Arkani-Hamed, Dimopoulos and Dvali have recently proposed that gravity may become strong at energies near 1 TeV thus removing the hierarchy problem. This scenario can be tested in several ways at present and future colliders. In this paper we examine the exchange of towers of Kaluza-Klein gravitons and their influence on the production of pairs of massive gauge bosons in {gamma}{gamma} collisions. These tower exchanges are shown to lead to a new dimension-8 operator that can significant alter the Standard Model expectations for these processes. The role of polarization for both the initial state photons and the final state gauge bosons in improving sensitivity to graviton exchange is emphasized. We find that the discovery reach for graviton tower exchange in the {gamma}{gamma} {r_arrow} W{sup +}W{sup {minus}} channel to be significantly greater than for any other process so far examined.

Although this guide focuses on the retrocommissioning process and its advantages, all three types of commissioning--retrocommissioning, commissioning, and recommissioning--play an equally important role in ensuring that buildings perform efficiently and provide comfortable, safe, and productive work environments for owners and occupants. For new construction and retrofit projects, commissioning should be incorporated early, during design, and last throughout the length of the project. For buildings that were never commissioned, the retrocommissioning process can yield a wealth of cost-saving opportunities while enhancing a building's environment. Finally, once a building is commissioned or retrocommissioned, incorporating recommissioning into the organization's O and M program (by periodically reapplying the original diagnostic testing and checklist procedures) helps ensure that cost savings and other benefits gained from the original process persist over time.

We consider the solution of time-dependent, energy-dependent, discrete ordinates, and nonlinear radiative transfer problems on three-dimensional unstructured spatial grids. We discuss the solution of this class of transport problems, using the code TETON, on large distributed-memory multinode computers having multiple processors per ''node'' (e.g. the IBM-SP). We discuss the use of both spatial decomposition using message passing between ''nodes'' and a threading algorithm in angle on each ''node''. We present timing studies to show how this algorithm scales to hundreds and thousands of processors. We also present an energy group ''batching'' algorithm that greatly enhances cache performance. Our conclusion, after considering cache performance, storage limitations and dependencies inherent in the physics, is that a model that uses a combination of message-passing and threading is superior to one that uses message-passing alone. We present numerical evidence to support our conclusion.

The Next Linear Collider is an electron-positron accelerator unprecedented in its size, energy, and tight tolerances. We describe the suite of simulation tools which are widely used in designing and modeling the performance of the NLC. In order to achieve a uniform beamline description and permit simulation of all facets of the collider, an extended version of the Standard Input Format (xSIF) has been developed and implemented in MAD and DIMAD. We discuss several enhancements to the MAD and DIMAD calculation engines necessary to properly simulate the most challenging regions of the facility. We also describe enhancements to LIAR which allow it to be used as the tracking engine for a tuning/feedback simulation written in MATLAB. Finally, we discuss the additional software needed to model the beam stabilization and tuning processes.

The Overture framework is an object-oriented environment for solving partial differential equations in two and three space dimensions. It is a collection of C++ libraries that enables the use of finite difference and finite volume methods at a level that hides the details of the associated data structures. Overture can be used to solve problems in complicated, moving geometries using the method of overlapping grids. It has support for grid generation, difference operators, boundary conditions, data-base access and graphics. Short sample code segments are presented to show the power of this approach.

In this paper we investigate the microstructural accommodation of nonstoichiometry in (Ba{sub x}Sr{sub 1{minus}x}Ti{sub 1+y}O{sub 3+z}) thin films grown by chemical vapor deposition. Films with three different (Ba+Sr)/Ti ratios of 49/51 (y=0.04 in the notation of the formula above), of 48/52 (y=0.08) and of 46.5/53.5 (y=O.15), were studied. High-resolution electron microscopy is used to study the microstructure of the BST films. High-spatial resolution electron energy-loss spectroscopy (EELS) is used to reveal changes in chemistry and local atomic environment both at grain boundaries and within grains as a function of titanium excess. We find an amorphous phase at the grain boundaries and grain boundary segregation of excess titanium in the samples with y=0.15. In addition, EELS is also used to show that excess titanium is being partially accommodated in the grain interior. Implications for the film electrical and dielectric properties are outlined.

The authors investigate finite pulse effects in self-amplified spontaneous emission (SASE), especially the role of coherent spontaneous emission (CSE) in the start and the evolution of the free-electron laser (FEL) process. When the FEL interaction is negligible, they solve the one-dimensional Maxwell equation exactly and clarify the meaning of the slowly varying envelope approximation (SVEA). In the exponential gain regime, they solve the coupled Vlasov-Maxwell equations and extend the linear theory to a bunched beam with energy spread. A time-dependent, non-linear simulation algorithm is employed to study the CSE effect for a general beam distribution.

