In this paper we report on large scale multi-physics simulation of beam dynamics in electron linacs for next generation free electron lasers (FELs). We describe key features of a parallel macroparticle simulation code including three-dimensional (3D) space-charge effects, short-range structure wake fields, longitudinal coherent synchrotron radiation (CSR) wake fields, and treatment of radiofrequency (RF) accelerating cavities using maps obtained from axial field profiles. A macroparticle up-sampling scheme is described that reduces the shot noise from an initial distribution with a smaller number of macroparticles while maintaining the global properties of the original distribution. We present a study of the microbunching instability which is a critical issue for future FELs due to its impact on beam quality at the end of the linac. Using parameters of a planned FEL linac at Lawrence Berkeley National Laboratory (LBNL), we show that a large number of macroparticles (beyond 100 million) is needed to control numerical shot noise that drives the microbunching instability. We also explore the effect of the longitudinal grid on simulation results. We show that acceptable results are obtained with around 2048 longitudinal grid points, and we discuss this in view of the spectral growth rate predicted from linear theory. As an …

Biogeochemical cycling of zinc is strongly influenced by sorption on birnessite minerals (layer-type MnO2), which are found in diverse terrestrial and aquatic environments. Zinc has been observed to form both tetrahedral (Zn{sup IV}) and octahedral (Zn{sup VI}) triple-corner-sharing surface complexes (TCS) at Mn(IV) vacancy sites in hexagonal birnessite. The octahedral complex is expected to be similar to that of Zn in the Mn oxide mineral, chalcophanite (ZnMn{sub 3}O{sub 7} {center_dot} 3H{sub 2}O), but the reason for the occurrence of the four-coordinate Zn surface species remains unclear. We address this issue computationally using spin-polarized Density Functional Theory (DFT) to examine the Zn{sub IV}-TCS and Zn{sup VI}-TCS species. Structural parameters obtained by DFT geometry optimization were in excellent agreement with available experimental data on Zn-birnessites. Total energy, magnetic moments, and electron-overlap populations obtained by DFT for isolated Zn{sup IV}-TCS revealed that this species is stable in birnessite without a need for Mn(III) substitution in the octahedral sheet and that it is more effective in reducing undersaturation of surface O at a Mn vacancy than is Zn{sub VI}-TCS. Comparison between geometry-optimized ZnMn{sub 3}O{sub 7} {center_dot} 3H{sub 2}O (chalcophanite) and the hypothetical monohydrate mineral, ZnMn{sub 3}O{sub 7} {center_dot} H{sub 2}O, which contains only tetrahedral …

High Level Waste (HLW) at the Savannah River Site (SRS) is stored in three forms: sludge, saltcake, and supernate. A small column ion-exchange (SCIX) process is being designed to treat dissolved saltcake waste before feeding it to the saltstone facility to be made into grout. The waste is caustic with high concentrations of various sodium salts and lower concentrations of radionuclides. Two cation exchange media being considered are a granular form of crystalline silicotitanate (CST) and a spherical form of resorcinol-formaldehyde (RF) resin. CST is an inorganic material highly selective for cesium that is not elutable. Through this process, radioactive cesium from the salt solution is absorbed into ion exchange media (either CST or RF) which is packed within a flow-through column. A packed column loaded with radioactive cesium generates significant heat from radiolytic decay. If engineering designs cannot handle this thermal load, hot spots may develop locally which could degrade the performance of the ion-exchange media. Performance degradation with regard to cesium removal has been observed between 50 and 80 C for CST [1] and at 65 C for RF resin [2]. In addition, the waste supernate solution will boil around 130 C. If the columns boiled dry, the …

An attempt to confirm the reported direct one-proton and two-proton decays of the (21+) isomer at 6.7(5) MeV in 94Ag has been made. The 0.39(4) s half-life of the isomer permitted use of a helium-jet system to transport reaction products from the 40Ca + natNi reaction at 197 MeV to a low-background area; 24 gas Delta E-(Si) E detector telescopes were used to identify emitted protons down to 0.4 MeV. No evidence was obtained for two-proton radioactivity with a summed energy of 1.9(1) MeV and a branching ratio of 0.5(3)percent. Two groups of one-proton radioactivity from this isomer had also been reported; our data confirm the lower energy group at 0.79(3) MeV with its branching ratio of 1.9(5)percent.

