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scattering

 
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MOPCH026 A Biperiodic X-band RF Cavity for SPARC coupling, simulation, controls, SLAC 101
 
  • L. Ficcadenti, M.E. Esposito, A. Mostacci, L. Palumbo
    Rome University La Sapienza, Roma
  • D. Alesini, B. Spataro
    INFN/LNF, Frascati (Roma)
  • A. Bacci
    INFN-Milano, Milano
  The Frascati photo-injector SPARC (Pulsed Self Amplified Coherent Radiation Source) will be equipped with an X-band RF cavity for linearizing emittance to enhance bunch compression and for reducing bunch longitudinal energy spread. A biperiodic cavity working on the pi/2-mode offers some advantages in comparison to a conventional (periodic) cavity despite the need of accurate machining. A copper prototype made of 17 separated cells has been built following numerical simulation. In this paper we report on preliminary measurements of its RF properties. The main characteristics of the cooling system for the final device are also addressed.  
 
MOPCH056 Development of High Brightness Soft X-ray Source Based on Inverse Compton Scattering laser, electron, background, MCP 166
 
  • R. Moriyama, Y. Hama, K. Hidume, A. Oshima, T. Saito, K. Sakaue, M. Washio
    RISE, Tokyo
  • H. Hayano, J. Urakawa
    KEK, Ibaraki
  • S. Kashiwagi
    ISIR, Osaka
  • R. Kuroda
    AIST, Tsukuba, Ibaraki
  Compact soft X-ray source based on inverse compton scattering have been developed at Waseda University. Using 1047nm laser light from Nd:YLF laser scattered off 4.2MeV electron beam generated from a photo-cathode rf-gun, we have already suceeded to generate the soft X-ray. The energy of this x-ray is included in the part of water window, in which absorption of water is much less than that of moleculars that organize a living body. Furthermore, this x-ray source has other features such as short pulse, proportional mono-energy and energy variableness. Because of these tures, the application to the biological microscope have been expected. However, the flux of x-ray is not satisfied for the biological microscope application. Therefore, to multiply a soft X-ray flux, we utilized multi-pass amplifier for the laser light and improved a collision chamber. In this conference, we will report the experimental results and future plans.  
 
MOPCH122 Realistic Beam Loss Estimation from the Nuclear Scattering at the RCS Charge-exchange Foil injection, beam-losses, simulation, target 333
 
  • P.K. Saha, H. Hotchi, Y. Irie, F. Noda
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • H. Harada
    Hiroshima University, Higashi-Hiroshima
  We have developed simulation tools for the realistic beam loss estimation at the RCS(rapid cycling synchrotron) of J-PARC(Japan Proton Accelerator Research Complex). The present simulation concerns an accurate estimation of the beam loss caused by the nuclear scattering at the charge-exchange foil during the multi turn injection period. It can also figure out the loss point in the ring, so would become very useful for the maintenance and optimization as well. The simulation code GEANT together with the SAD(Strategic Accelerator Design) have been used for the present purpose. In this paper, detail simulation method including the result will be discussed.  
 
MOPCH189 Calculating the Muon Cooling within a MICE Liquid Absorber emittance, cryogenics, factory, focusing 502
 
  • M.A. Green, S.P. Virostek
    LBNL, Berkeley, California
  • S.Q. Yang
    OXFORDphysics, Oxford, Oxon
  The key elements of the Muon Ionization Cooling Experiment (MICE) cooling channel are the absorbers that are a part of the MICE absorber focus coil modules (AFC modules). The boundaries of room temperature solid absorbers are well defined. The density of most solid absorber materials is also well understood. The properties of solid absorber are most certainly understood to 0.3 percent. The MICE liquid absorbers are different in that their dimensions are a function of the absorber temperature and the fluid pressure within the absorber. The second element in the liquid absorber is the variability of the liquid density with temperature and pressure. While one can determine the absorber boundary within 0.3 percent, the determination of the liquid density within 0.3 percent is more difficult (particularly with liquid helium in the absorber). This report presents a method of calculating absorber boundary and the cooling performance of the MICE absorbers as a function of fluid temperature and pressure.  
 
