Zimmermann, F.

Paper	Title	Page
MOPLT024	Flexibility, Tolerances, and Beam-Based Tuning of the CLIC Damping Ring	590
	M. Korostelev, J. Wenninger, F. Zimmermann CERN, Geneva
	The present design of the CLIC damping ring can easily accommodate anticipated CLIC parameter changes. Realistic misalignments of magnets and monitors increase the equilibrium emittance. In simulations we study both the sensitivity to magnet displacements and the emittance recovery achieved by orbit correction, dispersion-free steering and coupling compensation.
MOPLT039	QCD Explorer Based on LHC and CLIC-1	632
	F. Zimmermann, D. Schulte CERN, Geneva
	Colliding 7-TeV LHC super-bunches with 75-GeV CLIC bunch trains can provide electron-proton collisions at very high centre-of-mass energies, opening up a new window into QCD. At the same time, this QCD explorer would employ several key components required for both an LHC upgrade and CLIC. We here present a possible parameter set of such a machine, study the consequences of the collision for both beams, and estimate the attainable luminosity.
TUZBCH02	Beam Dynamics Challenges for Future Circular Colliders	83
	F. Zimmermann CERN, Geneva
	The luminosity of circular colliders rises with the beam intensity, until some limit is encountered, mostly due to head-on and long-range beam-beam interaction, due to electron cloud, or due to conventional impedance sources. These limitations can be alleviated, if not overcome, by a proper choice of beam parameters and by dedicated compensation schemes. Examples include the alternating crossing at several interaction points, electromagnetic wires, super-bunches, electron lenses, clearing electrodes, and nonlinear collimation. I illustrate the benefit from such mitigating measures for the Tevatron, the LHC, the LHC Upgrade, the VLHC, the super e+e- factories, or other projects, and I describe related research efforts at FNAL, KEK, BNL and CERN.
	Video of talk
	Transparencies
TUPLT012	Adjusting the IP Beta-functions in RHIC.	1156
	W. Wittmer, F. Zimmermann CERN, Geneva F.C. Pilat, V. Ptitsyn, J. Van Zeijts BNL, Upton, Long Island, New York
	The beta- functions at the IP can be adjusted without perturbation of other optics functions via several approaches. In this paper we describe a scheme based on a vector knob, which assigns fixed values to the different tuning quadrupoles and scales them by a common multiplier. The values for the knob vector were calculated for a lattice without any errors using MADX. Previous studies for the LHC have shown that this approach can meet the design goals. A specific feature of the RHIC lattice is the nested power supply system. To cope with the resulting problems a detailed response matrix analysis has been carried out and different sets of knobs were calculated and compared. The knobs are tested at RHIC during the 2004 run and preliminary results maybe discussed. Simultaneously a new approach to measure the beam sizes of both colliding beams at the IP, based on the tune ability provided by the knobs, was developed and tested.
TUPLT013	Calculating LHC Tuning Knobs using Various Methods	1159
	W. Wittmer, D. Schulte, F. Zimmermann CERN, Geneva
	By measuring and adjusting the beta-functions at the IP the luminosity is being optimized. In LEP this was done with the two closest doublet magnets. This approach is not applicable for the LHC due to the asymmetric lattice and common beam pipe through the triplet magnets. To control and change the beta-functions quadrupole groups situated on both sides further away from the IP have to be used where the two beams are already separated. The quadrupoles are excited in specific linear combinations, forming the so-called tuning knobs for the IP beta-functions. We compare the performance of such knobs calculated by different methods: (1) matching in MAD, (2) inversion of the re-sponse matrix and singular value decomposition inversion and conditioning and (3) conditioning the response matrix by multidimensional minimization using Hessian method.
