LBNL, Berkeley, California
ICST, Harbin
Tests of the spectrometer solenoids have taught us some important lessons. The spectrometer magnet lessons learned fall into two broad categories that involve the two stages of the coolers that are used to cool the magnets. On the first spectrometer magnet, the problems were centered on the connection of the cooler 2nd-stage to the magnet cold mass. On the second spectrometer magnet, the problems were centered on the cooler 1st-stage temperature and the connections between leads, the cold mass support intercept, and the shields to the cooler first-stage. If the cooler 1st-stage temperature is too high, the refrigerator will not produce full 2nd stage cooling. If the 1st-stage temperature is too high, the temperature of the top of the HTS leads. As a result, more heat goes into the 4 K cold mass and the temperature margin of the top of the HTS leads is too small, which are in a magnetic field. The parameters that affect the magnet cooling are compared for the MICE coupling magnet and the spectrometer magnet.
SLAC, Menlo Park, California
The Cornell Electron Storage Ring (CESR) has been reconfigured as an ultra low emittance damping ring for use as a test accelerator (CesrTA) for International Linear Collider (ILC) damping ring R&D. One of the primary goals of the CesrTA program are to investigate the interaction of the electron cloud with low emittance positron beam, to explore methods to suppress the electron cloud, and to develop suitable advanced instrumentation required for these experimental studies. This paper report the simulation of the electron-cloud formation in the wiggler and quadrupole magnets using 3D code CLOUDLAND. The transverse distribution of electron cloud in a wiggler magnet is similar to a dipole magnet except in the zero vertical field regions where the electrons have complicated trajectories and therefore a longer lifetime. Fortunately, these electrons are dominantly direct-photo-electrons and can be easily reduced by properly arranging photon absorbers. Simulations show that the electron cloud in a quadrupole magnet can be trapped for long time due to the mirror field effect.
SLAC, Menlo Park, California
A new method, using the parabolic equation (PE), for the calculation of both high-frequency and small-angle taper (or collimator) impedances is developed in [1]. One of the most important advantages of the PE approach is that it eliminates the spatial scale of the small wavelength from the problem. As a result, the numerical solution of the PE requires coarser spatial meshes. We developed a new code based on Finite Element Method (FEM) which can handle arbitrary profile of a transition. As a first step, we completed and benchmarked a two-dimensional code. One of the important advantages of the code is its fast execution time.
KEK, Ibaraki
SLAC, Menlo Park, California
Grooved surfaces are effective to suppress the secondary electron emission, and can be a possible technique to mitigate the electron cloud instability (ECI) in positron/proton storage rings. Various types of triangular grooved surfaces have been studied in a laboratory, and also using an intense positron beam of the KEKB B-factory. The grooves have vertex angles of 20 ~ 30 degrees, and depths of 2.5 mm. In the laboratory, the secondary electron yield (SEY) of sample pieces were measured using an electron beam in a magnetic-free condition. The maximum SEY well below 1.0 was obtained after some extent of electron bombardment for most of grooved surfaces. To test he groove efficacy in magnetic field regions of particle accelerators, insertions with several types of grooved surfaces were installed into a test chamber in a wiggler magnet of KEKB positron ring. In a dipole-like chamber wit magnetic field (0.78 T), the reduction in the electron density around the beam was observed for a grooved section when compared to the case of a flat surface with TiN coating. An R&D effort is underway to optimize and manufacture the grooved surface in accelerator beam pipes for practical use.
SLAC, Menlo Park, California
PEP-X, a next generation, ring-based light source is designed to run with beams of high current and low emittance. Important parameters are: energy 4.5 GeV, circumference 2.2 km, beam current 1.5 A, and horizontal and vertical emittances, 150 pm by 8 pm. In such a machine it is important that impedance driven instabilities not degrade the beam quality. In this report we study the strength of the impedance and its effects in PEP-X. For the present, lacking a detailed knowledge of the vacuum chamber shape, we create a straw man design comprising important vacuum chamber objects to be found in the ring, for which we then compute the wake functions. From the wake functions we generate an impedance budget and a pseudo-Green function wake representing the entire ring, which we, in turn, use for performing instability calculations. In this report we consider in PEP-X the microwave, transverse mode-coupling, multi-bunch transverse, and beam-ion instabilities.
