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A Study of Laser System Requirements for Application in Beam Diagnostics And Polarimetry at the ILC

Description: Advanced laser systems will be essential for a range of diagnostics devices and polarimetry at the ILC. High average power, high beam quality, excellent stability and reliability will be crucial in order to deliver the information required to attain the necessary ILC luminosity as well as for efficient polarimetry. The key parameters are listed together with the R & D required to achieve the necessary laser system performance.
Date: February 12, 2007
Creator: Dixit, S.; Delerue, N.; Foster, B.; Howell, D. F.; Peach, K.; Quelch, G. et al.
Partner: UNT Libraries Government Documents Department

Performance of the Integrated Tracker Towers of the GLAST Large Area Telescope

Description: The GLAST Large Area Telescope (LAT) is a high energy gamma ray observatory, mounted on a satellite that will be own in 2007. The LAT tracker consists of an array of tower modules, equipped with planes of silicon strip detectors (SSDs) interleaved with tungsten converter layers. Photon detection is based on the pair conversion process; silicon strip detectors will reconstruct tracks of electrons and positrons. The instrument is actually being assembled. The first towers have been already tested and integrated at Stanford Linear Accelerator Center (SLAC). An overview of the integration stages of the main components of the tracker and a description of the pre-launch tests will be given. Experimental results on the performance of the tracker towers will be also discussed.
Date: February 15, 2007
Creator: Brigida, M.; Caliandro, A.; Favuzzi, C.; Fusco, P.; Gargano, F.; Giglietto, N. et al.
Partner: UNT Libraries Government Documents Department

Performance of GAASP/GAAS Superlattice Photocathodes in High Energy Experiments using Polarized Electrons

Description: The GaAsP/GaAs strained superlattice photocathode structure has proven to be a significant advance for polarized electron sources operating with high peak currents per microbunch and relatively low duty factor. This is the characteristic type of operation for SLAC and is also planned for the ILC. This superlattice structure was studied at SLAC [1], and an optimum variation was chosen for the final stage of E-158, a high-energy parity violating experiment at SLAC. Following E-158, the polarized source was maintained on standby with the cathode being re-cesiated about once a week while a thermionic gun, which is installed in parallel with the polarized gun, supplied the linac electron beams. However, in the summer of 2005, while the thermionic gun was disabled, the polarized electron source was again used to provide electron beams for the linac. The performance of the photocathode 24 months after its only activation is described and factors making this possible are discussed.
Date: February 27, 2006
Creator: Brachmann, A.; Clendenin, J.E.; Maruyama, T.; Garwin, E.L.; Ioakemidi, K.; Prescott, C.Y. et al.
Partner: UNT Libraries Government Documents Department

Gamma Ray Bursts And Data Challenge One: Searching GRB in One Week of Simulated GLAST LAT Data

Description: GLAST (Gamma-ray Large Area Space Telescope) is a gamma-ray astronomy mission that will be launched in mid 2007. The main instrument is the LAT (Large Area Telescope), a pair conversion telescope with sensitivity in the range 20 MeV-300 GeV. Data Challenge One (DC1) was the simulation of one week of observation of the entire gamma-ray sky by the LAT detector. the simulated data was similar to the real data, which allowed for the development of scientific software. In this paper they present the GRB simulations and the detection algorithms developed by the GLAST GRB and Solar Flare Science Team.
Date: February 22, 2006
Creator: Longo, F.; Omodei, N.; Band, D.; Bonnell, J.T.; Brigida, M.; Cohen-Tanugi, J. et al.
Partner: UNT Libraries Government Documents Department

Hosing Instability in the Blow-Out Regime for Plasma-Wakefield Acceleration

Description: The electron hosing instability in the blow-out regime of plasma-wakefield acceleration is investigated using a linear perturbation theory about the electron blow-out trajectory in Lu et al. [in Phys. Rev. Lett. 96, 165002 (2006)]. The growth of the instability is found to be affected by the beam parameters unlike in the standard theory Whittum et al. [Phys. Rev. Lett. 67, 991 (1991)] which is strictly valid for preformed channels. Particle-in-cell simulations agree with this new theory, which predicts less hosing growth than found by the hosing theory of Whittum et al.
Date: February 13, 2008
Creator: Huang, C.; Lu, W.; Zhou, M.; Clayton, C.E.; Joshi, C.; Mori, W.B. et al.
Partner: UNT Libraries Government Documents Department

