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| MOAA003 | PEP-II and KEKB Operational Status | injection, interaction-region, beam-beam-effects, collider | 276 |
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Funding: Work supported by DOE contract DE-AC02-76SF00515. The present two B-Factories, KEKB at Tsukuba in Japan and PEP-II at SLAC in California, operate at the Upsilon 4S and have reached parameter levels unprecedented for e+e- colliders. They have provided very large data samples for their respective particle detectors, BELLE and BaBar. Luminosities are approaching 1 x 1034/cm2/s and beyond. Beam currents have reached over 2.5 A with 1600 positron bunches spaced by 4 nsec. Continuous injection with the detectors taking data has added significantly to data collection rates. Bunch-by-bunch feedback systems damp strong longitudinal and transverse coupled bunch instabilities. The beam-beam interaction has allowed high tune shift levels even in the presence of parasitic crossing and crossing angle effects. Both B-Factory colliders have significant near term luminosity improvement programs. |
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| MOAA004 | RHIC Operational Status | electron, polarization, proton, ion | 358 |
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Funding: Work was performed under the auspices of the U.S. Department of Energy. As the first hadron accelerator and collider consisting of two independent superconducting rings RHIC has operated with a wide range of beam energies and particle species. Machine operation and performance will be reviewed that includes high luminosity gold-on-gold and copper-on-copper collisions at design beam energy (100 GeV/u), asymmetric deuteron-on-gold collisions as well as high energy polarized proton-proton collisions (100 GeV on 100 GeV). Plans for future upgrades of RHIC will also be discussed. |
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| MOAA005 | FNAL Tevatron Operational Status | antiproton, proton, collider, electron | 484 |
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Funding: Work supported by the Universities Research Assos., Inc., under contract DE-AC02-76CH03000 with the U.S. Dept. of Energy. The Fermilab Tevatron Proton-Antiproton Collider is currently the world’s highest energy hadron collider. The luminosity of the Fermilab collider has been significantly increased with the Main Injector operating at its design goals. Further increases in luminosity have been the result of combining antiprotons from the Recycler and Accumulator storage rings. Recent commissioning of proton slip-stacking in the Main Injector has noticeably increased the antiproton accumulation rate. The increased stacking rate permits the sustained operation of using antiprotons from both the Accumulator and Recycler. Further increases in peak luminosity are expected from electron cooling in the Recycler and increased antiproton flux from the Antiproton Source. |
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| MOPA002 | Performance Limitations in High-Energy Ion Colliders | ion, electron, heavy-ion, injection | 122 |
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Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886. High-energy ion colliders (hadron colliders operating with species other than protons) are premier research tools for nuclear physics. The collision energy and high luminosity are important design and operations considerations. However, the experiments also expect flexibility with frequent changes in the collision energy, lattice configuration, and ion species, including asymmetric collisions. For the creation, acceleration, and storage of bright intense ion beams, attention must be paid to space charge, charge exchange, and intra-beam scattering effects. The latter leads to luminosity lifetimes of only a few hours for heavy ions. Ultimately cooling at full energy is needed to overcome this effect. Currently, the Relativistic Heavy Ion Collider at BNL is the only operating high-energy ion collider. The Large Hadron Collider, under construction at CERN, will also run with heavy ions. |
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| MOPC006 | Simulations and Experiments of Beam-Beam Effects in e+e- Storage Rings | simulation, positron, electron, damping | 520 |
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Funding: Work partially supported by the Department of Energy under Contract No. DE-AC02-76SF00515. Over the past decade, extensive simulations of beam-beam effects in positron-electron collliders, based on the particle-in-cell method, were developed to explain many complex experimental observations. Recently, such simulations were used to predict the future luminosity performance of e+e- colliders. Some predictions have been proven to be correct in the existing accelerators. In this paper, many effects such as dynamic beta, beam-beam limit, crossing angle, parasitic collisions, betatron spectrum, and beam-beam lifetime, will be reviewed from the viewpoints of both simulation and experiment. Whenever possible, direct comparisons between the predictions of the simulation and the corresponding experimental results will be provided. |
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| MOPC008 | Dynamic Beam-Beam Effects Measured at KEKB | emittance, electron, beam-beam-effects, positron | 606 |
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Funding: This work is partially supported by Grant-in-Aid Scientific Research (16540271) from Japan Society for the Promotion of Science and Technology. KEKB is a multi-bunch, high-current, electron/positron collider for B meson physics. The two beams collide at one interaction point (IP) with a finite horizontal crossing angle and with a bunch-space of 6 to 8 ns. The luminosity achieved at KEKB is the best in the world. The betatron tunes are set close to a half integer, to expect the dynamic beam-beam effects that change the beta function around the rings and the emittance as a function of the beam-beam parameter. In order to investigate such attractive beam-beam effects, the beam-beam kick and the beam-beam tune-shift were obtained by comparing the beam parameters between a colliding bunch and a non-colliding one. The horizontal beam size at the IP estimated from a beam-beam kick curve was slightly less than a calculated value without the dynamic effect. The horizontal emittance estimated from the beam-beam tune shift was somewhat larger than a calculated natural emittance. These experimental results reflect the dynamic beam-beam effects. |
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| MPPE031 | Simulation of Resonance Streaming at the eRHIC Electron Storage Ring | electron, simulation, damping, background | 2215 |
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Funding: Work performed under the auspices of the U.S. Department of Energy. To estimate electron beam lifetime and detector background at the future electron-ion collider eRHIC, knowledge of the electron beam halo region is essential. Simulations have been performed to determine the deviation of the transverse beam profile from a Gaussian distribution. |
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| MPPE057 | Measurement of the Vertical Emittance and Beta Function at the PEP-II Interaction Point Using the BaBar Detector | emittance, storage-ring, positron, factory | 3387 |
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Funding: U.S. Department of Energy. We present measurements of the effective vertical emittance and IP beta function in the PEP-II Asymmetric B Factory. These beam parameters are extracted from fits to the longitudinal dependence of the luminosity and of the vertical luminous size, measured using e+ e- –> mu+ mu- events recorded in the Babar detector. The results are compared, for different sets of machine conditions, to accelerator-based measurements of the optical functions of the two beams. |
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| MPPE058 | Virtual Accelerator for Accelerator Optics Improvement | coupling, optics, quadrupole, lattice | 3426 |
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Funding: Work supported by Department of Energy contract DE-AC02-76SF00515. Through determination of all quadrupole strengths and sextupole feed-downs by fitting quantities derivable from precision orbit measurement, one can establish a virtual accelerator that matches the real accelerator optics. These quantities (the phase advances, the Green's functions, and the coupling eigen-plane ellipses tilt angles and axis ratios) are obtained by analyzing turn-by-turn Beam Position Monitor (BPM) data with a model-independent analysis (MIA). Instead of trying to identify magnet errors, a limited number of quadrupoles are chosen for optimized strength adjustment to improve the virtual accelerator optics and then applied to the real accelerator accordingly. These processes have been successfully applied to PEP-II rings for beta beating fixes, phase and working tune adjustments, and linear coupling reduction to improve PEP-II luminosity. |
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| MPPE061 | Measurement and Correction of Nonlinear Chromaticity in RHIC | octupole, insertion, optics, sextupole | 3523 |
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Funding: Work performed under Contract Number DE-AC02-98CH10886 with the auspices of the U.S. Department of Energy. To improve luminosity in RHIC by using smaller Beta,* higher order chromatic effects may need to be corrected. Measuring of higher order chromaticities is discussed and compared to a model of RHIC, showing good agreement. Assuming round beams, four families of octupoles are used to correct the second order chromaticities while keeping under control the amplitude dependent betatron tune spread in the beams. We show that the octupoles can reduce the second order chromaticity in RHIC, but they have insufficient strength for complete correction. |
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| MPPE065 | Fully Coupled Analysis of Orbit Response Matrices at the FNAL Tevatron | quadrupole, coupling, optics, storage-ring | 3662 |
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Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38, and by the Universities Research Association, Inc., under contract DE-AC02-76CH03000 with the U.S. Dept. of Energy. Optics measurements have played an important role in improving the performance of the FNAL Tevatron collider. Initial optics measurements were performed using a small number of differential orbits, which allowed us to carry out the first round of optics corrections. However, because of insufficient accuracy, it was decided to apply the response matrix analysis method for further optics improvements. The response matrix program developed at ANL has been expanded to include coupling – the essential feature required to describe the Tevatron optics. The results of the optics calibration are presented and compared to local beta function measurements. |
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| MPPT037 | Design Study of Superconducting Magnets for the Super-KEKB Interaction Region | quadrupole, superconducting-magnet, interaction-region, multipole | 2470 |
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| The KEKB accelerator has achieved the highest luminosity of 1.39E1034cm-2s-1 at June-03-2004. For getting the higher luminosity over 1E1035cm-2s-1, the KEKB accelerator group continues to study the upgraded machine of the KEKB, that is the Super-KEKB. The designed machine parameters for this Super-KEKB are the vertical beta of 3 mm at the interaction point (IP), the LER and HER currents of 9.4 A and 4.1 A, and the half crossing angle of 15 mrad for the target luminosity of 1-5E1035cm-2s-1. For achieving these beam parameters, the superconducting magnets (final focus quadrupoles and compensation solenoids) are newly required to design. The magnet-cryostats have very tight spatial constraints against the Belle particle detector and the beam pipe so that the beam and the synchrotron light do not have any interference with the beam pipe. In this design, the final focus quadrupoles generate the field gradient of 42.3 T/m and their effective magnetic lengths are 0.30m and 0.36m in each side with respect to the IP, respectively. The compensation solenoids are overlaid with the quadrupoles. We will report the design of these magnets in detail and show the difficulties for the Super-KEKB-IR. | |||
| MPPT043 | Low-Beta Quadrupole Designs for the LHC Luminosity Upgrade | quadrupole, insertion, dipole, multipole | 2795 |
