In rough agreement with experimental values derived from Cu island shapes vs. temperature, ab-initio calculations yield formation energies of 0.27 and 0.26 eV/ step-edge-atom for (100)- and (111)-micro facet steps on Cu(lll), and 0.09 and 0.12 eV per kink in those steps. Comparison to ab-initio results for Al and Pt shows that as a rule, the average formation energy of straight steps on a close-packed metal surface equals -7% of the metal's cohesive energy.

Previous X-ray Diffraction (XRD) and Nuclear Magnetic Resonance (NMR) studies on Ti-doped NaAlH{sub 4} revealed the reaction products of two heavily doped (33.3 at.%) samples that were solvent-mixed and mechanically-milled. This investigation revealed that nano-crystalline or amorphous Al{sub 2}O{sub 3} forms from the possible coordination of aluminum with oxygen atom of the furan ring system from added tetrahydrofuran (THF) in the solvent-mixed sample, and that TiAl{sub 3} forms in mechanically-milled samples. The present paper provides a more sophisticated NMR investigation of the these materials. On heavily doped (33.3 at.%) solvent-mixed samples, {sup 27}Al Magic Angle Spinning (MAS) NMR {sup 27}Al multiple quantum MAS (MQMAS) indicates the presence of an oxide layer of Al{sub 2}O{sub 3} on the surfaces of potentially bulk nanocrystalline Ti, nanocrystalline TiAl{sub 3}, and/or metallic aluminum. The {sup 1}H MAS NMR data also indicate the possible coordination of aluminum with the oxygen atom in the THF. On heavily doped samples that were mechanically milled, {sup 27}Al MAS NMR and static NMR confirms the presence of TiAl{sub 3}. In addition, the {sup 1}H MAS NMR and {sup 1}H spin-lattice relaxation (T{sub 1}) measurements are consistent with the presence of TiH{sub 2}. These results are in agreement with recent …

In this paper, we present an 800 MHz crab cavity conceptual design for the LHC upgrade. The cell shape is optimized for lower maximum peak surface fields as well as higher transverse R/Q. A compact coax-to-coax coupler scheme is proposed to damp the LOM/SOM modes. A two-stub antenna with a notch filter is used as the HOM coupler to damp the HOM modes in the horizontal plane and rejects the operating mode at 800MHz. Multipacting (MP) simulations show that there are strong MP particles at the disks. Adding grooves along the short axis without changing the operating mode's RF characteristics can suppress the MP activities. Possible input coupler configurations are discussed.

he superconducting gap--an energy scale tied to the superconducting phenomena--opens on the Fermi surface at the superconducting transition temperature (Tc) in conventional BCS superconductors. In underdoped high-Tc superconducting copper oxides, a pseudogap (whose relation to the superconducting gap remains a mystery) develops well above Tc (refs 1, 2). Whether the pseudogap is a distinct phenomenon or the incoherent continuation of the superconducting gap above Tc is one of the central questions in high-Tc research3, 4, 5, 6, 7, 8. Although some experimental evidence suggests that the two gaps are distinct9, 10, 11, 12, 13, 14, 15, 16, 17, 18, this issue is still under intense debate. A crucial piece of evidence to firmly establish this two-gap picture is still missing: a direct and unambiguous observation of a single-particle gap tied to the superconducting transition as function of temperature. Here we report the discovery of such an energy gap in underdoped Bi2Sr2CaCu2O8+delta in the momentum space region overlooked in previous measurements. Near the diagonal of Cu?O bond direction (nodal direction), we found a gap that opens at Tc and has a canonical (BCS-like) temperature dependence accompanied by the appearance of the so-called Bogoliubov quasi-particles, a classical signature of superconductivity. This is …

We examine sub-structuring methods for solving large-scalegeneralized eigenvalue problems from a purely algebraic point of view. Weuse the term "algebraic sub-structuring" to refer to the process ofapplying matrix reordering and partitioning algorithms to divide a largesparse matrix into smaller submatrices from which a subset of spectralcomponents are extracted and combined to provide approximate solutions tothe original problem. We are interested in the question of which spectralcomponentsone should extract from each sub-structure in order to producean approximate solution to the original problem with a desired level ofaccuracy. Error estimate for the approximation to the small esteigen pairis developed. The estimate leads to a simple heuristic for choosingspectral components (modes) from each sub-structure. The effectiveness ofsuch a heuristic is demonstrated with numerical examples. We show thatalgebraic sub-structuring can be effectively used to solve a generalizedeigenvalue problem arising from the simulation of an acceleratorstructure. One interesting characteristic of this application is that thestiffness matrix produced by a hierarchical vector finite elements schemecontains a null space of large dimension. We present an efficient schemeto deflate this null space in the algebraic sub-structuringprocess.

