Thin-disk laser configurations have recently been demonstrated at cw output povters exceeding 1 kW [1]. Thin-disk lasers enable the generation of high average power by minimizing the distance over which waste heat is transported. A disk-laser of transverse dimensions significantly larger than its thickness will sustain laser output with intensity proportional to the thermal flux it dissipates. The fracture strength of the laser material limits the maximum temperature difference of a credible design. Further increases in the heat dissipation capacity of a disk varies inversely with the disk thickness (t) thus, the average laser output intensity of a thin/disk laser scales as 1/t; that is, to maximize the output intensity we must use the thinnest possible disk that is consistent with the pump geometry. The main challenge for the laser designer is then to coerce a thin gain sample into absorbing pump power efficiently. For this purpose, use of a highly absorbing gain medium is desirable in combination with a pumping geometry that allows multi-passing of the pump light. An important feature of the thin-disk laser is that one-dimensional thermal gradients away from the edges are made to align with the extraction beam Thus, as long as pumping and cooling …

Accurate predictions of a polymer component's functional lifetime at best arc tenuous when one has only relatively short term chemical or mechanical property data to extrapolate. We have analyzed a series of silica-filled siloxanes to determine the chemical and microstructural signatures of aging, and we are incorporating these data into rational methodologies for assessing a component's lifetime measured against as-designed engineering properties. We are monitoring changes in mechanical properties, crystallization kinetics, cross-link density changes, and motional dynamics with a variety of analysis methods: Modulated DSC, Dynamic Mechanical Analysis, and Solid-state Nuclear Magnetic Resonance. Previous work has shown that the addition of phenyl side groups to polydimethylsiloxane (PDMS) polymer chains reduces the rate and extent of crystallization of the co-polymer compared to that of pure PDMS. Crystallization has been observed in copolymer systems up to 6.5 mol % phenyl composition by DSC and up to 8 mol % phenyl by XRD. The PDMS-PDPS-silica composite materials studied here are silica reinforced random block copolymers consisting of dimethyl and diphenyl monomer units with 11.2 mol. % polydiphenylsiloxane. Based on this previous work, it is not expected that this material would exhibit crystallization in the polymer network; however, these silicones do, in fact, exhibit …

A semi-quantitative map based on a series of spatially resolved X-ray diffraction (SRXRD) scans shows the progression of the ferrite ({delta})/austenite ({gamma}) phase balance throughout the HAZ during GTA welding of a 2205 duplex stainless steel (DSS). This map shows an unexpected decrease in the ferrite fraction on heating, followed by a recovery to the original ferrite fraction on cooling at locations within the HAZ. Even though such behavior is supported by thermodynamic calculations, it has not been confirmed by either experimental methods or have the kinetics been evaluated. Both Gleeble thermal simulations and time resolved x-ray diffraction measurements on spot welds in the 2205 DSS provide further evidence for this rather low-temperature transformation. On the other hand, calculations of the diffusion of alloying elements across the 6/y interface under a variety of conditions shed no further light on the driving force for this transformation. Further work on the mechanisms and driving forces for this transformation is on-going.

Beams for heavy-ion fusion (HIF) are expected to require substantial neutralization in a target chamber. Present targets call for higher beam currents and smaller focal spots than most earlier designs, leading to high space-charge fields. Collisional stripping by the background gas expected in the chamber further increases the beam charge. Simulations with no electron sources other than beam stripping and background-gas ionization show an acceptable focal spot only for high ion energies or for currents far below the values assumed in recent HIF power-plant scenarios. Much recent research has, therefore, focused on beam neutralization by electron sources that were neglected in earlier simulations, including emission from walls and the target, photoionization by radiation from the target, and pre-neutralization by a plasma generated along the beam path. The simulations summarized here indicate that these effects can significantly reduce the beam focal-spot size.

