| Paper |
Title |
Other Keywords |
Page |
| OPR00 |
Recent Studies of the Electron Cloud Induced Beam Instability at the Los Alamos PSR
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accumulation, linac, simulation, space-charge |
1 |
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- R. Macek, L. Rybarcyk, R. McCrady, T. Zaugg
LANL
- J. Holmes
ORNL
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Recent beam studies have focused on two aspects of the observed e-p instability at the Los Alamos Proton Storage Ring (PSR). 1) Most recently it has been observed that a stable beam with the standard production bunch width (290 ns injected beam bunch width) will become e-p unstable when the bunch width is shortened to 200 ns or less. This was not the case years earlier. Experimental characteristics and possible explanations of this recent “short pulse instability phenomenon” will be presented. 2) Other beam studies have focused on understanding the main sources and locations of electron clouds (EC), which drive the observed e-p instability. Significant EC signals are observed in drift spaces and quadrupole magnets at PSR which together cover ~65% of the ring circumference. Results making use of two longitudinal barriers to isolate the drift space electron diagnostic have provided definitive evidence that most of the drift space EC signal is “seeded” by electrons ejected longitudinally by ExB drifts from adjacent quadrupole magnets. This result can explain why weak solenoids and TiN coatings in several drifts spaces had no effect on the e-p instability threshold. Modeling of EC generation in 3D quadrupoles using a modified version of the POSINST code shows that a sizeable fraction of the electrons generated in the quadrupoles are ejected longitudinally into the adjacent drifts. The experimental findings and simulation results of this focus will be summarized.
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Slides
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| OPR02 |
Recent Experimental Results on Amorphous Carbon Coatings for Electron Cloud Mitigation
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dipole, vacuum, cathode, proton |
6 |
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- C. Yin Vallgren, S. Calatroni, P. Chiggiato, P. Costa Pinto, H. Neupert, M. Taborelli, G. Rumolo, E. Shaposhnikova, W. Vollenberg
CERN
| |
Amorphous carbon (a-C) thin films, produced in different coating configurations by using d.c magnetron sputtering, have been investigated in laboratory for low secondary electron yield (SEY) applications. After the coatings had shown a reliable low initial SEY, the a-C thin films have been applied in the SPS and tested with LHC type beams. Currently, we have used a-C thin film coated in so-called liner configuration for the electron cloud monitors as well as for a removable sample. In addition the vacuum chambers of three dipole magnets have been coated and inserted in the machine. After describing the different configurations used for the coatings, results of the tests in the machine and a summary of the analyses after extraction will be presented. Based on comparison between different coating configurations, a new series of coatings has been applied on three further dipole magnet vacuum chambers. They have been installed and will be tested in coming machine development runs.
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Slides
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| OPR03 |
Can Electron Multipacting Explain the Pressure Rise in the Cold Bore ANKA Superconducting Undulator?
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vacuum, undulator, photon, simulation |
12 |
| |
- S. Casalbuoni, S. Schleede, M. Hagelstein, D. Saez de Jauregui, P. Tavares
Karlsruhe Institute of Technology
| |
Preliminary studies performed with the cold bore superconducting undulator installed in the ANKA (Angstrom source Karlsruhe) storage ring suggest that the beam heat load is mainly due to the electron wall bombardment. Electron bombardment can both heat the cold vacuum chamber and induce an increase in the pressure because of gas desorption. In this contribution we compare the measurements of the pressure in a cold bore performed in the electron storage ring ANKA with the predictions obtained using the equations of gas dynamic balance in a cold vacuum chamber exposed to synchrotron radiation and electron bombardment. The balance results from two competing effects: the photon and electron stimulated desorption of the gas contained in the surface layer of the chamber wall and of the gas cryosorbed, and the cryopumping by the cold surface. We show that photodesorption alone cannot explain the experimental results and that electron multipacting is needed to reproduce the observed pressure rise. Electron bombardment can at the same time explain the observed beam heat load.
