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Cavity Beam Position Monitor System for ATF2

Description: The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a future high energy lepton linear collider. The ATF2 beam-line is instrumented with a total of 38 C and S band resonant cavity beam position monitors (CBPM) with associated mixer electronics and digitizers. The current status of the BPM system is described, with a focus on operational techniques and performance. The ATF2 C-band system is performing well, with individ… more
Date: July 9, 2012
Creator: Boogert, Stewart; /Oxford U., JAI; Boorman, Gary; /Oxford U., JAI; Swinson, Christina; /Oxford U., JAI et al.
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Partner: UNT Libraries Government Documents Department
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Matlab Based LOCO

Description: The LOCO algorithm has been used by many accelerators around the world. Although the uses for LOCO vary, the most common use has been to find calibration errors and correct the optics functions. The light source community in particular has made extensive use of the LOCO algorithms to tightly control the beta function and coupling. Maintaining high quality beam parameters requires constant attention so a relatively large effort was put into software development for the LOCO application. The LOCO… more
Date: October 18, 2011
Creator: Portmann, Greg; Safranek, James & Huang, Xiaobiao
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Eliminating the Renormalization Scale Ambiguity for Top-Pair Production Using the Principle of Maximum Conformality

Description: The uncertainty in setting the renormalization scale in finite-order perturbative QCD predictions using standard methods substantially reduces the precision of tests of the Standard Model in collider experiments. It is conventional to choose a typical momentum transfer of the process as the renormalization scale and take an arbitrary range to estimate the uncertainty in the QCD prediction. However, predictions using this procedure depend on the choice of renormalization scheme, leave a non-conv… more
Date: April 2, 2012
Creator: Brodsky, Stanley J. & Wu, Xing-Gang
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Partner: UNT Libraries Government Documents Department
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Electronic Structure and Oxidation State Changes in the Mn (4) Ca Cluster of Photosystem II

Description: Oxygen-evolving complex (Mn{sub 4}Ca cluster) of Photosystem II cycles through five intermediate states (S{sub i}-states, i = 0-4) before a molecule of dioxygen is released. During the S-state transitions, electrons are extracted from the OEC, either from Mn or alternatively from a Mn ligand. The oxidation state of Mn is widely accepted as Mn{sub 4}(III{sub 2},IV{sub 2}) and Mn{sub 4}(III,IV{sub 3}) for S{sub 1} and S{sub 2} states, while it is still controversial for the S{sub 0} and S{sub 3} … more
Date: August 17, 2012
Creator: Yano, J.; Pushkar, Y.; Messinger, J.; Bergmann, U.; Glatzel, P. & Yachandra, V. K.
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Partner: UNT Libraries Government Documents Department
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Mechanical Design of the HER Synchrotron Light Monitor Primary Mirror

Description: This paper describes the mechanical design of the primary mirror that images the visible portion of the synchrotron radiation (SR) extracted from the High Energy Ring (HER) of the PEP-II B-Factory. During off-axis operation, the water-cooled GlidCop mirror is subjected to a heat flux in excess of 2000 W/cm2. When on-axis imaging occurs, the heat flux due to scattered SR, resistive wall losses and Higher-Order-Mode (HOM) heating is estimated at 1 W/cm2. The imaging surface is plated with Electro… more
Date: September 14, 2011
Creator: Daly, Edward F.; Fisher, Alan S.; Kurita, Nadine R. & Langton, J.
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Partner: UNT Libraries Government Documents Department
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Present Status And First Results of the Final Focus Beam Line at the KEK Accelerator Test Facility

Description: ATF2 is a final-focus test beam line which aims to focus the low emittance beam from the ATF damping ring to a vertical size of about 37 nm and to demonstrate nanometer level beam stability. Several advanced beam diagnostics and feedback tools are used. In December 2008, construction and installation were completed and beam commissioning started, supported by an international team of Asian, European, and U.S. scientists. The present status and first results are described.
Date: November 11, 2011
Creator: Bambade, P.; Alabau Pons, M.; Amann, J.; Angal-Kalinin, D.; Apsimon, R.; Araki, S. et al.
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Partner: UNT Libraries Government Documents Department
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On The Origin Of High Energy Correlations in Gamma-ray Bursts

Description: I investigate the origin of the observed correlation between a gamma-ray burst's {nu}F{sub {nu}} spectral peak E{sub pk} and its isotropic equivalent energy E{sub iso} through the use of a population synthesis code to model the prompt gamma-ray emission from GRBs. By using prescriptions for the distribution of prompt spectral parameters as well as the population's luminosity function and co-moving rate density, I generate a simulated population of GRBs and examine how bursts of varying spectral… more
Date: April 3, 2012
Creator: Kocevski, Daniel
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Partner: UNT Libraries Government Documents Department
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Measurements of the Electron Cloud Density in the PEP-II Low Energy Ring

