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MOXPA01 | The Global Design Initiative for an International Linear Collider | collider, linear-collider, electron, proton | 1 | ||||
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Two years after the selection of the SC technology and a few months before the release of the ILC Conceptual Design Report, the presentation will review the main issues towards an ILC project and the world-wide collaboration presently set-up to address them. It will especially emphasize the challenges both technical (performances, reliability, machine protection, cost minimisation, industrialisation) and organisational, in a world-wide collaboration for the first time from the very beginning of the project. It will then present the status of the performances already demonstrated, the R&D presently envisaged to improve them or reduce the cost, the test facilities set-up to address them and the effort towards technology transfer to industry and industrialisation. Finally, it will present the plans and schedule for the future as well as the site specific parameters and cost issues.
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Transparencies
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MOPCH160 | A Beam-based High Resolution Phase Imbalance Measurement Method for the ILC Crab Cavities | dipole, linear-collider, single-bunch, electron | 433 | ||||
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A high resolution method of RF phase adjustment and test is proposed for the Crab Cavity system of the ILC. The method is based on beam as ultimate test instrument. To measure phase imbalance in the pair of crab cavities (<0.02deg at 1.3GHz is required), a low energy (~1GeV) beam is used. A bunch center-of-mass trajectory through the cavities spaced (n+1/2) RF wavelengths and excited as in the case of the ILC, is a straight line for phase-balanced cavities and gets a kick when unbalanced. The kick is measured by two spaced BPMs with reference to the initial trajectory angle measured by two other BPMs. The method is insensitive to a bunch arrival time jitter and RF phase Common Mode jitter. A prototype of the test bench based on the method, is proposed. Using a 10MeV beam, two simple dipole cavities and low RF power, the prototype can be utilized for mastering high resolution measurements, for adjustment and tests of low level electronics of the Crab Cavity system and RF systems of XFEL ERLs as well. The phase resolution of the prototype is estimated as 0.01deg and the amplitude resolution as 0.01%.
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MOPLS042 | Longitudinal Beam Stability for CESR-c | feedback, luminosity, synchrotron, storage-ring | 634 | ||||
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The Cornell Electron-Positron Storage Ring (CESR) operates at 1.9 GeV per beam for high energy physics collisions. To maintain high luminosity it is essential for the bunch trains to be longitudinally stable. Measurements of longitudinal stability with a single, multiple, and colliding trains have been performed using a dual sweep streak camera and are presented in this paper.
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MOPLS043 | Studies of the Beam-beam Interaction at CESR | electron, optics, injection, lattice | 637 | ||||
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The Cornell Electron Storage Ring facility operates 2-GeV multi-bunch electron and positron beams in a single beam-pipe. Electrostatic separators are used to separate the two counter-rotating beams at the parasitic crossings. When the beam energy was lowered from 5 GeV in 2003, the strength of the beam-beam interaction became a more important factor in beam-current limitations, resulting in extensive experimental and calculational studies of their characteristics. The CESR lattice design procedure has been modified recently to account explicitly for their dynamic consequences. We describe our modelling of the beam-beam interaction, experimental validation techniques, and investigations into compensation strategies.
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MOPLS044 | Luminosity Variations along Bunch Trains in PEP-II | luminosity, electron, synchrotron, quadrupole | 640 | ||||
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In spring of 2005 after a long shut-down, the luminosity of the B-Factory PEP-II decreased along the bunch trains by about 25-30%. There were many reasons studied which could have caused this performance degradation, like a bigger phase transient due to an additional RF station in the Low-Energy-Ring (LER), bad initial vacuum, electron cloud, chromaticity, steering, dispersion in cavities, beam optics, etc. The initial specific luminosity of 4.2 sloped down to 3.2 and even 2.8 for a long train (typical: 130 of 144), later in the run with higher currents and shorter trains (65 of 72) the numbers were more like 3.2 down to 2.6. Finally after steering the interaction region for an unrelated reason (overheated BPM buttons) and the consequential lower luminosity for two weeks, the luminosity slope problem was mysteriously gone. Several parameters got changed and there is still some discussion about which one finally fixed the problem. Among others, likely candidates are: the LER betatron function in x at the interaction point got reduced, making the LER x stronger, dispersion reduction in the cavities, and finding and fixing a partially shorted magnet.
