Zimmermann, F.

Paper	Title	Page
TUPP082	Longitudinal Stability of Flat Bunches with Space-charge or Inductive Impedance	1721
	F. Zimmermann CERN, Geneva I. Santiago Gonzalez University of the Basque Country, Bilbao
	We study the loss of Landau damping for the longitudinal plane via the ''Sacherer formalism''. Stability limits are calculated for several longitudinal beam distributions, in particular for two types of flat bunches, which could be of interest to the LHC upgrade. The resulting Landau stability diagrams are computed and displayed for different azimuthal modes. A general recipe is given for calculating the threshold intensity in the case of a capacitive impedance below transition or, equivalently, for a purely inductive impedance above transition. Specific results are finally presented for the case of the PS Booster, as an example of space-charge impedance below transition, and for the SPS, as an example of inductive impedance above transition.
WEPP007	Crab Compensation for LHC Beams	2536
	R. Calaga BNL, Upton, Long Island, New York Y. Sun, R. Tomas, F. Zimmermann CERN, Geneva
	An R&D program to establish a road map for the installation of crab cavities in the LHC is rapidly advancing. Both local and global crab schemes are under investigation to develop cavities that will be compatible with LHC optics and meet aperture requirements. The design of a prototype TM110 cavity and pertinent RF requirements including impedance estimates and damping are discussed. Some alternate cavity designs are also explored. The required optics modifications to accommodate the crab cavities and some particle stability studies are presented.
WEPP012	Analysis of Optical Layouts for the Phase 1 Upgrade of the CERN Large Hadron Collider Insertion Regions	2551
	M. Giovannozzi, F. Borgnolutti, O. S. Brüning, U. Dorda, S. D. Fartoukh, W. Herr, M. Meddahi, E. Todesco, R. Tomas, F. Zimmermann CERN, Geneva R. de Maria EPFL, Lausanne
	In the framework of the studies for the upgrade of the insertions of the CERN Large Hadron Collider, four optical layouts were proposed with the aim of reducing the beta-function at the collision point down to 25 cm. The different candidate layouts are presented. Results from the studies performed on mechanical and dynamic aperture are summarized, together with the evaluation of beam-beam effects. Particular emphasis is given to the comparison of the optics performance, which led to retain two promising layouts for further investigation and development.
WEPP154	Linac-LHC ep Collider Options	2847
	F. Zimmermann, F. Bordry, H.-H. Braun, O. S. Brüning, H. Burkhardt, R. Garoby, T. P.R. Linnecar, K. H. Mess, J. A. Osborne, L. Rinolfi, D. Schulte, R. Tomas, J. Tuckmantel, A. de Roeck CERN, Geneva H. Aksakal N. U, Nigde S. Chattopadhyay Cockcroft Institute, Warrington, Cheshire A. K. Ciftci Ankara University, Faculty of Sciences, Tandogan/Ankara J. B. Dainton Liverpool University, Science Faculty, Liverpool A. Eide EPFL, Lausanne B. J. Holzer DESY, Hamburg M. Klein University of Liverpool, Liverpool S. Sultansoy TOBB ETU, Ankara A. Vivoli LAL, Orsay F. J. Willeke BNL, Upton, New York
	We describe various parameter scenarios for a ring-linac ep collider based on LHC and an independent s.c. electron linac. Luminosities of order 1032/cm2/s can be achieved with a standard ILC-like linac, operated either in pulsed or cw mode, with acceptable beam power. Reaching much higher luminosities, up to 1034/cm2/s and beyond, would require the use of two linacs and the implementation of energy recovery. Advantages and challenges of a ring-linac ep collider vis-a-vis an alternative ring-ring collider are discussed.