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| Several candidate scenarios are considered for the upgrade of the LHC insertions in view of increasing the luminosity in excess of 1034 cm-2s-1. In all cases, superconducting low-beta quadrupoles with apertures in the range of 90-110 mm are required in view of increased heat loads and beam crossing angles. We present possible low-beta quadrupole designs based on Nb3Sn and NbTi superconducting cables, including existing LHC-class superconductors, present scaling laws for the magnet parameters and discuss relative advantages of the underlying triplet layouts. | |||
| MPPT049 | Optimization of Open Midplane Dipole Design for LHC IR Upgrade | dipole, optics, radiation, quadrupole | 3055 |
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Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-98CH10886. The proposed ten-fold increase in Large Hadron Collider (LHC) luminosity requires high field (~15 T) magnets that are subjected to the high radiation power of ~9 kW/per beam directed towards each interaction region. This has a major impact in the design of first dipole in the "Dipole First" optics. The proposed design allows sufficient clear space between coils so that most of the particle showers from the interaction points (concentrated at the midplane due to strong magnetic field) can be transported outside the coil region to a warm absorber thus drastically reducing the peak power density in the coils and removing heat at a higher (nitrogen) temperature. The concept, however, presents several new technical challenges: (a) obtaining good field quality despite a large midplane gap, (b) minimizing peak fields on coil, (c) dealing with large vertical forces with no structure between the coils, (d) minimizing heat deposition in the cold region, (e) designing a support structure. Designs with different horizontal and vertical coil spacing are presented that offer significant savings in the operating and infrastructure cost of the cryo-system, providing reliable quench-stable operation with a lifetime of the critical components of at least ten years. |
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| MPPT080 | Design, Fabrication and Characterization of a Large-Aperture Quadrupole Magnet for CESR-c | quadrupole, photon, alignment, focusing | 4063 |
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Funding: National Science Foundation. Installation of a radiative Bhabha luminosity monitor for CESR-c operation in 2004 required replacing a 40-mm aperture steel quadrupole magnet with one of aperture 75 mm, while maintaining field-quality tolerances at the level of a few parts in $104. We present the design methodology using 2D- and 3D-finite-element field calculations, compare the calculated 3D integrals to flip-coil measurements, and discuss related mechanical tolerances. |
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| TOAA002 | U.S. Accelerator Contribution to the LHC | quadrupole, alignment, dipole, interaction-region | 184 |
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| In 1998, the United States entered into an agreement with CERN to help build the Large Hadron Collider (LHC), with contributions to the accelerator and to the large HEP detectors. To accomplish this, the US LHC Accelerator Project was formed, encompassing expertise from Brookhaven National Laboratory, Fermi National Accelerator Laboratory and the Lawrence Berkeley National Laboratory. Contributions from the US LHC Accelerator project included superconducting high gradient quadrupoles and beam separation dipoles for the four interaction regions and the RF section; feedboxes for cryogenic, power and instrumentation distribution; neutral and hadron beam absorbers in the high luminosity regions; design of the inner triplet cryogenic system; beam tracking studies utilizing the design IR magnet field quality and magnet alignment; particle heat deposition studies in the IR’s; and short sample characterization of superconducting cables used in the arc dipoles and quadrupoles. This report is a summary of these contributions including the progress towards project completion, as well as a discussion of future plans for US participation in the LHC accelerator. | |||
| TPAP012 | Luminosity Limit from Bound-Free Pair Production in the LHC | ion, simulation, dipole, proton | 1306 |
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| The luminosity of the LHC as a lead-ion collider is known to be limited by the large cross-sections for electromagnetic processes in ultra-peripheral collisions. In particular, the process of bound-free e-e+ pair production creates secondary beams of Pb81+ ions emerging from the collision points and impinging on the vacuum envelope inside superconducting magnets. New Monte-Carlo simulations, exploiting recent implementations of the physics of ion interactions with matter, are helping us to quantify the relationships among luminosity, energy deposition in the magnet coils and signals on beam loss monitors with a view to predicting and alleviating the quench limit on luminosity. | |||
| TPAP021 | A New Technique for Making Bright Proton Bunches using Barrier RF Systems | proton, emittance, simulation, collider | 1745 |
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Funding: Work supported by the Universities Research Association, Inc., under contract DE-AC02-76CH03000 with the U.S. Department of Energy. I describe here very promising schemes for producing high intensity low longitudinal emittance proton bunches for pp and ppbar high energy colliders. These methods are based on the use of wide-band barrier rf systems in the up-stream circular accelerators. The beam dynamics simulations clearly suggest that these schemes allow a wide range of bunch intensities and longitudinal emittances. In this paper I present the principle of these methods and results of multi-particle beam dynamics simulations applied to the Fermilab Tevatron. The feasibility of these methods to LHC pp collider will also be discussed. I also review a few other schemes which have been adopted and investigated at collider facilities. |
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| TPAP022 | Mixed pbar Source Operation at the Fermilab Tevatron | injection, acceleration, collider, simulation | 1763 |
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Funding: Work supported by the Universities Research Association, Inc., under contract DE-AC02-76CH03000 with the U.S. Department of Energy. Recently, we have adopted a scheme called "Mixed pbar Source Operation" to transfer 2.5 MHz pbar bunches from the Recycler and the Accumulator to the Fermilab Main Injector (MI). In this scheme, 2.5MHz pbar bunches are captured adiabatically in 53 MHz buckets at 8 GeV in the MI and accelerated to 150 GeV before bunch coalescing and transfer to the Tevatron collider stores. A special magnet ramp was needed in the MI to allow for pbar beam of slightly different 8 GeV energies from the Recycler and the Accumulator. Here we present the details of the scheme and its advantage over the method used for past several years. |
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| TPAP026 | Improving the Tevatron Collision Helix | antiproton, emittance, proton, beam-beam-effects | 1931 |
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| In the Tevatron, protons and pbars circulate in a single beam pipe, so electrostatic separators are used to create helical orbits that separate the two beams except at the two interaction points (IP). Increasing the separation outside of the IPs is desirable in order to decrease long range beam-beam effects during high energy physics (HEP) stores. We can increase separation by running the separators at higher gradients or by installing additional separators. We are pursuing both strategies in parallel. Here, we describe Tevatron operation with higher separator gradients and with new separators installed during a recent shutdown. We also describe possible future improvements. | |||
| TPAP032 | Beam-beam Effects in the Tevatron Run II | antiproton, proton, emittance, injection | 2245 |
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Funding: Work supported by the Universities Research Assos., Inc., under contract DE-AC02-76CH03000 with the U.S. Dept. of Energy. The Tevatron in Collider Run II (2001-present) is operating with many times higher beam intensities and luminosities than in previous Run I (1992-1995). Electromagnetic long-range and head-on interactions of high intensity proton and antiproton beams have been significant sources of beam loss and lifetime limitations. We present observations of the beam-beam phenomena in the Tevatron and results of relevant beam studies. We analyze the data and various methods employed in operations, predict the performance at upgraded beam parameters and luminosity and discuss possible improvements. |
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| TPAP036 | Fitting the Luminosity Decay in the Tevatron | antiproton, proton | 2434 |
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Funding: Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy. This paper explores the various ways in which the decay of the luminosity in the Tevatron have been fit. The standard assumptions of a fixed-lifetime exponential decay are only appropriate for very short time intervals. A "1/time" funcional form fits rather well, and is supported by analytical derivations. A more complex form, assuming a time-varying lifetime, produces excellent results. Changes in the luminosity can be factored into two phenomena: The luminosity burn-off rate, and the burn-off rate from non-luminosity effects. The luminous and the non-luminous burn rate are shown for stores in the Tevatron. |
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| TPAP037 | Monte Carlo of Tevatron Operations, Including the Recycler | antiproton, proton, emittance, electron | 2479 |
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Funding: Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy. A Monte Carlo model, which was originally developed for "Run I" of the Tevatron Collider, has been enhanced in many ways, most notably, to incorporate the effect of the Recycler Ring. This model takes into account reasonable random fluctuations in the performance of the Collider, and normal interruptions in operation of each accelerator due to downtime. Optimization of the integrated luminosity delivered to the experiments is based on when to end the store and how to deal with the anitprotons. Preliminary results show that a 20% gain in integrated luminosity in the Collider results from using the Recycler for one-third of the anitprotons in each store. As electron cooling becomes operative in the Recycler, Collider performance improves by as much as a factor of two. |
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| TPAP038 | Characterizing Luminosity Evolution in the Tevatron | proton, emittance, beam-beam-effects, antiproton | 2536 |
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Funding: Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy. We derive an approximate form of a luminosity evolution in a high intensity hadron collider taking into account the most important phenomena of intrabeam scattering (IBS), beam burn-up due to luminosity and beam-beam effects. It is well known that an exponential decay does not describe luminosity evolution very well unless the lifetime is allowed to vary with time. However, a "1/time" evolution, which this derivation shows is a good approximation, fits data from the Tevatron well. |
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| TPAP048 | Optimization of the Phase Advance Between RHIC Interaction Points | resonance, quadrupole, lattice, proton | 3031 |
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Funding: U.S. department of Energy. We consider the scenario of having two identical Interaction Points (IPs) in the Relativistic Heavy Ion Collider (RHIC). The strengths of beam-beam resonances strongly depend on the phase advance between these two IPs and therefore certain phase advances could improve beam lifetime and luminosity. We compute the dynamic aperture as function of the phase advance between these IPs to find the optimum settings. The beam-beam interaction is treated in the weak-strong approximation and a complete non-linear model of the lattice is used. For the current RHIC proton working point (0.69,0.685) the design lattice is found to have the optimum phase advance. However this is not the case for other working points. |
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| TPAP055 | Fast IR orbit feedback at RHIC | feedback, power-supply, coupling, emittance | 3298 |
