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Proton shadow camera using CR-39 track detectors

Description: We have developed a capability for imaging proton sources of moderate energy (6 MeV), with moderate spatial resolution (approx. = 9 ..mu..m), as a diagnostic for laser fusion research. Our technique involves the use of Fresnel zone plate coded imaging coupled with nuclear track detectors (CR-39). We report on a series of test experiments in which a zone plate shadow camera successfully produced images of a proton source distribution. The zone plate shadow patterns were optically reconstructed in higher order producing diffraction-limited point response images with FWHM values of approx. = 9 ..mu..m for a 6 MeV proton source.
Date: September 1, 1983
Creator: Stone, G.F. & Ceglio, N.M.
Partner: UNT Libraries Government Documents Department

Microstructures for high-energy x-ray and particle-imaging applications

Description: Coded imaging techniques using thick, micro-Fresnel zone plates as coded apertures have been used to image x-ray emissions (2-20 keV) and 3.5 MeV Alpha particle emissions from laser driven micro-implosions. Image resolution in these experiments was 3-8 ..mu..m. Extension of this coded imaging capability to higher energy x-rays (approx. 100 keV) and more penetrating charged particles (e.g. approx. 15 MeV protons) requires the fabrication of very thick (50-200 ..mu..m), high aspect ratio (10:1), gold Fresnel zone plates with narrow linewidths (5-25 ..mu..m) for use as coded aperatures. A reactive ion etch technique in oxygen has been used to produce thick zone plate patterns in polymer films. The polymer patterns serve as electroplating molds for the subsequent fabrication of the free-standing gold zone plate structures.
Date: May 1, 1981
Creator: Ceglio, N.M.; Stone, G.F. & Hawryluk, A.M.
Partner: UNT Libraries Government Documents Department

Fabrication and testing of gas filled targets for large scale plasma experiments on Nova

Description: An experimental campaign on the Nova laser was started in July 1993 to study one st of target conditions for the point design of the National Ignition Facility (NIF). The targets were specified to investigate the current NIF target conditions--a plasma of {approximately}3 keV electron temperature and an electron density of {approximately}1.0 E + 21 cm{sup {minus}3}. A gas cell target design was chosen to confine as gas of {approximately}0.01 cm{sup 3} in volume at {approximately} 1 atmosphere. This paper will describe the major steps and processes necessary in the fabrication, testing and delivery of these targets for shots on the Nova Laser at LLNL.
Date: March 6, 1995
Creator: Stone, G.F.; Spragge, M.; Wallace, R.J. & Rivers, C.J.
Partner: UNT Libraries Government Documents Department

Gas-filled hohlraum fabrication

Description: Los Alamos National Laboratory (LANL) researchers have fabricated and fielded gas-filled hohlraums at the Lawrence Livermore National Laboratory (LLNL) Nova laser. Fill pressures of 1--5 atmospheres have been typical. We describe the production of the parts, their assembly and fielding. Emphasis is placed on the production of gas-tight polyimide windows and the fielding apparatus and procedure.
Date: September 1, 1995
Creator: Salazar, M.A.; Gobby, P.L.; Foreman, L.R.; Bush, H. Jr.; Gomez, V.M.; Moore, J.E. et al.
Partner: UNT Libraries Government Documents Department

Summary of control and data acquisition systems for Nova experiments

Description: The Nova Laser has completed its first year of operation. During this period, emphasis has been placed on activation of the facility and of the numerous target and beam diagnostics. Two separate target chambers are in use. Nova operation is separated into two broad functions: Laser Operations and Experiments. The Operations Group provides the laser system control, operation and data acquisition and the Experiments Group provides experiment definition, diagnostic instrumentation and overall data processing. On the Operations side, VAX 11/780 computers are used to set up diagnostic operating parameters and collect data recorded by the CAMAC and CCD modules. These data are delivered in files by electronic link to the Laser Experiments and Analysis Facility (LEAF) VAX 11/785 of the Experiments Group for processing. Film data are digitized at LEAF and the film data files are also processed on the LEAF VAX.
Date: April 1, 1986
Creator: McCauley, E.W.; Campbell, E.M.; Auerbach, J.M.; Montgomery, D.S.; Martin, V.A.; Randolph, J.E. et al.
Partner: UNT Libraries Government Documents Department

Three Mile Island, Unit 2, radiation protection program: report of the special panel