This paper shows work at Lawrence Livermore National Lab (LLNL) devoted to modeling the propagation of, and heating by, a relativistic electron beam in a idealized dense fuel assembly for fast ignition. The implicit particle-in-cell (PIC) code LSP is used. Experiments planned on the National Ignition Facility (NIF) in the next few years using the Advanced Radiography Capability (ARC) short-pulse laser motivate this work. We demonstrate significant improvement in the heating of dense fuel due to magnetic forces, increased beam collimation, and insertion of a finite-radius carbon region between the beam excitation and fuel regions.

The effect of pressure on the crystal structure of white phosphorus has been studied up to 22.4 GPa. The {alpha} phase was found to transform into the {alpha}' phase at 0.87 {+-} 0.04 GPa with a volume change of 0.1 {+-} 0.3 cc/mol. A fit of a second order Birch-Murghanan equation to the data gave Vo = 16.94 {+-} 0.08 cc/mol and K{sub o} = 6.7 {+-} 0.5 GPa for the {alpha} phase and Vo = 16.4 {+-} 0.1 cc/mol and K{sub o} = 9.1 {+-} 0.3 GPa for the {alpha}' phase. The {alpha}' phase was found to transform to the A17 phase of black phosphorus at 2.68 {+-} 0.34 GPa and then with increasing pressure to the A7 and then simple cubic phase of black phosphorus. A fit of a second order Birch-Murnaghan equation to our orthorhombic and rhombohedral black phosphorus data gave Vo = 11.43 {+-} 0.02 cc/mol and K{sub o} = 34.7 {+-} 0.5 GPa for the A17 phase and Vo = 9.62 {+-} 0.01 cc/mol and K{sub o} = 65.0 {+-} 0.6 GPa for the A7 phase.

The first stars, forming at redshifts z > 15 in minihalos with M {approx} 10{sup 5-6} M{sub {circle_dot}} may leave behind remnant black holes, which could conceivably have been the 'seeds' for the supermassive black holes observed at z {approx}< 7. We study remnant black hole growth through accretion, including for the first time the radiation emitted due to accretion, with adaptive mesh refinement cosmological radiation-hydrodynamical simulations. The effects of photo-ionization and heating dramatically affect the large-scale inflow, resulting in negligible mass growth. We compare cases with accretion luminosity included and neglected to show that accretion radiation drastically changes the environment within 100 pc of the black hole, increasing gas temperatures by an order of magnitude. Gas densities are reduced and further star formation in the same minihalo is prevented for the two hundred million years we followed. Without radiative feedback included most seed black holes do not gain mass as efficiently as has been hoped for in previous theories, implying that black hole remnants of Pop III stars in minihalos are not likely to be miniquasars. Most importantly, however, our calculations demonstrate that if these black holes are indeed accreting close to the Bondi-Hoyle rate with ten percent radiative …

National Security Technologies’ X-ray Laboratory is comprised of a multi-anode Manson type source and a Henke type source that incorporates a dual goniometer and XYZ translation stage. The first goniometer is used to isolate a particular spectral band. The Manson operates up to 10 kV and the Henke up to 20 kV. The Henke rotation stages and translation stages are automated. Procedures have been developed to characterize and calibrate various NIF diagnostics and their components. The diagnostics include X-ray cameras, gated imagers, streak cameras, and other X-ray imaging systems. Components that have been analyzed include filters, filter arrays, grazing incidence mirrors, and various crystals, both flat and curved. Recent efforts on the Henke system are aimed at characterizing and calibrating imaging crystals and curved crystals used as the major component of an X-ray spectrometer. The presentation will concentrate on these results. The work has been done at energies ranging from 3 keV to 16 keV. The major goal was to evaluate the performance quality of the crystal for its intended application. For the imaging crystals we measured the laser beam reflection offset from the X-ray beam and the reflectivity curves. For the curved spectrometer crystal, which was a natural crystal, …

