CESR-c operates with twelve 2.1 Tesla wigglers that account for 90% of the synchrotron radiation with beam energy in the range of 1.8 to 2.1 GeV. The wigglers reduce the radiation damping time from 0.5 seconds to 50 milliseconds. The carefully designed wigglers restrict neither physical nor dynamic aperture of the storage ring, though both quadrupole and sextupole distributions must be tailored to compensate the primary optics effects of the wigglers. Colliding beam performance limits are determined by the numerous parasitic beam-beam interactions in the single ring. Several approaches taken to mitigate these limiting effects are described herein. The CESR-c wigglers are an excellent match to the requirements for future damping rings. We describe how with flexible optics, extensive infrastructure, and resource expertise, they form an effective test bed for assessment and solution of damping ring issues such as electron cloud and ion effects, and achieving ultra-low emittance beams.
CLASSE, Ithaca
CHESS, Ithaca, New York
Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
Cornell University, Department of Physics, Ithaca, New York
The status of plans for an Energy-Recovery Linac (ERL) X-ray facility at Cornell University is described. Currently, Cornell operates the Cornell High Energy Synchrotron Source (CHESS) at the CESR ring and the ERL is planned to be an extension to the CESR ring with the addition of a 5-GeV superconducting c.w. linac. Topics covered in this paper include the full layout on the Cornell campus, the different operation modes of the accelerator, methods to limit emittance growth, control of beam-ion effects and ways to limit transverse instabilities. As an upgrade of the CESR ring, special attention is given to reuse of many of the existing components. The very small electron-beam emittances would produce an x-ray source that is highly superior than any existing storage-ring light source. The ERL includes 18 X-ray beamlines optimized for specific areas of research that are currently being defined by an international group of scientists. This planned upgrade illustrates how other existing storage rings could be upgraded to work as ERL light sources with vastly improved beam qualities and with limited dark time for x-ray users.
KEK, Ibaraki
CERN, Geneva
ENSEM, Vandoeuvre les Nancy
Studies for the LHC luminosity upgrade showed the need for quadrupoles with apertures much larger than the present baseline (70 mm). In this paper we focus on the design issues of a 130 mm aperture quadrupole. We first consider the Nb-Ti option, presenting the magnetic design with the LHC dipole cable. We study the Lorentz forces and we discuss the field quality constraints. For the Nb3Sn option we sketch two designs, the first based on the LARP 10 mm cable, and the second one on a 15 mm cable. The issue of the stress induced by the Lorentz forces, which is critical for the Nb3Sn, is discussed using both scaling laws and finite element models.
CERN, Geneva
SLAC, Menlo Park, California
Changes to beamline optics may effect many engineering processes downstream. In the past, we incorporated these changes manually into disparate engineering spreadsheets. At LCLS, database applications have been developed in order to compare and clearly display differences amongst various versions of beamline optics files. These applications also incorporate the changes into engineering databases, after they have been validated by the engineers. This allows the engineers to be notified, and modifications to be made if beamline optics changes require corresponding adjustments of engineering elements. This paper will describe how this streamlines the workflow, and also provides greater reliability in how beamline optics changes are integrated into engineering databases (such as cabling, power supplies, inventory). The paper includes a description of the related LCLS inventory system, which also serves as a repository for quality assurance documents. The underlying database schemas and applications will be outlined.
CERN, Geneva
TRIUMF, Vancouver
The International Linear Collider (ILC) requires ultra fast kickers for the damping ring. One option requires kickers which must produce pulses of 5 kV magnitude, with 6 ns rise and 6 ns fall time into a 50 Ohm, terminated, matched stripline deflector. The pulse must rise and fall within 12 ns. The pulse magnitude must be repeatable to a high accuracy. This paper describes a novel design for a suitable pulse generator for the damping ring kicker, in which 2 stacks of 1kV FETS are combined to generate the fast pulses. The design concept uses 2 parallel 100 Ω drivers combined to provide a 50 Ω driver. The need for 3 MHz burst mode operation for 1 ms at 5 Hz (or 10 Hz) gives an average rep rate of 15 kHz (or 30 kHz). Measurements and calculations are presented on the present state of the TRIUMF prototype pulse generator.
