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  • 1
    Electronic Resource
    Electronic Resource
    Neutron spectroscopy on Nova (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1729-1730 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Some fundamental properties of inertial confinement fusion implosions can be measured using diagnostics based on neutron spectroscopy. An instrument that will measure neutron spectra using time-of-flight techniques with an array of "single-hit'' detectors is being developed for use on Nova. Its initial application will be measurement of ion temperature. Potential other applications, such as measurement of fuel 〈 ρR〉 will also be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138561
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  • 2
    Electronic Resource
    Electronic Resource
    Neutron diagnosis of compressed ICF targets (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1737-1739 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The final stages in the compression of microencapsulated DT fueled ICF targets require detailed characterization for meaningful comparison with predictions of hydrodynamic codes. The determination of such parameters as the fuel and shell areal densities, the average ion temperature, and the impact of implosion nonuniformities in high-density target implosions present a strong challenge. We describe several approaches utilizing the self-generated neutrons to diagnose these conditions, including neutron spectrometry, neutron activation of tracer gas and shell materials, and neutron scattering techniques. The importance of making simultaneous measurements of several core parameters to limit ambiguity in interpretation is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139166
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  • 3
    Electronic Resource
    Electronic Resource
    High-yield direct drive experiments at Nova (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2100-2100 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A series of direct drive implosions of D-T filled, glass microballoons has been initiated in an effort to produce intense neutron sources for diagnostics development. In particular, measurements such as neutron imaging, burn history using a neutron-sensitive streak camera, and fuel ρr by both neutron activation and neutron spectroscopy could be more easily tested with these simple targets than high-density targets that initially are not expected to produce such high yields. Targets with nominal dimensions of 1000×2 μm which contained D-T at 12–14 atm were imploded with 18 kJ of 0.35-μm light from the 10-beam Nova system. For pulse widths of 1 ns in either converging or diverging geometry, fusion yields in excess of 1013 have been obtained. The yields are comparable to those predicted from numerous 1-D model calculations in spite of the asymmetric illumination geometry of the driver. Work performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under contract number W-7405-ENG-48.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138753
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  • 4
    Electronic Resource
    Electronic Resource
    Approaches to ultrafast neutron detectors (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1096-1097 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We discuss two approaches to obtain neutron detectors of very high temporal resolution. In the first approach, a uranium-coated cathode is used in a streak tube configuration. Secondary electrons accompanying the fission fragments from a neutron-uranium reaction are accelerated, focused through a pinhole, and streaked. Calculations show that 20-ps time resolution can be obtained. In the second approach, a uranium-coated cathode is integrated into a transmission line. State-of-the-art technology indicates that a time resolution of 20 ps can be obtained by gating the cathode with a fast electric pulse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138234
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  • 5
    Electronic Resource
    Electronic Resource
    Neutron imaging of inertial confinement fusion targets at Nova (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1694-1696 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Images of the neutron-emitting region of high-yield inertial confinement fusion targets have been obtained with a penumbral coded-aperture imaging system. The major components of the imaging system are the penumbral aperture, neutron detector, alignment hardware, and image reconstruction software. We describe these components and present an example of the neutron imaging results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140136
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  • 6
    Electronic Resource
    Electronic Resource
    Neutron emission time measurements for ICF targets (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1697-1699 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The neutron emission time for laser-driven inertial confinement fusion targets is determined from data recorded with fast neutron and optical detector systems. Two types of neutron detectors are used. Radiation-induced conductivity devices have a 130-ps FWHM response and are sensitive to targets with yields greater than 5×1010 DT neutrons. They measure the average neutron emission time with a precision of ±50 ps and are fast enough to measure the neutron production rate within a target core as a function of time. Plastic scintillators coupled to microchannel-plate photomultiplier tubes have a 1.2-ns FWHM response and measure the average neutron emission time with a precision of ±75 ps for targets with yields greater than 106 neutrons. Streak cameras record the incident laser power. Optical fiducial signals that are injected into each detector are used to cross time between the detector systems. Measurements made on 1-mm-diam spherical targets irradiated with 23 kJ of 0.35-μm light delivered in a temporally square 1.1-ns pulse and yielding 1013 neutrons show a burn duration greater than 300 ps and an average neutron emission time of about 850 ps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140137