Based on prior work at the Lawrence Livermore National Laboratory ambient-temperature passive magnetic bearings are being adapted for use in high-power flywheel energy storage systems developed at the Trinity Flywheel Power company. En route to this goal specialized test stands have been built and computer codes have been written to aid in the development of the component parts of these bearing systems. The Livermore passive magnetic bearing system involves three types of elements, as follows: (1) Axially symmetric levitation elements, energized by permanent magnets., (2) electrodynamic ''stabilizers'' employing axially symmetric arrays of permanent magnet bars (''Halbach arrays'') on the rotating system, interacting with specially wound electrically shorted stator circuits, and, (3) eddy-current-type vibration dampers, employing axially symmetric rotating pole assemblies interacting with stationary metallic discs. The theory of the Livermore passive magnetic bearing concept describes specific quantitative stability criteria. The satisfaction of these criteria will insure that, when rotating above a low critical speed, a bearing system made up of the three elements described above will be dynamically stable. That is, it will not only be stable for small displacements from equilibrium (''Earnshaw-stable''), but will also be stable against whirl-type instabilities of the types that can arise from displacement-dependent drag …

Most single-crystal shock experiments have been performed in high-symmetry directions while the nature of shock propagation in low-symmetry directions remains relatively unstudied. It is well known that small-amplitude, linear acoustic waves propagating in low-symmetry directions can focus and/or form caustics (Wolfe, 1995). In this report we provide evidence for similar focusing behavior in nonlinear (shock) waves propagating in single crystals of silicon and diamond. Using intense lasers, we have driven non-planar (divergent geometry) shock waves through single-crystals of silicon or diamond and into an isotropic backing plate. On recovery of the backing plates we observe a depression showing evidence of anisotropic plastic strain with well-defined crystallographic registration. We observe 4-, 2-, and 3-fold symmetric impressions for [100], [110], and [111] oriented crystals respectively.

Gribov viewed the axial anomaly as a manifestation of the collective motion of Dirac fermions with arbitrarily high momenta in the vacuum. In the presence of an external magnetic field and a chirality imbalance, this collective motion becomes directly observable in the form of the electric current - this is the chiral magnetic effect (CME). I give an elementary introduction into the physics of CME, and discuss the experimental status and recent developments.

The need for normal incidence mirrors maintaining reflectivity greater than 60% for an industrially competitive Extreme Ultraviolet Lithography (EUV) system has been well documented. The Molybdenum/Silicon system has emerged as the de-facto standard, where researchers are now routinely fabricating mirrors demonstrating 63% reflectivity near 130 Angstroms. However, multilayer mirrors using beryllium as the low atomic number (low-Z) spacer could potentially show similar or better reflectivity, and operate at wavelengths down to the beryllium K-edge at 111 Angstroms. Besides offering potentially greater reflectivity, the shorter wavelength light offers increased dissolution depth in photoresists, and offers potentially better resolution and depth of focus. We will report our latest results from beryllium based multilayers. The mirrors were fabricated at the Lawrence Livermore National Laboratory (LLNL) and tested at the Center for X-Ray Optics at Lawrence Berkeley Laboratory (CXRO/LBL).

Quantitative estimates of charge exchange (CE) losses during acceleration are very important in the design and operation of heavy ion cyclotrons. Such estimates have been made using a vacuum model computer code which was developed to establish vacuum requirements for the MSU superconducting heavy ion cyclotron. This code uses pressure and cross-section data to calculate the radial loss of beam due to charge exchange. Since CE cross sections and radial pressure profiles are not always well known, certain specific measurements have been made using the LBL 88-Inch Cyclotron to provide experimental data needed to test the code. These include measurements of pressure versus radius under vacuum conditions closely approximating those existing during acceleration of /sup 14/N/sup 4 -/ and /sup 40/Ar/sup 8 -/ beams. Beam intensity versus radius data demonstrating transmission losses for three beams are presented. Comparisons with theoretical predictions are given.

