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dipole

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OPR02 Recent Experimental Results on Amorphous Carbon Coatings for Electron Cloud Mitigation electron, vacuum, cathode, proton 6
 
  • C. Yin Vallgren, S. Calatroni, P. Chiggiato, P. Costa Pinto, H. Neupert, M. Taborelli, G. Rumolo, E. Shaposhnikova, W. Vollenberg
    CERN
  Amorphous carbon (a-C) thin films, produced in different coating configurations by using d.c magnetron sputtering, have been investigated in laboratory for low secondary electron yield (SEY) applications. After the coatings had shown a reliable low initial SEY, the a-C thin films have been applied in the SPS and tested with LHC type beams. Currently, we have used a-C thin film coated in so-called liner configuration for the electron cloud monitors as well as for a removable sample. In addition the vacuum chambers of three dipole magnets have been coated and inserted in the machine. After describing the different configurations used for the coatings, results of the tests in the machine and a summary of the analyses after extraction will be presented. Based on comparison between different coating configurations, a new series of coatings has been applied on three further dipole magnet vacuum chambers. They have been installed and will be tested in coming machine development runs.  
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PST07 Techniques for Observing Beam Dynamical Effects Caused by the Presence of Electron Clouds electron, betatron, kicker, feedback 108
 
  • M. Billing, G. Dugan, R. Meller, M. Palmer, G. Ramirez, H. Williams, J. Sikora
    Cornell University - CLASSE
  • R. Holtzapple
    California Polytechnic State University
  During the last several years CESR has been studying the effects of electron clouds on stored beams in order to understand their impact on future linear-collider damping ring designs. One of the important issues is the way that the electron cloud alters the dynamics of bunches within the train. Techniques for observing the dynamical effects of beams interacting with the electron clouds have been developed. These methods and examples of measurements are presented here.  
 
PST10 Using Coherent Tune Shifts to Evaluate Electron Cloud Effects on Beam Dynamics at CesrTA simulation, positron, electron, photon 130
 
  • D. Kreinick, J. Crittenden, G. Dugan, Z. Leong, M. Palmer
    Cornell University - CLASSE
  • R. Holtzapple, M. Randazzo
    California Polytechnic State University
  • M. Furman, M. Venturini
    LBNL
  One technique used at CesrTA for studying the effects of electron clouds on beam dynamics is to measure electron and positron bunch tunes under a wide variety of beam energies, bunch charge, and bunch train configurations. Comparing the observed tunes with the predictions of various simulation programs allows the evaluation of important parameters in the cloud formation models. These simulations will be used to predict the behavior of the electron cloud in damping rings for future linear colliders.  
 
MOD03 Accurate Simulation of the Electron Cloud in the Fermilab Main Injector with VORPAL electron, simulation, proton, quadrupole 152
 
  • P. Lebrun, P. Spentzouris
    Fermilab
  • J. Cary
    University of Colorado Boulder
  • S. Veitzer, P. Stoltz
    Tech-X Corporation
  We present results from a precision simulation of the electron cloud (EC) problem in the Fermilab Main Injector using the code VORPAL. Fully 3D and self consistent that include both distributions of electrons in 6D phase-space and E. M. field maps. Various configurations of the magnetic fields found around the machine have been studied. Plasma waves associated to the fluctuation density of the cloud have been analyzed. Our results are compaired with those obtained with the POSINST code. It is shown that the 3D effects are important. The response of a Retarding Field Analyzer (RFA) to the EC has been simulated, as well as the more challenging microwave absorption experiment. Definite predictions of their exact response are difficult to compute, mostly because of the uncertainties in the secondary emission yield and, in the case of the RFA, because of the sensitivity of the electron collection efficiency to unknown stray magnetic fields. Nonetheless, our simulations do provide guidance to the experimental program.  
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DIA00 Electron Cloud Studies in the Fermilab Main Injector Using Microwave Transmission electron, proton, lattice, plasma 173
 
  • J. Thangaraj, N. Eddy, R. Zwaska, K. Seiya, I. Kourbanis, J. Crisp
    Fermilab
  In this paper, we present recent results from our measurement at the Fermilab Main Injector through microwave transmission in a beam pipe. We present three types of measurement techniques. In the first technique, we use time-resolved direct phase shift measurement to measure the e-cloud density. In the second and third techniques, we look for side bands in the frequency spectrum with or without frequency span by collecting turns of data. Finally, we also discuss the resonant BPM method, where a signal below the waveguide cutoff is sent through a one side of the BPM and is collected on the other side of the BPM to look for phase shift due to electron cloud. We present experimental results taken from MI40 and MI52 section of the main injector.  
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FTR00 ILC Damping Rings: Benefit of the Antechamber or: Antechamber vs. SEY electron, simulation, positron, photon 194
 
  • M. Furman
    LBNL
  We review the simulation results for the electron cloud build-up for the ILC Damping Rings, for both lattice options considered (6 km and 3 km), in a field-free region and in a bending dipole magnet. While the 6 km lattice is slightly more forgiving than the 3-km lattice vis-a-vis the electron cloud effects, we conclude that, in general, the existence of an antechamber helps to dramatically reduce the electron-cloud density (factor ~50) only if the peak secondary yield of the chamber surface is below a certain critical value. This critical value is in the range ~1.1~1.3, depending on various details.  
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