Intelligent Detector Design

Description: At a future e+e- linear collider, precision measurements of jets will be required in order to understand physics at and beyond the electroweak scale. Calorimetry will be used with other detectors in an optimal way to reconstruct particle 4-vectors with unprecedented precision. This Particle Flow Algorithm (PFA) approach is seen as the best way to achieve particle mass resolutions from dijet measurements in the range of {approx} 30%/{radical}E, resulting in innovative methods for choosing the calorimeter technology and optimizing the detector design.
Date: February 13, 2007
Creator: Graf, N.; Cassell, R.; Johnson, T.; McCormick, J.; /SLAC; Magill, S. et al.
Partner: UNT Libraries Government Documents Department

A Gravity Dual of Metastable Dynamical Supersymmetry Breaking

Description: Metastable, supersymmetry-breaking configurations can be created in flux geometries by placing antibranes in warped throats. Via gauge/gravity duality, such configurations should have an interpretation as supersymmetry-breaking states in the dual field theory. In this paper, we perturbatively determine the asymptotic supergravity solutions corresponding to D3-brane probes placed at the tip of the cascading warped deformed conifold geometry, which is dual to an SU(N+M) x SU(N) gauge theory. The backreaction of the antibranes has the effect of introducing imaginary anti-self-dual flux, squashing the compact part of the space and forcing the dilaton to run. Using the generalization of holographic renormalization to cascading geometries, we determine the expectation values of operators in the dual field theory in terms of the asymptotic values of the supergravity fields.
Date: February 4, 2008
Creator: DeWolfe, Oliver; U., /Colorado; Kachru, Shamit; Mulligan, Michael & /Stanford U., Phys. Dept. /SLAC
Partner: UNT Libraries Government Documents Department

Effects of Energy Chirp on Echo-Enabled Harmonic Generation Free-Electron Lasers

Description: We study effects of energy chirp on echo-enabled harmonic generation (EEHG). Analytical expressions are compared with numerical simulations for both harmonic and bunching factors. We also discuss the EEHG free-electron laser bandwidth increase due to an energy-modulated beam and its pulse length dependence on the electron energy chirp.
Date: February 23, 2009
Creator: Huang, Z.; Ratner, D.; Stupakov, G.; Xiang, D. & /SLAC
Partner: UNT Libraries Government Documents Department

Evidence for Color Transparency and Direct Hadron Production at RHIC

Description: The QCD color transparency of higher-twist contributions to the inclusive hadroproduction cross section, where the trigger proton is produced directly in a short-distance subprocess, can explain several remarkable features of high-p{sub T} proton production in heavy ion collisions which have recently been observed at RHIC: (a) the anomalous increase of the p {yields} {pi} ratio with centrality (b): the more rapid power-law fall-off at fixed x{sub T} = 2p{sub T}/{radical}s of the charged particle production cross section in high centrality nuclear collisions, and (c): the anomalous decrease of the number of same-side hadrons produced in association with a proton trigger as the centrality increases. These phenomena illustrate how heavy ion collisions can provide sensitive tools for interpreting and testing fundamental properties of QCD.
Date: February 4, 2008
Creator: Brodsky, S
Partner: UNT Libraries Government Documents Department

Difference Imaging of Lensed Quasar Candidates inthe SDSS Supernova Survey Region

Description: Difference imaging provides a new way to discover gravitationally lensed quasars because few non-lensed sources will show spatially extended, time variable flux. We test the method on lens candidates in the Sloan Digital Sky Survey (SDSS) Supernova Survey region from the SDSS Quasar Lens Search (SQLS) and their surrounding fields. Starting from 20768 sources, including 49 SDSS quasars and 36 candidate lenses/lensed images, we find that 21 sources including 15 SDSS QSOs and 7 candidate lenses/lensed images are non-periodic variable sources. We can measure the spatial structure of the variable flux for 18 of these sources and identify only one as a non-point source. This source does not display the compelling spatial structure of the variable flux of known lensed quasars, so we reject it as a lens candidate. None of the lens candidates from the SQLS survive our cuts. Given our effective survey area of order 0.71 square degrees, this indicates a false positive rate of order one per square degree for the method. The fraction of quasars not found to be variable and the false positive rate should both fall if we analyze the full, later data releases for the SDSS fields. While application of the method to the SDSS is limited by the resolution, depth, and sampling of the survey, several future surveys such as Pan-STARRS, LSST, and SNAP will avoid these limitations.
Date: February 4, 2008
Creator: Lacki, Brian C.; Kochanek, Christopher S.; Stanek, Krzysztof Z.; Inada, Naohisa & Oguri, Masamune
Partner: UNT Libraries Government Documents Department