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MOPLS045 | Achieving a Luminosity of 1034/cm2/s in the PEP-II B-factory | luminosity, injection, electron, beam-beam-effects | 643 | ||||
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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 exceeded 1x1034/cm2/s and has delivered an integrated luminosity of 728/pb in one day. PEP-II operates in continuous injection mode for both beams, boosting the integrated luminosity. The peak positron current has reached 2.94 A and 1.74 A of electrons in 1732 bunches. The total integrated luminosity since turn on in 1999 has reached over 333/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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MOPLS058 | eRHIC - Future Machine for Experiments on Electron-ion Collisions | electron, proton, luminosity, ion | 676 | ||||
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The paper presents recent developments for the design of the high luminosity electron-ion collider, eRHIC, proposed on the basis of the existing RHIC machine. The goal of eRHIC is to provide collisions of electrons and positrons on ions and protons in the center-of-mass energy range from 30 to 100 GeV. Lepton beams as well as the beam of protons (and, possibly, light ions) should be polarized. Two independent designs are under development, the so-called 'ring-ring' and 'linac-ring' options. The 'ring-ring' option is based on a 10 GeV electron storage ring. The design issues for the 'ring-ring' option are similar to those at existing B-factories. In the 'linac-ring' option, the electron beam is accelerated in a 10 GeV recirculating energy recovery linac. This option may provide higher luminosities (> 1·1033 cm-2s-1 for e-p collisions), but requires considerable R&D studies for a high current electron polarized source. In order to maximize the collider luminosity, ion ring upgrades, such as electron cooling and ion beam intensity increase, are considered.
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MOPLS068 | Beam Impact of the ILC Collimators | simulation, LEFT, electron, monitoring | 703 | ||||
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Spoilers in the ILC Beam Delivery System are required to survive a minimum of 1-2 direct impacts from each energetic electron or positron bunch of charged particles without failure, in addition to maintaining low geometric and resistive wall wakefields. The transient shock wave resulting from rapid localised beam heating and its implications for spoiler design are studied using ANSYS. The realistic patterns of energy deposition are taken from FLUKA.The results presented quantify uncertainties in the predictions and consider possible options for spoiler jaws for the ILC.
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MOPLS069 | Development of a Superconducting Helical Undulator for the ILC Positron Source | undulator, electron, linear-collider, CERN | 706 | ||||
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An undulator positron source has been recently selected by the International Linear Collider (ILC) community as a baseline. For the ILC a helical undulator capable of producing 10 MeV photons and with a period as close as possible to 10 mm is required. The HeliCal collaboration in the UK is looking at the merits of both permanent magnet and superconducting technologies for the design of a helical undulator. For the superconducting option, several prototypes have been built and tested. This paper details the design, construction and test results of the first superconducting prototypes.
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MOPLS072 | Status of the HeLiCal Contribution to the Polarised Positron Source for the International Linear Collider | undulator, electron, photon, polarization | 715 | ||||
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The baseline positron source for the International Linear Collider is a helical undulator-based design, which can generate unprecedented quantities of polarised positrons. A major thrust of the global design in this area is led by the UK-based HeLiCal collaboration. The collaboration takes responsibility for the design and prototyping of the helical undulator itself, which is a highly demanding short period device with very small aperture, and also leads the start to end simulations of the polarised particles to ensure that the high polarisation levels generated are maintained from the source, right through the beam transport systems and up to the interaction point itself. This paper will provide an update on the work of the collaboration, focusing on these two topic areas, and will also discuss future plans.
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MOPLS075 | Progress towards Crab Cavity Solutions for the ILC | luminosity, focusing, quadrupole, electron | 724 | ||||
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In order to achieve acceptable luminosity for ILC crossing angles greater than a few mrad, RF deflection cavities must be used to rotate electron and position bunches leading up to the IP. A bunch that passes through a deflection cavity at a phase where the deflection averages to zero receives a crab kick leading to a finite rotation at the IP. For a beam energy of 500GeV and a crossing angle of 20mrad, the required crab kick is about 19.5MV at 1.3GHz and 6.5MV at 3.9GHz. Cavities are needed on both beams and are likely to be positioned about 12m before the IP. Any RF phase error between the bunch and the cavity leads to a deflection of the bunch in addition to a rotation of the bunch. Any differential phase error between the cavities leads to differing deflections and consequential loss in luminosity. Collaborative work with FNAL, being undertaken to develop a variant of their 3.9GHz CKM cavity optimised for an ILC solution, is described. Current analysis favours a solution with four nine-cell cavities on each beam. It is anticipated that the cavities will be run CW and driven from small Klystron/s (< 5kW) or solid state amplifiers.*
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*We would like to thank Chris Adolphsen, SLAC, for his help in technical discussions, which were greatly appreciated. |
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MOPLS088 | Resonant Kicker System for Head-on-collision Option of Linear Collider | kicker, electron, linear-collider, collider | 759 | ||||
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The separation of incoming and outgoing (electron and positron) beams at the interaction point of a linear collider is investigated using a resonant kicker system. It should enable head-on-collisions at the interaction point with the use of staggered passing times for each bunch at certain locations. Magnetic core materials for such a resonant kicker with a frequency of 6MHz are under investigation. Such a kicker system should minimize the perturbation of the incoming bunch with a finite bunch length, while it kicks the outgoing bunch by more than 1 millirad. Various arrangements of such kickers along the beamlines are discussed.
