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Rumolo, G.

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OPR02 Recent Experimental Results on Amorphous Carbon Coatings for Electron Cloud Mitigation 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.  
slides icon Slides  
MIT01 Electron Cloud Mitigation Investigations at CesrTA 41
 
  • J. Calvey, J. Makita, M. Palmer, R. Schwartz, C. Strohman
    Cornell University - CLASSE
  • S. Calatroni, G. Rumolo
    CERN
  • K. Kanazawa, Y. Suetsugu
    KEK
  • M. Pivi, L. Wang
    SLAC National Accelerator Laboratory
 
  Over the course of the CesrTA program at Cornell, over 30 Retarding Field Analyzers (RFAs) have been installed in the CESR storage ring. These devices, which measure the local electron cloud density and energy distribution, have been deployed in drift, dipole, quadrupole, and wiggler field regions. They can be used to evaluate the efficacy of cloud mitigation techniques in each magnetic field element. Techniques investigated so far include different beam pipe coatings, grooves, and clearing electrodes. This talk will provide an overview of the electron cloud mitigation program at CESR, give a preliminary evaluation of the effectiveness of various mitigation techniques, and discuss methods used to obtain quantitative information about vacuum chamber properties via simulation.  
slides icon Slides  
PST05 Progress on Simulation of Beam Dynamics with Electron Cloud Effects: An update 100
 
  • K. Sonnad
    Cornell University - CLASSE
  • M. Pivi
    SLAC National Accelerator Laboratory
  • J. Vay
    LBNL
  • G. Rumolo, R. Tomas, F. Zimmermann
    CERN
  • G. Franchetti
    GSI
 
  In this presentation, we will report the progress made in the past few years on simulations to study the electron cloud effects on the dynamics of beams in cicular accelerators. Results associated with various acclerators such as the Fermilab Main Injector, SPS, LHC, ILC damping rings will be shown. Comparisions between the results obtained from three codes, namely Warp, HeadTail and CMad will be discussed. More recent studies done on CesrTA will be discussed in greater detail.  
PST09 Electron Cloud Modeling Results for Time-Resolved Shielded Pickup Measurements at CesrTA 123
 
  • J. Crittenden, Y. Li, X. Liu, M. Palmer, J. Sikora
    Cornell University - CLASSE
  • S. Calatroni, G. Rumolo
    CERN
  • N. Omcikus
    University of California at Los Angeles
 
  The Cornell Electron Storage Ring Test Accelerator (CesrTA) program includes investigations into electron cloud buildup, applying various mitigation techniques in custom vacuum chambers. Among these are two 1.1-m-long sections located symmetrically in the east and west arc regions. These chambers are equipped with pickup detectors shielded against the direct beam-induced signal. They detect cloud electrons migrating through an 18-mm-diameter pattern of holes in the top of the chamber. A digitizing oscilloscope is used to record the signals, providing time-resolved information on cloud development. Carbon-coated, TiN-coated and uncoated aluminum chambers have been tested. Electron and positron beams of 2.1, 4.0 and 5.3 GeV with a variety of bunch populations and spacings in steps of 4 and 14 ns have been used. Here we report on results from the ECLOUD modeling code which highlight the sensitivity of these measurements to model parameters such as the photoelectron azimuthal and energy distributions at production, and the secondary yield parameters including the true secondary, rediffused, and elastic yield values. In particular, witness bunch studies exhibit high sensitivity to the elastic yield by providing information on cloud decay times.