Black Hole Attractors and Pure Spinors

Description: We construct black hole attractor solutions for a wide class of N = 2 compactifications. The analysis is carried out in ten dimensions and makes crucial use of pure spinor techniques. This formalism can accommodate non-Kaehler manifolds as well as compactifications with flux, in addition to the usual Calabi-Yau case. At the attractor point, the charges fix the moduli according to {Sigma}f{sub k} = Im(C{Phi}), where {Phi} is a pure spinor of odd (even) chirality in IIB (A). For IIB on a Calabi-Yau, {Phi} = {Omega} and the equation reduces to the usual one. Methods in generalized complex geometry can be used to study solutions to the attractor equation.
Date: February 21, 2006
Creator: Hsu, Jonathan P.; Maloney, Alexander & Tomasiello, Alessandro
Partner: UNT Libraries Government Documents Department

Analysis of Laser-Driven Particle Acceleration fromPlanar Infinite Conductive Boundaries

Description: This article explores the energy gain for a single relativistic electron from a monochromatic linearly polarized plane wave incident on a planar reflective boundary oriented at an arbitrary oblique angle, and compares the prediction for the energy gain from Inverse Transition Radiation method and the electric field path integral method. It is found that both methods predict the same energy gain regardless of the orientation of the boundary. A brief analysis on partially reflecting surfaces is presented.
Date: February 17, 2006
Creator: Plettner, T. & /Stanford U., Ginzton Lab.
Partner: UNT Libraries Government Documents Department

Annual Site Environmental Report: 2005

Description: This report provides information about environmental programs during 2005 at the Stanford Linear Accelerator Center (SLAC). Seasonal activities that span calendar years are also included. Production of an annual site environmental report (ASER) is a requirement established by the United States Department of Energy (DOE) for all management and operating (M&O) contractors throughout the DOE complex. SLAC is a federally-funded research and development center with Stanford University as the M&O contractor. SLAC effectively applied environmental management in meeting the site's integrated safety and environmental management system (ISEMS) goals. For normal daily activities, all SLAC managers and supervisors are responsible for ensuring that proper procedures are followed so that: (1) Worker safety and health are protected; (2) The environment is protected; and (3) Compliance is ensured. Throughout 2005, SLAC focused on these activities through the SLAC management systems (described in Chapter 3). These systems were also the way SLAC approached implementing ''greening of the government'' initiatives such as Executive Order 13148. The management systems at SLAC are effective, supporting compliance with all relevant statutory and regulatory requirements. There were no reportable releases to the environment from SLAC operations during 2005. In addition, many improvements were continued during 2005, in waste minimization, recycling, stormwater drain system, groundwater restoration, and implementing a chemical management system (CMS) to better manage chemical use. Program-specific details are discussed.
Date: February 3, 2007
Creator: sabba, d
Partner: UNT Libraries Government Documents Department

Anomalous Fermi-Surface Dependent Pairing in a Self-Doped High-T(c) Superconductor

Description: We report the discovery of a self-doped multilayer high T{sub c} superconductor Ba{sub 2}Ca{sub 3}Cu{sub 4}O{sub 8}F{sub 2} (F0234) which contains distinctly different superconducting gap magnitudes along its two Fermi-surface sheets. While formal valence counting would imply this material to be an undoped insulator, it is a self-doped superconductor with a T{sub c} of 60 K, possessing simultaneously both electron- and hole-doped Fermi-surface sheets. Intriguingly, the Fermi-surface sheet characterized by the much larger gap is the electron-doped one, which has a shape disfavoring two electronic features considered to be important for the pairing mechanism: the van Hove singularity and the antiferromagnetic ({pi}/{alpha}, {pi}/{alpha}) scattering.
Date: February 12, 2007
Creator: Chen, Yulin; Iyo, Akira; Yang, Wanli; Zhou, Xingjiang; Lu, Donghui; Eisaki, Hiroshi et al.
Partner: UNT Libraries Government Documents Department

A 3D Parallel Beam Dynamics Code for Modeling High Brightness Beams in Photoinjectors

Description: In this paper we report on IMPACT-T, a 3D beam dynamics code for modeling high brightness beams in photoinjectors and rf linacs. IMPACT-T is one of the few codes used in the photoinjector community that has a parallel implementation, making it very useful for high statistics simulations of beam halos and beam diagnostics. It has a comprehensive set of beamline elements, and furthermore allows arbitrary overlap of their fields. It is unique in its use of space-charge solvers based on an integrated Green function to efficiently and accurately treat beams with large aspect ratio, and a shifted Green function to efficiently treat image charge effects of a cathode. It is also unique in its inclusion of energy binning in the space-charge calculation to model beams with large energy spread. Together, all these features make IMPACT-T a powerful and versatile tool for modeling beams in photoinjectors and other systems. In this paper we describe the code features and present results of IMPACT-T simulations of the LCLS photoinjectors. We also include a comparison of IMPACT-T and PARMELA results.
Date: February 13, 2006
Creator: Qiang, Ji; Lidia, S.; Ryne, R.D.; /LBL, Berkeley; Limborg, C. & /SLAC
Partner: UNT Libraries Government Documents Department

