106 Matching Results

Search Results

Advanced search parameters have been applied.
in publisher: "Stanford Linear Accelerator Center"  
Results: 1 - 24 next
open access

Relationship of field components and the matched dispersion function in Arc achromats

Description: The general integral condition connecting the field, its derivative and the resulting eta function derived for any lattice is applied to the achromats of the SLC Arcs. This condition can be combined with the non-dispersive condition to give a simple parameterization of second-order achromats constructed of combined function magnets.
Date: August 28, 1986
Creator: Fieguth, T.; Kheifets, S. & Murray, J. J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

New magic angle bumps and magic translation bumps

Description: SLC beams of opposite charge can be transversely deflected in the same direction by RF fields in the accelerating cavities caused by girder tilts, coupler-asymmetries, or manufacturing errors. A symmetric deflection can be corrected by a magic angle bump if the deflection is located adjacent to one of the linac quadrupoles. However, if the deflection is located between quadrupoles, two magic angle bumps or a magic angle bump and a magic translation bump are needed for the correction. Several ex… more
Date: October 28, 1983
Creator: Seeman, J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Sharp Reduction of the Secondary Electron Emission Yield from Grooved Surfaces

Description: The effect of an artificially-enhanced rough surface on the secondary electron emission yield (SEY) was investigated both theoretically and experimentally. Analytical studies on triangular and rectangular grooved surfaces show the connection between the characteristic parameters of a given geometry to the SEY reduction. The effect of a strong magnetic field is also discussed. SEY of grooved samples have been measured and the results agree with Monte-Carlo simulations.
Date: November 28, 2007
Creator: Pivi, M. T. F.; King, F. K.; Kirby, R. E.; Ruabenheimer, T. O.; Stupakov, G. & Le Pimpec, F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Distortion of Crabbed Bunch Due to the Electron Cloud

Description: In order to improve the luminosity, two crab cavities have been installed in KEKB HER and LER [1]. Since there is only one crab cavity in each ring, the crab cavity generates a horizontally titled bunch along the whole ring. The achieved specific luminosity with crabbed bunch is higher, but it is not as high as that from beam-beam simulation [2]. One of the suspicions is the electron cloud. The electron cloud in LER (positron beam) may distort the crabbed bunch and cause the luminosity drop. Th… more
Date: May 28, 2008
Creator: Wang, L. & Raubenheimer, T.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Dielectric Wakefield Accelerator Experiments at the SABER Facility

Description: Electron bunches with the unparalleled combination of high charge, low emittances, and short time duration, as first produced at the SLAC Final Focus Test Beam (FFTB), are foreseen to be produced at the SABER facility. These types of bunches have enabled wakefield driven accelerating schemes of multi-GV/m in plasmas. In the context of the Dielectric Wakefield Accelerators (DWA) such beams, having rms bunch length as short as 20 um, have been used to drive 100 um and 200 um ID hollow tubes above… more
Date: January 28, 2008
Creator: Kanareykin, A.; Thompson, M. C.; Berry, M. K.; Blumenfeld, I.; Decker, F. J.; Hogan, M. J. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Search for CPT and Lorentz Violation in B0-B0bar Oscillations with Dilepton Events

Description: We report results of a search for CPT and Lorentz violation in B{sup 0}-{bar B}{sup 0} oscillations using inclusive dilepton events from 232 million {Upsilon}(4S) {yields} B{bar B} decays recorded by the BABAR detector at the PEP-II B Factory at SLAC. We find 2.8{sigma} significance, compatible with no signal, for variations in the complex CPT violation parameter z at the Earth's sidereal frequency and extract values for the quantities {Delta}a{sub {mu}} in the general Lorentz-violating standar… more
Date: November 28, 2007
Creator: Collaboration, The BABAR & Aubert, B.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Optical Damage Threshold of Silicon for Ultrafast Infrared Pulses

Description: We present measurements of the optical damage threshold of crystalline silicon in air for ultrafast pulses in the near infrared. The wavelengths tested span a range from the telecommunications band at 1550 nm, extending to 2260 nm. We discuss the motivation for the measurements and give theoretical context. We then describe the experimental setup, diagnostics, and procedure. The results show a breakdown threshold of 0.2J/cm{sup 2} at 1550 nm and 1.06 ps FWHM pulse duration, and a weak dependenc… more
Date: November 28, 2007
Creator: Cowan, Benjamin M. & /Tech-X, Boulder /SLAC
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Highly Effective Polarized Electron Sources Based on Strained Semiconductor Superlattice with Distributed Bragg Reflector

