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Simultaneous measurement of the average ion-induced electron emission yield and the mean charge for isotachic ions in carbon foils

Description: Article discussing the simultaneous measurement of the average ion-induced electron emission yield and the mean charge for isotachic ions in carbon foils.
Date: February 1997
Creator: Arrale, A. M.; Zhao, Z. Y.; Kirchhoff, J. F.; Weathers, Duncan L.; McDaniel, Floyd Del. (Floyd Delbert), 1942- & Matteson, Samuel E.
Partner: UNT College of Arts and Sciences

X-ray emission from colliding laser plasmas

Description: Colliding Au, CD and Ti-Cr plasmas have been generated by illuminating two opposing foils each with a {approximately} 100J, 0.5 nsec, 2{omega} Nd-glass laser beam from the Trident laser facility at Los Alamos. The plasmas are being used to study plasma interactions which span the parameter regime from interpenetrating to collisional stagnation. X-ray emission during the laser target interaction and the subsequent collision is used to diagnose the initial plasma conditions and the colliding plasma properties. X-ray instrumentation consists of a 100 ps gated x-ray pinhole imager, a time-integratcd bremsstrahlung x-ray spectrograph and a gated x-ray spectrograph used to record isoelectronic spectra from the Ti-Cr plasmas. The imager has obtained multi-frame images of the collision and therefore, a measure of the stagnation length which is a function of the ion charge state and density and a strong function of the electron temperature. Other instrumentation includes a Thomson scattering spectrometer with probe beam, neutron detectors used to monitor the CD coated foil collisions and an ion spectrometer. We will describe the current status of the experiments and current results with emphasis on the x-ray emission diagnostics. We will also briefly describe the modeling using Lasnex and ISIS, a particle-in-cell code with massless fluid electrons and inter particle (classical) collisions.
Date: September 1, 1995
Creator: Wilke, M.; Obst, A.W. & Winske, D.
Partner: UNT Libraries Government Documents Department

Potential enhancement of warm x-ray dose from a reflexing bremsstrahlung diode

Description: The potential for generating intense bursts of war x rays (20 to 60 keV) using electron reflexing diodes on pulsed-power accelerators is evaluated with the TIGER Monte Carlo code, showing that hundreds of kilojoules of warm x rays can be generated under idealized conditions. The calculation are compared with data from Gamble-II experiments and applied to two suggest Jupiter (60-MA, 5-MV, 100-ns) diode configurations. If the simultaneous irradiation from the high-energy tail of the bremsstrahlung which accompanies the warm x rays is a concern, then the reflexing technique is shown to be limited to the irradiation of targets thinner than {approximately} 400 {mu}m for low-Z targets like aluminum and thinner than {approximately} 5 {mu}m for high-Z targets like gold.
Date: July 1, 1995
Creator: Sanford, T.W.L.; Halbleib, J.A.; Cooperstein, G. & Weber, B.V.
Partner: UNT Libraries Government Documents Department

Development and processing of LEU targets for {sup 99}Mo production-overview of the ANL program

Description: Most of the world`s supply of {sup 99m}Tc for medical purposes is currently produced from the decay of {sup 99}Mo derived from the fissioning of high-enriched uranium (HEU). Substitution of low-enriched uranium (LEU) silicide fuel for the HEU alloy and aluminide fuels used in most current target designs will allow equivalent {sup 99}Mo yields with little change in target geometries. Substitution of uranium metal for uranium oxide films in other target designs will also allow the substitution of LEU for HEU. During 1995, we have continued to study the modification of current targets and processes to allow the conversion from HEU to LEU. A uranium-metal-foil target was fabricated at ANL and irradiated to prototypic burnup in the Indonesian RSG-GAS reactor. Postirradiation examination indicated that minor design modifications will be required to allow the irradiated foil to be removed for chemical processing. Means to dissolve and process LEU foil have been developed, and a mock LEU foil target was processed in Indonesia. We have also developed means to dissolve the LEU foil in alkaline peroxide, where it can be used to replace HEU targets that are currently dissolved in base before recovering and purifying the {sup 99}Mo. We have also continued work on the dissolution of U{sub 3}Si{sub 2} and have a firm foundation on dissolving these targets in alkaline peroxide. The technology-exchange agreement with Indonesia is well underway, and we hope to expand our international cooperations in 1996.
Date: September 1, 1995
Creator: Snelgrove, J.L.; Hofman, G.L. & Wiencek, T.C.
Partner: UNT Libraries Government Documents Department