THYM02	Incoherent Effects of Space Charge and Electron Cloud	2942
	G. Franchetti, I. Hofmann GSI, Darmstadt F. Zimmermann CERN, Geneva
	Trapping in, or scattering off, resonances driven by space charge or electron cloud in conjunction with synchrotron motion can explain numerous observations of slow beam loss and emittance growth, which are often accompanied by changes in the longitudinal beam profile. This talk will review recent progress in understanding and modelling the underlying mechanisms, highlight the differences and similarities between space charge and electron cloud, and discuss simulation results in the light of experimental observations, e.g., at GSI, CERN and BNL.
	Slides
MOPP003	Study of Abnormal Vertical Emittance Growth in ATF Extraction Line	553
	M. Alabau, A. Faus-Golfe IFIC (CSIC-UV), Valencia M. Alabau, P. Bambade, J. Brossard, G. Le Meur, C. Rimbault, F. Touze LAL, Orsay D. Angal-Kalinin, J. K. Jones STFC/DL/ASTeC, Daresbury, Warrington, Cheshire R. Appleby, A. Scarfe UMAN, Manchester S. Kuroda KEK, Ibaraki G. R. White, M. Woodley SLAC, Menlo Park, California F. Zimmermann CERN, Geneva
	Since several years, the vertical emittance measured in the Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK, that will transport the electron beam from the ATF Damping Ring (DR) to the future ATF2 Final Focus beam line, is significantly larger than the emittance measured in the DR itself, and there are indications that it grows rapidly with increasing beam intensity. This long-standing problem has motivated studies of possible sources of this anomalous emittance growth. One possible contribution is non-linear magnetic fields in the extraction region experienced by the beam while passing off-axis through magnets of the DR during the extraction process. In this paper, simulations of the emittance growth are presented and compared to observations. These simulations include the effects of predicted non-linear field errors in the shared DR magnets and orbit displacements from the reference orbit in the extraction region. Results of recent measurements using closed orbit bumps to probe the relation between the extraction trajectory and the anomalous emittance growth are also presented.
WEOAG01	Prospects for a Large Hadron Electron Collider (LHeC) at the LHC	1903
	M. Klein Liverpool University, Science Faculty, Liverpool H. Aksakal N. U, Nigde F. Bordry, H.-H. Braun, O. S. Brüning, H. Burkhardt, R. Garoby, J. M. Jowett, T. P.R. Linnecar, K. H. Mess, J. A. Osborne, L. Rinolfi, D. Schulte, R. Tomas, J. Tuckmantel, F. Zimmermann, A. de Roeck CERN, Geneva S. Chattopadhyay, J. B. Dainton Cockcroft Institute, Warrington, Cheshire A. K. Ciftci Ankara University, Faculty of Sciences, Tandogan/Ankara A. Eide EPFL, Lausanne B. J. Holzer DESY, Hamburg P. Newman Birmingham University, Birmingham E. Perez CEA, Gif-sur-Yvette S. Sultansoy TOBB ETU, Ankara A. Vivoli LAL, Orsay F. J. Willeke BNL, Upton, New York
	The LHeC collides a lepton beam with one of the intense, LHC, hadron beams. It achieves both e± interactions with quarks at the terascale, at eq masses in excess of 1 TeV, with a luminosity of about 1033 cm-2 s-1, and it also enables a sub-femtoscopic probe of hadronic matter at unprecedented chromodynamic energy density, at Bjorken-x values down to 10-6 in the deep inelastic scattering domain. The LHeC combines the LHC infrastructure with recent advances in radio-frequency, in linear acceleration and in other associated technologies, to enable two proposals for TeV ep collisions: a "ring-ring" option in which 7 TeV protons (and ions) collide with about 70 GeV electrons/positrons in a storage ring in the LHC tunnel and a "linac-ring" option based on an independent superconducting linear accelerator enabling single-pass collisions of electrons and positrons of up to about 140 GeV with an LHC hadron beam. Both options will be presented and compared. Steps are outlined for completing a Conceptual Design Review of the accelerator complex, beam delivery, luminosity, physics and implications for experiment, following declared support by ECFA and by CERN for a CDR.
