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OPR05 Emittance Growth and Tune Spectra at PETRA III emittance, electron, simulation, wiggler 21
 
  • R. Wanzenberg
    DESY
  At DESY the PETRA ring has been converted into a synchrotron radiation facility, called PETRA III. 20 damping wigglers have been installed to achieve an emittance of 1 nm. The commissioning with beam started in April 2009 and user runs have been started in 2010. The design current is 100 mA and the bunch to bunch distance is 8 ns for one particular filling pattern with 960 bunches. At a current of about 50 mA a strong vertical emittance increase has been observed. During machine studies it was found that the emittance increase depends strongly on the bunch filling pattern. For the user operation a filling scheme has been found which mitigates the increase of the vertical emittance. In Aug. 2010 PETRA III has been operated without damping wigglers for one week. The vertical emittance growth was not significantly smaller without wigglers. Furthermore tune spectra at PETRA III show characteristic lines which have been observed at other storage rings in the connection with electron clouds. The measurements at PETRA III are presented for different bunch filling patterns and with and without wiggler magnets.  
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MIT00 e-Cloud Activity of DLC and TiN Coated Chambers at KEKB Positron Ring positron, electron, vacuum, ion 37
 
  • S. Kato, M. Nishiwaki
    KEK
  A copper chamber without coating and TiN and diamond like carbon (DLC) coated aluminum chambers were installed to an arc section of the KEKB positron ring to make comparisons of electron cloud activity as well as total pressure and residual gas components during the beam operation under the same condition. Recently a DLC coated aluminum chamber with high surface roughness that was obtained with cost-effective simple abrasive of the large grain before the coating was installed in the same arc section and exposed to the electron cloud until the KEKB shutdown. The measured electron cloud activity in the DLC coated chamber with smooth surface showed half and one-sixth of those in the TiN coated chamber and the copper chamber, respectively at the operation of around 1·103 Ah. Much more reduction of the e-cloud activity owing to the DLC on the roughed chamber surface was found, that is ,a reduction of one-fifth and one-tenth, respectively, in comparison with the DLC on non-roughed chamber and the TiN coating on non-roughed chamber at around 1·103 Ah. Preparation of the DLC coated chamber, characteristics of the DLC and measurements including the residual gas observation will be also reported in detail.  
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MIT03 Experimental Efforts at LNF to Reduce Secondary Electron Yield in Particle Accelerators electron, radiation, vacuum, synchrotron-radiation 46
 
  • R. Cimino, M. Commisso, T. Demma, D. Grosso
    INFN/LNF
  • N. Mahne, A. Giglia
    CNR-IOM
  A common effort in most of the accelerator centers is to develop new technologies to produce and test beam pipe inner walls of particle accelerators with an as low as possible Secondary Electron Yield (SEY). This item, in fact, is crucial in controlling Electron Cloud formation and in reducing its effects, that are well known to be a potential bottle-neck to the performances obtainable from present and future accelerators. Frascati has a longstanding experience in qualifying materials in terms of surface parameters of interest to e-cloud issues. We are routinely measuring SEY, its dependence from electron energy, temperature and scrubbing and we are about to be ready to study not only Photo Electron Yield (PEY) by using synchrotron radiation beamlines in construction at DAΦNE, but more importantly, to characterize in situ the surface chemical composition and eventual modifications occurring during electron or photon irradiation. Such characterization effort is also suggesting ways to produce Low SEY materials. Some preliminary results will be here discussed.  
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DYN03 Studies of the Electron-Cloud-Induced Beam Dynamics at CesrTA electron, betatron, emittance, single-bunch 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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DIA03 Analysis of the Electron Cloud Density Measurement With RFA in a Positron Ring electron, quadrupole, simulation, positron 184
 
  • K. Kanazawa, H. Fukuma
    KEK
  • P. Jain
    The Graduate University for Advanced Studies
  In a positron ring such as KEKB LER, clouding electrons receive an almost instantaneous kick from circulating bunches. Therefore, high energy electrons in the cloud are produced just after the interaction with the bunch locally around the beam. The authors gave an estimation of their density using a high energy electron current measured with RFA and a calculated volume neglecting their initial velocity before the interaction with the bunch. To evaluate the accuracy of this estimation, the process of the measurement is analyzed using the phase space density for the motion of electrons in the transverse plane of the beam. The expressions that can evaluate the accuracy of the estimation with the help of simulation are obtained. One of the authors has shown that the accuracy for a drift space is within ±5% error. For other cases such as in a solenoid field, in a quadruple field, the evaluation is not yet given. In addition to this discussion, some examples of the estimation with RFA are shown.  
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DIA04 Status of COLDDIAG: a Cold Vacuum Chamber for Diagnostics electron, vacuum, diagnostics, radiation 190
 
  • S. Gerstl, T. Baumbach, S. Casalbuoni, A. Grau, M. Hagelstein, D. Saez de Jauregui
    Karlsruhe Institute of Technology
  • R. Cimino, M. Commisso, B. Spataro, A. Mostacci
    INFN/LNF
  • J. Clarke, D. Scott
    Science and Technology Facilities Council (STFC/DL/ASTeC) Daresbury Laboratory Accelerator Science and Technology Centre
  • M. Cox, J. Schouten
    Diamond Light Source Ltd (Diamond)
  • R. Jones, I. Shinton
    Cockcroft Institute
  • E. Wallen
    Lund University - MAX-Lab
  • R. Weigel
    Max-Planck Institute for Metal Research, Stuttgart
  • V. Baglin
    CERN
  • C. Boffo, G. Sikler
    Babcock Noell GmbH (BNG)
  • T. Bradshaw
    Science and Technology Facilities Council (STFC/RAL) Rutherford Appleton Laboratory
  One of the still open issues for the development of superconducting insertion devices is the understanding of the heat load induced by the beam passage. With the aim of measuring the beam heat load to a cold bore and in order to gain a deeper understanding in the beam heat load mechanisms, a cold vacuum chamber for diagnostics is under construction. We plan to have access with the same set-up to a number of different diagnostics, so we are implementing: i) retarding field analyzers to measure the electron flux, ii) temperature sensors to measure the total heat load, iii) pressure gauges, iv) and mass spectrometers to measure the gas content. The inner vacuum chamber will be removable in order to test different geometries and materials. COLDDIAG is built to fit in a short straight section at ANKA, but we are proposing its installation in different synchrotron light sources with different energies and beam characteristics. A first installation in DIAMOND is planned in June 2011. Here we describe the technical design report of this device and the planned measurements with beam.  
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FTR02 Simulation of Electron Cloud Induced Instabilities and Emittance Growth for CesrTA emittance, simulation, electron, betatron 203
 
  • M. Pivi
    SLAC National Accelerator Laboratory
  • G. Dugan, M. Palmer, K. Sonnad
    Cornell University - CLASSE
  As part of the international Linear Collider (ILC) collaboration, we have compared the electron cloud (EC) effect for different Damping Ring (DR) designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of the shorter damping ring with respect to the electron cloud build-up and related beam instabilities. The studies for a 3.2 km ring 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 considerable reduction of the number of components, wiggler magnets and costs. We also present the results for the luminosity upgrade option with shorter 3ns bunch spacing. In particular we will go through the evaluation of mitigation techniques for the ILC DR and discuss the integration of the CesrTA results into the Damping Ring design. Furthermore (with Kiran Sonnad, Cornell) we have performed detailed simulations using the CMAD code for CesrTA single-bunch instability and linear emittance growth below threshold and preliminary comparisons with experimental data are discussed here in view of the validation of the simulation codes prediction for the ILC DR.  
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