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collimation

   
Paper Title Other Keywords Page
MOPCH048 Linac Coherent Light Source Electron Beam Collimation linac, undulator, LCLS, cathode 148
 
  • J. Wu, D. Dowell, P. Emma, C. Limborg-Deprey, J.F. Schmerge
    SLAC, Menlo Park, California
  This paper describes the design and preliminary simulations of the electron beam collimation system in the Linac Coherent Light Source (LCLS) linac. Dark current is expected from the gun and some of the accelerating cavities. Particle tracking of the expected dark current through the entire LCLS linac, from L0-linac exit to FEL undulator entrance, is used to estimate final particle extent in the undulator as well as expected beam loss at each collimator or aperture restriction. A table of collimators and aperture restrictions is listed along with halo particle loss results, which includes an estimate of average continuous beam power lost on each individual collimator. In addition, the transverse wakefield alignment tolerances are calculated for each collimator.  
 
MOPCH091 An Alternative Nonlinear Collimation System for the LHC LHC, sextupole, optics, insertion 246
 
  • J. Resta-López, R.W. Assmann, S. Redaelli, J. Resta-López, G. Robert-Demolaize, D. Schulte, F. Zimmermann
    CERN, Geneva
  • A. Faus-Golfe
    IFIC, Valencia
  The optics design of an alternative nonlinear collimation system for the LHC is presented. We discuss an optics scheme based on a single spoiler located in between a pair of skew sextupoles for betatron collimation. The nonlinear system allows opening up the collimator gaps and, thereby reduces the collimator impedance, which presently limits the LHC beam intensity. After placing secondary absorbers at optimum locations behind the spoiler, we analyze the beam losses and calculate the cleaning efficiency from tracking studies. The results are compared with those of the conventional linear collimation system.  
 
MOPCH124 Energy Deposition in Adjacent LHC Superconducting Magnets from Beam Loss at LHC Transfer Line Collimators LHC, simulation, beam-losses, proton 336
 
  • V. Kain, S. Beavan, Y. Kadi
    CERN, Geneva
  Injection intensities for the LHC are over an order of magnitude above the damage threshold. The collimation system in the two transfer lines is designed to dilute the beam sufficiently to avoid damage in case of accidental beam loss or mis-steered beam. To maximise the protection for the LHC most of the collimators are located in the last 300 m upstream of the injection point where the transfer lines approach the LHC machine. To study the issue of possible quenches following beam loss at the collimators the entire collimation section in one of the lines, TI 8, together with the adjacent part of the LHC has been modeled in FLUKA. The simulated energy deposition in the LHC for worst-case accidental losses as well as for losses expected during a normal filling is presented. The operational implications are discussed.  
 
MOPCH137 An Anti-symmetric Lattice for High Intensity Rapid-cycling Synchrotrons injection, lattice, dipole, synchrotron 369
 
  • J. Wei, Y.Y. Lee, S. Tepikian
    BNL, Upton, Long Island, New York
  • S.X. Fang, Q. Qin, J. Tang, S. Wang
    IHEP Beijing, Beijing
  • S. Machida, C.R. Prior, G. Rees
    CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
  Rapid cycling synchrotrons are used in many high power facilities like spallation neutron sources and proton drivers. In such accelerators, beam collimation plays a crucial role in reducing the uncontrolled beam loss. Furthermore, the injection and extraction section needs to reside in dispersion-free region to avoid couplings; a significant amount of drift space is needed to house the RF accelerating cavities; orbit, tune, and chromatic corrections are needed; long, uninterrupted straights are desired to ease injection tuning and to raise collimation efficiency. Finally, the machine circumference needs to be small to reduce construction costs. In this paper, we present a lattice designed to satisfy these needs. The lattice contains a drift created by a missing dipole near the peak dispersion to facilitate longitudinal collimation. The compact FODO arc allows easy orbit, tune, coupling, and chromatic correction. The doublet straight provides long uninterrupted straights. The four-fold lattice symmetry separates injection, extraction, and collimation to different straights. This lattice is chosen for the Beijing Spallation Neutron Source synchrotron.  
 
