EPAC 2006 - Classification:05 Beam Dynamics and Electromagnetic Fields/D02 Non-linear Dynamics

05 Beam Dynamics and Electromagnetic Fields

D02 Non-linear Dynamics - Resonances, Tracking, Higher Order

Paper	Title	Page
WEXFI03	Non-linear Collimation in Linear and Circular Colliders	1892
	A. Faus-Golfe IFIC, Valencia J. Resta-López, F. Zimmermann CERN, Geneva
	We describe the concept on nonlinear collimation of beam halo in linear and circular colliders. In particular we present the application of such a concept in two different cases: the energy collimation system for CLIC at 3 TeV c.m. energy and a betatron collimation system for LHC at 14 TeV c.m. energy. For each case, the system properties, like chromatic bandwidth, collimator survival and cleaning efficiency, are evaluated and compared with those of the corresponding linear collimation system.
	Transparencies
WEOFI01	Beam Dynamics Measurements in the Vicinity of a Half-integer Resonance	1902
	T. Ieiri, J.W. Flanagan, H. Fukuma, H. Ikeda, Y. Ohnishi, K. Oide, M. Tobiyama KEK, Ibaraki
	The operating point of the betatron tune set near a half-integer is a crucial parameter to make high luminosity in electron/positron ring colliders. Dynamic beam-beam effects would change the optics parameters of the colliders, depending on the betatron tune and the beam-beam parameter. On the other hand, existence of the half-integer stopband makes the beam unstable. Therefore, beam behavior near a half-integer might provide interesting issues from the viewpoint of beam dynamics. We measured a frequency response of the beam across a half-integer for measuring the betatron tune at KEKB. A sharp spike just at a half-integer was observed in the tune spectrum. We believe that the spectrum would be a nonlinear resonance caused by some off-momentum particles in a bunch, not by a coherent motion of a whole bunch. The horizontal beam size measured using a synchrotron radiation monitor indicated a slight increase when the tune approached a half-integer. The variations in the beam size are discussed, considering both dynamic beam-beam effects and a beta beat due to the half-integer stopband.
	Transparencies
WEOFI02	RF Phase Modulation Studies at the LNLS Electron Storage Ring	1905
	N.P. Abreu, R.H.A. Farias, P.F. Tavares LNLS, Campinas
	In this work we present a set of measurements of the effectiveness of RF phase modulation on the second harmonic of the RF frequency as a mechanism to damp longitudinal coupled-bunch instabilities. We also propose a theoretical model of the damping mechanism, in which the increase of the spread in synchrotron frequencies inside the bunches produced by phase modulation is responsible for damping the centroid dipolar coherent motion caused by an external excitation, which could be a Higher Order Mode (HOM) of the RF cavities driving the coupled bunch motion. We measured the coherent synchrotron oscillation damping of a single bunch under two circumstances, with and without phase modulation, and determined the amount of extra damping due to the modulation. With this experiment we could also measure the frequency of small oscillations around the stable islands formed by phase modulation and its behavior when the RF phase modulation amplitude and frequency are changed. We performed measurements of Beam Transfer Function (BTF) to observe the effects of phase modulation over the stable area for coherent oscillations and compared the results with a theoretical model.
	Transparencies
WEPCH067	Implementation of TPSA in the Mathematica Code LieMath	2077
	D. Kaltchev TRIUMF, Vancouver
	The Lie Algebra package LieMath written in the Mathematica language constructs the beamline map in a single-exponent Lie generator form. The algorithm (BCH-based map concatenation) has been recently enhanced with Truncated Power Series Algebra (TPSA) techniques.The polynomials produced by the series expansion of the Hamiltonian are replaced with arrays of coefficients (derivative structures) and the Poisson bracket and BCH are defined as operations on such structures. We have confirmed the statement that using automatic differentiation instead of symbolic operations increases the speed by least an order of magnitude. The code is equipped with a MAD parser and a normal form block allowing it to extract nonlinear chromaticity and amplitude detuning. The notebook was applied in FFAG studies and may be useful for the linear collider final focus or collimation systems.
