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Touschek Background and Lifetime Studies for the SuperB Factory

Description: The novel crab waist collision scheme under test at the DA{Phi}NE Frascati {Phi}-factory finds its natural application to the SuperB project, the asymmetric e{sup +}e{sup -} flavour factory at very high luminosity with relatively low beam currents and reduced backgrounds. The SuperB accelerator design requires a careful choice of beam parameters to reach a good trade-off between different effects. We present here simulation results for the Touschek backgrounds and lifetime obtained for both the low and high energy rings for different machine designs. A first set of horizontal collimators has been studied to stop Touschek particles. A study of the distributions of the Touschek particle losses at the interaction region into the detectors for further investigations is underway.
Date: August 26, 2010
Creator: Boscolo, M.; Biagini, M.; Raimondi, P.; /Frascati; Sullivan, M.; /SLAC et al.

TOUSCHEK LIFETIME CALCULATIONS AND SIMULATIONS FOR NSLS-II

Description: The beam lifetime in most medium energy synchrotron radiation sources is limited by the Touschek effect, which describes the momentum transfer from the transverse into the longitudinal direction due to binary collisions between electrons. While an analytical formula exists to calculate the resulting lifetime, the actual momentum acceptance necessary to perform this calculation can only be determined by tracking. This is especially the case in the presence of small vertical apertures at insertion devices. In this case, nonlinear betatron coupling leads to beam losses at these vertical aperture restrictions. In addition, a realistic model of the storage ring is necessary for calculation of equilibrium beam sizes (particularly in the vertical direction) which are important for a self-consistent lifetime calculation.
Date: June 25, 2007
Creator: MONTAG,C.; BENGTSSON, J. & NASH, B.

Touschek Lifetime Calculations for NSLS-II

Description: The Touschek effect limits the lifetime for NSLS-II. The basic mechanism is Coulomb scattering resulting in a longitudinal momentum outside the momentum aperture. The momentum aperture results from a combination of the initial betatron oscillations after the scatter and the non-linear properties determining the resultant stability. We find that higher order multipole errors may reduce the momentum aperture, particularly for scattered particles with energy loss. The resultant drop in Touschek lifetime is minimized, however, due to less scattering in the dispersive regions. We describe these mechanisms, and present calculations for NSLS-II using a realistic lattice model including damping wigglers and engineering tolerances.
Date: May 4, 2009
Creator: Nash,B. & Kramer, S.

A Tow-Level Progressive Damage for Simulating Carbon-Fiber Textile Composites: Interim Report

Description: A numerical approach to model the elasto-plastic and tensile damage response of tri-axially braided carbon-fiber polymeric-matrix composites is developed. It is micromechanically based and consists of a simplified unit cell geometry, a plane-stress tow-level constitutive relationship, a one-dimensional undulation constitutive law, and a non-traditional shell element integration rule. The braided composite lamina is idealized as periodic in the plane, and a simplified three-layer representative volume (RV) is assembled from axial and braider tows and pure resin regions. The constituents in each layer are homogenized with an iso-strain assumption in the fiber-direction and an iso-stress condition in the other directions. In the upper and lower layers, the fiber-direction strain is additively decomposed into an undulation and a tow portion. A finite-deformation tow model predicts the plane-stress tow response and is coupled to the undulation constitutive relationship. The overall braid model is implemented in DYNA3D and works with traditional shell elements. The finite-deformation tow constitutive relationship is derived from the fiber elasticity and the isotropic elasto-plastic power-law hardening matrix response using a thermodynamic framework and simple homogenization assumptions. The model replicates tensile damage evolution, in a smeared sense, parallel and perpendicular to the fiber axis and is regularized to yield mesh independent results. The tow-level model demonstrates reasonable agreement, prior to damage, with detailed three-dimensional FE (finite element) elasto-plastic simulations of aligned, periodically arranged, uni-directional composites. The 3-layer braid model response is compared with predictions obtained from detailed micromechanical simulations of the braid's unit cell in uni-axial extension, shear, and flexure for three braid angles. The elastic properties show good agreement as does the non-linear response for loadings dominated by the axial tows. In loadings dominated by the braider tow response, the absence of a non-linear undulation model deteriorates the agreement. Nonetheless, the present approach is applicable to a broad range of ...
Date: July 1, 2000
Creator: Zywicz, E.

