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Title |
Other Keywords |
Page |
| OPR05 |
Emittance Growth and Tune Spectra at PETRA III
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electron, simulation, synchrotron, wiggler |
21 |
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- R. Wanzenberg
DESY
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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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| OPR06 |
CesrTA Program Overview
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electron, damping, wiggler, pick-up |
30 |
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- D. Rubin
Cornell University - CLASSE
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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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Slides
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| DYN03 |
Studies of the Electron-Cloud-Induced Beam Dynamics at CesrTA
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electron, betatron, single-bunch, synchrotron |
60 |
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| DYN05 |
Electron Cloud Instability in Low Emittance Rings
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electron, simulation, positron, single-bunch |
76 |
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| PST00 |
E-Cloud Effects on Single-Bunch Dynamics in the Proposed PS2
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electron, simulation, extraction, injection |
79 |
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- M. Venturini, M. Furman, J. Vay
LBNL
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One of the options considered for a future aupgrade of the LHC injection complex entails the replacement of PS with PS2, a larger circumference and higher-energy synchrotron. Electron cloud has been identified as a potential limitation to the machine performance. We review studies of e-cloud build-up and present recent results of simulations of short-term e-cloud effects on the single-bunch dynamics in the smooth-lattice, quasi-static approximation, as implemented in the code Warp.
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| PST05 |
Progress on Simulation of Beam Dynamics with Electron Cloud Effects: An update
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electron, simulation, lattice, positron |
100 |
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- K. Sonnad
Cornell University - CLASSE
- M. Pivi
SLAC National Accelerator Laboratory
- J. Vay
LBNL
- G. Rumolo, R. Tomas, F. Zimmermann
CERN
- G. Franchetti
GSI
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In this presentation, we will report the progress made in the past few years on simulations to study the electron cloud effects on the dynamics of beams in cicular accelerators. Results associated with various acclerators such as the Fermilab Main Injector, SPS, LHC, ILC damping rings will be shown. Comparisions between the results obtained from three codes, namely Warp, HeadTail and CMad will be discussed. More recent studies done on CesrTA will be discussed in greater detail.
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| PST11 |
CesrTA Low Emittance Tuning
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quadrupole, coupling, sextupole, betatron |
134 |
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- D. Sagan, J. Shanks, Y. Yanay, D. Rubin
Cornell University - CLASSE
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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.
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| FTR02 |
Simulation of Electron Cloud Induced Instabilities and Emittance Growth for CesrTA
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simulation, electron, betatron, synchrotron |
203 |
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- M. Pivi
SLAC National Accelerator Laboratory
- G. Dugan, M. Palmer, K. Sonnad
Cornell University - CLASSE
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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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