X-ray spectroscopy and imaging of a plasma collision

Description: The collision of laser-produced plasmas has been diagnosed by x-ray spectroscopy and imaging. The two colliding plasmas are produced on Al thin foils at a distance of 200 to 900 {mu}m irradiated at {lambda} = 0.53 {mu}m with laser intensities of 3 {times} 10{sup 13} to 6 {times} 10{sup 13} W/cm{sup 2}. Interpenetration of the plasmas was visualized by replacing one of the foils material by magnesium. The main diagnostics viewing the inter-target space were time-resolved monochromatic imaging of the 1s{sup 2} 1s3p aluminum line (He{Beta} at {lambda} {minus} 6.635 {Angstrom}). Doppler broadening measurement with a vertical Johann very high resolution spectrograph in the range 6.5--6.7{Angstrom}, space-resolved high resolution spectra of the dielectronic satellites of the 1s-2p 1 yman, space-resolved spectra with a flat-crystal spectrograph in the range 5--7 {Angstrom} and in the range of 43--48 {Angstrom} obtained with a new OHM crystal spectrograph and a pinhole camera. A multifluid eulerian monodimensional hydrodynamic code coupled with a radiative-atomic package provided simulations of the experiments. Hydrodynamic 2D simulations calculating the lateral expansion of the plasma enabled a reliable treatment of reabsorption along the line of sight of the spectrographs. The size the time duration of the collision, the plasma parameters (Te,Ti and ne) in the collision region and interpenetration were measured. The hydrocode simulations give a good understanding of the behavior of the collision in function of intertarget distance and laser intensity.
Date: July 14, 1995
Creator: Chenais-Popovics, C.; Rancu, O. & Renaudin, P.
Partner: UNT Libraries Government Documents Department

Laser acceleration of thin flyers

Description: Laser energy delivered through an optical fiber has been used to accelerate a thin metallic foil to high velocity. Subsequent impact of the foil onto an explosive charge can initiate an explosion. The present computational study addresses the physical processes of laser absorption, energy transport flyer acceleration, and foil impact on HE or on diagnostic materials in associated experiments. The objective has been to gain understanding that will allow optimizing the system for practical HE initiation. The structure of the foil, especially the presence of a thermally insulating layer near the ablation surface, significantly influences foil effectiveness as an initiator. These simulations show a marked effect on the acceleration process by that layer, which influences both the onset of full laser power absorption, and the physical competence of the foil on arrival at the HE. The effect on laser absorption is especially noteworthy at low laser intensity, where foil launch is marginal. A role of the glass fiber in absorbing laser energy and contributing ablated material is seen in the calculations and confirmed by experiments.
Date: August 1, 1995
Creator: Farnsworth, A.V. Jr.
Partner: UNT Libraries Government Documents Department

Thermal/chemical degradation of inorganic membrane materials

Description: The objective of this program is to evaluate the long-term thermal and chemical degradation of inorganic membranes that are developed to separate gases produced by coal combustion and coal gasification. Membrane materials tested include alumina, vycor, platinum foil, and palladium foils. The porosity, permeability, and characterization of physical and chemical changes after exposure to hot gas streams is described.
Date: December 1, 1995
Creator: Krishnan, G.N.; Damle, A.S.; Sanjurjo, A.; Wood, B.J. & Lau, K.H.
Partner: UNT Libraries Government Documents Department