	Slides
WEPP052	A Storage Ring Based Option for the LHeC	2638
	F. J. Willeke BNL, Upton, New York F. Bordry, H.-H. Braun, O. S. Brüning, H. Burkhardt, J. M. Jowett, T. P.R. Linnecar, K. H. Mess, S. Myers, J. A. Osborne, F. Zimmermann CERN, Geneva S. Chattopadhyay Cockcroft Institute, Warrington, Cheshire J. B. Dainton, M. Klein Liverpool University, Science Faculty, Liverpool B. J. Holzer DESY, Hamburg
	The LHeC aims at the generation of Hadron-Lepton collisions with center of mass energies in the TeV scale and luminosities of the order of 1033 cm-2 sec-1 by taking advantage of the existing LHC 7 TeV proton ring and adding a high energy electron accelerator. This paper presents technical considerations and potential parameter choices for such a machine and outlines some of the challenges arising when an electron storage ring based option, constructed within the existing infrastructure of the LHC, is chosen.
THPC073	Measurement of Resonance Driving Terms in the ATF Damping Ring	3155
	R. Tomas, F. Zimmermann CERN, Geneva K. Kubo, S. Kuroda, T. Naito, T. Okugi, J. Urakawa KEK, Ibaraki
	The measurement of resonance driving terms in the Damping Ring of the Accelerator Test Facility in KEK could help finding possible machine imperfections and even to optimize single particle stability through the minimization of non-linearities. The first experimental attempts of this enterprise are reported in this note.
THPC081	RF Wire Compensator of Long-range Beam-beam Effects	3173
	U. Dorda, F. Caspers, T. Kroyer, F. Zimmermann CERN, Geneva
	The dynamic aperture of the proton beam circulating in the Large Hadron Collider (LHC) is expected to be limited by up to 120 long-range beam-beam encounters. In order to perfectly compensate the LHC long-range beam-beam effect for nominal as well as for so-called 'PACMAN' bunches, i.e. bunches at the start or end of a bunch train, the wire compensator strength should be adjusted for each bunch individually. Here an RF-based compensator is proposed as a practical solution for the PACMAN compensation. We show that this approach also allows relaxing the power and precision requirements compared with those of a pulsed DC device, to a level within the state-of-the-art of RF technology. Furthermore it allows the use of a passive circulator in the tunnel close to the beam and thus a significantly reduction of the transmission line length and of the resulting multiple reflection issues. Simulations, issues related to RF phase noise and first experimental results from laboratory models as well as from a wire-compensator prototype installed in the CERN Super Proton Synchrotron (SPS) are presented.
THPC082	Wire Excitation Experiments in the CERN SPS	3176
	U. Dorda, J.-P. Koutchouk, R. Tomas, J. Wenninger, F. Zimmermann CERN, Geneva R. Calaga, W. Fischer BNL, Upton, Long Island, New York
	In order to study the effect of long range interaction and its wire compensation experimentally, current carrying wires are installed in the CERN Super Proton Synchrotron (SPS). In this paper we summarize the main results of the 2007 wire excitation results at 26, 37 and 55 GeV including wire-current-, beam-wire distance and chromaticity scans. A strong dependence on the chromaticity and indications of a threshold effect at 37 and 55 GeV was found. The results are compared to simulation, to a simple analytic scaling law and to experimental results from RHIC. Wire-driven resonances have been observed through the Fourier spectrum of experimental BPM data and compared to simulations.
THPC089	Electron-cloud Intrabunch Density Modulation	3197
	G. Franchetti GSI, Darmstadt F. Zimmermann CERN, Geneva
	During the passage of a proton bunch through an electron cloud a complicated electron density modulation arises, with characteristic ring and stripe patterns of high density regions that move radially outward along the bunch. We present simulation results as well as a simple analytical model to reveal the morphology and main features of this phenomenon as well as its dependence on key parameters like bunch length, beam size, and bunch charge.