MOPLS013 The Roman Pot for LHC vacuum, LHC, optics, radiation 562
 
  • M. Oriunno, M. Deile, K. Eggert, J.-M. Lacroix, S.J. Mathot, E.P. Noschis, R. Perret, E.R. Radermacher, G. Ruggiero
    CERN, Geneva
  The LHC machine will be equipped with Roman Pot stations by the TOTEM experiment to measure the pp total cross section and to study the elastic scattering and the diffraction physics processes. TOTEM needs to bring the pots, equipped with cold micro-strip silicon detectors, as a close as possible to the high intensity beam of LHC. Because of the special optics required by TOTEM, the beam has a transversal size of only 80 microns at the Roman pot locations. Safety considerations for the machine protection set the limit to 10 ?, i.e. 800 μm. Such unprecedented parameters, together with the issues of the Ultra High Vacuum and the RF compatibility, and the harsh radiation environment, have requested a design for the Roman Pot system, which is compliant with the LHC requirements and operations. To better meet also the challenging requirements of TOTEM, a technology development of a thin window has been pursued and a flatness of less than 50 μm has been obtained by brazing foil of 150 μm thicknesses. A prototype of the Roman Pot and of the thin window box have been manufactured and tested. We describe the main issues of the final design and the results of the preliminary tests.  
 
MOPLS014 Lifetime Limit from Nuclear Intra-bunch Scattering for High-energy Hadron Beams LHC, proton, ion, injection 565
 
  • F. Zimmermann, H.-H. Braun, F. Ruggiero
    CERN, Geneva
  We derive an approximate expression for the nuclear scattering rate inside a bunched hadron beam. Application to the LHC suggests that the loss rate due to nuclear scattering can be significant in high-energy proton or ion storage rings.  
 
TUPCH073 Study of Beam Energy Spread at the VEPP-4M betatron, diagnostics, synchrotron, collider 1178
 
  • O.I. Meshkov, V. F. Gurko, A.D. Khilchenko, V. Kiselev, N.Yu. Muchnoi, A.N. Selivanov, V.V. Smaluk, A. N. Zhuravlev
    BINP SB RAS, Novosibirsk
  The knowledge of beam energy spread is necessary for the experimental program of the VEPP-4M collider. In this report we discuss the application of optical diagnostics for measurement of this value. The diagnostics is based on multi-anode photomultiplier and provides information about betatron and betetron frequencies of electron beam*. The beam energy spread is derived from the spectra of synchrotron oscillation. The results, obtained with this method, are compared with data, provided by Compton backscattering technique.

*O. I. Meshkov et al. Application of the beam profile monitor for VEPP-4M tuning. Proc. of DIPAC '05, June 6 - 8, 2005, Lyon, France, POM008.

 
 
TUPCH074 Fast and Precise Beam Energy Monitor Based on the Compton Backscattering at the VEPP-4M Collider photon, electron, laser, collider 1181
 
  • N.Yu. Muchnoi, S.A. Nikitin, V.N. Zhilich
    BINP SB RAS, Novosibirsk
  Accurate knowledge of the colliding beam energies is essential for the current experiments with the KEDR \cite{KEDR} detector at the VEPP-4M collider. Now the experimental activity is focused on the new precise measurement of the tau-lepton mass by studying the behavior of the tau production cross-section near the reaction threshold. To achieve the desired quality of the experiment, an on-line beam energy monitoring by the Compton backscattering of laser light was performed. This approach is found to be a very good supplement to rare energy calibrations by the resonant depolarization technique, saving the beam time for luminosity runs. The method itself does not require electron beam polarization and additionally allows one to measure the electron beam energy spread. The achieved accuracy of the method in the beam energy range 1.7–1.9 GeV is 60 keV.  
 