Complexation of U(VI) with N,N,N{prime},N{prime}-tetramethyl-3-oxa-glutaramide (TMOGA) and N,N-dimethyl-3-oxa-glutaramic acid (DMOGA) was studied in comparison with their dicarboxylate analog, oxydiacetic acid (ODA). Thermodynamic parameters, including stability constants, enthalpy and entropy of complexation, were determined by spectrophotometry, potentiometry and calorimetry. Single-crystal X-ray diffractometry, EXAFS spectroscopy, FT-IR absorption and laser-induced luminescence spectroscopy were used to obtain structural information on the U(VI) complexes. Like ODA, TMOGA and DMOGA form tridentate U(VI) complexes, with three oxygen atoms (the amide, ether and/or carboxylate oxygen) coordinating to the linear UO{sub 2}{sup 2+} cation via the equatorial plane. The stability constants, enthalpy and entropy of complexation all decrease in the order ODA > DMOGA > TMOGA, showing that the complexation is entropy driven and the substitution of a carboxylate group with an amide group reduces the strength of complexation with U(VI) due to the decrease in the entropy of complexation. The trend in the thermodynamic stability of the complexes correlates very well with the structural and spectroscopic data obtained by single crystal XRD, FT-IR and laser-induced luminescence spectroscopy.

The H1700 Package is based on the DOE-EM Certified 9977 Packaging. The H1700 will be certified by the Packaging Certification Division of the National Nuclear Security Administration for the shipment of plutonium by air by the United Stated Military both within the United States and internationally. The H1700 is designed to ship radioactive contents in assemblies of Radioisotope Thermoelectric Generators (RTGs) or arrangements of nested food-pack cans. The RTG containers are designed and tested to remain leaktight during transport, handling, and storage; however, their ability to remain leaktight during transport in the H1700 is not credited. This paper discusses the design and special operation of the H1700.

National Security Technologies’ High Energy X-ray (HEX) Facility is unique in the U.S. Department of Energy complex. The HEX provides fluorescent X-rays of 5 keV to 100 keV with fluence of 10^5–10^6 photons/cm^2/second at the desired line energy. Low energy lines can be filtered, and both filters and fluorescers can be changed rapidly. We present results of calibrating image plates (sensitivity and modulation transfer function), a Bremsstrahlung spectrometer (stacked filters and image plates), and the National Ignition Facility’s Filter- Fluorescer Experiment (FFLEX) high energy X-ray spectrometer. We also show results of a scintillator light yield and alignment study for a neutron imaging system.

Bang time and reaction history measurements are fundamental components of diagnosing ICF implosions and will be essential contributors to diagnosing attempts at ignition on the National Ignition Facility (NIF). Fusion gammas provide a direct measure of fusion interaction rate without being compromised by Doppler spreading. Gamma-based gas Cherenkov detectors that convert fusion gamma rays to optical Cherenkov photons for collection by fast recording systems have been developed and fielded at Omega. These systems have established their usefulness in illuminating ICF physics in several experimental campaigns. Bang time precision better than 25 ps has been demonstrated, well below the 50 ps accuracy requirement defined by the NIF System Design Requirements. A staged approach of implementing Gamma Reaction History (GRH) diagnostics on the NIF has been initiated. In the early stage, multiple detectors located close to target chamber center (at 2 and 6 m) and coupled to photomultiplier tubes are geared toward the loweryield THD campaign. In the later stage, streak camera–coupled instruments will be used for improved temporal resolution at the higher yields expected from the DT ignition campaign. Multiple detectors will allow for increased dynamic range and gamma energy spectral information.

We study the impedance due to coherent synchrotron radiation (CSR) generated by a short bunch of charged particles passing through a dipole magnet of finite length in a vacuum chamber of a given cross section. Our method represents a further development of the previous studies: we decompose the electromagnetic field of the beam over the eigenmodes of the toroidal chamber and derive a system of equations for the expansion coefficients in the series. We illustrate our general method by calculating the CSR impedance of a beam moving in a toroidal vacuum chamber of rectangular cross section.

