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closed-orbit

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MOPP011 Fast Vertical Beam Instability in the CTF3 Combiner Ring linac, injection, simulation, beam-losses 574
 
  • R. Corsini, D. Schulte, P. K. Skowronski, F. Tecker
    CERN, Geneva
  • D. Alesini, C. Biscari, A. Ghigo
    INFN/LNF, Frascati (Roma)
  The CLIC Test Facility CTF3 is being built at CERN by an international collaboration, in order to demonstrate the main feasibility issues of the CLIC two-beam technology by 2010. The facility includes an 84 m combiner ring, which was installed and put into operation in 2007. High-current operation has shown a vertical beam break-up instability, leading to high beam losses over the four turns required for nominal operation of the CTF3 ring. Such instability is most likely due to the vertically polarized transverse mode in the RF deflectors used for beam injection and combination. In this paper we report the experimental data and compare them with simulations. Possible methods to eliminate the instability are also outlined.  
 
MOPP055 A Comparison of Tuning Strategies for a Linear Collider Damping Ring emittance, lattice, quadrupole, damping 667
 
  • J. K. Jones
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  Emittance preservation is an important aspect in the design and running of any new Linear Collider design, with a direct consequence on the luminosity of the machine. Damping rings provide the lower limit on achievable emittance, and so are designed to produce as small a vertical emittance as possible, not only for luminosity considerations, but also to relax tolerances in downstream, emittance diluting, systems. Maintaining such small emittances requires that the damping ring emittance is regularly “tuned”. Several methods of damping ring tuning are investigated, and analysed both in terms of their relative effectiveness, under a variety of conditions, and the non-monetary cost involved in implementing and using the various algorithms.  
 
TUPC015 Data Acquisition and Analysis in SSRF BPM System storage-ring, booster, electron, controls 1077
 
  • Y. B. Yan, Y. Z. Chen, Y. B. Leng, W. M. Zhou, Y. Zou
    SINAP, Shanghai
  The beam position monitor (BPM) system in Shanghai Synchrotron Radiation Facility (SSRF) is fully (Linac, transfer line, booster and storage ring) equipped with Libera Electron BPM Processors. Primary data acquisition and position calculation has been done in Libera FPGA. EPICS support package developed by Diamond Light Source has been adapted to link BPM system with accelerator control system. Two dedicated soft IOCs are introduced to collect beam position data from all Libera IOCs and calculate RMS noise, histogram, spectrum and phase space, etc. online. Other BPM based analysis is completed via MATLAB scripts. The initial results during booster and storage ring commissioning will be described in this paper.  
 
TUPC119 Corrector Based Determination of Quadrupole Centres quadrupole, dipole, storage-ring, feedback 1347
 
  • M. Sjöström, M. Eriksson, L.-J. Lindgren, E. J. Wallén
    MAX-lab, Lund
  A corrector magnet based method to determine the quadrupole magnet centres for storage rings has been tested on the MAX III synchrotron light source. The required corrector magnet strengths for the corrected beam orbit are used to determine the quadrupole magnet centre positions. This method is the most effective for an optimal distribution of beam position monitors and corrector magnets in the storage ring and will be used as a basis for the MAX IV storage rings.  
 
TUPD031 Crystals Application in the TOTEM Experiment to Increase the Acceptance of a Roman Pot proton, optics, scattering, simulation 1491
 
  • E. Laface, W. Scandale
    CERN, Geneva
  • S. Hasan
    Univ. Insubria and INFN Milano, Como
  • C. Santoni
    Université Blaise Pascal, Clermont-Ferrand
  Bent crystal may enhance the physics reach of a near-beam physics detector in the CERN-LHC, by increasing the acceptance of scattered protons in low transverse momentum reactions. As an example we present simulations demonstrating the increase of the Roman Pot acceptance in the TOTME apparatus. Starting from the MadX v6.5 nominal optic, a crystal is placed at different longitudinal and transversal positions: for each scheme a gaussian beam of protons with different kinematic variables is created and tracked along the optical line with crystal. The number of protons with transversal coordinates greater than 10σ+0.5mm, that is inside the Roman Pot, is compared with the total number of protons. The possible gain in acceptance is around 15-20%.  
 