MOPLS007 Monitoring Heavy-ion Beam Losses in the LHC ion, proton, LHC, simulation 544
 
  • R. Bruce, G. Bellodi, H.-H. Braun, S.S. Gilardoni, J.M. Jowett
    CERN, Geneva
  The LHC beam loss monitor (BLM) system, primarily designed for proton operation, will survey particle losses and dump the beam if the loss rate exceeds a threshold expected to induce magnet quenches. Simulations of beam losses in the full magnet geometry allow us to compare the response of the BLMs to ion and proton losses and establish preliminary loss thresholds for quenches. Further simulations of beam losses caused by collimation and electromagnetic interactions peculiar to heavy ion collisions determine the positions of extra BLMs needed for ion operation in the LHC.  
 
MOPLS008 Beam Halo on the LHC TCDQ Diluter System and Thermal Load on the Downstream Superconducting Magnets LHC, simulation, insertion, superconducting-magnet 547
 
  • B. Goddard, R.W. Assmann, A. Presland, S. Redaelli, G. Robert-Demolaize, L. Sarchiapone, Th. Weiler, W.J.M. Weterings
    CERN, Geneva
  The moveable single-jawed graphite TCDQ diluter must be positioned very close to the circulating LHC beam in order to prevent damage to downstream components in the event of an unsynchronised beam abort. A two-jawed graphite TCS collimator forms part of the TCDQ system. The requirement to place the TCDQ and TCS jaws close to the beam means that the system can intercept a substantial beam halo load. Initial investigations indicated a worryingly high heat load on the Q4 coils. This paper presents the updated load cases, shielding and simulation geometry, and the results of simulations of the energy deposition in the TCDQ system and in the downstream superconducting Q4 magnet. The implications for the operation of the LHC are discussed.  
 
MOPLS074 Collimation Optimisation in the Beam Delivery System of the International Linear Collider lattice, betatron, linear-collider, collider 721
 
  • F. Jackson
    CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
  The collimation systems of the International Linear Collider (ILC) beam delivery system (BDS) must perform efficient removal of halo particles which lie outside the acceptable ranges of energy and spatial spread. An optimisation strategy is developed to improve the performance of the BDS collimation system. Primary considerations are the phase relationships between collimation systems and the final focus, and the overall bandwidth of the system.  
 
MOPLS082 Simulation of the ILC Collimation System Using BDSIM, MARS15 and STRUCT extraction, simulation, radiation, SLAC 744
 
  • J. Carter, I.V. Agapov, G.A. Blair, L. Deacon
    Royal Holloway, University of London, Surrey
  • A.I. Drozhdin, N.V. Mokhov
    Fermilab, Batavia, Illinois
  • Y. Nosochkov, A. Seryi
    SLAC, Menlo Park, California
  The simulation codes STRUCT, MARS15 and BDSIM are used to simulate in detail the collimation section of the ILC. A comparative study of the collimation system performance is performed, and the key radiation loads are calculated. Results for the latest ILC designs are presented together with their implications for future design iterations.  
 
MOPLS092 Efficient Collimation and Machine Protection for the Compact Linear Collider CLIC, linac, kicker, luminosity 768
 
  • R.W. Assmann, F. Zimmermann
    CERN, Geneva
  We present a new approach to machine protection and collimation in CLIC, separating these two functions: If emergency dumps in the linac protect the downstream beam line against drive-beam failures, the energy collimation only needs to clean the beam tails and can be compact. Overall, the length of the beam delivery system is significantly reduced.  
 
TUZBPA02 Crystal Channelling in Accelerators extraction, SPS, simulation, proton 945
 
  • V.M. Biryukov
    IHEP Protvino, Protvino, Moscow Region
  This presentation will begin with a description of the channelling of charged particles through crystals and the use of the channelling effect in accelerators etc. Results from use of crystals for beam deflection and extraction from synchrotrons in Russia, USA and CERN will also be given. Following this the potential advantage of crystals for collimation in high-energy high-intensity machines will be described.  
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TUODFI01 The Final Collimation System for the LHC LHC, insertion, impedance, proton 986
 
