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Status of the PEP-II B-factory high energy ring

Description: The 9 GeV High Energy Ring (HER) of the PEP-II B Factory is an electron storage ring under construction at SLAC. Significant progress has been made in the last year on all systems. As of mid 1996, all 192 dipoles have been installed, with installation of the quadrupoles underway. The vacuum system, for design currents up to 3 A average, is in production using a recently commissioned e-beam welder. Beam instrumentation systems are being fabricated. The interaction region will bring the HER beam into collision with the 3 GeV beam of the Low Energy Ring; design of this section of the HER is in an advanced stage. 8 refs., 3 figs., 1 tab.
Date: January 1, 1996
Creator: Wienands, U.; Reuter, E.; Bellomo, P.; Daly, E.; Fisher, A.; Gracia, J. et al.
Partner: UNT Libraries Government Documents Department

Low energy ring lattice of the PEP-II asymmetric B-Factory

Description: Developing a lattice that contains a very low beta value at the interaction point (IP) and has adequate dynamic aperture is one of the major challenges in designing the PEP-II asymmetric B-factory. For the Low Energy Ring (LER) the authors have studied several different chromatic correction schemes since the conceptual design report (CDR). Based on these studies, a hybrid solution with local and semi-local chromatic sextupoles has been selected as the new baseline lattice to replace the local scheme in the CDR. The new design simplifies the interaction region (IR) and reduces the number of sextupoles in the arcs. Arc sextupoles are paired at {pi} phase difference and are not interleaved. In this paper the authors describe the baseline lattice with the emphasis on the lattice changes made since the CDR.
Date: June 1, 1995
Creator: Cai, Y.; Donald, M.; Helm, R.; Irwin, J.; Nosochkov, Y.; Ritson, D.M. et al.
Partner: UNT Libraries Government Documents Department

Low level RF system design for the PEP-II B factory

Description: Heavy beam loading in PEP-II has driven the design of the low level RF system to contain feedback loops similar to those used in proton rings. The RF feedback loops control longitudinal coupled-bunch instabilities caused by the beam interaction with the accelerating mode of the RF cavities by reducing the cavity impedance observed by the beam. The RF system employs a modular design housed in a VXI environment and uses the EPICS control system. Modem control system design and signal processing is used throughout the system. This paper describes the RF system topology and the signal processing used to fulfill the system requirements.
Date: October 1, 1995
Creator: Corredoura, P.; Claus, R. & Sapozhnikov, L.
Partner: UNT Libraries Government Documents Department

The PEP II injection kicker system

Description: PEP II or the B Factory consists of two asymmetric storage rings. The injection energy for electrons is 9 GeV, while that for positrons is 3.1 GeV. The bend angle into the high energy ring (HER) is 0.35 m-rad, and the angle into the low energy ring (LER) is 0.575 m-rad. The magnetic length for the HER kicker is 0.85 m, and 0.55 m for the LER kicker. The field produced by the magnet is therefore 123.5 G for the HER, and 132 G for the LER. Each ring has a kicker magnet upstream of the injection line which is used to distort the orbit of the stored beam. An identical magnet downstream of the injection line is used to restore the orbit of the stored beam and inject the incoming beam. The two magnets are driven in parallel by the modulator. The apeture of the magnets is 3.86x3.46 cm (HxV). Therefore the current required to drive the HER is 863 A, while for the LER it is 756 A. The inductance of the magnet is approximately 1.4 uH/m. The current pulse is a critically damped sinusoid with a rise time of less than 300 ns. A kicker system has been designed which can be used for injection of both beams by varying the charge of voltage. The modulator uses a conjugate circuit to match the impedance of the magnet, and coupling to the beam chamber.
Date: July 1, 1997
Creator: Pappas, G.C.; Donaldson, A.R. & Williams, D.
Partner: UNT Libraries Government Documents Department

Development of a movable plunger tuner for the high-power RF cavity for the PEP-II B-factory

Description: A 10 cm diameter by 5 cm travel plunger tuner was developed for the PEP-II RF copper cavity system. The single cell cavity including the tuner is designed to operate up to 150 kW of dissipated RF power are specially placed 8.5 cm away from the inside wall of the cavity to avoid fundamental and higher order mode resonances. The spring fingers are made of dispersion-strengthened copper to accommodate relatively high heating. The design, alignment, testing and performance of the tuner is described.
Date: May 1, 1997
Creator: Schwarz, H.D.; Fant, K. & Judkins, J.G.
Partner: UNT Libraries Government Documents Department

Results from a prototype permanent magnet dipole-quadrupole hybrid for the PEP-II B-factory