WEPCH068	6-D Beam Dynamics Studies in EMMA FFAG	2080
	F. Meot CEA, Gif-sur-Yvette
	Extensive simulations of 6-D transmission simulations in linear, non-scaling FFAGs, based on gutter rapid acceleration, are reported. They concern two different on-going projects: the 20~GeV muon accelerators in the Neutrino Factory (NuFact) with ISS parameters* and a 20~MeV electron model of these machines, EMMA*. http://www.hep.ph.ic.ac.uk/iss/**http://hepunx.rl.ac.uk/uknf/wp1/emodel/
WEPCH072	The High Order Non-linear Beam Dynamics in High Energy Storage Ring of FAIR	2083
	A.N. Chechenin, R. Maier, Y. Senichev, E. Senicheva FZJ, Jülich
	The High Energy Storage Ring (HESR) is part of the international project FAIR for antiproton physics with beam in the momentum range from 1.5 to 15 GeV/c to explore the research areas of hadron structure and quark-gluon dynamics. An important feature of the project is the combination of phase space cooled beams with thick internal targets. Therefore there are two obvious reasons of beam heating: the target-beam interaction and the intra-beam scattering. Another source of the beam size growth is the higher order resonances. In the paper we investigate the non-linear beam dynamics together with different correction schemes minimizing this effect and compare with other sources of beam heating. Since the tune working point has a spread dependent on the chromaticity correction scheme and space charge, we include in our consideration both effects as well. All beam dynamics calculations are carried out with the SIMBAD code from the Unified Accelerator Library (UAL). We use 10000 macro particles, grid sizes 64x64 and 1000 turns per run.
WEPCH073	Asymptotic Analysis of Ultra-relativistic Charge	2086
	D.A. Burton, J. Gratus, R. Tucker Lancaster University, Lancaster
	A new approach is developed for analysing the dynamic behaviour of distributions of charged particles in an electromagnetic field. Noting the limitations inherent in the Lorentz-Dirac equation for a single point particle, a simple model is proposed for a charged continuum interacting self-consistently with the Maxwell field in vacuo. The model is developed using intrinsic tensor field theory and exploits to the full the symmetry and light-cone structure of Minkowski spacetime. This permits the construction of a regular stress-energy tensor whose vanishing divergence determines a system of non-linear partial differential equations for the velocity and self-fields of accelerated charge. Within this covariant framework a particular perturbation scheme is motivated by an exact class of solutions to this system describing the evolution of a charged fluid under the combined effects of both self and external electromagnetic fields. The scheme yields an asymptotic approximation in terms of inhomogeneous linear equations for the self-consistent Maxwell field, charge current and time-like velocity field of the charged fluid and is defined as an ultra-relativistic configuration.
WEPCH074	Progress with Non-linear Beam Dynamic Studies of the Diamond Storage Ring	2089
	R. Bartolini, I.P.S. Martin, B. Singh Diamond, Oxfordshire J.K. Jones CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
	The conflicting requirements of high-brightness photon beams combined with adequate beam lifetime and high injection efficiency mean careful control of the non-linear lattice is crucial to achieving optimum performance. As part of the optimisation of the Diamond storage ring, studies have been made of both the Touschek lifetime and storage ring injection process, with the help of on-momentum and off-momentum frequency maps. The effect of chromaticity on Touschek lifetime has also been investigated and several new sextupole settings were identified achieving good Touschek lifetime and injection efficiency.
