| Paper | Title | Page |
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| MOPEC037 | High Beta Operation Scenarios for Crab Cavities in the Insertion Region 4 of the CERN Large Hadron Collider | 540 |
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IR4 is a potential candidate for the installation of crab cavities in the CERN Large Hadron Collider. In this paper we present several operational scenarios in which the effect of the kick imparted by the cavity is enhanced by performing a dynamic unsqueeze of the beta function at collision energy. Linear optics, power supply requirements, beam aperture and finally potential luminosity increase studies will be discussed in order to rank and assess the feasibility of the various options. |
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| TUPD020 | Studies of Space Charge Effects in the Proposed CERN PS2 | 1964 |
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A new proton synchrotron, the PS2, is under design study to replace the the current proton synchrotron at CERN for the LHC upgrade. Nonlinear space charge effects could cause significant beam emittance growth and particle losses and limit the performance of the PS2. In this paper, we report on studies of the potential space-charge effects at the PS2 using three-dimensional self-consistent macroparticle tracking codes, IMPACT, MaryLie/IMPACT, and Synergia. We will present initial benchmark results among these codes. Effects of space-charge on the emittance growth, especially due to synchrotron coupling, and the aperture sizes will also be discussed. |
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| WEPEB052 | SPS Ecloud Instabilities - Analysis of Machine Studies and Implications for Ecloud Feedback | 2806 |
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The SPS at high intensities exhibits transverse single-bunch instabilities with signatures consistent with an Ecloud driven instability. We present recent MD data from the SPS, details of the instrument technique and spectral analysis methods which help reveal complex vertical motion that develops within a subset of the injected bunch trains. The beam motion is detected via wide-band exponential taper striplines and delta-σ hybrids. The raw sum and difference data is sampled at 50 GHz with 1.8 GHz bandwidth. Sliding window FFT techniques and RMS motion techniques show the development of large vertical tune shifts on portions of the bunch of nearly 0.025 from the base tune of 0.185. Results are presented via spectrograms and rms bunch slice trajectories to illustrate development of the unstable beam and time scale of development along the injected bunch train. The study shows that the growing unstable motion occupies a very broad frequency band of 1.2 GHz. These measurements are compared to numerical simulation results, and the system parameter implications for an Ecloud feedback system are outlined. |
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| WEPEB054 | Analysis of the Performance of the SPS Exponential Coupler Striplines using Beam Measurements and Simulation Data | 2812 |
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The SPS exponential coupler stripline are used to study single bunch instabilities. An accurate description of the response of the pickup is required to obtain high resolution measurements of the bunch vertical motion along the longitudinal axis. In this study we present the results of the comparison between dedicated beam experiments and electromagnetic simulations of a geometrical model of the stripline. |
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| MOPEC023 | RHIC Performance for FY10 200 GeV Au+Au Heavy Ion Run | 507 |
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Since the last successful RHIC Au+Au run in 2007 (Run7), the RHIC experiments have made numerous detector improvements and upgrades. In order to benefit from the enhanced detector capabilities and to increase the yield of rare events in the acquired heavy ion data a significant increase in luminosity is essential. In Run7 RHIC achieved an average store luminosity of <L>=12x1026 cm-2 s-1 by operating with 103 bunches (out of 110 possible), and by squeezing to β*=0.8 m. Our goal for this year's run, Run10, was to achieve an average of <L>=27x1026 cm-2 s-1. The measures taken were decreasing β* to 0.6 m, and reducing longitudinal and transverse emittances by means of bunched-beam stochastic cooling. In addition we introduced a lattice to suppress intra-beam scattering (IBS) in both RHIC rings, upgraded the RF system, and separated transition crossings in both rings while ramping. We present an overview of the changes and the results in terms of Run10 increased instantaneous luminosity, luminosity lifetime, and integrated luminosity. |
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| TUPD018 | Electron-cloud Build-up Simulations in the Proposed PS2: Status Report | 1958 |
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A replacement for the PS storage ring is being considered, in the context of the future LHC accelerator complex upgrade, that would likely place the new machine (the PS2) in a regime where the electron-cloud (EC) effect might be an operational limitation. We report here our present understanding of the ECE build-up based on simulations. We focus our attention on the bending magnets and the field-free regions, and consider both proposed bunch spacings of 25 and 50 ns. The primary model parameters exercised are the peak secondary emission yield (SEY) δmax, and the electron-wall impact energy at which SEY peaks, Emax. By choosing reasonable values for such quantities, and exploring variations around them, we estimate the range for the EC density ne to be expected in nominal operation. We present most of our results as a function of bunch intensity Nb, and we provide a tentative explanation for a curious non-monotonic behavior of ne as a function of Nb. We explore the sensitivity of ne to other variables such as the beam pipe radius in the field-free regions. |
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| TUPD072 | E-cloud Driven Single-bunch Instabilities in PS2 | 2087 |
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One of the options under consideration for a future upgrade of the LHC injector complex includes the replacement of PS with PS2 (a longer circumference and higher energy ring). Efforts are currently underway to design the new machine and characterize the beam dynamics. Electron cloud effects represent a potentially serious limitation to the achievement of the upgrade goals. We report on ongoing numerical studies aiming at estimating the e-cloud density threshold for the occurrence of single bunch instabilities or significant degradation of the beam emittance. We present selected results obtained in the more familiar quasi-static approximation and/or in the Lorentz-boosted frame. |