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collimation

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MOPC091 Benchmarking of Collimation Tracking Using RHIC Beam Loss Data simulation, beam-losses, proton, insertion 274
 
  • G. Robert-Demolaize, K. A. Drees
    BNL, Upton, Long Island, New York
  State-of-the-art tracking tools were recently developed at CERN to study the cleaning efficiency of the Large Hadron Collider (LHC) collimation system. These tools can be benchmarked using data taken from operations of the Relativistic Heavy Ion Collider (RHIC) multi-stage collimation system. This article reviews preliminary simulation results on both the location and the intensity of proton losses around the RHIC lattice. Comparison with live measurements from the beam loss monitors are also shown in order to assess the accuracy of the predictions in the LHC case.  
 
MOPC092 Single Particle Multi-turn Dynamics During Crystal Collimation simulation, proton, scattering, betatron 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.  
 
MOPC095 Mechanical and Thermal Prototype Testing for a Rotatable Collimator for the LHC Phase II Collimation Upgrade simulation, power-supply, beam-losses, impedance 286
 
  • J. C. Smith, J. E. Doyle, L. Keller, S. A. Lundgren, T. W. Markiewicz
    SLAC, Menlo Park, California
  The Phase II upgrade to the LHC collimation systems calls for complementing the 30 high robust Phase I graphite collimators with 30 high Z, low impedance Phase II collimators. The design for the collimation upgrade has not been finalized. One option is to use metallic rotatable collimators and this design will be discussed here. The Phase II collimators must be robust in various operating conditions and accident scenarios. A series of prototype collimator jaws have been tested for both mechanical and thermal compliance with the design goals. Collimator jaw shape after thermal expansion benchtop tests were compared to ANSYS simulation results. Mechanical tests were also performed to demonstrate fabrication precision and collimator movement operation as designed.  
 
MOPC096 Design of a Rotatable Copper Collimator for the LHC Phase II Collimation Upgrade simulation, impedance, shielding, insertion 289
 
  • J. C. Smith, J. E. Doyle, L. Keller, S. A. Lundgren, T. W. Markiewicz
    SLAC, Menlo Park, California
  • L. Lari
    EPFL, Lausanne
  The Phase II upgrade to the LHC collimation systems calls for complementing the 30 high robust Phase I graphite collimators with 30 high Z, low impedance Phase II collimators. The design for the collimation upgrade has not been finalized. One option is to use metallic rotatable collimators and this design will be discussed here. The Phase II collimators must be robust in various operating conditions and accident scenarios. Design issues include:
  1. Collimator jaw deflection due to heating and sagita must be small when operated in the steady state condition,
  2. Collimator jaws must withstand transitory periods of high beam impaction with no permanent damage,
  3. Jaws must recover from accident scenario where up to 8 full intensity beam pulses impact on the jaw surface and
  4. The beam impedance contribution due to the collimators must be small to minimize coherent beam instabilities.
The current design will be presented.
 
 
MOPC098 LHC Particle Collimation by Hollow Electron Beams electron, proton, cathode, ion 292
 
  • V. D. Shiltsev, A. I. Drozhdin, V. Kamerdzhiev, G. F. Kuznetsov, L. G. Vorobiev
    Fermilab, Batavia, Illinois
  Electron Lenses built and installed in Tevatron have proven themselves as safe and very reliable instruments which can be effectively used in hadron collider operation for a number of applications, including compensation of beam- beam effects, DC beam removal from abort gaps, as a diagnostic tool. In this presentation we consider a possibility of using electron lenses with hollow electron beam for ion and proton collimation in LHC.  
 
MOPP016 Collimation Aperture for the Beam Delivery System of the International Linear Collider quadrupole, extraction, linear-collider, emittance 586
 
  • F. Jackson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  The beam delivery sytem (BDS) of the international linear collider (ILC) must provide efficient removal of beam halo particles which would cause unacceptable detector background. The collimation aperture or 'collimation depth' is designed such that synchrotron radiation from the halo emitted in the final doublet passes cleanly through the detector interaction region. The ILC BDS collimation depth for several different detector scenarios is evaluated using a semi-analytical technique.  
 