WEPLT008	Simulated Emittance Growth due to Electron Cloud for SPS and LHC	1831
	E. Benedetto, D. Schulte, F. Zimmermann CERN, Geneva G. Rumolo GSI, Darmstadt
	The emittance growth caused by an electron cloud is simulated by the HEADTAIL code. The simulation result depends on the number of beam-cloud "interaction points"(IPs), the phase advance between the IPs, the number of macro-particles used to represent beam and cloud, and on the betatron tune. Simulations include a transverse feedback system and, optionally, a large chromaticity, as employed in actual SPS operation. Simulation results for the SPS are compared with observations, and the emittance growth in the LHC is computed as a function of the average electron density.
WEPLT009	Dynamics of the Electron Pinch and Incoherent Tune Shift Induced by Electron Cloud	1834
	E. Benedetto, F. Zimmermann CERN, Geneva
	When a proton bunch passes through an electron cloud, the cloud electrons are attracted by the beam electric field; their density strongly increases near the beam centre. This gives rise to an incoherent proton tune shift, which depends on the longitudinal and radial position within the bunch. We present an analytical description of the 'electron pinch' and the resulting proton tune shift, for a circular symmetry and a Gaussian cloud. Benchmarking and extending the results by computer simulations, we explore the effects of different longitudinal beam profiles and of the nonlinear transverse force.
WEPLT044	Electron-cloud Build-up Simulations and Experiments at CERN	1930
	F. Zimmermann, G. Arduini, V. Baglin, T. Bohl, B.J. Jenninger, J.M. Jimenez, J.-M. Laurent, F. Ruggiero, D. Schulte CERN, Geneva
	We compare the predications of electron-cloud build-up simulations with measurements at the CERN SPS. Specifically, we compare the electron flux at the wall, electron-energy spectra, heat loads, and the spatial distribution of the electrons for two different bunch spacings, with variable magnetic fields, and for several chamber temperatures and associated surface conditions. The simulations employ a modified, improved version of the ECLOUD code. The main changes are briefly described. We finally present updated simulation results for the heat load in the cold LHC arcs.
WEPLT045	Experiments on LHC Long-range Beam-beam Compensation in the CERN SPS	1933
	F. Zimmermann, J.-P. Koutchouk, J. Wenninger CERN, Geneva
	Long-range beam-beam collisions may limit the dynamic aperture and the beam lifetime in storage-ring colliders. Their effect can be compensated by a current-carrying wire mounted parallel to the beam. A compensation scheme based on this principle has been proposed for the Large Hadron Collider (LHC). To demonstrate its viability, a prototype wire was installed at the CERN SPS in 2002. First successful machine experiments explored the dependence of beam loss, beam size, and beam lifetime on the beam-wire distance and on the wire excitation. They appear to confirm the predicted effect of the long-range collisions on the beam dynamics. In 2004, two further wires will become available, by which we can explicitly demonstrate the compensation, study pertinent tolerances, and also compare the respective merits of different beam-beam crossing schemes for several interaction points.
WEPLT046	Localizing Impedance Sources from Betatron-phase Beating in the CERN SPS	1936
	F. Zimmermann, G. Arduini, C. Carli CERN, Geneva
	Multi-turn beam-position data recorded after beam excitation can be used to extract the betatron-phase advance between adjacent beam position monitors (BPMs) by a harmonic analysis. Performing this treatment for different beam intensities yields the change in phase advance with current. A local impedance contributes to the average tune shift with current, but, more importantly, it also causes a mismatch and phase beating. We describe an attempt to determine the localized impedance around the SPS ring by fitting the measured betatron phase shift with current at all BPMs to the expected impedance response matrix.
WEPLT054	Electron Cloud Build up in Coasting Beams	1960
	G. Rumolo GSI, Darmstadt G. Bellodi CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon K. Ohmi KEK, Ibaraki F. Zimmermann CERN, Geneva
	Electrons could in principle accumulate in the potential of coasting beams of positively charged particles until a balance between the beam force and space charge force from the electrons is reached. But the continuous interaction between a non-ideal perturbed coasting beam and the cloud of electrons being trapped by it, together with the reflection and secondary emission processes at the inner pipe wall, can alter this picture and cause a combined cloud or beam transverse instability long before the concentration of electrons reaches the theoretical equilibrium value. The issue is addressed in this paper by means of combined build-up and instability simulations carried out with the HEADTAIL code.