Description: Resonance enhancement of the quantum efficiency of new polarized electron photocathodes based on a short-period strained superlattice structures is reported. The superlattice is a part of an integrated Fabry-Perot optical cavity. We demonstrate that the Fabry-Perot resonator enhances the quantum efficiency by the order of magnitude in the wavelength region of the main polarization maximum. The high structural quality implied by these results points to the very promising application of these pho… more
Date: November 28, 2007
Creator: Gerchikov, L. G.; Aulenbacher, K.; Clendenin, J. E.; Kuz'michev, V. V.; Mamaev, Yu. A.; Maruyama, T. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Summary of Polarized e-/e+ Source Presentations

Description: The development of polarized electron sources in the 1970s capable of generating beams for injection into electron accelerators has been a major enabling factor for spin physics with electrons during the past quarter century. These sources continue to be refined for higher polarization and better operability. Recent developments were presented at this workshop in both plenary sessions and in 2 separate parallel sessions. The ILC plans to utilize not only a polarized electron source but also a p… more
Date: November 28, 2007
Creator: Clendenin, J. E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Improvements in Monte Carlo Simulation of Large Electron Fields

Description: Two Monte Carlo systems, EGSnrc and Geant4, were used to calculate dose distributions in large electron fields used in radiotherapy. Source and geometry parameters were adjusted to match calculated results with measurement. Both codes were capable of accurately reproducing the measured dose distributions of the 6 electron beams available on the accelerator. Depth penetration was matched to 0.1 cm. Depth dose curves generally agreed to 2% in the build-up region, although there is an additional 2… more
Date: November 28, 2007
Creator: Faddegon, Bruce A.; /UC, San Francisco; Perl, Joseph & Asai, Makoto
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Photoemission Study of Cs-NF3 Activated GaAs(100) Negative Electron Affinity Photocathodes

Description: GaAs based negative electron affinity photocathodes activated with Cs and NF{sub 3} are used as polarized electron sources for linear accelerators. It is generally believed that the activation layer consists of CsF. The activation layers of Cs-NF{sub 3} on GaAs photocathodes are herein investigated using synchrotron radiation photoelectron spectroscopy (SR-PES). F1s, N1s and other core levels are recorded at photon energies ranging from 70eV to 820eV. Surprisingly, a significant amount of nitro… more
Date: May 28, 2008
Creator: Liu, Z.; Sun, Y.; Peterson, S. & Pianetta, P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

3C454.3 Revelas the Structure and Physics of its 'Blazar Zone'

Description: Recent multi-wavelength observations of 3C454.3, in particular during its giant outburst in 2005, put severe constraints on the location of the 'blazar zone', its dissipative nature, and high energy radiation mechanisms. As the optical, X-ray, and millimeter light-curves indicate, significant fraction of the jet energy must be released in the vicinity of the millimeter-photosphere, i.e. at distances where, due to the lateral expansion, the jet becomes transparent at millimeter wavelengths. We c… more
Date: November 28, 2007
Creator: Sikora, M.; Moderski, R. & Madejski, G.M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

SUSY at the ILC and Solving the LHC Inverse Problem

Description: Recently a large scale study of points in the MSSM parameter space which are problematic at the Large Hadron Collider (LHC) has been performed. This work was carried out in part to determine whether the proposed International Linear Collider (ILC) could be used to solve the LHC inverse problem. The results suggest that while the ILC will be a valuable tool, an energy upgrade may be crucial to its success, and that, in general, precision studies of the MSSM are more difficult at the ILC than has… more
Date: May 28, 2008
Creator: Gainer, James S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Factorization and resummation for collinear poles in QCD amplitudes

Description: We study the origin of subleading soft and collinear poles of form factors and amplitudes in dimensionally-regulated massless gauge theories. In the case of form factors of fundamental fields, these poles originate from a single function of the coupling, denoted G({alpha}{sub s}), depending on both the spin and gauge quantum numbers of the field. We relate G({alpha}{sub s}) to gauge-theory matrix elements involving the gluon field strength. We then show that G({alpha}{sub s}) is the sum of thre… more
Date: May 28, 2008
Creator: Dixon, Lance J.; Magnea, Lorenzo & Sterman, George
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

On the Possibility of Accelerating Positron on an Electron Wake at SABER

Description: A new approach for positron acceleration in non-linear plasma wakefields driven by electron beams is presented. Positrons can be produced by colliding an electron beam with a thin foil target embedded in the plasma. Integration of positron production and acceleration in one stage is realized by a single relativistic, intense electron beam. Simulations with the parameters of the proposed SABER facility [1] at SLAC suggest that this concept could be tested there.
Date: January 28, 2008
Creator: Ischebeck, R.; Joshi, C.; Katsouleas, T. C.; Muggli, P. & Wang, X.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Correlating Pulses from Two Spitfire, 800nm Lasers