X-ray source production in foil implosion machines

Description: A number of two-dimensional radiation-magneto-hydrodynamic foil implosion calculations are discussed which explore ways of producing warm x-ray sources ({approximately}60 eV) in a reproducible manner and which would permit close-in access to the source. The discussions include the effects of contoured electrodes on the foil implosion and source output, and of tapering the average mass distribution along the length of the foil. Primarily, source evaluation by jet formation and stagnation against a dense stopping block is treated.
Date: September 1, 1995
Creator: Rich, M. & Matuska, W.
Partner: UNT Libraries Government Documents Department

Comparison and analysis of 2-D simulation results with two implosion radiation experiments on the Los Alamos Pegasus I and Pegasus II capacitor banks

Description: Two experiments, PegI-41, conducted on the Los Alamos Pegasus I capacitor bank, and PegII-25, on the Pegasus II bank, consisted of the implosions of 13 mg (nominal), 5 cm radius, 2 cm high thin cylindrical aluminum foils resulting in soft x-ray radiation pulses from the plasma thermalization on axis. The implosions were conducted in direct-drive (no intermediate switching) mode with peak currents of about 4 MA and 5 MA respectively, and implosion times of about 2.5 {micro}s and 2.0 {micro}s. A radiation yield of about 250 kJ was measured for PegII-25. The purpose of these experiments was to examine the physics of the implosion and relate this physics to the production of the radiation pulse and to provide detailed experimental data which could be compared with 2-D radiation-magnetohydrodynamic (RMHD) simulations. Included in the experimental diagnostic suites were faraday rotation and dB/dt current measurements, a visible framing camera, an x-ray stripline camera, time-dependent spectroscopy, bolometers and XRD`S. A comparison of the results from these experiments shows agreement with 2-D simulation results in the instability development, current, and radiation pulse data, including the pulsewidth, shape, peak power and total radiation yield as measured by bolometry. Instabilities dominate the behavior of the implosion and largely determine the properties of the resulting radiation pulse. The 2-D simulations can be seen to be an important tool in understanding the implosion physics.
Date: September 1, 1995
Creator: Peterson, D.L.; Bowers, R.L.; Lebeda, C.F.; Matuska, W.; Benage, J.; Idzorek, G. et al.
Partner: UNT Libraries Government Documents Department

The pressure regime 10 {minus} 750 Mbar: Use of lasers in EOS measurements

Description: The use of intense lasers has long been proposed as a means to generate Mbar pressures in matter for the study of high energy density equations-of-state. This effort has been hampered by technology, mainly by the small spatial scales necessary to obtain the required high intensities and the inability to produce a uniform shock. Recently, the use of smoothed laser beams and indirect drive have led to the reliable production of uniform > 10Mbar shocks in solids over > 0.5 mm surface. Direct laser irradiation can produce shock pressures up to {approx} 30 Mbar. Indirect irradiation using high-Z hohlraums can exceed 100 Mbar. Accelerated foils, where the driver is an indirect x-ray field produced by a kilojoule-class laser, have produced pressures of 750 Mbar. This opens the door to use high power lasers for EOS studies. It is predicted that a megajoule-class laser, such as NIF, will be able to produce energy densities an order of magnitude greater than these.
Date: September 1, 1995
Creator: Cauble, R.; Da Silva, L.B.; Hammel, B.A.; Holmes, N.C.; Lee, R.W.; Perry, T.S. et al.
Partner: UNT Libraries Government Documents Department

High Energy Density Physics technical quarterly, October--December 1994. Volume 3

Description: The High Energy Density Physics Technical Quarterly (formerly the AGEX 2 Technical Quarterly) publishes short technical contributions on above ground experiments that use pulsed power and laser drivers. The Quarterly is intended to provide rapid exposure of timely technical ideas and results as well as a means for documenting High Energy Density Physics progress and scientific quality for the High Energy Density Physics community. Two articles are included in this volume. They are ``Simulation and Analysis of PEGII-25`` and ``Resistor Developments for Atlas Marx Modules``.
Date: September 1, 1995
Partner: UNT Libraries Government Documents Department

