PAC07 - List of Authors (Zimmermann, F.)

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Zimmermann, F.

Paper	Title	Page
MOPAN023	Superconductive Damping Wigglers for the CLIC Project	200
	R. Rossmanith, S. Casalbuoni, A. W. Grau, M. Hagelstein, B. K. Kostka FZK, Karlsruhe T. Baumbach, A. Bernhard, A.-S. Muller, D. Wollmann University of Karlsruhe, Karlsruhe H.-H. Braun, M. Korostelev, Y. Papaphilippou, F. Zimmermann CERN, Geneva E. M. Mashkina, E. Steffens University of Erlangen-Nurnberg, Physikalisches Institut II, Erlangen
	The CLIC damping ring requires wigglers with both high on-axis fields and short periods. The present design foresees a superconductive wiggler with a period length of 5 cm, a peak on-axis field of 2.5 T and a full width aperture of 12 mm. In this paper we explore the performance improvements of the damping ring when these parameters are pushed to 2.7 T at a period length of 2 cm with the expense of a reduced aperture of 5 mm. A design for a prototype for testing the field quality of such a wiggler is presented in this paper and the possibility to test this wiggler with beam in the storage ring ANKA is described.
TUZAKI02	LHC Upgrade Scenarios	714
	F. Zimmermann CERN, Geneva
	Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395) The EU CARE-HHH and US-LARP programmes for an LHC upgrade aim at increasing the LHC luminosity by a factor of 10 around the year 2015. The upgrade plan envisages rebuilding the interaction regions (IRs) and modifying the beam parameters. In addition to advanced low-beta quadrupoles, the future IRs may accommodate other novel elements such slim s.c. dipoles or quadrupoles embedded deep inside the detectors, global low-angle crab cavities, and wire compensators of long-range beam-beam effects. Important constraints on the upgrade path are the maximum acceptable number of detector pile-up events, favoring many closely spaced bunches, and the heat load on the cold-magnet beam screens, pointing towards fewer and more intense bunches. In addition, the upgrade of the LHC ring proper should be complemented by an upgrade of the injector complex. I will present preferred luminosity upgrade scenarios for the LHC IRs and beam parameters, sketch accompanying injector enhancements, and comment on a longer-term LHC energy upgrade.
	Slides
TUPAN048	Beam-beam Effects With an External Noise in LHC	1496
	K. Ohmi KEK, Ibaraki R. Calaga BNL, Upton, Long Island, New York W. Hofle, R. Tomas, F. Zimmermann CERN, Geneva
	Proton beam do not have any damping mechanism for an incoherent betatron motion. A noise, which kicks beam particles in the transverse plane, gives a coherent betatron amplitude. Nonlinear force due to the beam-beam interactions causes a decoherence for the betatron motion with keeping an amplitude of each beam particle, with the result that an emittance growth arises. We focus fast transverse turn by turn noises caused by a bunch by bunch feedback system and a cavity phase zitter in crab collision.
TUPAN085	LHC Impedance Reduction by Nonlinear Collimation	1571
	J. Resta-Lopez, A. Faus-Golfe IFIC, Valencia F. Zimmermann CERN, Geneva
	A nonlinear collimation system can allow larger aperture for the mechanical jaws, and it thereby can help to reduce the collimator impedance, which presently limits the LHC beam intensity. Assuming the nominal LHC beam at 7 TeV, we show how a nonlinear betatronic collimation insertion would reduce considerably the LHC coherent tune shift for the most critical coupled-bunch mode as compared with the conventional baseline linear collimation system of Phase-I. In either case, the tune shifts of the most unstable modes are compared with the stability diagrams for Landau damping.