TUPCH075 Dependence of the Electron Beam Polarization Effect in the Intra-beam Scattering Rate on the Vertical Beam Emittance polarization, electron, emittance, coupling 1184
 
  • S.A. Nikitin, I.B. Nikolaev
    BINP SB RAS, Novosibirsk
  Measurement of the Intra-beam scattering rate is applied in the resonant depolarization technique to detect beam polarization in electron/positron storage rings. A depolarization jump in the counting rate of scattering particles occurs at the instant when the beam becomes unpolarized due to fulfillment of the external spin resonance condition. The magnitude of the jump depends on polarization quadratically. It also depends on some other beam parameters as well as the position of counters relative to the beam orbit. A larger jump implies higher accuracy in absolute calibration of particle energy because the latter is proportional to the spin precession frequency. In contrast to an ordinary one-dimensional approach, we calculate the magnitude of jump subject to, among other things, the vertical component of relative velocity in particle collisions inside the beam. For this purpose, the transverse momentum distribution function is properly modified. Calculations performed for the VEPP-4M storage ring-collider show that the jump may depend significantly on the ratio between the vertical and radial beam emittance. We present results of our recent experiments on study of this dependence.  
 
TUPCH098 Antiproton Momentum Distributions as a Measure of Electron Cooling Force at the Fermilab Recycler electron, antiproton, emittance, betatron 1241
 
  • D.R. Broemmelsiek, S. Nagaitsev
    Fermilab, Batavia, Illinois
  The Fermilab Recycler is a fixed 8GeV kinetic energy storage ring located in the Fermilab Main Injector tunnel near the ceiling. Electron cooling of high-energy antiprotons has recently been demonstrated at the Recycler. Antiproton beam Schottky signals were used to measure the antiproton momentum distribution at equilibrium between a calibrated broadband diffusion source and electron cooling. The large Recycler momentum aperture, the dependence of the electron cooling force as a function of the antiproton momentum deviation and the calibrated diffusion source combine to give a unique spectral measurement of the antiproton momentum beam distribution.  
 
TUPCH165 Compact Single-channel Ka-band SLED-II Pulse Compressor coupling, LEFT, CLIC, linac 1411
 
  • S.V. Kuzikov, S.V. Kuzikov, M.E. Plotkin, A.A. Vikharev
    Omega-P, Inc., New Haven, Connecticut
  • J.L. Hirshfield
    Yale University, Physics Department, New Haven, CT
  Basic studies of factors that limit RF fields in warm accelerator structures require experiments at RF power levels that can only be produced from an intense drive beam, as with CLIC studies, or using pulse compression of output pulses from the RF source. This latter approach is being implemented to compress output pulses from the Yale/Omega-P 34-GHz magnicon to produce ~100-200 MW, 100 ns pulses. A new approach for passive pulse compression is described that uses a SLED-II-type circuit operating with axisymmetrical modes of the TE0n type that requires only a single channel instead of the usual double channel scheme. This allows avoidance of a 3-dB coupler and need for simultaneous fine tuning of two channels. Calculations show that with this device at 34 GHz one can anticipate a power gain of 3.3:1, and an efficiency of 66% for a 100 ns wide output pulse, taking into account losses and a realistic 50-ns long 180 degrees phase flip.  
 
TUPLS008 A new HOM Water Cooled Absorber for the PEP-II B-factory Low Energy Ring dipole, quadrupole, coupling, impedance 1499
 
  • M. Kosovsky, N. Kurita, A. Novokhatski, J. Seeman, S.P. Weathersby
    SLAC, Menlo Park, California
  At high currents and small bunch lengths beam line components in the PEP-II B-factory experience RF induced heating from higher order RF modes (HOMs) produced by scattered intense beam fields. A design for a passive HOM water cooled absorber for the PEP-II low energy ring is presented. This device is to be situated near HOM producing beamline components such as collimators and provide HOM damping for dipole and quadrupole modes while minimizing impedance to the beam. We present a method of optimizing the impedance characteristics of such devices through the evaluation of loss factors and absorber effectiveness for specific modes using scattering parameter and wakefield analysis.  
 