Toward a 20% Wind Electricity Supply in the United States: Preprint

Description: Since the U.S. Department of Energy (DOE) initiated the Wind Powering America (WPA) program in 1999, installed wind power capacity in the United States has increased from 2,500 MW to more than 11,000 MW. In 1999, only four states had more than 100 MW of installed wind capacity; now 16 states have more than 100 MW installed. In addition to WPA's efforts to increase deployment, the American Wind Energy Association (AWEA) is building a network of support across the country. In July 2005, AWEA launched the Wind Energy Works! Coalition, which is comprised of more than 70 organizations. In February 2006, the wind deployment vision was enhanced by President George W. Bush's Advanced Energy Initiative, which refers to a wind energy contribution of up to 20% of the electricity consumption of the United States. A 20% electricity contribution over the next 20 to 25 years represents 300 to 350 gigawatts (GW) of electricity. This paper provides a background of wind energy deployment in the United States and a history of the U.S. DOE's WPA program, as well as the program's approach to increasing deployment through removal of institutional and informational barriers to a 20% wind electricity future.
Date: May 1, 2007
Creator: Flowers, L. & Dougherty, P.

Toward a cold electron beam in the Fermilab's Electron Cooler

Description: Fermilab is developing a high-energy electron cooling system to cool 8.9-GeV/c antiprotons in the Recycler ring [1]. Cooling of antiprotons requires a round electron beam with a small angular spread propagating through 20-m long cooling section with a kinetic energy of 4.3 MeV. To confine the electron beam tightly and to keep its transverse angles below 0.1 mrad, the cooling section will be immersed into a solenoidal field of 50-150G. This paper describes the technique of measuring and adjusting the magnetic field quality in the cooling section and presents preliminary results of beam quality measurements in the cooler prototype.
Date: May 12, 2004
Creator: al., Vitali S. Tupikov et

Toward a common component architecture for high-performance scientific computing

Description: This paper describes work in progress to develop a standard for interoperability among high-performance scientific components. This research stems from growing recognition that the scientific community must better manage the complexity of multidisciplinary simulations and better address scalable performance issues on parallel and distributed architectures. Driving forces are the need for fast connections among components that perform numerically intensive work and parallel collective interactions among components that use multiple processes or threads. This paper focuses on the areas we believe are most crucial for such interactions, namely an interface definition language that supports scientific abstractions for specifying component interfaces and a ports connection model for specifying component interactions.
Date: June 9, 1999
Creator: Armstrong, R.; Gannon, D.; Geist, A.; Katarzyna, K.; Kohn, S.; McInnes, L. et al.

Toward a competitive electric power industry for the 21. century. Comprehensive Review of the Northwest Energy System final report

Description: This report contains a review of the activities and the recommendations of the Steering Committee of the Comprehensive Review of the Northwest Energy System. The topics of the report include a summary of recommendations; federal power marketing; preserving the benefits of low-cost hydropower for the Northwest; Columbia River System governance; reflecting the values and meeting the needs of northwest citizens through conservation, renewable resources and low-income energy services; ensuring the benefits of competition for all by consumer access to the competitive market; open-access power transmission for competion in generation; and the future power system role for a four-state regional body. An appendix contains a dissenting opinion.
Date: December 12, 1996

Toward a comprehensive theory of radiation-induced swelling and creep - the point defect concentrations

Description: The theory of void swelling and irradiation creep is now fairly comprehensive. A unifying concept on which most of this understanding rests is that of the rate theory point defect concentrations. Several basic aspects of this unifying conept are reviewed. These relate to local fluctuations in point defect concentrations produced by cascades, the effects of thermal and radiation-produced divacancies, and the effects of point defect trapping.
Date: January 1, 1979
Creator: Mansur, L.K. & Yoo, M.H.

