| Paper | Title | Page |
|---|---|---|
| MOPC009 | Experiments on LHC Long-Range Beam-Beam Compensation and Crossing Schemes at the CERN SPS in 2004 | 686 |
|
||
| Experiments with two prototype long-range beam-beam compensators (current-carrying wires) during the 2004 CERN SPS run explored the efficiency of a proposed long-range beam-beam compensation for the LHC. In addition, the SPS compensators were also used to 'simulate' the effect of different planes of crossing at two LHC interaction points. We present the experimental results and compare them with computer simulations. | ||
| MPPE009 | 2003-2004 Nonlinear Optics Measurements and Modeling for the CERN SPS | 1171 |
|
||
| In 2003 and 2004 nonlinear chromaticity, amplitude detuning, chromatic phase advance, resonance driving terms and off-energy orbits were measured in the CERN SPS at 14 GeV/c and 26 GeV/c, respectively. From the nonlinear chromaticity, the SPS optics model has been updated, by adjusting the strength of nonlinear field errors in dipoles and quadrupoles. Furthermore, we have added to the model the effect of the displacement of all main bends and the voluntary misalignments of all the other elements of the machine. We compare the field errors with those founded in 2002, 2001 and 2000. The tune shifts with transverse amplitude, driving terms, etc., predicted by this nonlinear optics model are compared with direct measurements. | ||
| MPPE044 | Damping Wiggler Study at KEK-ATF | 2809 |
|
||
| The effects by damping wiggler magnets have been studied at KEK-ATF. The damping ring of the KEK-ATF is a 1.3 GeV storage ring capable of producing ultra-low emittance electron beams. It is significant issue to realize fast damping in the damping ring. The tuning method with 4 sets of wiggler was investigated for the ultra-low emittance beam. The performance on the beam quality, which is related to the transverse (x and y) and the longitudinal (z and dp/p), has been measured by the SR monitor, the laser wire, the streak camera and the energy spread monitor at the extraction line. We report on the operation condition and the measurement results. | ||
| TPAP003 | Exploring a Nonlinear Collimation System for the LHC | 877 |
|
||
| We explore the adaptation of a nonlinear collimation system, as previously considered for linear colliders, to LHC betatron cleaning. A possible nonlinear system for LHC consists of a horizontal and vertical primary collimator located in between a pair of skew sextupoles. We discuss the modified LHC optics, the need for and optimum placement of secondary absorbers, and the simulated cleaning efficiency. | ||
| TPPP010 | Photon-Nucleon Collider Based on LHC and CLIC | 1207 |
|
||
| We describe the scheme of a photon-nucleon collider where high-energy photons generated by Compton back-scattering off a CLIC electron beam, at either 75 GeV or 1.5 TeV, are collided with protons or ions stored in the LHC. Different design constraints for such a collider are discussed and the achievable luminosity performance is estimated. | ||
| TPAP008 | Measurements of the LHC Collimator Impedance with Beam in the SPS | 1132 |
|
||
| The transverse impedance of the LHC collimators will likely dominate the overall transverse impedance in the LHC at high energies and potentially limit the maximum intensity. A prototype collimator was recently tested in the SPS. Small, but significant tune shifts depending on the collimator position have been observed using different independent high resolution tune measurement methods. In addition trapped modes predicted from numerical simulation at the ends of the collimator jaws have been identified by bench measurement techniques as well as with the beam. We present a description of the measurements and an analysis of the results. | ||
| TPPP007 | Recent Progress at KEKB | 1045 |
|
||
| We summarize the machine operation of KEKB during past one year. Progress for this period, causes of present performance limitations and future prospects are described. | ||
| WPAE029 | Tevatron Beam-beam Compensation Project Progress | 2083 |
|
||
|
Funding: Work supported by the Universities Research Assos., Inc., under contract DE-AC02-76CH03000 with the U.S. Dept. of Energy. The 2nd Tevatron electron lens (TEL2) is under the final phase of development and prepare for the installation in the Tevatron. In this report, we will describe the system and the main upgrades from the TEL1. We will also show the magnetic field measurement results, beam testing and plan for installation. The special operation consideration of the TEL2 under high radiation dose will also be discussed. |
||