TUPLS016 Characterization of Crystals for Steering of Protons through Channelling in Hadronic Accelerators proton, lattice, CERN, extraction 1523
 
  • V. Guidi, S. Baricordi, M. Fiorini, G. Martinelli, A. Mazzolari, E. Milan
    UNIFE, Ferrara
  • E. Boscolo Marchi, G. Della Mea, R. Milan, S. Todros, A. Vomiero
    INFN/LNL, Legnaro, Padova
  • A. Carnera, D. De Salvador, A. Sambo
    Univ. degli Studi di Padova, Padova
  • Y.A. Chesnokov
    IHEP Protvino, Protvino, Moscow Region
  • Yu.M. Ivanov
    PNPI, Gatchina, Leningrad District
  • W. Scandale
    CERN, Geneva
  Channeling of relativistic particles through a crystal may be useful for many applications in accelerators, and particularly for collimation in hadronic colliders. Efficiency proved to be dependent on the state of the crystal surface and hence on the method used for preparation. We investigated the morphology and structure of the surface of the samples that have been used in accelerators with high efficiency. We found that crystal fabrication by only mechanical methods (dicing, lapping, and others) leads to a superficial damaged layer, which is correlated to performance limitation in accelerators. A planar chemical etching was studied and applied in order to remove the superficial damaged layer. RBS analysis with low-energy protons highlighted better crystal perfection at surface, as a result of the etching. Finally, measurement with 70-GeV protons at IHEP demonstrated a superior performance of the chemically cleaned crystals with respect to conventional samples. A protocol for preparation and characterization of crystal for channelling has been developed, which may be of interest for reliable operation with crystals in accelerators.  
 
TUPLS021 First Observation of Proton Reflection from Bent Crystals proton, lattice, CERN, collimation 1535
 
  • W. Scandale
    CERN, Geneva
  • V.T. Baranov, V.N. Chepegin, Y.A. Chesnokov
    IHEP Protvino, Protvino, Moscow Region
  • Yu.A. Gavrikov, Yu.M. Ivanov, L. P. Lapina, A.A. Petrunin, A.I. Schetkovsky, V. Skorobogatov, A. V. Zhelamkov
    PNPI, Gatchina, Leningrad District
  • V. Guidi
    UNIFE, Ferrara
  • A. Vomiero
    INFN/LNL, Legnaro, Padova
  We recently suggested using short bent crystals as primary collimators in a two-stage cleaning system for hadron colliders, with the aim of providing larger impact parameters in the secondary bulk absorber, through coherent beam-halo deflection*. Tests with crystals a few mm long, performed with 70 GeV proton beams at IEHP in Protvino, showed a channeling efficiency exceeding 85%. We also observed disturbing phenomena such as dechanneling at large impact angle, insufficient bending induced by volume capture inside the crystal, multiple scattering of non-channeled protons and, for the first time, a proton flux reflected by the crystalline planes. Indeed, protons with a tangent path to the curved planes somewhere inside the crystal itself are deflected in the opposite direction with respect to the channeled particles, with an angle almost twice as large as the critical angle. This effect, up to now only predicted by computer simulations**, produces a flux of particles in the wrong direction with respect to the absorber, which may hamper the collimation efficiency if neglected.

*A. Afonin et al. PhysRevLett.87.094802(2001).**A. M. Taratin and S.A.Vorobiev, Phys.Lett. A119(1987)425.

 
 
WEOAPA03 MICE Overview - Physics Goals and Prospects emittance, focusing, radiation, photon 1870
 
  • M. Yoshida
    Osaka University, Osaka
  Ionization cooling, a technique in which muon beam is passed through a series of absorbers and followed by RF-acceleration, is a proposed method for cooling muon beam, i.e., phase-space reduction. The international Muon Ionisation Cooling Experiment (MICE), which will construct and operate a realistic cooling channel and measure the beam cooling performance, is the first essential step towardsrealization of nutrino factories and eventually muon colliders based on intense muon sources. The MICE have got approved to be constructedin Rutherford Appleton Laboratory (RAL) and the fist beam commissioning is scheduled in 2007. The physics goal and future prospects of the MICE together with the beamline and the instruments which is now being built will be described.  
slides icon Transparencies
 
WEPCH111 Time Domain Radiation of a Gaussian Charge Sheet Passing a Slit in a Conducting Screen radiation, ITY 2173
 
  • M. Filtz, H. Henke
    TET, Berlin
  A semi-analytical method is proposed to calculate in time-domain the radiation of a relativistic Gaussian charge sheet travelling parallel to a slotted conducting screen. The method is based on transient line current elements as basis functions which have a triangular time dependence. Making use of duality magnetic current elements are used in the slot region. Radiation fields are shown and the transverse kick received by a test charge is given. The dual problem, the scattering of the fields at a conducting strip, is also treated. The main purpose of the paper is to present an effective algorithm which is easy to implement for computing and visualising plane scattering and diffraction problems in time domain.  
 