Experiment 791 at Fermilab`s Tagged Photon Laboratory has just accumulated a high statistics charm sample by recording 20 billion events on 24000 8mm tapes. A 500 GeV/c {pi}{sup {minus}} beam was used with a fixed target and a magnetic spectrometer which now includes 23 silicon microstrip planes for vertex reconstruction. A new data acquisition system read out 9000 events/sec during the part of the Tevatron cycle that delivered beam. Digitization and readout took 50 {mu}S per event. Data was buffered in eight large FIFO memories to allow continuous event building and continuous tape writing to a wall of 42 Exabytes at 9.6 MB/sec. The 50 terabytes of data buffered to tape is now being filtered on RISC CPUs. Preliminary results show D{sup 0} {yields} K{sup {minus}}{pi}{sup +} and D{sup +} {yields} K{sup {minus}}{pi}{pi}{sup +} decays. Rarer decays will be pursued.

Experiment 791 at Fermilab's Tagged Photon Laboratory has just accumulated a high statistics charm sample by recording 20 billion events on 24000 8mm tapes. A 500 GeV/c [pi][sup [minus]] beam was used with a fixed target and a magnetic spectrometer which now includes 23 silicon microstrip planes for vertex reconstruction. A new data acquisition system read out 9000 events/sec during the part of the Tevatron cycle that delivered beam. Digitization and readout took 50 [mu]S per event. Data was buffered in eight large FIFO memories to allow continuous event building and continuous tape writing to a wall of 42 Exabytes at 9.6 MB/sec. The 50 terabytes of data buffered to tape is now being filtered on RISC CPUs. Preliminary results show D[sup 0] [yields] K[sup [minus]][pi][sup +] and D[sup +] [yields] K[sup [minus]][pi][pi][sup +] decays. Rarer decays will be pursued.

The rate capabilities of LiFePO{sub 4} composites are dependent on the structure of the carbon that coats the powders, formed during co-calcination with carbon containing precursors. The addition of readily decomposed pyromellitic acid and graphitization catalysts such as ferrocene during synthesis results in coatings with low D/G (disordered/graphene) ratios, while maintaining the carbon content of the powders below 2 wt. %. This is important to avoid adversely affecting the tap density. The good correlation between the pressed pellet conductivities of the LiFePO{sub 4}/C composites and their rate capability in lithium cells is further confirmation of the importance of the carbon structure, because graphitic carbons generally have higher conductivities than disordered ones.

Recently a scheme entitled echo-enabled harmonic generation (EEHG) was proposed for producing short wavelength FEL radiation that allows far higher harmonic numbers to be accessed as compared with the normal limit arising from incoherent energy spread. In this paper we study the feasibility of a single EEHG stage to generate coherent radiation in the 'water window' (2--4 nm wavelength) directly from a UV seed laser at 190-nm wavelength. We present time-dependent simulation results which demonstrate that the single-stage EEHG FEL can generate high power soft x-ray radiation in the water window with narrow bandwidth close to Fourier transform limit directly from a UV seed laser. The schemes to generate short x-ray pulse from femtosecond to attosecond using EEHG FEL are also discussed.

We present recent developments on the single transverse spin physics, in particular, the Collins mechanism contributions in various hadronic reactions, such as semi-inclusive hadron production in DIS process, azimuthal distribution of hadron in high energy jet in pp collisions. We will demonstrate that the transverse momentum dependent and collinear factorization approaches are consistent with each other in the description of the Collins effects in the semi-inclusive hadron production in DIS process.

The long-term success of the Experimental Breeder Reactor-II (EBR-II) provides several insights into fundamental characteristics and design features of a nuclear generating station that enhance safety, operability, and maintainability. Some of these same characteristics, together with other features, offer the potential for operational lifetimes well beyond the current licensing time frame, and improved reliability that could potentially reduce amortized capital costs as well as overall operation and maintenance costs if incorporated into advanced plant designs. These features and characteristics are described and the associated benefits are discussed.

The DARHT II accelerator at LANL is preparing a series of preliminary tests at the reduced voltage of 7.8 MeV. The transport hardware between the end of the accelerator and the final target magnet was shipped to LLNL and installed on ETA II. Using the ETA II beam at 5.2 MeV we completed a set of experiments designed reduce start up time on the DARHT II experiments and run the equipment in a configuration adapted to the reduced energy. Results of the beam transport using a reduced energy beam, including the kicker and kicker pulser system will be presented.