Prior studies of evaporation and sputter deposition show that the grain size of pure beryllium can be dramatically refined through the incorporation of metal impurities. Recently, the addition of boron at a concentration greater than 11% is shown to serve as a glassy phase former in sputter deposited beryllium. Presently, thermally induced crystallization of the beryllium-boron metallic glass is reported. The samples are characterized during an in-situ anneal treatment with bright field imaging and electron diffraction using transmission electron microscopy. A nanocrystalline structure evolves from the annealed amorphous phase and the crystallization temperature is affected by the boron concentration.

The Scaled Thermal Explosion Experiment (STEX) has been developed to quantify the violence of thermal explosion under well defined and carefully controlled initial and boundary conditions. Here we present results with HMX-based explosives (LX-04 and PBX-9501) and with Composition B. Samples are 2 inches (50 mm) in diameter and 8 inches (200 mm) in length, under confinement of 7,500-30,000 psi (50-200 MPa), with heating rates of 1-3 C/hr. We quantify reaction violence by measuring the wall velocity in the ensuing thermal explosion, and relate the measured velocity to that expected from a detonation. Results with HMX-based explosives (LX-04 and PBX-9501) have shown the importance of confinement and HMX solid phase, with reaction violence ranging from mild pressure bursts to near detonations. By contrast, Composition B has shown very violent reactions over a wide range of conditions.

Thermal cycling was used as a means to control density in the preparation of Insensitive High Explosive (IHE) specimens slated for performance testing. These samples were thermally cycled between -55 degrees C and 70 degrees C and their densities measured using hydrostatic weighing, an immersion density measurement technique. Bulk sample densities were reduced by as much as 1.5% over 40 thermal cycles. In these thermal cycling studies, the effects of several parameters were investigated. These parameters included different ME composites (LX-17 and PBX 9502), different pressing mechanisms (die-pressed and isostatically-pressed) and sample size.

Surfaces generated by scientific simulation and range scanning can reach into the billions of polygons. Such surfaces must be aggressively compressed, but at the same time should provide for level of detail queries. Progressive compression techniques based on subdivision surfaces produce impressive results on range scanned models. However, these methods require the construction of a base mesh which parameterizes the surface to be compressed and encodes the topology of the surface. For complex surfaces with high genus and/or a large number of components, the computation of an appropriate base mesh is difficult and often infeasible. We present a surface compression method that stores surfaces as wavelet-compressed signed-distance volumes. Our method avoids the costly base-mesh construction step and offers several improvements over previous attempts at compressing signed-distance functions, including an {Omicron}(n) distance transform, a new zero set initialization method for triangle meshes, and a specialized thresholding algorithm. We demonstrate the potential of sampled distance volumes for surface compression and progressive reconstruction for complex high genus surfaces.

The characteristics of the particle emitting source are deduced from low p{sub T} identified hadron spectra ((m{sub T}-m0) < 1 GeV) and HBT radii using a hydrodynamic interpretation. From the most peripheral to the most central data, the single particle spectra are fit simultaneously for all {pi}{sup {+-}}, K{sup {+-}}, and {bar p}/p using the parameterization in [1] and assuming a linear transverse flow profile. Within the systematic uncertainties, the expansion parameters T{sub fo} and {beta}{sub T}, respectively decrease and increase with the number of participants, saturating for both at mid-centrality. The expansion using analytic calculations of the k{sub T} dependence of HBT radii in [2] is fit to the data but no {chi}{sup 2} minimum is found.

The authors present a numerical method to model non-Newtonian, viscoelastic flow at the microscale. The equations of motion are the incompressible Navier-Stokes equations coupled with the Oldroyd-B constitutive equation. This constitutive equation is chosen to model a Boger fluid which is representative of complex biological solutions exhibiting elastic behavior due to macromolecules in the solution (e.g., DNA solution). The numerical approach is a projection method to impose the incompressibility constraint and a Lax-Wendroff method to predict velocities and stresses while recovering both viscous and elastic limits. The method is second-order accurate in space and time, free-stream preserving, has a time step constraint determined by the advective CFL condition, and requires the solution of only well-behaved linear systems amenable to the use of fast iterative methods. They demonstrate the method for viscoelastic incompressible flow in simple microchannels (2D) and microducts (3D).