ORNL, Oak Ridge, Tennessee
SLAC, Menlo Park, California
The Accelerator Physics group at the Spallation Neutron Source (SNS) has developed numerous codes to assist in the beam commissioning, tuning, and operation of the SNS Linac. These codes have been key to meeting the beam commissioning milestones. For example, a recently developed code provides for rapid retuning of the superconducting Linac in case of RF stations going offline or coming online. Highlights of these "physics applications" will be presented.
Tech-X, Boulder, Colorado
LBNL, Berkeley, California
Fermilab, Batavia, Illinois
ALBA, Bellaterra (Cerdanyola del Valles)
Diamond, Oxfordshire
Diamond, Oxfordshire
ANL, Argonne, Illinois
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
Photons that carry orbital angular momentum are of great interest to the optics and laser communities*. This exotic property of photon beams was recently demonstrated in the x-ray regime** and may be useful to probe angular momentum in matter***. However, by comparison to the visible light regime, it is difficult to fabricate efficient achromatic optics to generate these optical modes in x-rays. In spite of these inconveniences, there has been no investigation of the possibility of using a synchrotron light source to directly generate an x-ray beam with transverse optical modes. In this paper, we investigate use of an APPLE-type undulator for generating Laguerre-Gaussian (LG) and Hermite-Gaussian (HG) mode beams. We find that the second harmonic radiation in the circular mode corresponds to an LG beam with l=1, and the second harmonic in the linear mode corresponds to an HG beam with l=1. The combination of an APPLE undulator and conventional monochromator optics may provide an opportunity for a new type of experimental research in the synchrotron radiation community. Detailed discussion will be presented in the conference. We thank C. Quitmann for insightful comments.
* M. Padgett, J. Courtial, L. Allen, Physics Today, p. 35, May, 2004.** A. G. Peele et al., Optics Letters, 27, 1752 (2002).*** M. VanVeenendaal and I. McNulty, Phys. Rev. Lett., submitted.
SLAC, Menlo Park, California
DESY, Hamburg
Jefferson Lab, Newport News, Virginia
SBUNSL, Stony Brook, New York
BNL, Upton, Long Island, New York
We report recent progress in the development of a hybrid lead/niobium superconducting (SC) injector. The goal of this effort is to produce an all-SC injector with the SCRF properties of a niobium cavity along with the superior quantum efficiency (QE) of a lead photocathode. Two prototype hybrid injectors have been constructed, one utilizing a cavity with a removable cathode plug, and a second consisting of an all-niobium cavity arc-deposited with lead in the cathode region. We present the results of QE measurements on these cavities, along with tests of the effect of the laser on the cavity RF performance.
INFN/LNF, Frascati (Roma)
KEK, Ibaraki
BINP SB RAS, Novosibirsk
For the KEKB Accelerator Group.
Due to the errors in all kinds of components of storage ring, the real ring optics is different from the design one. A computer code LOCO is developed to calibrate the linear optics based on the closed orbit response matrix. This paper discusses mainly on the procedure and results of optics correction at BEPCII BPR. Using LOCO, we have determined the errors of quadrupole strengths, BPM gains and corrector kicks, and found the quadrupole strengths that best restore the design optics with sextupoles on. Optics measurement after correction shows the real optics agrees well with the design optics.
weiyy@mail.ihep.ac.cn
KAERI, Daejon
The Proton Engineering Frontier Project (PEFP) will supply 20-MeV and 100-MeV proton beams from a 100 MeV proton linear accelerator for beam applications. The extracted 20 MeV or 100 MeV proton beams will be simultaneously distributed into the five targets through a dipole magnet equipped with a controllable AC power supply. The most important design criterion is the flexibility of the irradiation conditions in order to meet various user requirements in many application fields. For this purpose, we have designed the beamlines to the targets for wide or focused beams, external or in-vacuum beams, and horizontal or vertical beams. This work includes details of the conceptual design of the beamlines.
EPFL, Lausanne
CERN, Geneva
BNL, Upton, Long Island, New York
Fermilab, Batavia, Illinois
CERN, Geneva
Fermilab, Batavia, Illinois
The operation and performance of the new, 15 Hz, H- charge exchange injection system for the FNAL Booster is described. The new system installed in 2006 was necessary to allow injection into the Booster at up to 15 Hz. It was built using radiation hardened materials which will allow the Booster to reliably meet the high intensity and repetition rate requirements of the Fermilab's HEP program. The new design uses three orbit bump magnets (Orbmps) rather than the usual four and permits injection into the Booster without a septum magnet. Injection beam line modification and compensation for the quadrupole gradients of the Orbmp magnets is discussed.