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MOPLS105 | Collimators for ILC | undulator, target, electron, radiation | 807 | ||||
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We considered two types of collimators for usage in undulator conversion system of ILC. In the first, the Pyrolytic graphite is used and it is installed in front of a target; the second one uses InGa alloy in rotating cylinder. The last one installed in front of undulator. Collimators allow absorption single train on bunches in ILC and enhace the photon polarization.
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MOPLS106 | Independent Operation of Electron/Positron Wings of ILC | kicker, electron, target, linac | 810 | ||||
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We represent a concept of fast feedback system allowing independent operation of electron-positron wings of ILC.
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MOPLS107 | Test of SC Undulator for ILC | undulator, vacuum, collider, electron | 813 | ||||
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We represent details of design and results of test SC 40cm-long undulator having period 10mm and aperture ~8 mm allowing K=0.7. This undulator can be used in ILC positron conversion system.
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MOPLS108 | Liquid Metal Target for ILC | target, undulator, single-bunch, electron | 816 | ||||
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We considered the Hg target for gamma/positron conversion suitable for usage in ILC project. Positron scheme generation with undulator allows usage thin Hg jet confined in profiled duct with rectangular cross-section.
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MOPLS109 | Operational Experience with Undulator for E-166 | undulator, electron, vacuum, SLAC | 819 | ||||
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We represent results of operation of 2.54 mm period, K=0.2, up to 30 Hz undulator used in E-166 experiment for polarized positron production. One peculiarity is in usage of Ferrofluid for cooling.
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MOPLS118 | Magnetic Modelling of a Short-period Superconducting Helical Undulator for the ILC Positron Source | undulator, TESLA, photon, cryogenics | 840 | ||||
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A positron source utilising undulators is now defined as the baseline option for the International Linear Collider (ILC). The ILC requires a short period undulator, as close to 10mm as possible, that is capable of producing 10 MeV photons. The HeliCal collaboration in the UK has undertaken a programme to design, develop and produce a prototype undulator. As part of the programme, the group has used the OPERA software package to perform the magnetic design of the undulator. The design has addressed several issues, including the effect of magnetic material for the undulator former, optimal winding geometry, the magnetic flux inside the superconductor and its variation with undulator period and the winding bore. This paper summarizes the results of both the 2d and the 3d magnetic simulations.
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MOPLS121 | The DAFNE Beam Test Facility: from 1 to 10 Milliards of Particles | electron, photon, linac, target | 846 | ||||
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The DAFNE Beam Test Facility is operating since 2002, providing electrons, positrons and photons from the single particle up to 1010 particleS per spill and from 20 to 750 MeV. During these years, the facility has hosted tens of high energy test and experiments coming from all Europe, operating in a wide spread of multiplicity and energy. Operation performance and parameters, tools and diagnostics, as well as the main results obtained, are presented.
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MOPLS124 | The KEK Injector Upgrade for the Fast Beam-Mode Switch | KEKB, linac, electron, injection | 855 | ||||
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The KEK linac is a 600-m-long linear accelerator with maximum energy 8-GeV electron and 3.5-GeV positron, and it is used as an injector for 4-rings (KEKB e-/ e+, PF, PF-AR). To increase the operation efficiency, we have an injector upgrade plan for the quasi-simultaneous injection. In this paper, we will present the operation scheme and the construction of a new beam transport line in detail.