MOPP046 Collimation Optimizations, Capture Efficiency, and Primary-Beam Power Loss in the ILC Positron Source positron, target, optics, injection 649
 
  • F. Zhou, Y. Nosochkov, J. Sheppard
    SLAC, Menlo Park, California
  • W. Liu
    ANL, Argonne, Illinois
  The ILC positron beam generated from a thin Ti target has a wide energy spread and large transverse divergence. With the collection optics immediately downstream of the target and pre-acceleration to 125 MeV, the collected positron beam still has a long tail of positrons with low energies and large transverse divergence, which will be lost in the rest of the ILC positron source beamline. A collimation system is proposed and optimized for the case of a shielded target with quarter-wave transformation collection optics so that the power loss in the magnets and RF structures is effectively controlled within the acceptable level and in the damping ring (DR) within 640 W, assuming 3× 1010 of the captured positrons per bunch in the DR. In this case, the capture efficiency and DR injection efficiency are 13% and 99.8%, respectively. The lower capture efficiency is expected to result in higher injection efficiency and therefore, a lower power loss in the DR. The capture efficiency for the cases of a shielded target with flux concentrator and 5-T immersed target with flux concentrator is 20% and 30%, respectively, with the collimation system.  
 
TUPD033 Fabrication of Crystals for Channelling of Particles in Accelerators collider, proton, hadron, background 1497
 
  • A. Mazzolari, S. Baricordi, V. Guidi, G. Martinelli, D. Vincenzi
    UNIFE, Ferrara
  Channelling in bent crystals is used for beam extraction, focusing, collimation in accelerators machines, studies related to emission of coherent electromagnetic radiation and other topics. Distinctive features of performance increase is the availability of new techniques to manufacture the crystals within which channeling takes place. We propose a method to fabricate crystals through micromachining techniques, i.e., photolithography and anisotropic chemical etching. Patterning of a Si wafer with silicon nitride allows selective erosion of uncovered areas along specific atomic planes, resulting in a technique to dice Si wafers to the needed dimensions solely through chemical methods. Thus, it results in no damage to the crystal quality due to the dicing process. As was demonstrated by electron microscopy investigation, the crystal exhibits ultra flat lateral surfaces and simultaneously no amorphous layer at the entry face of the crystal with respect to the beam. The crystals were positively tested at the external line H8 of the SPS with 400 GeV protons for investigation on axial channeling and on single and multiple volume reflection experiments by the H8-RD22 collaboration.  
 
TUPP042 Status of the ORBIT Code: Recent Developments and Plans scattering, acceleration, injection, synchrotron 1637
 
  • J. A. Holmes, S. M. Cousineau, A. P. Shishlo
    ORNL, Oak Ridge, Tennessee
  We report on recent enhancements to the physics modules of the ORBIT Code and on progress toward a new implementation of ORBIT using python. We have developed the capability to track particles through general three dimensional electromagnetic field configurations. This facility has proved essential in modeling beam transport through the complicated magnetic field regions of the SNS injection chicane and injection dump line, where beam losses are high. We have also enhanced the acceleration module to provide more flexibility for synchrotron calculations. Finally, progress continues on the migration of the ORBIT physics models to a python user environment, and we present the status of this work.  
 
TUPP073 Bench-top Impedance Measurements for a Rotatable Copper Collimator for the LHC Phase II Collimation Upgrade impedance, vacuum, simulation, target 1703
 
  • J. C. Smith, K. L.F. Bane, J. E. Doyle, L. Keller, S. A. Lundgren, T. W. Markiewicz, C.-K. Ng, L. Xiao
    SLAC, Menlo Park, California
  The Phase II upgrade to the LHC collimation system calls for complementing the 30 high robust Phase I graphite collimators with 30 high Z, low impedance Phase II collimators. The design for the collimation upgrade has not been finalized. One option is to use metallic rotatable collimators and this design will be discussed here. Simulations have been performed in MAFIA to study both the resistive wall and geometric impedance contributions of our rotatable collimator design. Benchtop stretched coil probe impedance measurements have also been performed on prototype components to directly measure the low frequency impedance contributions. The design also calls for an RF contact interface at the jaw end. This contact resistance must be a small fraction of a milliohm in order to limit transverse impedance. DC resistance measurements in a custom built test chamber have been performed to test the performance of various metal pairs and surface coatings.  
 