  • R.W. Assmann, O. Aberle, G. Bellodi, A. Bertarelli, C.B. Bracco, H.-H. Braun, M. Brugger, S. Calatroni, R. Chamizo, A. Dallocchio, B. Dehning, A. Ferrari, P. Gander, A. Grudiev, E.B. Holzer, J.-B. Jeanneret, J.M. Jimenez, M. Jonker, Y. Kadi, K. Kershaw, J. Lendaro, J. Lettry, R. Losito, M. Magistris, A.M. Masi, M. Mayer, E. Métral, R. Perret, C. Rathjen, S. Redaelli, G. Robert-Demolaize, S. Roesler, F. Ruggiero, M. Santana-Leitner, P. Sievers, M. Sobczak, E. Tsoulou, V. Vlachoudis, Th. Weiler
    CERN, Geneva
  • I. Baishev, I.L. Kurochkin
    IHEP Protvino, Protvino, Moscow Region
  The LHC collimation system has been re-designed over the last three years in order to address the unprecedented challenges that are faced with the 360 MJ beams at 7 TeV. The layout of the LHC has now been fixed and a final approach for collimation and cleaning has been adopted. In total 132 collimator locations have been reserved in the two LHC rings and can be installed in a phased approach. Ninety collimators of five different types will be available for initial beam operation. The system has been fully optimized for avoiding quenches of super-conducting magnets during beam losses and for sufficient survival of beamline components against radioactive dose. The phased approach for LHC collimation is described, the various collimators and their functionalities are explained, and the expected system performance is summarized.  
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TUPLS013 Protection of the LHC against Unsynchronised Beam Aborts LHC, kicker, extraction, monitoring 1514
 
  • B. Goddard, R.W. Assmann, E. Carlier, J.A. Uythoven, J. Wenninger, W.J.M. Weterings
    CERN, Geneva
  An unsynchronised beam abort in the LHC could cause major damage to other downstream accelerator components, in particular the extraction septum magnets, the experimental low-beta triplet magnet apertures and the tertiary collimators. Although the LHC beam dumping system includes design features to minimise their frequency, such unsynchronised aborts can arise from several sources and cannot be excluded. A system of protection devices comprising fixed and moveable passive diluters and collimators will be built to safely protect the downstream LHC aperture from the mis-directed bunches in case of such a failure. The sources of unsynchronised abort events are described, together with the requirements and design of the protection devices and their expected performance. The accompanying operational requirements and envisaged solutions are discussed, in particular the problem of ensuring the local orbit at the protection devices.  
 
TUPLS017 Optics Study for a Possible Crystal-based Collimation System for the LHC LHC, injection, proton, extraction 1526
 
  • R.W. Assmann, S. Redaelli, W. Scandale
    CERN, Geneva
  The use of bent crystals as primary collimators has been long proposed as an option to improve the cleaning efficiency of the LHC betatron and momentum collimation systems. These systems are presently based on two-stage collimation with amorphous scatterers and absorbers. Crystals are expected to help by channeling and extracting the halo particles with large angles, resulting in higher cleaning efficiency. Independent of ongoing studies for crystal qualifications (not reported here), it is important to understand the required deflection angles and the possible locations of absorbers for the LHC layout. Optics studies have been performed in order to specify the required angles for various LHC beam energies and possible locations of absorbers for the deflected halo beam. A possible layout for crystal-assisted collimation at the LHC is discussed, aiming for a solution which would not change the LHC layout but would make use of the existing collimator location.  
 
TUPLS018 Collimation Efficiency during Commissioning LHC, proton, insertion, betatron 1529
 
  • C.B. Bracco, R.W. Assmann, A. Ferrari, S. Redaelli, G. Robert-Demolaize, M. Santana-Leitner, V. Vlachoudis, Th. Weiler
    CERN, Geneva
  The design of the LHC collimation system naturally focused on understanding and maximizing the ultimate performance with all collimators in place. However, for the commissioning of the LHC it is important to analyze the collimation efficiency with certain subsets of collimators, with increased collimation gaps and relaxed set-up tolerances. Special studies on halo tracking and energy deposition have been performed in order to address this question. The expected cleaning performance and intensity limits are discussed for various collimation scenarios as they might be used during commissioning and initial operation of the LHC.  
 