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Slides
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| OPR05 |
Emittance Growth and Tune Spectra at PETRA III
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emittance, simulation, synchrotron, 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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Slides
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| OPR06 |
CesrTA Program Overview
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emittance, damping, wiggler, pick-up |
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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Slides
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| MIT00 |
e-Cloud Activity of DLC and TiN Coated Chambers at KEKB Positron Ring
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positron, vacuum, ion, synchrotron |
37 |
| |
- S. Kato, M. Nishiwaki
KEK
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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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Slides
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| MIT03 |
Experimental Efforts at LNF to Reduce Secondary Electron Yield in Particle Accelerators
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radiation, vacuum, synchrotron, synchrotron-radiation |
46 |
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- R. Cimino, M. Commisso, T. Demma, D. Grosso
INFN/LNF
- N. Mahne, A. Giglia
CNR-IOM
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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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Slides
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| DYN02 |
Simulated Performance of an FIR-Based Feedback System to Control the Electron Cloud Single-Bunch Transverse Instabilities in the CERN SPS
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kicker, feedback, simulation, controls |
56 |
| |
- R. Secondo, J. Byrd, M. Furman, M. Venturini, J. Vay
LBNL
- J. Fox, C. Rivetta
SLAC National Accelerator Laboratory
- W. Hofle
CERN
| |
The performance of High Energy proton machines like the SPS at CERN is affected by transverse single-bunch instabilities due to the Electron Cloud effect. In a first step to model a Feedback control system to stabilize the bunch dynamics, we use a Finite Impulse Response filter to represent the processing channel. The effect of this simplified processing channel in the bunch dynamics is analyzed using the simulation package WARP-POSINST. We report on simulation results, discuss the basic features of the feedback model and present our plans for further development of the numerical models used in the simulations.
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Slides
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| DYN03 |
Studies of the Electron-Cloud-Induced Beam Dynamics at CesrTA
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betatron, emittance, single-bunch, synchrotron |
60 |
| |
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| DYN05 |
Electron Cloud Instability in Low Emittance Rings
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emittance, 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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simulation, emittance, extraction, injection |
79 |
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- M. Venturini, M. Furman, J. Vay
LBNL
| |
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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| PST01 |
Implementation and Operation of Electron Cloud Diagnostics for CesrTA
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vacuum, diagnostics, quadrupole, pick-up |
83 |
| |
- Y. Li, X. Liu, V. Medjidzade, J. Conway, M. Palmer
Cornell University - CLASSE
| |
The vacuum system of Cornell Electron Storage Ring (CESR) was successfully reconfigured to support CesrTA physics programs, including electron cloud (EC) build-up and suppression studies. One of key features of the reconfigured CESR vacuum system is the flexibility for exchange of various vacuum chambers with minimized impact to the accelerator operations. This is achieved by creation of three short gate-valve isolated vacuum sections. Over the last three years, many vacuum chambers with various EC diagnostics (such as RFAs, shielded pickups, etc) were rotated through these short experimental sections. With these instrumented test chambers, EC build-up was studied in many magnetic field types, including dipoles, quadrupoles, wigglers and field-free drifts. EC suppression techniques by coating (TiN, NEG and a-C), surface textures (grooves) and clearing electrode are incorporated in these test chambers to evaluate their effectiveness. We present the implementation and operations of EC diagnostics.
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| PST03 |
Methods for Quantitative Interpretation of Retarding Field Analyzer Data
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simulation, photon, positron, pick-up |
91 |
| |
- J. Calvey, J. Crittenden, G. Dugan, M. Palmer
Cornell University - CLASSE
- K. Harkay
Argonne National Laboratory
| |
A great deal of Retarding Field Analyzer (RFA) data has been taken as part of the CesrTA program at Cornell. Obtaining a quantitative understanding of this data requires use of cloud simulation programs, as well as a detailed model of the RFA itself. In some cases the RFA can be modeled by postprocessing the output of a simulation codes, and one can obtain “best fit” values for important simulation parameters using a systematic method to improve agreement between data and simulation. In other cases, in particular in high magnetic field regions, the presence of the RFA can have an effect on the cloud, and one needs to include a model of the RFA in the simulation program itself.
