A novel handheld time-domain array GPR antipersonnel mine detection system using an offset paraboloidal reflector antenna is described. The reflector collimates rays from an ultra-wideband transmitting feed, directing the microwave impulse forward, in front of the antenna structure. As such, much of the ground reflected wave is directed further forward, away from the operator, the reflector, and the receiving antennas, and thereby reducing the major source of clutter. The wave transmitted into the ground that interacts with the target, generating significant backscatter returning toward the receiving antennas. These receiving antennas are configured in a 2 by 2 array to provide spatial focusing in both the along- and cross-track directions. This system has been built and tested at both Lawrence Livermore National Laboratory, and GeoCenters, Inc. In both cases, custom-built wideband antenna elements generate narrow pulse shapes, which allow for resolving small non-metallic targets buried at shallow depths. The LLNL's Micro-Power Impulse Radar (MIR) operates in the 1.5 to 5 GHz range a very narrow pulse shape. The Geo-Centers wideband TEMR antenna elements have higher power, though lower frequency range (850 to 1700 MHz), and generate less residual ringing in the time signal. Preliminary measured data from both systems indicate that …

Multi-resolution techniques and models have been shown to be effective for the display and transmission of large static geometric object. Dynamic environments with internally deforming models and scientific simulations using dynamic meshes pose greater challenges in terms of time and space, and need the development of similar solutions. In this paper we introduce the T-DAG, an adaptive multi-resolution representation for dynamic meshes with arbitrary deformations including attribute, position, connectivity and topology changes. T-DAG stands for Time-dependent Directed Acyclic Graph which defines the structure supporting this representation. We also provide an incremental algorithm (in time) for constructing the T-DAG representation of a given input mesh. This enables the traversal and use of the multi-resolution dynamic model for partial playback while still constructing new time-steps.

We explore how nuclear modifications to the nucleon structure functions, shadowing, affect massive gauge boson production in heavy ion collisions at different impact parameters. We calculate the dependence of Z{sup 0}, W{sup +} and W{sup -} production on rapidity and impact parameter to next-to-leading order in Pb+Pb collisions at 5.5 TeV/nucleon to study quark shadowing at high Q{sup 2}. We also compare our Pb+Pb results to the pp rapidity distributions at 14 TeV.

The two-dimensional Steven impact test has been developed to be reproducible and amenable to computer modeling. This test has a hemispherical projectile traveling at tens of m/s impacting a metal cased explosive target. To assist in the understanding of this safety test, two-dimensional shock wave gauge techniques were used to measure the pressures of a few kilobars and times of reactions less than a millisecond. This work is in accord with a long-term goal to develop two-dimensional shock diagnostic techniques that are more than just time of arrival indicators. Experiments were performed where explosives were impacted at levels below shock initiation levels but caused low level reactions. Carbon foil and carbon resistor pressure gauges were used to measure pressures and time of events. The carbon resistor gauges indicate a late time low level reaction at 350 {micro}s after impact of the hemispherical projectile creating 0.5-6 kb peak shocks at the center of PBX 9501 (HMX/Estane/BDNPA-F; 95/2.5/2.5 wt %) explosive discs. The Steven test calculations are based on an ignition and growth criteria and found that the low level reaction occurs at 335 {micro}s, which is in good agreement with the experimental data. Some additional experiments simulating the Steven impact test …

Sea quark distributions in the nucleon have naively been expected to be generated perturbatively by gluon splitting. In this case, there is no reason for the light quark and anti-quark sea distributions to be different. No asymmetries in the strange or heavy quark sea distributions are predicted in the improved parton model. However,recent experiments have called these naive expectations into question. A violation of the Gottfried sum rule has been measured in several experiments, suggesting that (bar u) < (bar d) in the proton. Additionally, other measurements, while not definitive, show that there may be an asymmetry in the strange and anti-strange quark sea distributions. These effects may require nonperturbative explanations. In this review we first discuss the perturbative aspects of the sea quark distributions. We then describe the experiments that could point to nonperturbative contributions to the nucleon sea. Current phenomenological models that could explain some of these effects are reviewed.

