BNL, Upton, Long Island, New York
Funding: Work supported by U.S. DOE, Contract No.DE-AC02-98CH10886
The NSLS-II light source is a proposed 3 GeV storage ring, with the potential for ultra-low emittance*. Despite the reduced emittance goal for the bare lattice, the closed orbit amplification factors are on average >50 in both planes, for random quadrupole alignment errors. The high chromaticity will also require strong sextupoles and the low 3 GeV energy will require large dynamic and momentum aperture to insure adequate lifetime. This will require tight alignment tolerances (~30microns) on the multipole magnets during installation. By specifying tight alignment tolerances of the magnets on the support girders, the random alignment tolerances of the girders in the tunnel can be significantly relaxed. Using beam based alignment to find the golden orbit through the quadrupole centers, the closed orbit offsets in the multipole magnets will then be reduced to essentially the alignment errors of the magnets, restoring much of the DA and lifetime of the bare lattice. Our R&D program to achieve these tight alignment tolerances of the magnets on the girders using a vibrating wire technique**, will be discussed and initial results presented.
*Work presented on behalf of the NSLS-II Design Team, CDR(2006) and CD2(2007).
**A. Jain, et al, International Workshop on Accelerator Alignment, Tsukuba, Japan, Feb.11-15, 2008.
USTC/NSRL, Hefei, Anhui
Funding: Work supported by National Natural Science Foundation of China (No.10175062 & 10575100).
In recent years, Fixed Field Alternating Gradient (FFAG) accelerator is becoming a highlight in particle accelerator R&D area. This type of accelerator could accelerate ions with higher beam current than conventional strong focusing circular accelerator, which could be more useful for the study of radioactive material. In this paper, conceptual design of an FFAG with high Helium ion beam current and a few MeV energy which is dedicated to study the impact of Helium embitterment to fusion reactor envelope material is discussed, the periodic focusing structure model is given, following which the calculation result of magnetic field is also presented.
CERN, Geneva
Following a series of injection tests, the first attempts to pass beam around both directions of the LHC were successful and led rapidly to circulating beam in the counter clockwise direction (beam 2) and many turns of beam 1. Unfortunately the beam commissioning was curtailed by the incident in sector 34. However, measurements performed during this first commissioning period should that the magnet model of the machine had delivered optics close to nominal, and also very good performance of beam instrumentation and supporting software. Details of the machine set-up and the commissioning procedures are detailed. The measurements performed and the key results from this period are described.
CERN, Geneva
The Large Hadron Collider (LHC) has been aligned using classical and non-standard techniques. The results have been seen on September 10th, 2008, the day when the beam made several turns in the machine with very few correctors activated. The paper will present the different steps of the alignment, from the metrological measurements done during the phase of the magnets assembly to the alignment itself in the tunnel as well as the techniques used to obtain the accuracy required by the physicists. The correlation of the results of this alignment with the position of the beam seen on the BPMs by the operation team during the days the beam has circulated will be presented.
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
KEK, Ibaraki
A fast local bump system for the helicity switching of a circular/linear polarized undulator (CPU) has been developed at the Photon Factory storage ring (PF-ring). The system consists of five identical bump magnets and tandem APPLE-2 type CPUs. In addition, fast correction magnets for a leakage of the bump were prepared. We designed the bump magnets with a core length of 0.15 m, a pole gap of 21 mm and the coils of 32 turns, which were excited by bipolar power supplies with a capacity of ±100 A and ±50 V since a switching frequency of more than 10 Hz and a bump angle of 0.3 mrad were required for user experiments. The bump magnets and one of CPUs were installed at PF-ring in March 2008, and the experiments for the machine development using a stored beam have been progressed. In this conference, we present the first experimental results with the bump system.
CERN, Geneva
The performance reach of the LHC depends on the magnitude of beam losses and the achievable cleaning efficiency of its collimation system. The ideal performance reach for the nominal Phase 1 collimation system is reviewed. However, unavoidable imperfections affect any accelerator and can further deteriorate the collimation performance. Multiple static machine and collimator imperfections were included in the LHC tracking simulations. Error models for collimator jaw flatness, collimator setup accuracy, the LHC orbit and the LHC aperture were set up, based to the maximum extent possible on measurements and results of experimental beam tests. It is shown that combined "realistic" imperfections can reduce the LHC cleaning efficiency by about a factor 11 on average.