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Funding: Work performed under the auspices of the US Department of Energy Mechanical low-beta triplet vibrations lead to horizontal jitter of RHIC beams at frequencies around 10 Hz. The resulting beam offsets at the interaction points are considered detrimental to RHIC luminosity performance. To stabilize beam orbits at the interaction points, installation of a fast orbit feedback is foreseen. A prototype of this system is being developed and tested. Recent results are presented. |
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| TPAP056 | Electron Beam Stability Requirements for Linac-Ring Electron-Ion Colliders | electron, simulation, ion, emittance | 3363 |
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Funding: Work performed under the auspices of the U.S. Department of Energy. In recent years, linac-ring electron-ion colliders have been proposed at a number of laboratories around the world. While the linac-ring approach overcomes the beam-beam tuneshift limitation on the electron beam, it also introduces noise into the ion beam, via the beam-beam interaction with electron bunches of slightly fluctuating intensity and transverse size. The effect of these fluctuations is studied using a linearized model of the beam-beam interaction. Upper limits for the rms jitter amplitudes of electron beam parameters for various linac-ring electron-ion colliders are presented. |
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| TPAP057 | Beam-Beam Simulations for the eRHIC Electron Ring | electron, simulation, resonance, emittance | 3399 |
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Funding: Work performed under the auspices of the U.S. Department of Energy. To study collisions between polarized electrons and heavy ions or polarized protons at high energy, adding a 10 GeV electron storage ring to the existing RHIC facility is currently under consideration. To achieve high luminosities, vertical beam-beam tuneshift parameters of 0.08 are required for the electron beam. Simulation studies are being performed to study the feasibility of these high tuneshift parameters and to explore the potential for even higher tuneshifts. Recent results of these studies are presented. |
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| TPAP058 | Beam-Beam Simulations for Double-Gaussian Beams | emittance, simulation, proton, electron | 3405 |
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Funding: Work performed under the auspices of the U.S. Department of Energy. Electron cooling together with intra-beam scattering results in a transverse distribution that can best be described by a sum of two Gaussians, one for the high-density core and one for the tails of the distribution. Simulation studies are being performed to understand the beam-beam interaction of these double-Gaussian beams. Here we report the effect of low-frequency random tune modulations on diffusion in double-Gaussian beams and compare the effects to those in beam-beam interactions with regular Gaussian beams and identical tuneshift parameters. |
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| TPAT051 | Asymmetrical Spectrum Observed at the KEKB High Energy Electron Ring | electron, ion, vacuum, feedback | 3176 |
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| KEKB is a multi-bunch, high-current, electron/positron collider for B meson physics. The two beams collide at one interaction point (IP) with a finite horizontal crossing angle. The luminosity achieved at KEKB is the best in the world. In order to keep up the performance, the tune of a non-colliding bunch, placed just after a colliding bunch-train, is continuously monitored. It was observed that an electron bunch showed an asymmetrical distribution biased to a higher tune in the vertical tune-spectrum. We found that the asymmetrical spectrum was reinforced by the beam-beam interaction, though the electron bunch did not collide. The asymmetry was reinforced moreover, as the electron bunch approached a bunch-train further. These observations suggest that the asymmetry in the spectrum is not related to trapped-ions or fast-ions observed in an electron single beam, but related to ions produced by the beam-beam interaction, which makes the particles scattered and they might yield new ions due to the collision with residual gas. We can imagine that the ions are accumulated along a bunch-train and some ions survive after colliding bunches passed through in the electron ring. A quantitative analysis remains for future study. | |||
| TPAT076 | Measurement of the Luminous-Region Profile at the PEP-II IP, and Application to e± Bunch-Length Determination | monitoring, simulation, collider, optics | 3973 |
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| The three-dimensional luminosity distribution at the interaction point (IP) of the SLAC B-Factory is measured continuously, using e+e- –> e+e- and e+e –> mu+mu- events reconstructed online in the silicon tracker of the BaBar detector. The centroid of the transverse luminosity profile provides a very precise and reliable monitor of medium- and long-term orbit drifts at the IP. The longitudinal centroid is sensitive to variations in the relative RF phase of the colliding beams, both over time and differentially along the bunch train. The measured horizontal r.m.s. width of the distribution is consistent with a sizeable dynamic-beta effect; it is also useful as a benchmark of strong-strong beam-beam simulations. The longitudinal luminosity distribution depends on the e± bunch lengths and vertical IP beta-functions, which can be different in the high- and low-energy rings. Using independent estimates of the beta-functions, we analyze the longitudinal shape of the luminosity distribution in the presence of controlled variations in accelerating RF voltage and/or beam current, to extract separate measurements of the e+ and e- bunch lengths. | |||
| TPAT077 | Beam-Beam Study on the Upgrade of Beijing Electron Positron Collider | simulation, collider, injection, positron | 4000 |
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| It is an important issue to study the beam-beam interaction in the design and performance of such a high luminosity collider as BEPCII, the upgrade of Beijing Electron Positron Collider. The weak-strong simulation is generally used during the design of a collider. For performance a large scale tune scan, the weak-strong simulation studies on beam-beam interaction were done, and the geometry effects were taken into account The strong-strong simulation studies were done for investigating the luminosity goal and the dependence of the luminosity on the beam parameters. | |||
| TPAT083 | Computational Study of the Beam-Beam Effect in Tevatron Using the LIFETRAC Code | emittance, simulation, optics, antiproton | 4117 |
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Funding: Work supported by the Universities Research Assos., Inc., under contract DE-AC02-76CH03000 with the U.S. Dept. of Energy. Results of a comprehensive numerical study of the beam-beam effect in the Tevatron are presented including the dependence of the luminosity lifetime on the tunes, chromaticity and optics errors. These results help to understand the antiproton emittance blow-up routinely observed in the Tevatron after the beams are brought into collision. To predict a long term luminosity evolution, the diffusion rates are increased to represent long operation time (~day) by using a small number of simulated turns. To justify this approach, a special simulation study of interplay between nonlinear beam-beam resonances and diffusion has been conducted. A number of ways to mitigate the beam-beam effects are discussed, such as increasing bunch spacing, separation between the beams and beam-beam compensation with electron lenses. |
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| TPAT085 | Development of a Beam-Beam Simulation Code for e+e- Colliders | simulation, synchrotron, beam-beam-effects, positron | 4176 |
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Funding: Chinese National Foundation of Natural Sciences, contract 10275079 JSPS Core University Program BEPC will be upgraded into BEPCII, and the luminosity will be about 100 times higher. We developed a three dimensional strong-strong PIC code to study the beam-beam effects in BEPCII. The transportation through the arc is the same as that in Hirata's weak-strong code. The beam-beam force is computed directly by solving the Poisson equation using the FACR method, and the boundary potential is computed by circular convolution. The finite bunch length effect is included by longitudinal slices. An interpolation scheme is used to reduce the required slice number in simulations. The standard message passing interface (MPI) is used to parallelize the code. The computing time increases linearly with (n+1), where n is the slice number. The calculated luminosity of BEPCII at the design operating point is less than the design value. The best area in the tune space is near (0.505,0.57) according to the survey, where the degradation of luminosity can be improved. |
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| TPAT087 | The Effect of Magnetic Field Errors on Dynamical Friction in Electron Coolers | electron, simulation, ion, positron | 4206 |
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Funding: Work supported by US DOE grants DE-FG03-01ER83313 and DE-FG03-95ER40926.
A proposed luminosity upgrade to the Relativistic Heavy Ion Collider (RHIC) includes a novel electron cooling section,* which would use ~55 MeV electrons to cool fully-ionized 100 GeV/nucleon gold ions. A strong (1-5 T) solenoidal field will be used to magnetize the electrons and thus enhance the dynamical friction force on the ions. The physics of magnetized friction is being simulated for RHIC parameters, using the VORPAL code.** Most theoretical treatments for magnetized dynamical friction do not consider the effect of magnetic field errors, except in a parametric fashion.*** However, field errors can in some cases dramatically reduce the velocity drag and corresponding cooling rate. We present a simple analytical model for the magnetic field errors, which must be Lorentz transformed into the beam frame for use in our simulations. The simulated dynamical friction for the case of a perfect solenoidal field will be compared with results from this new model, for parameters relevant to RHIC.
*Fedotov et al., Proc. 33rd ICFA Adv. Beam Dynamics Workshop (2004). **Nieter & Cary, J. Comp. Phys. 196 (2004). ***Parkhomchuk, Nucl. Instr. Meth. Phys. Res. A 441 (2000). |
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| TPAT089 | Cooling Dynamics Studies and Scenarios for the RHIC Cooler | electron, ion, emittance, simulation | 4236 |
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Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-98CH10886 In this paper, we discuss various cooling dynamics studies for RHIC, such as an equilibrium process between intra-beam scattering within ion bunch and electron cooling, critical number of electrons needed, magnetized cooling logarithm and resulting requirements on parameters of electron beam, effects of solenoid errors, etc. We also present simulations of various possibilities of using electron cooling at RHIC, which includes cooling at the top energy, pre-cooling at low energy, aspects of transverse and longitudinal cooling and their impact on the luminosity. Electron cooling at various collision energies both for heavy ions and protons is also discussed. |
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| TPAT090 | Simulations of High-Energy Electron Cooling | electron, ion, simulation, emittance | 4251 |
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Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-98CH10886. High-energy electron cooling of RHIC presents many unique features and challenges. An accurate estimate of the cooling times requires a detailed calculation of the cooling process, which takes place simultaneously with various diffusive mechanisms in RHIC. In addition, many unexplored effects of high-energy cooling in a collider complicate the task of getting very accurate estimates of cooling times. To address these high-energy cooling issues, a detailed study of cooling dynamics based on computer codes is underway at Brookhaven National Laboratory. In this paper, we present an update on code development and its application to the high-energy cooling dynamics studies for RHIC. |
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| TPAT091 | IBS for Ion Distribution Under Electron Cooling | lattice, ion, emittance, simulation | 4263 |
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Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-98CH10886.
