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betatron

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MOPC092 Single Particle Multi-turn Dynamics During Crystal Collimation simulation, proton, collimation, scattering 277
 
  • G. Robert-Demolaize, K. A. Drees, S. Peggs
    BNL, Upton, Long Island, New York
  • R. P. Fliller
    Fermilab, Batavia, Illinois
  As the increase in luminosity remains a high-profile issue for current and future accelerator projects, protecting superconducting magnets from beam induced quenches implies using state-of-the-art halo cleaning devices given the required beam intensities. In CERN's LHC case, a multi-stage collimation system is being set up so as to provide a halo cleaning efficiency up to 99.995%. In order to improve this system even further, US-LARP funded studies have started to appreciate the use of a silicon-based crystal as a primary target for the halo particles. Dedicated experiments have recently been performed in an SPS extraction line for a bent silicon crystal in case of single-pass particles. This article compares the published results of this experiment with simulations using established tracking codes. The goal is to better describe the main physics mechanisms involved in the beam-crystal interaction. A simple algorithm is then introduced to allow for fast tracking of the effect of a crystal on a high energy proton beam over many turns. The general feasibility of single particle, multi-turn crystal experiments at the SPS (CERN) and Tevatron (Fermilab) and their outline are discussed.  
 
MOPC112 HESR Linear Lattice Design target, lattice, electron, antiproton 325
 
  • B. Lorentz, A. Lehrach, R. Maier, D. Prasuhn, H. Stockhorst, R. Tölle
    FZJ, Jülich
  The High Energy Storage Ring (HESR) is a part of the future Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt. The ring is used for hadron physics experiments with a pellet target and the PANDA detector, and will supply antiprotons of momenta from 1.5 GeV/c to 15 GeV/c. The ring will consist of two 180 degree bending sections (arcs) of 157 m length, each, and two 132 m long straight sections. In one of the straight sections the PANDA experiment will be installed, the other straight section will be equipped with a High Energy Electron Cooler. A longitudinal and transverse stochastic cooling system will be used in the momentum range from 3.8 GeV/c to 15 GeV/c. Adjustment of beta functions at target and electron cooler, to achieve highest beam lifetimes, most efficient cooling and highest luminosities are the main design requirements. The basic design consists of FODO cell structures in the arcs. The arc quadrupole magnets are grouped into four families, to allow a flexible adjustment of transition energy, horizontal and vertical tune, and dispersion. The details of the linear lattice and operation modes will be discussed in this presentation.  
 
MOPC117 Hybrid Snake Spin Resonance in RHIC resonance, lattice, sextupole, coupling 337
 
  • V. H. Ranjbar, D. T. Abell
    Tech-X, Boulder, Colorado
  • M. Bai, A. U. Luccio
    BNL, Upton, Long Island, New York
  Simulations reveal a potential polarization loss during low beta squeeze. This depolarization appears to be driven by a spin tune modulation caused by spin precession through the strong low beta quads due to the vertical fields. The modulation of the spin tune introduces an additional snake resonance condition at νs0 ± n νx - νz l = integer which while the same numerology as the well known sextupole resonance, can operate in the absence of sextupole elements.  
 
MOPC129 Lattice without Transition Energy for the Future PS2 dipole, lattice, quadrupole, sextupole 370
 
  • D. Trbojevic, S. Peggs
    BNL, Upton, Long Island, New York
  • Y. Papaphilippou, R. de Maria
    CERN, Geneva
  The Large Hadron Collider (LHC) will be commissioned very soon. Improvements of the LHC injection complex are considered in the upgrade possibilities. In the injection complex it is considered that the aging Proton Synchrotron (PS) would be replaced with a new fast cycling synchrotron PS2. The energy range would be from 5-50 GeV with a repetition rate of 0.3 Hz. This is a report on the PS2 lattice design using the Flexible Momentum Compaction (FMC) method*. The design is trying to fulfill many requirements: high compaction factor, racetrack shape with two long zero dispersion straight sections, circumference fixed to a value of 1346 meters (CPS2=15/77 CPS), using normal conducting magnets and avoiding the transition energy.

*D. Trbojevic et al. ”Design Method for High Energy Accelerator Without Transition Energy”, EPAC 90, Nice, June 12-16 (1990) pp. 1536-1538.

 
 
MOPP006 Machine Induced Backgrounds for FP420 proton, background, simulation, scattering 559
 
  • R. Appleby, K. M. Potter, F. Roncarolo, G. J. Sellers
    UMAN, Manchester
  • I. Azhgirey, I. Baishev, I. L. Kurochkin, V. Talanov
    IHEP Protvino, Protvino, Moscow Region
  • M. Ruspa
    INFN-Torino, Torino
  The LHC FP420 collaboration is assessing the feasibility of installing forward proton detectors at 420m from the ATLAS and/or CMS interaction points. Such detectors aim at measuring diffracted protons, which lost less than 2% of their longitudinal momentum. The success of this measurement requires a very good understanding of the charged and neutral particle environment in the detector region in order to avoid the signal being swamped as well as for detector survivability. This background receives contributions from beam-gas interactions, halo particles surviving from the Betatron and momentum cleaning systems and secondary showers produced by particles from the 14TeV collision region striking the beampipe upstream of the FP420 detectors. In this paper, such background sources are reviewed, and the expected background rates calculated.  
 
