| Paper |
Title |
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| WEOAC01 |
Secondary Electron Yield and Rectangular Groove Chamber Tests in PEP-II
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1997 |
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- M. T.F. Pivi
- R. E. Kirby, T. W. Markiewicz, T. O. Raubenheimer, J. Seeman, L. Wang
SLAC, Menlo Park, California
- F. Le Pimpec
PSI, Villigen
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Funding: Work supported by the Director, Office of Science, High Energy Physics, U. S. DOE under Contract No. DE-AC02-76SF00515.
Possible remedies for the electron cloud in the Damping Ring of the International Linear collider includes conditioning of the surface and chamber with grooves. We installed chambers in PEP-II to test the secondary electron yield (SEY) of coated TiN and TiZrV NEG samples and study the effect of electron and photon conditioning in situ. We have also installed vacuum chambers with rectangular groove profile in straight sections to test this possible mitigation technique. In this paper, we will describe the PEP-II test layout, results and impact on impedance.
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| WEOAC02 |
A New Type of Distributed Enamel Based Clearing Electrode
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2000 |
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- F. Caspers
- F.-J. Behler
Eisenwerke Fried. Wilh. Dueker GmbH & Co. KGaA, Laufach
- P. P. Hellmold
Clausthal, Inst für Nichtmetall. Werkstoffe, Clausthal-Zellerfeld
- T. Kroyer, E. Metral, F. Zimmermann
CERN, Geneva
- J. Wendel
Wendel GmbH, Dillenburg
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A practical technology for implanting thin strip-like enamel structures in metallic beam-pipes, to be used for e-cloud clearing, has been developed. We discuss the technical and technological issues of this method. Parameters of particular interest are the beam coupling impedance as a function of the conductive coating resistivity and also the secondary electron yield. A test-stand for multipactoring measurements on a first prototype using the coaxial resonator method is described.
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Slides
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| WEOAC03 |
Transverse Impedance of LHC Collimators
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2003 |
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- E. Metral
- G. Arduini, R. W. Assmann, A. Boccardi, T. Bohl, C. B. Bracco, F. Caspers, M. Gasior, O. R. Jones, K. K. Kasinski, T. Kroyer, S. Redaelli, G. Robert-Demolaize, G. Rumolo, R. J. Steinhagen, Th. Weiler, F. Zimmermann
CERN, Geneva
- F. Roncarolo
UMAN, Manchester
- B. Salvant
EPFL, Lausanne
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The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most of which are made of Fibre-Reinforced-Carbon to withstand the impacts of high intensity proton beams in case of failures, and which will be moved very close to the beam, with full gaps of few millimetres, in order to protect surrounding super-conducting equipments. We present an estimate of the transverse resistive-wall impedance of the LHC collimators, the total impedance in the LHC at injection and top energy, the induced coupled-bunch growth rates and tune shifts, and finally the result of the comparison of the theoretical predictions with measurements performed in 2004 and 2006 on a prototype collimator installed in the SPS.
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Slides
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| WEOAC04 |
Impedance Minimization by Nonlinear Tapering
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2006 |
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- B. Podobedov
- I. Zagorodnov
DESY, Hamburg
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There exist analytical approximations that express the transverse geometric impedance of tapered transitions in the inductive regime as a functional of the transition boundary and its derivatives. Assuming the initial and final cross-sections and the transition length are fixed, one can minimize these functionals by appropriate choice of the boundary variation with the longitudinal coordinate. In this paper we numerically investigate how well this works for the cases of optimized tapered transitions in circular, elliptical and rectangular geometry by running ABCI, ECHO, and GDFIDL EM field solvers. We show that a significant reduction of impedance for optimized boundary compared to that of a linear taper is indeed possible in some cases, and then we compare this reduction to analytical predictions.
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Slides
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