Fermilab, Batavia, Illinois
CESR-LEPP, Ithaca, New York
Following two decades of operation at 5 GeV beam energy for studies of bottom quark bound states, the Cornell Electron Storage Ring (CESR) converted to 2 GeV operation in 2001 for the purpose of investigating bound states of charm quarks. This reduction of beam energy resulted in increased relative contributions of the beam-beam force. The beam-beam interaction has been found to have considerable consequences for the optics and for the injection aperture. We describe recent developments in our modelling of the beam-beam interaction, experimental validation techniques, and investigations into compensation strategies.
SLAC, Menlo Park, California
INFN/LNF, Frascati (Roma)
BNL, Upton, Long Island, New York
A beam-based method was proposed and applied to check the polarities of the arc sextupoles in the Relativistic Heavy Ion Collider (RHIC) with repetitive local horizontal bumps. Wrong sextupole polarities can be easily identified from mismatched signs and amplitudes of the horizontal and vertical tune shifts from bump to bump and/or from arc to arc. This check takes less than 2 hours for both RHIC Blue and Yellow rings. Tune shifts in both planes during this study were tracked with a high-resolution baseband tunemeter (BBQ) system. This method was successfully used to the sextupole polarity check in the RHIC run06.
BNL, Upton, Long Island, New York
A hydrogen jet polarimeter was developed for the RHIC accelerator to improve the process of measuring polarization. Particle beams intersecting with gas molecules can produce light by the process known as luminescence. This light can then be focused, collected, and processed giving important information such as size, position, emittance, motion, and other parameters. The RHIC hydrogen jet polarimeter was modified in 2005 with specialized optics, vacuum windows, light transport, and camera system making it possible to monitor the luminescence produced by polarized protons intersecting the hydrogen beam. This paper will describe the configuration and preliminary measurements taken using the RHIC hydrogen jet polarimeter as a luminescence monitor.
LAL, Orsay
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
UMAN, Manchester
CERN, Geneva
CEA, Gif-sur-Yvette
Kyoto ICR, Uji, Kyoto
SLAC, Menlo Park, California
KEK, Ibaraki
LBNL, Berkeley, California
An interaction region with head-on collisions is considered as an alternative to the baseline ILC configuration. Progress in the final focus optics design includes engineered large bore superconducting final doublet magnets and their 3D magnetic integration in the detector solenoids. Progress on the beam separation optics is based on technical designs of electrostatic separator and special extraction quadripoles. The spent beam extraction is realized by a staged collimation scheme relying on realistic collimators. The impact on the detector background is estimated. The possibility of technical tests of the most challenging components is investigated.
Kyoto ICR, Uji, Kyoto
NIRS, Chiba-shi
KEK, Ibaraki
SLAC, Menlo Park, California
An adjustable permanent magnet quadrupole has been developed for the final focus in an electron-positron linear collider. The design has two concentric rings of permanent magnets. Recent activities include a newly fabricated inner ring that demonstrates the strongest field gradient at a small bore diameter of 15mm and a new magnetic field measurement system based on a rotating coil. The prospects of the R&D will be discussed.
INFN/LNF, Frascati (Roma)
CNAO Foundation, Milan
CERN, Geneva
UU/ISV, Uppsala
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
LAL, Orsay
UMAN, Manchester
We are considering the implementation of a Lithium lens and SC solenoidal lens for collection of positrons in ILC undulator-based source. Such a lens installed right after the thin target, which is illuminated by gamma quants from helical undulator.
LLNL, Livermore, California
As part of the ongoing development of fast neutron imaging technology for national secu-rity applications at LLNL, a large-format imaging optics system has been designed and built. The system will be used to acquire radiographic images of heavily-shielded low-Z objects irradiated by ~ 10 MeV neutrons and is expected to have an ultimate spatial resolution ~ 1 mm (FWHM). It is comprised of a 65 cm x 65 cm plastic scintillator (e.g. BC-408), an aluminized front-surface turning mirror and a fast (~ f/1.25) optical lens coupled to a CCD camera body with a cryo-cooled, back-illuminated 4096 x 4096 (15 micron) pixel sensor. The lens and camera were developed and purchased from vendors and system integration was done at LLNL. A description of the overall system and its initial performance characteristics shall be presented.
