ECLOUD10 - List of Keywords (positron)

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positron

Paper	Title	Other Keywords	Page
MIT00	e-Cloud Activity of DLC and TiN Coated Chambers at KEKB Positron Ring	electron, vacuum, ion, synchrotron	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.
	Slides

DYN05	Electron Cloud Instability in Low Emittance Rings	electron, emittance, simulation, single-bunch	76
	K. Ohmi, H. Jin, Y. Susaki KEK
	We discuss single bunch instability in low emittance rings, especially focus side band appearance. Multi-bunch instability due to electron cloud in bending field is discussed.
	Slides

PST03	Methods for Quantitative Interpretation of Retarding Field Analyzer Data	simulation, electron, photon, 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.

PST04	TE Wave Measurements at CesrTA	resonance, electron, wiggler, plasma	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.

PST05	Progress on Simulation of Beam Dynamics with Electron Cloud Effects: An update	electron, simulation, emittance, lattice	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.

PST09	Electron Cloud Modeling Results for Time-Resolved Shielded Pickup Measurements at CesrTA	electron, pick-up, vacuum, simulation	123
	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.

PST10	Using Coherent Tune Shifts to Evaluate Electron Cloud Effects on Beam Dynamics at CesrTA	simulation, electron, dipole, photon	130
	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.

DIA03	Analysis of the Electron Cloud Density Measurement With RFA in a Positron Ring	electron, quadrupole, simulation, 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.
	Slides

FTR00	ILC Damping Rings: Benefit of the Antechamber or: Antechamber vs. SEY	electron, simulation, 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.
	Slides