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Sikora, J.

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DYN03 Studies of the Electron-Cloud-Induced Beam Dynamics at CesrTA 60
 
  • G. Dugan, M. Billing, R. Meller, M. Palmer, G. Ramirez, J. Sikora, K. Sonnad, H. Williams
    Cornell University - CLASSE
  • R. Holtzapple
    California Polytechnic State University
 
  This talk will review recent data and simulation results related to electron-cloud induced beam dynamics studies at Cesr-TA.  
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PST04 TE Wave Measurements at CesrTA 95
 
  • J. Sikora
    Cornell University - CLASSE
  • S. De Santis
    LBNL
  • K. Hammond
    Harvard University
 
  Funding: This work is supported by the US National Science Foundation PHY-0734867, and the US Department of Energy DE-FC02-08ER41538

TE Wave measurement systems have been installed in the L0 and L3 regions of CesrTA. L0 is the location of 6 superconducting wiggler magnets; L3 has round beampipe through a chicane magnet (PEPII) and a NEG coated chamber. At both locations, rf relays are used to multiplex signals from a signal generator output, through the beampipe, and to the input of a spectrum analyzer. Software monitors can be triggered to take data on demand, or on changes in accelerator conditions such as beam current or wiggler fields. The poster will describe the TE Wave measurement technique, the installation of hardware at CesrTA and some measurement examples. It will also outline some of the problems in the interpretation of data, specifically the results of reflections and standing waves.

 
PST06 Effects of Reflections on TE-Wave Measurements of Electron Cloud Density 103
 
  • K. Sonnad, J. Sikora
    Cornell University - CLASSE
  • K. Hammond
    Harvard University
  • S. Veitzer
    Tech-X Corporation
 
  The simulation code VORPAL has been used as a tool to study charecteristics of TE wave transmission in the presence of electron clouds for CesrTA. We look at how the electron cloud induced phase shift is influenced by (1) reflections of the wave, caused by possible protrusions in the beam pipe and (2)effect of nonuniformities of the cloud density distribution in the transverse plane.  
PST07 Techniques for Observing Beam Dynamical Effects Caused by the Presence of Electron Clouds 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.  
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.  
DIA01 TE Wave Measurements at Cesr-TA  
 
  • S. De Santis, J. Byrd, G. Penn
    LBNL
  • J. Sikora
    Cornell University - CLASSE
  • K. Hammond
    Harvard University
 
  TE wave transmission is currently used as a diagnostic tool for measurements of the electron cloud density in several regions of the Cesr-TA ring. While the method is conceptually well established, a number of effects contribute to making a quantitative estimate of the density not straightforward. We report on the measurements currently performed during Cesr-TA experimental runs, describe experimental challenges, and the methods devised to analyze and solve them.  
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