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| PST04 |
TE Wave Measurements at CesrTA
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resonance, wiggler, plasma, positron |
95 |
| |
- J. Sikora
Cornell University - CLASSE
- S. De Santis
LBNL
- K. Hammond
Harvard University
| |
Funding: This work is supported by the US National Science Foundation PHY-0734867, and the US Department of Energy DE-FC02-08ER41538
TE Wave measurement systems have been installed in the L0 and L3 regions of CesrTA. L0 is the location of 6 superconducting wiggler magnets; L3 has round beampipe through a chicane magnet (PEPII) and a NEG coated chamber. At both locations, rf relays are used to multiplex signals from a signal generator output, through the beampipe, and to the input of a spectrum analyzer. Software monitors can be triggered to take data on demand, or on changes in accelerator conditions such as beam current or wiggler fields. The poster will describe the TE Wave measurement technique, the installation of hardware at CesrTA and some measurement examples. It will also outline some of the problems in the interpretation of data, specifically the results of reflections and standing waves.
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| PST05 |
Progress on Simulation of Beam Dynamics with Electron Cloud Effects: An update
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simulation, emittance, lattice, positron |
100 |
| |
- K. Sonnad
Cornell University - CLASSE
- M. Pivi
SLAC National Accelerator Laboratory
- J. Vay
LBNL
- G. Rumolo, R. Tomas, F. Zimmermann
CERN
- G. Franchetti
GSI
| |
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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| PST06 |
Effects of Reflections on TE-Wave Measurements of Electron Cloud Density
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simulation, plasma, controls, background |
103 |
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- K. Sonnad, J. Sikora
Cornell University - CLASSE
- K. Hammond
Harvard University
- S. Veitzer
Tech-X Corporation
| |
The simulation code VORPAL has been used as a tool to study charecteristics of TE wave transmission in the presence of electron clouds for CesrTA. We look at how the electron cloud induced phase shift is influenced by (1) reflections of the wave, caused by possible protrusions in the beam pipe and (2)effect of nonuniformities of the cloud density distribution in the transverse plane.
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| PST07 |
Techniques for Observing Beam Dynamical Effects Caused by the Presence of Electron Clouds
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betatron, kicker, feedback, dipole |
108 |
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| PST09 |
Electron Cloud Modeling Results for Time-Resolved Shielded Pickup Measurements at CesrTA
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pick-up, vacuum, simulation, positron |
123 |
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- J. Crittenden, Y. Li, X. Liu, M. Palmer, J. Sikora
Cornell University - CLASSE
- S. Calatroni, G. Rumolo
CERN
- N. Omcikus
University of California at Los Angeles
| |
The Cornell Electron Storage Ring Test Accelerator (CesrTA) program includes investigations into electron cloud buildup, applying various mitigation techniques in custom vacuum chambers. Among these are two 1.1-m-long sections located symmetrically in the east and west arc regions. These chambers are equipped with pickup detectors shielded against the direct beam-induced signal. They detect cloud electrons migrating through an 18-mm-diameter pattern of holes in the top of the chamber. A digitizing oscilloscope is used to record the signals, providing time-resolved information on cloud development. Carbon-coated, TiN-coated and uncoated aluminum chambers have been tested. Electron and positron beams of 2.1, 4.0 and 5.3 GeV with a variety of bunch populations and spacings in steps of 4 and 14 ns have been used. Here we report on results from the ECLOUD modeling code which highlight the sensitivity of these measurements to model parameters such as the photoelectron azimuthal and energy distributions at production, and the secondary yield parameters including the true secondary, rediffused, and elastic yield values. In particular, witness bunch studies exhibit high sensitivity to the elastic yield by providing information on cloud decay times.