WEPC042 Commissioning of the SSRF Storage Ring storage-ring, emittance, sextupole, optics 2079
 
  • L. G. Liu
    SSRF, Shanghai
  • Z. M. Dai, B. C. Jiang, H. H. Li, D. Wang, W. Zhang, Z. T. Zhao
    SINAP, Shanghai
  The Shanghai Synchrotron Radiation Facility (SSRF) is a 3.5GeV synchrotron radiation light source under commissioning in Shanghai, China. The SSRF accelerator complex consists of a 150MeV linac, full energy booster and a 3.5GeV storage ring. The commissioning of the SSRF storage ring began on Dec. 21st evening, 2007, the first turn and 150 turns was observed in less than 12 hours with RF off and then the stored beam of 5 mA was achieved on Dec. 24th. On Jan. 3rd, 2008, the 100mA stored beam current were obtained in the machine for the first time. Since then, the storage ring has been brought close to the design parameters, and frequent operation with 100mA beam current has been down for making the vacuum chamber cleaning. In this paper, commissioning results of the machine is presented.  
 
WEPP008 Localizing Sources of Horizontal Orbit Oscillations at RHIC luminosity, emittance, focusing, feedback 2539
 
  • R. Calaga, R. J. Michnoff, T. Satogata
    BNL, Upton, Long Island, New York
  Horizontal oscillations of the closed orbit at frequencies around 10Hz are observed at RHIC. These oscillations lead to beam beam offsets at the collision point, resulting in emittance growth and reduced luminosity. An approach to localize the sources of these vibrations using a special mode of RHIC turn-by-turn BPM data is presented. Data from the 2005-06 are analyzed to spatially resolve the location of the dominant sources.  
 
WEPP018 Operational Experience with a Near-integer Working Point at RHIC proton, background, heavy-ion, dynamic-aperture 2563
 
  • C. Montag, M. Bai, J. Beebe-Wang, W. Fischer, Y. Luo, N. Malitsky, T. Roser, T. Satogata, S. Tepikian
    BNL, Upton, Long Island, New York
  During the RHIC polarized proton run in FY 2006 it became evident that the luminosity performance is limited by the beam-beam effect. With a working point between 2/3 and 7/10, and the necessity to mirror the tunes of the two RHIC rings at the diagonal, the beam with a horizontal tune closest to 2/3 showed poor lifetime. To overcome this limitation, a near-integer working point has been proposed. Tracking studies performed at both working points showed a larger dynamic aperture near the integer tune than above 2/3. In Run-8, this new working point was commissioned in one ring of RHIC, while the other ring was operated at the same working point as in Run-6. In this paper we report the commissioning process and operational experience with this new working point.  
 
WEPP025 Optics Correction in the LHC quadrupole, dipole, optics, betatron 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)  
 
WEPP116 Muon Decay Ring Study emittance, dynamic-aperture, quadrupole, storage-ring 2770
 
  • D. J. Kelliher, S. Machida, C. R. Prior, G. H. Rees
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon
  • F. Meot
    CEA, Gif-sur-Yvette
  Three different muon decay ring configurations are being considered for a neutrino factory. A racetrack design is the current ISS baseline (as it allows greater flexibility in the choice of detector sites) but triangular and bow-tie rings have advantages in neutrino production rates*. Using tracking code simulations, a study of the latter two designs is carried out. Since spin depolarisation measurements have been proposed for muon energy calibration**, spin tracking is included in this study. Dynamic aperture is important and is also calculated.

*International Scoping Study report, 2006.
**A Blondel et al. (editors), ECFA/CERN studies of a European Neutrino Factory Complex, CERN-2004-002 and EFCA/04/230, 13 April, 2004.

 
 
WEPP121 Recirculating Ring for an Ionization Cooling Channel emittance, lattice, factory, simulation 2779
 
  • C. T. Rogers
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon
  In a muon acceleration facility such as a Neutrino Factory or Muon Collider, the muons created from pion decay occupy a large volume of phase space. For a good capture efficiency this phase space should be reduced and this is typically achieved using ionisation cooling channels. These are quite expensive but the cost can be reduced by recirculating muons through the cooling hardware. Recirculating a high emittance beam typical of a Neutrino Factory is very challenging if it is to be achieved without significant losses. I describe latest attempts to design a high acceptance recirculator for a muon front end.  
 
