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The process of interest in this study is the solidification of a molten metal subjected to rapid pressurization. Most details about solidification occurring when the liquid-solid coexistence line is suddenly transversed along the pressure axis remain unknown. We present preliminary results from an ongoing study of this process for both simple models of metals (Cu) and more sophisticated material models (MGPT potentials for Ta). Atomistic (molecular dynamics) simulations are used to extract details such as the time and length scales that govern these processes. Starting with relatively simple potential models, we demonstrate how molecular dynamics can be used to study solidification. Local and global order parameters that aid in characterizing the phase have been identified, and the dependence of the solidification time on the phase space distance between the final (P,T) state and the coexistence line has been characterized.

We have developed a compact, 14.7 nm, sub-5 ps x-ray laser source at LLNL together with a Mach-Zehnder type Diffraction Grating Interferometer built at Colorado State University for probing dense, high intensity laser-produced plasmas. The short wavelength and pulse length of the probe reduces refraction and absorption effects within the plasma and minimizes plasma motion blurring. This unique diagnostic capability gives precise 2-D density profile snapshots and is generating new data for rapidly evolving laser-heated plasmas. A review of the results from dense, mm-scale line focus plasma experiments will be described with detailed comparisons to hydrodynamic simulations.

The evaporation of a range of synthetic pore water solutions representative of the potential high-level-nuclear-waste repository at Yucca Mountain, NV is being investigated. The motivation of this work is to understand and predict the range of brine compositions that may contact the waste containers from evaporation of pore waters, because these brines could form corrosive thin films on the containers and impact their long-term integrity. A relatively complex synthetic Topopah Spring Tuff pore water was progressively concentrated by evaporation in a closed vessel, heated to 95 C in a series of sequential experiments. Periodic samples of the evaporating solution were taken to determine the evolving water chemistry. According to chemical divide theory at 25 C and 95 C our starting solution should evolve towards a high pH carbonate brine. Results at 95 C show that this solution evolves towards a complex brine that contains about 99 mol% Na{sup +} for the cations, and 71 mol% Cl{sup -}, 18 mol% {Sigma}CO{sub 2}(aq), 9 mol% SO{sub 4}{sup 2-} for the anions. Initial modeling of the evaporating solution indicates precipitation of aragonite, halite, silica, sulfate and fluoride phases. The experiments have been used to benchmark the use of the EQ3/6 geochemical code in …

Covalently bonded extended phases of molecular solids made of first- and second-row elements at high pressures are a new class of materials with advanced optical, mechanical and energetic properties. The existence of such extended solids has recently been demonstrated using diamond anvil cells in several systems, including N{sub 2}, CO{sub 2},and CO. However, the microscopic quantities produced at the formidable high-pressure/temperature conditions have limited the characterization of their predicted novel properties including high-energy content. In this paper, we present the first experimental evidence that these extended low-Z solids are indeed high energy density materials via milligram-scale high-pressure synthesis, recovery and characterization of polymeric CO (p-CO). Our spectroscopic data reveal that p-CO is a random polymer made of lactonic entities and conjugated C=C with an energy content rivaling or exceeding that of HMX. Solid p-CO explosively decomposes to CO{sub 2} and glassy carbon and thus might be used as an advanced energetic material.

Atmospheric testing of thermonuclear devices during the 1950s and 1960s created a global radiocarbon ({sup 14}C) signal in the environment that has provided a useful tracer and chronological marker in oceanic systems and organisms. The bomb-generated {sup 14}C signal retained in fish otoliths can be used as a permanent, time-specific recorder of the 14C present in ambient seawater, making it a useful tool in age validation of fishes. The goal of this study was to determine {sup 14}C levels in otoliths of the age-validated yelloweye rockfish (Sebastes ruberrimus) to establish a reference time series for the coastal waters of southeast Alaska. Radiocarbon values from the first year's growth of 43 yelloweye rockfish otoliths were plotted against estimated birth year to produce a 14C time series for these waters spanning 1940 to 1990. The time series shows the initial rise of bomb 14C occurred in 1958 in coastal southeast Alaskan waters and {sup 14}C levels rose relatively rapidly to peak {Delta}{sup 14}C values (60-70%) between 1966 and 1971, with a subsequent declining trend through the end of the record in 1990 (-3.2%). In addition, the radiocarbon data, independent of the radiometric study, confirms the longevity of the yelloweye rockfish up to …