WEPCH075	Effect of Insertion Devices on Beam Dynamics of the Diamond Storage Ring Using Kick Maps	2092
	B. Singh, A.I. Baldwin, R. Bartolini, I.P.S. Martin Diamond, Oxfordshire
	The effect of the all Phase-I Insertion Devices (IDs) on the beam dynamic of the Diamond storage ring has been investigated using the kick map modelisation of the IDs. Kick maps have been produced with high accuracy using the computer code RADIA, considering many longitudinal harmonics. The effect of IDs on the dynamic aperture, Touschek lifetime and injection efficiency in the low emittance lattice, was investigated considering both coupling errors and physical engineering apertures. Harmful resonances have been identified using Frequency Map Analysis (FMA) and full 6D tracking was performed to estimate the Touschek lifetime and the injection efficiency. Additionally, the kick maps have been used to generate feed-forward tables for compensation of linear optics distortion.
WEPCH076	Renormalization Group Reduction of the Frobenius-Perron Operator	2095
	S.I. Tzenov Universita' degli Studi di Salerno, Dipartimento di Fisica E.R. Caianiello, Baronissi
	The Renormalization Group (RG) method is adopted as a tool for a constructive analysis of the properties of the Frobenius-Perron Operator. The renormalization group reduction of a generic symplectic map in the case, where the unperturbed rotation frequency of the map is far from structural resonances driven by the kick perturbation has been performed in detail. It is further shown that if the unperturbed rotation frequency is close to a resonance, the reduced RG map of the Frobenius-Perron operator (or phase-space density propagator) is equivalent to a discrete Fokker-Planck equation for the renormalized distribution function. The RG method has been also applied to study the stochastic properties of the standard Chirikov-Taylor map.
WEPCH077	Particle Tracking in a Sextupole Field using the Euler Method Approximation	2098
	S. Di Mitri, E. Karantzoulis ELETTRA, Basovizza, Trieste
	The purpose of this paper is to evaluate any differences in the single particle tracking through a magnetic lattice when sextupoles are treated either like sliced or single-kick elements. Only on-energy transverse motion is considered. Convergence and symplecticity of the method of sliced sextupoles are discussed. Dynamic apertures and transverse phase spaces applied to the Elettra synchrotron lattice are compared for the two cases.
WEPCH078	Measurement of Wake Effects by Means of Tune Shift in the KEKB Low-Energy Ring	2101
	T. Ieiri, H. Fukuma, Y. Ohnishi, M. Tobiyama KEK, Ibaraki
	The electron cloud produced by the positron beam induces single-bunch and coupled-bunch wakes, in addition to a tune shift. Effects of the dipole wake-field including the electron cloud were tried to measure in the KEKB Low Energy Ring. A test bunch was placed behind a bunch-train of the positron beam, even though a test bunch itself might interact with the remaining electron cloud. We measured a current-dependent tune-shift of a test bunch under constant train-current, while changing the bucket position of a test bunch. The tune shift indicated a strong defocusing field, however, tended to a focusing field when a test bunch approached a train with high train-current. The results are discussed, considering variations of the electron cloud density.
WEPCH079	Effects of Intrinsic Nonlinear Fields in the J-PARC RCS	2104
	H. Hotchi, Y. Irie, F. Noda JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken S. Machida CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon A.Y. Molodozhentsev KEK, Ibaraki
	In order to accelerate a high intense proton beam with small particle losses, the J-PARC RCS, which is being constructed at JAEA, has a large acceptance. In such synchrotrons, the nonlinear motion of the beam particles, especially moving away from the axis of the elements, is a common issue, and it becomes essential to consider intrinsic field nonlinearities. The main sources of nonlinear magnetic fields in the RCS are as follows: fringes of the main dipole and quadrupole magnets, sextupole fields used for the chromatic correction, leak fields from the injection and extraction beam lines, etc. In this paper, we will discuss influences of the intrinsic field nonlinearities and a cure for the induced betatron resonances, based on single-particle and multi-particle tracking simulations.