THPPGM04 SLIM - An Early Work Revisited radiation, coupling, damping, lattice 2963
 
  • A. Chao
    SLAC, Menlo Park, California
  An early, but at the time illuminating, piece of work on how to deal with a general, linearly coupled accelerator lattice is revisited. This work is based on the SLIM formalism developed in 1979-1981.  
slides icon Slides  
 
THPC021 Investigations on a Q0 Doublet Optics for the LHC Luminosity Upgrade quadrupole, luminosity, optics, alignment 3023
 
  • E. Laface, W. Scandale, E. Y. Wildner
    CERN, Geneva
  • C. Santoni
    Université Blaise Pascal, Clermont-Ferrand
  The Q0 scheme of the LHC insertion region is based on the introduction of a doublet of quadrupoles at 13 meters from IP. We present here the doublet optics and the magnets layout such as gradients, lengths, positions and apertures. In this scheme we show the gain in luminosity and chromaticity, with respect to a nominal layout with β*=0.25 (i.e. LHC phase 1 upgrade) and β*=0.15 m, due to a smaller beta-max. We show the alignment tolerance and the energy deposition issues, in Q0A-Q0B. We also consider shielding the magnets with liners. The capability of Q0 optics to limit the β function could be exploited after the LHC Phase 1 upgrade in order to reduce the β* below 0.25 m, leaving the upgraded triplet unchanged.  
 
THPC032 Vertical Beam Size Reduction via Compensation of Residual Transverse Coupling coupling, wiggler, optics, simulation 3047
 
  • T. F. Roque, X. R. Resende, P. F. Tavares
    LNLS, Campinas
  The Brazilian Synchrotron Light Source (LNLS) is currently constructing a beamline which will make use of the radiation produced by the EPU installed in the storage ring (SR) in 2007. Various force tasks have been triggered by this new beamline in order to achieve required beam properties and stability. One of these tasks has to do with reducing the SR's vertical beam size at the straight section where the EPU is located, hence improving the radiation brilliance from the EPU. This report will describe our recent efforts in understanding and controlling what residual effects there are in the ring that dominate the ring's vertical beam size. In particular, we study the effects of residual coupling perturbations on the beam size through the transfer matrix formalism which, we argue, is the most appropriate. A beam model including transverse linear coupling is validated with measured closed orbit response functions. By Analyzing this model we are able to propose new skew quadrupole elements to the SR that might reduce the vertical beam size at the EPU section and we can infer the validity of results with a pinhole beam imaging system which we have available in our diagnostic beamline.  
 
THPC034 Correction the Round Beam Lattice of VEPP-2000 Collider Using Orbit Response Technique lattice, dipole, quadrupole, multipole 3053
 
  • A. L. Romanov, D. E. Berkaev, A. N. Kirpotin, I. Koop, E. Perevedentsev, Yu. A. Rogovsky, P. Yu. Shatunov, D. B. Shwartz
    BINP SB RAS, Novosibirsk
  Round colliding beams option in VEPP-2000 puts a number of strict requirements on the collider lattice. Orbit Response Matrix (ORM) technique is a versatile tool for lattice analysis and correction. For linear optical function study and correction, the orbit response to the dipole correctors is collected and processed, while for the orbit correction the quadrupole trimming is used. Theoretical and experimental responses of closed orbit on the same perturbations are compared to determine the most probable deviations of chosen parameters from its project values.  
 
THPC041 Closed Orbit Correction and Orbit Stabilization Control for TPS Storage Ring quadrupole, emittance, dipole, radiation 3068
 
  • H.-J. Tsai, H.-P. Chang, H. C. Chao, P. J. Chou, K. T. Hsu, C.-C. Kuo, W. T. Liu, J. W. Tsai
    NSRRC, Hsinchu
  TPS is a 3 GeV synchrotron storage ring proposed in Taiwan. The designed natural emittance with slightly positive dispersion in the straight sections is less than 2 nm-rad. With 1% emittance coupling, the beam size in horizontal and vertical plane are 120/5 micron in the short straight sections, respectively. The beam position stability requirements are 10% of the beam sizes, i.e., 12/0.5 micron in the horizontal/vertical plane. The closed orbit distortions due to alignment displacement and magnetic field errors are simulated. The distribution of beam position monitors and the location of slow and fast correctors are proposed and the level of achievement is shown.  
 