Lawrence Livermore National Laboratory is currently involved in a long term study using time-lapse multiple frequency electromagnetic (EM) imaging at a carbon dioxide (CO{sub 2}) enhanced oil recovery (EOR) site in the San Joaquin Valley, California. The impetus for this proposed research project is to develop the ability to image subsurface CO{sub 2} during EOR processes while simultaneously discriminating between background heavy petroleum and water deposits. Using field equipment developed at Lawrence Livermore National Laboratory in prior imaging studies of EOR water and steam injection, this research uses multiple field deployments to acquire subsurface image snapshots of the CO{sub 2} injection and displacement. Laboratory research, including electrical and transport properties of fluid and CO{sub 2} in saturated materials, uses core samples from drilling, as well as samples of injection and formation fluid provided by industrial partners on-site. Our two-fold approach to combine laboratory and field methods in imaging a pilot CO{sub 2} sequestration EOR site using the cross-borehole EM technique is to (1) improve the inversion process in CO{sub 2} studies by coupling field results with petrophysical laboratory measurements and (2) focus on new gas interpretation techniques of the field data using multiple frequencies and low noise data processing techniques. …

The addition of oxygenates to diesel fuel can reduce particulate emissions, but the underlying chemical pathways for the reductions are not well understood. While measurements of particulate matter (PM), unburned hydrocarbons (HC), and carbon monoxide (CO) are routine, determining the contribution of carbon atoms in the original fuel molecules to the formation of these undesired exhaust emissions has proven difficult. Renewable bio-derived fuels (ethanol or bio-diesel) containing a universal distribution of contemporary carbon are easily traced by accelerator mass spectrometry (AMS). These measurements provide general information about the emissions of bio-derived fuels. Another approach exploits synthetic organic chemistry to place {sup 14}C atoms in a specific bond position in a specific fuel molecule. The highly labeled fuel molecule is then diluted in {sup 14}C-free petroleum-derived stock to make a contemporary petroleum fuel suitable for tracing. The specific {sup 14}C atoms are then traced through the combustion event to determine whether they reside in PM, HC, CO, CO{sub 2}, or other emission products. This knowledge of how specific molecular structures produce certain emissions can be used to refine chemical-kinetic combustion models and to optimize fuel composition to reduce undesired emissions. Due to the high sensitivity of the technique and the lack …

A new Detonation Profile Test (DPT) was developed to measure simultaneously the detonation wave breakout profile and the average detonation velocity at the breakout surface. The test evaluated small cylindrical samples with diameter up to 19.08 mm and length up to 33 mm. The experiment involved initiating a LX-17 cylindrical specimen and recording the wave breakout using a fast streaking electronic camera. The initiation was done using a PBX-9407 pellet (1.630 g/cm{sup 3}), which has a Chapman-Jouguet (C-J) pressure close to that of LX-17. The acceptor breakout surface had a 2 mm wide by 1 mm deep groove that provided a step in the recorded breakout profile for velocity determination. A 532-nm laser light illuminated the specimen surface. A streak camera looking perpendicular to the groove, recorded the extinction of the laser light as the detonation wave emerged from the surface. This technique provided a high-resolution spatial and temporal profile of the wave curvature as well as accurate timing of the propagating wave over the last millimeter of the sample. The measured groove depth and recorded travel time were then used to calculate the average detonation wave velocity. Results for 12.7 mm diameter unconfined LX-17 charges showed detonation velocity in …

We report on the performance of an S-band RF photocathode electron gun and accelerator for operation with the PLEIADES Thomson x-ray source at LLNL. Simulations of beam production, transport, and focus are presented. It is shown that a 1 ps, 500 pC electron bunch with a normalized emittance of less than 5 {pi}mm-mrad can be delivered to the interaction point. Initial electron measurements are presented. Calculations of expected x-ray flux are also performed, demonstrating an expected peak spectral brightness of 10{sup 20} photons/s/mm{sup 2}/mrad{sup 2}/0.1% bandwidth. Effects of RF phase jitter are also presented, and planned phase measurements and control methods are discussed.