WEPCH080	Beam Simulation of SQQ Injection System in KIRAMS-30 Cyclotron	2107
	D.H. An, J.-S. Chai, H.B. Hong, S.S. Hong, M.G. Hur, W.T. Hwang, H.S. Jang, I.S. Jung, J. Kang, J.H. Kim, Y.S. Kim, M.Y. Lee, T.K. Yang KIRAMS, Seoul
	The injection system of KIRAMS-30 cyclotron consists of a double gap buncher, an SQQ, and a spiral inflector. Initial beam with 100 mmmrad has been generated by random Gaussian function in the transverse plane and random uniform function in the longitudinal direction. Using the 3D electric and magnetic fields of a buncher, SQQ, inflector, and return-yoke bore, the characteristics of the beam injected into the KIRAMS-30 cyclotron's central region has been obtained. This paper presents the results of its beam characteristics and parameters of each beam element.
WEPCH081	Injection of The Proton Beam Into The Compact Cyclotron with Solenoid	2110
	L.M. Onischenko, E. Samsonov JINR, Dubna, Moscow Region
	The proton (H-) low (100 mkA) intensity beam injected by means of the solenoid comes to the first cyclotron orbit without the beam emittance deterioration. This is demonstrated by computer simulation.
WEPCH082	Simulation of Ions Acceleration and Extraction in Cyclotron C400	2113
	Y. Jongen, W.J.G.M. Kleeven IBA, Louvain-la-Neuve G.A. Karamysheva, S.A. Kostromin, N.A. Morozov, E. Samsonov JINR, Dubna, Moscow Region
	The Belgian company IBA, together with scientists of the JINR in Dubna is designing a superconducting isochronous cyclotron for therapy by Carbon beams. The new cyclotron C400 has to deliver carbon ions with energy 400 MeV/amu and protons with energy close to 250 MeV. The cyclotron has a compact type superconducting magnet, with a pole radius of 187 cm. The axial focusing is provided by four sectors, with a spiral angle increasing to a maximum value close to 70° at maximum energy. With this design, an axial betatron frequency is maintained during most of the acceleration. The beam acceleration is provided by two spiral dees located in opposite valleys. The dee voltage increases from 100 kV at the center to 200 kV at extraction. The paper presents the analysis of the beam acceleration in the proposed new cyclotron. During the acceleration, several resonance lines are crossed, but the paper demonstrates that this resonance crossing is done without damaging the beam properties. Extraction of the Carbon ions is done by an electrostatic deflector, followed by magnetic correctors. Protons are extracted at lower energy by stripping 2H⁺1 ions.
WEPCH085	Algorithms for Chromatic Sextupole Optimization and Dynamic Aperture Increase	2116
	E. Levichev, P.A. Piminov BINP SB RAS, Novosibirsk
	Strong chromatic sextupoles compensating natural chromaticity of a storage ring may reduce dynamic aperture drastically. In the case of several sextupole families, one can find a lot of ways to correct chromaticity, which provides different sizes of the dynamic aperture. Finding a solution that gives the largest dynamic aperture is an important task for the storage ring design and operation. The paper discusses several approaches to sextupole arrangement optimization in order to obtain a large dynamic aperture.
WEPCH086	Adiabatic Theory of Slow Extraction of Particles from a Synchrotron	2119
	S.A. Nikitin BINP SB RAS, Novosibirsk
	An analytical approach is developed to describe the process of slow extraction of particles from a synchrotron based on adiabatic crossing of the betatron resonance of the third order. An exact expression for the phase integral is found to analyze the conditions of oscillation amplitude growth near the resonance band. It allows one to directly define the interval of adiabatic motion from the start of decreasing the resonant tune to the beginning of fast increase of the oscillation amplitude. The interval distribution function is constructed for the cases of zero momentum spread and zero machine chromaticity as well as for the general case, taking into account non-zero momentum spread, non-zero chromaticity and synchrotron oscillations. Some numeric calculations of the time dependence of the extracted particle current are presented. It is shown that the momentum spread in the extracted beam can be minimized with the use of additional RF acceleration of particles during the slow extraction procedure.