TUPAN091	LHC Beam-beam Compensation Using Wires and Electron Lenses	1589
	U. Dorda, F. Zimmermann CERN, Geneva W. Fischer BNL, Upton, Long Island, New York V. D. Shiltsev Fermilab, Batavia, Illinois
	We present weak-strong simulation results for a possible application of current-carrying wires and electron lenses to compensate the LHC long-range and head-on beam-beam interaction, respectively, for nominal and Pacman bunches. We show that these measures have the potential to considerably increase the beam-beam limit, allowing for a corresponding increase in peak luminosity
TUPAS067	Electron Cloud in the Wigglers of The Positron Damping Ring of the International Linear Collider	1808
	L. Wang SLAC, Menlo Park, California F. Zimmermann CERN, Geneva
	Funding: Work supported by the U. S. Department of Energy under contract DE-AC02-76SF00515 The ILC positron damping ring comprises hundreds of meters of wiggler sections, where many more photons than in the arcs are emitted, and with the smallest beam-pipe aperture of the ring. A significant electron-cloud density can therefore be accumulated via photo-emission and via beam-induced multipacting. In field-free regions the electron-cloud build up may be suppressed by adding weak solenoid fields, but the electron cloud remaining in the wigglers as well as in the arc dipole magnets can still drive single-bunch and multi-bunch beam instabilities. This paper studies the electron-cloud formation in an ILC wiggler section for various scenarios, as well as its character, and possible mitigation schemes.
TUPAS089	Small Angle Crab Compensation for LHC IR Upgrade	1853
	R. Calaga BNL, Upton, Long Island, New York K. Akai, K. Ohmi, K. Oide KEK, Ibaraki U. Dorda, R. Tomas, F. Zimmermann CERN, Geneva
	Funding: This work is partially supported by the U. S. DOE A small angle (< 1mrad) crab scheme is an attractive option for the LHC luminosity upgrade to recover the geometric luminosity loss from the finite crossing angle, which steeply increases to unacceptable levels as the IP beta function is reduced below its nominal value. The crab compensation in the LHC can be accomplished using only two sets of deflecting rf cavities, placed in collision-free straight sections of LHC to nullify the crossing angles at IP1 & IP5. We present IR optics configurations with low-angle crab crossing, study the beam-beam performance and proton-beam emittance growth in the presence of crab compensation, lattice errors, crab RF noise sources. We also explore a 400MHz superconducting cavity design and discuss the pertinent RF challenges.
WEOAC02	A New Type of Distributed Enamel Based Clearing Electrode	2000
	F. Caspers, T. Kroyer, E. Metral, F. Zimmermann CERN, Geneva F.-J. Behler Eisenwerke Fried. Wilh. Dueker GmbH & Co. KGaA, Laufach C. Dr. Wendel Wendel GmbH, Dillenburg P. P. Hellmold Clausthal, Inst für Nichtmetall. Werkstoffe, Clausthal-Zellerfeld
	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.
	Slides
THPMN064	Luminosity Upgrade of CLIC-LHC ep/gp Collider	2853
	H. Aksakal, A. K. Ciftci, Z. Nergiz Ankara University, Faculty of Sciences, Tandogan/Ankara D. Schulte, F. Zimmermann CERN, Geneva
	An energy-frontier or QCD-exploring ep and gp collider can be realized by colliding high-energy photons generated by Compton back-scattered off a CLIC electron beam, at either 75 GeV or 1.5 TeV, with protons or ions stored in the LHC. In this study we discuss a performance optimization of this type of collider by tailoring the parameters of both CLIC and LHC. An estimate of the ultimately achievable luminosity is given.
THPMN065	Laser Collimation for Linear Colliders	2856
	H. Aksakal Ankara University, Faculty of Sciences, Tandogan/Ankara J. Resta-Lopez IFIC, Valencia F. Zimmermann CERN, Geneva
	We explore the possibility of laser-based postlinac beam collimation in future linear colliders. A laser employed as a spoiler can neither be 'destroyed' by the beam impact and nor generate collimator wake fields. In addition, the postlinac collimation section, presently the longest part of linear-collider beam delivery systems, can be shortened. In this paper, we investigate different types of laser modes for use as spoiler. Suitable laser beam parameters and modes are discussed for collimation in both CLIC and ILC.