LCS experiments were carried out at the Idaho Accelerator Center (IAC); sharp monochromatic x-ray lines were observed. These are produced using the so-called inverse Compton effect, whereby optical laser photons are collided with a relativistic electron beam. The back-scattered photons are then kinematically boosted to keV x-ray energies. We have first demonstrated these beams using a 20 MeV electron beam collided with a 100 MW, 7 ns Nd; YAG laser. We observed narrow LCS x-ray spectral peaks resulting from the interaction of the electron beam with the Nd; YAG laser second harmonic (532 nm). The LCS x-ray energy lines and energy deviations were measured as a function of the electron beam energy and enery-spread respectively. The results showed good agreement with the predicted valves. LCS could provide an exellent probe of electron beam energy, energy spread, transverse and longitudinal distribution and direction.

The question of the anisotropy of the electron scattering in high temperature superconductors is investigated using high resolution angle-resolved photoemission data from Pb-doped Bi2Sr2CaCu2O8(Bi2212) with suppressed superstructure. The scattering rate of low energy electrons along two bilayer split pieces of the Fermi surface is measured (via the quasiparticle peak width), and no increase of scattering towards the antinode (Pi,0) region is observed, contradicting the expectation from Q=(Pi, Pi) scattering. The results put a limit on the effects of Q=(Pi, Pi) scattering on the electronic structure of this overdoped superconductor with still very high Tc.

Tobacco-specific N'-nitrosamines (TSNA) are a unique class of systemic organ-specific carcinogens. The TSNA are formed by N-nitrosation of nicotine and of the minor tobacco alkaloids after harvesting of tobacco and during smoking. The N-nitrosation of anatabine leads to N'-nitrosoanatabine (NAT; 1-nitroso-1,2,3,4-tetrahydro-2,3'-bipyridyl) which requires in-depth assays in laboratory animals other than the rat. Furthermore, delineation of its tissue distribution and metabolism is needed for structure:activity comparisons with other TSNA and for the assessment of potential human risk from this TSNA. We have, therefore, synthesized (+)[5-3H]NAT. 5-Bromo-3-pyridine-carboxaldehyde was condensed with ethyl carbamate prior to Diels-Alder reaction with 1,4-butadiene to give the racemic anatabine ring system. Hydrolysis followed by reduction with LiAlT4 and nitrosation, led to (+)[5-3H]NAT (60 percent yield, specific activity 266 mCi/mmol, radiochemical purity of >99 percent).

The Advanced Light Source (ALS) at the E.O. Lawrence Berkeley National Laboratory (Berkeley Lab) of the University of California is a ''third-generation'' synchrotron radiation source optimized for highest brightness at ultraviolet and soft x-ray photon energies. It also provides world-class performance at hard x-ray photon energies. Berkeley Lab operates the ALS for the United States Department of Energy as a national user facility that is available 24 hours/day around the year for research by scientists from industrial, academic, and government laboratories primarily from the United States but also from abroad.

Dantrolene is a drug that suppresses intracellular Ca2+ release from sarcoplasmic reticulum in normal skeletal muscle and is used as a therapeutic agent in individuals susceptible to malignant hyperthermia. Though its precise mechanism of action has not been elucidated, we have identified the N-terminal region (amino acids 1-1400) of the skeletal muscle isoform of the ryanodine receptor (RyR1), the primary Ca2+ release channel in sarcoplasmic reticulum, as a molecular target for dantrolene using the photoaffinity analog [3H]azidodantrolene(1). Here, we demonstrate that heterologously expressed RyR1 retains its capacity to be specifically labeled with [3H]azidodantrolene,indicating that muscle specific factors are not required for this ligand-receptor interaction. Synthetic domain peptides of RyR1, previously shown to affect RyR1 function in vitro and in vivo, were exploited as potential drug binding site mimics and used in photoaffinity labeling experiments. Only DP1 and DP1-2, peptide s containing the amino acid sequence corresponding to RyR1 residues 590-609, were specifically labeled by [3H]azidodantrolene. A monoclonal anti-RyR1 antibody which recognizes RyR1 and its 1400 amino acid N-terminal fragment, recognizes DP1 and DP1-2 in both Western blots and immunoprecipitation assays, and specifically inhibits [3H]azidodantrolene photolabeling of RyR1 and its N-terminal fragment in sarcoplasmic reticulum. Our results indicate that synthetic domain …