THPC066 Measuring Ring Nonlinear Components via Induced Linear "Feed-down" sextupole, resonance, simulation, beam-losses 3137
 
  • A. S. Parfenova, G. Franchetti, I. Hofmann
    GSI, Darmstadt
  The knowledge of the distribution in a ring of the non-linear components is important for the resonance compensation. We present a method to measure the lattice nonlinear components based on the non-linear tune response to a locally controlled closed orbit deformation. A test of this concept in the SIS18 synchrotron is presented and discussed.  
 
THPC076 Closed Orbit Correction and Sextupole Compensation Schemes for Normal-conducting HESR sextupole, dipole, electron, lattice 3161
 
  • D. M. Welsch, A. Lehrach, B. Lorentz, R. Maier, D. Prasuhn, R. Tölle
    FZJ, Jülich
  The High Energy Storage Ring (HESR) will be part of the future Facility for Antiproton and Ion Research (FAIR) located at GSI in Darmstadt, Germany. The HESR will be operated with antiprotons in the momentum range from 1.5 to 15 GeV/c, which makes a long beam life time and a minimum of particle losses crucial. This and the demanding requirements of the PANDA experiment lead to the necessity of a good orbit correction and an effective multipole compensation. We developed a closed orbit correction scheme and tested it with Monte Carlo simulations. We assigned different sets of angular and spatial errors to all elements (magnets, bpms, etc.) within the lattice of the HESR. For correction we applied the orbit response matrix method. We carried out investigations concerning higher-order multipoles and created a scheme for chromaticity correction and compensation of arising resonances utilising analytic formulae and dynamic aperture calculations. In this presentation we give an overview of the correction and compensation schemes and of the corresponding results.  
 
THPC102 Image Simulations on the ISIS Synchrotron simulation, vacuum, lattice, dipole 3215
 
  • B. G. Pine, C. M. Warsop
    STFC/RAL/ISIS, Chilton, Didcot, Oxon
  ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on a loss-limited 50 Hz proton synchrotron, which accelerates ~3·1013 ppp from 70 to 800 MeV, corresponding to mean beam powers of 0.2 MW. A significant proportion of beam loss is attributable to space charge effects. One such effect is the image field which forms in the beam pipe. Off-centre beams resulting from closed orbit errors generate fields, which can perturb the beam and cause loss. Of particular interest on ISIS is the rectangular, varying aperture, vacuum vessel, as compared with the more usual constant aperture circular or elliptical geometries. A new 2D space charge code, Set, was developed to study these effects. The code simulates the effects of space charge using a 2D particle-in-cell model of the beam distribution, including an appropriate treatment of the rectangular beam pipe, and details of the ISIS lattice. The effects of images on closed orbits, driving terms, and the evolution of beam distributions at ISIS operational intensities were explored.  
 
THPC120 Conceptual Design and Performance Estimation of The TPS Fast Orbit Feedback System feedback, power-supply, controls, vacuum 3263
 
  • P. C. Chiu, J. Chen, K. T. Hsu, K. H. Hu, C. H. Kuo
    NSRRC, Hsinchu
  A 3 GeV Synchrotron (TPS) is proposed in Taiwan. Its storage ring consists of 24 double-bend cells with 6-fold symmetry and the circumference is 518.4m. The report presents the initial design of the fast orbit feedback system (FOFB) for TPS. The system uses 168 BPMs and 168 correct magnets to stabilize global closed orbit at 10 kHz updated rate. The different subsystems are modeled: the BPM systems, the corrector magnet, vacuum chamber, and etc. The latency of the communication and computation is also studied. The preliminary calculation on the stability performance for the orbit feedback system is presented in the report. The FOFB is expected to achieve a submicron stability of the electron beam working at a bandwidth of at least 100 Hz.  
 