SLAC, Menlo Park, California
ANL, Argonne, Illinois
Undulator-based positron source is adopted as the International Linear Collider baseline design. Complete optics to transport the positron beam having large angular divergence and large energy spread from a thin Ti target to the entrance of the 5 GeV damping ring injection line is developed. Start-to-end multi-particle tracking through the beamline is performed including the optical matching device, capture accelerator system, transport system, superconducting booster linac, spin rotators, and energy compressor. Positron capture efficiency of different schemes (immersed vs shielded target, and flux concentrator vs quarter wave transformation for the optics matching system) is compared. For the scheme of a shielded target and quarter wave transformation, the simulation shows that 15.1% of the positrons from the target are captured within the damping ring 6-D acceptance at the entrance of the damping ring injection line.
ASP, Clayton, Victoria
TRIUMF, Vancouver
TRIUMF, Vancouver
KEK, Ibaraki
DESY, Hamburg
CERN, Geneva
Northern Illinois University, DeKalb, Illinois
ANL, Argonne, Illinois
An exotic beam facility for the production of rare isotopes requires investigation of higher order optical effects, while taking into account beam-material interactions. An important component of the fragment separator is the absorber wedge, which is necessary for isotope separation. The properties of the absorber, such as the type and shape of material used, determine the resolution and transmission of the fragment separator. Nuclear reactions such as the fission and fragmentation of radioactive isotopes within the target or absorber contribute to the phase space and isotopic distributions of the beam. We have computed these distributions for all isotopes emerging from the target or absorber by implementing a limited fission model from within COSY Infinity that uses polynomial interpolations. Higher order optical aberrations have been computed and successfully eliminated by the shaping of the absorber material. COSY allows us to find the parameters of the absorber that maximize the resolution and transmission of the fragment separator. In addition, beam purity tests have been performed. From our results we have determined an appropriate location for a dump of the primary beam.
Fermilab, Batavia, Illinois
The University of Texas at Austin, Austin, Texas
Fermilab, Batavia, Illinois
MEPhI, Moscow
CERN, Geneva
Turn-by-turn BPM data provide immediate information on the coupledoptics functions at BPM locations. In the case of small deviations from the known (design) uncoupled optics some cognizance of the sources of perturbation, BPM calibration errors and tilts can also be inferred without detailed lattice modelling. In practical situations, however, fitting the lattice model with the help of some optics code would lead to more reliable results. We present an algorithm for coupled optics reconstruction from TBT data on the basis of MAD-X and give examples of its application for the Fermilab Tevatron and Booster accelerators.
Fermilab, Batavia, Illinois
The Main Injector (MI) is a rapid cycling multipurpose accelerator. After completion of the Tevatron Run II, its primary application will be the acceleration of high intensity proton beams for neutrino experiments. To achieve the intensity goal a detailed knowledge of the optics and transverse impedances is necessary which can be obtained from Turn-By-Turn (TBT) beam position measurements. The recent MI Beam Position Monitor system upgrade made it possible to apply the TBT data analysis methods which were successfully used by the authors for the Tevatron. We present the results of MI optics measurements and the impedance estimates obtained from the betatron phase advance dependence on beam current.
Fermilab, Batavia, Illinois
CHEF is both a framework and an interactive application emphasizing accelerator optics calculations. The framework supports, using a common infrastructure, multiple domains of applications: e.g. nonlinear analysis, perturbation theory, and tracking. Its underlying philosophy is to provide infrastructure with minimum hidden implicit assumptions, general enough to facilitate both routine and specialized computational tasks and to minimize duplication of necessary, complex bookkeeping tasks. CHEF was already described in recent conferences. In this paper we present a status report on the most recent developments, including issues related to its application to high energy linacs.
The University of Texas at Austin, Austin, Texas
Until recently, values of the amplitude functions through the Interaction Regions of the Tevatron collider detectors have been inferred either by reconstructing event locations through the detector and mapping out the luminous region to deduce the beam emittance and amplitude function or by performing differential closed orbit measurements while varying steering magnets and producing detailed models of the synchrotron's optical properties which reproduce the observed orbital deviations. Both of these methods rely on often lengthy off-line analyses and sometimes many hours of experimental data to obtain a meaningful result. The new Tevatron Beam Position Monitor system, commissioned in 2005, has allowed unprecedented detail of turn-by-turn motion to be measured at the 20-micron level and for thousands of beam revolutions. Such measurements performed with a freely oscillating proton beam, excited by a kicker magnet, allow for the direct measurement of the amplitude function which is model independent. A simple measurement procedure, data analysis method, and typical results for the Tevatron experimental regions are presented.