WEPCH087	Normal Form for Beam Physics in Matrix Representation	2122
	S.N. Andrianov St. Petersburg State University, Applied Mathematics & Control Processes Faculty, St. Petersburg A.N. Chechenin FZJ, Jülich
	The modeling of long beam evolution dynamics in nonlinear accelerator structures has raised new interest in the effective methods of nonlinear effects calculation. Moreover, it is preferably to use both analytical tools and numerical methods for evolution modeling. Usually the standard numerical methods and computer codes are based on the concept of symplectic transfer maps, whereas the analytical tool is the theory of normal forms. The method of normal forms can be realized in symbolic and numerical modes easily enough. In this paper, we discuss the normal form theory based on the matrix formalism for Lie algebraic tools. This approach allows using well known methods of matrix algebra. This permits to compute necessary matrices step-by-step up to desired order of approximation. This procedure leads to more simple structure of matrix representation for very complicated structure of this map does not allow using this map for practical computing. Therefore, it is necessary to transform this map in more appropriate form. In another words the new matrix representation for the map is particularly simple and has explicit invariants and symmetries.
WEPCH088	High Order Aberration Correction	2125
	S.N. Andrianov St. Petersburg State University, Applied Mathematics & Control Processes Faculty, St. Petersburg A.N. Chechenin FZJ, Jülich
	It is known that modern accelerators fall under nonlinear aberrations influence. The most of these aberrations have harmful character, and their effect must be maximally decreased. There are a set of approaches and codes to solving this problem. In this paper, we consider an approach for solving this problem using the matrix formalism for Lie algebraic tools. This formalism allows reducing the starting problem to linear algebraic equations for aberration coefficients, which are elements of corresponding matrices. There are discussed results evaluated using suggested approach and nonlinear programming tools. Some examples of corresponding results are given.
WEPCH092	Dynamical Aperture Studies for the CERN LHC: Comparison between Statistical Assignment of Magnetic Field Errors and Actual Measured Field Errors	2128
	M. Giovannozzi, S.D. Fartoukh, S.S. Gilardoni, J.-B. Jeanneret, A.M. Lombardi, Y. Papaphilippou, T. Risselada, R. de Maria CERN, Geneva
	It is customary to evaluate the performance of a circular particle accelerator by computing the dynamical aperture, i.e., the domain in phase space where bounded single-particle motion occurs. In the case of the LHC the dynamical aperture computation is performed by assuming a statistical distribution of the magnetic field errors of various magnets' classes: the numerical computations are repeated for a given set of realisations of the LHC ring. With the progress in the magnet production and allocation of the available positions in the ring, the statistical approach has to be replaced by the computation of one single configuration, namely the actual realisation of the machine. Comparisons between the two approaches are presented and discussed in details.
WEPCH093	Parameter Scans and Accuracy Estimates of the Dynamic Aperture of the CERN LHC	2131
	M. Giovannozzi, E. McIntosh CERN, Geneva
	Techniques to make use of large distributed computing facilities allow for denser parameter scans of the dynamical aperture, i.e., the domain in phase space where bounded single-particle motion prevails. Moreover, one can also increase the number of 'seeds' each of which represents a possible realisation of multipolar components around the machine. In this paper the dependence of the dynamical aperture on the step size of the grid of initial conditions and on the number of seeds is studied. Estimates on the accuracy of the dynamic aperture are derived and the definition of an improved protocol for numerical simulations is presented.
WEPCH094	An Early Beam Separation Scheme for the LHC	2134
	J.-P. Koutchouk, G. Sterbini CERN, Geneva
	The high nominal luminosity of the LHC requires a large number of bunches spaced by about 7.5 m. To prevent more than one head-on collision in each interaction region, a crossing angle of 0.285 mrad is necessary. A side effect of this crossing angle is the increase of the effective transverse beam cross-section, thereby decreasing the luminosity by some 16%. For the LHC upgrade, depending on the focusing scenarios, this loss significantly increases and largely offsets the potential gain of a stronger focusing. In this paper we analyze a strategy to circumvent this difficulty, based an early beam separation using small dipoles placed at a few meters from the interaction point, deep inside the detectors. This allows quasi co-linear head-on collisions at the crossing point only. From the beam dynamics point of view, the essential constraint is to control the long-range beam-beam interactions in a scenario where the normalized beam separation is not constant. In this paper the criteria of the analysis and the performance improvement obtained with the scheme are discussed. The strength of the dipoles is estimated as well as the impact on the detectors structure.