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| PST10 |
Using Coherent Tune Shifts to Evaluate Electron Cloud Effects on Beam Dynamics at CesrTA
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simulation, positron, dipole, photon |
130 |
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- D. Kreinick, J. Crittenden, G. Dugan, Z. Leong, M. Palmer
Cornell University - CLASSE
- R. Holtzapple, M. Randazzo
California Polytechnic State University
- M. Furman, M. Venturini
LBNL
| |
One technique used at CesrTA for studying the effects of electron clouds on beam dynamics is to measure electron and positron bunch tunes under a wide variety of beam energies, bunch charge, and bunch train configurations. Comparing the observed tunes with the predictions of various simulation programs allows the evaluation of important parameters in the cloud formation models. These simulations will be used to predict the behavior of the electron cloud in damping rings for future linear colliders.
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| PST12 |
In Situ SEY Measurements at CesrTA
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gun, vacuum, radiation, controls |
140 |
| |
- J. Kim, J. Conway, S. Greenwald, Y. Li, T. Moore, M. Palmer, V. Medjidzade, D. Asner, C. Strohman
Cornell University - CLASSE
| |
Measuring secondary electron yields (SEYs) on technical surfaces in accelerator vacuum systems provides essential information for many accelerator R&D projects, such as the ILC Damping Rings, regarding to electron cloud growth and suppression. As a part of CesrTA research program, we developed and deployed SEY in-situ measurement systems. Two such SEY systems were installed to expose samples with direct and scattered synchrotron radiation (SR), and the SEYs of the samples were measured as a function of SR dosages. In this poster, we describe the in-situ SEY measurement systems and the initial results on bare aluminum and TiN-coated aluminum samples.
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| MOD01 |
Analysis of Synchrotron Radiation using SYNRAD3D and Plans to Create a Photoemission Model
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photon, wiggler, radiation, damping |
147 |
| |
- L. Boon, A. Garfinkel
Purdue University
- K. Harkay
Argonne National Laboratory
| |
Electron cloud data from electron rings suggest that the photoelectron model in electron cloud generation codes is incomplete. The photoelectron model will be important in modeling the cloud generation on components downstream of wigglers, which can produce a very high photon flux on the wall in a local region. The code SYNRAD3D has been developed in the context of the Bmad accelerator physics software library. SYNRAD3D includes computation of synchrotron radiation and propagation in 3D through a vacuum chamber. The probability of reflection vs. absorption of the photons on the chamber wall is included, using data from the literature. We used SYNRAD3D to model the photon flux for the ILC damping ring. For simplicity in modeling, we started with a round chamber and varied parameters such as the number of simulation-generated photons, bin size, photon energy cutoff, and whether photons reflect off the wall. With a realistic photon flux and distribution, we can study models for the photoemission. Preliminary work has begun to develop a photoelectron model using Retarding Field Analyzer (RFA) data. The work to date and future plans are described.
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Slides
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| MOD03 |
Accurate Simulation of the Electron Cloud in the Fermilab Main Injector with VORPAL
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simulation, proton, dipole, quadrupole |
152 |
| |
- P. Lebrun, P. Spentzouris
Fermilab
- J. Cary
University of Colorado Boulder
- S. Veitzer, P. Stoltz
Tech-X Corporation
| |
We present results from a precision simulation of the electron cloud (EC) problem in the Fermilab Main Injector using the code VORPAL. Fully 3D and self consistent that include both distributions of electrons in 6D phase-space and E. M. field maps. Various configurations of the magnetic fields found around the machine have been studied. Plasma waves associated to the fluctuation density of the cloud have been analyzed. Our results are compaired with those obtained with the POSINST code. It is shown that the 3D effects are important. The response of a Retarding Field Analyzer (RFA) to the EC has been simulated, as well as the more challenging microwave absorption experiment. Definite predictions of their exact response are difficult to compute, mostly because of the uncertainties in the secondary emission yield and, in the case of the RFA, because of the sensitivity of the electron collection efficiency to unknown stray magnetic fields. Nonetheless, our simulations do provide guidance to the experimental program.