Northern Illinois University, DeKalb, Illinois
ANL, Argonne, Illinois
An Exotic Beam Facility is one of the highest priority projects in the DOE 20-year plan and a major strategic initiative for Argonne. The main components of the facility are a high-power multi-beam superconducting heavy-ion accelerator, a production complex, and finally a high-efficiency post-accelerator. This talk revolves around new approaches to heavy-ion beam dynamics for the central part, the Fragment Separators. To this end, it will summmarize the theories developed, software written, and simulations done that lead to better understanding of basic beam dynamics, more insight towards the best design choices, and optimization of the system?s parameters, including the integrated beam optics-nuclear physics approach.
G. H. Gillespie Associates, Inc., Del Mar, California
The Particle Beam Optics Laboratory, or PBO Lab, is a suite of software applications developed to support beamline design, accelerator operations, and personnel training. The software provides an intuitive and easy-to-use graphic user interface (GUI) that works with a variety of particle optics codes. The PBO Lab GUI is largely responsible for the popularity of this software suite, which is now used at more than ninety institutions throughout the world. While PBO Lab greatly improves the human-machine interface for several popular optics programs, it has historically required a significant effort to incorporate additional optics codes into the software suite. The Open Architecture Software Integration System, or OASIS, provides an innovative framework that allows users to readily integrate their own optics programs into PBO Lab. This paper provides an overview of the OASIS framework and describes some of the new PBO Lab Modules that have been created using OASIS.
SLAC, Menlo Park, California
For optics measurement and modeling of the PEP-II electron (HER) and position (LER) storage rings, we have been doing well with MIA* which requires analyzing turn-by-turn Beam Position Monitor (BPM) data that are resonantly excited at the horizontal, vertical, and longitudinal tunes respectively. However, in anticipating that certain BPM buttons or even pins in the PEP-II IR region will be missing for the next run starting in January 2007, we have been developing a data validation process, hoping to reduce the effect due to the reduced BPM data accuracy on PEP-II optics measurement and modeling. Besides the routine process for ranking BPM noise level through data correlation among BPMs, allowing BPMs to have linear gains and linear cross couplings, we can also check BPM data symplecticity by comparing the invariant ratios. We may also work out nonlinear BPM data correction if needed. Results on PEP-II measurement will be presented.
* Y. T. Yan, et. al. EPAC06 Proceedings, WEPCH062, (2006)
Jefferson Lab, Newport News, Virginia
Particle beam modeling in accelerators has been the focus of much effort (at great expense) since the 1950s. Several generations of tools have resulted from this process, each leveraging both the understanding provided by predecessors and the availability of increasingly powerful computer hardware. Nonetheless, the process remains on-going, in part due to innovations in accelerator design, construction, and operation that result in machines not easily described by existing tools. We discuss a novel response to this issue, which was encountered when Jefferson Lab began operation of its energy-recovering linacs. As such machines are not conveniently described using legacy software, a machine model was been built using Microsoft Excel. This interactive simulation can query data from the accelerator, use it to compute machine parameters, analyze difference orbit data, and evaluate beam properties. It can also derive new accelerator tunings and rapidly evaluate the impact of changes in machine configuration. As it is spreadsheet-based, it can be easily user-modified in response to changing requirements. Examples for the JLab IR Upgrade FEL are presented.
In this study, we analyze the longitudinal effective CSR force for an energy-chirped Gaussian bunch moving relativistically on a circular orbit. With the geometry of the bunch tilt in dispersive regions (as induced by the initial energy-chirp) included in the retardation relation, the longitudinal effective CSR force thus calculated displays a variety of behaviors depending on the level of bunch compression. The variety ranges from the suppression of the longitudinal CSR force, for an undercompressed thin bunch, to an enhancement of the CSR interaction above that for a projected bunch, in a duration of path length shortly after the bunch crosses over the full compression point. The amplitude and duration of the enhancement depends on the bunch and lattice parameters. During this enhancement, the longitudinal effective CSR force depends sensitively on the particle's transverse position in the bunch. The physical picture of this phenomenon will be discussed.