WEPCH119 Beam Performance with Internal Targets in the High-energy Storage Ring (HESR) target, beam-losses, luminosity, antiproton 2197
 
  • A. Lehrach, R. Maier, D. Prasuhn
    FZJ, Jülich
  • O. Boine-Frankenheim, R.W. Hasse
    GSI, Darmstadt
  • F. Hinterberger
    Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, Bonn
  The High-energy Storage Ring of the future International Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt is planned as an antiproton synchrotron storage ring in the momentum range of 1.5 to 15 GeV/c. An important feature of HESR is the combination of phase space cooled beams and dense internal targets (e.g., pellet targets), which results in demanding beam parameter requirements for two operation modes: high luminosity mode with peak luminosities of up to 2·1032 cm-2 s-1, and high resolution mode with a momentum spread down to 10-5, respectively. The beam cooling equilibrium and beam loss with internal target interaction is analyzed. Rate equations are used to predict the rms equilibrium beam parameters. The cooling and intra-beam scattering rate coefficients are obtained from simplified models. Energy loss straggling in the target and the associated beam loss are analyzed analytically assuming a thin target. A longitudinal kinetic simulation code is used to study the evolution of the momentum distribution in coasting and bunched beam. The analytic expressions for the target induced momentum tail are found in good agreement with the simulation results.

*A. Lehrach et al. Beam Performance and Luminosity Limitations in the High-Energy Storage Ring (HESR), Nuclear Inst. and Methods in Physics Research, A44704 (2006).

 
 
WEPCH124 BDSIM - Beamline Simulation Toolkit Based on Geant4 simulation, quadrupole, electron, CLIC 2212
 
  • I.V. Agapov, G.A. Blair, J. Carter
    Royal Holloway, University of London, Surrey
  • O. Dadoun
    LAL, Orsay
  BDSIM is a code that combines accelerator-style particle tracking with traditional Geant-style tracking based on Runge-Kutta techniques. This approach means that particle beams can be tracked efficiently when inside the beampipe, while also enabling full Geant4 processes when beam-particles interact with beamline apertures. Tracking of the resulting secondary particles is automatic. The code is described, including a new MAD-style interface and new geometry description, and key performance parameters are listed.  
 
WEPCH126 Issues in Modelling of Negative Ion Extraction ion, plasma, extraction, electron 2218
 
  • M. Cavenago
    INFN/LNL, Legnaro, Padova
  • V. Antoni, F. Sattin
    CNR/RFX, Padova
  In the context of negative ion sources proposed for neutral beam injectors for tokamaks, halo of the extracted beam is typically large (about 10 %) and optimum shape of the multiaperture extraction electrode is a matter of research. Present designs range from an aperture angle of 45 degree (low current, convergent beam) to 90 degrees (flat electrode, high current, large divergence and halo). Two major difficulties of the beam extraction modelling are here discussed. First, the generation processes of negative ion show some shortcomings: volume production seems low; wall production is large, but ions have wrong directions and/or large nonuniformity in current density; elastic scattering of wall generated ions into the extraction direction must compete with mutual neutralization. Second, the plasma sheath charge has to be negative on the extraction hole surface and positive on the nearby wall surface, which enhances beam aberration near hole edge. After discussing limitation of existing codes and model, result from an ad hoc code are discussed. Also 2D equation for the selfconsistent electrostatic field can be written and implemented into a multiphysics general purpose program.  
 