Measurements of laser imprint by XUV radiography using an x-ray laser

Description: We have developed a technique for studying the imprint of a laser beam on a thin foil using an x-ray laser as an XUV backlighter and XUV multilayer optics. This technique allows us to measure small fractional variations in the foil thickness due to hydrodynamics imprinted by direct laser irradiation. We present results of imprinted modulation and growth due to a low intensity 0.53 {mu}m drive beam incident on a 2 {mu}m Al foil using a germanium x-ray laser at the Vulcan facility. We present measurements of the modulation due to static RPP, SSD smoothed, and ISI smoothed speckle patterns at 0.53 {mu}m irradiation.
Date: May 30, 1996
Creator: Kalantar, D.H.; DaSilva, L.B. & Glendinning, S.
Partner: UNT Libraries Government Documents Department

Prototype nickel component demonstration. Final report

Description: We have been developing a process to produce high-purity nickel structures from nickel carbonyl using chemical vapor deposition (CVD). The prototype demonstration effort had been separated into a number of independent tasks to allow Los Alamos National Laboratory (LANL) the greatest flexibility in tailoring the project to their needs. LANL selected three of the proposed tasks to be performed--Task 1- system modification and demonstration, Task 2-stainless steel mandrel trials, and Task 4-manufacturing study. Task 1 focused on converting the CVD system from a hot-wall to a cold-wall configuration and demonstrating the improved efficiency of the reactor type by depositing a 0.01-inch-thick nickel coating on a cylindrical substrate. Since stainless steel substrates were preferred because of their low {alpha}-emitter levels, Task 2 evaluated mandrel configurations which would allow removal of the nickel tube from the substrate. The manufacturing study was performed to develop strategies and system designs for manufacturing large quantities of the components needed for the Sudbury Nuetrino Observatory (SNO) program. Each of these tasks was successfully completed. During these efforts, BIRL successfully produced short lengths of 2-inch-diameter tubing and 6-inch-wide foil with levels of {alpha}-radiation emitting contaminants lower than either conventional nickel alloys or electroplated materials. We have produced both the tubing and foil using hot-substrate, cold-wall reactors and clearly demonstrated the advantages of higher precursor efficiency and deposition rate associated with this configuration. We also demonstrated a novel mandrel design which allowed easy removal of the nickel tubing and should dramatically simplify the production of 1.5-meter-long tubes in the production phase of the program.
Date: November 14, 1994
Creator: Boss, D.E.
Partner: UNT Libraries Government Documents Department

Measurement of local gain and electron density in an yttrium x-ray laser amplifier

Description: X-ray lasers have measured average gains significantly less than calculated and a persistently low level of spatial coherence. We have used an X-ray laser both as an injected signal to a short X-ray laser amplifier and as an interferometer beam to measure two dimensional local gain and density profiles of the X-ray laser plasma with near-1- mm resolution. The measured local gain is in agreement with atomic models, but its gain is unexpectedly spatially inhomogeneous. This inhomogeneity explains the low level of spatial coherence observed and helps explain the disparity between observed and simulated gains.
Date: May 1, 1996
Creator: Cauble, R.; Da Silva, L.B.; Barbee, T.Jr.; Celliers, P.; Decker, C.; London, R.A. et al.
Partner: UNT Libraries Government Documents Department

High current CW beam profile monitors using transisiton radiation at CEBAF

Description: One way of measuring the profile of CEBAF`s low emittance and high power beam is to use the Optical Transition Radiation (OTR) emitted from a thin foil surface when the electron beam passes through it. We present the design of a monitor using the forward OTR emitted from a 0.25 {mu}m carbon foil. We believe that the monitor will resolve three main issues: (i) whether the max temperature of the foil stays below the melting point, (ii) whether the beam loss remains below 0. 5%, in order not to trigger the machine protection system, and (iii) whether the monitor resolution (unlike that of synchrotron radiation monitors) is better than the product {lambda}{gamma}. It seems that the most serious limitation for CEBAF is the beam loss due to beam scattering. We present results from Keil`s theory and simulations from the computer code GEANT as well as measurements with Al foils with a 45 MeV electron beam. We also present a measurement of a 3.2 GeV beam profile that is much smaller than {lambda}{gamma}, supporting Rule & Fiorito`s calculations of the OTR resolution limit due to diffraction.
Date: July 1, 1996
Creator: Piot, P.; Denard, J.C.; Adderley, P; Capek, K. & Feldl, E.
Partner: UNT Libraries Government Documents Department