MOPP013 Coupler Kick for Very Short Bunches and its Compensation emittance, focusing, laser, radio-frequency 580
 
  • M. Dohlus, I. Zagorodnov
    DESY, Hamburg
  • E. Gjonaj, T. Weiland
    TEMF, Darmstadt
  In this contribution we estimate two different effects: the kick due to asymmetry of the external accelerating field (coupler RF kick) and the kick due to electromagnetic field of the bunch scattered by the couplers (coupler wake kick). We take into acoount the cavities and calculate the periodic solution for bunch with an rms width of 300 mkm. The different possibilities for compensation of the kick are considered.  
 
TUOBG01 Observations of Beam-beam Tune Spectrum and Measurement of Coherent Tune Shift at KEKB luminosity, electron, emittance, positron 962
 
  • T. Ieiri, Y. Ohnishi, M. Tobiyama, S. Uehara
    KEK, Ibaraki
  KEKB is a double-ring electron/positron collider with a horizontal crossing angle. The crab cavities installed in 2007 achieved an effective head-on collision and gained a higher specific luminosity. Under the new crabbing collision as well as the horizontal crossing collision, tune spectra of a colliding bunch were observed on a spectrum analyzer to study beam-beam effects. The beam-beam spectrum showed strong nonlinear resonant phenomena. Considering the nonlinearity, the coherent beam-beam tune shift was measured as a function of the bunch current. It was confirmed that the vertical beam-beam parameter estimated from the coherent beam-beam tune shift agreed with a value obtained from a bunch-by-bunch luminosity monitor. The estimated vertical beam-beam parameter was saturated on a level of about 0.04, which is called a beam-beam limit. We found that the bunch current corresponding to the beam-beam limit was far below the bunch current used in the usual operation.  
slides icon Slides  
 
TUOBG02 Study of Beam Dynamics During the Crossing of Resonances in the VEPP-4M Storage Ring resonance, octupole, emittance, collider 965
 
  • P. A. Piminov, V. A. Kiselev, E. B. Levichev, O. I. Meshkov, S. A. Nikitin
    BINP SB RAS, Novosibirsk
  The influence of resonances on the beam dynamics in the storage rings is of a substantial interest for the accelerator physics. For example, a fast crossing of resonances occurs in the damping rings of future linear colliders during the beam damping due to the coherent shift that can result in a loss of particles. We have studied experimentally the crossing of resonances of different power nearby the working point of the VEPP-4M storage ring. The observation of the beam sizes and particle losses has been done with a single-turn time resolution. The comparison with the numerical simulation has been made.  
slides icon Slides  
 
TUPC040 Measurements of Beam-beam Kick using a Gated Beam-position Monitor under Crabbing Collision at KEKB positron, electron, beam-beam-effects, luminosity 1143
 
  • T. Ieiri, H. Fukuma, Y. Funakoshi, M. Masuzawa, K. Ohmi, M. Tobiyama
    KEK, Ibaraki
  KEKB is a double-ring electron/positron collider with a horizontal crossing-angle. The crab cavities installed in 2007 achieved an effective head-on collision and gained a higher specific luminosity. A gated beam-position monitor is a tool to measure the beam-beam effects. A beam-beam kick curve was measured by comparing the beam position between colliding and non-colliding bunches, while shifting the beam orbit at the interaction point (IP). An effective horizontal beam size at the IP was obtained from a linear part of the beam-beam kick around the central orbit. The estimated beam size agreed with a calculated value including the dynamic effects. It was confirmed that the effective horizontal beam size was reduced by the crabbing collision, as expected from a calculation with a rigid Gaussian model. When a horizontal orbit offset was larger than a beam size, however, we found that the measured beam-beam kick curve deviated from calculated values using the Gaussian model. The result suggests that the beam profile might enlarge horizontally in the peripheral part.  
 
TUPC044 Towards Routine Operation of the Digital Tune Monitor in the Tevatron proton, pick-up, antiproton, feedback 1155
 
  • V. Kamerdzhiev, V. A. Lebedev, A. Semenov
    Fermilab, Batavia, Illinois
  The digital tune monitor (DTM) was designed to measure bunch-by-bunch tunes in the Tevatron collider. It uses a standard BPM as a pickup. The vertical proton monitor is installed and allows us to gain valuable operational experience. A major upgrade is underway to implement an automatic bunch-by-bunch gain and offset adjustment to maintain the highest possible sensitivity under real operational conditions. Once the system is shown to be able to cope with orbit changes and different bunch intensities in an automatic manner while reliably delivering data it will be expanded to measure horizontal proton as well as antiproton tunes. The motivation and the technical description of the DTM as well as the latest experimental results are presented. Major challenges from the design and operation point of view are discussed.  
 
TUPC072 Design and Fabrication of an X-band Traveling Wave Deflection Mode Cavity for Longitudinal Characterization of Ultra-short Electron Beam Pulses electron, diagnostics, dipole, simulation 1215
 
  • A. Y. Murokh, R. B. Agustsson, S. Boucher, P. Frigola
    RadiaBeam, Marina del Rey
  • D. Alesini
    INFN/LNF, Frascati (Roma)
  • R. J. England, J. B. Rosenzweig, G. Travish
    UCLA, Los Angeles, California
  • V. Yakimenko
    BNL, Upton, Long Island, New York
  An X-band Traveling wave Deflector mode cavity (XTD) has been developed at Radiabeam Technologies to perform longitudinal characterization of the sub-picosecond ultra-relativistic electron beams. The device is optimized for the 100 MeV electron beam parameters at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory, and is scalable to higher energies. An XTD is designed to operate at 11.424 GHz, and features short filling time, femtosecond resolution, and a small footprint. RF design, fabrication procedure, and commissioning plans are presented. An experimental program at ATF to utilize the deflector for compressed beam characterization is discussed, including proposed measurements of the phase space filamentation due to non-linear processes in a chicane compressor.  
 