Experiment E906 at the BNL-AGS, searching for light S = -2 hypernuclei, found strong evidence for the nuclide {sub {Lambda}{Lambda}}{sup 4}H. Perhaps the most striking feature of this experiment was the presence in the data of a narrow low-momentum {pi}{sup -} line at k{sub {pi}} = 104-105 MeV/c. This line was ascribed to the decay of {sub {Lambda}{Lambda}}{sup 4}H into a resonant state in {sub {Lambda}}{sup 4}H. The existence of such a state is shown to be plausible, its characteristics delineated, and its relevance to ongoing theoretical calculations considered.

The diffusion method is a good approximation inside the dense core of a cloud, but not at the more tenuous boundary regions. Also, it breaks down in regions where the density of scattering droplets is zero. We have enhanced it by using hardware cell projection volume rendering at cloud border voxels to account for the straight line light transport across these empty regions. We have also used this hardware volume rendering at key voxels in the low-density boundary regions to account for the multiple anisotropic scattering of the environment.

We present clear experimental evidence showing that the contribution of bound electrons can dominate the index of refraction of laser created plasmas at soft x-ray wavelengths. We report anomalous fringe shifts in soft x-ray laser interferograms of Al laser-created plasmas. The comparison of measured and simulated interferograms show that this results from the dominant contribution of low charge ions to the index of refraction. This usually neglected bound electron contribution can a.ect the propagation of soft x-ray radiation in plasmas and the interferometric diagnostics of plasmas for many elements.

Amorphous Be-B-X alloys are vapor deposited as coatings. The microstructure and hardness of the Be-B-X coatings are examined using transmission electron microscopy and nanoindentation, respectively. Whereas a Be-B-2.5 at.% Cu amorphous coating is found to crystallize to a cubic Be-33 at.% B phase at 673 K, a coating of Be-B-1.8 at.% Fe-0.4 at.% Cr-0.3 at.% Co does not crystallize until at a higher temperature of 748 K. The hardness of the amorphous Be-B-X coating increases with B content but is less than its crystalline counterparts.

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.

The engineering barriers for the nuclear waste repository at Yucca Mountain include a double walled container and a detached drip shield. The material selected to construct the drip shield will be Titanium Grade 7 (Ti Gr 7 or R52400). Ti Gr 7 is highly resistant to corrosion and consequently it is widely used to handle aggressive industrial environments. The model for the degradation of the engineering barriers includes three modes of corrosion, namely general corrosion, localized corrosion and environmentally assisted cracking (EAC). The objective of the current research was to characterize the susceptibility of three titanium alloys to EAC in several environmental conditions with varying solution composition, pH and temperature. The susceptibility to EAC was evaluated using constant deformation (deflection) U-bend specimens in both the non-welded and welded conditions. Results show that after more than five years exposure in the vapor and liquid phases of alkaline (pH {approx} 10) and acidic (pH {approx} 3) multi-ionic environments at 60 C and 90 C, most of the specimens were free from EAC. The only specimens that suffered EAC were welded Ti Gr 12 (R53400) exposed to liquid simulated concentrated water (SCW) at 90 C.

Measurement and modeling of the 2-D poloidal D{alpha} intensity distribution in DIII-D low and medium density L-mode and ELMy H-mode plasmas indicate that hydrogen neutrals predominantly fuel the core from the divertor X-point region. The 2-D distribution of neutral deuterium and low-charge-state carbon were measured in the divertor and the high-field side midplane scrape-off layer (SOL) using tangentially viewing cameras. The emission in the high-field SOL at the equatorial plane was found to be three to four orders of magnitude lower than at the strike points in the divertor, suggesting a strong divertor particle source. Modeling using the UEDGE/DEGAS codes predicted the poloidal fueling distribution to be dependent on the direction of the ion Bx{Delta}B drift. In plasmas with the Bx{Delta}B drift into the divertor stronger fueling from the inner divertor than from the outer is predicted, due to a lower-temperature and higher-density plasma in the inner leg. UEDGE simulations with carbon produced by both physical and chemical sputtering at the divertor plates and walls only are in agreement with a large set of diagnostic data. The simulations indicate flow reversal in the inner divertor that augments the leakage of carbon ions from the divertor into the core.