Stress level evaluation of thin films under thermal loading from a brazing process

Description: X-ray front end beamline windows are made of thin beryllium foil that is commonly brazed or diffusion bonded onto a copper frame. In the brazing process, due to differences in the thermal expansion coefficient of the beryllium and copper materials, the beryllium film ends up in a state of very high level compression stress after cooling from 700{degrees}C (the brazing temperature) to room temperature. This makes the thin Be foil deform into a dome-shaped structure due to the usual asymmetrical geometry of the window. This paper studies the brazing process using a finite element method and explains the reason for such phenomena. Recommendations are offered for possible improvement in the bonding process of beryllium to the window block.
Date: June 1, 1996
Creator: Wang, Z. & Kuzay, T.M.
Partner: UNT Libraries Government Documents Department

Reactive multilayer synthesis of hard ceramic foils and films

Description: Disclosed is method for synthesizing hard ceramic materials such as carbides, borides and aluminides, particularly in the form of coatings provided on another material so as to improve the wear and abrasion performance of machine tools, for example. Method involves the sputter deposition of alternating layers of reactive metals with layers of carbon, boron, or aluminum and the subsequent reaction of the multilayered structure to produce a dense crystalline ceramic. The material can be coated on a substrate or formed as a foil which can be coiled as a tape for later use.
Date: December 31, 1993
Creator: Makowiecki, D.M. & Holt, J.B.
Partner: UNT Libraries Government Documents Department

Reports of Jupiter II: Measurements and analysis

Description: This report provides the reaction rate measurements and analyses and the basic data for reaction rate measurements for ZPPR-13C in: The high [sup 240]Pu zone of ZPPR-13C; The high-heavy-metal-volume- fraction zone;The pin zone; The [sup 235]U fuel zone; and the enriched uranium zone. In-cell reaction rate measurements and cell factors for the zone studies in ZPPR Assembly 13C are provided.
Date: December 31, 1986
Partner: UNT Libraries Government Documents Department

Erosion of thin carbon foils by 20 keV and 40 keV Ar{sup +} irradiation

Description: Nominal 2 {mu}g/cm{sup 2} C foils were irradiated with 20 and 40 keV Ar{sup +} ions at fluences up to 1.1x10{sup 16} Ar{sup +}/cm{sup 2}. Foil erosion (determined by measuring changes in angular scatter distribution of 2-keV protons transiting the foil) is observed to reach a constant rate of 3.5 C atoms removed per incident Ar{sup +}. The independence of the sputter yield on foil thickness indicates that interactions leading to sputtering occur within a depth of 0.5 {mu}g/cm{sup 2} of the sputter surface. Using theoretical and TRIM estimates for the backwater sputtering yield, the transmission sputtering yield is a factor of 3-16 times larger than the backward sputtering yield. The fraction of holes created in the foil by Ar{sup +} irradiation linearly increases with fluence above a fluence of 4x10{sup 15} Ar{sup +}/cm{sup 2}, and the foil lifetime is 8.7x10{sup 15} Ar{sup +}/cm{sup 2}.
Date: October 1, 1996
Creator: Funsten, H.O. & Shappirio, M.
Partner: UNT Libraries Government Documents Department

A small economical rolling mill for producing foils used as nuclear targets

Description: A small, economical rolling mill has found extensive use in the Physics Division Target Development Laboratory for producing foils used in atomic and nuclear physics experiments. This apparatus is quite versatile for its size and enables a large fraction of our target foil requirements to be realized in-house. A description of the rolling mill and some examples of targets produced will be given.
Date: November 1, 1996
Creator: Greene, J.P. & Thomas, G.E.
Partner: UNT Libraries Government Documents Department