TUPC084 Combating Multi-bunch Instabilities with the Libera Bunch-by-bunch Unit feedback, kicker, single-bunch, target 1251
 
  • V. Poucki, T. Karcnik, P. L. Lemut, M. O. Oblak
    Instrumentation Technologies, Solkan
  Libera Bunch by Bunch is the digital processing unit for a bunch by bunch feedback system. The upgraded unit has a DSP core application featuring a 16 tap filter for each bunch. DSP processing is organized in 4 chains, following the HW implementation of A/D conversion. Besides setting of FIR filter coefficients in each processing chain, one bunch per chain can have different FIR filter coefficients and provides an option for 4 single bunch processing. All FIR filter coefficients are double buffered. Delays maximally equal to a revolution period are implemented before and after the FIR block. As an additional feature, a phase shift block is introduced that precisely shifts the phase of the output signal in the vicinity of a determined frequency. The core application is accompanied with a Matlab GUI, with an additional window for data acquisition. This system accompanied by a Front End unit provides a complete solution for combating multi bunch beam instabilities. A detailed description and results are presented.  
 
TUPC098 Results of the LHC Prototype Chromaticity Measurement System Studies in the CERN-SPS controls, feedback, coupling, emittance 1290
 
  • R. J. Steinhagen, A. Boccardi, T. Bohl, M. Gasior, O. R. Jones, J. Wenninger
    CERN, Geneva
  • K. K. Kasinski
    AGH, Cracow
  Tune and chromaticity control is an integral part of safe and reliable LHC operation. Tight tolerances on the maximum transverse beam excursions allow oscillation amplitudes of less than 30 um. This leaves only a small margin for transverse beam and momentum excitations required for measuring tune and chromaticity. This contribution discusses the baseline LHC continuous chromaticity measurement with results from tests at the CERN-SPS. The system is based on continuous tracking of the tune using a phase-locked-loop (PLL) while modulating the beam momentum. The high PLL tune resolution achieved ( ~1·10-6 ) made it possible to detect chromaticity changes well below the nominally required 1 unit for relative momentum modulations of only 2·10-5. The sensitive tune measurement front-end employed allowed the PLL excitation and radial amplitudes to be kept below a few tens of micrometers. These results show that this type of measurement can be considered as practically non-perturbative permitting its use even during nominal LHC operation.  
 
TUPP032 Trajectory Jitter and Single Bunch Beam Break Up Instability linac, emittance, quadrupole, simulation 1607
 
  • S. Di Mitri, P. Craievich
    ELETTRA, Basovizza, Trieste
  • M. Borland
    ANL, Argonne, Illinois
  • A. Zholents
    LBNL, Berkeley, California
  This paper addresses stability issues related to control of the beam break up (BBU) instability in the FERMI@Elettra linac using local trajectory bumps. Analytical study and simulations using the Elegant code are presented. Three different parameters have been used to characterize the BBU, i.e. the projected emittance, the bunch head-to-tail deviation, and the Courant-Snyder invariant for the slice centroid. It is shown that shot-to-shot trajectory jitter in the injector affects the efficiency of the control of the BBU.  
 
TUPP068 Bench Measurements of the Low Frequency Transverse Impedance of the CERN LHC Beam Vacuum Interconnects with RF Contacts impedance, vacuum, cryogenics, coupling 1697
 
  • B. Salvant
    EPFL, Lausanne
  • F. Caspers, E. Métral
    CERN, Geneva
  • F. Roncarolo
    UMAN, Manchester
  The low frequency longitudinal and transverse impedances of the CERN Large Hadron Collider (LHC) have to be specifically minimized to prevent the onset of coherent instabilities. The LHC beam vacuum interconnects were designed as Plug In Modules (PIMs) with RF contacts to reduce their coupling impedances, but the resulting contact resistance is a concern, as this effect is difficult to estimate. High sensitivity measurements of the transverse impedance of a PIM at low frequency using a coil probe are presented. In particular, the increase of the transverse impedance of the PIM when it is elongated to its operating position is discussed in detail. Finally, the issue of non-conforming contact resistance is also addressed.  
 
TUPP079 Distortion of Crabbed Bunch due to Electron Cloud with Global Crab electron, luminosity, optics, positron 1715
 
  • L. Wang, Y. Cai, T. O. Raubenheimer
    SLAC, Menlo Park, California
  In order to improve the luminosity, crab cavities have been installed in the KEKB HER and LER. Since there is only one crab cavity in each ring, the crab cavity generates a horizontally titled bunch oscillating around the whole ring. The electron cloud in LER (positron beam) may distort the crabbed bunch and cause the luminosity drop. This paper briefly estimates the distortion of positron bunch due to the electron cloud with global crab.  
 