Toward a constructive physics

Description: We argue that the discretization of physics which has occurred thanks to the advent of quantum mechanics has replaced the continuum standards of time, length and mass which brought physics to maturity by counting. The (arbitrary in the sense of conventional dimensional analysis) standards have been replaced by three dimensional constants: the limiting velocity c, the unit of action h, and either a reference mass (eg m/sub p/) or a coupling constant (eg G related to the mass scale by hc/(2..pi..Gm/sub p//sup 2/) approx. = 1.7 x 10/sup 38/). Once these physical and experimental reference standards are accepted, the conventional approach is to connect physics to mathematics by means of dimensionless ratios. But these standards now rest on counting rather than ratios, and allow us to think of a fourth dimensionless mathematical concept, which is counting integers. According to constructive mathematics, counting has to be understood before engaging in the practice of mathematics in order to avoid redundancy. In its strict form constructive mathematics allows no completed infinities, and must provide finite algorithms for the computation of any acceptable concept. This finite requirement in constructive mathematics is in keeping with the practice of physics when that practice is restricted to hypotheses which are testable in a finite time. In this paper we attempt to outline a program for physics which will meet these rigid criteria while preserving, in so far as possible, the successes that conventional physics has already achieved.
Date: June 1, 1983
Creator: Noyes, H.P.; Gefwert, C. & Manthey, M.J.

Toward a Deeper Understanding of Plutonium

Description: Plutonium is a very complex element lying near the middle of the actinide series. On the lower atomic number side of Pu is the element neptunium; its 5f electrons are highly delocalized or itinerant, participating in metallic-like bonding. The electrons in americium, the element to the right of Pu, are localized and do not participant significantly in the bonding. Plutonium is located directly on this rather abrupt transition. In the low-temperature {alpha} phase ground state, the five 5f electrons are mostly delocalized leading to a highly dense monoclinic crystal structure. Increases in temperature take the unalloyed plutonium through a series of five solid-state allotropic phase transformations before melting. One of the high temperature phases, the close-packed face centered cubic {delta} phase, is the least dense of all the phases, including the liquid. Alloying the Pu with Group IIIA elements such as aluminum or gallium retains the {delta} phase in a metastable state at ambient conditions. Ultimately, this metastable {delta} phase will decompose via a eutectoid transformation to {alpha} + Pu{sub 3}Ga. These low solute-containing {delta}-phase Pu alloys are also metastable with respect to low temperature excursions or increases in pressure and will transform to a monoclinic crystal structure at low temperatures via an isothermal martensitic phase transformation or at slightly elevated pressure. The delocalized to localized 5f electron bonding transition that occurs in the light actinides surrounding Pu gives rise to a plethora of unique and anomalous properties but also severely complicates the modeling and simulation. The development of theories and models that are sufficiently sensitive to capture the details of this transition and capable of elucidating the fundamental properties of plutonium and plutonium alloys is currently a grand challenge in actinide science. Recent advances in electronic structure theory, semi-empirical interatomic potentials, and raw computing power have enabled remarkable progress ...
Date: June 21, 2007
Creator: Schwartz, A J & Wolfer, W G