| ROPB007 | 3-D Parallel Simulation Model of Continuous Beam-Electron Cloud Interactions | 549 |
|
||
| A 3D Particle-In-Cell model for continuous modeling of beam and electron cloud interaction in a circular accelerator is presented. A simple model for lattice structure, mainly the Quadruple and dipole magnets and chromaticity have been added to a plasma PIC code, QuickPIC, used extensively to model plasma wakefield acceleration concept. The code utilizes parallel processing techniques with domain decomposition in both longitudinal and transverse domains to overcome the massive computational costs of continuously modeling the beam-cloud interaction. Through parallel modeling, we have been able to simulate long-term beam propagation in the presence of electron cloud in many existing and future circular machines around the world. The exact dipole lattice structure has been added to the code and the simulation results for CERN-SPS and LHC with the new lattice structure have been studied. Also the simulation results are compared to the results from the two macro-particle modeling for strong head-tail instability. It is shown that the simple two macro-particle model can capture some of the physics involved in the beam- electron cloud interaction qualitatively. | ||
| RPPP007 | CLIC Damping Ring Optics Design Studies | 1060 |
|
||
| In this paper the nonlinearities induced by the short period NbFeB permanent wiggler optimized for the CLIC damping ring and their influence to the beam dynamics are studied. | ||
| RPPP008 | The Short Circumference Damping Ring Design for the ILC | 1126 |
|
||
| The ILC damping ring tentative design is driven by the operational scenario of the main linac, the beam-dynamics demand of producing a stable and high-quality beam, the injection/extraction scheme and the kicker performance. In this paper, a short circumference damping ring design based on TME cells is described. The ring accommodates injection kickers which provide a flat top of 280 nsec and a 60 nsec rise and fall time and very fast strip-line kickers for beam extraction with a 2 nsec rise and fall time for 3-MHz operation. The potential impact of collective effects and the possible degradation of the dynamic aperture by nonlinear-wiggler fields are estimated. | ||
| RPPP012 | Collective Effects in the CLIC Damping Rings | 1312 |
|
||
| The small emittance, short bunch length, and high current in the CLIC damping ring could give rise to collective effects which degrade the quality of the extracted beam. In this paper, we survey a number of possible instabilities and estimate their impact on the ring performance. The effects considered include fast beam-ion instability, coherent synchrotron radiation, and electron cloud, in addition to conventional single and multi-bunch instabilities. | ||
| RPPP045 | Single-Bunch Instability Driven by the Electron Cloud Effect in the Positron Damping Ring of the International Linear Collider | 2884 |
|
||
|
Funding: Work supported by the U.S. DOE under contracts DE-AC02-76SF00515. With the recommendation that the future International Linear Collider (ILC) should be based on superconducting technology, there is considerable interest in exploring alternate designs for the damping rings (DR). The TESLA design was 17 km in circumference with a "dog-bone" configuration. Two other smaller designs have been proposed that are 6 km and 3 km in length. In the smaller rings, collective effects may impose the main limitations. In particular for the positron damping ring, an electron cloud may be produced by ionization of residual gas or photoelectrons and increase through the secondary emission process. The build-up and development of an electron cloud is more severe with the higher average beam current in the shorter designs. In this paper, we present recent computer simulation results for the electron cloud build-up and instability thresholds for the various DR configurations. |
||
| FPAP001 | Electron Cloud Build-Up Study for DAFNE | 779 |
|
||
| After the first experimental observations compatible with the presence of the electron cloud effect in the DAFNE positron ring, a more systematic study has been performed regarding the e-cloud build-up and related instability. The measured field map of the magnetic field has been taken into account in the simulation for elements present in the four 10 m long bending sections, representing 40% of the whole positron ring. The simulation results obtained with different codes are presented and compared with the recent experimental observations performed on the beam instabilities and the vacuum behavior of the positron ring. | ||