TUPP119 Lattice Design of a Carbon Ion Synchrotron for Cancer Therapy extraction, resonance, lattice, synchrotron 1803
 
  • H.-S. Kang, H. S. Suh
    PAL, Pohang, Kyungbuk
  A synchrotron accelerator for carbon ion cancer therapy was designed to be compact for a hospital based therapy facility. The circumference of the synchrotron is only 60 meter and the lattice is the FODO structure of 6 cells. Each cell has two dipole magnets with a angle of 30 degree. The lattice satisfies the requirement of Hardt condition for slow beam extraction which is to align the separatrices of different momenta of the particles.  
 
TUPP150 The Radiatron: A High Average Current Betatron for Industrial and Security Applications acceleration, focusing, electron, injection 1860
 
  • S. Boucher, R. B. Agustsson, P. Frigola, A. Y. Murokh, M. Ruelas
    RadiaBeam, Los Angeles
  • F. H. O'Shea, J. B. Rosenzweig, G. Travish
    UCLA, Los Angeles, California
  The fixed-field alternating-gradient (FFAG) betatron has emerged as a viable alternative to RF linacs as a source of high-energy radiation for industrial and security applications. For industrial applications, high average currents at modest relativistic electron beam energies, typically in the 5 to 10 MeV range, are desired for medical product sterilization, food irradiation and materials processing. For security applications, high power x-rays in the 3 to 20 MeV range are needed for rapid screening of cargo containers and vehicles. In a FFAG betatron, high-power output is possible due to high duty factor and fast acceleration cycle: electrons are injected and accelerated in a quasi-CW mode while being confined and focused in the fixed-field alternating-gradient lattice. The beam is accelerated via magnetic induction from a betatron core made with modern low-loss magnetic materials. Here we present the design and status of a prototype FFAG betatron, called the RadiaTron, as well as future prospects for these machines.  
 
WEPC003 Coupling Control at the SLS coupling, quadrupole, emittance, sextupole 1983
 
  • A. Streun, Å. Andersson, M. Böge, A. Luedeke
    PSI, Villigen
  The vertical beam size measurement at the Swiss Light Source (SLS) is based on vertically polarized visual light and allows to verify a vertical emittance of a few pm rad, resp. an emittance ratio in the 10-4 range obtained in 400 mA top-up user operation mode by tuning the lattice by means of 24 skew quadrupoles. Suppression of betatron coupling by local and global coupling correction prevents losses of Touschek scattered particles at the narrow vertical gaps of the in-vacuum undulators and thus protects these devices and increases beam lifetime, resp. the top-up interval. We will report on our experience with the beam size monitor, on the method of coupling control and on the achievements in vertical emittance and beam lifetime.  
 
WEPC107 Observation and Interpretation of Dynamic Focusing Effects Introduced by APPLE-II Undulators on Electron Beam at SOLEIL undulator, electron, focusing, storage-ring 2249
 
  • O. V. Chubar, P. Brunelle, M.-E. Couprie, J.-M. Filhol, A. Nadji, L. S. Nadolski
    SOLEIL, Gif-sur-Yvette
  The paper presents the results of electron beam closed orbit distortion (COD) and tune shift measurements performed on three different APPLE-II type undulators when making horizontal displacements of the electron beam orbit in those straight sections of the SOLEIL storage ring where these undulators are installed. In agreement with data from other storage rings, our results show that, when APPLE-II undulators are used in elliptical, linear-vertical or linear-tilted polarization modes, the measured tune shifts and the COD can not be explained only by residual first-order focusing effects: taking into account the second-order, or dynamic focusing effects, is necessary. We describe a COD interpretation method allowing for straightforward comparison of the measured effects on electron beam with the corresponding predictions from calculations and magnetic measurements. The observed dynamic effects are in good agreement with calculations performed using RADIA code. We also discuss possible modification of the figures of merit to be used at computer-aided shimming of APPLE-II undulators, which would allow for simultaneous minimization of the first- and second-order focusing effects.  
 
WEPC117 Influence of Insertion Devices on the ALBA Dynamic Aperture wiggler, undulator, lattice, dynamic-aperture 2279
 
  • E. B. Levichev, P. A. Piminov
    BINP SB RAS, Novosibirsk
  • D. Einfeld
    ALBA, Bellaterra
  Insertion devices can produce effects reducing the dynamic aperture in a storage ring. To study these effects for the ALBA light source the following insertion devices were inserted in the ALBA lattice: a superconducting wiggler SC-W31 with 31-mm-period and 2.1-T-field amplitude, and two Apple-II type PMM NdFeB undulators with periods of 62 mm (HU62) and 71 mm (HU71). Results of numerical study of the nonlinear beam dynamics by a 6D computer code are presented.  
 
WEPP003 Optics Flexibility in the LHC at Top Energy optics, injection, quadrupole, luminosity 2524
 
  • M. Aiba, H. Burkhardt, S. D. Fartoukh, M. Giovannozzi, S. M. White
    CERN, Geneva
  We report on studies of optics flexibility which allow for tune changes of the order of half a unit at top energy in the LHC. We describe how this could be done using one or several of the insertions IR2, IR4, IR8 or the main quadrupoles and discuss and compare the implications. This flexibility could be used to compensate for the loss in tune for high beta optics and may make it feasible to use the standard injection and ramp for these configurations. Potential further applications are also highlighted.  
 