Recently, it has been proposed that the fundamental scale of quantum gravity can be close to the weak scale if there are large extra dimensions . This proposal has important phenomenological implications for processes at the TeV scale. We study the process {gamma}{gamma} {r_arrow} {gamma}{gamma}, assuming an ultraviolet cutoff M{sub S} {approximately} 1 TeV for the effective gravity theory. We find that, at center of mass energies {radical}s {approximately} 1 TeV, the contribution of gravitationally mediated scattering to the cross section is comparable to that coming from the one-loop Feynman diagrams of the Standard Model. We thus conclude that the effects of weak scale quantum gravity can be studied at the Next Linear Collider (NLC), in the photon collider mode. Our results suggest that, for typical proposed NLC energies and luminosities, the range 1 TeV {le} M{sub S} {le} 10 TeV can be probed.

Horizontal orbit errors at the sextuples in the Advanced Photon Source (APS) storage ring can cause changes in tune and modulation of the beta functions around the ring. To determine the significance of these effects requires knowing the orbit relative to the magnetic center of the sextuples. The method considered here to determine the horizontal beam position in a given sextupole is to measure the tune shift caused by a change in the sextupole strength. The tune shift and a beta function for the same plane uniquely determine the horizontal beam position in the sextupole. The beta function at the sextupole was determined by propagating the beta functions measured at nearby quadrupoles to the sextupole location. This method was used to measure the sextupole magnetic center offset relative to an adjacent beam position monitor (BPM) at a number of sextupole locations. We report on the successes and problems of the method as well as an improved method.

In this presentation the electron field emission and electrical conductivity of undoped and nitrogen doped DLC films have been investigated. Undoped and nitrogen doped DLC films were grown by PE CVD from CH{sub 4}:H{sub 2} and CH{sub 4}:H{sub 2}:N{sub 2} gas mixtures, correspondingly. During nitrogen doped DLC film deposition, the nitrogen content in the gas mixture was varied within the range 0 to 45%. In-situ gas-phase doping allowed them to deposit DLC films with different content nitrogen. DLC films were deposited under three different levels of gas pressure in the chamber: 0.2, 0.6 and 0.8 Torr. The measurements of emission current from samples were performed in the vacuum system which could be pumped to a stable pressure of 10{sup {minus}6} Torr. The emission current was measured in the diode structure. The emitter-anode spacing L was constant and equal to 20 {micro}m. The current-voltage characteristics of the Si field electron emission arrays covered with undoped and nitrogen doped DLC films show that at the beginning the threshold voltage (V{sub th}) increases remarkably with nitrogen content, then V{sub th} is observed to decrease and finally V{sub th} increases. Corresponding Fowler-Nordheim (F-N) plots follow F-N tunneling over a wide range. The F-N plots …

During electron beam (EB) welding of developmental units, weld blowouts occurred. It is well documented that the presence of moisture causes the weld blowout. The detrimental effects of water vapor on the weld are experimentally proven [l]. The availability of water vapor in the melt increases the onset and severity of blowout and porosity. Because water vapor is insoluble in the molten metal, it will consequently form either bubbles or boil. On the other hand, hydrogen will react with other impurities present in the melt to form insoluble gas bubbles, which most likely will be entrapped in the fusion zone as porosity. This study attempts to answer the question of what is the critical weld blowout pressure, and to compare the experimental results to the estimated pressure values, so that validated calculations could be extended to other weld configurations.

Infrared thermal imaging has become increasingly popular as a nondestructive evaluation method for characterizing materials and detecting defects. One technique, which was utilized in this study, is front-flash thermal imaging. We have developed a thermal imaging system that uses this technique to characterize advanced material systems, including continuous fiber ceramic composite (CFCC) components. In a front-flash test, pulsed heat energy is applied to the surface of a sample, and decay of the surface temperature is then measured by the thermal imaging system. CFCC samples with drilled flat-bottom holes at the back surface (to serve as ''flaws'') were examined. The surface-temperature/time relationship was analyzed to determine the depths of the flaws from the front surface of the CFCC material. Experimental results on carbon/carbon and CFCC samples are presented and discussed.