WEPCH136 Monte Carlo Simulation Model of Internal Pellet Targets target, simulation, injection, storage-ring 2239
 
  • O.A. Bezshyyko, K.A. Bezshyyko, I.M. Kadenko, R.V. Yermolenko
    National Taras Shevchenko University of Kyiv, The Faculty of Physics, Kyiv
  • A. Dolinskii
    NASU/INR, Kiev
  • V.G. Ziemann
    UU/ISV, Uppsala
  We develop a numerical model of a pellet target and use it for Monte Carlo simulations of the interaction of a circulating beam with a pellet target. Real geometry details of the pellet beam and the beam are taken into account. We emphasize the role of tails of non-Gaussian distributions for transverse scattering and energy loss. These effects are especially important for simultaneous calculations of electron cooling, intrabeam scattering and target influence. Black-box algorithms for the generation of automatic nonuniform random variate distributions are used for the effective time averaging of scattering angle and energy loss distributions.  
 
WEPCH167 Study of Scatterer Method to Compensate Asymmetric Distribution of Slowly Extracted Beam at HIMAC Synchrotron simulation, extraction, emittance, synchrotron 2322
 
  • T. Furukawa, K. Noda, S. Sato, S. Shibuya, E. Takada, M. Torikoshi, S. Yamada
    NIRS, Chiba-shi
  In the medical use of the ion beam, the following characteristics of the beam are preferred: 1) Symmetric Gaussian beam profile is convenient for the scanning irradiation. 2) In the rotating gantry system, the symmetric beam condition can realize no-correlation between the beam profiles and the rotation angles of the gantry. However, the slowly extracted beam has asymmetric distribution in the phase-space and a difference between the horizontal emittance and vertical one. Thus, we have proposed the thin scatterer method to compensate the phase-space distribution of the slowly extracted beam, although the emittance is enlarged by scattering. As a result of particle tracking and experiment, it was verified that the asymmetric distribution was compensated by very small scattering angle. It was also simulated that this scatterer method can realize the symmetric beam condition for the rotating gantry. In this paper, these results of asymmetry compensation for the slow-extraction at HIMAC is presented.  
 
WEPLS019 Parameters for Absorber-based Reverse Emittance Exchange of Muon Beams emittance, collider, acceleration, betatron 2433
 
  • R.P. Johnson
    Muons, Inc, Batavia
  • Y.S. Derbenev
    Jefferson Lab, Newport News, Virginia
  The normalized longitudinal emittance of a muon beam after six-dimensional ionization cooling appears very small compared to the value that could be utilized or maintained after acceleration to muon collider energy. This circumstance offers the possibility for further reduction of the transverse emittance by introducing absorber-based reverse emittance exchange (REMEX) between longitudinal and transverse degrees of freedom before acceleration to high energy. REMEX follows Parametric-resonance Ionization Cooling and is accomplished in two stages. In the first stage the beam is stretched to fill the RF bucket at the initial cooling energy. In the second stage the beam is accelerated to about 2.5 GeV, where energy straggling begins to limit the absorber technique, and stretched again. The potential transverse emittance reduction and the intrinsic limitations of the REMEX technique have been analyzed earlier. In this report, we describe the required beam transport and RF parameters needed to achieve the maximum REMEX effect.  
 
WEPLS045 Study on Low-energy Positron Polarimetry positron, electron, target, photon 2475
 
  • A. Schaelicke, K. Laihem, S. Riemann, A. Ushakov
    DESY Zeuthen, Zeuthen
  • R. Dollan, Th. Lohse
    Humboldt University Berlin, Institut für Physik, Berlin
  For the design of the International Linear Collider (ILC) a polarised positron source based on a helical undulator system has been proposed. In order to optimise the positron beam, i.e., to ensure high intensity as well as high degree of polarisation, a measurement of the polarisation close to the positron creation point is envisaged. In this contribution methods to determine the positron polarisation at low energies are investigated. These studies are based on simulations with an extended version of Geant4, which allows the tracking of polarised particles taking into account the spin effects.  
 