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MOPLS137 | Tracking Studies to Determine the Required Wiggler Aperture for the ILC Damping Rings | lattice, wiggler, damping, injection | 879 | ||||
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The injection efficiency of an ILC damping ring is closely tied to its acceptance. To maximize both, one wants a physical aperture as large as possible in the wiggler magnets, as these are the limiting physical apertures in the ring. On the other hand, a small aperture in the wiggler magnets is needed to achieve the required field profile, a high magnetic field that is very linear over the whole physical aperture of the magnet. Tracking studies were done for all proposed ILC damping ring lattices to determine their required apertures. Although a half-aperture of 8 or 10 mm had been proposed, our studies showed that, for most lattices, a 16 mm half-aperture is required. (For some lattices a 12 mm half aperture might suffice.) We present here the results of our studies, which led to adopting a 16 mm half-aperture in the current ILC damping ring baseline design.
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MOPLS141 | The Proposed Conversion of CESR to an ILC Damping Ring Test Facility | emittance, damping, wiggler, electron | 891 | ||||
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In 2008 the Cornell Electron Storage Ring (CESR) will end nearly three decades of providing electron-positron collisions for the CLEO experiment. At that time it will be possible to reconfigure CESR as a damping ring test facility, CesrTF, for the International Linear Collider (ILC) project. With its complement of 12 damping wigglers, CesrTF will offer horizontal emittances in the few nanometer range and, ideally, vertical emittances approaching those specified for the ILC damping rings. An important feature of the CesrTF concept is the ability to operate with positrons or electrons. Positron operation will allow detailed testing of electron cloud issues critical for the operation of the ILC positron damping rings. Other key features include operation with wigglers that meet or exceed all ILC damping ring requirements, the ability to operate from 1.5 to 5.5 GeV beam energies, and the provision of a large insertion region for testing damping ring hardware. We discuss in detail the CesrTF machine parameters, critical conversion issues, and experimental reach for damping ring studies.
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TUODFI02 | DAFNE Experience with Negative Momentum Compaction | electron, luminosity, lattice, feedback | 989 | ||||
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There are several potential advantages for a collider operation with a lattice having a negative momentum compaction factor (alfa): bunches can be shorter and have a more regular shape; longitudinal beam-beam effects and synchrobetatron resonances are predicted to be less dangerous; requirements on sextupole strengths can be relaxed because there is no head-tail instability with the negative chromaticity. Since the lattice of the Frascati e+e- Phi-factory DAFNE is flexible enough to provide collider operation with alfa < 0, we have exploited this possibility to study experimentally the beam dynamics. The negative momentum compaction lattices have been successfully implemented and stable 1 A currents have been stored in both the electron and positron rings without any problem for RF cavities and feedback systems operation. First collisions have been tested at low currents. In this paper we describe the experimental results and compare them with expectations and numerical simulations. Present limitations to DAFNE operation with alfa < 0 are also discussed.
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Transparencies
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TUODFI03 | Operational Status of CESR-c | luminosity, optics, wiggler, electron | 992 | ||||
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We summarize recent running experience at the Cornell Electron Storage Ring operating as a high-statistics production-threshold factory for mesons containing charm quarks. Since beginning operation at beam energies near 2 GeV in late 2003, CESR has accumulated world-record samples of D and D$_s$ meson decays and has also operated in an energy-scanning mode, making unique contributions to the presently very active field of charm spectroscopy. CESR lattice design is characterized by the versatility provided by the variety of beam-line components applied to the challenges imposed by the beam-beam interactions at the parasitic crossing points in the pretzel orbits and the necessity of powerful superconducting wiggler magnets used to tune damping and emittance. We describe the observed tune-plane, beam-current and luminosity limits, as well as our understanding of their sources and near-term plans for operational improvements.
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Transparencies
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TUPCH049 | Proposal for a Fast Scanning System Based on Electro-optics for Use at the ILC Laser-wire | laser, electron, focusing, PETRA | 1118 | ||||
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Electro-optic devices open the possibility of ultra-fast scanning systems for use in intra-train scanning at the ILC, where scanning rates in excess of 100 kHz may be required. A first study of the possibilities is presented together with the first results from a prototype system.