Description: Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation of these machines at high currents. Because of the size of these accelerators, it is difficult to probe the low energy electron clouds over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave that is independently excited and transmitted… more
Date: April 10, 2012
Creator: Byrd, J.; De Santis, S.; Sonnad, K.; Caspers, F.; Kroyer, T.; Krasnykh, A. et al.
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Partner: UNT Libraries Government Documents Department
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Laser Assisted Emittance Transfer for Storage Ring Lasing

Description: In modern storage rings the transverse emittance of electron beams can be comparable to that from state-of-art photoinjectors, but the intrinsic low peak current and large energy spread pre-cludes the possibility of realizing short-wavelength high-gain free electron lasers (FELs) in storage rings. In this note I propose a technique to significantly increase beam peak current without greatly increasing beam energy spread, which is achieved by transferring part of the longitudinal emittance to tr… more
Date: June 1, 2011
Creator: Xiang, Dao
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Partner: UNT Libraries Government Documents Department
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Suzaku And Multi-Wavelength Observations of OJ 287 During the Periodic Optical Outburst in 2007

Description: Suzaku observations of the blazar OJ 287 were performed in 2007 April 10-13 and November 7-9. They correspond to a quiescent and a flaring state, respectively. The X-ray spectra of the source can be well described with single power-law models in both exposures. The derived X-ray photon index and the flux density at 1 keV were found to be {Lambda} = 1.65 {+-} 0.02 and S{sub 1keV} = 215 {+-} 5 nJy, in the quiescent state. In the flaring state, the source exhibited a harder X-ray spectrum ({Lambda… more
Date: December 1, 2011
Creator: Seta, Hiromi; Isobe, N.; Tashiro, Makoto S.; Yaji, Yuichi; Arai, Akira; Fukuhara, Masayuki et al.
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Partner: UNT Libraries Government Documents Department
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A Compact Ring Design with Tunable Momentum Compaction

Description: A storage ring with tunable momentum compaction has the advantage in achieving different RMS bunch length with similar RF capacity, which is potentially useful for many applications, such as linear collider damping ring and predamping ring where injected beam has a large energy spread and a large transverse emittance. A tunable bunch length also makes the commissioning and fine tuning easier in manipulating the single bunch instabilities. In this paper, a compact ring design based on a supercel… more
Date: May 17, 2012
Creator: Sun, Y.
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Partner: UNT Libraries Government Documents Department
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A 4 to 0.1 nm FEL Based on the SLAC Linac

Description: The author show that using existing electron gun technology and a high energy linac like the one at SLAC, it is possible to build a Free Electron Laser operating around the 4 nm water window. A modest improvement in the gun performance would further allow to extend the FEL to the 0.1 nm region. Such a system would produce radiation with a brightness many order of magnitude above that of any synchrotron radiation source, existing or under construction, with laser power in the multigawatt region … more
Date: June 5, 2012
Creator: Pellegrini, C.
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Partner: UNT Libraries Government Documents Department
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Electron Anomalous Magnetic Moment in Basis Light-Front Quantization Approach

Description: We apply the Basis Light-Front Quantization (BLFQ) approach to the Hamiltonian field theory of Quantum Electrodynamics (QED) in free space. We solve for the mass eigenstates corresponding to an electron interacting with a single photon in light-front gauge. Based on the resulting non-perturbative ground state light-front amplitude we evaluate the electron anomalous magnetic moment. The numerical results from extrapolating to the infinite basis limit reproduce the perturbative Schwinger result w… more
Date: February 17, 2012
Creator: Zhao, Xingbo; Honkanen, Heli; Maris, Pieter; Vary, James P. & Brodsky, Stanley J.
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Partner: UNT Libraries Government Documents Department
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Design and Factory Test of the E /E- Frascati Linear Accelerator for DAFNE

Description: The electron-positron accelerator for the DAFNE project has been built and is in test at Titan Beta in Dublin, CA. This S-Band RF linac system utilizes four 45 MW sledded klystrons and 16-3 m accelerating structures to achieve the required performance. It delivers a 4 ampere electron beam to the positron converter and accelerates the resulting positrons to 550 MeV. The converter design uses a 4.3T pulsed tapered flux compressor along with a pseudo-adiabatic tapered field to a 5 KG solenoid over… more
Date: November 28, 2011
Creator: Anamkath, H.; Lyons, S.; Nett, D.; Treas, P.; Whitham, K.; Zante, T. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Resolving Lifshitz Horizons