Standard models of the intra-beam scattering (IBS) are based on the growth of the rms beam parameters for a Gaussian beam distribution. As a result of electron cooling, the core of beam distribution is cooled much faster than the tails, producing a denser core. Formation of such a core is an important feature since it plays dominant role in the luminosity increase. A simple use of standard rms-based IBS approach may significantly underestimate IBS for the beam core. A detailed treatment of IBS, which depends on individual particle amplitudes, was recently proposed by Burov,* with an analytic formulation done for a Gaussian distribution. However, during the cooling process the beam distribution quickly deviates from a Gaussian profile. To understand the extent of the dense core formation in the ion distribution, the "core-tail" model for IBS, based on the diffusion coefficients for bi-Gaussian distributions, was employed in cooling studies for RHIC. In addition, the standard IBS theory was recently reformulated for rms parameters growth of a bi-Gaussian distribution by Parzen.** In this paper, we compare various approaches to IBS treatment for such distribution. Its impact on the luminosity is also discussed.
*A. Burov, FERMILAB-TM-2213 (2003). **G. Parzen, Tech Note C-AD/AP/150 (2004). |
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| TPAT093 | Operations and Performance of RHIC as a Cu-Cu Collider | collider, ion, emittance, background | 4281 |
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Funding: Work performed under the auspices of the U.S. Department of Energy. The 5th year of RHIC operations, started in November 2004 and expected to last till June 2005, consists of a physics run with Cu-Cu collisions at 100 GeV/u followed by one with polarized protons at 100 GeV. We will address here overall performance of the RHIC complex used for the first time as a Cu-Cu collider, and compare it with previous operational experience with Au, PP and asymmetric d-Au collisions. We will also discuss operational improvements, such as a ?* squeeze to 85cm in the high luminosity interaction regions from the design value of 1m, system improvements and machine performance limitations, such as vacuum pressure rise, intra-beam scattering, and beam beam interaction. |
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| TPAT095 | Beam Induced Pressure Rise at RHIC | electron, ion, background, proton | 4308 |
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Beam induced pressure rise in RHIC warm sections is currently one of the machine intensity and luminosity limits. This pressure rise is mainly due to electron cloud effects. The RHIC warm section electron cloud is associated with longer bunch spacings compared with other machines, and is distributed non-uniformly around the ring. In addition to the countermeasures for normal electron cloud, such as the NEG coated pipe, solenoids, beam scrubbing, bunch gaps, and larger bunch spacing, other studies and beam tests toward the understanding and counteracting RHIC warm electron cloud are of interest. These include the ion desorption studies and the test of anti-grazing ridges. For high bunch intensities and the shortest bunch spacings, pressure rises at certain locations in the cryogenic region have been observed during the past two runs. Beam studies are planned for the current 2005 run and the results will be reported.
Work performed under the auspices of the US Department of Energy. |
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| TPAT098 | A Review of TeV Scale Lepton-Hadron and Photon-Hadron Colliders | collider, lepton, linac, hadron | 4329 |
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Funding: Gazi University, Ankara, Turkey. The investigation of lepton-hadron and photon-hadron collisions at TeV scale is crucial both to clarify the strong interaction dynamics from nuclei to quark-parton level and for adequate interpretation of experimental data from future hadron colliders (LHC and VLHC). In this presentation different TeV scale lepton-hadron and photon-hadron collider proposals (such as THERA, "LEP"-LHC, QCD Explorer etc) are discussed. The advantages of linac-ring type colliders has been shown comparatively. |
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| TPAT099 | Main Parameters of ILC-Tevatron Based Lepton-Hadron and Photon-Hadron Colliders | electron, collider, photon, proton | 4335 |
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Funding: Ankara University. The construction of the ILC tangential to Tevatron ring will give opportunity to investigate electron-proton, positron-proton, electron-antiproton, positron-antiproton interactions at 1 TeV center of mass energy. The analysis of the lepton-hadron collisions in these energy region is very important both for understanding of strong interaction dynamics and for adequate interpretation of future LHC and VLHC data. In addition, ILC-Tevatron collider will provide a possibility to realize photon-hadron collisions in the same energy region using Compton backscattered laser photon of ILC electron beam. Main parameters of these colliders are estimated and their physics search potential is briefly discussed. |
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| TPPP003 | Lattice Upgrade Plan for Crab Crossing at the KEKB Rings | lattice, quadrupole, optics, coupling | 865 |
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| We plan to install two superconducting crab cavities into the rings at Janyary, 2006. In our plan, we will install one crab cavity per one ring into the NIKKO straight section where the cryogenic infrastructure is already operated for the superconducting accelerating cavities. In order to obtain the correct crabbing angle at the interaction point(IP), we have to enlarge the horizontal beta function(200m for HER) and have to adjust the horizontal phase advance between the IP and the cavity installation point. In this paper, we will report the lattice modified for the crab crossing and the study results about the single beam dynamics. | |||
| TPPP004 | Study of the Beam-Beam Effect for Crab Crossing in KEKB and Super KEKB | coupling, damping, radiation, simulation | 925 |
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| Luminosity upgrade using crab cavities is planned at KEK-B factory (KEKB)in 2006. The crab crossing is expected to increase the beam-beam parameter >0.1, which is twice of present value, for KEKB. We discuss torelances of crab cavities and lattice to get the high beam-beam parameter. | |||
| TPPP006 | Beam-Beam Simulation Study with Parasitic Crossing Effect at KEKB | simulation, target, damping, beam-beam-effects | 1033 |
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| KEKB is an asymmetric-energy, two-ring, electron-positron collider for B physics. Two beams collide at one interaction point with a finite crossing angle of 22 mrad. The bunch spacing has chosen to be 4 buckets (8 nsec) in most physics run of KEKB. While the shorter bunch spacing is necessary for a higher luminosity, the degradation of the specific luminosity by unknown reason is observed in 4 or 6 nsec spacing. In order to investigate whether parasitic crossing effect degrades a beam-beam performance, we have performed strong-strong beam-beam simulation with parasitic long-range beam-beam force. In this paper we present and discuss our simulation results. | |||
| TPPP007 | Recent Progress at KEKB | vacuum, feedback, beam-losses, injection | 1045 |
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| 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. | |||
| TPPP010 | Photon-Nucleon Collider Based on LHC and CLIC | electron, proton, collider, photon | 1207 |
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| 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. | |||
| TPPP014 | Ionization Cooling Using a Parametric Resonance | emittance, resonance, focusing, betatron | 1374 |
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Funding: This work was supported in part by DOE SBIR grant DE-FG02-04ER84016. Muon collider luminosity depends on the number of muons in the storage ring and on the transverse size of the beams in collision. Ionization cooling as it is presently envisioned will not cool the beam sizes sufficiently well to provide adequate luminosity without large muon intensities. A new idea to combine ionization cooling with parametric resonances has been developed that will lead to beams with much smaller sizes so that high luminosity in a muon collider can be achieved with fewer muons. In the linear channel described here, a half integer resonance is induced such that the normal elliptical motion of particles in x-x' phase space becomes hyperbolic, with particles moving to smaller x and larger x' as they pass down the channel. Thin absorbers placed at the focal points of the channel then cool the angular divergence of the beam by the usual ionization cooling mechanism where each absorber is followed by RF cavities. We discuss the theory of Parametric-resonance Ionization Cooling, including the sensitivity to aberrations and the need to start with a beam that has already been cooled adequately. |
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| TPPP015 | ELIC at CEBAF | electron, ion, collider, emittance | 1437 |
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Funding: Work supported by DOE Contract DE-AC05-84ER40150. We report on the progress of the conceptual development of the energy recovering linac (ERL)-based Electron-Light Ion Collider (ELIC) at CEBAF that is envisioned to reach luminosity level of 1033-1035 /cm2s with both beams polarized to perform a new class of experiments in fundamental nuclear physics. Four interaction points with all light ion species longitudinally or transversally polarized and fast flipping of the spin for all beams are planned. The unusually high luminosity concept is based on the use of the ERL and circulator ring-based electron cooling and crab crossing colliding beams. Our recent studies concentrate on the design of low beta interaction points with crab-crossing colliding beams, the exploration on raising the polarized electron injector current to the level of 3-30 mA with the use of electron circulator-collider ring, forming a concept of stacking and cooling of the ion beams, specifications of the electron cooling facility, and studies of beam-beam interaction and intra-beam scattering. |
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| TPPP017 | Beam-Beam Effects in the Ring-Ring Version of eRHIC | resonance, emittance, beam-beam-effects, simulation | 1520 |
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Funding: The U.S. Department of Energy under Grant No. DE-FG02-04ER41288. The eRHIC is a proposed electron ring at the RHIC that will provide collisions between a polarized 5-10 GeV electron beam and an ion beam from one of the RHIC rings. In order to achieve proposed high luminosity, large bunch current and small beta-functions at the IP has to be employed. Such measures result in large beam-beam parameters, 0.029 and 0.08 for the electron beam and 0.0065 and 0.0033 for the proton beam in the horizontal and vertical plane, respectively, in the current ZDR design. The beam-beam effect especially the coherent beam-beam effect is therefore one of important issues to the eRHIC. Moreover, the proposed configuration of unequal circumferences of the electron and proton rings could further enhance the coherent beam-beam effect. The beam-beam effect of eRHIC has therefore been studied with a self-consistent beam-beam simulation by using the particle-in-cell method. Beam-beam limits of the electron and proton beam were examined as thresholds of the onset of coherent beam-beam instability. For the proposed luminosity, the electron and proton bunch currents optimized with the consideration of the beam-beam effect will be discussed. |
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| TPPP022 | The eRHIC Ring-Ring Collider Design | electron, ion, polarization, proton | 1766 |