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TUPCH070 | Development of Beam Profile Monitor for Cyclotron | cyclotron, CDA, TTF, vacuum | 1169 | ||||
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A beam profile monitor was designed and fabricated to measure the beam shape of the cyclotron MC50 beam line at KIRAMS. The sensor module was made of 13 tungsten wires and they were assembled into an array type. The sensor wires whose diameter is 1 mm were placed in parallel with the incident beam, while they were placed in the perpendicular direction to the incident beam in the conventional method. Thus this monitor has a linear actuator to scan whole beam profile, which moves the sensor module from the dormant to measurement position or vice versa. The current output of each sensor was amplified using a trans-resistance amplifier which can measure input current in the range of 1 pA. The amplifier had a resolution of ~ 20 fA, the temperature drift of ~0.5 pA/°C, and the signal-to-noise ratio greater than 80 dB. Various test results of the amplifier and sensor module assembly are given in this paper. The measured current profiles of cyclotron beam line at KIRAMS are also given.
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TUPCH097 | Instrumentation and Operation of a Remote Operation Beam Diagnostics Lab at the Cornell Electron-positron Storage Ring | radiation, optics, electron, synchrotron | 1238 | ||||
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Accelerator beam diagnostics are being modified at the Laboratory of Elementary Particle Physics (LEPP) at Cornell University for remote operation at nearby Alfred University. Presently, a streak camera used for longitudinal dynamics measurements on the Cornell Electron-Positron Storage Ring (CESR) is operational and measurements have been made from Alfred University [1]. In the near future, photomultiplier tube arrays for electron and positron vertical beam dynamics measurements will be remotely operated as well. In this paper, we describe instrumentation and operation of the remote beam diagnostics.
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TUPCH108 | Characterization of the PEP-II Colliding-beam Phase Space by the Boost Method | emittance, electron, coupling, simulation | 1262 | ||||
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We present a novel approach to characterize the colliding-beam phase space at the interaction point of the energy-asymmetric PEP-II B-Factory. The method exploits the fact that the transverse-boost distribution of e+ e- > mu+ mu- events reconstructed in the BaBar tracking system, reflects that of the colliding electrons & positrons. The average boost direction, when combined with the measured orientation of the luminous ellipsoid, determines the e+e- crossing angles. Varying the horizontal direction of one beam with respect to the other in a controlled fashion allows to estimate the individual e+ and e- horizontal IP beam sizes. The angular spread of the transverse boost vector provides an accurate measure of the angular spread of the incoming high-energy beam, confirming the presence of a significant beam-beam induced increase of this angular spread. In addition, the longitudinal dependence of the angular spread of the boost vector in the y-z plane allows to extract from the continuously-monitored boost distributions, a weighted average of the vertical IP beta-functions & emittances of the two beams representative of routine high-luminosity operation.
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TUPLS003 | A Perfect Electrode to Suppress Secondary Electrons inside the Magnets | electron, dipole, KEKB, quadrupole | 1489 | ||||
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Electron cloud due to multipacting in the positron ring of B-factories is one of the limitations on the machine performance. Electron cloud in the drift region can be suppressed by solenoid. However, solenoid doesn't work inside a magnet. Numerical studies show that there is strong multipacting in the dipole magnet of the B-factory positron ring. Electrons also can be trapped inside quadrupole and sextupole magnets. The electron cloud from the dipole magnet and wiggler in the positron damping ring of the ILC is a critical limitation on the choice of damping ring circumference, which directly results in a choice of two 6km rings as the baseline for the positron damping ring. Various electrodes have been studied using the program CLOUDLAND. Our studies show that a wire type of electrode with a few hundred voltages works perfectly to kill the secondary electrons inside various magnets.
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TUPLS009 | Design and Tests of New Fast Kickers for the DAFNE Collider and the ILC Damping Rings | kicker, impedance, injection, damping | 1502 | ||||
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In this paper we illustrate the design of new, fast stripline kickers to inject or extract bunches in electron/positron rings. The kickers have been designed for the injection upgrade of the Phi-factory DAFNE and as injection/extraction devices for the International Linear Collider (ILC) damping rings. The design is based on tapering the striplines in order to simultaneously obtain low impedance and an excellent uniformity of the deflecting field. The design has been done using 2D and 3D electromagnetic codes such as Superfish and HFSS. High voltage test results on prototypes are also shown.
