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The SLAC Damped Detuned Structure: Concept and design

Description: The SLAC Damped Detuned Structure (DDS) is an accelerator structure designed to suppress the long range transverse wakefields which limit the performance of high current multibunch accelerators. We discuss the conceptual considerations which have led to its development and discuss the steps involved in arriving at a design.
Date: May 1, 1997
Creator: Kroll, N.M.
Partner: UNT Libraries Government Documents Department

Opportunistic or event-driven maintenance at the Stanford Linear Accelerator Center

Description: The Stanford Linear Accelerator Center (SLAC) uses a maintenance management philosophy that is best described as opportunistic or event-driven. Opportunistic maintenance can be defined as a systematic method of collecting, investigating, pre-planning, and publishing a set of proposed maintenance tasks and acting on them when there is an unscheduled failure or repair ``opportunity``. Opportunistic maintenance can be thought of as a modification of the run-to-fail maintenance management philosophy. This maintenance plan was adopted and developed to improve the overall availability of SLAC`s linear accelerator, beam delivery systems, and associated controls, power systems, and utilities. In the late 1980`s, as the technical complexity of the accelerator facility increased, variations on a conventional maintenance plan were used with mixed results. These variations typically included some type of regular periodic interruption to operations. The periodic shutdowns and unscheduled failures were additive and resulted in unsatisfactory availability. Maintenance issues are evaluated in a daily meeting that includes the accelerator managers, maintenance supervisors and managers, safety office personnel, program managers, and accelerator operators. Lists of pending maintenance tasks are made available to the general SLAC population by a World Wide Web site on a local internet. A conventional information system which pre-dates the WWW site is still being used to provide paper copies to groups that are not yet integrated into the WWW system. The local internet provides real time maintenance information, allowing people throughout the facility to track progress on tasks with essentially real-time status updates. With the introduction of opportunistic maintenance, the accelerator`s availability has been measurably better. This paper will discuss processes, rolls and responsibilities of key maintenance groups, and management tools developed to support opportunistic maintenance.
Date: March 1, 1997
Creator: Allen, C.W.; Anderson, S.; Erickson, R.; Linebarger, W.; Sheppard, J.C. & Stanek, M.
Partner: UNT Libraries Government Documents Department

Secondary Electron Yield Measurements of Fermilab?s Main Injector Vacuum Vessel

Description: We discuss the progress made on a new installation in Fermilab's Main Injector that will help investigate the electron cloud phenomenon by making direct measurements of the secondary electron yield (SEY) of samples irradiated in the accelerator. In the Project X upgrade the Main Injector will have its beam intensity increased by a factor of three compared to current operations. This may result in the beam being subject to instabilities from the electron cloud. Measured SEY values can be used to further constrain simulations and aid our extrapolation to Project X intensities. The SEY test-stand, developed in conjunction with Cornell and SLAC, is capable of measuring the SEY from samples using an incident electron beam when the samples are biased at different voltages. We present the design and manufacture of the test-stand and the results of initial laboratory tests on samples prior to installation.
Date: May 1, 2012
Creator: Scott, D.J.; Capista, D.; Duel, K.L.; Zwaska, R.M.; /Fermilab; Greenwald, S. et al.
Partner: UNT Libraries Government Documents Department

Simulation and Analysis of Microwave Transmission through an Electron Cloud, a Comparison of Results

Description: Simulation studies for transmission of microwaves through electron cloudes show good agreement with analytic results. The elctron cloud produces a shift in phase of the microwave. Experimental observation of this phenomena would lead to a useful diagnostic tool for acessing the local density of electron clouds in an accelerator. These experiments are being carried out at the CERN SPS and the PEP-II LER at SLAC and is proposed to be done at the Fermilab maininjector. In this study, a brief analysis of the phase shift is provided and the results are compared with that obtained from simulations.
Date: March 12, 2007
Creator: Sonnad, Kiran; Sonnad, Kiran; Furman, Miguel; Veitzer, Seth; Stoltz, Peter & Cary, John
Partner: UNT Libraries Government Documents Department

Preliminary Analysis and Simulation Results of Microwave Transmission Through an Electron Cloud

Description: The electromagnetic particle-in-cell (PIC) code VORPAL is being used to simulate the interaction of microwave radiation through an electron cloud. The results so far showgood agreement with theory for simple cases. The study has been motivated by previous experimental work on this problem at the CERN SPS [1], experiments at the PEP-II Low Energy Ring (LER) at SLAC [4], and proposed experiments at the Fermilab Main Injector (MI). With experimental observation of quantities such as amplitude, phase and spectrum of the output microwave radiation and with support from simulations for different cloud densities and applied magnetic fields, this technique can prove to be a useful probe for assessing the presence as well as the densityof electron clouds.
Date: January 12, 2007
Creator: Sonnad, Kiran; Sonnad, Kiran; Furman, Miguel; Veitzer, Seth; Stoltz, Peter & Cary, John
Partner: UNT Libraries Government Documents Department