CERN, Geneva
BNL, Upton, Long Island, New York
KEK, Ibaraki
For several years optics measurement and correction algorithms have been developed for the LHC. During 2008 these algorithms have been directly tested in the SPS and RHIC. The experimental results proving the readiness of the applications are presented.
Brunel University, Middlesex
CEA, Gif-sur-Yvette
The Non Scaling FFAG EMMA lattice allows a important displacement of the magnets in the radial direction. From this peculiarity, interesting studies of beam dynamics can be performed comparing simulated and experimental results. Being able to study a specific resonance, choosing a certain set of parameters for the lattice is really challenging. Simulations have been done integrating particle trajectories with Zgoubi through Magnetic Field Map created with OPERA. From a chosen tune evolution, one can find the corresponding magnets' configuration required by interpolating between a various sets of Field Map. Relative position and strength of the magnets are degrees of freedom. However, summing field maps requires a special care since the real magnetic field created by two magnets is not obviously linearly dependent on each single magnet. For this reason, frequently used hard edge and fringe field models may not be accurate enough. This linearity of the magnetic field has been studied directly through OPERA finite element method solutions and further on with Zgoubi tracking results.
Brunel University, Middlesex
STFC/RAL, Chilton, Didcot, Oxon
The University of Liverpool, Liverpool
The unconventional size and the possibility of transverse displacement of the magnets in the EMMA non-scaling FFAG motivates a careful study of particle behavior within the EMMA ring. The magnetic field map of the doublet cell is computed using a Finite Element Method solver; particle motion through the field can then be found by numerical integration, using (for example) OPERA, or ZGOUBI. However, by obtaining an analytical description of the magnetic field (by fitting a Fourier-Bessel series to the numerical data) and using a differential algebra code, such as COSY, to integrate the equations of motion, it is possible to produce a dynamical map in Taylor form. This has the advantage that, after once computing the dynamical map, multi-turn tracking is far more efficient than repeatedly performing numerical integrations. Also, the dynamical map is smaller (in terms of computer memory) than the full magnetic field map; this allows different configurations of the lattice, in terms of magnet positions, to be represented very easily using a set of dynamical maps, with interpolation between the coefficients in different maps*.
*yoel.giboudot@stfc.ac.uk
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
RHIC BPM system average orbit was originally calculated by averaging positions of 10000 consecutive turns for a single selected bunch. Known perturbations in RHIC particle trajectories, with multiple frequencies around 10 Hz, contribute to observed average orbit fluctuations. In 2006, the number of turns for average orbit calculations was made programmable; this was used to explore averaging over single periods near 10 Hz. Although this has provided an average orbit signal quality improvement, an average over many periods would further improve the accuracy of the measured closed orbit. A new continuous average orbit calculation is currently under development and planned for use in the 2009 RHIC run. This paper will discuss the algorithm, performance with a simulated beam signal, and beam measurements.
ELSA, Bonn
Acceleration of polarized electrons in a fast ramping circular accelerator poses challenging demands on the control and stabilization/correction of the closed orbit and the vertical betatron tune, in particular on the fast energy ramp. In order to successfully compensate depolarizing resonances at a ramping speed of up to 7.5 GeV/sec (dB/dt = 2 T/sec), at ELSA the closed orbit is stabilized with high precision using a system of Beam Position Monitors and steerer magnets distributed along the ring. During acceleration, the beam positions are read out from the BPMs at a rate of 1 kHz and energy-dependent orbit corrections are applied accordingly by means of offline feed-forward techniques. The system is thus sensitive to dynamic effects and an orbit stabilization of 100 microns rms is achieved routinely. At the same time, the betatron tunes are stabilized to 0.01 by time-resolved tune measurement and appropriate manipulations of the machine optics. This presentation will cover the concepts and implementation of techniques for orbit stabilization required for the acceleration of a polarized electron beam in the fast ramping stretcher ring ELSA.
