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Rubin, D.

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OPR06 CesrTA Program Overview 30
 
  • D. Rubin
    Cornell University - CLASSE
 
  The Cornell Electron Storage Ring (CESR) is configured as a test accelerator (CesrTA) for investigation of electron cloud phenomena in the regime of low emittance damping rings. The storage ring is equipped with superconducting damping wigglers and focusing optics to reduce horizontal emittance to 2.5 nm at 2.1GeV. The machine is instrumented with detectors (retarding field analyzers) to measure the growth of the electron cloud in wiggler magnets, dipoles, quadrupoles and field free drifts. Shielded button pickups are used to measure the time development of the cloud. A gated tune receiver is used to measure the cloud induced tune shift along a train of bunches and to identify sidebands associated with a head tail instability. An xray camera with high speed readout provides a single pass measurement of the vertical size of each bunch in a long train of bunches, so that emittance growth due to the electron cloud can be observed. Various mitigations are tested by installation of prepared vacuum chambers in association with retarding field analyzers. The phase shift in the transmission of a TE wave propagated between adjacent beam position monitors provides a measure of the local electron density, obviating the need for specialized detectors. We measure the energy dependence of the secondary emission yield of a variety of sample materials, including the effect of beam processing. We utilize high bandwidth precision beam position monitors to measure and correct transverse coupling and vertical dispersion in order to minimize vertical emittance. Our low emittance tuning procedure typically yields vertical emittance less than 20pm in one or two iterations, so that measurements of electron cloud effects peculiar to ultra-low emittance can be readily accomodated. Modeling and simulation of RFA detector response, electron cloud growth, electron cloud - beam interaction, cloud as plasma, and nonlinear beam dynamics provide context for interpretation of the experimental data, and motivation to pursue additional measurements and develop new experimental techniques.  
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PST11 CesrTA Low Emittance Tuning 134
 
  • D. Sagan, J. Shanks, Y. Yanay, D. Rubin
    Cornell University - CLASSE
 
  Low emittance tuning and characterization of electron cloud phenomena are central to the CesrTA R&D program. A small vertical emittance is required in order to be sensitive to the emittance diluting effects of the electron cloud. We have developed techniques to systematically and efficiently eliminate optical and alignment errors that are the sources of vertical emittance. Beam based measurements are used to center the beam position monitors with respect to the adjacent quadrupoles, determine the relative gains of the BPM button electrodes, and measure the BPM tilts, thus allowing precision measurement of transverse coupling and vertical dispersion. Low emittance also requires that the tune plane be relatively clear of nonlinear coupling resonances associated with sextupoles. We report on tests of a sextupole distribution designed to minimize resonance driving terms. We also report on efforts to measure sextupole strengths. Our standard low emittance tuning procedure typically yields sub 20pm emittance in one or two iterations. With tuning, we achieve a vertical emittance of ?v ~15 pm at 2.1 GeV.  
PST02 Bunch-By-Bunch Instrumentation Upgrades For CESR, Based On Requirements For The CESR Test Accelerator Research Program 88
 
  • N. Rider, J. Alexander, M. Billing, C. Conolly, N. Eggert, E. Fontes, W. Hopkins, B. Kreis, A. Lyndaker, R. Meller, M. Palmer, D. Peterson, M. Rendina, P. Revesz, D. Rubin, J. Savino, R. Seeley, J. Shanks, C. Strohman
    Cornell University - CLASSE
  • R. Holtzapple
    California Polytechnic State University
  • J. Flanagan
    KEK
 
  The research focus of the CESR Test Accelerator program requires new instrumentation hardware, software and techniques in order to accurately investigate beam dynamics in the presence of electron cloud effects. These new instruments are also required to develop low emittance beam conditions which are key to the success of the damping ring design for the International Linear Collider. This poster will detail some of the architecture and tools which have been developed to support these efforts. Emphasis will be placed on the 4 nS bunch by bunch Beam Position Monitoring system as well as the 4 nS capable X-ray Beam Size Monitor.