• J.R. Calvey, J.A. Crittenden, G. Dugan, S. Greenwald, Z. Leong, J.A. Livezey, M.A. Palmer
  CLASSE, Ithaca, New York
• C.M. Celata
  Cornell University, Ithaca, New York
• M.A. Furman, M. Venturini
  LBNL, Berkeley, California
• K.C. Harkay
  ANL, Argonne

Retarding field analyzers (RFAs) provide an effective measure of the local electron cloud density and energy distribution. Proper interpretation of RFA data can yield information about the behavior of the cloud, as well as the surface properties of the instrumented vacuum chamber. However, due to the complex interaction of the cloud with the RFA, particularly in regions of high magnetic field, understanding these measurements can be nontrivial. This paper will examine different methods for interpreting RFA data via cloud simulation programs. Possible techniques include postprocessing the output of a simulation code to predict the RFA response, and incorporating an RFA model into the program itself.

• J.R. Calvey, Y. Li, J.A. Livezey, J. Makita, R.E. Meller, M.A. Palmer, R.M. Schwartz, C.R. Strohman
  CLASSE, Ithaca, New York
• S. Calatroni, G. Rumolo
  CERN, Geneva
• K.C. Harkay
  ANL, Argonne
• K. Kanazawa, Y. Suetsugu
  KEK, Ibaraki
• M.T.F. Pivi, L. Wang
  SLAC, Menlo Park, California

Over the course of the CesrTA program, the Cornell Electron Storage Ring (CESR) has been instrumented with several retarding field analyzers (RFAs), which measure the local density and energy distribution of the electron cloud. These RFAs have been installed in drifts, dipoles, quadrupoles, and wigglers; and data have been taken in a variety of beam conditions and bunch configurations. This paper will provide an overview of these results, and give a preliminary evaluation of the efficacy of cloud mitigation techniques implemented in the instrumented vacuum chambers.

• J.A. Crittenden, J.R. Calvey, G. Dugan, D.L. Kreinick, Z. Leong, J.A. Livezey, M.A. Palmer, D. L. Rubin, D. Sagan
  CLASSE, Ithaca, New York
• M.A. Furman, G. Penn, M. Venturini
  LBNL, Berkeley, California
• K.C. Harkay
  ANL, Argonne
• R. Holtzapple
  CalPoly, San Luis Obispo, CA
• M.T.F. Pivi, L. Wang
  SLAC, Menlo Park, California

The Cornell Electron Storage Ring Test Accelerator (CesrTA) program has included extensive measurements of coherent tune shifts for a variety of electron and positron beam energies, bunch current levels, and bunch train configurations. The tune shifts have been shown to result primarily from the interaction of the beam with the space-charge field of the beam-induced low-energy electron cloud in the vacuum chamber. Comparison to several advanced electron cloud simulation program packages has allowed determination of the sensitivity of these measurements to physical parameters such as the synchrotron radiation flux, its interaction with the vacuum chamber wall, the beam emittance and lattice optics, as well as to those of the various contributions to the electron secondary yield model. We report on progress in understanding the cloud buildup and decay mechanisms in magnetic fields and in field-free regions, addressing quantitatively the precise determination of the physical parameters of the modelling. Validation of these models will serve as essential input in the design of damping rings for future high-energy linear colliders.