Brunel University, Middlesex
STFC/RAL, Chilton, Didcot, Oxon
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
JAI, Oxford
The PAMELA project to design an accelerator for hadron therapy using non-scaling Fixed Field Alternating Gradient (NS-FFAG) magnets requires a transport line and gantry to take the beam to the patient. The NS-FFAG principle offers the possibility of a gantry much smaller, lighter and cheaper than conventional designs, with the added ability to accept a wide range of fast changing energies. This paper will build on previous work to investigate a transport line which could be used for the PAMELA project. The design is presented along with a study and optimisation of its acceptance.
GSI, Darmstadt
The GSI heavy ion synchrotron SIS18 will be used as a booster for the SIS100 synchrotron of the new FAIR facility. The linear corrections and measurements are a necessary step before the nonlinear field errors can be applied. A tune response to a change in a sextupole magnet strength for a certain Closed Orbit (CO) deformation is used to verify beta-functions of the SIS18 model at the location of the ring's sextupoles for chromaticity correction. The progress in development of Nonlinear Tune Response Matrix (NTRM) technique to diagnose nonlinear field components is presented.
BNL, Upton, Long Island, New York
The Touschek effect limits the lifetime for NSLS-II. The basic mechanism is Coulomb scattering resulting in a longitudinal momentum outside the momentum aperture. The momentum aperture results from a combination of the initial betatron oscillations after the scatter and the non-linear properties determining the resultant stability. We find that higher order multipole errors may reduce the momentum aperture, particularly for scattered particles with energy loss. The resultant drop in Touschek lifetime is minimized, however, due to less scattering in the dispersive regions. We describe these mechanisms, and present calculations for NSLS-II using a realistic lattice model including damping wigglers and engineering tolerances.
KEK, Ibaraki
KURRI, Osaka
Crossing of integer resonance in scaling FFAG accelerator has been studied experimentally with the injector of 150MeV FFAG complex at Kyoto University Research Reactor Institute (KURRI). The results were analyzed based on harmonic oscillator model and compared with beam tracking simulations.
LBNL, Berkeley, California
Funding: This work was supported by the Director, Office of Science, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
Frequency map analysis is being widely used, nowadays, both in simulations to design or improve accelerator lattices, as well as in experiments to study the transverse nonlinear dynamics in accelerators. A significant challenge to the use of frequency map analysis in experiments is the usually very fast decoherence of transverse oscillations, caused by the large nonlinearities of state-of-the-art lattices. Due to the decoherence, the center of mass oscillations of bunches often disappear in less than 100 turns. A potential way to get around this limitation is the use of multiple BPMs distributed (symetrically) around the storage ring. The presentation will describe the challenges multi-BPM frequency map analysis poses as well as initial results using the ALS.
SOLEIL, Gif-sur-Yvette
SOLEIL is the French 2.75 GeV high brilliance third generation synchrotron light source delivering photons to beam-lines since January 2007. Reaching micrometer to sub-micrometer level stability for the photon beams is then necessary but very challenging. Since September 2008, a fast orbit feedback has been running in daily operation. The performances of the system will be presented together with comparison with the ones previously achieved with the slow orbit feedback system. Status of the interaction of both feedback systems will be discussed. Moreover new X-BPMs have been installed on dipole and undulator based beam-lines; a total number of 9 vibration sensors (velocimeters) are now installed in the storage ring tunnel, on the experimental slab and outside the building in order to help to locate the different noise sources. Detailed results will be presented and debated.
LANL, Los Alamos, New Mexico
IUCF, Bloomington, Indiana
Funding: US DOE #DE-AC52-06NA25396
Orbit response matrix techniques have been used in numerous electron storage rings to elucidate various optical properties of the machines. Such measurements in a long-pulse accumulator ring have unique complications. We present here the techniques and results of such a measurement at the Los Alamos Proton Storage Ring*. We also show the deficiencies in previous models of the ring and a comparison of the beta-functions as fit by the orbit response method to direct measurements by quadrupole magnet variations.