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| The eRHIC ring-ring collider is the main design option of the future lepton-ion collider at Brookhaven National Laboratory. We report the revisions of the ring-ring collider design features to the baseline design presented in the eRHIC Zeroth Design Report (ZDR). These revisions have been made during the past year. They include changes of the interaction region which are required from the modifications in the design of the main detector. They also include changes in the lepton storage ring for high current operations as a result of better understandings of beam-beam interaction effects. The updated collider luminosity and beam parameters also take into account a more accurate picture of current and future operational aspects of RHIC. | |||
| TPPP024 | Experimental Study of Crossing-Angle and Parasitic-Crossing Effects at the PEP-II e+e- Collider | simulation, electron, optics, quadrupole | 1874 |
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| In a series of dedicated accelerator experiments, we have measured the dependence of the PEP-II luminosity performance on small horizontal crossing angles and on the horizontal separation at the first parasitic crossing. The experiment was carried out by varying the IP angle of one of the beams in two different bunch patterns, one with and one without parasitic crossings. The experimental measurements show satisfactory agreement with three-dimensional beam-beam simulations. | |||
| TPPP026 | Bunch-Length Measurements in PEP-II | single-bunch, synchrotron, positron, electron | 1934 |
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Funding: Supported by U.S. Department of Energy contract DE-AC03-76SF00515. We measured the lengths of colliding e+e- bunches in the PEP-II B Factory at SLAC using various techniques. First, at several RF voltages and with both single-bunch and multibunch beams, a synchroscan streak camera measured synchrotron emission through a narrow blue filter. With 3.8 MV of RF, the length of a single positron bunch was 12 mm at low current, rising to 13 mm at 1.5 mA and 14.8 mm at 3 mA. The electrons measured 12.2 mm with little current dependence. Both are longer than the expected low-current value of 10 mm (e+) and 11 mm (e-), derived from the energy spread and the measured synchrotron tune. We also determined the length from measurements between 2 and 13 GHz of the bunch spectrum on a BPM button. After correcting for the frequency dependence of cable attenuation, we then fit the measured spectrum to that of a Gaussian bunch. With 3.8 MV, the positrons measurement gave 13.2 mm at 1.5 mA/bunch in a full ring, in agreement with the streak camera, but we found 11.4 mm for the electrons at 16.7 MV and 1 mA/bunch, lower than the streak measurement. |
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| TPPP027 | Single-Bunch Tune and Beam Size Measurements Along Bunch Trains in PEP-II | single-bunch, electron, positron, feedback | 2006 |
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| By scanning a gated camera and a gated tune monitor across the bunch pattern during normal colliding-bunch operation of PEP-II, the single-bunch tunes and beam sizes were measured simultaneously in the high and low energy storage rings of PEP-II. The measurements were made with 1561 colliding bunches in PEP-II, arranged in trains of 66 bunches, with each bunch in the train separated by 4.2 ns. The tune and beam size measurements were correlated with the current, luminosity, and specific luminosity of the bunch. The results show a vertical tune shift at the start and end of the mini-trains, a luminosity droop along the mini-train, and specific luminosity drop in the first and last bunches of the train, since they experience a different parasitic crossing on either side of the IP. | |||
| TPPP029 | A Preliminary Interaction Region Design for a Super B-Factory | background, radiation, interaction-region, synchrotron | 2077 |
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Funding: work supportted by the Department of Energy under contract number DE-AC03-76SF00515. The success of the two B-Factories (PEP-II and KEKB) has encouraged us to look at design parameters for a B-Factory with a 30-50 times increase in the luminosity of the present machines (L~1e36). In order to achieve this high luminosity, the beta y* values are reduced to 3-2 mm, the bunch spacing is minimized (0.6-0.3 m) and the bunch currents are increased. Total beam currents range from 5-25 A. The interaction region (IR) of these "SuperB" designs presents special challenges. Synchrotron radiation fans from local bending in shared magnets and from upstream sources pose difficulties due to the high power levels in these fans. High-order-mode(HOM)heating, effects that have been seen in the present B-factories, will become much more pronounced with the very short bunches and high beam currents. Masking the detector beam pipe from synchrotron radiation must take into account effects of HOM power generation. Backgrounds that are a function of the luminosity will become very important. We present an initial design of an IR with a crossing angle of ± 14 mrad and include a discussion of the constraints, requirements and concerns that go into designing an IR for these very high luminosity e+e- machines. |
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| TPPP034 | Parameters of a Super-B-Factory Design | interaction-region, factory, collider, linac | 2333 |
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Funding: Work supported by DOE contract DE-AC02-76SF00515. Submitted for the High Luminosity Study Group: Parameters are being studied for a high luminosity e+e- collider operating at the Upsilon 4S that would deliver a luminosity in the range of 7 to 10 x 1035/cm2/s. Particle physics studies dictate that a much higher luminosity collider is needed to answer new key physics questions. A Super-B-Factory with 20 to 100 times the performance of the present PEP-II accelerator would incorporate a higher frequency RF system, lower impedance vacuum chambers, higher power synchrotron radiation absorbers, and stronger bunch-by-bunch feedback systems. Parameter optimizations are discussed. |
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| TPPP035 | Performance of the PEP-II B-Factory Collider at SLAC | injection, beam-beam-effects, electron, positron | 2369 |
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Funding: Work supported by DOE contract DE-AC02-76SF00515. For the PEP-II Operation Staff: PEP-II is an asymmetric e+e- collider operating at the Upsilon 4S and has recently set several performance records. The luminosity has reached 9.2 x 1033/cm2/s. PEP-II has delivered an integrated luminosity of 710/pb in one day. It operates in continuous injection mode for both beams boosting the integrated luminosity. The peak positron current has reached 2.55 A in 1588 bunches. The total integrated luminosity since turn on in 1999 has reached 256/fb. This paper reviews the present performance issues of PEP-II and also the planned increase of luminosity in the near future to over 2 x 1034/cm2/s. Upgrade details and plans are discussed. |
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| TPPP043 | ERL Based Electron-Ion Collider eRHIC | electron, proton, ion, collider | 2768 |
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Funding: Work performed under Contract Number DE-AC02-98CH10886 with the auspices of the US Department of Energy.
We present the designs of a future polarized electron-hadron collider, eRHIC* based on a high current super-conducting energy-recovery linac (ERL) with energy of electrons up to 20 GeV. We plan to operate eRHIC in both dedicated (electron-hadrons only) and parallel(with the main hadron-hadron collisions) modes. The eRHIC has very large tunability range of c.m. energies while maintaining very high luminosity up to 1034 cm-2 s-1 per nucleon. Two of the most attractive features of this scheme are full spin transparency of the ERL at all operational energies and the capability to support up to four interaction points. We present two main layouts of the eRHIC, the expected beam and luminosity parameter, and discuss the potential limitation of its performance.
*http://www.agsrhichome.bnl.gov/eRHIC/, Appendix A: Linac-Ring Option. |
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| TPPP049 | eRHIC Detector Design Studies - Implications and Constraints on the ep(A) Interaction-Region Design | electron, interaction-region, proton, scattering | 3043 |
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| An electron-proton/ion collider facility (eRHIC) is under consideration at Brookhaven National Laboratory. This high energy, high intensity polarized electron/positron beam facility to collide with the existing RHIC heavy ion and polarized proton beam would significantly enhance the exploration of fundamental aspects of Quantum Chromodynamics (QCD), the underlying quantum field theory of strong interactions. The design of a new optimized detector is closely coupled to the design of the interaction region and thus to the machine development work in general. A GEANT-based detector simulation framework has been developed to study various processes at eRHIC taking into consideration the impact of machine elements inside the detector volume and the synchrotron radiation fan generated by the electron/positron beam. The GEANT-based detector simulation framework called ELECTRA will be presented followed by a discussion of constraints and implications on the interaction region design. | |||
| TPPT010 | HOM Damping of ARES Cavity System for SuperKEKB | coupling, klystron, dipole, damping | 1186 |
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| The ARES cavity scheme is a decisive edge for KEKB to stably accelerate high-current electron and positron beams. The RF structure is a coupled-cavity system where a HOM-damped accelerating cavity is coupled with a large cylindrical energy storage cavity via a coupling cavity between. The HOM-damped structure is designed to be smoothly embedded into the whole coupled-cavity scheme without any structural or electromagnetic incompatibility. Currently, the total HOM power dissipated in the RF absorbers per cavity is about 5 kW according to calorimetric measurements in the KEKB LER with a beam current of 1.6 A. On the other hand, for SuperKEKB aiming at luminosity frontiers over 1035 cm-2 s-1, the total HOM power per cavity is estimated about 100 kW for the LER with the design beam current of 9.4 A. In this article, a new HOM-damped structure of the ARES cavity system designed for the SuperKEKB LER is reported together with the recent activities and future plans for upgrading the HOM absorbers. | |||
| TPPT011 | R&D Status of C-Band Accelerating Section for SuperKEKB | linac, positron, klystron, coupling | 1233 |
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| For future energy upgrade of the KEKB injector linac, C-band accelerating section has been developed. First prototype 1-m long section has been installed in the linac and has achieved the accelerating field gradient of 42 MV/m. Developments of second prototype which has thicker coupler iris and third prototype which has smooth surface of the iris are in progress for less frequent breakdown. This paper reports on the recent R and D status of these C-band accelerating sections. | |||
| TOPE004 | CLIC Progress Towards Multi-TeV Linear Colliders | linac, damping, collider, emittance | 353 |
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| Novel parameters of an e+/e- Linear Collider based on CLIC technology with a broad colliding energy range from 0.5 to 5 TeV are presented for an optimised luminosity of 8x1034 cm-2s-1 at the nominal energy of 3 TeV. They are derived in part from the very successful tests and experience accumulated in the CLIC Test facility, CTF2. A new and ambitious test facility, CTF3, presently under construction at CERN within an international collaboration of laboratories and institutes, and aimed at demonstrating the key feasibility issues of the CLIC scheme, is described. | |||
| TOPD002 | BEPCII -The Second Phase Construction of the Beijing Electron-Positron Collider | positron, electron, vacuum, linac | 131 |