Description: The E163 laser acceleration experiments conducted at SLAC have stringent requirements on the temporal properties of two regeneratively amplified, 800nm, Spitfire laser systems. To determine the magnitude and cause of timing instabilities between the two Ti:Sapphire amplifiers, we pass the two beams through a cross-correlator and focus the combined beam onto a Hamamatsu G1117 photodiode. The photodiode has a bandgap such that single photon processes are suppressed and only the second order, two-… more
Date: January 28, 2008
Creator: Colby, Eric R.; Mcguinness, C.; Zacherl, W. D. & Plettner, T.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Commissioning the LCLS Injector

Description: The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) project presently under construction at SLAC. The injector section, from drive laser and RF photocathode gun through first bunch compressor chicane, was installed in fall 2006. Initial system commissioning with an electron beam was completed in August 2007, with the goal of a 1.2-micron emittance in a 1-nC bunch clearly demonstrated. The second phase of commissioning, including second bunch compressor and full lina… more
Date: November 28, 2007
Creator: Akre, R.; Dowell, D.; Emma, P.; Frisch, J.; Gilevich, S.; Hays, G. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Master Integrals for Fermionic Contributions to Massless Three-Loop Form Factors

Description: In this letter we continue the calculation of master integrals for massless three-loop form factors by giving analytical results for those diagrams which are relevant for the fermionic contributions proportional to N{sub F}{sup 2}, N{sub F} {center_dot} N, and N{sub F}/N. Working in dimensional regularization, we express one of the diagrams in a closed form which is exact to all orders in {epsilon}, containing {Lambda}-functions and hypergeometric functions of unit argument. In all other cases … more
Date: November 28, 2007
Creator: Heinrich, G.; Huber, T. & Maitre, D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Measurements of the Semileptonic Decays \Bb\to D\ell\nub and \Bb\to D^*\ell\nub Using a Global Fit to D X\ell\nub Final States

Description: Semileptonic {bar B} decays to DX{ell}{bar {nu}} ({ell} = e or {mu}) are selected by reconstructing D{sup 0}{ell} and D{sup +}{ell} combinations from a sample of 230 million {Upsilon}(4S) {yields} B{bar B} decays recorded with the BABAR detector at the PEP-II e{sup +}e{sup -} collider at SLAC. A global fit to these samples in a 3-dimensional space of kinematic variables is used to determine the branching fractions {Beta}(B{sup -} {yields} D{sup 0}{ell}{bar {nu}}) = 2.36 {+-} 0.03 {+-} 0.12% and… more
Date: August 28, 2008
Creator: Aubert, Bernard; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Parametric Modeling of Electron Beam Loss in Synchrotron Light Sources

Description: Synchrotron light is used for a wide variety of scientific disciplines ranging from physical chemistry to molecular biology and industrial applications. As the electron beam circulates, random single-particle collisional processes lead to decay of the beam current in time. We report a simulation study in which a combined neural network (NN) and first-principles (FP) model is used to capture the decay in beam current due to Touschek, Bremsstrahlung, and Coulomb effects. The FP block in the combi… more
Date: November 28, 2007
Creator: Sayyar-Rodsari, B.; Schweiger, C.; Hartman, E.; Corbett, J.; Lee, M.; Lui, P. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Bunch Length Measurements in SPEAR3

Description: A series of bunch length measurements were made in SPEAR3 for two different machine optics. In the achromatic optics the bunch length increases from the low-current value of 16.6ps rms to about 30ps at 25ma/bunch yielding an inductive impedance of -0.17{Omega}. Reducing the momentum compaction factor by a factor of {approx}60 [1] yields a low-current bunch length of {approx}4ps rms. In this paper we review the experimental setup and results.
Date: November 28, 2007
Creator: Corbett, W.J.; Fisher, A.; Huang, X.; Safranek, J.; Sebek, J.; /SLAC et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Forces on the conductors of the Arc AG Magnet

Description: In the evaluation of the design of the support system for the Arc AG Magnets, factors which could deform or move the magnet have to be considered. Typically they are the ground movements, temperature effects, water vibrations, magnetic forces on the magnet and coil, and accidental human or equipment impacts. This note calculates the magnetic forces on the conductors at an excitation for a 50 GeV beam. It is found that the force is not negligible; therefore, a method to restrict the movement of … more
Date: December 28, 1983
Creator: Weng, W. T.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Asymmetric B-factory note

Description: Three main issues giving purpose to our visit to CERN, ESRF and DESY were to: assess the current thinking at CERN on whether Eta, the gas desorption coefficient, would continue to decrease with continued with continued beam cleaning, determine if the time between NEG reconditioning could be expanded, and acquire a knowledge of the basic fabrication processes and techniques for producing beam vacuum chambers of copper.
Date: August 28, 1990
Creator: Calderon, M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
Back to Top of Screen