KEK, Ibaraki
SLAC, Menlo Park, California
In order to mitigate the electron cloud instability (ECI) in a positron ring, an electron clearing electrode with a very thin structure has been developed. The electrode has been tested with an intense positron beam of the KEKB B-factory using a test chamber. A drastic reduction in the electron density around the beam was demonstrated in a dipole magnetic field (0.78 T). The clearing electrode was then applied to the actual copper beam pipe (94 mm in diameter) with antechambers for wiggler magnets of KEKB. The feed-through was revised to improve reliability, and the length was modified to fit a real magnet. The input power into the electrode was estimated to be approximately 80 W/m. The clear reduction in the electron density was also observed by applying a voltage of +500 V to the electrode. The design of clearing electrodes has now reached a high reliability and it is suitable for accelerator applications.
CLASSE, Ithaca, New York
CERN, Geneva
Carleton University, College of Natural Sciences, Ottawa, Ontario
Purdue University, West Lafayette, Indiana
LBNL, Berkeley, California
Grove City College, Grove City, Pennsylvania
INFN/LNF, Frascati (Roma)
ASCo, Clayton, Victoria
KEK, Ibaraki
Clarkson University, Potsdam, New York
BNL, Upton, Long Island, New York
ANL, Argonne
CalPoly, San Luis Obispo, CA
Cockcroft Institute, Warrington, Cheshire
SLAC, Menlo Park, California
Fermilab, Batavia
Technion, Haifa
Loyola University, Chicago, Illinois
The Cornell Electron Storage Ring (CESR) has been reconfigured as a test accelerator (CesrTA) for a program of electron cloud (EC) research at ultra low emittance. The instrumentation in the ring has been upgraded with local diagnostics for measurement of cloud density and with improved beam diagnostics for the characterization of both the low emittance performance and the beam dynamics of high intensity bunch trains interacting with the cloud. Finally a range of EC mitigation methods have been deployed and tested. Measurements of cloud density and its impact on the beam under a range of conditions will be presented and compared with simulations. The effectiveness of a range of mitigation techniques will also be discussed.
CLASSE, Ithaca, New York
CERN, Geneva
ANL, Argonne
KEK, Ibaraki
SLAC, Menlo Park, California
Over the course of the CesrTA program, the Cornell Electron Storage Ring (CESR) has been instrumented with several retarding field analyzers (RFAs), which measure the local density and energy distribution of the electron cloud. These RFAs have been installed in drifts, dipoles, quadrupoles, and wigglers; and data have been taken in a variety of beam conditions and bunch configurations. This paper will provide an overview of these results, and give a preliminary evaluation of the efficacy of cloud mitigation techniques implemented in the instrumented vacuum chambers.
CLASSE, Ithaca, New York
LBNL, Berkeley, California
ANL, Argonne
CalPoly, San Luis Obispo, CA
SLAC, Menlo Park, California
The Cornell Electron Storage Ring Test Accelerator (CesrTA) program has included extensive measurements of coherent tune shifts for a variety of electron and positron beam energies, bunch current levels, and bunch train configurations. The tune shifts have been shown to result primarily from the interaction of the beam with the space-charge field of the beam-induced low-energy electron cloud in the vacuum chamber. Comparison to several advanced electron cloud simulation program packages has allowed determination of the sensitivity of these measurements to physical parameters such as the synchrotron radiation flux, its interaction with the vacuum chamber wall, the beam emittance and lattice optics, as well as to those of the various contributions to the electron secondary yield model. We report on progress in understanding the cloud buildup and decay mechanisms in magnetic fields and in field-free regions, addressing quantitatively the precise determination of the physical parameters of the modelling. Validation of these models will serve as essential input in the design of damping rings for future high-energy linear colliders.
SLAC, Menlo Park, California
Over the past year, we have worked out a baseline design for PEP-X, as an ultra-low emittance storage ring that could reside in the existing 2.2-km PEP-II tunnel. The design features a hybrid lattice with double bend achromat cells in two arcs and theoretical minimum emittance cells in the remaining four arcs. Damping wigglers reduce the horizontal emittance to 86 pm-rad at zero current for a 4.5 GeV electron beam. At a design current of 1.5 A, the horizontal emittance increases, due to intra-beam scattering, to 164 pm-rad when the vertical emittance is maintained at a diffraction limited 8 pm-rad. The baseline design will produce photon beams achieving a brightness of 1022 (ph/s/mm2/mrad2/0.1% BW) at 10 keV in a 3.5-m conventional planar undulator. Our study shows that an optimized lattice has adequate dynamic aperture, while accommodating a conventional off-axis injection system. In this paper, we will present the study of the lattice properties, nonlinear dynamics, intra-beam scattering and Touschek lifetime, and collective instabilities. Finally, we discuss the possibility of partial lasing at soft X-ray wavelengths using a long undulator in a straight section.