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The Beijing Electron-Positron Collider (BEPC) was constructed for both high energy physics and synchrotron radiation researches. The peak luminosity of the BEPC has reached its design goal of 5*1030 cm-2s-1 at J/sai energy of 1.55 GeV and 1*1031 cm-2s-1 at 2 GeV respectively. As the second phase construction of the BEPC, the BEPCII has been approved with total budget of 640 million RMB. The construction was started in the beginning of 2004 and is scheduled to be completed by the end of 2007. The BEPCII is a double ring machine with its luminosity goal of 1*1033 cm-2s-1 at 1.89 GeV, two orders of magnitude higher than present BEPC. The upgrading of the collider should also provide an improved SR performance with higher beam energy and intensity. The beam currents will be increased to 250 mA at E=2.5 GeV for the dedicated synchrotron radiation operation of the BEPCII. Some key technologies, such as superconducting RF system, low impedance vacuum devices, superconducting micro-beta quadrupoles and etc., are being developed in order to achieve the target of the BEPCII.*
*Submitted on behalf of the BEPCII Team. |
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| WOAA002 | Progress and Plans for R&D and the Conceptual Design of the ILC Main Linacs | linac, klystron, coupling, collider | 199 |
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| The International Linear Collider Main Linacs are based on superconducting accelerator structures operating at 1.3 GHz. The basis for this design has been developed and tested at DESY and R&D is progressing at many laboratories around the world including DESY, Orsay, KEK, FNAL, SLAC, Cornell, and JLAB. The status of the TESLA-style cavities and rf system will be reviewed and parameters for the ILC linac will be described. The role of the different linac test facilities will discussed and the critical items and R&D program to support a Conceptual Design and Technical Design will be outlined. | |||
| WPAE030 | Thermal Analysis of the Al Window for a New CESR-c Luminosity Monitor | photon, positron, vacuum, simulation | 2137 |
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Funding: Work supported by the U.S. National Science Foundation. A luminosity monitor using photons from radiative bhabha events at the CLEO interaction point (IP) has been installed in the Cornell Electron Storage Ring (CESR). A key vacuum and detector component is the photon window/converter whose uniformity and thickness are critical for determining the resolution of the total energy deposited in the segmented luminosity monitor. The window design must accommodate the operational requirements of the new monitor at CLEO-c beam energies of 1.5-2.5 GeV and also provide sufficient safety margin for operation at 5.3 GeV beam energies for Cornell High Energy Synchrotron Source (CHESS) running. During 5.3 GeV operation, intense stripes of synchrotron radiation from the interaction region superconducting quadrupole magnets as well as nearby bending magnets strike the window. During the course of window development, several materials and designs were evaluated. Thermal stresses were calculated using the finite element code ANSYS for various beam conditions to guide the cooling design. A window using aluminum alloy (6061-T6) was ultimately chosen to provide optimal performance for both CLEO-c and CHESS running conditions. The window has been in successful operation since September 2004. |
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| WPAE056 | Geant4-Based Simulation Study of PEP-II Beam Backgrounds in the BaBar Detector at the SLAC B-Factory | vacuum, simulation, scattering, background | 3351 |
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| To improve the understanding of accelerator-induced backgrounds at the SLAC B-Factory and validate the proposed PEP-II luminosity upgrade, we simulate lost-particle backgrounds in the BaBar detector originating from beam-gas interactions and radiative-Bhabha scatters. To perform this study, we have extended the GEANT4-based BaBar detector simulation to include PEP-II beam-line components and magnetic fields up to 10m away from the interaction point. We first describe the simulation model and then compare predicted background levels with measurements from dedicated single-and colliding-beam experiments. Finally, we compare the simulated background levels in the current and the proposed luminosity-upgrade configurations. | |||
| WPAE079 | Dual Power Supplies for PEP-II Injection Kickers | kicker, injection, power-supply, background | 4045 |
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Funding: Work supported by Department of Energy contract DE-AC03-76SF00515. Originally the PEP-II injection kickers where powered by one power supply. Since the kicker magnets where not perfectly matched, the stored beam got excited by about 7% of the maximum kicker amplitude. This led to luminosity losses which were especially obvious for trickle injection when the detector is on for data taking. Therefore two independant power supplies with thyratrons in the tunnel next to the kicker magnet were installed. This also reduces the necessary power by about a factor of five since there are no long cables that have to be charged. The kickers are now independantly adjustable to eliminate any non-closure of the kicker system and therefore excitation of the stored beam. Setup, commissioning and fine tuning of this system are discussed. |
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| WPAT038 | Instability of the RF Control Loop in the Presence of a High-Q Passive Superconducting Cavity | feedback, resonance, simulation, superconducting-RF | 2553 |
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Funding: Work is supported by the National Science Foundation. An instability of the active RF cavity field control loop was observed during experiments with beam-driven (passive) superconducting cavities in CESR when the cavity external Q factor was raised to a value above 1x107. A computer model was developed and further experiments have been performed to study this instability and find a way to cure it. The results of simulations are presented alongside the experimental results. |
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| WOAB005 | The Status of Turkic Accelerator Complex Proposal | factory, linac, proton, electron | 449 |
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| Recently, the Turkic Accelerator Complex (TAC) is proposed as a regional facility for accelerator based fundamental and applied research. The complex will include linac on ring type electron-positron collider as a phi, charm and tau factory, linac based free electron laser (FEL), ring based third generation syncrothron radiation (SR) source and a few GeV proton accelerator. Preliminary estimations show that hundred inverse femto barn integral luminosity per year can be achieved for factory options. The FEL facility is planned to obtain laser beam between IR and soft X-ray region. In addition, SR facility will produce photon beams in UV and X-ray region. The proton accelerator will give opportunity to produce muon and neutron beams for applied research. The current status of the conceptual study of the complex is presented. | |||
| WOAD001 | Super-B Factories | background, factory, lattice, vacuum | 64 |
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| Energy-asymmetric electron-positron B factories, KEKB and PEP-II, have been operated at the luminosity frontiers and have delivered the integrated luminosities of a few hundreds of /fb to experiments. For further progress in particle physics, a luminosity of higher than 100/nb/s is strongly required, which means higher beam currents, smaller beta functions at the interaction point, larger beam-beam parameters, shorter bunch lengths, etc. This paper will review major upgrade plans of both machines toward SuperKEKB and Super PEP-II. | |||
| WOAD002 | Lepton Collider Operation with Constant Currents | injection, background, collimation, linac | 149 |
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Funding: Work supported by US DOE under contract DE-AC03-76SF00515 Traditionally, electron-positron colliders have been operating in a top-off-and-coast fashion with a cycle time depending on the beam life time, typically on the order of an hour. Each top-off involves ramping detector systems in addition to the actual filling time. The loss in accumulated luminosity is typically 20-50%. During the last year, both B-Factories have commissioned a continuous-injection mode of operation in which beam is injected without ramping the detector, thus raising luminosity integration by constant operation at peak luminosity. Constant beam currents reduce thermal drift and trips caused by change in beam loading. To achieve this level of operation, special efforts were made to reduce the injection losses and also to implement special gating procedures in the detectors, minimizing dead time. Bunch-injection control decides which bunch to inject into next while maintaining small charge variation between bunches. Beam collimation can reduce injection noise but also cause an increase in background rates. A challenge can be determining beam lifetime, important to maintain tuning of the beams. The paper will discuss the special features of continuous injection in both KEKB and PEP-II. |
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| ROAA001 | DAFNE Operation and Plans for DAFNE2 | injection, factory, damping, coupling | 112 |
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| The e+e- collider DAFNE, a 1.02 Gev c.m. Phi-factory, has exceeded 1.2 1032 cm-2s-1 peak luminosity with 7.5 pb-1 maximum daily integrated luminosity. At the present performance the physics program of the three main experiments DEAR, FINUDA and KLOE will be completed by mid 2007. In this paper we describe the steps which have led to the luminosity improvement and present proposals for the upgrade of the collider towards higher energy and/or luminosity. The main accelerator issues on which we are planning to rely for this purpose, such as lattices with negative momentum compaction, strong RF focusing, design of high field magnets and Linac upgrade, are discussed in detail. | |||
| ROAA002 | CESR-c: Performance of a Wiggler-Dominated Storage Ring | wiggler, resonance, sextupole, betatron | 189 |
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Funding: Work supported by the U.S. National Science Foundation. CESR-c operates now as a Wiggler-Dominated Storage Ring extending the lowest operating energy to 1.5GeV/beam. To improve beam stability at low energy, 12 super-ferric wiggler magnets with total length of 15m and 2.1T maximum field were installed in the ring. They cause ~90% of total beam radiation lost and increase radiation damping rate by factor 10 from ~3 to 40 Hz. However, the field of the wiggler magnets not only initiates the radiation, but potentially affects beam dynamics. The latter was an issue of a great concern from the planning the CESR-c project. In this paper we describe general performance of CESR-c and report the results of an experimental study on some aspects of beam dynamics. Comparisons are made between the experimental data and the model prediction. We find that all parameters, which are critically dependent on wigglers, such as beam properties and ring nonlinearity, are in good agreement with those calculated from the model. This validates the ring and wiggler models and justifies our design and production technique of the magnets. The experience we obtained will be extremely useful in future work on linear collider damping rings. |
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| ROAA003 | Proposal of an Experiment on Bunch Length Modulation in DAFNE | synchrotron, dynamic-aperture, storage-ring, factory | 336 |