We describe a diagnostics system developed, to measure exponential gain properties and the electron beam dynamics inside the strong focusing 4-m long undulator for the VISA (Visible to Infrared SASE Amplifier) FEL. The technical challenges included working inside the small undulator gap, optimizing the electron beam diagnostics in the high background environment of the spontaneous undulator radiation, multiplexing and transporting the photon beam. Initial results are discussed.

Low Power EM radar-like sensors have made it possible to measure properties of the human speech production system in real-time, without acoustic interference. This greatly enhances the quality and quantity of information for many speech related applications. See Holzrichter, Burnett, Ng, and Lea, J. Acoustic. SOC. Am . 103 ( 1) 622 (1998). By combining the Glottal-EM-Sensor (GEMS) with the Acoustic-signals, we've demonstrated an almost 10 fold reduction in error rates from a speaker verification system experiment under a moderate noisy environment (-10dB).

GRB 990123 established the existence of prompt optical emission from gamma-ray bursts (GRBs). The Livermore Optical Transient Imaging System (LOTIS) has been conducting a fully automated search for this kind of simultaneous low energy emission from GRBs since October 1996. Although LOTIS has obtained simultaneous, or near simultaneous, coverage of the error boxes obtained with BATSE, IPN, XTE, and BeppoSAX for several GRBs, image analysis resulted in only upper limits. The unique gamma-ray properties of GRB 990123, such as very large fluence (top 0.4%) and hard spectrum, complicate comparisons with more typical bursts. We scale and compare gamma-ray properties, and in some cases afterglow properties, from the best LOTIS events to those of GRB 990123 in an attempt to determine whether the prompt optical emission of this event is representative of all GRBs. Furthermore, using LOTIS upper limits in conjunction with the relativistic blast wave model, we weakly constrain the GRB and afterglow parameters such as density of the circumburster medium and bulk Lorentz factor of the ejecta.

Controlling composition at the nanometer scale is well known to alter material properties in sometimes highly desirable and dramatic ways. In the field of energetic materials component distributions, particle size, and morphology, effect both sensitivity and reactivity performance. To date nanostructured energetic materials are largely unknowns with the exception of nanometer-sized reactive powders now being produced at a number of laboratories. We have invented a new method of making nanostructured energetic materials, specifically explosives, propellants, and pyrotechnics, using sol-gel chemistry. The ease of this synthetic approach along with the inexpensive, stable, and benign nature of the metal precursors and solvents permit large-scale syntheses to be carried out. This approach can be accomplished using low cost processing methods. We will describe here, for the first time, this new synthetic route for producing metal-oxide-based pyrotechnics. The procedure employs the use of stable and inexpensive hydrated-metal inorganic salts and environmentally friendly solvents such as water and ethanol. The synthesis is straightforward and involves the dissolution the metal salt in a solvent followed by the addition of an epoxide, which induces gel formation in a timely manner. Experimental evidence suggests that the epoxide acts as an irreversible proton scavenger that induces the hydrated-metal species …

In December 1999 and January 2000, a 40-cm-thick spherical shell of sprayable concrete (''gunite'') was applied to the exterior surface of the National Ignition Facility (NIF) target chamber. Glow-discharge mass spectroscopy has been to determine the elemental composition of multiple gunite samples, which were collected at the time of application. These measured compositions are compared to the anticipated composition and both are used for neutron activation calculations. Contact dose rates are reported and implications for doses rates during operation and for the eventual facility decommissioning are discussed.

A critical issue for a Two-Beam accelerator based upon extended relativistic klystrons is controlling the cumulative dipole instability growth We describe a theoretical scheme to reduce the growth from an exponential to a more manageable linear rate, and a new experiment to test this concept. The experiment utilizes a 1-MeV, 600-Amp, 200-ns electron beam and a short beamline of periodically spaced RF dipole pillbox cavities and solenoid magnets for transport. Descriptions of the RTA injector and the planned beamline are presented, followed by theoretical studies of the beam transport and dipole mode growth.