THPC131 On the Optimal Number of Eigenvectors for Orbit Correction feedback, quadrupole, storage-ring, simulation 3295
 
  • I. Pinayev, M. G. Fedurin
    BNL, Upton, New York
  The singular value decomposition method is widely used for orbit correction in the storage rings. It is a powerful tool for inverting of the usually rectangular response matrices, which usually have rectangular form. Another advantage is flexibility to choose number of eigenvectors for calculation of required strengths of orbit correctors. In particular, by reduction in number of eigenvectors one can average over ensemble noise in the beam position monitors. A theoretical approach as well as experimental results on the NSLS VUV ring are presented.  
 
THPC140 The Performance of a Fast Closed Orbit Feedback System with Combined Fast and Slow Correctors feedback, power-supply, simulation, vacuum 3315
 
  • L.-H. Yu, S. Krinsky, O. Singh, F. J. Willeke
    BNL, Upton, Long Island, New York
  For NSLSII closed orbit feedback system, in order to reduce the noise caused by the step changes of the power supplies in the feedback system, the angular kick corresponding to the last bit of the power supplies for the fast correctors must be smaller than 3 nrad*. On the other hand, in order to carry out closed orbit alignment or orbit correction after a long term drift, we need strong correctors with 0.8 mrad kick strength*. In order to avoid the requirement of correctors with both large strength and very small minimum step size, we consider separate sets of slow correctors with large strength and fast correctors with smaller maximum strength. In order to avoid fast and slow feedback systems working in parallel, and avoid the possible interaction between two feedback systems, we consider the possibility of using only one fast feedback system with slow correctors periodically removing the DC components of the fast correctors so that the DC components in fast feedback system would not accumulate to reach saturation even after a large long term drift of the closed orbit motion. We report on simulation of the performance of this combined system for NSLSII in this paper.

* NSLSII Preliminary Design Report (2007)

 
 
THPP005 Orbit Distortion and its Correction in a Non-scaling FFAG acceleration, quadrupole, injection, lattice 3383
 
  • D. J. Kelliher, S. Machida
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon
  The wide variation in betatron tune over a rapid acceleration time presents particular difficulties in orbit correction in a non-scaling FFAG. Due to the fact that the phase advance between an error source and the corrector magnets varies during acceleration, and assuming that the corrector magnets' strengths must be constant during the short acceleration period, it is clear that conventional harmonic correction is ineffective. We propose a method to determine the magnet and BPM misalignments in a non-scaling FFAG. By running the beam at fixed energy over many turns, and assuming no other error sources exist, the BPM measurements allow the misalignments to be calculated (assuming that there are as many BPMs as error sources). We show that it is also possible to calculate the BPM misalignment error if the beam is run at two fixed energies. This is due to a characteristic property of non-scaling FFAGs - the variation of the phase shift, and hence the response of the BPM measurements to magnet misalignments, with momentum. Having estimated the magnet misalignments, a local correction is made and a tracking study carried out to calculate the reduction in orbit distortion that results.  
 
THPP007 Six-sector FFAG Ring to Demonstrate Bunch Rotation for PRISM simulation, target, vacuum, injection 3389
 
  • A. Sato, M. Aoki, S. Araki, Y. Arimoto, Y. Eguchi, K. Hirota, I. Itahashi, Y. Kuno, Y. Kuriyama, Y. Nakanishi, M. Y. Yoshida
    Osaka University, Osaka
  • Y. Iwashita
    Kyoto ICR, Uji, Kyoto
  • A. Kurup
    Imperial College of Science and Technology, Department of Physics, London
  • Y. Mori
    KURRI, Osaka
  • C. Ohmori
    KEK, Ibaraki
  A monochromatic muon beam is one of the most important requirements to improve a sensitivity of mu-e conversion experiments. In the PRISM project, which searches for mu-e conversion at a sensitivity of BR~10-18, makes such muon beams by using a bunch rotation technique in an FFAG ring. To demonstrate the bunch rotation, a FFAG ring has been constructed in RCNP, Osaka. The ring has six FFAG magnets and one RF cavity. Alpha particles from a radioactive isotope 241Am will circulate in the ring for the demonstration of bunch rotation.  
 
THPP096 Injection Optimisation on the ISIS Synchrotron injection, synchrotron, betatron, 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.