WEPP025 Optics Correction in the LHC quadrupole, dipole, closed-orbit, optics 2572
 
  • R. Tomas, M. Aiba, G. Vanbavinckhove
    CERN, Geneva
  • R. Calaga
    BNL, Upton, Long Island, New York
  • A. Morita
    KEK, Ibaraki
  Optics correction in the LHC is challenged by the tight aperture constrains and the demand of a highly performing BPM system. To guarantee that the LHC optics remains within a maximum allowable beta-beating of 20% several methods are being investigated through computer simulations and experiments at existing hadron machines. A software package to consolidate the implementation of the various techniques during LHC operation is underway (or nearing completion)  
 
WEPP037 Independent Component Analysis of Tevatron Turn-by-turn BPM Measurements synchrotron, collider, optics, extraction 2602
 
  • A. V. Petrenko
    BINP SB RAS, Novosibirsk
  • V. A. Lebedev, A. Valishev
    Fermilab, Batavia, Illinois
  Transverse dipole coherent beam oscillations in the Tevatron were analyzed with different independent component analysis algorithms. This allowed to obtain the model-independent values of coupled beta-functions as well as betatron phase advance and dispersion along the ring from a single kick measurement. Using a 1-turn shift of turn-by-turn BPM readings for virtual doubling of the number of BPMs it is also possible to measure the fractional part of betatron tunes with high accuracy. Good agreement with the linear optical model of the Tevatron was observed.  
 
WEPP045 Suppression of Beam-beam Resonances in Crab Waist Collisions luminosity, sextupole, resonance, collider 2620
 
  • M. Zobov, P. Raimondi
    INFN/LNF, Frascati (Roma)
  • D. N. Shatilov
    BINP SB RAS, Novosibirsk
  The recently proposed Crab Waist scheme of beam-beam collisions can substantially increase the collider luminosity since it combines several potentially advantageous ideas. One of the basic ingredients of the scheme is the use of dedicated sextupoles in the interaction region for the vertical beta function waist rotation at the interaction point. In this paper we show how this nonlinear focusing helps to suppress betatron and synchrobetatron resonances arising in beam-beam collisions due to particles’ vertical motion modulation by their horizontal oscillations.  
 
WEPP058 Optics Measurements and Matching of TT2-TT10 Line for Injection of the LHC Beam in the SPS optics, injection, scattering, emittance 2650
 
  • E. Benedetto, G. Arduini, A. Guerrero, D. Jacquet
    CERN, Geneva
  A well matched injection in the SPS is very important for preserving the emittance of the LHC beam. The paper presents the algorithms used for the analysis and the results of the optics measurements done in the transfer line TT2-TT10 and in the SPS. The dispersion is computed by varying the beam momentum and recording the offsets at the BPMs, while the Twiss parameters and emittance measurements in TT2-TT10 are performed with beam profile monitors equipped with OTR screens. These results are completed by those obtained with a matching monitor installed in the SPS as a prototype for the LHC. This device makes use of an OTR screen and a fast acquisition system, to get the turn by turn beam profiles right at injection in the ring, from which the beam mismatch is computed and compared with the results obtained in the line. Finally, on the basis of such measurments, a betatron and dispersion matching of TT2-TT10 for injection in the SPS has been performed and successfully put in operation.  
 
WEPP134 Ultra-short x-ray Radiation coming from a Laser Wakefield Accelerator electron, plasma, laser, radiation 2809
 
  • V. Leurent, L. Divol, T. Doeppner, D. H. Froula, S. H. Glenzer, P. Michel, J. Palastro
    LLNL, Livermore, California
  • C. E. Clayton, C. Joshi, K. A. Marsh, A. E. Pak, J. E. Ralph, T.-L. Wang
    UCLA, Los Angeles, California
  • B. B. Pollock, G. R. Tynan
    UCSD, La Jolla, California
  A Laser Wakefield Accelerator (LWFA) is under development at LLNL Jupiter Laser Facility to produce multi-GeV electron bunches promising to provide a bright and compact source of x-ray radiation for high energy density studies. The interaction of a high power (200 TW), short laser (50 fs) pulse with neutral He gas can accelerate monoenergetic electrons up to 1 GeV in a stable self-guiding regime*, over a dephasing length of 1 cm (for a plasma density of 1.5x1018 cm-3), overcoming the limitation of vacuum diffraction and allowing long interaction lengths for LWFA. The waveguide can be extended over several centimeters by using a novel scheme, which employs an external magnetic field (up to 5 T uniform along 12 cm) to control the radial heat flux** resulting from the interaction of a high energy (100 J), long pulse (1 ns) laser with a gas tube. The acceleration of electrons over several centimeters can produce multi-GeV bunches and thus a powerful x-ray source. Analysis will be presented on femtosecond x-ray radiation produced by wiggling an electron bunch with energy above 1 GeV in this new LWFA scheme.

* W. Lu et al., Phys. Rev. Spec. Top-ac 10, 061301 (2007)
** D. H. Froula et al., Phys. Rev. Lett. 98, 135001 (2007)

 
 
WEPP149 Advances in Parametric-resonance Ionization Cooling resonance, emittance, coupling, space-charge 2838
 
  • Y. S. Derbenev
    Jefferson Lab, Newport News, Virginia
  • R. P. Johnson
    Muons, Inc, Batavia
  Parametric-resonance ionization cooling (PIC) is a muon-cooling technique that is useful for low-emittance muon colliders. This method requires a well-tuned focusing channel that is free of chromatic and spherical aberrations. The dispersion function of the channel must be large where the correction magnets are placed for aberration control but small and non-zero where the ionization cooling beryllium wedges are located to provide emittance exchange to maintain small momentum spread. In order to be of practical use in a muon collider, it also necessary that the focusing channel be as short as possible to minimize muon loss due to decay. A compact PIC focusing channel is described in which new magnet concepts are used to generate the required lattice functions.  
 
