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  • 1
    Electronic Resource
    Electronic Resource
    Development of a neutron imaging diagnostic for inertial confinement fusion experiments : 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. 865-868 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Pinhole imaging of the neutron production in laser-driven inertial confinement fusion experiments can provide important information about the performance of various capsule designs. This requires the development of systems capable of spatial resolutions on the order of 5 μm or less for source strengths of 1015 and greater. We have initiated a program which will lead to the achievement of such a system to be employed at the National Ignition Facility (NIF) facility. Calculated neutron output distributions for various capsule designs will be presented to illustrate the information which can be gained from neutron imaging and to demonstrate the requirements for a useful system. We will describe the lines-of-sight available at NIF for neutron imaging and explain how these can be utilized to reach the required parameters for neutron imaging. We will describe initial development work to be carried out at the Omega facility and the path which will lead to systems to be implemented at NIF. Beginning this year, preliminary experiments will be aimed at achieving resolutions of 30–60 μm for direct-drive capsules with neutron outputs of about 1014. The main thrust of these experiments will be to understand issues related to the fabrication and alignment of small diameter pinhole systems as well as the problems associated with signal-to-background ratios at the image plane. Subsequent experiments at Omega will be described. These efforts will be aimed at achieving resolutions of about 10 μm. Proposed developments for new imaging systems as well as further refinement of pinhole techniques will be presented. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1329883
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  • 2
    Electronic Resource
    Electronic Resource
    Two-dimensional capsule-hohlraum designs for the National Ignition Facility (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 3724-3733 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article describes 250, 280, and 350 eV drive temperature copper-doped Be [Be(Cu)] two-dimensional (2-D) capsule-hohlraum designs for the National Ignition Facility (NIF) [Paisner et al., Laser Focus World 30, 75 (1994)]. These capsule-hohlraum designs are a follow-on to the previous one-dimensional capsule designs of Bradley and Wilson [Phys. Plasmas 6, 4293 (1999)]. It is shown that a 2-D 350 eV capsule-hohlraum design scaled from the successful 330 eV design does not ignite, mostly due to poor symmetry. In addition, the 350 eV capsule hohlraum design requires the full 500 TW of the NIF design and 1.66 MJ of the maximum 1.8 MJ designed energy output. It is possible to design a capsule-hohlraum combination that achieves ignition and burn with peak radiation temperatures of 250, 280, and 330 eV. These designs use from 1.3 to 1.6 MJ of laser energy and the successful designs have yields of 16–20 MJ. Changes in symmetry and yield due to changing the focal point of the inner and outer laser cones were examined. The 280 eV capsule can tolerate pointing changes of 40–100 μm before the yield drops by 50%, while even a 40 μm pointing change for the 250 eV capsule causes the yield to drop by a factor of 2 to 100. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1385173
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  • 3
    Electronic Resource
    Electronic Resource
    Physics of one-dimensional capsule designs for the National Ignition Facility (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 4293-4303 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article describes a suite of 250, 280, and 350 eV copper-doped Be [Be(Cu)] capsule designs for the National Ignition Facility [Paisner et al., Laser Focus World 30, 75 (1994)] and compare these to previous Be(Cu) and bromine-doped CH plastic [CH(Br)] capsule designs for 300 and 330 eV drives. These capsule designs are constrained to have the same deuterium-tritium (DT) fuel mass as the 300 and 330 eV designs so that differences in yield are due to differences in capsule compression before ignition. The one-dimensional (1-D) calculations show that the fuel ρr reaches a maximum value when about 20–30 μm of ablator material is left behind, and this amount of ablator material provides the best trade-off between maximizing the fuel ρr, the implosion velocity, and the calculated clean yield. The results of this paper add optimized 1-D capsule designs that operate at drive temperatures of 250, 280, and 350 eV and they complement the established 300 eV CH(Br) ablator and the 330 eV Be(Cu) ablator designs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873710
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  • 4
    Electronic Resource
    Electronic Resource
    Solar-cycle variation of the daily foF2 and M(3000)F2 (1998)
    Springer
    Annales geophysicae 16 (1998), S. 1039-1042 
    Details
    ISSN: 0992-7689
    Keywords: Electromagnetics (Guided waves) ; Ionosphere (Ionospheric disturbances) ; Radio Science (Radio wave propagation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Daily values of the ionospheric characteristics foF2 and M(3000)F2 for a given hour and month are correlated with the corresponding daily values of sunspot number using measured data collected at seven European locations. The significance of applying different-order polynomials is considered and the times are confirmed when the higher-order terms are important. Mean correlation coefficients for combined data sets over all hours, months and stations are determined, together with the standard errors of estimates. Comparisons are made with corresponding figures for monthly median values derived from the same data sets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-998-1039-0
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