• M.A. Palmer, J.P. Alexander, M.G. Billing, J.R. Calvey, C.J. Conolly, J.A. Crittenden, J. Dobbins, G. Dugan, N. Eggert, E. Fontes, M.J. Forster, R.E. Gallagher, S.W. Gray, S. Greenwald, D.L. Hartill, W.H. Hopkins, D.L. Kreinick, B. Kreis, Z. Leong, Y. Li, X. Liu, J.A. Livezey, A. Lyndaker, J. Makita, M.P. McDonald, V. Medjidzade, R.E. Meller, T.I. O'Connell, S.B. Peck, D.P. Peterson, G. Ramirez, M.C. Rendina, P. Revesz, D.H. Rice, N.T. Rider, D. L. Rubin, D. Sagan, J.J. Savino, R.M. Schwartz, R.D. Seeley, J.W. Sexton, J.P. Shanks, J.P. Sikora, E.N. Smith, C.R. Strohman, H.A. Williams
  CLASSE, Ithaca, New York
• F. Antoniou, S. Calatroni, M. Gasior, O.R. Jones, Y. Papaphilippou, J. Pfingstner, G. Rumolo, H. Schmickler, M. Taborelli
  CERN, Geneva
• D. Asner
  Carleton University, College of Natural Sciences, Ottawa, Ontario
• L. Boon, A.F. Garfinkel
  Purdue University, West Lafayette, Indiana
• J.M. Byrd, C.M. Celata, J.N. Corlett, S. De Santis, M.A. Furman, A. Jackson, R. Kraft, D.V. Munson, G. Penn, D.W. Plate, M. Venturini
  LBNL, Berkeley, California
• B.T. Carlson
  Grove City College, Grove City, Pennsylvania
• T. Demma
  INFN/LNF, Frascati (Roma)
• R.T. Dowd
  ASCo, Clayton, Victoria
• J.W. Flanagan, P. Jain, K. Kanazawa, K. Kubo, K. Ohmi, H. Sakai, K. Shibata, Y. Suetsugu, M. Tobiyama
  KEK, Ibaraki
• D. Gonnella
  Clarkson University, Potsdam, New York
• W. Guo
  BNL, Upton, Long Island, New York
• K.C. Harkay
  ANL, Argonne
• R. Holtzapple
  CalPoly, San Luis Obispo, CA
• J.K. Jones, A. Wolski
  Cockcroft Institute, Warrington, Cheshire
• D. Kharakh, J.S.T. Ng, M.T.F. Pivi, L. Wang
  SLAC, Menlo Park, California
• M.C. Ross, C.-Y. Tan, R.M. Zwaska
  Fermilab, Batavia
• L. Schächter
  Technion, Haifa
• E.L. Wilkinson
  Loyola University, Chicago, Illinois

The Cornell Electron Storage Ring (CESR) has been reconfigured as a test accelerator (CesrTA) for a program of electron cloud (EC) research at ultra low emittance. The instrumentation in the ring has been upgraded with local diagnostics for measurement of cloud density and with improved beam diagnostics for the characterization of both the low emittance performance and the beam dynamics of high intensity bunch trains interacting with the cloud. Finally a range of EC mitigation methods have been deployed and tested. Measurements of cloud density and its impact on the beam under a range of conditions will be presented and compared with simulations. The effectiveness of a range of mitigation techniques will also be discussed.

Slides

• M.T.F. Pivi, L. Wang
  SLAC, Menlo Park, California
• C.M. Celata, M.A. Furman, M. Venturini
  LBNL, Berkeley, California
• J.A. Crittenden, G. Dugan, M.A. Palmer
  CLASSE, Ithaca, New York
• T. Demma, S. Guiducci
  INFN/LNF, Frascati (Roma)
• K.C. Harkay
  ANL, Argonne
• O.B. Malyshev
  Cockcroft Institute, Warrington, Cheshire
• K. Ohmi, K. Shibata, Y. Suetsugu
  KEK, Ibaraki
• Y. Papaphilippou, G. Rumolo
  CERN, Geneva

As part of the International Linear Collider (ILC) collaboration, we have compared the electron cloud effect for different Damping Ring designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of a shorter damping ring with respect to the electron cloud build-up and related beam instability. These studies were carried out with beam parameters of the ILC Low Power option. A reduced damping ring circumference has been proposed for the new ILC baseline design and would allow to considerably reduce the number of components, wiggler magnets and costs. We also briefly discuss the plans for future studies including the luminosity upgrade option with shorter bunch spacing, the evaluation of mitigations and the integration of the CesrTA results into the Damping Ring design.