*LA-UR- 08-07694
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Using an FFAG for rapid-cycling proton acceleration has the advantage that the acceleration cycle is no longer subject to constraints from the main magnet power supply used in an RCS. The RF can be used to its maximum potential to increase the energy range in a short 50Hz cycle as proposed for multi-MW proton driver projects. The challenge becomes an optical one of maintaining a stable lattice across a wide range of beam momenta without magnet sizes or the ring circumference making the machine prohibitively expensive for its purpose. Investigations of stable energy ranges for proton FFAG lattices in the few GeV regime (relativistic but not ultra-relativistic) are presented here.
USTC/NSRL, Hefei, Anhui
In order to meet the increasing requirements of synchrotron radiation users, a new plan of VUV and soft X-ray light source, named Hefei Advanced Light Source (HALS), is brought forward by National Synchrotron Radiation Laboratory (NSRL). This 1.5GeV storage ring with ultra low emittance 0.2nmrad consists of 18 combined FBA cells and the circumference is 388m. Strong enough quadrupoles and sextupoles must be needed for getting such low emittance lattice, which will lead beam close orbit distortions’ (COD) sensitivity to the field and alignment errors in magnets. Estimation of the COD from various error sources is investigated. Using orbit response matrix and singular value decomposition method, the distribution of beam position monitors and the location of correctors are reported in the paper. Simulation proves that COD can be corrected down to 60 microns level. In the same time the corrector strengths are weaker enough in the correction scheme.
YSU, Yerevan
CANDLE, Yerevan
PSI, Villigen
An online measurement of the beam energy spread is based on the analysis of the decoherence/recoherence signals obtained from the beam position monitors after a single turn beam excitation by a pinger magnet. Furthermore the analysis allows calibration of the model in terms of higher order chromaticities and amplitude dependant tune shifts. An analytical model including 1st and 2nd order chromaticities and amplitude dependant tune shift will be presented.
UMD, College Park, Maryland
Funding: This work is funded by the US Dept. of Energy Offices of High Energy Physics and High Energy Density Physics, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office.
Beam centroid control is an important method for optimizing the performance for accelerators, including the University of Maryland Electron Ring (UMER), which is a scaled low-energy (10KeV) storage ring. The conventional response matrix and singular value decomposition approach do not work well on the UMER because of the unique ring structure. One of the purposes of this work is to verify that the beam centroid could be controlled in the presence of very strong space charge. In this paper, we present a novel algorithm which is based on the singular value decomposition, but uses a different response matrix, which is computed from the closed equilibrium orbit and beam positions up to the first four turns in the multi-turn beam circulation. Other issues like strong coupling between the horizontal steering dipoles and vertical steering dipoles in the beam injection section will be addressed. Implementation of this algorithm leads to significant improvement on the beam positions and multi-turn operation.
CEA, Gif-sur-Yvette
Sigmaphi, Vannes
Imperial College of Science and Technology, Department of Physics, London
Funding: Agence Nationale de la Recherche, France, contract NT05-1_41853
A prototype of a spiral lattice FFAG magnet has been constructed in the frame of the RACCAM project*. THis magnet is subject to extensive field measurements and 3-dimensional field map measurements. The properties and qualities of the magnet are assessed directly from ray-tracing, using stepwise integration, for deriving lattice parameters as tunes, chromaticities, dynamic paertures, etc. Reporting on this is the subject of the poster.
*http://lpsc.in2p3.fr/service_accelerateurs/raccam.htm
TRIUMF, Vancouver
Fixed-Field Alternating-Gradient (FFAG) accelerators span a large range of momenta and have markedly different reference orbits for each momemtum. In the non-scaling (NS) versions proposed for rapid acceleration, the orbits are geometrically dissimilar. In particular, none of the orbits within bending magnets are arcs of circles and this complicates tune calculation. One approach to NS-FFAG design is to employ alternating combined-function magnets. Second generation NS-FFAGs designs attempt to mitigate the variation of betatron tunes; and careful calculation of orbits and tunes is essential. Starting from an analytic magnetic potential for the combined-function magnet, we elucidate expressions for orbit calculation which are second order in the cyclotron motion and arbitrary order in the momentum (no expansion is used).