Author: Holtzapple, R.
Paper Title Page
WEP108 Application of Coherent Tune Shift Measurements to the Characterization of Electron Cloud Growth 1680
 
  • D.L. Kreinick, J.A. Crittenden, G. Dugan, M.A. Palmer, G. Ramirez
    CLASSE, Ithaca, New York, USA
  • M.A. Furman, M. Venturini
    LBNL, Berkeley, California, USA
  • R. Holtzapple, M. Randazzo
    CalPoly, San Luis Obispo, California, USA
 
  Funding: DOE = DE-FC02-08ER41538 NSF = PHY-0734867
Measurements of coherent tune shifts at the Cornell Electron Storage Ring Test Accelerator (CesrTA) have been made for electron and positron beams under a wide variety of beam energies, bunch charge, and bunch train configurations. Comparing the observed tunes with the predictions of several electron cloud simulation programs allows the evaluation of important parameters in these models. These simulations will be used to predict the behavior of the electron cloud in damping rings for future linear colliders. We outline recent improvements to the analysis techniques that should improve the fidelity of the modeling.
 
 
WEP194 Measurement Techniques to Characterize Instabilities Caused by Electron Clouds 1852
 
  • M.G. Billing, G. Dugan, M.J. Forster, R.E. Meller, M.A. Palmer, G. Ramirez, J.P. Sikora, H.A. Williams
    CLASSE, Ithaca, New York, USA
  • R. Holtzapple
    CalPoly, San Luis Obispo, California, USA
  • K.G. Sonnad
    Cornell University, Ithaca, New York, USA
 
  Funding: Work is supported by NSF (PHY-0734867) and DOE (DE-FC02-08ER41538) grants.
The study of electron cloud-related instabilities for the CESR-TA project has required the development of new measurement techniques. The dynamics of the interaction of electron clouds with trains of bunches has been undertaken employing three basic observations. Measurements of tune shifts of bunches along a train has been used extensively with the most recent observations permitting the excitation of single bunches within the train to avoid collective train motion from driving the ensemble of bunches. Another technique has been developed to detect the coherent self-excited spectrum for each of the bunches within a train. This method is particularly useful when beam conditions are near the onset of an instability. The third method was designed to study bunches within the train in conditions below the onset of unstable motion. This is accomplished by separately driving each bunch within the train for several hundred turns and then observing the damping of its coherent motion. These last two techniques have been applied to study both transverse dipole (centroid) and head-tail motion. We will report on the observation methods and give examples of typical results.