TUPMN024	Measurements of the Beam Heat Load in the Cold Bore Superconductive Undulator Installed at ANKA	968
	S. Casalbuoni, A. W. Grau, M. Hagelstein, B. K. Kostka, R. Rossmanith FZK, Karlsruhe T. Baumbach, A. Bernhard, D. Wollmann University of Karlsruhe, Karlsruhe E. M. Mashkina, E. Steffens University of Erlangen-Nurnberg, Physikalisches Institut II, Erlangen F. Zimmermann CERN, Geneva
	The beam heat load in the cold bore superconductive undulator installed at ANKA has been monitored for almost two years. The possible sources of the observed heat load as synchrotron radiation from upstream magnets, image currents, photo-excited electrons and ions will be discussed and compared with the experimental results.
TUPAS095	Experiments with a DC Wire in RHIC	1859
	W. Fischer, N. P. Abreu, R. Calaga, G. Robert-Demolaize BNL, Upton, Long Island, New York U. Dorda, J.-P. Koutchouk, F. Zimmermann CERN, Geneva A. C. Kabel SLAC, Menlo Park, California H. J. Kim, T. Sen Fermilab, Batavia, Illinois J. Qiang LBNL, Berkeley, California
	Funding: Work supported by U. S. DOE under contract No DE-AC02-98CH1-886. A DC wire has been installed in RHIC to explore the long-range beam-beam effect, and test its compensation. We report on experiments that measure the effect of the wire's electro-magnetic field on the beam's lifetime and tune distribution, and accompanying simulations.
WEOAC03	Transverse Impedance of LHC Collimators	2003
	E. Metral, G. Arduini, R. W. Assmann, A. Boccardi, T. Bohl, C. 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
	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.
	Slides
THPAN066	Improvements in FAKTOR2, a Code to Simulate Collective Effect of Electrons and Ions	3375
	W. Bruns, D. Schulte, F. Zimmermann CERN, Geneva
	Funding: Supported by the European Community under the 6th Framework Programme "Structuring the European Research Area". The electrostatic Particle in Cell code 'Faktor2' is extended to 3D, and is parallelised. Results for electron cloud buildup in end regions of damping ring dipoles for next generation linear colliders are presented.
THPAN072	A Concept for the LHC Luminosity Upgrade Based on Strong Beta* Reduction Combined with a Minimized Geometrical Luminosity Loss Factor	3387
	E. Todesco, R. W. Assmann, J.-P. Koutchouk, E. Metral, G. Sterbini, F. Zimmermann, R. de Maria CERN, Geneva
	A significant increase of the LHC beam current touches physics limits as collective effects, electron-cloud, heat load, collimation and machine protection. We propose an upgrade scheme mainly based on a stronger focusing, with a beta* of 10 cm, requiring a triplet quadrupole aperture of around 130 mm. The performance is further improved if the triplet is based on the Nb3Sn technology. In the present baseline, this beta* reduction provides a negligible luminosity increase: this approach requires a drastic action to minimize the crossing angle, while the beam separation at the long-range encounters has to be increased. This is provided by an early separation scheme made of small dipoles inside the detectors. Optionally, a small angle crab cavity scheme may totally suppress the residual crossing angle. The quadrupole aperture is calculated to allow a larger gap for the collimator, suppressing their impedance limitation. This concept offers high performance while significantly reducing the risks associated to a beam current increase; it opens as well new issues that deserve further studies, such as the dipole integration in the detector, and the correction of the triplet aberrations.