SIMULATION AND ANALYSIS OF MICROWAVE TRANSMISSION THROUGH ANELECTRON CLOUD, A COMPARISON OF RESULTS

Description: Simulation studies for transmission of microwaves through electron clouds show good agreement with analytic results. The electron cloud produces a shift in phase of the microwave. Experimental observation of this phenomena would lead to a useful diagnostic tool for accessing the local density of electron clouds in an accelerator. These experiments are being carried out at the CERN SPS and the PEP-II LER at SLAC and is proposed to be done at the Fermilab main injector. In this study, a brief analysis of the phase shift is provided and the results are compared with that obtained from simulations.
Date: April 15, 2006
Creator: Sonnad, Kiran G.; Furman, Miguel; Veitzer, Seth A. & Cary, John
Partner: UNT Libraries Government Documents Department

Using The SLAC Two-Mile Accelerator for Powering an FEL

Description: A parameter survey is made, employing the recently developed 2D formalism for an FEL, of the characteristics of an FEL using the SLAC accelerator. Attention is focused upon a wavelength of 40 {angstrom} (the water window) and 1 {angstrom} case is also presented. They consider employing the SLAC linac with its present operating parameters and with improved parameters such as would be supplied by a new photo-cathode injector. They find that improved parameters are necessary, but that the parameters presently achieved with present-day photo-cathode guns are adequate to reach the water window.
Date: June 29, 2012
Creator: Barletta, W.A.; /LLNL, Livermore; Sessler, A.M.; /LBL, Berkeley; Yu, L.H. & /Brookhaven
Partner: UNT Libraries Government Documents Department

Prompt Bunch by Bunch Synchrotron Oscillation Detection via a Fast Phase Measurement

Description: An electronic system is presented which detects synchrotron oscillations of individual bunches with 4 ns separation. The system design and performance are motivated by the requirements of the proposed B Factory facility at SLAC. Laboratory results are presented which show that the prototype is capable of measuring individual bunch phases with better than 0.5 degree resolution at the 476 MHz RF frequency.
Date: May 1, 1991
Creator: Briggs, D.; Corredoura, P.; Fox, J.D.; Giousmousis, A.; Hosseini, W.; Klaisner, L. et al.
Partner: UNT Libraries Government Documents Department

APIARY B-Factory Separation Scheme

Description: A magnetic beam-separation scheme for an asymmetric-energy B Factory based on the SLAC electron-positron collider PEP is described that has the following properties: the beams collide head-on and are separated magnetically with sufficient clearance at the parasitic crossing points and at the septum, the magnets have large beam-stay-clear apertures, synchrotron radiation produces low detector backgrounds and acceptable heat loads, and the peak {beta}-function values and contributions to the chromaticities in the IR quadrupoles are moderate.
Date: May 3, 1991
Creator: Garren, A. & Sullivan, M.
Partner: UNT Libraries Government Documents Department

Locking Lasers to RF in an Ultra Fast FEL

Description: Using a novel, phase-stabilized RF-over-fiber scheme, they transmit 3GHz over 300m with 27fs RMS error in 250kHz bandwidth over 12 hours, and phase lock a laser to enable ultrafast pump-probe experiments. Free-electron lasers (FELs) are capable of producing short-duration (< 10fs), high-energy X-ray pulses for a range of scientific applications. The recently activated Linac Coherent Light Source (LCLS) FEL facility at SLAC will support experiments which require synchronized light pulses for pump-probe schemes. They developed and operated a fiber optic RF transmission system to synchronize lasers to the emitted X-ray pulses, which was used to enable the first pump-probe experiments at the LCLS.
Date: January 2, 2010
Creator: Wilcox, R.; Huang, G.; Doolittle, L.; White, W.; Frisch, J. & Coffee, R.
Partner: UNT Libraries Government Documents Department