CERN, Geneva
The tight mechanical aperture for the LHC imposes severe constraints on both the beta and dispersion beating. Robust techniques to compensate these errors are critical for operation of high intensity beams in the LHC. We present simulations using realistic errors from magnet measurements and alignment tolerances in the presence of BPM noise. Correction reveals that the use of BPM calibration and model independent observables are key ingredients to accomplish optics correction. Experiments at RHIC to verify the algorithms for optics correction are also presented.
Polarized protons are injected into the Relativistic Heavy Ion Collider (RHIC) just above transition energy. When installation of a cold partial Siberian snake in the AGS required lowering the injection energy by Delta gamma=0.56, the transition energy in RHIC had to be lowered accordingly to ensure proper longitudinal matching. This paper presents lattice modifications implemented to lower the transition energy by ∆ γt=0.8.
IMCCE, Paris
CERN, Geneva
One of the main limitations for precise tune measurements using kicked turn-by-turn data is the beam decoherence, which can limit the available signal to a reduced number of turns. Applying Laskar's frequency analysis, on measurements from several beam position monitors, a fast and accurate determination of the real tune is possible. The efficiency of the method is demonstrated when applied in turn-by-turn data from the ESRF storage ring and CERN's Super Proton Synchrotron. Estimates from tracking simulations and analytical considerations are further compared with the experimental results.
KEK, Ibaraki
USTC/NSRL, Hefei, Anhui
A simple measurement method of beam bunch length in time domain for HLS (Hefei Light Source) has been proposed. The Bunch length measurement system is composed of an optical system, a high speed photo-receiver and a wide bandwidth oscilloscope. The photo-receiver which is made by FEMTO has high sensitivity and high bandwidth, which converts the synchrotron radiation light into electronic signal. The oscilloscope which is made by Tektronix is TDS7704B, which has a high bandwidth up to 7GHz and show the bunch length in time domain. The measurement results of the bunch length and its analysis are given. We compare the results with that determined by the conventional method using a streak camera.
CEA, Grenoble
CERN, Geneva
LBNL, Berkeley, California
CERN, Geneva
BNL, Upton, Long Island, New York
IFIC, Valencia
In recent years several measurements of the SPS non-linear chromaticity have been performed in order to determine the non-linear optics model of the SPS machine at injection energy for different cycles. In 2006 additional measurements have been performed at injection and during the ramp for the cycle used to accelerate the LHC beam. New and more robust matching algorithms have been developed in 2006 to fit the model to the measurements up to arbitrary chromatic order. In this paper we describe the algorithms used in the analysis of the data and we summarize and compare the results from all experiments.
ANL, Argonne, Illinois
NSWC, West Bethesda, Maryland
We have investigated the angular distribution patterns (far-field focus) of optical transition radiation (OTR) and optical diffraction radiation (ODR) generated by 7-GeV electron beams passing through and near an Al metal plane, respectively. The 70-μrad opening angles of the OTR patterns provide calibration factors for the system. Effects of the upstream quadrupole focusing strength on the patterns as well as polarization effects were observed. The OTR data are compared to an existing OTR single-foil model, while ODR profile results are compared to expressions for single-edge diffraction. ODR was studied with impact parameters of about 1.25 mm, close to the gamma λ?bar value of 1.4 mm for 628-nm radiation. We expect angle-pointing information along the x axis parallel to the mirror edge is available from the single-lobe ODR data as well as divergence information at the sub-100-μrad level. Experimental and model results will be presented.
To avoid multiple head-on collisions the proton and antiproton beams in the Tevatron move along separate helical orbits created by 7 horizontal and 8 vertical electrostatic separators. Still the residual long-range beam-beam interactions can adversely affect particle motion at all stages from injection to collision. With increased intensity of the beams it became necessary to modify the orbits in order to mitigate the beam-beam effect on both antiprotons and protons. This report summarizes the work done on optimization of the Tevatron helical orbits, outlines the applied criteria and presents the achieved results.