Calculation of Beam-Loaded Q in High-Power Klystrons

Description: Instabilities in the gun region of a high-power klystron can occur when there is positive feedback between a mode and an induced current on the quasi-steady state beam emitted by the gun cathode[1]. This instability is dependent on the gun voltage, and is predicted on the basis of a negative total Q. The established method for computing the beam-loaded Q of a cavity involves using a time-dependent electromagnetic particle-in-cell (PIC) code to track beam particles through the quasi-static gun fields perturbed by the electromagnetic fields of a cavity eigenmode[2]. The energy imparted to the beam by the mode is obtained by integrating the Lorentz force along the particle tracks, and this quantity is simply related to the beam-loaded Q. We have developed an alternative approach that yields comparable accuracy but is computationally much simpler. The new method is based on a time-independent electrostatic PIC calculation, resulting in much faster solutions without loss of accuracy. We will present the theory and implementation of the new method, as well as benchmarks and results from analysis of the XP-4 klystron that show a potential instability near 3 GHz.
Date: February 22, 2006
Creator: DeFord, J.F.; Held, B.; /Unlisted; Ivanov, V.; Ko, K. & /SLAC
Partner: UNT Libraries Government Documents Department

Properties of Wide-separation Lensed Quasars byClusters of Galaxies in the SDSS

Description: We use high-resolution N-body numerical simulations to study the number of predicted large-separation multiply-imaged systems produced by clusters of galaxies in the SDSS photometric and spectroscopic quasar samples. We incorporate the condensation of baryons at the center of clusters by (artificially) adding a brightest central galaxy (BCG) as a truncated isothermal sphere. We make predictions in two at cosmological models: a {Lambda}CDM model with a matter density {Omega}{sub m,0} = 0.3, and {sigma}{sub 8} 0.9 ({Lambda}CDM0), and a model favored by the WMAP three-year data with {Omega}{sub m,0} = 0.238, and {sigma}{sub 8} = 0.74 (WMAP3). We found that the predicted multiply-imaged quasars with separation > 10 is about 6.2 and 2.6 for the SDSS photometric (with an effective area 8000 deg{sup 2}) and spectroscopic (with an effective area 5000 deg{sup 2}) quasar samples respectively in the {Lambda}CDM0 model; the predicted numbers of large-separation lensed quasars agree well with the observations. These numbers are reduced by a factor of 7 or more in the WMAP3 model, and are consistent with data at {approx}< 8% level. The predicted cluster lens redshift peaks around redshift 0.5, and 90% are between 0.3 and 1. The ratio of systems with at least four image systems (N{sub img} {ge} 4) and those with N{sub img} {ge} 2 is about 1/3.5 for both the {Lambda}CDM0 and WMAP3 models, and for both the photometric and spectroscopic quasar samples.We find that the BCG creates a central circular region, comparable to the Einstein ring of the BCG, where the central image disappears in the usual three-image and five-image configurations. If we include four image systems as an extreme case of five-image systems (with an infinitely demagnified central image), we find that 68% of the central images are fainter by a factor of 100 than the brightest image, and about ...
Date: February 3, 2007
Creator: Li, G.L.; Mao, S.; Jing, Y.P.; Lin, W.P. & Oguri, M.
Partner: UNT Libraries Government Documents Department

Beam Matching to a Plasma Wakefield Accelerator Using a Ramped Density Profile at the Plasma Boundary

Description: An important aspect of plasma wake field accelerators (PWFA) is stable propagation of the drive beam. In the under dense plasma regime, the drive beam creates an ion channel which acts on the beam as a strong thick focusing lens. The ion channel causes the beam to undergo multiple betatron oscillations along the length of the plasma. There are several advantages if the beam size can be matched to a constant radius. First, simulations have shown that instabilities such as hosing are reduced when the beam is matched [1]. Second, synchrotron radiation losses are minimized when the beam is matched. Third, an initially matched beam will propagate with no significant change in beam size in spite of large energy loss or gain. Coupling to the plasma with a matched radius can be difficult in some cases. This paper shows how an appropriate density ramp at the plasma entrance can be useful for achieving a matched beam. Additionally, the density ramp is helpful in bringing a misaligned trailing beam onto the drive beam axis. A plasma source with boundary profiles useful for matching has been created for the E-164X PWFA experiments at SLAC.
Date: February 17, 2006
Creator: Marsh, K.A.; Clayton, C.E.; Huang, C.; Johnson, D.K.; Joshi, C.; Lu, W. et al.
Partner: UNT Libraries Government Documents Department