Toward a defense-dominated world

Description: Maintaining the large-scale peace in a defense-dominated world necessarily will require not only passive but also active defenses against large-scale aggression that are technically feasible, practical and easy to employ -- and robust against perversion into support of aggression. Such peace maintenance tool-sets will feature means for effectively rebuking aggression as well as providing timely and very widely available seaming of aggression underway anywhere. This report discusses the technology base which currently exists to provide world-wide, high-quality imagery at moderate (5--10 meter) spatial resolution or imagery of 1% of the Earth`s land surface at high ({le} 1 meter) resolution no less frequently than daily, at a total cost of the order of $1 B, with operational capability in the later `90s. Such systems could provide timely warning of aggressive actions anywhere. Similarly, space-based means of defeating aggression conducted with even quite short-range ballistic missiles anywhere in the world could be brought into existence by the end of the `90s for a total cost of about $10 B, and small high-altitude, long flight-duration robotic aircraft carrying high-performance sensors and interceptor missilery could provide both seaming and active defenses against attacks conducted with very short range ballistic missiles, as well as attacks launched with air-breathing threats such as bombers and cruise missiles, for a cost per defended area of the order of $10/km{sup 2}. It appears that all of the associated sensors can find apt dual-use as high-performance systems for monitoring physical aspects of the human environment.
Date: August 1, 1993
Creator: Wood, L.

Toward a design for the ITER plasma shape and stability control system

Description: A design strategy for an integrated shaping and stability control algorithm for ITER is described. This strategy exploits the natural multivariable nature of the system so that all poloidal field coils are used to simultaneously control all regulated plasma shape and position parameters. A nonrigid, flux-conserving linearized plasma response model is derived using a variational procedure analogous to the ideal MHD Extended Energy Principle. Initial results are presented for the non-rigid plasma response model approach applied to an example DIII-D equilibrium. For this example, the nonrigid model is found to yield a higher passive growth rate than a rigid current-conserving plasma response model. Multivariable robust controller design methods are discussed and shown to be appropriate for the ITER shape control problem.
Date: July 1, 1994
Creator: Humphreys, D. A.; Leuer, J. A.; Kellman, A. G.; Haney, S. W.; Bulmer, R. H.; Pearlstein, L. D. et al.

Toward a Diurnal Climatology of Cold-Season Turbulence Statistics in Continental Stratocumulus as Observed by the Atmospheric Radiation Millimeter- Wavelength Cloud Radars

Description: Numerous observational studies of marine stratocumulus have demonstrated a pronounced diurnal cycle. At night, longwave flux divergence at the top of the cloud drives negatively buoyant eddies that tend to keep the boundary layer well mixed. During the day, solar absorption by the cloud tends to reduce the turbulent intensity and often decouples the planetary boundary layer (PBL) into cloud- and sub-cloud circulations. The delicate balance between turbulent intensity, entrainment, and fluxes dictates cloud geometry and persistence, which can significantly impact the shortwave radiation budget. Millimeter-wavelength cloud radars (MMCRs) have been used to study the turbulent structure of boundary layer stratocumulus (e.g. Frisch et al. 1995; Kollias and Albrecht 2000). Analysis is confined to nondrizzling or lightly drizzling cloud systems for which precipitation contamination is negligible. Under such assumptions the Doppler velocity field becomes a proxy for vertical velocity. Prior research has mainly consisted of a few case studies of specific cloud systems using radar scan strategies optimized for this particular cloud type. The MMCR operating at the Southern Great Plains Atmospheric Radiation Measurement Climate Research Facility is broadly configured to be able to detect many different cloud types over a broad range of reflectivities and altitudes, so it is not specifically optimized for PBL clouds. Being in more-or-less continuous operation since the end of 1996, it does, however, have the advantage of long data coverage, which suggests that statistically significant measures of the diurnal cycle of turbulence should be attainable. This abstract summarizes the first few steps toward this goal, using 7 months of cold season MMCR data.
Date: March 18, 2005
Creator: Mechem, D.B.; Kogan, Y.L.; Childers, M.E. & Donner, K.M.

Toward a fourth-generation light source.