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Slides
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| MOD04 |
Modeling Electron Cloud Buildup and Microwave Diagnostics using VORPAL
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simulation, plasma, diagnostics, higher-order-mode |
162 |
| |
- S. Veitzer, P. Stoltz
Tech-X Corporation
- K. Sonnad
Cornell University - CLASSE
- P. Lebrun
Fermilab
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We present an overview of recent electron cloud modeling results using the multi-dimensional, parallel, plasma simulation code VORPAL. We have used VORPAL to model cloud buildup in dipole, quadrupole, and field-free magnetic field configurations, in both circular and elliptical cross section pipes relevant to microwave diagnostics at the PEP-II experiment at SLAC, and ongoing experiments in the Main Injector at Fermilab. In addition, we present preliminary results for modeling electron orbits in the CesrTA wiggler, which is the beginning of a more detailed modeling effort to understand electron cloud effects in electron/positron accelerators, as well as connecting microwave side-band measurements to cloud densities. We also report on recent 3-Dimensional microwave transmission simulations through uniform and non-uniform clouds, and with higher order TE and TM waves using VORPAL.
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Slides
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| MOD05 |
Trapping of Electron Cloud in ILC / CesrTA Quadrupole and Sextupole Magnets
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quadrupole, sextupole, simulation, damping |
167 |
| |
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| DIA00 |
Electron Cloud Studies in the Fermilab Main Injector Using Microwave Transmission
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proton, lattice, dipole, plasma |
173 |
| |
- J. Thangaraj, N. Eddy, R. Zwaska, K. Seiya, I. Kourbanis, J. Crisp
Fermilab
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In this paper, we present recent results from our measurement at the Fermilab Main Injector through microwave transmission in a beam pipe. We present three types of measurement techniques. In the first technique, we use time-resolved direct phase shift measurement to measure the e-cloud density. In the second and third techniques, we look for side bands in the frequency spectrum with or without frequency span by collecting turns of data. Finally, we also discuss the resonant BPM method, where a signal below the waveguide cutoff is sent through a one side of the BPM and is collected on the other side of the BPM to look for phase shift due to electron cloud. We present experimental results taken from MI40 and MI52 section of the main injector.
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Slides
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| DIA02 |
The Ecloud Measurement Setup in the Main Injector
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proton, vacuum, simulation, antiproton |
177 |
| |
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| DIA03 |
Analysis of the Electron Cloud Density Measurement With RFA in a Positron Ring
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quadrupole, simulation, positron, synchrotron |
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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Slides
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| DIA04 |
Status of COLDDIAG: a Cold Vacuum Chamber for Diagnostics
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vacuum, diagnostics, synchrotron, 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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Slides
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| FTR00 |
ILC Damping Rings: Benefit of the Antechamber or: Antechamber vs. SEY
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simulation, positron, dipole, photon |
194 |
| |
- M. Furman
LBNL
| |
We review the simulation results for the electron cloud build-up for the ILC Damping Rings, for both lattice options considered (6 km and 3 km), in a field-free region and in a bending dipole magnet. While the 6 km lattice is slightly more forgiving than the 3-km lattice vis-a-vis the electron cloud effects, we conclude that, in general, the existence of an antechamber helps to dramatically reduce the electron-cloud density (factor ~50) only if the peak secondary yield of the chamber surface is below a certain critical value. This critical value is in the range ~1.1~1.3, depending on various details.
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Slides
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| FTR02 |
Simulation of Electron Cloud Induced Instabilities and Emittance Growth for CesrTA
|
emittance, simulation, betatron, synchrotron |
203 |
| |
- 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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Slides
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