Description: A special panel was appointed by the Director of Nuclear Reactor Regulation, NRC, to review the radiation protection program at Three Mile Island Unit 2. The Panel confirmed several management and technical deficiencies in the program. Recent major GPU/Met Ed commitments and actions demonstrated a major change in management attitude. The Panel concluded that exposures to personnel can be maintained to as low as is reasonably achievable while limited preparatory recovery work continues and when further needed improvements are implemented as needed, the radiation safety program will be able to support major recovery activities.
Date: December 1, 1979
Creator: Meinhold, C. B.; Murphy, T. D.; Neely, D. R.; Kathren, R. L.; Rich, B. L.; Stone, G. F. et al.
Partner: UNT Libraries Government Documents Department

Electron density measurement of a colliding plasma using soft x-ray laser interferometry

Description: The understanding of the collision and subsequent interaction of counter-streaming high-density plasmas is important for the design of indirectly-driven inertial confinement fusion (ICF) hohlraums. We have employed a soft x-ray Mach-Zehnder interferometer, using a Ne- like Y x-ray laser at 155 {angstrom} as the probe source, to study interpenetration and stagnation of two colliding plasmas. We observed a peaked density profile at the symmetry axis with a wide stagnation region with width of order 100 {mu}m. We compare the measured density profile with density profiles calculated by the radiation hydrodynamic code LASNEX and a multi-specie fluid code which allows for interpenetration. The measured density profile falls in between the calculated profiles using collisionless and fluid approximations. By using different target materials and irradiation configurations, we can vary the collisionality of the plasma. We hope to use the soft x-ray laser interferometry as a mechanism to validate and benchmark our numerical codes used for the design and analysis of high-energy- density physics experiments.
Date: May 1, 1996
Creator: Wan, A.S.; Back, C.A.; Barbee, T.W.Jr.; Cauble, R.; Celliers, P.; DaSilva, L.B. et al.
Partner: UNT Libraries Government Documents Department

Experimental Investigation of Short Scalelength Density Fluctuations in Laser-Produced Plasmas

Description: The technique of near forward laser. scattering is used to infer characteristics of intrinsic and controlled density fluctuations in laser-produced plasmas. Intrinsic fluctuations are studied in long scalelength plasmas where the fluctuations exhibit scale sizes related to the size of the intensity variations in the plasma forming and interaction beams. Stimulated Brillouin forward scattering and filamentation appear to be the primary mechanism through which these fluctuations originate. The beam spray which results from these fluctuations is important to understand since it can affect symmetry in an inertial confinement fusion (ICF) experiment. Controlled fluctuations are studied in foam and exploding foil targets. Forward scattered light from foam targets shows evidence that the initial target inhomogeneities remain after the target is laser heated. Forward scattered light from an exploding foil plasma shows that a regular intensity pattern can be used to produce a spatially correlated density fluctuation pattern. These results provide data which can be used to benchmark numerical models of beam spray.
Date: November 1, 1999
Creator: Moody, J.D.; MacGowan, B.J.; Glenzer, S.H.; Kirkwood, R.K.; Kruer, W.L.; Williams, E.A. et al.
Partner: UNT Libraries Government Documents Department

Experimental Investigation of Short Scalelength Density Fluctuations in Laser-Produced Plasmas

Description: The technique of near forward laser scattering is used to infer characteristics of intrinsic and controlled density fluctuations in laser-produced plasmas. Intrinsic fluctuations are studied in long-scale length plasmas where we find that the fluctuations exhibit scale sizes related to the intensity variation scales in the plasma-forming and interaction beams. Stimulated Brillouin forward scattering and filamentation appear to be the primary mechanism through which these fluctuations originate. The beam spray resulting from these fluctuations is important to understand since it can affect symmetry in an inertial confinement fusion (ICF) experiment. Controlled fluctuations are studied in foam and exploding foil targets. Forward scattered light from foam targets shows evidence that the initial target inhomogeneities remain after the target is laser heated. Forward scattered light from an exploding foil plasma shows that a regular intensity pattern can be used to produce a spatially correlated density fluctuation pattern. These results provide data which are being used to benchmark numerical models of beam spray.
Date: January 5, 2000
Creator: Moody, J.D.; MacGowan, B.J.; Glenzer, S.H.; Kirkwood, R.K.; Kruer, W.L.; Montgomery, D.S. et al.
Partner: UNT Libraries Government Documents Department