TUPP085 Beam Dynamics Using Graphical Processing Units (GPUs) lattice, extraction, simulation, beam-transport 1727
 
  • R. Appleby, D. Bailey, M. D. Salt
    UMAN, Manchester
  Simulation of particle beam dynamics in accelerators is computationally expensive, and requires very high particle statistics and accuracy. Conventional beam tracking tools operate sequentially on particle phase space to compute the trajectories of particles through many turns of circular, and linear, machines. Graphical Processing Units (GPUs) utilise stream processing techniques to dramatically speed up parallel computational tasks, and offer considerable performance benefits to particle beam dynamics processing. In this paper, the stream processing beam dynamics code GPMAD is presented, which exploits the NVidia GPU processor, and demonstrates the considerable performance benefits to particle tracking calculations. The accuracy and speed of GPMAD is benchmarked using the Diamond Light Source BTS lattice, and the collimation system is evaluated.  
 
WEOAG02 Measurements of Heavy Ion Beam Losses from Collimation ion, simulation, proton, beam-losses 1906
 
  • R. Bruce, R. W. Assmann, G. Bellodi, C. Bracco, H.-H. Braun, S. S. Gilardoni, E. B. Holzer, J. M. Jowett, S. Redaelli, Th. Weiler, C. Zamantzas
    CERN, Geneva
  The collimation efficiency for Pb82+ ion beams in the LHC is predicted to be much lower than for protons. Nuclear fragmentation and electromagnetic dissociation in the primary collimators create fragments with a wide range of Z/A ratios, which are not intercepted by the secondary collimators but lost where the dispersion has grown sufficiently large. In this article we present measurements of loss patterns caused by a prototype LHC collimator in the CERN SPS. The loss maps show a qualitative difference between Pb82+ ions and protons, with the maximum loss rate observed at different places in the ring. This behaviour was predicted by simulations and provides a valuable benchmark of the simulations done for the LHC.  
slides icon Slides  
 
WEPC073 Layout of the Beam Switchyard at the European XFEL kicker, septum, undulator, linac 2163
 
  • W. Decking, F. Obier
    DESY, Hamburg
  A unique feature of the European XFEL will be the possibility to distribute electron bunches of one beam pulse to different FEL beam lines. This is achieved by using a combination of fast kickers and a DC septum. Integration of a beam abortion dump allows a flexible selection of the bunch pattern at the FEL experiment, while the superconducting linear accelerator operates with constant beam-loading. We describe the principal scheme, the geometrical and optical layout and deal with stability and technical issues like the fast kicker development.  
 
WEPP006 Effects of Ultraperipheral Nuclear Collisions in the LHC and their Alleviation ion, simulation, beam-losses, luminosity 2533
 
  • R. Bruce, S. S. Gilardoni, J. M. Jowett
    CERN, Geneva
  Electromagnetic interactions between colliding heavy ions at the LHC are the sources of specific beam loss mechanisms that may quench superconducting magnets. We propose a simple yet efficient strategy to alleviate the effect of localized losses from bound-free pair production by spreading them out in several magnets by means of orbit bumps. We also consider the consequences of neutron emission by electromagnetic dissociation and show through simulations that ions modified by this process will be intercepted by the collimation system, without further modifications.  
 