| FPAP013 | Emittance Growth Caused by Electron Cloud Below the “Fast TMCI” Threshold: Numerical Noise or True Physics? | 1344 |
|
||
| Simulations show a persisting slow emittance growth for electron cloud densities below the threshold of the fast Transverse Mode Coupling type instability, which could prove important for proton beams with negligible radiation damping, such as in the LHC. We report on a variety of studies performed to quantify the contributions to the simulated emittance growth from numerical noise in the PIC module and from an artificial resonance excitation due to the finite number of kicks per turn applied for modeling the cloud-bunch interaction. | ||
| FPAP014 | Electron Cloud Measurements in the SPS in 2004 | 1371 |
|
||
| Novel measurements of the electron cloud have been performed in the SPS in 2004. In this machine the beam consists of a number of short bunch trains. By varying the distance between these trains it is possible to witness the survival of the electrons after the bunch passage. In this paper, results from simulations and experiments are compared. | ||
| FPAP022 | Long Time Simulation of LHC Beam Propagation in Electron Clouds | 1769 |
|
||
| In this report we show the simulation results of single-bunch instabilities caused by interaction of a proton beam with an electron cloud for the Large Hadron Collider (LHC) using the code QuickPIC [1]. We describe three new results: 1) We test the effect of the space charge of the beam on itself; 2) we add the effect of dispersion in the equation of motion in the x direction, and 3) we extend previous modeling by an order of magnitude (from 50ms to 500ms) of beam circulation time. The effect of including space charge is to change the emittance growth by less than a few percent. Including dispersion changes the plane of instability but keeps the total emittance approximately the same. The longer runs indicate that the long term growth of electron cloud instability of the LHC beam cannot be obtained by extrapolating the results of short runs. | ||
| ROPB004 | Effect of Lattice and Electron Distribution in Electron-Cloud Instability Simulations for the CERN SPS and LHC | 387 |
|
||
| Several simulation codes have been adapted so as to model the single-bunch electron-cloud instability including a realistic variation of the optical functions with longitudinal position. In addition, the electron cloud is typically not uniformly distributed around the ring, as frequently assumed, but it is mainly concentrated in certain regions with specific features, e.g., regions which give rise to strong multipacting or suffer from large synchrotron radiation flux. Particularly, electrons in a dipole magnet are forced to follow the vertical field lines and, depending on the bunch intensity, they may populate two vertical stripes, symmetrically located on either side of the beam. In this paper, we present simulation results for the CERN SPS and LHC, which can be compared with measurements or analytical predictions. | ||
| RPPP003 | Proposal of the Next Incarnation of Accelerator Test Facility at KEK for the International Linear Collider | 874 |
|
||
| The realization of the International Linear Collider (ILC) will require the ability to create and reliably maintain nanometer size beams. The ATF damping ring is the unique facility where ILC emittancies are possible. In this paper we present and evaluate the proposal to create a final focus facility at the ATF which, using compact final focus optics and an ILC-like bunch train, would be capable of achieving 35nm beam size. Such a facility would enable the development of beam diagnostics and tuning methods, as well as the training of young accelerator physicists. | ||
| RPPP036 | A Test Facility for the International Linear Collider at SLAC End Station A for Prototypes of Beam Delivery and IR Components | 2461 |
|
||
|
Funding: U.S. Department of Energy. The SLAC Linac can deliver damped bunches with ILC parameters for bunch charge and bunch length to End Station A (ESA). A 10Hz beam at 28.5 GeV energy can be delivered to ESA, parasitic with PEP-II operation. During the engineering design phase for the ILC over the next 5 years, we plan to use this facility to prototype and test key components of the Beam Delivery System (BDS) and Interaction Region (IR). We discuss our plans for this ILC Test Facility and preparations for carrying out experiments related to Collimator Wakefields, Materials Damage Tests and Energy Spectrometers. We also plan an IR Mockup of the region within 5 meters of the ILC Interaction Point to investigate effects from backgrounds and beam rf higher-order modes (HOMs). |