Damping Wiggler Study at KEK-ATF

Description: The effects of damping wiggler magnets have been studied at KEK-ATF damping ring, which is a 1.3 GeV storage ring capable of producing ultra-low emittance electron beams. The fast beam damping is a significant issue for the damping ring. The tuning method with 4 sets of wiggler magnets was investigated for the ultra-low emittance beam. The effect on the beam quality, which is related to the transverse (x and y) and the longitudinal (z and {Delta}p/p), has been measured by the wire scanner, SR monitor, the laser wire, streak camera and the energy spread monitor. We report on the operational condition and the measurement results.
Date: February 7, 2006
Creator: Naito, T.; Hayano, H.; Honda, Y.; Kubo, K.; Kuriki, M.; Kuroda, S. et al.
Partner: UNT Libraries Government Documents Department

Observations And Measurements of Anomalous Hollow Electron Beams in a Storage Ring

Description: Anomalous hollow electron beams have been recently observed in the Duke storage ring. With a single bunch beam in a lattice with a negative chromaticity, a hollow beam can be created. This beam consists of a solid core beam inside and a large ring beam outside. In this paper, we report the measurements of the hollow beam phenomenon, including its distinct image pattern and spectrum signature, and its evolution with time. By capturing the post-instability bursting beam, the hollow beam is a unique model system for studying transverse instabilities, in particular, the interplay of the wakefield and lattice nonlinearity. The hollow beam can also be used as a tool to study linear and nonlinear particle dynamics in the storage ring.
Date: February 6, 2006
Creator: Wu, Y.K.; Li, J.; U., /Duke; Wu, J. & /SLAC
Partner: UNT Libraries Government Documents Department

Precise Predictions for W + 3 Jet Production at Hadron Colliders

Description: We report on the first next-to-leading order QCD computation of W + 3-jet production in hadronic collisions including all partonic subprocesses. We compare the results with CDF data from the Tevatron, and find excellent agreement. The renormalization and factorization scale dependence is reduced substantially compared to leading-order calculations. The required one-loop matrix elements are computed using on-shell methods, implemented in a numerical program, BlackHat. We use the SHERPA package to generate the real-emission contributions and to integrate the various contributions over phase space. We use a leading-color (large-N{sub c}) approximation for the virtual part, which we confirm in W + 1,2-jet production to be valid to within three percent. The present calculation demonstrates the utility of on-shell methods for computing next-to-leading-order corrections to processes important to physics analyses at the Large Hadron Collider.
Date: February 23, 2009
Creator: Berger, C.F.; /MIT, LNS; Bern, Z.; /UCLA; Dixon, L.J.; /SLAC et al.
Partner: UNT Libraries Government Documents Department

The Non-BPS Black Hole Attractor Equation

Description: We study the attractor mechanism for extremal non-BPS black holes with an infinite throat near horizon geometry, developing, as we do so, a physical argument as to why such a mechanism does not exist in non-extremal cases. We present a detailed derivation of the non-supersymmetric attractor equation. This equation defines the stabilization of moduli near the black hole horizon: the fixed moduli take values specified by electric and magnetic charges corresponding to the fluxes in a Calabi Yau compactification of string theory. They also define the so-called double-extremal solutions. In some examples, studied previously by Tripathy and Trivedi, we solve the equation and show that the moduli are fixed at values which may also be derived from the critical points of the black hole potential.
Date: February 8, 2006
Creator: Kollosh, R
Partner: UNT Libraries Government Documents Department

Optical Phase Locking of Modelocked Lasers for Particle Accelerators

Description: Particle accelerators require precise phase control of the electric field through the entire accelerator structure. Thus a future laser driven particle accelerator will require optical synchronism between the high-peak power laser sources that power the accelerator. The precise laser architecture for a laser driven particle accelerator is not determined yet, however it is clear that the ability to phase-lock independent modelocked oscillators will be of crucial importance. We report the present status on our work to demonstrate long term phaselocking between two modelocked lasers to within one degree of optical phase and describe the optical synchronization techniques that we employ.
Date: February 17, 2006
Creator: Plettner, T.; Sinha, S.; Wisdom, J.; /Stanford U., Phys. Dept.; Colby, E.R. & /SLAC
Partner: UNT Libraries Government Documents Department