MicroBooNE is a liquid Argon time projection chamber to be built at Fermilab for an accelerator-based neutrino physics experiment and as part of the R&D strategy for a large liquid argon detector at DUSEL. The waveforms of the {approx}9000 sense wires in the chamber are continuously digitized at 2 M samples/s - which results in a large volume of data coming off the TPC. We have developed a lossless data reduction scheme based on Huffman Coding and have tested the scheme on cosmic ray data taken from a small liquid Argon time projection chamber, the BO detector. For sense wire waveforms produced by cosmic ray tracks, the Huffman Coding scheme compresses the data by a factor of approximately 10. The compressed data can be fully recovered back to the original data since the compression is lossless. In addition to accelerator neutrino data, which comes with small duty cycle in sync with the accelerator beam spill, continuous digitized waveforms are to be temporarily stored in the MicroBooNE data-acquisition system for about an hour, long enough for an external alert from possible supernova events. Another scheme, Dynamic Decimation, has been developed to compress further the potential supernova data so that the storage …

We have developed a novel insulator concept that involves the use of alternating layers of conductors and insulators with periods less than 1 mm. We have demonstrated that these structures perform 2 to 5 times better than conventional insulators in long pulse, short pulse, and alternating polarity applications. We present new testing results showing exceptional behavior at DC, with gradients in excess of 110kV/cm in vacuum.

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Determining the printability of substrate defects beneath the extreme ultraviolet (EUV) reflecting multilayer stack is an important issue in EUVL lithography. Several simulation studies have been performed in the past to determine the tolerable defect size on EUV mask blank substrates but the industry still has no exact specification based on real printability tests. Therefore, it is imperative to experimentally determine the printability of small defects on a mask blanks that are caused by substrate defects using direct printing of programmed substrate defect in an EUV exposure tools. SEMATECH fabricated bump type program defect masks using standard electron beam lithography and performed printing tests with the masks using an EUV exposure tool. Defect images were also captured using SEMATECH's Berkeley Actinic Imaging Tool in order to compare aerial defect images with secondary electron microscope images from exposed wafers. In this paper, a comprehensive understanding of substrate defect printability will be presented and printability specifications of EUV mask substrate defects will be discussed.

Successful operation of large-scale high-power lasers, such as those in use and planned at LLNL and elsewhere, require optical elements that can withstand extremely high fluences without suffering damage. Of particular concern are dielectric diffraction gratings used for beam sampling and pulse compression. Laser induced damage to bulk dielectric material originates with coupling of the electric field of the radiation to bound electrons, proceeding through a succession of mechanisms that couple the electron kinetic energy to lattice energy and ultimately to macroscopic structural changes (e.g. melting). The constructive interference that is responsible for the diffractive behavior of a grating or the reflective properties of a multilayer dielectric stack can enhance the electric field above values that would occur in unstructured homogeneous material. Much work has been done to model damage to bulk matter. The presence of nonuniform electric fields, resulting from diffractive coherence, has the potential to affect damage thresholds and requires more elaborate theory. We shall discuss aspects of work directed towards understanding the influence of dielectric structures upon damage, with particular emphasis on computations and interpretation of electric fields within dielectric gratings and multilayer dielectric stacks, noting particularly the interference effects that occur in these structures.

We consider in detail the effects of local mass anomalies in Eoetvoes-like experiments. It is shown that in the presence of an intermediate-range non-gravitational force, the dominant contributions to both the sign and magnitude of the Eoetvoes anomaly may come from nearby masses and not from the earth as a whole. This observation has important implications in the design and interpretation of future experiments, and in the formulation of unified theories incorporating new intermediate-range forces.

Successful operation of large-scale high-power lasers, such as those in use and planned at LLNL and elsewhere, require optical elements that can withstand extremely high fluences without suffering damage. Of particular concern are gratings used for pulse compression. Laser induced damage to bulk dielectric material originates with coupling of the electric field of the radiation to bound electrons, proceeding through a succession of mechanisms that couple the electron kinetic energy to lattice energy and ultimately to macroscopic structural changes (e.g. fracture, melting, ablation, etc.). The constructive interference that is responsible for the diffractive behavior of a grating or the reflective properties of a multilayer dielectric stack can enhance the electric field above values that would occur in unstructured homogeneous material. The presence of nonuniform electric fields, resulting from diffractive coherence, has the potential to affect damage thresholds We describe aspects of LLNL work directed towards understanding the influence of dielectric structures upon damage, with particular emphasis on electric fields within multilayer dielectric stacks.