A multi-beamlet approach to a high current ion injector, whereby a large number of beamlets are accelerated and then merged to form a single beam, offers a number of potential advantages over a monolithic single beam injector. These advantages include a smaller transverse footprint, more control over the shaping and aiming of the beam, and more flexibility in the choice of ion sources. A potential drawback however is a larger emittance. In this paper, we seek to understand the merging of the beamlets and how it determines the emittance. When the constraints imposed by beam propagation physics and practical engineering issues are included, the design is reduced to a few free parameters. We describe the physics design of a multi-beamlet injector, and produce a design for an example set of parameters. Extensive use of 2-D and 3-D particle simulations was made in understanding the injector. Design tolerances and sensitivities are discussed in general and in relation to the example.

Recent analyses of multifragmentation in terms of Fisher's model and the related construction of a phase diagram brings forth the problem of the true existence of the vapor phase and the meaning of its associated pressure. Our analysis shows that a thermal emission picture is equivalent to a Fisher-like equilibrium description which avoids the problem of the vapor and explains the recently observed Boltzmann-like distribution of the emission times. In this picture a simple Fermi gas thermometric relation is naturally justified. Low energy compound nucleus emission of intermediate mass fragments is shown to scale according to Fisher's formula and can be simultaneously fit with the much higher energy ISiS multifragmentation data.

Water infiltrating down a fracture in unsaturated rock experiences complex fluid-flow and heat-transfer phenomena when entering above-boiling rock temperature regions. Such conditions are expected, for example, after emplacement of heat-generating nuclear waste in underground repositories. A new, efficient semi-analytical method is proposed in this paper that simulates the flow processes of infiltration events subject to vigorous boiling from the adjacent hot rock. It is assumed that liquid flow forms in localized preferential flow paths, and that infiltration events are typically short in duration but large in magnitude relative to the average net infiltration. The new solution scheme is applied to several test cases studying sensitivity to a variety of input parameters. Sample simulations are performed for conditions representative of the potential nuclear waste repository at Yucca Mountain, Nevada. A characteristic parameter is introduced that provides a quick estimate of the relative significance of boiling at a given location of interest.

High impact publication on innovative work to understand magnetic coupling in magnetic insulators and how to evaluate accurately the magnetic coupling constants.

CuPt-type ordering in In{sub 0.49}Al{sub 0.51}P is studied by TEM. The lattice-matched film was grown by MOCVD on a GaAs substrate oriented 10{sup o} off (001) towards [110], at 650 C and 25 nm/min. TEM [110] and [1{bar 1}0] cross-sections (XS) were made by wedge polishing and 2 kV Ar ion milling. In CuPt-type ordering of In{sub 0.52}Ga{sub 0.48}P, alternating In-Ga-In-Ga {l_brace}111{r_brace} planes of group III atoms produce 1/2 {bar 1}11 and 1/2 1{bar 1}1 order spots in the 110 SADP, while the [1{bar 1}0] SADP shows no order spots [1-3]. A few studies have reported this type of order in In{sub 0.49}Al{sub 0.51}P [4]. The 004 BF image of the [1{bar 1}0] XS in Fig. 1 shows uneven light/dark contrast modulation due to phase separation often observed in In{sub 0.52}Ga{sub 0.48}P. There are also light/dark layers marked ML parallel to the film growth plane; such unintentional multilayers have also been observed [5] but their origin is not understood. Order lamellae {approx}1.5 nm thick inclined at a shallow angle to the growth plane overlap the multilayer to produce Moire fringe contrast. Fig. 2 is a DF image showing the thin ordered domains in the [1{bar 1}0] XS, which are inclined …