WEPLS108 High Field Solenoid Magnets for Muon Cooling TESLA, collider, emittance, luminosity 2634
 
  • S.A. Kahn, M. Alsharo'a, P.M. Hanlet, R.P. Johnson, M. Kuchnir, D.J. Newsham
    Muons, Inc, Batavia
  • R.C. Gupta, R. Palmer, E. Willen
    BNL, Upton, Long Island, New York
  Magnets made with high-temperature superconducting (HTS) coils operating at low temperatures have the potential to produce extremely high fields for use in beam lines and accelerators. The specific application of interest that we are proposing is to use a very high field (of the order of 50 Tesla) solenoid to provide a very small beta region for the final stages of cooling for a muon collider. With the commercial availability of HTS tape based on BSCCO technology with high current carrying capacity at 4.2 K, very high field solenoid magnets should be possible. In this paper we will evaluate the technical issues associated with building this magnet. In particular we will address how to mitigate the high Lorentz stresses associated with this high field magnet.  
 
THPCH004 Space Charge Induced Resonance Trapping in High-intensity Synchrotrons beam-losses, resonance, synchrotron, space-charge 2790
 
  • G. Franchetti, I. Hofmann
    GSI, Darmstadt
  With the recent development of high-intensity circular accelerators, the simultaneous presence of space charge and lattice nonlinearities has gained special attention as possible source of beam loss. In this paper we present our understanding of the role of space charge and synchrotron motion as well as chromaticity for trapping of particles into the islands of nonlinear reonances. We show that the three effects combined can lead to significant beam loss, where each individual effect leads to small or negligible loss. We apply our findings to the SIS100 of the FAIR project, where the main source of field nonlinearities stems from the pulsed super-conducting dipoles, and the beam dynamics challenge is an extended storage at the injection flat-bottom, over almost one second, together with a relatively large space charge tune shift.  
 
THPCH019 Halo and Tail Generation Studies for Linear Colliders simulation, CLIC, linac, collimation 2823
 
  • L. Neukermans, H. Burkhardt
    CERN, Geneva
  • J. Resta-López
    IFIC, Valencia
  Halo particles in linear colliders can result in significant losses and serious background which may reduce the overall performances. We present a study of various halo generation processes with numerical estimates. The aim is to allow to predict and minimize the halo throughout the accelerator chain including the final focus up to the experimental detectors. We include estimates for the planned CLIC beam line.  
 
THPCH027 An Experimental Proposal to Study Heavy-ion Cooling in the AGS due to Beam Gas or the Intrabeam Scattering ion, electron, AGS, RHIC 2838
 
  • D. Trbojevic, L. Ahrens, J. Beebe-Wang, M. Blaskiewicz, J.M. Brennan, W.W. MacKay, G. Parzen, T. Roser
    BNL, Upton, Long Island, New York
  Low emittance of not-fully-stripped gold(Z=79) Au+77 Helium-like ion beams from the AGS (Alternating Gradient Synchrotron) could be attributed to the cooling phenomenon due to inelastic intrabeam scattering [1]. The low emittance gold beams have always been observed at injection in the Relativistic Heavy Ion Collider (RHIC). There have been previous attempts to attribute the low emittance to a cooling due to the exchange of energy between ions during the inelastic intrabeam scattering. The Fano-Lichten theory[2] of electron promotion might be applied during inelastic collisions between helium like gold ions in the AGS. During collisions if the ion energy is large enough, a quasi-molecule could be formed, and electron excitation could occur. During de-excitation of electrons, photons are emitted and a loss of total bunch energy could occur. This would lead to smaller beam size. We propose to inject gold ions with two missing electrons into RHIC at injection energy and study the beam behavior with bunched and de-bunched beam, varying the RF voltage and the beam intensity. If the "cooling" is observed additional.  
 
THPCH053 Numerical and Experimental Study of Cooling-stacking Injection in HIMAC Synchrotron ion, injection, electron, simulation 2907
 
  • E. Syresin
    JINR, Dubna, Moscow Region
  • K. Noda
    NIRS, Chiba-shi
  • S. Shibuya
    AEC, Chiba
  • T. Uesugi
    KEK, Ibaraki
  The cooling-stacking injection at the HIMAC synchrotron was used to increase the intensity of Ar18+ ion beam. The beam stacking was realized in a horizontal free phase-space, which was created by the HIMAC electron cooler. The stack intensity of (1.5~2.5)·109 ppp was accumulated at an injection intensity of (0.3~1.0)e9. The stack intensity was limitted by the ion lifetime. A peculiarity of present cooling-stacking experiments is related to lifetime difference by a factor of 2~3 of the stack and injected ions. The lifetime of stack ions is determined by vacuum pressure. The new injected ions were slowly lost at multiple scattering on residual gas atoms at diffusion heating in the vertical direction caused by the acceptance of 30pi-mm-mrad and a reduction of cooling force at large betatron amplitudes. The results of numerical simulations and experimental study of cooling-stacking injection on the HIMAC synchrotron are presented.  
 