MSU, East Lansing, Michigan
Fermilab, Batavia, Illinois
ANL, Argonne, Illinois
UMD, College Park, Maryland
We have developed a new optical diffraction radiation (ODR) - dielectric foil radiation interferometer to measure the divergence of the low energy (8 - 14 MeV) ANL - Advanced Wakefield Accelerator electron beam. The interferometer employs an electro-formed micromesh first foil, which overcomes the inherent scattering limitation in the solid first foil of a conventional OTR interferometer, and an optically transparent second foil. The interference of forward directed ODR from the mesh and optical radiation from the dielectric foil is observed in transmission. This geometry allows a small gap between the foils (1 - 2 mm), which is required to observe fringes from two foils at low beam energies. Our measurements indicate that a single Gaussian distribution is sufficient to fit the data.
correspondance email: shkvar@umd.edu
SLAC, Menlo Park, California
Pavilion Technologies, Inc, Austin, Texas
The primary contributing factors to electron beam lifetime in a storage ring are elastic and inelastic gas scattering, and intrabeam scattering. In order to further quantify the relative contributions of each mechanism, a series of measurements using vertical scraper position and rf-voltage sweeps were performed in SPEAR3 with fill patterns featuring different single-bunch and total beam currents. In parallel, an analytic beam-lifetime simulator was developed taking scattering cross-sections, rf-bucket height and bunch lengthening effects into account. In this paper, we compare measured results with the simulated results in an effort to develop a comprehensive model for electron beam lifetime under a variety of operating conditions.
SLAC, Menlo Park, California
ANL, Argonne, Illinois
Life Imaging Technology, Palo Alto, California
In the nominal SPEAR3 storage ring optics, the natural radiation pulse length is 40ps fwhm per bunch. Due to the double-bend achromat lattice configuration, it is relatively straightforward to reduce the momentum compaction factor (α) and hence reduce the bunch length by modest values. In this paper we present streak camera measurements of the bunch length in the nominal optics, and with ~α/20 and α/50 optics as a function of single-bunch current. The results demonstrate <10ps fwhm radiation pulses with up 5x108 particles/bunch (~100μ amp). Radiation pulse power, bunch length scaling and broadband impedance estimates are discussed.
SLAC, Menlo Park, California
Wake fields defining beam stability affect also the beam optics and beam properties in high current machines. We present observations and analysis of the optical effects in the PEP-II SLAC B-factory, which has the record in achievement of high electron and positron currents. We study the synchronous phase and the bunch length variation along the train of bunches, overall bunch lengthening and effects of the wakes on the tune and on the Twiss parameters. This analysis is being used in upgrades of PEP II and may be applied to future B-factories and damping rings for Linear Colliders.
SLAC, Menlo Park, California
During the last PEP-II run a major goal was to bring the Low-Energy Ring optics as close as possible to the design. Sudden artificial jumps of the orbit, which were regularly observed by a large number of BPMs during routine operation, were interfering with this effort. The source of the majority of these jumps had been traced to the filter-isolator boxes (FIBs) near the BPM buttons. A systematic approach to find and repair the failing units had been developed and implemented. Despite this effort, the instrumental orbit jumps never completely disappeared. To trace the source of this behavior a test setup, using a spare Bergoz MX-BPM processor (kindly provided by SPEAR III at SSRL) was connected in parallel to various PEP-II BPM processors. In the course of these measurements a slow instrumental orbit drift was found which was clearly not induced by a moving positron beam. Based on the size of the system and the limited time before the end of PEP II an accelerator improvement project was initiated to install BERGOZ BPM-MX processors close to all sextupoles.
In earlier work related to the NSLS-II project we have outlined a control theory approach for the dynamic aperture problem. In particular, an algorithm for the joint optimization of the Lie generator and the working point for the Poincare map. This time we report on how the Lie generator provides guidelines on acceptable magnitudes for e.g. the intrinsic nonlinear effects from insertion devices, and the nonlinear pseudo-invariant can be used to optimize the dynamic aperture. We also show how a polymorphic beam line class can be used to study the parameter dependance and rank conditions for control of optics and dynamic aperture.
bengtsson@bnl.gov
BNL, Upton, Long Island, New York
With 8 arc sextupole families in each RHIC ring, the nonlinear chromaticities can be corrected on-line by matching the off-momentum tunes onto the wanted off-momentum tunes with linear chromaticity only. The Newton method with singular value decomposition (SVD) technique is used for this multi-dimensional nonlinear optimization, where the off-momentum tune response matrix with respect to sextupole strength changes is adopted to simplify and fasten the on-line optimization process. The off-momentum tune response matrix can be calculated with the on-line accelerator optics model or directly measured with the real beam. This correction method will be verified and used in the coming RHIC run'07.