Description: Via the AdS/CFT correspondence, ground states of field theories at finite charge density are mapped to extremal black brane solutions. Studies of simple gravity + matter systems in this context have uncovered wide new classes of extremal geometries. The Lifshitz metrics characterizing field theories with non-trivial dynamical critical exponent z {ne} 1 emerge as one common endpoint in doped holographic toy models. However, the Lifshitz horizon exhibits mildly singular behaviour - while curvatur… more
Date: April 24, 2012
Creator: Harrison, Sarah; Kachru, Shamit; Wang, Huajia & /Stanford U., ITP /Stanford U., Phys. Dept. /SLAC
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Search for the Z_1(4050)^+ and Z_2(4250)^+ States in bar B^0 to chi_{c1} K^- pi^+ and B^+ to chi_{c1} K^0_S pi^+

Description: We search for the Z{sub 1}(4050){sup +} and Z{sub 2}(4250){sup +} states, reported by the Belle Collaboration, decaying to {chi}{sub c1}{pi}{sup +} in the decays {bar B}{sup 0} {yields} {chi}{sub c1}K{sup -}{pi}{sup +} and B{sup +} {yields} {chi}{sub c1}K{sub S}{sup 0}{pi}{sup +} where {chi}{sub c1} {yields} J/{psi}{gamma}. The data were collected with the BABAR detector at the SLAC PEP-II asymmetric-energy e{sup +}e{sup -} collider operating at center-of-mass energy 10.58 GeV, and correspond t… more
Date: April 10, 2012
Creator: Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M. et al.
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Partner: UNT Libraries Government Documents Department
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Unitarity Constraints on Asymmetric Freeze-In

Description: This paper considers unitarity and CPT constraints on asymmetric freeze-in, the use of freeze-in to store baryon number in a dark sector. In this scenario, Sakharov's out of equilibrium condition is satisfied by placing the visible and hidden sectors at different temperatures while a net visible baryon number is produced by storing negative baryon number in a dark sector. It is shown that unitarity and CPT lead to unexpected cancellations. In particular, the transfer of baryon number cancels co… more
Date: August 15, 2011
Creator: Hook, Anson
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Partner: UNT Libraries Government Documents Department
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The One-Loop Six-Dimensional Hexagon Integral and its Relation to MHV Amplitudes in N=4 SYM

Description: We provide an analytic formula for the (rescaled) one-loop scalar hexagon integral {tilde {Phi}}{sub 6} with all external legs massless, in terms of classical polylogarithms. We show that this integral is closely connected to two integrals appearing in one- and two-loop amplitudes in planar N = 4 super-Yang-Mills theory, {Omega}{sup (1)} and {Omega}{sup (2)}. The derivative of {Omega}{sup (2)} with respect to one of the conformal invariants yields {tilde {Phi}}{sub 6}, while another first-order… more
Date: August 19, 2011
Creator: Dixon, Lance J.; Drummond, James M. & Henn, Johannes M.
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Partner: UNT Libraries Government Documents Department
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Observation of the Decay B- --> Ds(*) K- l- nubar

Description: We report the observation of the decay B{sup -} {yields} D{sub s}{sup (*)+} K{sup -}{ell}{sup -}{bar {nu}}{sub {ell}} based on 342 fb{sup -1} of data collected at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II e{sup +}e{sup -} storage rings at SLAC. A simultaneous fit to three D{sub s}{sup +} decay chains is performed to extract the signal yield from measurements of the squared missing mass in the B meson decay. We observe the decay B{sup -} {yields} D{sub s}{sup (*)+} K{sup … more
Date: August 12, 2011
Creator: del Amo Sanchez, P.; Lees, J. P.; Poireau, V.; Prencipe, E.; Tisserand, V.; /Annecy, LAPP et al.
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Partner: UNT Libraries Government Documents Department
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SLAC Cosmic Ray Telescope Facility

Description: SLAC does not have a test beam for the HEP detector development at present. We have therefore created a cosmic ray telescope (CRT) facility, which is presently being used to test the FDIRC prototype. We have used it in the past to debug this prototype with the original SLAC electronics before going to the ESA test beam. Presently, it is used to test a new waveform digitizing electronics developed by the University of Hawaii, and we are also planning to incorporate the new Orsay TDC/ADC electron… more
Date: February 15, 2010
Creator: Va'vra, J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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General Relativistic Magnetohydrodynamic Simulations of Magnetically Choked Accretion Flows around Black Holes

Description: Black hole (BH) accretion flows and jets are qualitatively affected by the presence of ordered magnetic fields. We study fully three-dimensional global general relativistic magnetohydrodynamic (MHD) simulations of radially extended and thick (height H to cylindrical radius R ratio of |H/R| {approx} 0.2-1) accretion flows around BHs with various dimensionless spins (a/M, with BH mass M) and with initially toroidally-dominated ({phi}-directed) and poloidally-dominated (R-z directed) magnetic fiel… more
Date: April 26, 2012
Creator: McKinney, Jonathan C.; Tchekhovskoy, Alexander & Blandford, Roger D.
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Partner: UNT Libraries Government Documents Department
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