damping

Paper	Title	Other Keywords	Page
OPR06	CesrTA Program Overview	electron, emittance, 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.
	Slides
PST02	Bunch-By-Bunch Instrumentation Upgrades For CESR, Based On Requirements For The CESR Test Accelerator Research Program	instrumentation, optics, controls, monitoring	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.
MOD01	Analysis of Synchrotron Radiation using SYNRAD3D and Plans to Create a Photoemission Model	photon, wiggler, radiation, electron	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.
	Slides
MOD05	Trapping of Electron Cloud in ILC / CesrTA Quadrupole and Sextupole Magnets	electron, quadrupole, sextupole, simulation	167
	M. Pivi, L. Wang SLAC National Accelerator Laboratory
	This talk will discuss the electron trapping mechanism in quadrupole and sextupole magnets. We will present the results in CESRTA and ILC quadrupole and sextupole magnets.
	Slides