WEPP007 Crab Compensation for LHC Beams impedance, damping, optics, luminosity 2536
 
  • R. Calaga
    BNL, Upton, Long Island, New York
  • Y. Sun, R. Tomas, F. Zimmermann
    CERN, Geneva
  An R&D program to establish a road map for the installation of crab cavities in the LHC is rapidly advancing. Both local and global crab schemes are under investigation to develop cavities that will be compatible with LHC optics and meet aperture requirements. The design of a prototype TM110 cavity and pertinent RF requirements including impedance estimates and damping are discussed. Some alternate cavity designs are also explored. The required optics modifications to accommodate the crab cavities and some particle stability studies are presented.  
 
WEPP009 Collimator Integration and Installation Example of One Object to be Installed in the LHC vacuum, insertion, alignment, survey 2542
 
  • K. Foraz, O. Aberle, R. W. Assmann, C. Bertone, R. Chamizo, S. Chemli, J.-P. Corso, F. Delsaux, J. L. Grenard, J. M. Jimenez, Y. Kadi, K. Kershaw, M. Lazzaroni, R. Perret, Th. Weiler
    CERN, Geneva
  • J. Coupard
    IN2P3-CNRS, Orsay
  The collimation system is a vital part of the LHC project, protecting the accelerator against unavoidable regular and irregular beam loss. About 80 collimators will be installed in the machine before the first run. Two insertion regions are dedicated to collimation and these regions will be among the most radioactive in the LHC. The space available in the collimation regions is very restricted. It was therefore important to ensure that the 3-D integration of these areas of the LHC tunnel would allow straightforward installation of collimators and also exchange of collimators under the remote handling constraints imposed by high radiation levels. The paper describes the 3-D integration studies and verifications of the collimation regions combining the restricted space available, the dimensions of the different types of collimators and the space needed for transport and handling. The paper explains how installation has been planned and carried out taking into account the handling system and component availability.  
 
WEPP068 Impact Distribution of the Beam Losses at the LHC Collimators in Case of Magnet Failures injection, quadrupole, dipole, simulation 2674
 
  • A. Gomez Alonso
    CERN, Geneva
  During LHC operation, magnet failures may affect the beam optics leading to proton losses in the collimators. These losses, with about 360MJ of stored energy per beam at nominal collision operation, are potentially dangerous for the accelerator equipment. The LHC Machine Protection Systems ensure that the beam is extracted safely before these losses can produce any damage. As a magnet failure develops, so does the distribution of the lost particles, longitudinally along the ring as well as transversally at each collimator. The transversal impact distributions of lost particles at the most affected collimators and their evolution with time have been studied for representative magnet failures in the LHC. It has been found that the impact distribution at a given collimator can be approximated by an exponential function with time-dependent parameters. The average impact parameter ranges from about 7 to 620 μm for the cases studied.  
 
WEPP070 High Efficiency Collimation with Bent Crystals scattering, alignment, proton, simulation 2680
 
  • S. Hasan
    Univ. Insubria and INFN Milano, Como
  A revolutionary collimation approach is being developed by the H8RD22 collaboration. The basic idea is to replace the amorphous jaws, which spread the beam halo in the whole solid angle, with bent crystals, which are able to deviate the halo particles in a given direction outside the beam core. Studies to investigate the bent crystal properties have been carried out over the past 3 years at the H8 beam line (CERN SPS) with a 400 GeV/c proton beam. The crucial result of these studies is the observation of the Volume Reflection effect, the coherent scattering of the beam on the crystalline plane which provides a small but very efficient (respectively, 14 μrad and 98% at 400 GeV/c) particle deflection. The high efficiency (which should increase at higher energy) combined with a large angular acceptance (~100 μrad) led to the development of multi-reflection systems to increase the deflection angle. Nowadays this system has reached the stage to be tested in a circular accelerator as a primary collimator to verify the effective collimation efficiency in a complex environment. The second phase of the LHC collimation could be the first application of this crystal based system.  
 