THPC003 Sum of Emittance in the Presence of a Linear Coupling emittance, coupling, quadrupole, focusing 2975
 
  • M. Aslaninejad, H. Ghasem
    IPM, Tehran
  In this article, the influence of linear coupling due to skew quadrupoles on the transverse equations of motion and emittances in accelerators is studied*. We first introduce the definition of the transverse single particle emittances using the Floquet transformation in alternating gradient as well as the constant focusing rings, then in the presence of the linear coupling, due to skew quadrupoles we introduce the coupled differential equations governing the particles motion and try to solve them by a direct method and also using the normal modes of motion to find the relation between the two transverse emittances. Based on smooth approximation and using the normal modes** we solve the equations of motion of a test charged particle and derive two new formulas for the sum of the emittances, and the conditions under which this sum is invariant.

*P. J.Bryant, CERN Acclerator School, CERN, PROCEEDINGS, 94-01, Vol. I.
**E. Metral, CERN/PS 2001-066(AE).

 
 
THPC008 Constants and Pseudo-constants of Coupled Beam Motion in the PEP-II Rings coupling, sextupole, quadrupole, lattice 2990
 
  • F.-J. Decker, W. S. Colocho, M.-H. Wang, Y. T. Yan, G. Yocky
    SLAC, Menlo Park, California
  Constants of beam motion help as cross checks to analyze beam diagnostics and the modeling procedure. Pseudo-constants, like the betatron mismatch parameter or the coupling parameter det C, are constant till certain elements in the beam line change then. This can be used to visually find the non-desired changes, pinpointing errors compared with the model.  
 
THPC023 Optimization of the AGS Superconducting Helical Partial Snake Strength resonance, polarization, acceleration, simulation 3026
 
  • F. Lin, H. Huang, A. U. Luccio, T. Roser
    BNL, Upton, Long Island, New York
  Two helical partial snakes, one is superconducting (called cold snake) and one is normal conducting (called warm snake), have preserved the polarization of proton beam up to 65% at the AGS extraction energy with the inject 82% polarization. In order to overcome the spin resonances, stronger partial snake is required. However, the stronger partial snake, the more titled stable spin direction that results in stronger horizontal intrinsic resonance. The balance between raising the spin tune gap generated by the snakes and reducing the titled stable spin direction has to be considered to maintain the polarization. Because the magnetic field of the warm snake is constant, only the cold snake with a maximum 3T magnetic field can be varied to find out the optimized snake strength. The paper presents the simulation results from the spin tracking with different cold snake magnetic fields. Some experimental data are also analyzed.  
 
THPC026 Measurement of Complex Coupling Driving Term of Linear Difference Resonance Using Turn-by-turn Beam Position Monitors coupling, quadrupole, resonance, storage-ring 3035
 
  • M. Masaki, K. Soutome, S. Takano, M. Takao
    JASRI/SPring-8, Hyogo-ken
  X-Y emittance coupling is one of the important measures of beam quality in an electron storage ring for high brilliant light source. We have developed a method of measuring complex coupling driving term C of linear difference resonance using turn-by-turn beam position monitors (BPMs), assuming the perturbation theory with the single resonance approximation. Since both amplitude and phase of the driving term are derived, we can uniquely determine the strength of two-degree-of-freedom skew quadrupole magnets for correction of the linear resonance coupling. Before the correction, the driving term was measured by the developed method at the SPring-8 storage ring where small skew quadrupole components are distributed as error magnetic fields. On the other hand, the linear resonance coupling was corrected using the counter skew quadrupole magnets, the strength of which was adjusted to minimize vertical beam size near the linear difference resonance. The measured driving term C was broadly consistent with the counter term calculated from the adjusted strength of skew quadrupole magnets for the coupling correction.  
 
THPC053 Turn-by-turn Data Analysis at the Diamond Storage Ring storage-ring, optics, resonance, quadrupole 3101
 
  • R. Bartolini, I. P.S. Martin, G. Rehm, J. Rowland
    Diamond, Oxfordshire
  The Diamond Storage Ring has been recently equipped with a set of two pinger magnets that can excite betatron oscillations to large amplitudes in both planes of motion. In conjunction with the turn-by-turn capabilities available at all BPMs, the system provides a powerful diagnostic tools for the characterisation of the linear and non-linear beam dynamics of the electron beam in the storage ring. We report the first results on the application of the Frequency Map Analysis and the measurement of the resonant driving terms at the Diamond Storage Ring.  
 
THPC060 Spin Flip of Deuterons in COSY - Spink Tracking resonance, dipole, simulation, polarization 3122
 
  • A. U. Luccio
    BNL, Upton, Long Island, New York
  • A. Lehrach
    FZJ, Jülich
  The spin tracking code Spink, as recently overhauled*, has been used to study the deuteron spin resonances and spin flipping induced by a RF dipole and a RF solenoid. The modifications of the code followed extended discussions on the formalism used to model spin evolution in a synchrotron. The simulation shows a good agreement with published results of the measurements**.

*A. U. Luccio et al. See another contribution to this Conference.
**A. D. Krisch et al. PR-STAB 10, 07100-1, 2007.