The performance requirements of the Advanced Photon Source (APS) challenge the control system in a number of areas. This paper will review a few applications of advanced technology in the control and monitoring of the APS. The application of digital signal processors (DSPs) and techniques will be discussed, both from the perspective of a large distributed multiprocessor system and from that of embedded systems. In particular, two embedded applications will be highlighted, a beam position monitor processor and a DSP-based power supply controller. Fast data distribution is often a requirement. The application of a high-speed network based on reflective memory will also be discussed in the context of the APS global orbit feedback system. Timing systems provide opportunities to apply technologies such as high-speed logic and fiber optics. Examples of the use of these technologies will also be included. Finally, every modern accelerator control system of any size requires networking. Features of the APS accelerator controls network will be discussed.

The powder-in-tube (PIT) technique was used to fabricate multifilament (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (Bi-2223) superconducting tapes. Transport current properties of these tapes were enhanced by increasing the packing density of the precursor powder and improving the mechanical deformation condition. A critical current (I{sub c}) of > 35 A in long lengths (> 200 m) tapes has been achieved. In measuring the dependence of critical current density on magnetic field and temperature for the optimally processed tapes, we found a J{sub c} of > 10{sup 4} A/cm{sup 2} at 20 K in magnetic fields up to 3 T and parallel to the c-axis, which is of interest for use in refrigerator-cooled magnets. I{sub c} declined exponentially when an external field was applied perpendicular to the tape surface at 77 K. Mechanical stability was tested for tapes sheathed with pure Ag and Ag-Mg alloy. Tapes made with pure Ag sheathing can withstand a tensile stress of {approx}20 MPa with no detrimental effect on I{sub c} values. Mechanical performance was improved by using Ag-Mg alloy sheathing: values of transport critical current began to decrease at the tensile stress of {approx} 100 MPa. Transport current measurements on tapes wound on a mandrel …

Microstructural analyses by several advanced metallographic techniques were conducted on austenitic stainless steel mockup and core shroud welds that had cracked in boiling water reactors. Contrary to previous beliefs, heat-affected zones of the cracked Type 304L, as well as 304 SS core shroud welds and mockup shielded-metal-arc welds, were free of grain-boundary carbides, which shows that core shroud failure cannot be explained by classical intergranular stress corrosion cracking. Neither martensite nor delta-ferrite films were present on the grain boundaries. However, as a result of exposure to welding fumes, the heat-affected zones of the core shroud welds were significantly contaminated by oxygen and fluorine, which migrate to grain boundaries. Significant oxygen contamination seems to promote fluorine contamination and suppress thermal sensitization. Results of slow-strain-rate tensile tests also indicate that fluorine exacerbates the susceptibility of irradiated steels to intergranular stress corrosion cracking. These observations, combined with previous reports on the strong influence of weld flux, indicate that oxygen and fluorine contamination and fluorine-catalyzed stress corrosion play a major role in cracking of core shroud welds.

We have seen that many different types of intermolecular interactions in organic conducting cation radical salts. Hydrogen bonding between the donor molecules and the anions is weak but not negligible. The ionic Madelung energy is insufficient to completely intersperse anions and cations, thus the layers favored by the van der Waals interactions remain intact. The search for new conducting and superconducting salts has been mainly by trial-and-error methods, even though simple substitutions have been employed in order to obtain isostructural analogs of successful (e.g., superconducting) salts. However, even seemingly minor substitutions sometimes destroy the packing type, and different crystal structures result. Simulations with the aim at predicting crystal structures have not succeeded, mainly because the different interaction types are of comparable energy, and the delocalized and partial charges render the calculations of the ionic terms extremely unreliable. Clearly, the development of suitable crystal modeling techniques with predictive capabilities is one of the great needs of the field.

In this lecture, a limited introduction of gauge invariance in phase-space is provided, predicated on canonical transformations in quantum phase-space. Exact characteristic trajectories are also specified for the time-propagating Wigner phase-space distribution function: they are especially simple--indeed, classical--for the quantized simple harmonic oscillator. This serves as the underpinning of the field theoretic Wigner functional formulation introduced. Scalar field theory is thus reformulated in terms of distributions in field phase-space. This is a pedagogical selection from work published and reported at the Yukawa Institute Workshop ''Gauge Theory and Integrable Models'', 26-29 January, 1999.

The longitudinal microwave instability is present in the SLC damping rings during routine operations. Experimental studies of the instability at nominal conditions have been reported previously. To complement those studies and better understand the properties of the instability a series of dedicated experiments were performed under a broad range of operating parameters. These experiments included spectral measurements of BPM signals as well as time domain diagnostics using a custom detecting circuit. This paper describes the techniques, the results and discusses possible interpretations of these measurements.