WEPP071 Preliminary Exploratory Study of Different Phase II Collimators simulation, radiation, luminosity, impedance 2683
 
  • L. Lari, R. W. Assmann, A. Bertarelli, C. Bracco, M. Brugger, F. Cerutti, A. Dallocchio, A. Ferrari, M. Mauri, S. Roesler, L. Sarchiapone, V. Vlachoudis
    CERN, Geneva
  • J. E. Doyle, L. Keller, S. A. Lundgren, T. W. Markiewicz, J. C. Smith
    SLAC, Menlo Park, California
  • L. Lari
    EPFL, Lausanne
  The LHC collimation system is installed and commissioned in different phases, following the natural evolution of the LHC performance. To improve cleaning efficiency towards the end of the low beta squeeze at 7TeV, and in stable physics conditions, it is foreseen to complement the 30 highly robust Phase I secondary collimators with low impedance Phase II collimators. At this stage, their design is not yet finalized. Possible options include metallic collimators, graphite jaws with a movable metallic foil, or collimators with metallic rotating jaws. As part of the evaluation of the different designs, the FLUKA Monte Carlo code is extensively used for calculating energy deposition and studying material damage and activation. This report outlines the simulation approach and defines the critical quantities involved.  
 
WEPP072 Evaluation of Beam Losses and Energy Deposition for A Possible Phase II Design for LHC Collimation simulation, beam-losses, proton, kicker 2686
 
  • L. Lari, R. W. Assmann, C. Bracco, M. Brugger, F. Cerutti, A. Ferrari, M. Mauri, S. Redaelli, L. Sarchiapone, V. Vlachoudis, Th. Weiler
    CERN, Geneva
  • J. E. Doyle, L. Keller, S. A. Lundgren, T. W. Markiewicz, J. C. Smith
    SLAC, Menlo Park, California
  • L. Lari
    EPFL, Lausanne
  The LHC beams are designed to have high stability and to be stored for many hours. The nominal beam intensity lifetime is expected to be of the order of 20h. The Phase II collimation system has to be able to handle particle losses in stable physics conditions at 7 TeV in order to avoid beam aborts and to allow correction of parameters and restoration to nominal conditions. Monte Carlo simulations are needed in order to evaluate the behavior of metallic high-Z collimators during operation scenarios using a realistic distribution of losses, which is a mix of the three limiting halo cases. Moreover, the consequences in the IR7 insertion of the worst (case) abnormal beam loss are evaluated. The case refers to a spontaneous trigger of the horizontal extraction kicker at top energy, when Phase II collimators are used. These studies are an important input for engineering design of the collimation Phase II system and for the evaluation of their effect on adjacent components. The goal is to build collimators that can survive the expected conditions during LHC stable physics runs, in order to avoid quenches of the SC magnets and to protect other LHC equipments.  
 
WEPP102 Design of the ILC RTML Extraction Lines extraction, kicker, damping, focusing 2752
 
  • S. Seletskiy, P. Tenenbaum, D. R. Walz
    SLAC, Menlo Park, California
  • N. Solyak
    Fermilab, Batavia, Illinois
  The Damping Ring to the Main Linac beamline (RTML) is equipped with three extraction lines (EL). Each EL can be used both for an emergency abort dumping of the beam and the tune-up continual train-by-train extraction. Two of the extraction lines are located downstream of the first and second stages of the RTML bunch compressor, and must accept both compressed and uncompressed beam with energy spread of 2.5 % and 0.15 % respectively. In this paper we report optical design that allowed us to minimize the length of the extraction lines while offsetting the beam dumps from the main line by the distance required for acceptable radiation level in the service tunnel. Proposed extraction lines can accommodate beams with different energy spreads at the same time providing the beam size suitable for the aluminum dump window.  
 
WEPP158 Simulation of beam Halo in CLIC Collimation Systems simulation, synchrotron, synchrotron-radiation, radiation 2859
 
  • G. A. Blair, S. Malton
    Royal Holloway, University of London, Surrey
  • I. V. Agapov, A. Latina, D. Schulte
    CERN, Geneva
  Full simulation of the CLIC and ILC collimation systems are performed to take account of collimator wakefield effects from the core beam on the halo. In addition full simulation of the interaction of the halo with the collimator material is performed to study the effect of multiple scattering and also the production of neutrons in the electromagnetic showers. The effect of beam-gas scattering downstream of the collimators is also included.  
 