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TUPLS063 | Layout of the USR at FLAIR | storage-ring, ion, electron, antiproton | 1636 | ||||
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The Facility for Low-energy Antiproton and Ion Research (FLAIR) and a large part of the wide physics program decisively rely on new experimental techniques to cool and slow down antiprotons to 20 keV, namely on the development of an ultra-low energy electrostatic storage ring (USR). The whole research program connected with anti-matter/matter interactions is only feasible if such a machine will be realized For the USR to fulfil its key role in the FLAIR project, the development of novel and challenging methods and technologies is necessary: the combination of the electrostatic storage mode with a deceleration of the stored ions from 300 keV to 20 keV, electron cooling at all energies in both longitudinal and transverse phase-space, bunching of the stored beam to ultra-short pulses in the nanosecond regime and the development of an in-ring reaction microscope for antiproton-matter rearrangement experiments. In this contribution, the layout and the expected beam parameters of the USR are presented and its role within FLAIR described. The machine lattice and the cooler parameters are summarized.
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WEPCH053 | Peculiarities of Influence of Coherency Processes at Charged Particles Channeling on Particle Beams Characteristics | proton, controls, electron | 2041 | ||||
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In the work the length of reciprocal coherency existence and peculiarities of coherency of different states of channeled particles wave functions are discussed. It was shown that the length of coherent channeling depends on the monochromaticity of initial particle beam as well as on the interaction of channeled particles with thermal oscillations of the crystal lattice. Peculiarities of influence of coherency processes at relativistic and nonrelativistic charged particles channeling on spatial and angular characteristics of particle beam that has passed through a thin crystal are discussed. In was shown, that the influence of different particle states interference within the area of coherent channeling leads to very strong periodic dependence of final beam angular width from the crystal length. This effect allows to control beam parameters (e.g., to form narrower beam, that it was before falling on the crystal). Influence of coherency of particle states in a single channel and several channels on the angular distribution and the possibility of quasicharacteristic short-wave spontaneous and stimulated radiation is also studied.
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WEPCH061 | SABER Optical Design | electron, linac, SLAC, sextupole | 2062 | ||||
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SABER, the South Arc Beam Experimental Region, is a proposed new beam line facility designed to replace the Final Focus Test Beam at SLAC. In this paper, we outline the optical design features and beam parameters now envisioned for SABER. A magnetic chicane to compress positron bunches for SABER and a bypass line that could transport electrons or positrons from the two-thirds point of the linac to SABER, bypassing the LCLS systems, are also discussed.
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WEPCH078 | Measurement of Wake Effects by Means of Tune Shift in the KEKB Low-Energy Ring | electron, betatron, single-bunch, KEKB | 2101 | ||||
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The electron cloud produced by the positron beam induces single-bunch and coupled-bunch wakes, in addition to a tune shift. Effects of the dipole wake-field including the electron cloud were tried to measure in the KEKB Low Energy Ring. A test bunch was placed behind a bunch-train of the positron beam, even though a test bunch itself might interact with the remaining electron cloud. We measured a current-dependent tune-shift of a test bunch under constant train-current, while changing the bucket position of a test bunch. The tune shift indicated a strong defocusing field, however, tended to a focusing field when a test bunch approached a train with high train-current. The results are discussed, considering variations of the electron cloud density.
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WEPCH146 | Intrabeam Scattering Studies for the ILC Damping Rings Using a New Matlab Code | wiggler, damping, lattice, emittance | 2266 | ||||
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A new code to calculate the effects of intrabeam scattering (IBS)has been developed in Matlab based on the approximation suggested by K. Bane*. It interfaces with the Accelerator Toolbox** but can also read in lattice functions from other codes. The code has been benchmarked against results from other codes for the ATF*** that use this approximation or do the calculation in a different way. The new code has been used to calculate the emittance growth due to intrabeam scattering for the lattices currently proposed for the ILC Damping Rings, as IBS is a concern, especially for the electron ring. A description of the code and its user interface, as well as results for the Damping Rings, will be presented.
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*K. Bane, in Proceedings of EPAC2002, p.1443. **A. Terebilo, Accelerator Toolbox for MATLAB, SLAC-PUB-8732 and www-ssrl.slac.stanford.edu/at/. ***K. Kubo et al. PhysRevST AB.8.081001 (2005). |
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WEPLS032 | Spin Tracking at the ILC | damping, polarization, synchrotron, radiation | 2454 | ||||
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Polarized beams will play a key role in the physics programme at the International Linear Collider (ILC). It is expected that the electron and positron sources will be able to produce beams with polarizations of about 90% and 60% respectively. However, to obtain accurate measurements it is essential to have precise knowledge and control of the polarization at the interaction point itself. It follows that the theoretical calculations used for spin tracking must be guaranteed to match the anticipated 0.1% relative measurement uncertainty of the polarimeters. To meet this need, the heLiCal collaboration is developing a computer simulation to track the evolution of the polarization of bunches of electrons and positrons from the sources to the interaction point. We have studied the beam spin dynamics throughout the ILC including spin precession and radiative spin-flip processes in the positron source, damping rings, beam delivery system and the interaction region. We present the result of these studies with special emphasis on the impact of new theoretical calculations for the CAIN bunch-bunch simulation including full spin correlations and higher-order contributions.