We present an update on our ongoing effort to establish a dedicated observation program with an automated 0.6 meter telescope system that can detect GRB optical signals from 30 s to many hours after the start of the burst. The Super-LOTIS telescope has a 0.8 x 0.8{sup o} field-of-view, is sensitive to V 17 {approx} 19 objects, depending on the integration times, and will be placed at the Kitt Peak National Observatory. This paper presents technical aspects of this telescope and first results from initial operations at LLNL. Utilizing real-time coordinates from BATSE, BeppoSAX, XTE, IPN, HETE-2 and INTEGRAL, our LOTIS and SLOTIS systems will measure prompt GRB optical light curves that will enhance our understanding of GRBs.

Using an induction linac, ETA-II, we are studying the interaction of a 2 kA, 6 MeV electron beam focused to a &lt;2 mm diameter spot on high-Z foils. A focus shift was noticed when changing from 5 mil to 40 mil tantalum foil targets. This shift was subsequently attributed to the effect of a substantial fraction of the incident electron beam backscattering from the target, reducing the net beam current. This fraction varies with the thickness and density of the target. The presence and magnitude of the backscattered component was confirmed using Faraday cup collectors and beam current monitors. Calculations confirm the magnitude of the focus shift is consistent with the observed backscattered fraction.

This paper addresses the need to support a very precise optical instrument while causing essentially no influence to its natural shape. Such influences could come from a number of sources, such as manufacturing tolerances, temperature changes, over-constrained structural members, or ground motion. Kinematic couplings have long been used for purposes of repeatable location and minimal influence to the supported object, however these couplings typically offer very little damping. This paper presents a kinematic coupling that utilizes constrained-layer damping techniques to damp out the first three modes of vibration of a precision optical instrument. Finite element analysis was used to aid in the design and tuning of the dampers for the kinematic coupling. Experimental tests were conducted and confirmed the effectiveness of the dampers. The quality factor (Q), which measure the amplification at resonance, dropped from 33.3 to 5.9 on the first mode, from 156.3 to 7.1 on the second mode, and from 147.1 to 18.5 on the third mode. These dampers help to ensure that the stringent vibration requirements necessary to produce high quality optical images are met.

A phenomenological model is proposed to correlate the onset of solid-state amorphization with the loss of interfacial stability in Ni-Ti multilayers. Additionally, a temperature dependence to the onset of amorphization is attributed to the effect of interfacial coherency that varies with the Ni-Ti layer pair spacing.

Here we present designs for a static septum magnet with two adjacent apertures where ideally one aperture has a uniform dipole field and the other zero field. Two designs are considered. One is a true septum magnet with a thin layer of coils and materials separating the dipole field region from the null field region. During the beam switching process, the intense electron beam will spray across this material septum leading to concerns on beam control, vacuum quality, radiation damage, etc. due to the lost particles. Therefore, another configuration without a material septum is also considered. With this configuration it is more difficult to achieve high field quality near the transition region. Shaped shims are designed to limit the degradation of beam quality (emittance growth). Simulations are performed to obtain the magnetic field profile in both designs. A PIC simulation is used to transport a beam slice consisting of several thousand particles through the magnet to estimate emittance growth in the magnet due to the field non-uniformity.

A better understanding of thermal cook-off is important for safe handling and storing explosive devices. A number of safety issues exist about what occurs when a cased explosive thermally cooks off. For example, violence of the events as a function of confinement are important for predictions of collateral damage. This paper demonstrates how adjacent materials can be gauged to measure the resulting pressure wave and how this wave propagates in this adjacent material. The output pulse from the thermal cook-off explosive containing fixture is of obvious interest for assessing many scenarios.