Description: We describe the construction of a prototype hybrid permanent magnet dipole and quadrupole. The magnet consists of two concentric rings of Sm{sub 2}Co{sub 17} magnetic material 5 cm in length. The outer ring is made of 16 uniformly magnetized blocks assembled as a Halbach dipole and the inner ring has 32 blocks oriented in a similar fashion so as to generate a quadrupole field. The resultant superimposed field is an offset quadrupole field which allows us to center the field on the high-energy beam in the interaction region of the PEP-II B-factory. The dipole blocks are glued to the inside surface of an outer support collar and the quadrupole blocks are held in a fixture that allows radial adjustment of the blocks prior to potting the entire assembly with epoxy. An extensive computer model of the magnet has been made and from this model we developed a tuning algorithm that allowed us to greatly reduce the n=3 17 harmonics of the magnet.
Date: June 1, 1997
Creator: Sullivan, M.; Bowden, G. & Ecklund, S.
Partner: UNT Libraries Government Documents Department

Numerical modeling of beam-environment interactions in the PEP-II B-Factory

Description: The PEP-II B-Factory is designed to operate at high currents with many bunches (1658) to achieve the luminosity required for physics studies. Interactions of a beam with its environment in a storage ring raise various issues of concern for accelerator physics, mechanical design and device performance. First, for accelerator physics, wakefields generated by interactions of a beam with beamline components, if not properly controlled, will drive single-bunch and coupled-bunch instabilities. The total broad-band impedance of the ring cannot exceed a budget limited by single-bunch effects. The growth rate of a coupled-bunch mode contributed from narrow-band impedance should be smaller than the damping rate due to synchrotron radiation; otherwise, suppression by feedback control will be necessary. Second, the energy loss by a beam at a beamline component in the form of higher-order-mode (HOM) power leads to additional heating on the component, and to TE mode radiation through openings on vacuum chamber walls. Last, calculations of transfer and beam impedances of pickup and kicker devices are essential for improving their performance and for identifying trapped modes. To address these issues quantitatively requires numerical simulations of each beamline component which include the realistic geometry and the relevant physics involved in the particular beam-environment interactions.
Date: November 1, 1996
Creator: Ng, C.K.; Ko, K.; Li, Z. & Lin, X.E.
Partner: UNT Libraries Government Documents Department

Design and performance of the PEP-II B-Factory HER QDA quadrupole magnet

Description: The High Energy Ring (HER) in Stanford Linear Accelerator Center`s PEP-II B-Factory employs two high field quality quadrupole magnets, labeled QD4, for final horizontal beam de-focusing at a gradient of {approximately}75.65 kG/m. An asymmetric, septum quadrupole design is required for QD4. Due to space constraints, the magnetic field is shaped with both the iron and the coil. Each coil has fifteen conductors. A perturbation analysis was performed using the Poisson code in order to locate the ideal position of the individual conductors. Manufacturing and assembly tolerances of +/- 0.5 mm of each conductor were required to maintain an integrated field quality of multipole content of b{sub n}/b{sub 2}{le}0.0001 for n=3-15 at a radius of 59.0 mm. The steel core of the magnet is 1.425 m long and is comprised of 1.5 mm thick laminations. A cut out in the steel core is required to allow the Low Energy Ring beam to pass through the side of the magnet. A double shield is in place to allow the LER beam to remain field free. The pole tip shape is a simple hyperbola without any end contours. The design and performance of the QD4 magnet is presented.
Date: October 1, 1997
Creator: Swan, J.; Behne, D.; Kendall, C.M.; Yamamoto, R.; Yokota, T. & Tanabe, J.
Partner: UNT Libraries Government Documents Department

Calibration of the beam-position monitor system for the SLAC PEP-II B factory

Description: The Beam-Position Monitors (BPM) for the PEP-II B Factory consist of four 1.5-cm diameter button style pickups mounted on the diagonals of the quadrupole vacuum chambers. Before installation of the vacuum chambers in the quadrupole assemblies, the electrical center of the BPMs is measured with respect to the mechanical center in a calibration test stand. In this paper the calibration test stand is described and the precision and accuracy of the calibrations are presented. After installation of the quadrupole assemblies in the PEP-II tunnel, the passive attenuation for each channel of the system is measured to preserve the accuracy of the calibration. Finally, the active electronics includes an onboard calibrator. Results for these portions of the calibration are presented.
Date: June 1, 1997
Creator: Johnson, R.; Smith, S. & Kurita, N.
Partner: UNT Libraries Government Documents Department