THPAN074	Space-Charge Compensation Options for the LHC Injector Complex	3390
	F. Zimmermann, M. Aiba, M. Chanel, U. Dorda, R. Garoby, J.-P. Koutchouk, M. Martini, E. Metral, Y. Papaphilippou, W. Scandale CERN, Geneva G. Franchetti GSI, Darmstadt V. D. Shiltsev Fermilab, Batavia, Illinois
	Space-charge effects have been identified as the most serious intensity limitation in the CERN PS and PS booster, on the way towards ultimate LHC performance and beyond. We here explore the application of several previously proposed space-compensation methods to the two LHC pre-injector rings, for each scheme discussing its potential benefit, ease of implementation, beam-dynamics risk, and the R&D programme required. The methods considered include tune shift and resonance compensation via octupoles, nonlinear chromaticity, or electron lenses, and beam neutralization by an electron cloud, plasma or negative ions.
THPAN075	Modeling Incoherent Electron Cloud Effects	3393
	F. Zimmermann, E. Benedetto, G. Rumolo, D. Schulte, R. Tomas CERN, Geneva W. Fischer BNL, Upton, Long Island, New York G. Franchetti GSI, Darmstadt K. Ohmi KEK, Ibaraki M. T.F. Pivi, T. O. Raubenheimer SLAC, Menlo Park, California K. G. Sonnad, J.-L. Vay LBNL, Berkeley, California
	Incoherent effects driven by an electron cloud could seriously limit the beam lifetime in proton storage rings or blow up the vertical emittance in positron ones. Different approaches to modeling these effects each have their own merits and drawbacks. We compare the simulation results and computing time requirements from a number of dedicated codes under development over the last years, and describe the respective approximations for the beam-electron cloud interaction, the accelerator structure, and the optical lattice, made in each of these codes. Examples considered include the LHC, CERN SPS, RHIC, and the ILC damping ring. Tentative conclusions are drawn and a strategy for further codes development is outlined.
THPAS091	BPM Calibration Independent LHC Optics Correction	3693
	R. Calaga BNL, Upton, Long Island, New York R. Tomas, F. Zimmermann CERN, Geneva
	Funding: This work is partially supported by the U. S. DOE The tight mechanical aperture for the LHC imposes severe constraints on both the beta and dispersion beating. Robust techniques to compensate these errors are critical for operation of high intensity beams in the LHC. We present simulations using realistic errors from magnet measurements and alignment tolerances in the presence of BPM noise. Correction reveals that the use of BPM calibration and model independent observables are key ingredients to accomplish optics correction. Experiments at RHIC to verify the algorithms for optics correction are also presented.
FRPMN078	Improved Algorithms to Determine Non-Linear Optics Model of the SPS from Non-Linear Chromaticity	4231
	R. Tomas, G. Arduini, G. Rumolo, F. Zimmermann CERN, Geneva R. Calaga BNL, Upton, Long Island, New York A. Faus-Golfe IFIC, Valencia
	Funding: This work is partially supported by the U. S. DOE In recent years several measurements of the SPS non-linear chromaticity have been performed in order to determine the non-linear optics model of the SPS machine at injection energy for different cycles. In 2006 additional measurements have been performed at injection and during the ramp for the cycle used to accelerate the LHC beam. New and more robust matching algorithms have been developed in 2006 to fit the model to the measurements up to arbitrary chromatic order. In this paper we describe the algorithms used in the analysis of the data and we summarize and compare the results from all experiments.
FRPMN079	Two-Beam Resistive-Wall Wake Field	4237
	F. Zimmermann CERN, Geneva
	In all storage-ring colliders, two beams propagating in opposite direction share a common beam pipe over parts or all of the ring circumference. The resistive-wall wake field coupling bunches of these two beams is different from the conventional single-beam wake field, as the magnetic force and the longitudinal electric force experienced by a probe bunch invert their sign, while the transverse electric force does not. In addition, the distance between driving and probing bunches is not constant, but the net wake field must be obtained via an integration of the force experienced over the drive-probe distance. We derive the two-beam resistive-wall wake field for a round beam pipe.