 
 
THPC067 ALBA Dynamic Aperture Optimization dynamic-aperture, resonance, sextupole, lattice 3140
 
  • P. A. Piminov, E. B. Levichev
    BINP SB RAS, Novosibirsk
  • D. Einfeld
    ALBA, Bellaterra
  The lattice of ALBA, the 3 GeV synchrotron light source in Spain, provides extremely low emittance of the beam. It is known that such lattices require strong sextupole magnets to compensate natural chromaticities. The paper describes strategy and results of the ALBA dynamic aperture optimization including both tune point selecting and sextupoles arrangement to increase the DA size.  
 
THPC070 Symmetry Restoration of the SPring-8 Storage Ring by Counter-sextupole Magnets sextupole, dynamic-aperture, electron, lattice 3149
 
  • K. Soutome, S. Daté, T. Fujita, K. Fukami, C. Mitsuda, A. Mochihashi, H. Ohkuma, M. Oishi, S. Sasaki, J. Schimizu, Y. Shimosaki, M. Shoji, M. Takao, K. Tsumaki, H. Yonehara, C. Zhang
    JASRI/SPring-8, Hyogo-ken
  • S. Matsui, H. Takebe, H. Tanaka
    RIKEN/SPring-8, Hyogo
  In the SPring-8 storage ring there are four magnet-free long straight sections of about 30m. These were realized in 2000 by locally rearranging quadrupole and sextupole magnets. In modifying the optics we took care of the periodicity of cell structure, especially of sextupole field distribution along the ring. To keep the periodicity high and hence the dynamic aperture large, we adopted a scheme in which "betatron phase matching" and "local chromaticity correction" are combined. In this scheme the dynamic aperture for on-momentum electrons is kept by the phase matching and that for off-momentum electrons is enlarged by the local chromaticity correction with weak sextupoles (SL). After modifying the lattice, we tried to recover the symmetry of the ring further and found that a harmful effect of nonlinear kick due to SL can be minimized by additional "counter-sextupole magnets" placed 180 degrees apart in horizontal betatron phase from SL. We installed such counter-sextupoles in every long straight sections and confirmed that the aperture was improved. In the paper we discuss these topics showing experimental data of injection efficiency, momentum acceptance, etc.  
 
THPC072 Impact of Betatron Motion on Path Lengthening and Momentum Aperture in a Storage Ring storage-ring, optics, resonance, undulator 3152
 
  • M. Takao
    JASRI/SPring-8, Hyogo-ken
  The amplitude of the betatron motion in an electron storage ring becomes large in some cases, e.g. Touschek scattered electrons or injected beam. Then we cannot ignore the effect of a finite amplitude of betatron motion on the beam dynamics. The path lengthening of the central trajectory of betatron motion is one of the most serious manifestations of such an influence. Due to the synchrotron motion, the variation of the path length is converted into the energy deviation, so that the betatron motion gives the impact on the momentum aperture in the storage ring. In this paper the path lengthening by a finite amplitude betatron motion is calculated by means of the canonical perturbation method. The derived formula for the path lengthening is simply represented by the product of the chromaticity and the invariant amplitude. Using the formula, we discuss the impact of the betatron motion on momentum aperture in a Touschek effect.  
 
THPC116 Commissioning of the iGp Feedback System at DAΦNE feedback, single-bunch, controls, diagnostics 3251
 
  • A. Drago
    INFN/LNF, Frascati (Roma)
  • J. D. Fox
    SLAC, Menlo Park, California
  • D. Teytelman
    Dimtel, San Jose
  • M. Tobiyama
    KEK, Ibaraki
  The iGp (Integrated Gigasample Processor) is an innovative digital bunch-by-bunch feedback system developed by a KEK/SLAC/INFN-LNF joint collaboration. The processing unit can sample at 500 MHz and compute the bunch-by-bunch output signal for up to 5000 bunches. The feedback firmware code is implemented inside just one FPGA (Field Programmable Gate Array) chip, a Xilinx Virtex-II. The FPGA implements two 16 taps FIR (Finite Impulse Response) filter that are realtime programmable through the operator interface. At DAΦNE, the Frascati PHI-Factory, two iGp units have been commissioned in the April 2007. The iGp systems have plugged in the previous betatron feedback systems. This insertion has been very fast and has shown no problems involving just a substitution of the old, less flexible, digital unit, letting unchanged the baseband analog frontend and the analog backend. The commissioning has been very simple, due to the complete and powerful EPICS operator interface, working well in local and remote operations. The software includes also tools for analyzing post processor data. A description of the commissioning with the operations done to find the best feedback setup are reported.  
 
THPC122 Digital Signal Processing for the Multi-bunch LHC Transverse Feedback System pick-up, kicker, feedback, damping 3269
 
  • W. Höfle, P. Baudrenghien, G. Kotzian, V. Rossi
    CERN, Geneva
  For the LHC a VME card has been developed that contains all functionalities for transverse damping, diagnostics and controlled bunch by bunch excitation. It receives the normalized bunch by bunch position from two pick-ups via Gigabit Serial Links (SERDES). A Stratix II FPGA is responsible for resynchronising the two data streams to the bunch-synchronous clock domain (40.08 MHz) and then applying all the digital signal processing: In addition to the classic functionalities (gain balance, rejection of closed orbit, pick-up combinations, one-turn delay) it contains 3-turn Hilbert filters for phase adjustment with a single pick-up scheme, a phase equalizer to correct for the non-linear phase response of the power amplifier and an interpolator to double the processing frequency followed by a low-pass filter to precisely control the bandwidth. Using two clock domains in the FPGA the phase of the feedback loop can be adjusted with a resolution of 10 ps. Built-in diagnostic memory (observation and post-mortem) and excitation memory for setting-up are also included. The card receives functions to continuously adjust its parameters as required during injection, ramping and physics.  
 