Higher Order Modes Damping Analysis for the SPX Deflecting Cavity Cryomodule

Description: A single-cell superconducting deflecting cavity operating at 2.812 GHz has been proposed and designed for the Short Pulse X-ray (SPX) project for the Advanced Photon Source upgrade. A cryomodule of 4 such cavities will be needed to produce the required 2-MV deflecting voltage. Each deflecting cavity is equipped with one fundamental power coupler (FPC), one lower order mode (LOM) coupler, and two higher order mode (HOM) couplers to achieve the stringent damping requirements for the unwanted modes. The damping of the HOM/LOM modes below the beampipe cutoff has been analyzed in the single cavity geometry and shown to meet the design requirements. The HOMs above beam pipe cutoff in the 4-cavity cyromodule, however, may result in cross coupling which may affect the HOM damping and potentially trapped modes between the cavities which could produce RF heating to the beamline bellows and even be detrimental to the beam. We have evaluated the HOM damping and trapped modes in the 4-cavity cryomodule using the parallel finite element EM code ACE3P developed at SLAC. We will present the results of the cryomodule analysis in this paper.
Date: July 1, 2012
Creator: Xiao, L.; Li, Z.; Ng, C.-K.; Nassiri, A.; Waldschmidt, G.; Wu, G. et al.
Partner: UNT Libraries Government Documents Department

Progress on the high-current 704 MHz superconducting RF cavity at BNL

Description: The 704 MHz high current superconducting cavity has been designed with consideration of both performance of fundamental mode and damping of higher order modes. A copper prototype cavity was fabricated by AES and delivered to BNL. RF measurements were carried out on this prototype cavity, including fundamental pass-band and HOM spectrum measurements, HOM studies using bead-pull setup, prototyping of antenna-type HOM couplers. The measurements show that the cavity has very good damping for the higher-order modes, which was one of the main goals for the high current cavity design. 3D cavity models were simulated with Omega3P code developed by SLAC to compare with the measurements. The paper describes the cavity design, RF measurement setups and results for the copper prototype. The progress with the niobium cavity fabrication will also be described.
Date: May 20, 2012
Creator: W., Xu; Astefanous, C.; Belomestnykh, S.; Ben-Zvi, I. & al, et
Partner: UNT Libraries Government Documents Department

A Search for B^{+} \to \ell^{+} \nu_{\ell} Recoiling Against B^{-} \to D^{(*)0}\ell^{-}\bar{\nu}X

Description: We present a search for the decay B{sup +} {yields} {ell}{sup +} {nu}{sub {ell}} ({ell} = {tau}, {mu}, or e) in (458.9 {+-} 5.1) x 10{sup 6} {Upsilon}(4S) decays recorded with the BABAR detector at the SLAC PEP-IIB-Factory. A sample of events with one reconstructed exclusive semi-leptonic B decay (B{sup -} {yields} D{sup 0} {ell}{sup -}{bar {nu}}X) is selected, and in the recoil a search for B{sup +} {yields} {ell}{sup +}{nu}{sub {ell}} signal is performed. The {tau} is identified in the following channels: {tau}{sup +} {yields} e{sup +}{nu}{sub e}{nu}{sub {tau}}, {tau}{sup +} {yields} {mu}{sup +}{nu}{sub {mu}}{nu}{sub {tau}}, {tau}{sup +} {yields} {pi}{sup +}{nu}{sub {tau}}, and {tau}{sup +} {yields} {pi}{sup +}{pi}{sup 0}{nu}{sub {tau}}. The analysis strategy and the statistical procedure is set up for branching fraction extraction or upper limit determination. We determine from the dataset a preliminary measurement of {Beta}(B{sup +} {yields} {tau}{sup +}{nu}{sub {tau}}) = (1.8 {+-} 0.8 {+-} 0.1) x 10{sup -4}, which excludes zero at 2.4{sigma}, and f{sub B} = 230 {+-} 57 MeV. Combination with the hadronically tagged measurement yields {Beta}(B{sup +} {yields} e{sup +}{nu}{sub e}) = (1.8 {+-} 0.6) x 10{sup -4}. We also set preliminary limits on the branching fractions at {Beta}(B{sup +} {yields} e{sup +}{nu}{sub e}) < 7.7 x 10{sup -6} (90% C.L.), {Beta}(B{sup +} {yields} {mu}{sup +}{nu}{sub {mu}}) < 11 x 10{sup -6} (90% C.L.), and {Beta}(B{sup +} {yields} {tau}{sup +}{nu}{sub {tau}}) < 3.2 x 10{sup -4} (90% C.L.).
Date: April 17, 2009
Creator: Aubert, Bernard; Bona, M.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Prencipe, E. et al.
Partner: UNT Libraries Government Documents Department

