The accumulator ring of the Spallation Neutron Source (SNS) at ORNL employs in its straight sections closely packed quadrupole doublemagnets with large aperture of R=15.1 cm an relatively short iron-to-iron distance of 51.4 cm. These quads have much extended fringe field, and magnetic interferences among them in the doublet assemblies is not avoidable. Though each magnet in the assemblies has been individually mapped to high accuracy of lower than 0.01 percent level, the experimental data including the magnetic interference effect will not be available. We have performed 3D computing simulations on a quadrupole doublet model in order to assess the degree of the interference and to obtain relevant data for the SNS commissioning and operation.

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High-precision analyses of supersymmetry parameters aim atreconstructing the fundamental supersymmetric theory and its breakingmechanism. A well defined theoretical framework is needed whenhigher-order corrections are included. We propose such a scheme,Supersymmetry Parameter Analysis SPA, based on a consistent set ofconventions and input parameters. A repository for computer programs isprovided which connect parameters in different schemes and relate theLagrangian parameters to physical observables at LHC and high energy e+e-linear collider experiments, i.e., masses, mixings, decay widths andproduction cross sections for supersymmetric particles. In addition,programs for calculating high-precision low energy observables, thedensity of cold dark matter (CDM) in the universe as well as the crosssections for CDM search experiments are included. The SPA scheme stillrequires extended efforts on both the theoretical and experimental sidebefore data can be evaluated in the future at the level of the desiredprecision. We take here an initial step of testing the SPA scheme byapplying the techniques involved to a specific supersymmetry referencepoint.

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This study examines the temporal variability of ocean heat uptake in observations and in climate models. Previous work suggests that coupled Atmosphere-Ocean General Circulation Models (A-OGCMs) may have underestimated the observed natural variability of ocean heat content, particularly on decadal and longer timescales. To address this issue, we rely on observed estimates of heat content from the 2004 World Ocean Atlas (WOA-2004) compiled by Levitus et al. (2005). Given information about the distribution of observations in WOA-2004, we evaluate the effects of sparse observational coverage and the infilling that Levitus et al. use to produce the spatially-complete temperature fields required to compute heat content variations. We first show that in ocean basins with limited observational coverage, there are important differences between ocean temperature variability estimated from observed and infilled portions of the basin. We then employ data from control simulations performed with eight different A-OGCMs as a test-bed for studying the effects of sparse, space- and time-varying observational coverage. Subsampling model data with actual observational coverage has a large impact on the inferred temperature variability in the top 300 and 3000 meters of the ocean. This arises from changes in both sampling depth and in the geographical areas sampled. Our …

There is compelling empirical [1] and theoretical [2] evidence that the global confinement of H-mode discharges increases as the pedestal pressure or temperature increases. Therefore, confidence in the performance of future machines requires an ability to predict the pedestal conditions in those machines. At this time, both the theoretical and empirical understanding of transport in the pedestal are incomplete and are inadequate to predict pedestal conditions in present or future machines. Recent empirical results might be evidence of a fundamental relation between the electron temperature T{sub e} and electron density n{sub e} profiles in the pedestal. A data set from the ASDEX-Upgrade tokamak has shown that {eta}{sub e}, the ratio between the scale lengths of the n{sub e} and T{sub e} profiles, exhibits a value of about 2 throughout the pedestal, despite a large range of the actual density and temperature values [3]. Data from the DIII-D tokamak show that over a wide range of pedestal density, the width of the steep gradient region for the T{sub e} profile is about 1-2 times the corresponding width for the n{sub e} profile, where both widths are measured from the plasma edge [4]. Thus, the barrier in the density might form a …

Understanding the stability physics of the H-mode pedestal in tokamak devices requires an accurate measurement of plasma current in the pedestal region with good spatial resolution. Theoretically, the high pressure gradients achieved in the edge of H-mode plasmas should lead to generation of a significant edge current density peak through bootstrap and Pfirsh-Schlueter effects. This edge current is important for the achievement of second stability in the context of coupled magneto hydrodynamic (MHD) modes which are both pressure (ballooning) and current (peeling) driven [1]. Many aspects of edge localized mode (ELM) behavior can be accounted for in terms of an edge current density peak, with the identification of Type 1 ELMs as intermediate-n toroidal mode number MHD modes being a natural feature of this model [2]. The development of a edge localized instabilities in tokamak experiments code (ELITE) based on this model allows one to efficiently calculate the stability and growth of the relevant modes for a broad range of plasma parameters [3,4] and thus provides a framework for understanding the limits on pedestal height. This however requires an accurate assessment of the edge current. While estimates of j{sub edge} can be made based on specific bootstrap models, their validity …

The modeling of dielectric and magnetic materials in the time domain is required for pulse power applications, pulsed induction accelerators, and advanced transmission lines. For example, most induction accelerator modules require the use of magnetic materials to provide adequate Volt-sec during the acceleration pulse. These models require hysteresis and saturation to simulate the saturation wavefront in a multipulse environment. In high voltage transmission line applications such as shock or soliton lines the dielectric is operating in a highly nonlinear regime, which require nonlinear models. Simple 1-D models are developed for fast parameterization of transmission line structures. In the case of nonlinear dielectrics, a simple analytic model describing the permittivity in terms of electric field is used in a 3-D finite difference time domain code (FDTD). In the case of magnetic materials, both rate independent and rate dependent Hodgdon magnetic material models have been implemented into 3-D FDTD codes and 1-D codes.