Design and alaysis of the PEP-II B-Factory HER QF5 quadrupole magnet

Description: The High Energy Ring (HER) in Stanford Linear Accelerator Center`s PEP-II B-Factory employs two high field quality quadrupole magnets, labeled QF5, located in the Interaction Region (IR) symmetrically about the Interaction Point (IP), for final horizontal beam focusing. An asymmetric, septum, Collins quadrupole design is required for QF5 as a result of space constraints within the IR. Water cooled square hollow copper conductor is used in a two coil per pole configuration to develop the 61.7 kG/m and 82.2 kG/m gradients required for the HER 9 GeV and 12 GeV energy levels respectively. A 1.45 m long laminated iron core constructed in two halves with a 160 mm diameter aperture and pole tip shims shape the quadruple field. The QF5 field quality requirements include a multipole content of b{sub n}/b{sub 2} {le}1 {times} 10{sup -4} for n = 3-15 at a radius of 78.1 mm. The QF5 quadrupole mechanical and magnetic design and analysis are presented.
Date: October 11, 1997
Creator: Kendall, C.M.; Harvey, A.; Swan, J.; Yamamoto, R.; Yokota, T.; Tanabe, J. et al.
Partner: UNT Libraries Government Documents Department

Impedance study for the PEP-II B-factory

Description: The paper summarizes results of the impedance studies of the components of the B-factory. The prime goal of this activity was to support the design of the vacuum chamber and, at the same time, to get a reasonable model of the machine impedance, which can be used later for detail studies of collective effects.
Date: June 1, 1995
Creator: Heifets, S.; Daly, C.E. & Ko, K.
Partner: UNT Libraries Government Documents Department

1.2 MW klystron for Asymmetric Storage Ring B Factory

Description: A cw klystron operating at 476 MHz has been developed jointly by SLAC and Varian Associates. The unique set of characteristics of this tube were strongly guided by requirements of the fast feedback necessary to prevent oscillations of the storage ring beams caused by the detuned accelerating cavity. This requires a combination of bandwidth and short group delay within the klystron. The RF feedback stabilization scheme also requires amplitude modulation making it necessary to operate the klystron about 10% below saturation. Performance specifications and initial operating results are presented.
Date: March 1995
Creator: Fowkes, W. R.; Caryotakis, G. & Doyle, E.
Partner: UNT Libraries Government Documents Department

High-power RF window and coupler development for the PEP-II B Factory

Description: We describe the fabrication and testing of the RF windows designed to transmit power to the PEP-II 476 MHz cavities. Design choices to maximize the reliability of the window are discussed. Fabrication technologies for the window are described and finite-element analysis of the assembly process is presented. Conditioning and high-power testing of the window are discussed. Design of the coupler assembly including the integration of the window and other components is reported.
Date: May 1, 1995
Creator: Neubauer, M.; Fant, K.; Hodgson, J.; Judkins, J.; Schwarz, H. & Rimmer, R.A.
Partner: UNT Libraries Government Documents Department

Status of the SLAC/LBL/LLNL B-factory and the BABAR detector

Description: After a brief introduction on the physics reach of the SLAC/LBL/LLNL Asymmetric B-Factory, the author describes the status of the accelerator and the detector as of the end of 1994. At this time, essentially all major decisions have been made, including the choice of particle identification for the detector. The author concludes this report with the description of the schedule for the construction of both accelerator and detector.
Date: October 1, 1994
Creator: Oddone, P.
Partner: UNT Libraries Government Documents Department

Inclusive Hadronic Results at BaBar: ISR and Pentaquark Searches

Description: We present recent measurements of hadronic cross-sections from the BaBar experiment and report preliminary results on searches for pentaquark states. Studies of hadronic cross-sections using initial-state radiation offer promising prospects at BaBar. Many exclusive channels have already been measured, and more are in progress. A fully inclusive analysis should also offer a precise measurement of {Delta}{alpha}{sub QED}{sup Had}. Searches for pentaquark states have so far been negative, but they have served to highlight the potential for the study of charmed and non-charmed baryons at high-luminosity e{sup +}e{sup -} colliders.
Date: August 15, 2005
Creator: Berger, Nicolas
Partner: UNT Libraries Government Documents Department

Transverse multibunch modes for non-rigid bunches, including mode coupling

Description: A method for computing transverse multibunch growth rates and frequency shifts in rings, which has been described previously, is applied to the PEP-II B factory. The method allows multibunch modes with different internal-bunch oscillation modes to couple to one another, similar to single-bunch mode coupling. Including coupling between the multibunch modes gives effects similar to those seen in single-bunch mode coupling. These effects occur at currents that are lower than the single-bunch mode coupling threshold.
Date: August 1, 1995
Creator: Bert, J.S. & Ruth, R.D.
Partner: UNT Libraries Government Documents Department