The energies of p-shell hypernuclear {gamma} rays obtained from recent experiments using the Hyperball at BNL and KEK are used to constrain the YN interaction which enters into shell-model calculations which include both {Lambda} and {Sigma} configurations.

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.

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 …

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.

An extended structure zone diagram is proposed that includes energetic deposition, characterized by a large flux of ions typical for deposition by filtered cathodic arcs and high power impulse magnetron sputtering. The axes are comprised of a generalized homologous temperature, the normalized kinetic energy flux, and the net film thickness, which can be negative due to ion etching. It is stressed that the number of primary physical parameters affecting growth by far exceeds the number of available axes in such a diagram and therefore it can only provide an approximate and simplified illustration of the growth condition?structure relationships.

We revisit the molecular line growth mechanism of styrene on the hydrogenated Si(001) 2x1 surface. In particular, we investigate the energetics of the radical chain reaction mechanism by means of diffusion quantum Monte Carlo (QMC) and density functional theory (DFT) calculations. For the exchange correlation (XC) functional we use the non-empirical generalized-gradient approximation (GGA) and meta-GGA. We find that the QMC result also predicts the intra dimer-row growth of the molecular line over the inter dimer-row growth, supporting the conclusion based on DFT results. However, the absolute magnitudes of the adsorption and reaction energies, and the heights of the energy barriers differ considerably between the QMC and DFT with the GGA/meta-GGA XC functionals.

We have started upgrading the control room programs for the injector at the Advanced Light Source (ALS). We chose to program in C* exclusively on the .NET Framework to create EPICS client programs on Windows Vista PCs. This paper reports the status of this upgrade project.

We report the demonstration of a reflection microscope that operates at 13.2-nm wavelength with a spatial resolution of 55 {+-} 3 nm. The microscope uses illumination from a table-top EUV laser to acquire aerial images of photolithography masks with a 20 second exposure time. The modulation transfer function of the optical system was characterized.

Chromosomal mosaicism in human preimplantation embryos is a common cause ofspontaneous abortions, however, our knowledge of its etiology is limited. We used multicolor fluorescence in situ hybridization (FISH) painting to investigate whether paternally-transmitted chromosomal aberrations result in mosaicism in mouse 2-cell embryos. Paternal exposure to acrylamide, an important industrial chemical also found in tobacco smoke and generated during the cooking process of starchy foods, produced significant increases in chromosomally defective 2-cell embryos, however, the effects were transient primarily affecting the postmeiotic stages of spermatogenesis. Comparisons with our previous study of zygotes demonstrated similar frequencies of chromosomally abnormal zygotes and 2-cell embryos suggesting that there was no apparent selection against numerical or structural chromosomal aberrations. However, the majority of affected 2-cell embryos were mosaics showing different chromosomal abnormalities in the two blastomeric metaphases. Analyses of chromosomal aberrations in zygotes and 2-cell embryos showed a tendency for loss of acentric fragments during the first mitotic division ofembryogenesis, while both dicentrics and translocations apparently underwent propersegregation. These results suggest that embryonic development can proceed up to the end of the second cell cycle of development in the presence of abnormal paternal chromosomes and that even dicentrics can persist through cell division. The high …

We report the scaling behavior of Barkhausen avalanches for every small field step along the hysteresis loop in CoCrPt alloy film having perpendicular magnetic anisotropy. Individual Barkhausen avalanche is directly observed utilizing a high-resolution soft X-ray microscopy that provides real space images with a spatial resolution of 15 nm. Barkhausen avalanches are found to exhibit power-law scaling behavior at all field steps along the hysteresis loop, despite their different patterns for each field step. Surprisingly, the scaling exponent of the power-law distribution of Barkhausen avalanches is abruptly altered from 1 {+-} 0.04 to 1.47 {+-} 0.03 as the field step is close to the coercive field. The contribution of coupling among adjacent domains to Barkhausen avalanche process affects the sudden change of the scaling behavior observed at the coercivity-field region on the hysteresis loop of CoCrPt alloy film.