THPCH179 High Power Cavity Combiner for RF Amplifiers simulation, electron, storage-ring, coupling 3215
 
  • F. Pérez, B. B. Baricevic, D. Einfeld, P. Sanchez
    ALBA, Bellaterra
  • J.P. Buge, M.L. Langlois, G. Peillex-Delphe
    TED, Thonon
  A new approach of RF power combination has been developed for the ALBA Storage Ring RF system: a three-port high power Cavity Combiner (CaCo). A prototype has been successfully built and tested in Thales Electron Devices, Thonon, France. The final goal is to combine the power of two 80 kW IOTs at 500 MHz in order to provide a total output power of 160 kW. In this paper, a summary of the analytical and simulation analysis of the expected behaviour is given. In basis of that, the decided geometric constraints and the final design configuration chosen for the prototype production are explained. Low power test results and matching, and finally the high power test performances, are shown. As a conclusion, the RF system of the ALBA Storage Ring will incorporate the CaCo concept to obtain the needed power per cavity from the combination of two IOTs.  
 
THPLS044 Preliminary Experiment of the Thomson Scattering X-ray Source at Tsinghua University laser, electron, photon, linac 3386
 
  • Y.-C. Du, Cheng. Cheng. Cheng, Q. Du, Du.Taibin. Du, W.-H. Huang, Y. Lin, C.-X. Tang, S. Zheng
    TUB, Beijing
  A preliminary experiment of the Thomson scattering x-ray source is being planned and constructed to generate short-pulsed, tunable x-rays in the range of ~4.5 kev by Thomson scattering of laser photons from a relativistic electron beam. Laser photons of ? = 1064 nm are Thomson backscattered by a 16MeV electron beam from a 16MeV Backward Travelling Wave (BTW) electron linac. The laser is derived from a 2J,10ns Nd:YAG laser. The parameters of electron beam and laser have been measured. The simulated and experiment results are described in this paper.  
 
THPLS060 Lifetime and Acceptance at the SLS coupling, SLS, emittance, resonance 3421
 
  • A. Streun, Å. Andersson
    PSI, Villigen
  Beam lifetime at the storage ring of the Swiss Light Source (SLS) is limited by Touschek effect and elastic gas scattering. Both mechanism are affected by narrow gaps in the machine, elastic scattering directly by the vertical acceptance limitation, Touschek scattering via a possible restriction of lattice momentum acceptance due to coupling. The particle loss mechanism was explored by evaluations of lifetime as function of scraper position, chromaticity and emittance coupling.  
 
THPLS093 Status of the Photocathode RF Gun System at Tsinghua University gun, laser, cathode, BNL 3496
 
  • X. He, Cheng. Cheng. Cheng, Q. Du, Du.Taibin. Du, Y.-C. Du, W.-H. Huang, Y. Lin, C.-X. Tang, S. Zheng
    TUB, Beijing
  An S-band high gradient photocathode RF gun test stand is in construction process at Tsinghua University. The photocathode RF gun test stand is a primary step of a femtosecond hard x-ray source based on Thomson scattering. The photocathode RF gun system adopts Ti:Sap laser, BNL IV type 1.6 cell RF gun, compact compensation solenoid. We foresee to conduct investigations on the thermal emittance contribution of surface roughness, the emittance compensation technique under various laser shape and its application to Thomson scattering x-ray source. Except for the transportation of laser, correction of laser front for glazing incidence and laser pulse shaping system, other parts of the photocathode RF gun test stand have been constructed, and we can start very primary experiment on the RF gun test stand, such as measurements of dark current, QE and energy of the beam. The experimental results are reported.