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  • 7
    Electronic Resource
    Electronic Resource
    Debris collection from implosion of microballoons (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1734-1736 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Recovery of krypton from implosion of glass microballoons has been studied in the development of a radiochemical diagnostic for determination of 〈ρr〉fuel. Collection onto metal surfaces following implosions performed on the OMEGA laser with 1–3 TW (1–2 kJ) of 0.35-μm light is consistent with an ion implantation mechanism. The dependence of the intrinsic collection efficiency on the energy fluence to the collector surface and its variation in implosions carried out under the same nominal conditions indicate ion energies extending to at least 0.1 MeV and energy distribution functions that are sensitive to the details of the implosion dynamics. Intrinsic sticking efficiencies approaching 0.5 can be obtained in the limit of low total energy fluence to the collector surface (≤0.1 J cm−2).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139165
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  • 8
    Electronic Resource
    Electronic Resource
    Zone-plate imaging of neutrons emitted from a laser fusion target (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1803-1803 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Zone-plate coded imaging techniques are routinely used to image nonpenetrating emissions from laser fusion targets. Only highly penetrating radiations like 14-MeV neutrons will escape the dense compressed core region of future targets to provide information about the burn region. A zone plate for 14-MeV neutrons must be several centimeters thick to produce adequate modulation in the coded image. Computer modeling of zone-plate systems show that a thick, tapered zone plate acts like a thin zone plate for points within its field of view and depth of field. Equations developed for thin zone-plate systems that describe quantities such as planar and tomographic resolution may be applied to thick zone-plate systems. System simulations of a 100-zone, 5-cm-thick zone plate with 5-μm outer zone width constructed of alternating layers of gold and aluminum produce images with 10-μm resolution. The source strength required to image a 20-μm-diam source is 100 to 1000 times less than that needed with an equivalent pinhole system. Work performed under the auspices of the U.S. DOE by the LLNL under Contract No. W-7405-ENG-48.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139188
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  • 9
    Electronic Resource
    Electronic Resource
    Neutron penumbral aperture images of inertial confinement fusion targets achieve 60 μm resolution (abstract) : 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. 1220-1220 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Images formed by 14 MeV neutrons emitted from the core of inertial confinement fusion targets demonstrate 60 μm resolution for the penumbral aperture imaging system used in our 1988 experiments. Hohlraums containing deuterium–tritium filled capsules were irradiated at the Nova Laser Facility and produced images with detector limited resolution. Neutron yields ranged from 5×1010 to 2×1011. The results imply that convolution of the aperture point spread function with the neutron emitting region of the target core is less than 40 μm. Images produced by the indirect-drive hohlraum targets are compared with previously reported images of high-yield (1×1013) exploding-pusher targets that show 150 μm (full width half maximum) diameters for the emitting region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149457
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  • 10
    Electronic Resource
    Electronic Resource
    Design of a neutron penumbral-aperture microscope with 10 μm resolution : Eighth topical conference on high-temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3184-3186 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We are currently designing a 10 μm resolution neutron penumbral-aperture microscope to diagnose high-convergence targets at the Nova laser facility. To achieve such high resolution, the new microscope will require developments in three areas. First, we have designed thick penumbral apertures with extremely sharp cutoffs over a useful (≈100 μm) field of view; fabrication of such apertures appears feasible using gold electroplating techniques. Second, the limited field of view and required close proximity of the aperture to the target (2 cm) necessitates a durable mounting and alignment system with ±25 μm accuracy. Finally, a neutron detector containing 160 000 scintillator elements is required. We plan to utilize clad-scintillator elements in this array, bonded together with a high-Z paint to eliminate recoil-proton crosstalk. Two schemes are under consideration for readout of this large array.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141680
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