TUPLS021 First Observation of Proton Reflection from Bent Crystals proton, scattering, lattice, CERN 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.

 
 
TUPLS022 Experimental Study of Crystal Channeling at CERN-SPS for Beam-halo Cleaning proton, LHC, alignment, SPS 1538
 
  • M. Fiorini, P. Dalpiaz, V. Guidi
    UNIFE, Ferrara
  • G. Ambrosi
    INFN-PG, Perugia
  • R.W. Assmann, I. Efthymiopoulos, L. Gatignon, W. Scandale
    CERN, Geneva
  • C. Biino
    INFN-Torino, Torino
  • Y.A. Chesnokov
    IHEP Protvino, Protvino, Moscow Region
  • Yu.M. Ivanov
    PNPI, Gatchina, Leningrad District
  • R. Santacesaria
    INFN-Roma, Roma
  • A.M. Taratin
    JINR, Dubna, Moscow Region
  • A. Vomiero
    INFN/LNL, Legnaro, Padova
  An efficient and robust collimation system is mandatory for any superconducting hadron collider, in particular for the LHC, which will store a beam of unprecedented high intensity and energy. The usage of highly efficient and short primary bent-crystal collimators might be a possibility for reaching nominal and ultimate LHC intensity. Over the last years, groups in Russia (St. Petersburg) and Italy (Ferrara) have developed crystal production methods, which considerably improve the crystal quality. In view of the crystal-collimation experiments at the Tevatron and of the potential improvement compared with the phas·10-1 LHC collimation system, considering the recent progress in crystal technology, we proposed experiments for crystal characterization in the SPS beam lines. Major objectives will be: 1) qualification of the new crystals to be used in the Tevatron; 2) measuring the channeling efficiency of long crystals with 1 mrad and/or 8 mrad bending angle; and 3) comparison of loss patterns around the ring for a crystal with one for amorphous material. In this paper we will report the progress towards the SPS experiment.  
 
TUPLS085 Stacking Simulations in the Beta-beam Decay Ring ion, injection, CERN, simulation 1699
 
  • S. Hancock
    CERN, Geneva
  • A. Chancé
    CEA, Gif-sur-Yvette
  The so-called beta-beam concept for accelerator-driven neutrino experiments envisages the production of a pure beam of electron neutrinos (or their antiparticles) through the beta-decay of radioactive ions circulating in a high-energy storage ring. An unprecedented number of ions must be collected in the decay ring and maintained in a few short bunches. Stacking is unavoidable to match the available source rates with this demand. A new stacking method makes use of off-momentum injection into the decay ring to approach the circulating beam without requiring ultra-fast injection elements, rotation in the longitudinal plane to bring the fresh bunches onto the central orbit and asymmetric merging to transport these ions into the centre of the large stack. Simulation results are presented for the complete repetitive stacking process for two candidate ion species of significantly different charge-to-mass ratio.  
 
TUPLS127 Permanent Deformation of the LHC Collimator Jaws Induced by Shock Beam Impact: an Analytical and Numerical Interpretation LHC, CERN, proton, simulation 1801
 
  • A. Bertarelli, O. Aberle, R.W. Assmann, A. Dallocchio, T. Kurtyka, M. Magistris, M. Mayer, M. Santana-Leitner
    CERN, Geneva
  Inspections carried out on jaws of the LHC collimator prototype, which underwent the 450 GeV robustness test in CERN TT40 extraction line, revealed no visible damage, except a permanent deformation of the jaw metal support of ~300 um. An explanation of this phenomenon is proposed in this paper. The temperature increase on the metal support induced by the thermal shock, though limited to ~70°C, led to a sudden expansion of the copper-based support which was partially prevented by the inertia of the material itself, thus generating compressive stresses exceeding the elastic limit of OFE-copper. An analytical assessment of the process, followed by a finite-element transient elasto-plastic analysis, is presented. Numerical results are in good agreement with measured data. In order to confirm this analysis, a special test on series production jaws, where OFE-copper has been replaced by Dispersion Strengthened Copper (Glidcop®), is scheduled for the second half of 2006.  
 