Injection Related Background due to the Transverse Feedback

Description: The background in the BaBar detector is especially high during injection, when most components are actually having reduced voltages. The situation is worse for the beam in High Energy Ring (HER) when the LER beam is present. It was found that the transverse feedback system plays an important role when stacking more charge on top of existing bunches. Lowering the feedback gain helped and it was realized later that the best scenario would be to gate off the feedback for only the one bunch, which got additional charge injected into it. The explanation is that the blown-up, but centered, original HER bunch plus the small injected off-axis bunch (each with half the charge) would stay in the ring if not touched, but the feedback system sees half the offset and wants to correct it, therefore disturbing and scraping the blown-up part.
Date: March 18, 2008
Creator: Decker, F.J.; Akre, R.; Fisher, A.; Iverson, R.; Weaver, M. & /SLAC
Partner: UNT Libraries Government Documents Department

Interaction-Point Phase-Space Characterization using Single-Beam and Luminous-Region Measurements at PEP-II

Description: We present an extensive experimental characterization of the e{sup {+-}} phase space at the interaction point of the SLAC PEP-II B-Factory, that combines a detailed mapping of luminous-region observables using the BABAR detector, with stored-beam measurements by accelerator techniques.
Date: September 9, 2008
Creator: Kozanecki, W; /Saclay; Bevan, A.J.; /Queen Mary, U. of London; Viaud, B.F.; U., /Montreal et al.
Partner: UNT Libraries Government Documents Department

Evidence for B- to rho0rho0 Decay and Implications for the CKM Angle alpha

Description: The authors search for the decays B{sup 0} {yields} {rho}{sup 0}{rho}{sup 0}, B{sup 0} {yields} {rho}{sup 0} f{sub 0}(980), and B{sup 0} {yields} f{sub 0}(980) f{sub 0}(980) in a sample of about 384 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at SLAC. They find evidence for B{sup 0} {yields} {rho}{sup 0}{rho}{sup 0} with 3.5{sigma} significance and measure the branching fraction {Beta} = (1.07 {+-} 0.33 {+-} 0.19) x 10{sup -6} and longitudinal polarization fraction f{sub L} = 0.87 {+-} 0.13 {+-} 0.04, where the first uncertainty is statistical, and the second is systematic. The uncertainty on the CKM unitarity angle {alpha} due to penguin contributions in B {yields} {rho}{rho} decays is 18{sup o} at the 1{sigma} level. They also set upper limits on the B{sup 0} {yields} {rho}{sup 0} f{sub 0}(980) and B{sup 0} {yields} f{sub 0}(980)f{sub 0}(980) decay rates.
Date: January 3, 2007
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department

The 2mrad horizontal crossing angle IR layout for a TeV ILC

Description: The current status of the 2mrad crossing angle layout for the ILC is reviewed. The scheme developed in the UK and France is described and the performance discussed for a TeV machine. Secondly, the scheme developed at SLAC and BNL is then studied and modified for a TeV machine. We find that both schemes can handle the higher energy beam with modifications, and share many common features.
Date: July 27, 2005
Creator: Appleby, R.; Angal-Kalinin, D.; /Daresbury; Bambade, P.; Mouton, B.; /Orsay, LAL et al.
Partner: UNT Libraries Government Documents Department

Network Upgrade for the SLC: PEP II Network

Description: The PEP-II control system required a new network to support the system functions. This network, called CTLnet, is an FDDI/Ethernet based network using only TCP/IP protocols. An upgrade of the SLC Control System micro communications to use TCP/IP and SLCNET would allow all PEP-II control system nodes to use TCP/IP. CTLnet is private and separate from the SLAC public network. Access to nodes and control system functions is provided by multi-homed application servers with connections to both the private CTLnet and the SLAC public network. Monitoring and diagnostics are provided using a dedicated system. Future plans and current status information is included.
Date: September 9, 2011
Creator: Crane, M.; Call, M.; Clark, S.; Coffman, F.; Himel, T.; Lahey, T. et al.
Partner: UNT Libraries Government Documents Department

Observation of Y(3940) to J/psi omega in B to J/psi omega K at BABAR

Description: The authors report the results of a study of the decays B{sup +} {yields} J/{psi}{omega}K{sup +} and B{sup 0} {yields} J/{psi}{omega}K{sub S}{sup 0} using 383 million B{bar B} events from {Upsilon}(4S) decays with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} storage rings. They observe evidence for Y(3940) {yields} J/{psi}{omega} with product branching fractions {Beta}(B{sup +} {yields} Y K{sup +}, Y {yields} J/{psi}{omega}) = (4.9 {+-} 1.0(stat) {+-} 0.5(syst)) x 10{sup -5} and {Beta}(B{sup 0} {yields} Y K{sup 0}, Y {yields} J/{psi}{omega}) = (1.5{sub -1.2}{sup +1.4}(stat){sub -0.2}{sup +0.2}(syst)) x 10{sup -5}. The measured mass and width are M(Y) = (3914.6{sub -3.4}{sup +3.8}(stat){sub -1.9}{sup +1.9}(syst)) MeV/c{sup 2} and {Lambda}(Y) = (33{sub -8}{sup +12}(stat){sub -5}{sup +5}(syst)) MeV, respectively.
Date: December 4, 2007
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department