We have investigated a coupled motion of two vortex cores in ferromagnetic/nonmagnetic/ferromagnetic trilayer cynliders by means of micromagnetic simulation. Dynamic motion of two vortex with parallel and antiparallel relative chiralities of curling spins around the vortex cores have been examined after excitation by 1-ns pulsed external field. With systematic variation in non-magnetic spacer layer thickness from 0 to 20 nm, the coupling between two cores becomes significant as the spacer becomes thinner. Significant coupling leads to a nonlinear chaotic coupled motion of two vortex cores for the parallel chiralities and a faster coupled gyrotropic oscillation for the antiparallel chiralities.

Within the pC{sub H} range of 2.5 to 4.2, gluconate forms three uranyl complexes UO{sub 2}(GH{sub 4}){sup +}, UO{sub 2}(GH{sub 3})(aq), and UO{sub 2}(GH{sub 3})(GH{sub 4}){sup -}, through the following reactions: (1) UO{sub 2}{sup 2+} + GH{sub 4}{sup -} = UO{sub 2}(GH{sub 4}){sup +}, (2) UO{sub 2}{sup 2+} + GH{sub 4}{sup -} = UO{sub 2}(GH{sub 3})(aq) + H{sup +}, and (3) UO{sub 2}{sup 2+} + 2GH{sub 4}{sup -} = UO{sub 2}(GH{sub 3})(GH{sub 4}){sup -} + H{sup +}. Complexes were inferred from potentiometric, calorimetric, NMR, and EXAFS studies. Correspondingly, the stability constants and enthalpies were determined to be log {Beta}{sub 1} = 2.2 {+-} 0.3 and {Delta}H{sub 1} = 7.5 {+-} 1.3 kJ mol{sup -1} for reaction (1), log {Beta}{sub 2} = -(0.38 {+-} 0.05) and {Delta}H{sub 2} = 15.4 {+-} 0.3 kJ mol{sup -1} for reaction (2), and log {Beta}{sub 3} = 1.3 {+-} 0.2 and {Delta}H{sub 3} = 14.6 {+-} 0.3 kJ mol{sup -1} for reaction (3), at I = 1.0 M NaClO{sub 4} and t = 25 C. The UO{sub 2}(GH{sub 4}){sup +} complex forms through the bidentate carboxylate binding to U(VI). In the UO{sub 2}(GH{sub 3})(aq) complex, hydroxyl-deprotonated gluconate (GH{sub 3}{sup 2-}) coordinates to U(VI) through the …

We developed a new approach to separate bacteria from human blood cells based on soft inertial force induced migration with flow defined curved and focused sample flow inside a microfluidic device. This approach relies on a combination of an asymmetrical sheath flow and proper channel geometry to generate a soft inertial force on the sample fluid in the curved and focused sample flow segment to deflect larger particles away while the smaller ones are kept on or near the original flow streamline. The curved and focused sample flow and inertial effect were visualized and verified using a fluorescent dye primed in the device. First the particle behavior was studied in detail using 9.9 and 1.0 {micro}m particles with a polymer-based prototype. The prototype device is compact with an active size of 3 mm{sup 2}. The soft inertial effect and deflection distance were proportional to the fluid Reynolds number (Re) and particle Reynolds number (Re{sub p}), respectively. We successfully demonstrated separation of bacteria (Escherichia coli) from human red blood cells at high cell concentrations (above 10{sup 8}/mL), using a sample flow rate of up to 18 {micro}L/min. This resulted in at least a 300-fold enrichment of bacteria at a wide range …

We review recent progress in the following areas of the impedance theory: calculation of impedance of tapers and small angle collimators; optical approximation and parabolic equation for the high-frequency impedance; impedance due to resistive inserts in a perfectly conducting pipe.

We describe a funnel cone for concentrating an ion beam on a target. The cone utilizes the reflection characteristic of ion beams on solid walls to focus the incident beam andincrease beam intensity on target. The cone has been modeled with the TRIM code. A prototype has been tested and installed for use in the 350-keV K+ NDCX target chamber.