The importance of the performance of threads libraries is growing as clusters of shared memory machines become more popular POSIX threads, or Pthreads, is an industry threads library standard. We have implemented the first Pthreads benchmark suite. In addition to measuring basic thread functions, such as thread creation, we apply the L.ogP model to standard Pthreads communication mechanisms. We present the results of our tests for several hardware platforms. These results demonstrate that the performance of existing Pthreads implementations varies widely; parts of nearly all of these implementations could be further optimized. Since hardware differences do not fully explain these performance variations, optimizations could improve the implementations. 2. Incorporating Threads Benchmarks into SKaMPI is an MPI benchmark suite that provides a general framework for performance analysis [7]. SKaMPI does not exhaustively test the MPI standard. Instead, it

At Lawrence Livermore National Laboratory (LLNL), we have the unique combination of precision turning and metrology capabilities critical to the fabrication of large optical elements. We have developed a self-referenced interferometer to measure errors in aspheric optics to sub- nanometer accuracy over 200-millimeter apertures, a dynamic range of 5{approximately}10. We have utilized diamond turning to figure optics for X-ray to IR wavelengths and, with fast-tool-servo technology, can move optical segments from off-axis to on-axis. With part capacities to 2.3-meters diameter and the metrology described above, segments of very large, ultra-lightweight mirrors can potentially be figured to final requirements. precision of diamond-turning will carryover although the surface finish may be degraded. Finally, the most critical component of a fabrication process is the metrology that enables an accurate part. Well characterized machines are very repeatable and part accuracy must come from proper metrology. A self- referencing interferometer has been developed that can measure accurately to sub-nanometer values. As with traditional interferometers, measurements are fast and post- processed data provides useful feedback to the user. The simplicity of the device allows it to be used on large optics and systems.

A total energy cycle analysis (TECA) of electric vehicles (EV) was recently completed. The EV energy cycle includes production and transport of fuels used in power plants to generate electricity, electricity generation, EV operation, and vehicle and battery manufacture. This paper summarizes the key assumptions and results of the EVTECA. The total energy requirements of EVS me estimated to be 24-35% lower than those of the conventional, gasoline-fueled vehicles they replace, while the reductions in total oil use are even greater: 55-85%. Greenhouse gases (GHG) are 24-37% lower with EVs. EVs reduce total emissions of several criteria air pollutants (VOC, CO, and NO{sub x}) but increase total emissions of others (SO{sub x}, TSP, and lead) over the total energy cycle. Regional emissions are generally reduced with EVs, except possibly SO{sub x}. The limitations of the EVTECA are discussed, and its results are compared with those of other evaluations of EVs. In general, many of the results (particularly the oil use, GHG, VOC, CO, SO{sub x}, and lead results) of the analysis are consistent with those of other evaluations.

A computational fluid dynamic (CFD) computer code was used to determine the effects of product yields of three feed injection parameters in a fluidized catalytic cracking (FCC) riser reactor. This study includes the effects of both symmetrical and non-symmetrical injection parameters. All these parameters have significant effects on the feed oil spray distribution, vaporization rates and the resulting product yields. This study also indicates that optimum parameter ranges exist for the investigated parameters.

Slow-positron beams produced from negative-work-function solid-state moderators have found numerous applications in condensed matter physics. There are potential advantages in using low-energy primary electron beams for positron production, including reduced radiation damage to single-crystal moderators and reduced activation of nearby components. We present numerical calculations of positron yields and other beam parameters for various target-moderator configurations using the Argonne Wakefield Accelerator (AWA) [1] and Advanced Photon Source (APS) [2] electron linacs [3] as examples of sources for the primary electron beams. The status of experiments at these facilities is reviewed.

Photoelectrons produced through the interaction of synchrotrons radiation and the vacuum chamber walls can be accelerated by a charged particle beam, acquiring sufficient energy to produce secondary electrons (SES) in collisions with the walls. If the secondary-electron yield (SEY) coefficient of the wall material is greater than one, a run-away condition can develop. In addition to the SEY, the degree of amplification depends on the beam intensity and temporal distribution. As the electron cloud builds up along a train of stored bunches, a transverse perturbation of the head bunch can be communicated to trailing bunches in a wakefield-like interaction with the cloud. The electron cloud effect is especially of concern for the high-intensity PEP-II (SLAC) and KEK B-factories and at the Large Hadron Collider (LHC) at CERN. An initiative was undertaken at the Advanced Photon Source (APS) storage ring to characterize the electron cloud in order to provide realistic limits on critical input parameters in the models and improve their predictive capabilities. An intensive research program was undertaken at CERN to address key issues relating to the LHC. After giving an overview, the recent theoretical and experimental results from the APS and the other laboratories will be discussed.