Measurement of D^0-\bar{D^0} Mixing From a Time-Dependent Amplitude Analysis of D^0\ -> K^+\pi^-\pi0 Decays

Description: The authors present evidence of D{sup 0}-{bar D}{sup 0} mixing using a time-dependent amplitude analysis of the decay D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} in a data sample of 384 fb{sup -1} collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider at SLAC. Assuming CP conservation, they measure the mixing parameters x{prime}{sub K{pi}{pi}{sup 0}} = [2.61{sub -0.68}{sup +0.57}(stat.) {+-} 0.39(syst.)]%, y{prime}{sub K{pi}{pi}{sup 0}} = [-0.06{sub -0.64}{sup +0.55}(stat.) {+-} 0.34(syst.)]%. The confidence level for the data to be consistent with the no-mixing hypothesis is 0.1%, including systematic uncertainties. This result is inconsistent with the no-mixing hypothesis with a significance of 3.2 standard deviations. They find no evidence of CP violation in mixing.
Date: August 4, 2008
Creator: Aubert, Bernard; Bona, M.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Prencipe, E. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the B+- to rho pi0 Branching Fraction and Direct CP Asymmetry

Description: The authors present improved measurements of the branching fraction and CP asymmetry for the process B{sup {+-}} {yields} {rho}{sup {+-}}{pi}{sup 0}. The data sample corresponding to 211 fb{sup -1} comprises 232 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. The yield and CP asymmetry are measured using an extended maximum likelihood fitting method. The branching fraction and Cp asymmetry are found to be {Beta}(B{sup {+-}} {yields} {rho}{sup {+-}}{pi}{sup 0}) = [10.2 {+-} 1.4(stat) {+-} 0.9(syst)] x 10{sup -6} and {Alpha}{sub CP}(B{sup {+-}} {yields} {rho}{sup {+-}}{pi}{sup 0}) = -0.01 {+-} 0.13(stat) {+-} 0.02(syst).
Date: January 25, 2007
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department

Measurement of the Time-dependent CP Asymmetry inB to D(*)_CP h0 Decays

Description: The authors report a measurement of the time-dependent CP-asymmetry parameters S and C in color-suppressed B{sup 0} {yields} D{sup (*)0}h{sup 0} decays, where h{sup 0} is a {pi}{sup 0}, {eta}, or {omega} meson, and the D{sup 0} decays to one of the CP eigenstates K{sup +}K{sup -}, K{sub S}{sup 0}{pi}{sup 0}, or K{sub S}{sup 0}{omega}. The data sample consists of 383 x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II asymmetric-energy B-factory at SLAC. The results are S = -0.56 {+-} 0.23 {+-} 0.05 and C = -0.23 {+-} 0.16 {+-} 0.04, where the first error is statistical and the second is systematic.
Date: March 14, 2007
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department

Measurement of the Branching Fraction, Polarization, and CP Asymmetries in B0->rho0rho0 Decay, and Implications for the CKM Angle alpha

Description: We study B{sup 0} {yields} {rho}{sup 0}{rho}{sup 0} decays in a sample of 465 x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} events collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider located at the Stanford Linear Accelerator Center (SLAC). We measure the branching fraction {Beta} = (0.92 {+-} 0.32 {+-} 0.14) x 10{sup -6} and longitudinal polarization fraction f{sub L} = 0.75{sub -0.14}{sup +0.11} {+-} 0.04, where the first uncertainty is statistical and the second is systematic. The evidence for the B{sup 0} {yields} {rho}{sup 0}{rho}{sup 0} signal has a significance of 3.1 standard deviations, including systematic uncertainties. We investigate the proper-time dependence of the longitudinal component in the decay and measure the CP-violating coefficients S{sub L}{sup 00} = (0.3 {+-} 0.7 {+-} 0.2) and C{sub L}{sup 00} = (0.2 {+-} 0.8 {+-} 0.3). They study the implication of these results for the unitarity triangle angle {alpha}.
Date: September 10, 2008
Creator: Aubert, B
Partner: UNT Libraries Government Documents Department