We report transient hole-burning and saturation recovery measurements in the CN radical with MHz frequency resolution and 20 ns time resolution. Narrow velocity groups of individual hyperfine levels of selected rotational states in CN (X{sup 2} {Sigma}{sup +}) are depleted and excited (A{sup 2}{pi}{sub i}) with a saturation laser and probed by a counterpropagating, frequency modulated probe beam. Recent work in our lab has used this method to measure and characterize the hyperfine splittings for a set of rotational, fine structure, and parity components of CN (A{sup 2}{pi}{sub i}, v=1). Extending this work, we report time and frequency dependence of the saturation signals following abrupt switching of the CW saturation beam on and off with an electro-optic amplitude modulator. Recovery of the unsaturated absorption following the turnoff of the saturation beam follows pressure-dependent kinetics, driven by collisions with the undissociated NCCN precursor with a rate coefficient of 2 x 10{sup -9} cm{sup 3} s{sup -1} molec{sup -1}. Similar recovery kinetics are observed for two-level saturation resonances, where the signal observed is a combination of X- and A-state kinetics, as well as for three-level crossover resonances, which can be chosen to probe selectively the holefilling in the X state or the …

This paper discusses the use of nuclear resonance fluorescence (NRF) techniques for the isotopic and quantitative assaying of radioactive material. Potential applications include age-dating of an unknown radioactive source, pre- and post-detonation nuclear forensics, and safeguards for nuclear fuel cycles Examples of age-dating a strong radioactive source and assaying a spent fuel pin are discussed. The modeling work has ben performed with the Monte Carlo radiation transport computer code MCNPX, and the capability to simulate NRF has bee added to the code. Discussed are the limitations in MCNPX's photon transport physics for accurately describing photon scattering processes that are important contributions to the background and impact the applicability of the NRF assay technique.

An analysis is presented to show how it is possible for unconsolidated granular packings to obey overall non-Hertzian pressure dependence due to the imperfect and random spatial arrangements of the grains in these packs. With imperfect arrangement, some gaps that remain between grains can be closed by strains applied to the grain packing. As these gaps are closed, former rattler grains become jammed and new stress-bearing contacts are created that increase the elastic stiffness of the packing. By allowing for such a mechanism, detailed analytical expressions are obtained for increases in bulk modulus of a random packing of grains with increasing stress and strain. Only isotropic stress and strain are considered in this analysis. The model is shown to give a favorable fit to laboratory data on variations in bulk modulus due to variations in applied pressure for bead packs.

We have successfully built and operated a source deployment system for the KamLAND detector. This system was used to position radioactive sources throughout the delicate 1-kton liquid scintillator volume, while meeting stringent material cleanliness, material compatibility, and safety requirements. The calibration data obtained with this device were used to fully characterize detector position and energy reconstruction biases. As a result, the uncertainty in the size of the detector fiducial volume was reduced by a factor of two. Prior to calibration with this system, the fiducial volume was the largest source of systematic uncertainty in measuring the number of antineutrinos detected by KamLAND. This paper describes the design, operation and performance of this unique calibration system.

Gas Cherenkov detectors have been used to convert fusion gammas into photons to achieve gamma reaction history (GRH) measurements. These gas detectors include a converter, pressurized gas volume, relay optics, and a photon detector. A novel design for the National Ignition Facility (NIF) using 90º Off-Axis Parabolic mirrors efficiently collects signal from fusion gammas with 8-ps time dispersion.1 Fusion gammas are converted to Compton electrons, which generate broadband Cherenkov light (our response is from 250 to 700 nm) in a pressurized gas cell. This light is relayed into a high-speed detector using three parabolic mirrors. The detector optics collect light from a 125-mm-diameter by 600-mm-long interchangeable gas (CO2 or SF6) volume. Because light is collected from source locations throughout the gas volume, the detector is positioned at the stop position rather than at an image position. The stop diameter and its position are independent of the light-generation locations along the gas cell. This design incorporates a fixed time delay that allows the detector to recover from prompt radiation. Optical ray tracings demonstrate how light can be collected from different angled trajectories of the Compton electrons as they traverse the gas volume. A Monte Carlo model of the conversion process from …

The conclusions are: (1) LDA predicts fairly well the structures of {pi}-dimers. This has been reported before. Here we show that even the small difference between conformers can be described by LDA. Electron densities suggest a stronger bond is formed in LDA than B3LYP. (2) Though its good performance is possibly due to error cancelations, LDA may be used as a practical tool for large {pi}-dimer systems. (3) TDDFT once again does a good job for the optical transitions. The near-IR band shows a weak dependence on the functional, but a stronger one on the interplanar distance.