Description: Historically, x-ray research has been propelled by the existence of urgent and compelling scientific questions and the push of powerful and exquisite source technology. These two factors have gone hand in hand since Rontgen discovered x-rays. Here we review the progress being made with existing third-generation synchrotron-radiation light sources and the prospects for a fourth-generation light source with dramatically improved laser-like beam characteristics. The central technology for high-brilliance x-ray beams is the x-ray undulator, a series of alternating-pole magnets situated above and below the particle beam. When the particle beam is oscillated by the alternating magnetic fields, a set of. interacting and interfering wave fronts is produced, which leads to an x-ray beam with extraordinary properties. Third-generation sources of light in the hard x-ray range have been constructed at three principal facilities: the European Synchrotrons Radiation Facility (ESRF) in France; the Super Photon Ring 8-GeV (or Spring-8) in Japan; and the Advanced Photon Source (APS) in the US. Undulator technology is also used on a number of low-energy machines for radiation in the ultraviolet and soft x-ray regimes. At the APS, these devices exceed all of our original expectations for beam brilliance, tunability, spectral range, and operational flexibility. Shown in Fig. 1 are the tuning curves of the first few harmonics, showing x-ray production from a few kV to better than 40 keV. High-brilliance radiation extends to over 100 keV.
Date: May 3, 1999
Creator: Moncton, D. E.

Toward a fourth-generation x-ray source.

Description: The field of synchrotron radiation research has grown rapidly over the last 25 years due to both the push of the accelerator and magnet technology that produces the x-ray beams and the pull of the extraordinary scientific research that is possible with them. Three successive generations of synchrotrons radiation facilities have resulted in beam brilliances 11 to 12 orders of magnitude greater than the standard laboratory x-ray tube. However, greater advances can be easily imagined given the fact that x-ray beams from present-day facilities do not exhibit the coherence or time structure so familiar with the optical laser. Theoretical work over the last ten years or so has pointed to the possibility of generating hard x-ray beams with laser-like characteristics. The concept is based on self-amplified spontaneous emission (SASE) in flee-electron lasers. A major facility of this type based upon a superconducting linac could produce a cost-effective facility that spans wave-lengths from the ultraviolet to the hard x-ray regime, simultaneously servicing large numbers experimenters from a wide range of disciplines. As with each past generation of synchrotrons facilities, immense new scientific opportunities would result from fourth-generation sources.
Date: May 19, 1999
Creator: Monction, D. E.

Toward a general description of two-body hadron reactions

Description: A model for describing two-body high energy hadron reactions at energies above the resonance region is presented. Although no real theory yet exists, one can give a procedure for obtaining a (possibly correct) description of the amplitudes for any two-body resction (whatever the spins involved, including real and imaginary parts of amplitudes, any helicity flip pi exchange as well as vector and tensor exchanges, etc.). The most important new physical effect involved is using the appropriate t-dependent phase for the vacuum exchange amplitude (the Pomeron''), both in elastic scattering and in describing absorption effects. The Pomeron is not a Regge pole. The model is very simple to formulate and has a reasonable physical interpretation in terms of important unitarity effects and absorption. It allows one to understand the partial successes and the inadequacies of previous approaches such as the dual absorptive model the strong absorption model, the view that some amplitudes have Regge pole behavior while others do not, etc, All the 0/sup -/1/2/sup +/ reactions, np yields pn, and pp yields nn, cross sections, polarizations, and amplitudes; these include all the important kinds of helicity amplitudes for any two-body resctions, Apart from a few places the results are very good; it is argued that the few places where there may be some difficulty are due to effects we have left out rather than to the structure of the model. Although the input Reggeon exchanges are not all exchange degenerate, the phases of the output amplitudes after absorption show a remarkable and unexpected resemblance to what one would expect from exchange degenerate poles, apart from the necessity of having a zero structure related to important absorption corrections, A number of related results, some of which are considered puzzles are discussed (total cross section differences for pi N and KN, the ...
Date: January 1, 1973
Creator: Hartley, B.J. & Kane, G.L.