WEPCH095	Models to Study Multi-bunch Coupling through Head-on and Long-range Beam-beam Interactions	2137
	T. Pieloni, W. Herr CERN, Geneva
	In the LHC almost 6000 bunches will collide in four interaction points where they experience head-on as well as clustered long range interactions. These lead to a coupling between all bunches and coherent beam-beam effects. For two colliding bunches this is well understood. However, for a large number of bunches colliding with different collision patterns, it results in a complex spectrum of oscillation frequencies with consequences for beam measurements and Landau damping. To study the coherent beam-beam modes, three complementary models have been developped and will be described in this report. Two of these methods rely on self-consistent multi-bunch and multi-particle tracking while the third is a semi-analytic model based on a complex matrix algorithm. The three methods together provide useful information about the beam-beam coupling of multi bunch beams and together provide a deeper insight into the underlying physics.
WEPCH096	Measurement and Correction of the 3rd Order Resonance in the Tevatron	2140
	F. Schmidt CERN, Geneva Y. Alexahin, V.A. Lebedev, D. Still, A. Valishev Fermilab, Batavia, Illinois
	At Fermilab Tevatron BPM system has been recently upgraded resulting much better accuracy of beam position measurements and improvements of data acquisition for turn-by-turn measurements. That allows one to record the beam position at each turn for 8000 turns for all BPMs (118 in each plane) with accuracy of about 10^-20 μm. In the last decade a harmonic analysis tool has been developed at CERN that allows relating each FFT line derived from the BPM data with a particular non-linear resonance in the machine. In fact, one can even detect the longitudinal position of the sources of these resonances. Experiments have been performed at the Tevatron in which beams have been kicked to various amplitudes to analyze the 3rd order resonance. It was possible to address this rather large resonance to some purposely powered sextupoles. An alternative sextupole scheme allowed the suppression of this resonance by a good factor of 2. Lastly, the experimental data are compared with model calculations.
WEPCH097	Beam Dynamics in Compton-ring Gamma Sources	2143
	E.V. Bulyak, P. Gladkikh, V. Skomorokhov NSC/KIPT, Kharkov K. Moenig DESY Zeuthen, Zeuthen T. Omori, J. Urakawa KEK, Ibaraki F. Zimmermann CERN, Geneva
	Electron storage rings with a laser cavity are promising intensive sources of polarized hard photons to generate polarized positron beams. The dynamics of electron bunches circulating in a storage ring and interacting with high-power laser pulses is studied both analytically and by simulation. Common features and difference in the bunch behavior interacting with an extremely high power laser pulse (polarized positron source for the ILC project) and a moderate pulse (source for CLIC) are shown. Also considerations on particular lattice designs for both rings are presented.
WEPCH100	Application of the Lie-transform Perturbation Theory for the Turn-by-turn Data Analysis	2146
	Y. Alexahin Fermilab, Batavia, Illinois
	Harmonic analysis of turn-by-turn BPM data is a rich source of information on linear and nonlinear optics in circular machines. In the present report the normal form approach first introduced by R. Bartolini and F. Schmidt is extended on the basis of the Lie-transform perturbation theory to provide direct relation between the sources of perturbation and observable spectra of betatron oscillations. The goal is to localize strong perturbing elements, find the resonance driving terms - both absolute value and phase - that are necessary for calculation of the required adjustments in correction magnet circuits: e.g. skew-quadrupoles for linear coupling correction. The theory is nonlinear and permits to analyze higher order effects, such as coupling contribution to beta-beating and nonlinear sum resonances.
