along with high speed electronic pulsers to drive the x-ray detector. The QXI has both a two-strip and a four-strip detection head and has the ability to individually bias the gain of each of the strips. The timing of the QXI was done at the Trident short pulse laboratory, using 211 nm light. Single strip jitter was looked at as well and determined to be 〈25 ps. Flatfielding of the photocathode across the MCP was done with the Trident main laser with 150 J on a gold disk with a 1 ns. Spatial resolution was determined to be 〈5 μm by using the same laser conditions as before and a backlit 1000 lp/in. grid. The QXI has been used on cylindrical implosion work at the Nova Laser Facility, and on direct-drive cylinder mix and indirect-drive high convergence implosion experiments at OMEGA. Its two-strip module has provided the capability to look at point backlighters, as part of technique development for experiments on the NIF. Its next use will be in March 2000 with its off axis viewer nose at Omega, providing a perpendicular view of Rayleigh–Taylor spike dissipation. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1329655
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  • 10
    Electronic Resource
    Electronic Resource
    Evidence for bias dependent barrier heights in gold-epitaxial CdTe Schottky diodes (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3295-3299 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The forward bias and reverse bias current-voltage characteristics of some gold-epitaxial CdTe-on-InSb Schottky diodes have been measured at room temperature. Series resistance is evident in undoped material (base electron concentration ∼1014 cm−3) which has been measured and corrected for and identified as arising from the reverse biased CdTe-InSb junction. Two straight lines of differing slopes are present in the semilog plots for all the diodes, which we interpret as a bias-dependent barrier height. The two barrier heights, 0.91±0.04 eV and 0.74±0.02 eV, are well known in the Au-CdTe system, from which we conclude that two discrete states are present at the CdTe-Au interface. The occupancy of the states is determined by the applied bias, and hence the barrier height changes. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358614
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