WEPP164 Beam Collimation Studies for the ILC Positron Source positron, emittance, damping, target 2871
 
  • A. I. Drozhdin
    Fermilab, Batavia, Illinois
  • Y. Nosochkov, F. Zhou
    SLAC, Menlo Park, California
  The results of collimation studies for the ILC positron source beam line are presented. The calculations of primary positron beam loss are done using the ELEGANT code. The secondary positron and electron beam loss, synchrotron radiation along the beam line and bremsstrahlung radiation in the collimators are simulated using the STRUCT code. The first part of the system, located right after the positron source target at 0.125 GeV, is used for protection of super-conducting RF Linac from heating and radiation. The second part of the system is used for final collimation of the beam before injection to the Damping Ring at 5 GeV. The calculated power loss in the collimation region is about 100 W/m, with loss in the collimators of 0.2-5 kW. The beam transfer efficiency from target to the Damping Ring is 13.5%.  
 
WEPP167 Effect of Collimator Wakefields in the Beam Delivery System of the International Linear Collider emittance, lattice, simulation, linear-collider 2880
 
  • A. M. Toader, R. J. Barlow
    UMAN, Manchester
  • D. Angal-Kalinin, F. Jackson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  The collimators in the design of the International Linear Collider (ILC) Beam Delivery System (BDS) may be a significant source of wakefields and significantly degrade luminosity. New simulations are used to predict the effect of BDS collimator wakefields, and compared with previous analytical methods. BDS lattices optimised for improved collimation performance are also examined.  
 
THYG01 The ILC Beam Delivery System Design and R&D Programme extraction, collider, linear-collider, instrumentation 2907
 
  • T. Tauchi
    KEK, Ibaraki
  The presentation will describe recent developments for the ILC beam delivery system. Special emphasis will be given to the R&D programme at existing and planned test facilities.  
slides icon Slides  
 
THPC052 Beam Losses and Collimation Considerations for PS2 injection, beam-losses, extraction, lattice 3098
 
  • J. Barranco, W. Bartmann, M. Benedikt, Y. Papaphilippou
    CERN, Geneva
  The high intensity beams with different emittances foreseen to be delivered by the PS2, an upgraded version of the actual CERN Proton Synchrotron, require strict control of beam losses in order to protect the machine components and enable their hands-on maintenance. Beam loss simulations based on dedicated numerical tools are undertaken for a variety of PS2 beams and for different loss mechanisms, along the whole accelerating cycle. In this respect, the design of a collimation system is presented and its performance is compared within different lattice options.  
 
THPC147 Generation of 1.5 Million Beam Loss Threshold Values proton, simulation, beam-losses, insertion 3333
 
  • E. B. Holzer, B. Dehning, L. Ponce, M. Sapinski, M. Stockner
    CERN, Geneva
  • D. K. Kramer
    TUL, Liberec
  • P. Priebe
    Poznan University of Technology, Poznan
  CERN's Large Hadron Collider will store an unprecedented amount of energy in its circulating beams. Beam-loss monitoring (BLM) is, therefore, critical for machine protection. It must protect against the consequences (equipment damage, quenches of superconducting magnets) of excessive beam loss. 4000 monitors will be installed at critical loss locations. Each monitor has 384 beam abort thresholds associated; for 12 integrated loss durations (40 us to 83 s) and 32 energies (450 GeV to 7 TeV). Depending on monitor location, the thresholds vary by orders of magnitude. For simplification, the monitors are grouped in 'families'. Monitors of one family have the same thresholds at start-up; they protect similar magnets against equivalent loss scenarios. The start-up calibration of the BLM system is required to be within a factor of five in accuracy; and the final accuracy should be a factor of two. Simulations (backed-up by control measurements) determine the relation between the BLM signal, the deposited energy and the critical energy deposition for damage or quench (temperature of the coil). The paper presents the details and systematic of determining 1.5 million threshold values.