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WEPLS045 | Study on Low-energy Positron Polarimetry | electron, target, scattering, photon | 2475 | ||||
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For the design of the International Linear Collider (ILC) a polarised positron source based on a helical undulator system has been proposed. In order to optimise the positron beam, i.e., to ensure high intensity as well as high degree of polarisation, a measurement of the polarisation close to the positron creation point is envisaged. In this contribution methods to determine the positron polarisation at low energies are investigated. These studies are based on simulations with an extended version of Geant4, which allows the tracking of polarised particles taking into account the spin effects.
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WEPLS046 | Radiation Levels and Activation at the ILC Positron Source | target, undulator, photon, electron | 2478 | ||||
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An undulator-based positron source is recommended as baseline design for the International Linear Collider (ILC). Photons generated by electrons passing an undulator hit a rotating target and create electron-positron pairs. The positrons are captured and accelerated. An advantage of this source is the significantly lower radiation level in comparison to a conventional positron source which uses the electron beam directly to produce electron-positron pairs. The fluxes of neutrons and photons have been calculated with the particle transport code FLUKA. The activation of the positron source components has been estimated depending on the parameters of the source. The results for undulator-based and conventional positron sources are compared and presented.
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WEPLS048 | Development of a Positron Production Target for the ILC Positron Source | target, photon, vacuum, undulator | 2484 | ||||
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The future International Linear Collider (ILC) will require of order 1014 positrons per second to fulfil its luminosity requirements. The current baseline design produces this unprecedented flux of positrons using an undulator-based source. In this concept, a collimated beam of 10MeV photons produced from the action of an undulator on the main electron beam of the ILC is incident on a conversion target. Positrons produced in the resulting electromagnetic shower can then be captured, accelerated and injected into a damping ring. The international community is pursuing several alternative technologies to develop a target capable of long-term operation in the intense photon beam. In the design being developed jointly by the Cockcroft Institute, LLNL and SLAC, a thin (0.4 radiation length) water-cooled Titanium alloy target wheel of diameter 4m is rotated at approximately 1000rpm to spread the incident power of each pulse over a wide area. We present the latest target design, report on the status of the target prototypes and computer models, and review the interplay between the target technology, capture optics, photon collimator and remote-handling systems.
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WEPLS060 | CLIC Polarized Positron Source Based on Laser Compton Scattering | laser, CLIC, damping, photon | 2520 | ||||
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We describe the possible layout and parameters of a polarized positron source for CLIC, where the positrons are produced from polarized gamma rays created by Compton scattering of a 1.3-GeV electron beam off a YAG laser. This scheme is very energy effective using high finesse laser cavities in conjunction with an electron storage ring. We point out the differences with respect to a similar system proposed for the ILC.
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WEPLS138 | Operation Status and Statistics of the KEK Electron/Positron Linac | linac, KEKB, injection, klystron | 2700 | ||||
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The KEK electron/positron linac has been operated since 1982, surpassing the total operation time of more than 100,000 hours. It delivers four different beams to four different rings quite stably, even frequently switching beam modes. The operation time per year has reached 7,000 hours since 1999 when the KEKB entered a normal operation mode. Operation status and statistics will be reported with the emphasis on continuing efforts in various kinds of machine improvements, which have ensured the stable operation.
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THOBFI03 | Record-high Resolution Experiments on Comparison of Spin Precession Frequencies of Electron Bunches Using the Resonant Depolarization Technique in the Storage Ring | electron, storage-ring, radiation, polarization | 2787 | ||||
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The opportunity of performing an experiment on high precision comparison of the electron and positron anomalous magnetic moments following the VEPP-2M experiment is under study at the VEPP-4M storage ring. The record accuracy of 2x10-8 was obtained for comparison of spin precession frequencies in the experiment on resonant depolarization with simultaneously circulating electron bunches, two of them polarized and one unpolarized. It is the first time when the spreading of the spin precession frequency line (~5x10-7,) due to scattering of particle trajectories about the equilibrium orbit in a non-linear field of the storage ring, was presumably observed in experiments. We proposed and realized an RF scheme for controlled separation of the spin precession frequencies of two electron bunches; the first measurements using this scheme were made.