WEPLT069	Investigation of Scraper Induced Wake Fields at ANKA	2005
	A.-S. Müller, I. Birkel, E. Huttel, M. Pont, F. Pérez FZK-ISS-ANKA, Karlsruhe F. Zimmermann CERN, Geneva
	The ANKA synchrotron light source operates in the energy range from 0.5 to 2.5 GeV. Typical requirements for light sources include small beam sizes, large lifetimes and high currents to provide the highest possible photon flux. The understanding of impedance and instability related issues is very important in order to improve the machine performance, in particular when small aperture insertion devices are installed that require protection by a scraper. In the framework of an impedance survey the transverse and longitudinal wake fields induced by a vertical scraper have been measured and analysed. This paper reports the beam observations and compares them with the expectation.
WEPLT070	Studies of Current Dependent Effects at ANKA	2008
	A.-S. Müller, I. Birkel, E. Huttel, M. Pont, F. Pérez FZK-ISS-ANKA, Karlsruhe F. Zimmermann CERN, Geneva
	The ANKA electron storage ring is operated at energies between 0.5 and 2.5 GeV. A major requirement for a synchrotron light source, such as ANKA, is to achieve a high beam current. A multitude of mostly impedance related effects depend on either bunch or total beam current. This paper gives an overview over the various beam studies performed at ANKA in this context, specifically the observation of current dependent detuning, the dermination of the bunch length change with current from a measurement of the ratio between coherent and incoherent synchrotron tune and an assessment of the effective longitudinal loss factor from the current dependent horizontal closed orbit distortion.
THPLT017	Review and Comparison of Simulation Codes Modeling Electron-Cloud Build Up and Instabilities	2499
	F. Zimmermann, E. Benedetto, F. Ruggiero, D. Schulte CERN, Geneva G. Bellodi CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon M. Blaskiewicz, L. Wang BNL, Upton, Long Island, New York Y. Cai, M.T.F. Pivi SLAC, Menlo Park, California V.K. Decyk, W. Mori UCLA, Los Angeles, California M.A. Furman LBNL/AFR, Berkeley, California A.F. Ghalam, T. Katsouleas USC, Los Angeles, California K. Ohmi, S.S. Win KEK, Ibaraki G. Rumolo GSI, Darmstadt
	Several computer codes written at various laboratories are employed for modelling the generation and the consequences of an electron cloud. We review the most popular of these programs, which simulate either the build of an electron cloud or the instabilities it produces, and we compare simulation results for identical, or similar, input parameters obtained from the various codes.
MOPLT067	KEKB Performance	707
	Y. Funakoshi, K. Akai, K. Ebihara, K. Egawa, A. Enomoto, J. Flanagan, H. Fukuma, K.  Furukawa, T. Furuya, J. Haba, S. Hiramatsu, T. Ieiri, N. Iida, H. Ikeda, T. Kageyama, S. Kamada, T. Kamitani, S. Kato, M. Kikuchi, E. Kikutani, H. Koiso, M. Masuzawa, T. Mimashi, A. Morita, T. Nakamura, H. Nakayama, Y. Ogawa, K. Ohmi, Y. Ohnishi, N. Ohuchi, K. Oide, M. Shimada, S. Stanic, M. Suetake, Y. Suetsugu, T. Sugimura, T. Suwada, M. Tawada, M. Tejima, M. Tobiyama, S. Uehara, S. Uno, S.S. Win, N. Yamamoto, Y. Yamamoto, Y. Yano, K. Yokoyama, M. Yoshida, M. Yoshida, S.I. Yoshimoto KEK, Ibaraki F. Zimmermann CERN, Geneva
	The KEKB B-Factory is an electron-positron double ring collider working at KEK. Its peak luminosity surpassed 1034 /cm2/sec in May 2003 for the first time in the history of colliders. In this report, we summarize the history of KEKB with an emphasis of recent progress.