Toward a General Theory for Multiphase Turbulence Part I: Development and Gauging of the Model Equations

Description: A formalism for developing multiphase turbulence models is introduced by analogy to the phenomenological method used for single-phase turbulence. A sample model developed using the formalism is given in detail. The procedure begins with ensemble averaging of the exact conservation equations, with closure accomplished by using a combination of analytical and experimental results from the literature. The resulting model is applicable to a wide range of common multiphase flows including gas-solid, liquid-solid and gas-liquid (bubbly) flows. The model is positioned for ready extension to three-phase turbulence, or for use in two-phase turbulence in which one phase is accounted for in multiple size classes, representing polydispersivity. The formalism is expected to suggest directions toward a more fundamentally based theory, similar to the way that early work in single-phase turbulence has led to the spectral theory. The approach is unique in that a portion of the total energy decay rate is ascribed to each phase, as is dictated by the exact averaged equations, and results in a transport equation for energy decay rate associated with each phase. What follows is a straightforward definition of a turbulent viscosity for each phase, and accounts for the effect of exchange of fluctuational energy among phases on the turbulent shear viscosity. The model also accounts for the effect of slip momentum transfer among the phases on the production of turbulence kinetic energy and on the tensor character of the Reynolds stress. Collisional effects, when appropriate, are included by superposition. The model reduces to a standard form in limit of a single, pure material, and is expected to do a credible job of describing multiphase turbulent flows in a wide variety of regimes using a single set of coefficients.
Date: December 1, 2000
Creator: Kashiwa, B. A. & VanderHeyden, W. B.

Toward a high performance distributed memory climate model

Description: As part of a long range plan to develop a comprehensive climate systems modeling capability, the authors have taken the Atmospheric General Circulation Model originally developed by Arakawa and collaborators at UCLA and have recast it in a portable, parallel form. The code uses an explicit time-advance procedure on a staggered three-dimensional Eulerian mesh. The authors have implemented a two-dimensional latitude/longitude domain decomposition message passing strategy. Both dynamic memory management and interprocessor communication are handled with macro constructs that are preprocessed prior to compilation. The code can be moved about a variety of platforms, including massively parallel processors, workstation clusters, and vector processors, with a mere change of three parameters. Performance on the various platforms as well as issues associated with coupling different models for major components of the climate system are discussed.
Date: February 15, 1993
Creator: Wehner, M. F.; Ambrosiano, J. J.; Brown, J. C.; Dannevik, W. P.; Eltgroth, P. G.; Mirin, A. A. et al.

Toward a mechanistic understanding of radiation effects in materials

Description: Substantial progress has been made to understanding radiation effects in materials, and in formulating and testing a metallurgical approach for developing radiation-resistant alloys. This understanding is a combination of theoretical modeling with experiments using mixed spectrum fission reactors, fast reactors and ion irradiations. The development of materials with properties to meet the challenges of advanced reactors has four major steps: (1) the development of a mechanistic understanding of the behavior of materials during irradiation in appropriate environments; (2) selection of candidate materials based on physical, chemical, and mechanical properties; (3) development of these candidate materials through compositional and microstructural control to achieve the necessary properties and radiation damage resistance; and (4) the development of a database sufficient to support engineering design, performance analysis, and safety assessment. This paper will present a brief overview of the present understanding of radiation effects in materials, with emphasis on work performed at Oak Ridge National Laboratory as part of the U.S. fusion materials and basic energy sciences programs. Progress in fundamental understanding of void swelling, phase formation and stability, irradiation creep, and post-irradiation mechanical properties has been gained through comparison of experimental data with the predictions of theoretical models. Applications of the understanding of radiation effects in materials have led to the development of candidate structural materials for use in aggressive radiation environments such as fast breeder reactors and proposed fusion energy systems. Because of the successes associated with the development of radiation resistant austenitic stainless steels, it is believed that these principles will provide the basis for addressing radiation issues in a variety of materials systems.
Date: February 1, 1995
Creator: Pawel, J. E.; Bloom, E. E.; Mansur, L. K.; Rowcliffe, A. F.; Zinkle, S. J.; Stoller, R. E. et al.