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THPCH011 | Wire Compensation of Parasitic Crossings in DAFNE | luminosity, simulation, injection, collider | 2808 | ||||
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Long-range beam-beam interactions (parasitic crossings) are one of the main luminosity performance limitations for the Frascati e+e- Phi-factory DAFNE. In particular, the parasitic crossings (PC) lead to a substantial lifetime reduction of both beams in collision. This puts a limit on the maximum storable current and, as a consequence, on achievable peak and integrated luminosity. In order to alleviate the problem numerical and experimental studies of the PC compensation with current-carrying wires have been performed at DAFNE. Two such wires have been installed at both ends of the KLOE interaction region. Switching on the wires in accordance with the numerical predictions, improvement in the lifetime of the "weak" beam (positrons) has been obtained at the maximum current of the "strong" one (electrons) without luminosity loss. In this paper we describe the PC effects in DAFNE, summarize the results of numerical simulations on the PC compensation with the wires and discuss the experimental measurements and observations.
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THPCH049 | Simulation Study of Transverse Coupled-bunch Instabilities due to Electron Cloud in KEKB LER | electron, simulation, KEKB, quadrupole | 2895 | ||||
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In this paper we report simulation results on the transverse coupled-bunch instabilities (TCBI) due to electron cloud at the KEKB Low Energy Ring (LER). The formation of electron cloud and related TCBI is investigated based on realistic solenoid field model. Studies on electron cloud in Quadrupole which could induce TCBI are also presented in this paper.
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THPCH075 | Simulation of the Electron Cloud for Various Configurations of a Damping Ring for the ILC | electron, damping, simulation, wiggler | 2958 | ||||
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In the beam pipe of the Damping Ring (DR) of the International Linear Collider (ILC), an electron cloud may be first produced by photoelectrons and ionization of residual gasses and then increased by the secondary emission process. This paper reports about the work that has been done by the electron cloud assessment international task force group for the recommendation of the ILC Damping Rings baseline design, made in November 2005. We have carefully estimated the secondary electron yield (SEY) threshold for electron cloud build-up and estimated the related single- and coupled-bunch instabilities that can be caused by the presence of electron cloud as a function of beam current and surface properties, for a variety of optics designs. The result of these studies was an important consideration in the choice of a 6-km design for the ILC damping rings. On the basis of the theoretical and experimental work, the baseline configuration specifies a pair of damping rings for the positron beam to mitigate the effects of the electron cloud.
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THPCH076 | Resistive Wall Wake Effect of a Grooved Vacuum Chamber | vacuum, impedance, SLAC, electron | 2961 | ||||
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To suppress the emission of secondary electrons in accelerators with positively charged beams (ions or positrons) it has been proposed to use a vacuum chamber that is longitudinally grooved (or, equivalently, one can say finned)*/**. One consequence of having such a chamber in an accelerator is an increased resistive wall impedance. In this paper, we calculate the resistive wall impedance of one such finned chamber, planned to be used in experimental studies of secondary emission suppression at SLAC. For rectangular fins, we use an analytical method based on a conformal mapping approach; we compare the results with a numerical solution of the field equation. We also numerically compute the impedance for rounded fins (as will be used in the SLAC experiment) and analyse how the impedance depends on geometric properties of the fins.
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*A. A. Krasnov. Vaccum, vol. 73, p. 195, (2004).**G. Stupakov and M. Pivi. Preprint SLAC-TN-04-045, (2004). |
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THPCH116 | Continuous Circumference Control and Timing System for Simultaneous Electron-positron Injection at the KEKB | linac, KEKB, injection, controls | 3074 | ||||
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We have continuously controlled ring circumference with a new method of synthesizer control at the KEKB. The new method stands for continuous controlling of reference frequency of synthesizers. Due to the new circumference control, we stabilized the KEKB circumference within about 6 micrometers. In Fall 2006, KEKB will introduce simultaneous electron-positron injection scheme. We have to change the timing system of KEKB to control the injection phase with pulse-to-pulse injection. We show the plan of the new timing system due to the simultaneous injection scheme.
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