Dielectric Wall Accelerator (DWA) technology incorporates the energy storage mechanism, the switching mechanism, and the acceleration mechanism for electron beams. Electromagnetic simulations of DWA structures includes these effects and also details of the switch configuration and how that switch time affects the electric field pulse which accelerates the particle beam. DWA structures include both bi-linear and bi-spiral configurations with field gradients on the order of 20MV/m and the simulations include the effects of the beampipe, the beampipe walls, the DWA High Gradient Insulator (HGI) insulating stack, wakefield impedance calculations, and test particle trajectories with low emittance gain. Design trade-offs include the transmission line impedance (typically a few ohms), equilibration ring optimization, driving switch inductances, and layer-to-layer coupling effects and the associated affect on the acceleration pulse's peak value.

The high mass X-ray binary (HMXB) V0332+53 became active at the end of 2004, with the outburst being monitored by RXTE and INTEGRAL at hard X-rays. Here, the orbital parameters are measured with the hard X-ray data through the fitting of the Doppler-shifted spin periods. The derived orbital period and the eccentricity are consistent with those reported by Stella et al. (1985) from earlier EXOSAT observations, whereas the projected semimajor axis and the periastron longitude are found to differ, from 48 {+-} 4 to 86{sub -10}{sup +6} lt-s and from 313{sup o} {+-} 10 to 282{sup o} {+-} 14, respectively. This would indicate an angular speed of {ge} 1.6 {sup o} {+-} 0.9 yr{sup -1} for the orbit over the past 20 years. The periastron passage time, TJD 13367 {+-} 1, is just around the time when the intensity reached the maximum and, an orbital period earlier is the time when the outburst occurred. This correlation resembles the behavior of a Type I outburst. During the outburst the source spun up with {dot P}{sub spin} = 8.01{sub -1.14}{sup 1.00} x 10{sup -6} s day{sup -1}. The evolution of the pulse profile is highly intensity dependent. The separation of the double …

A time-of-flight imaging technique is introduced to visualize fluid flow and dispersion through porous media using NMR. As the fluid flows through a sample, the nuclear spin magnetization is modulated by RF pulses and magnetic field gradients to encode the spatial coordinates of the fluid. When the fluid leaves the sample, its magnetization is recorded by a second RF coil. This scheme not only facilitates a time-dependent imaging of fluid flow, it also allows a separate optimization of encoding and detection subsystems to enhance overall sensitivity. The technique is demonstrated by imaging gas flow through a porous rock.

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Under constant current electromigration, white tin(?-Sn)exhibited a resistance drop of up to 10 percent. It has a body centertetragonal (BCT) structure, and the resistivity along the aand b axes is35 percent smaller than that along the c axis.Microstructure evolutionunder electromigration could be responsible for the resistance drop.Synchrotron radiation white beam x-ray microdiffraction was used to studythis evolution. Both stress and grain orientation was studied.Grain-by-grain analysis was obtained from the diffracted Laue patternsabout the changes of grain orientation during electromigration testing inex-situ and in-situ samples. We observed that high resistance grainsreorient with respect to the neighboring low resistance grains, mostlikely by grain rotation of the latter. A different mechanism ofmicrostructure evolution under electromigration from the normal graingrowth is proposed and discussed.

Existing theoretical literature suggests that defect-free, pristine carbon nanotubes (CNTs) interact weakly with many gas molecules like H{sub 2}O, CO, NH{sub 3}, H{sub 2}, and so on. The case of NH{sub 3} is particularly intriguing because this is in disagreement with experimentally observed changes in electrical conductance of CNTs upon exposure to these gases. In order to explain such discrepancy, we have carried out Density Functional Theory (DFT) investigations of the role of common atomistic defects in CNT (Stone-Wales, monovacancy, and interstitial) on the chemisorption of NH{sub 3}. Computed binding energies, charge transfer, dissociation barriers, and vibrational modes are compared with existing experimental results on electrical conductance, thermal desorption and infrared spectroscopy.

A method is described for jointly using time-lapse multiple-offset cross-borehole ground-penetrating radar (GPR) travel time measurements and hydrological measurements to estimate field-scale soil hydraulic parameters and parameters of the petrophysical function, which relates soil porosity and water saturation to the effective dielectric constant. We build upon previous work to take advantage of a wide range of GPR data acquisition configurations and to accommodate uncertainty in the petrophysical function. Within the context of water injection experiments in the vadose zone, we test our inversion methodology with synthetic examples and apply it to field data. The synthetic examples show that while realistic errors in the petrophysical function cause substantial errors in the soil hydraulic parameter estimates,simultaneously estimating petrophysical parameters allows for these errors to be minimized. Additionally, we observe in some cases that inaccuracy in the GPR simulator causes systematic error in simulated travel times, making necessary the simultaneous estimation of a correction parameter. We also apply the method to a three-dimensional field setting using time-lapse GPR and neutron probe (NP) data sets collected during an infiltration experiment at the U.S. Department of Energy (DOE) Hanford site in Washington. We find that inclusion of GPR data in the inversion procedure allows for …

As the switching capabilities of solid-state devices increase, these devices are being incorporated into modulator designs for high voltage accelerator applications. Solid-state modulators based on inductive adder circuit topology have demonstrated great versatility with regard to pulse width and pulse repetition rate while maintaining fast pulse rise and fall times. Additionally, these modulators are capable of being scaled to higher output voltage and power levels. An explanation of the basic circuit operation will be presented as well as test data of several different hardware systems.