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| Obtaining very short bunches is a challenge for colliders and Coherent Synchrotron Radiation sources as well. The modulation of the bunch length in a strong RF focusing regime has been proposed, corresponding to a large value of the synchrotron tune. A ring structure where the dependence of the longitudinal position of a particle on its energy (R56) along the ring oscillates between large positive and negative values can produce a bunch length modulation. The synchrotron frequency can be tuned both by means of the rf voltage and by the integral of R56, down to the limit of zero value corresponding to the isochronicity condition. We present here the proposal of bunch length modulation along the DAFNE rings. Its lattice can be tuned to positive or negative momentum compaction, or to structures in which the two arcs are alternately set to positive/negative integrals of R56. With the proposed installation of an extra RF system at 1.3 GHz, experiments on bunch length modulation both in the high and low synchrotron tune regimes can be realized. | |||
| RPAT052 | Vertical Beam Size Measurement by Streak Camera under Colliding and Single Beam Conditions in KEKB | electron, beam-beam-effects, positron, feedback | 3194 |
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| Beam behavior of KEKB was studied by measurement of the beam size using a streak camera. Effect of the electron-cloud and the parasitic collision on the vertical beam size was examined in beam collision. We intentionally injected a test bunch of positrons after 2 rf buckets of a bunch to enhance the electron cloud effect and changed electron beam conditions to see the beam-beam effect. The beam size was also measured with a single positron beam and compared with that during collision. The result of the measurement is reported in this paper. | |||
| RPAT053 | Movement of BPMs Due to Thermal Stress in KEKB | pick-up, sextupole, radiation, synchrotron | 3253 |
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| Movement of Beam Position Monitors (BPM) due to thermal stress in high beam current operation is observed in KEKB. For high luminosity operation of KEKB, the beam current as high as 1.6A is accumulated in the positron ring and a precise control of the beam orbit based on the BPM system is required. Though the every BPM chamber is fixed firmly on a support of each quadrupole magnet, the BPM chamber moves several hundred microns from the setting position depending on the beam current due to beam pipe heating by strong synchrotron light irradiation. Such movement introduces an unavoidable offset error in the BPM measurement, and is a serious problem not only for KEKB but also for the next generation of B-factory operated with extremely high beam current. We report the measurement of the movement by distance sensors and an attempt to correct the BPM offset error in real-time operation. | |||
| RPAT062 | Design and Operation of a Radiative Bhabha Luminosity Monitor for CESR-c | photon, vacuum, monitoring, positron | 3564 |
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Funding: Work supported by the National Science Foundation. The CLEO-c experiment at the Cornell Electron Storage Ring (CESR) is presently embarking on a multi-year exploration of charm and QCD physics in the 3-5 GeV center-of-mass energy range. In order to facilitate rapid optimization of machine parameters over this energy range, a luminosity monitor based on the measurement of radiative-bhabha photons coming from the CLEO-c interaction point (IP) has been designed and installed in the CESR ring. Key design criteria of the device include: better than 1% statistical measurements of the luminosity with a 1 Hz update rate over the full range of CESR-c operating conditions; bunch-by-bunch measurement capability; a large horizontal aperture to enable measurements under conditions ranging from single-bunch head-on collisions to multi-bunch collisions with a horizontal crossing angle of up to 4~mrad; and, a segmented readout to provide direct information on beam characteristics at the IP. We review the design and performance of this device and discuss its application to machine tuning and performance studies. |
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| RPAT063 | A Bunch-By-Bunch and Turn-By-Turn Instrumentation Hardware Upgrade for CESR-c | electron, positron, synchrotron, instrumentation | 3597 |
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Funding: Work supported by the National Science Foundation. A key factor in the colliding beam performance of the Cornell Electron Storage Ring (CESR) is the impact of parasitic beam-beam interactions between bunches in the two beams as they follow their electrostatically separated orbits in a single vacuum chamber. In order to better investigate the differential performance of bunches in CESR, instrumentation electronics has been developed to allow acquisition of turn-by-turn data from multiple bunches simultaneously. The electronics consists of a standardized digital board centered around an Analog Devices TigerSHARC family digital signal processor, a communications interface, and an interface to the CESR Precision Timing System. Mated to these components is an analog front end and digitizer board which is customized for the particular diagnostic device of interest. Front ends have been developed for beam position monitor, luminosity monitor, and beam profile monitor applications. We describe the design and characterization of this new hardware. |
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| ROPB009 | Betatron Sidebands Due to Electron Clouds Under Colliding Beam Conditions | electron, betatron, positron, feedback | 680 |
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| Recently, we have observed vertical betatron sidebands in the transverse beam spectra of positron bunches at the KEKB LER which are associated with the presence of electron clouds. When the LER is operating in single-beam mode (no colliding bunches in the HER), these sidebands are sharply peaked. When the bunches are in collision for physics running, the sidebands are still present but are found to be smeared out. The bunch-by-bunch specific luminosity is lower for bunches with sidebands than for those without sidebands. In this paper, the behavior of the sidebands in collision and the effects on luminosity are discussed. | |||
| RPPE005 | Ions for LHC: Beam Physics and Engineering Challenges | ion, electron, injection, linac | 946 |
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| The first phase of the heavy ion physics program at the LHC aims to provide lead-lead collisions at energies of 5.5 TeV per colliding nucleon pair and ion-ion luminosity of 1027 cm-2s-1. The transformation of CERN’s ion injector complex (Linac3-LEIR-PS-SPS) presents a number of beam physics and engineering challenges. Conversion of the Low Energy Antiproton Ring (LEAR) to a Low Energy Ion Ring (LEIR) is under way: the high-current electron cooling system, novel broad-band RF cavities and vacuum equipment to achieve 10-12 mbar are the major challenges. Commissioning of LEIR with beam will start in the middle of 2005. Major hardware changes in Linac3 include the installation of the new ECR ion source and of the energy ramping cavity. The PS will have a new injection system and RF gymnastics. A stripping insertion between PS and SPS must not disturb the proton operation. In the LHC itself, there are fundamental performance limitations due to various beam loss mechanisms. To study these without risk of damage there will be an initial period of operation with a reduced number of nominal intensity bunches. While reducing the work required to commission the LHC with ions in 2008, this will still enable early physics discoveries. | |||
| RPPE044 | Vacuum Modifications for the Installation of a New CESR-c Fast Luminosity Monitor | vacuum, dipole, photon, synchrotron | 2836 |
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Funding: Work supported by the National Science Foundation. In order to improve luminosity tuning and maintenance for the CLEO-c high energy physics (HEP) program at the Cornell Electron Storage Ring (CESR), a luminosity monitor using photons from radiative Bhabha events has been installed in the CESR ring. Over 10 meters of CESR vacuum chambers near the interaction region were modified to accommodate this new device. The vacuum modifications were designed to meet two criteria. First, the new vacuum chambers had to provide sufficient horizontal and vertical aperture for photons originating from the IP over a wide range of colliding beam conditions. Secondly, the new vacuum chambers required adequate safety margins for operation at beam energies up to 5.3 GeV for Cornell High Energy Synchrotron Source running. In order to be certain that the vacuum modifications would not give rise to any localized pressure bumps, a detailed calculation of the expected vacuum pressure distribution due to synchrotron radiation flux was carried out. Careful design and planning enabled a successful installation and resumption of CESR operations in record time. |
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| RPPE047 | Upgrade of RHIC Vacuum Systems for High Luminosity Operation | vacuum, ion, electron, injection | 2977 |
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Funding: Work performed under Contract Number DE-AC02-98CH10886 with the auspices of the U.S. Department of Energy. With increasing ion beam intensity during recent RHIC operations, pressure rises of several decades were observed at most room temperature sections and at a few cold sections. The pressure rises are associated with electron multi-pacting, electron stimulated desorption and beam ion induced desorption and have been one of the major intensity and luminosity limiting factors for RHIC. Improvement of the warm sections has been carried out in the last few years. Extensive in-situ bakes, additional UHV pumping, anti-grazing ridges and beam tube solenoids have been implemented. Several hundred meters of NEG coated beam pipes have been installed and activated. Vacuum monitoring and interlock were enhanced to reduce premature beam aborts. Preliminary measures, such as pumping before cool down to reduce monolayer condensates, were also taken to suppress the pressure rises in the cold sections. The effectiveness of these measures in reducing the pressure rises during machine studies and during physics runs are discussed and summarized. |
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| RPPE050 | Development of NEG Coating for RHIC Experimental Beamtubes | cathode, vacuum, electron, ion | 3120 |
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Funding: Work performed under Contract No. DE-AC02-98CH10886 under the auspices of the U.S. Department of Energy. As RHIC beam intensity increases beyond original scope, pressure rises in some regions have been observed. The luminosity limiting pressure rises are associated with electron multi-pacting, electron stimulated desorption and beam induced desorption. Non-Evaporable Getter (NEG) coated beampipes have been proven effective to suppress pressure rise in synchrotron radiation facilities. Standard beampipes have been NEG coated by a vendor and added to many RHIC UHV regions. BNL is developing a cylindrical magnetron sputtering system to NEG coat special beryllium beampipes installed in RHIC experimental regions. It features a hollow, liquid cooled cathode producing power density of 500W/m and deposition rate of 5000 Angstrom/hr on 7.5cm OD beampipe. The cathode, a titanium tube partially covered with zirconium and vanadium ribbons, is oriented for horizontal coating of 4m long chambers. Ribbons and magnets are arranged to provide uniform sputtering distribution and deposited NEG composition. Vacuum performance of NEG coated pipes was measured. Coating analysis includes energy dispersive spectroscopy, auger electron spectroscopy and scanning electron microscopy. System design, development, and analysis results are presented. |
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| RPPP009 | Luminosity Tuning Bumps in the CLIC Main Linac | emittance, simulation, linac, quadrupole | 1141 |
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Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395). Preservation of beam emittance in the CLIC main linac is a challenging task. This requires not only beam-based alignment of the beam line components but also the use of emittance tuning bumps. In this paper the potential use of luminosity tuning bumps is explored and compared to emittance tuning bumps. |