Theoretical predictions for exotic hadrons

Description: In this contribution the authors discuss current theoretical expectations for the properties of light meson exotica, which are meson resonances outside the q{anti q} quark model. Specifically they discuss expectations for gluonic hadrons (glueballs and hybrids) and multiquark systems (molecules). Experimental candidates for these states are summarized, and the relevance of a TCF to these studies is stressed.
Date: December 1996
Creator: Barnes, T.
Partner: UNT Libraries Government Documents Department

B-factory interaction region design

Description: High luminosity B-factories generally high current (1-3 A) e+e- storage ring accelerators that operate at a center-of-mass energy equal to the mass of the Upsilon (4S) resonance (10.58 GeV). The high beam currents are achieved by storing a large number of bunches (several hundred to several thousand) into each beam. Two designs, the ones located at SLAC and KEK, also have asymmetric beam energies. This imparts a boost to the nearly stationary B mesons formed from the decay of the 4S resonance and allows precision vertex tracking detectors to look for a difference between the decay profiles of the matter and anti-matter B mesons, thereby observing a violation of CP. Bringing the stored beams into collision is one of the major challenges of any B-factory design. In order to achieve high luminosity the beams must be tightly focused. This pushes the final focusing elements close enough to the interaction point to be inside the solenoidal field of the physics detector. In addition, beam-related detector backgrounds from synchrotron radiation and scattered beam particles must be kept below an acceptable level. The major B-factory designs at Cornell University, KEK, and SLAC have all addressed these problems in various ways that depend on specific accelerator design decisions. This paper discusses the accelerator parameters and detector constraints that influence an interaction region (IR) design, as well as how the various IR designs address the challenges posed by a high luminosity B-factory.
Date: June 1, 1997
Creator: Sullivan, M.
Partner: UNT Libraries Government Documents Department

A final-focus magnet for PEP-II

Description: A compact quadrupole magnet has been designed for the final-focus of the 3GeV {times} 9GeV PEP II B-factory collider being built at SLAC. The magnet system must fit within the particle detector, has no iron, and consists of four nested separately controlled magnets: a two-layer 11.95 T/m quadrupole; a horizontal dipole; a vertical dipole; and a 1.5T solenoid. The 1.1 m long magnet must produce a highly uniform quadrupole field in the 120 mm ID beam pipe. The cryostat is 140 mm ID. (warm), 314 mm OD, and approximately 1.5 m long. The very compact cryogenic suspension system using Ti alloy plates is designed to withstand large forces due to interaction between the field of the detector solenoid and the four nested magnets. Cryogenic services and magnet leads are provided through a single flexible transfer line approximately 4m long.
Date: October 17, 1994
Creator: Taylor, C.E.; Caspi, S. & Saho, N.
Partner: UNT Libraries Government Documents Department

Summary report of the impedance and instability subgroup

Description: This subgroup discussed several technical issues facing the BTCF (Beijing tau-charm factory). Most of these are R and D issues to be performed before a construction start. The two uncertainties facing the B-factories and the BTCF alike, namely the transient ion instability and the photo-electron instability are much weaker in the BTCF. Another uncertainty concerns the monochromator scheme, for which a round of parameters optimization is called for. The R and D issues can be collected into a long list. These discussions are by no means exhaustive, but are listed below as a summary of this report: (1) impedance policing is to be established; (2) single bunch instability is marginally acceptable; (3) beam-beam effects is to be considered together with microwave instability to optimize the overall design; (4) microwave power is a new issue which needs attention; (5) trapped modes need attention; (6) aluminum antechamber vacuum chamber design is recommended; (7) electrostatic separators need to be designed to minimize the microwave power generation; (8) dust particles need attention.
Date: February 1, 1996
Creator: Chao, A. W.; Fang, S. X. & Guo, Z. Y.
Partner: UNT Libraries Government Documents Department

Detector solenoid compensation in the PEP-II B-Factory

Description: The PEP-II experimental detector includes a strong 1.5 T solenoid field in the interaction region (IR). With the fringe fields, the solenoid extends over a range of 6 m. Additional complications are that (1) it is displaced longitudinally from the interaction point (IP) by about 40 cm, (2) neither beam is parallel to the solenoid axis, and (3) the solenoid overlaps a dipole and a quadrupole on either side of the IP. In each half IR the correction system includes a set of skew quadrupoles, dipole correctors and normal quadrupoles to independently compensate the coupling, orbit perturbation, dispersion and focusing effect produced by the solenoid. The correction schemes for the Low Energy Ring (LER) and for the High Energy Ring (HER) are described, and the impact on the dynamic aperture is evaluated.
Date: June 1, 1995
Creator: Nosochkov, Y.; Cai, Y.; Irwin, J.; Sullivan, M. & Forest, E.
Partner: UNT Libraries Government Documents Department