WEXFI03 Non-linear Collimation in Linear and Circular Colliders sextupole, optics, collider, betatron 1892
 
  • A. Faus-Golfe
    IFIC, Valencia
  • J. Resta-López, F. Zimmermann
    CERN, Geneva
  We describe the concept on nonlinear collimation of beam halo in linear and circular colliders. In particular we present the application of such a concept in two different cases: the energy collimation system for CLIC at 3 TeV c.m. energy and a betatron collimation system for LHC at 14 TeV c.m. energy. For each case, the system properties, like chromatic bandwidth, collimator survival and cleaning efficiency, are evaluated and compared with those of the corresponding linear collimation system.  
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WEPCH009 Loss Management in the Beta-beam Decay Ring dipole, ion, injection, lattice 1936
 
  • A. Chancé, J. Payet
    CEA, Gif-sur-Yvette
  The aim of the beta-beams is to produce pure electronic neutrino and anti-neutrino highly energetic beams, coming from beta radioactive disintegration of the 18Ne10+ and 6He2+, both at gamma = 100, directed towards experimental halls situated in the Frijus tunnel. The high intensity ion beams are stored in a ring, until the ions decay. Consequently, all the injected particles will be lost anywhere around the ring generating a high level of losses. In order to keep a constant neutrino flux, the losses due to the decay of the radioactive ions are compensated with regular injections. The new ion beam is then merged with the stored beam with a specific RF program Two sources of losses have been considered: -The beta-decay products: their magnetic rigidity being different from the reference one, they are bent differently and lost. -The losses during the injection merging process. The first one needs a particular ring design in order to insert appropriate beam stoppers at the right place. The second one needs a specific collimation system which allows beam longitudinal halo cleaning between two successive injections.  
 
WEPCH033 Single Particle Beam Dynamics Design of CSNS/RCS dipole, lattice, injection, extraction 1996
 
  • S. Wang, S.X. Fang, Q. Qin, J. Tang
    IHEP Beijing, Beijing
  • J. Wei
    BNL, Upton, Long Island, New York
  Rapid Cycling Synchrotron (RCS) is a key component of Beijing Spallation Neutron Source (BSNS). It accumulates and accelerates protons to design energy of 1.6 GeV and extracts high energy beam to the target. As a high beam density and high beam power machine, low beam loss is also a basic requirement. An optimal lattice design is essential for the cost and the future operation. The lattice design of BSNS is presented, and the related dynamics issues are discussed. The injection/extraction scheme and the beam collimation system design are introduced.  
 
WEPCH187 A Compact 5 MeV, S-band, Electron Linac Based X-ray Tomography System linac, electron, simulation, radiation 2370
 
  • L. Auditore, L. Auditore, R.C. Barnà, D. De Pasquale, D. Loria, A. Trifirò, M. Trimarchi
    INFN & Messina University, S. Agata, Messina
  • U. Emanuele, A. Italiano
    INFN - Gruppo Messina, S. Agata, Messina
  The availability of commercial X-ray tubes made of radiography and tomography two of the most used non-destructive testing techniques both in industrial and cultural heritage fields. Nevertheless, the inspection of heavy materials or thick objects requires X-ray energies larger than the maximum energy provided by commercial X-ray tubes (600 kV). For this reason, and owing to the long experience of the INFN-Gruppo Collegato di Messina in designing and assembling low energy electron linacs, at the Dipartimento di Fisica, Universita di Messina, a 5 MeV electron linac based X-ray tomographic system has been developed. The X-ray source, properly designed by means of the MCNP-4C2 code, provides a 16 cm diameter X-ray spot at the sample position and a beam opening angle of about 3.6 degree. The image acquisition system consists of a CCD camera (Alta Apogee E1, 768x512 pixel) and a GOS scintillating screen. Preliminary radiographies and tomographies showing the high quality performances of the tomographic system have been acquired. Finally, the compactness of the linac, is one of the advantages of this system that could be used for in situ inspections when huge structures have to be tested  
 
THPCH019 Halo and Tail Generation Studies for Linear Colliders scattering, simulation, CLIC, linac 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.