WEPCH101	Ion Motion in the Adiabatic Focuser	2149
	A. Sessler, E. Henestroza, S. Yu LBNL, Berkeley, California
	The Adiabatic Focuser* works by having a focusing channel whose strength increases with distance down the channel. In this situation electrons of various energies and various transverse oscillation phase all are transversely focused. The concept works with external focusing, but would be very effective in a plasma ion focusing channel where the density of ions is simply increased as one goes down the channel. In the original work (Ref 1) motion of the ions was not included (as it was assumed to be a small effect). Recently, it has been suggested that ion motion in an adiabatic focuser would be significant and, even, preclude operation of the focuser as previously envisioned*. In this paper we numerically study the ion motion in the focuser. The ions clearly influence each other and, most importantly, are influenced by the electric field of the electrons being focused. It is shown that parameters can be selected such that the adiabatic focuser works as well as originally envisioned. P. Chen et al. Phys. Rev. Lett. 64, 1231 (1990).**J. R. Rosenzweig, et al. Phys. Rev. Lett. 95, 195002 (2005).
WEPCH102	Studies of the Nonlinear Dynamics Effects of APPLE-II Type EPUs at the ALS	2152
	C. Steier, S. Marks, S. Prestemon, D. Robin, D. Schlueter, W. Wan, W. Wittmer LBNL, Berkeley, California
	Elliptically Polarizing Undulators (EPUs) have become more and more popular at synchrotron radiation sources, providing full polarization control of the photon beam. The fields of the most commonly used APPLE-II type EPUs have a very fast, intrinsic field roll-off, creating significant non-linearities of the beam motion with in some cases large impact on the dynamic (momentum) aperture. In general, the nonlinear effects get stronger with longer periods and higher undulator magnetic fields. One of the planned future beamlines at the ALS (MERLIN) will use a quasiperiodic EPU with 9 cm period and maximum B fields of about 1.3 T. We will present simulation studies for the proposed shimming schemes for this future device to reduce the nonlinear effects to acceptable values, as well as experimental studies for the existing 5 cm period EPUs already installed in the ALS.
WEPCH103	Ion Effects in the Electron Damping Ring of the International Linear Collider	2155
	L. Wang, T.O. Raubenheimer SLAC, Menlo Park, California A. Wolski Liverpool University, Science Faculty, Liverpool
	Ion-induced beam instabilities and tune shifts are critical issues for the electron damping ring of the International Linear Collider (ILC). To avoid conventional ion trapping (multi-turn trapping), a long gap is introduced in the electron beam by omitting a number of successive bunches out of a long train. However, the beam can still suffer from the fast ion instability (FII), driven by ions that last only for a single passage of the electron bunches. Our study shows that the ion effects can be significantly mitigated by using multiple gaps, so that the stored beam consists of a number of relatively short bunch trains. The ion effects in the ILC damping rings are investigated using both analytical and numerical methods.
WEPCH104	Observation of the Long-range Beam-beam Effect in RHIC and Plans for Compensation	2158
	W. Fischer, R. Calaga BNL, Upton, Long Island, New York U. Dorda, J.-P. Koutchouk, F. Zimmermann CERN, Geneva A.C. Kabel SLAC, Menlo Park, California J. Qiang LBNL, Berkeley, California V.H. Ranjibar, T. Sen Fermilab, Batavia, Illinois J. Shi KU, Lawrence, Kansas
	At large distances the electromagnetic field of a wire is the same as the field produced by a bunch. Such a long-range beam-beam wire compensator was proposed for the LHC, and single beam tests with wire compensators were successfully done in the SPS. RHIC offers the possibility to test the compensation scheme with colliding beams. We report on measurements of beam loss measurements as a function of transverse separation in RHIC at injection, and comparisons with simulations. We present a design for a long-range wire compensator in RHIC.