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| RPPP014 | Multi-Bunch Simulations of the ILC for Luminosity Performance Studies | simulation, feedback, ground-motion, linac | 1368 |
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Funding: This work is supported by the Commission of the European Communities under the 6th Framework Programme "Structuring the European Research Area", contract number RIDS-011899. To study the luminosity performance of the International Linear Collider (ILC) with different design parameters, a simulation was constructed that tracks a multi-bunch representation of the beam from the Damping Ring extraction through to the Interaction Point. The simulation code PLACET is used to simulate the LINAC, MatMerlin is used to track through the Beam Delivery System and GUINEA-PIG for the beam-beam interaction. Included in the simulation are ground motion and wakefield effects, intra-train fast feedback and luminosity-based feedback systems. To efficiently study multiple parameters/multiple seeds, the simulation is deployed on the Queen Mary High-Throughput computing cluster at Queen Mary, University of London, where 100 simultaneous simulation seeds can be run. |
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| RPPP015 | Reconstruction of IP Beam Parameters at the ILC from Beamstraahlung | photon, simulation, radiation, electron | 1446 |
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Funding: This work is supported by the Commission of the European Communities under the 6th Framework Programme "Structuring the European Research Area", contract number RIDS-011899. The luminosity performance of the ILC will be very sensitive to the parameters of the colliding bunches. Only some of these parameters can be measured using planned instrumentation. This analysis aims to access some of the colliding beam parameters not available by other means and to improve on the resolution of those that are. GUINEA-PIG is used to simulate the beam-beam interactions and produce beamstrahlung radiation (e+/e- pairs and photons). These are tracked to a simulation of the low-angle Beam Calorimeter and a photon detector and event shapes are produced. A Taylor map is produced to transform from the event shapes to the simulated beam parameters. This paper reports on the progress of this analysis, examining the usefulness of the proposed fitting technique. |
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| RPPP019 | Revisiting the Cold ILC Parameters | damping, linac, collider, feedback | 1661 |
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| At the first ILC Workshop, discussions were underway to re-examine the parameters of the cold ILC. Using the TESLA parameters MathCad program developed in 1991, I examined several variations to explore consequences to the capital and operating costs of the linac (cryomodules, RF, & refrigerator). The cost coefficients were chosen to match the distribution of the above items in the TESLA TDR at 25 MV/m. One parameter varied is the gradient from 25 to 50 MV/m coupled with a realistic Q as well as an optimistic Q (1010). Other parameters varied are: number of bunches, spacing, and rep rate to decrease the damping ring size. Keeping all other TDR parameters the same, the optimal gradient for the realistic Q curve is about 35 MV/m, yielding a capital cost savings of 16% and a total cost savings of 9% over the nominal gradient of 25 MV/m. If however the Q remains at 1010, the optimum gradient moves to 50 MV/m where the total cost savings rise to 17.5%, and capital cost savings rise to 35%. Of course, gradients higher than 35 MV/m are extremely challenging, demanding major development efforts, such as control of Lorentz force detuning which increases as the square of the gradient. | |||
| RPPP021 | Multivariate Optimization of ILC Parameters | linac, collider, emittance, linear-collider | 1736 |
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Funding: This work is supported by the NSF. We present results of multiobjective optimization of the International Linear Collider (ILC) which seeks to maximize luminosity at each given total cost of the linac (capital and operating costs of cryomodules, refrigeration and RF). Evolutionary algorithms allow quick exploration of optimal sets of parameters in a complicated system such as ILC in the presence of realistic constraints as well as investigation of various what-if scenarios in potential performance. Among the parameters we varied there were accelerating gradient and Q of the cavities (in a coupled manner following a realistic Q vs. E curve), the number of particles per bunch, the bunch length, number of bunches in the train, etc. We find an optimum which decreases (relative to TDR baseline) the total linac cost by 22 %, capital cost by 25 % at the same luminosity of 3·1038 1/m2/s. For this optimum the gradient is 35 MV/m, the final spot size is 3.6 nm, and the beam power is 15.9 MW. Dropping the luminosity to 2·1038 1/m2/s results in an additional 8 % reduction in the total linac cost. We have also explored the optimal fronts of luminosity vs. cost for several other scenarios using the same approach. |
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| RPPP030 | Design of ILC Extraction Line for 20 mrad Crossing Angle | extraction, diagnostics, optics, beam-losses | 2134 |
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Funding: Work supported by the Department of Energy Contract DE-AC02-76SF00515. One of the two ILC Interaction Regions will have a large horizontal crossing angle which would allow to extract the spent beams in a separate beam line. In this paper, the extraction line design for 20 mrad crossing angle is presented. This beam line transports the primary e+/e- and beamstrahlung photon beams from the IP to a common dump, and includes diagnostic section for energy and polarization measurements. The optics is designed for a large energy acceptance to minimize losses in the low energy tail of the disrupted beam. The extraction optics, diagnostic instrumentation and particle tracking simulations are described. |
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| FOAC001 | High Intensity Muon Beam Facilities with FFAG | betatron, proton, factory, simulation | 29 |
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| A new highly intense muon source with narrow beam energy spread and high purity, based on a FFAG ring, is under development in Japan. It is called the PRISM project, which stands for Phase Rotated Intense Slow Muon source. The aimed beam intensity is about 1011-1012 muons per year, which is about 1000 or 1000 times that presently available. The muon beam energy is low, of 20 MeV in kinetic energy, for stopped muon experiments. In particular, high luminosity would be important, and narrow beam spread can be achieved by phase (bunch) rotation in the FFAG ring. It is expected to compress the beam energy spread from about 30% down to about 3 %. At Osaka university, the PRISM-FFAG ring is now under construction. The special requirements for the PRISM-FFAG ring, compared to other FFAG rings so far developed, is to have large acceptance dedicated for a muon beam, and high-gradient RF to complete phase rotation within a muon lifetime. In this presentation the present designs of PRISM and status of construction will be presented. | |||
| FPAE017 | Observation of Longitudinal Diffusion and Cooling Due to Intrabeam Scattering at the Fermilab Recycler Ring | emittance, antiproton, scattering, proton | 1560 |
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| The Fermilab Recycler Ring is a high vacuum fixed energy antiproton storage ring with both stochastic and electron cooling systems. In this note the technique for diffusion rate measurement, beam parameters and the analysis of data are presented, as well as the effect of intrabeam scattering on the operational considerations for the storage and cooling of the antiproton beam in the Recycler. | |||
| FPAP017 | Luminosity Optimization With Offset, Crossing Angle, and Distortion | electron, positron, linear-collider, simulation | 1541 |
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Funding: Work is supported by the U.S. Department of Energy under contract DE-AC02-76SF00515. In a linear collider, sources of beam jitter due to kicker noise, quadrupole vibration and long-range transverse wakefields will lead to beam offsets and tilts at the Intersection Point (IP). In addition, sources of emittance dilution such as short-range transverse wakefields or dispersive errors will lead to internal beam distortions. When the IP disruption parameter is large, these beam imperfections will be amplified by a single bunch kink instability which will lead to luminosity loss. In this paper, we study the luminosity loss and then the optimization required to cancel the luminosity loss first analytically and then with simulation. |
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| FPAP018 | Luminosity Loss Due to Beam Distortion and the Beam-Beam Instability | resonance, simulation, emittance, electron | 1586 |
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Funding: Work is supported by the U.S. Department of Energy under contract DE-AC02-76SF00515. In a linear collider, sources of emittance dilution such as transverse wakefields or dispersive errors will couple the vertical phase space to the longitudinal position within the beam (the so-called ‘banana effect'). When the Intersection Point (IP) disruption parameter is large, these beam distortions will be amplified by a single bunch kink instability which will lead to luminosity loss. We study this phenomena both analytically using linear theory and via numerical simulation. In particular, we examine the dependence of the luminosity loss on the wavelength of the beam distortions and the disruption parameter. This analysis may prove useful when optimizing the vertical disruption parameter for luminosity operation with given beam distortions. |
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| FPAT003 | Joining the RHIC Online and Offline Models | simulation, lattice, optics, insertion | 880 |
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Funding: Work performed under the auspices of the U.S. Department of Energy. The paper presents an interface encompassing the RHIC online ramp model and the UAL offline simulation framework. The resulting consolidated facility aims to minimize the gap between design and operational data, and to facilitate analysis of RHIC performance and future upgrades in an operational context. The interface is based on the Accelerator Description Exchange Format (ADXF), and represents a snapshot of the RHIC online model which is in turn driven by machine setpoints. This approach is also considered as an intermediate step towards integrating the AGS and RHIC modeling environments to produce a unified online and offline AGS model for operations. |
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| FOAA003 | HOM Effects in Vacuum System with Short Bunches | vacuum, resonance, positron, synchrotron | 289 |
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Funding: Work supported by Department of Energy contract DE–AC02–76SF00515. High luminosity in electron-positron factories requires high beam currents of very short bunches. SLAC PEP-II and KEKB B-factories are progressively increasing currents and gaining more and more luminosity. Because of this the interaction of high currents and vacuum chamber elements becomes more important for the operation of the rings. High Order Modes (HOM) excited by short intense bunches propagate along the vacuum chamber, penetrating and dissipating inside vital vacuum elements like shielded bellows, vacuum valves and vacuum pumps. As a result these elements can heat up or have temperature oscillations. Often HOM heating has a resonance character. HOM heating of vacuum pumps can lead to vacuum pressure increases. High frequency modes excited by short bunches “check” the quality of the vacuum chamber by detecting small gaps, weak RF screens or weak feed-through. At these high currents even smooth tapers and smooth collimators become a source of HOM production. We will discuss the physical nature of these very interesting HOM effects. |
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