THPC127 Filling of High Current Singlet and Train of Low Bunch Current in SPring-8 Storage Ring feedback, injection, kicker, damping 3284
 
  • T. Nakamura, T. Fujita, K. Fukami, K. Kobayashi, C. Mitsuda, M. Oishi, S. Sasaki, M. Shoji, K. Soutome, M. Takao, Y. Taniuchi
    JASRI/SPring-8, Hyogo-ken
  • T. Ohshima
    RIKEN/SPring-8, Hyogo
  • Z. R. Zhou
    USTC/NSRL, Hefei, Anhui
  We performed the storage of high current singlet of 10mA/bunch and a train of bunches of 0.3mA/bunch under the bunch by bunch feedback systems with newly developed bunch current sensitive automatic attenuators with FPGA. The automatic attenuator reduces the signal level of the high current bunch by factor three to five to avoid the saturation of the feedback systems. With this system, the feedback systems suppress horizontal and vertical mode-coupling instabilities and raise the bunch current limit from 3.5mA/bunch to 12mA/bunch, and simultaneously the systems suppress the multi-bunch instabilities by resistive-wall and cavity higher order mode impedances. The improvement of the automatic attenuation system to fit to the final target of the bunch current in the train, 0.06mA/bunch, are being performed. The other problems which limit the filling patterns, such as saturation of the readout electronics of the beam position monitor system and the heating of vacuum components by high current bunches, will be briefly presented.  
 
THPP008 Hamiltonian Approach to the Dynamics of Particles in Non-scaling FFAG Accelerators acceleration, lattice, focusing, proton 3392
 
  • B. D. Muratori, S. L. Smith, S. I. Tzenov
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  Starting from first principle the Hamiltonian formalism for the description of the dynamics of particles in non-scaling FFAG machines has been developed. The stationary reference (closed) orbit has been found within the Hamiltonian framework. The dependence of the path length on the energy deviation has been described in terms of higher order dispersion functions. The latter have been used subsequently to specify the longitudinal part of the Hamiltonian. It has been shown that higher order phase slip coefficients should be taken into account to adequately describe the acceleration in non-scaling FFAG accelerators.  
 
THPP009 Injection and Extraction Orbits and Twiss Parameters for the EMMA Ring injection, extraction, kicker, focusing 3395
 
  • B. D. Muratori, S. L. Smith, S. I. Tzenov
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  Using the FFEMMAG code, the injection and extraction orbits for the EMMA ring at a variety of injection and extraction energies together with the Twiss parameters to be used for matching have been calculated. The orbits include two kickers together with a septum at both injection and extraction. The FFEMMAG code has been used in conjunction with several scripts so as to be able to scan the parameter space of the two kicker strengths for a section of the EMMA ring. The results confirm the choice of magnet and vacuum pipe apertures as being adequate to operate EMMA from 10 to 20 MeV.  
 
THPP089 Gamma Transition Jump for PS2 optics, quadrupole, collective-effects, lattice 3572
 
  • W. Bartmann, M. Benedikt, E. Métral, D. Möhl
    CERN, Geneva
  • S. Peggs
    BNL, Upton, Long Island, New York
  The PS2, which is proposed as a replacement for the existing ~50-year old PS accelerator, is presently considered to be a normal conducting synchrotron with an injection kinetic energy of 4 GeV and a maximum energy of 50 GeV. One of the possible lattices (FODO option) foresees crossing of transition energy near 10 GeV. Since many intensity dependent effects can take place in both the longitudinal and the transverse planes a fast jump of gamma transition is necessary in order to pass the non-adiabatic region rapidly. The aim of the present paper is on the one hand to scale the gamma transition jump, used since 1973 in the PS, to the projected PS2 and on the other hand based on these results the analysis of the implementation and feasibility of a gamma transition jump scheme in a conventional FODO lattice.  
 
THPP096 Injection Optimisation on the ISIS Synchrotron injection, synchrotron, closed-orbit, simulation 3587
 
  • B. Jones, D. J. Adams, C. M. Warsop
    STFC/RAL/ISIS, Chilton, Didcot, Oxon
  The ISIS Facility at the Rutherford Appleton Laboratory in the UK produces intense neutron and muon beams for condensed matter research. At its core is a 50 Hz proton synchrotron which, as the commissioning of a new dual harmonic RF system concludes, can accelerate 3.75·1013 protons per pulse from 70 to 800 MeV, delivering a mean beam power of 0.24 MW. The multi-turn charge-exchange injection process strongly affects transverse beam distributions, space charge forces and beam loss, which ultimately limits operational intensity. The evolution of longitudinal distributions and subsequent trapping efficiency is also intimately linked with injection. Optimising injection is therefore a key consideration for present and future upgrades. This paper summarises injection studies including 2D space-charge simulations of the ISIS injection process using the ORBIT code. Comparisons of simulation results with measurements for a range of beam intensities are presented and an assessment is made of a correlated painting scheme in contrast to the usual anti-correlated configuration.