The direct electrochemical conversion of carbon involves discharge of suspensions of reactive carbon particles in a molten salt electrolyte against an oxygen (air) cathode. (Figure 1). The free energy and the enthalpy of the oxidation reaction are nearly identical. This allows theoretical efficiencies ({Delta}G(T)/{Delta}H) to approach 100% at temperatures from 500 to 800 C. Entropy heat losses are therefore negligible. The activities of the elemental carbon and of the carbon dioxide product are uniform throughout the fuel cell and constant over discharge time. This stabilizes cell EMF and allows full utilization of the carbon fuel in a single pass. Finally, the energy cost for pyrolysis of hydrocarbons is generally very low compared with that of steam reforming or water gas reactions. Direct electrochemical conversion of carbon might be compared with molten carbonate fuel cell using carbon rather than hydrogen. However, there are important differences. There is no hydrogen involved (except from trace water contamination). The mixture of molten carbonate and carbon is not highly flammable. The carbon is introduced in as a particulate, rather than as a high volume flow of hydrogen. At the relatively low rates of discharge (about 1 kA/m{sup 2}), the stoichiometric requirements for carbon dioxide by …

Article on the solubility of anthracene in ternary 1,4-dioxane + alcohol + heptane solvent mixtures at 298.15 K.

Nonlinear magneto-optical rotation (NMOR) is investigated at highlight powers where the rotation is significantly modified by AC Stark shifts. These shifts are shown to change the overall sign of rotation for closed F-->F+1 transitions as light power is increased. The effect is demonstrated by measurements in rubidium and density matrix calculations. The results are important for applications of nonlinear optical rotation such as sensitive magnetometry.

The authors compare the results of a microscopic laser theory with gain and recombination currents obtained from experimental spontaneous emission spectra. The calculated absorption spectrum is first matched to that measured on a laser, ensuring that the quasi-Fermi levels for the calculation and the experiment (spontaneous emission and gain) are directly related. This allows one to determine the inhomogeneous broadening in their experimental samples. The only other inputs to the theory are literature values of the bulk material parameter. The authors then estimate the non-radiative recombination current associated with the well and wave-guide core from a comparison of measured and calculated recombination currents.

Sandia National Laboratories (SNL) is leading an effort to evaluate vertical high pressure Bridgman (VHPB) Cd{sub 1-x}Zn{sub x}Te (CZT) crystals grown in the former Soviet Union (FSU) (Ukraine and Russia), in order to study the parameters limiting the crystal quality and the radiation detector performance. The stoichiometry of the CZT crystals, with 0.04 &lt; x &lt; 0.25, has been determined by methods such as proton-induced X-ray emission (PIXE), X-ray diffraction (XRD), microprobe analysis and laser ablation ICP mass spectroscopy (LA-ICP/MS). Other methods such as triaxial double crystal x-ray diffraction (TADXRD), infrared transmission spectroscopy (IR), atomic force microscopy (AFM), thermoelectric emission spectroscopy (TEES) and laser induced transient charge technique (TCT) were also used to evaluate the material properties. The authors have measured the zinc distribution in a CZT ingot along the axial direction and also its homogeneity. The (Cd+Zn)/Te average ratio measured on the Ukraine crystals was 1.2, compared to the ratio of 0.9-1.06 on the Russian ingots. The IR transmission showed highly decorated grain boundaries with precipitates and hollow bubbles. Microprobe elemental analysis and LA-ICP/MS showed carbon precipitates in the CZT bulk and carbon deposits along grain boundaries. The higher concentration of impurities and the imperfect crystallinity lead to shorter …

The authors review how a classification into representations of color and flavor can be used to understand the possible patterns of symmetry breaking for color superconductivity in dense quark matter. In particular, the authors show how for three flavors, color-flavor locking is precisely analogous to the usual pattern of chiral symmetry breaking in the QCD vacuum.

A drift-diffusion transport model has been used to examine the performance capabilities of AlGaN/GaN Npn heterojunction bipolar transistors (HBTs). The Gummel plot from the first GaN-based HBT structure recently demonstrated is adjusted with simulation by using experimental mobility and lifetime reported in the literature. Numerical results have been explored to study the effect of the p-type Mg doping and its incomplete ionization in the base. The high base resistance induced by the deep acceptor level is found to be the cause of limiting current gain values. Increasing the operating temperature of the device activates more carriers in the base. An improvement of the simulated current gain by a factor of 2 to 4 between 25 and 300 C agrees well with the reported experimental results. A preliminary analysis of high frequency characteristics indicates substantial progress of predicted rf performances by operating the device at higher temperature due to a reduced extrinsic base resistivity.