SLAC, Menlo Park, California
LBNL, Berkeley, California
CLASSE, Ithaca, New York
INFN/LNF, Frascati (Roma)
ANL, Argonne
Cockcroft Institute, Warrington, Cheshire
KEK, Ibaraki
CERN, Geneva
As part of the International Linear Collider (ILC) collaboration, we have compared the electron cloud effect for different Damping Ring designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of a shorter damping ring with respect to the electron cloud build-up and related beam instability. These studies were carried out with beam parameters of the ILC Low Power option. A reduced damping ring circumference has been proposed for the new ILC baseline design and would allow to considerably reduce the number of components, wiggler magnets and costs. We also briefly discuss the plans for future studies including the luminosity upgrade option with shorter bunch spacing, the evaluation of mitigations and the integration of the CesrTA results into the Damping Ring design.
USTC/NSRL, Hefei, Anhui
In order to obtain more straight sections for insertion devices and higher brilliance synchrotron radiation, an upgrade project of Hefei Light source (HLS) is undergoing. A new injection system has been designed to improve injection efficiency and keep the machine running stably. Four kickers will be used to generate a local injection bump. Effects of injection system to injecting beam and stored beam have been simulated considering errors. Finally, ELEGANT code was used to simulate the injection process with new designed bump system. The simulation results show that the injection efficiency would be higher than 99% and perturbation on stored beam would be small enough, which are benefit to full energy injection and top-up operation of HLS in the future.
USTC/NSRL, Hefei, Anhui
Hefei Advanced Light Source(HALS) will be a high brightness light source with about 0.2nmrad emittance at 1.5GeV and about 400m circumference. To enhance brilliance, very low beam emittance is required. High brightness demand and relative low energy will make emittance a critical issue in ring design. Intra-beam scattering(IBS) is usually thought a fundamental limitation to achieve low emittance. Here we preliminarily estimate the emittance growth due to IBS for the temporary lattice design of HALS based on Piwinski and Bjorken-Mtingwa theories, and discuss the effect of implementation of damping wiggler and harmonic cavity to lower the emittance.
USTC/NSRL, Hefei, Anhui
HLS (Hefei Light Source) is a dedicated synchrotron radiation research facility, whose emittance is relatively large. In order to improve performance of the machine, especially getting higher brilliance synchrotron radiation and increasing the number of straight sections for insertion devices, an upgrade project is on going. A new low emittance lattice, which keeps the circumference of the ring no changing, has been studied and presented in this paper. For the upgrade project, a new ring will be installed on current ground settlement of HLS and all of the magnets will be reconstructed. After optimization, two operation modes have been chosen for different users. Nonlinear dynamics shows that dynamic aperture for on-momentum and off-momentum particle is large enough. Beam lifetime has also been studied. Calculation results proves that expected beam lifetime about 8.5 hours can be obtained with a fourth harmonic cavity operation.
USTC/NSRL, Hefei, Anhui
The Hefei Light Source is composed of an 800 MeV storage ring, a 200 MeV electron linac and transfer line, which was designed and constructed twenty years ago. Several factors limit the performance of HLS, for example, less number of insertion devices and large beam emittance. To meet the requirements of synchrotron radiation users, an upgrade project of HLS will be carried out in the next two years. Several sub-systems will be renewed, such as magnet system, power supply, beam diagnostics, vacuum system, etc. The upgrade scheme is described in this paper, including magnet lattice design, nonlinear performance, collective effects,beam injection, orbit detection and correction, injector, etc.
USTC/NSRL, Hefei, Anhui
UW-Madison/SRC, Madison, Wisconsin
A radio frequency system with a higher-harmonic cavity will be used to increase the beam lifetime and suppress coupled-bunch instabilities of the upgrade Hefei Light Source. In the paper, the simulated results confirm that tuning in the harmonic cavity may suppresses the parasitic coupled-bunch instabilities. The higher-harmonic cavity has been designed and the calculated optimum lifetime increase ratio is 2.58.
USTC/NSRL, Hefei, Anhui
Low emittance is a desirable performance for high brightness synchrotron light source and damping ring. The work presented in this paper demonstrates that the lattice of a given electron storage ring, which has fixed circumference and magnet layout, can be optimized to obtain low emittance by using MOGA (Multi-objective Genetic Algorithm). Both dispersion-free and non-dispersion-free lattices of HLS (Hefei Light Source) upgrade project are computed as an illustration. Simulation result shows that this method is fast and straightforward.
USTC/NSRL, Hefei, Anhui
In order to meet the increasing requirements of synchrotron radiation users, an upgrading plan of hefei light source is undergoing by National Synchrotron Radiation Laboratory (NSRL). The emittance of storage ring is reduced from 166nm.rad to 36nm.rad. In this paper, we study the beam close orbit distortions' (COD) sensitivity to the field and alignment errors in magnets. Estimation of the COD from various error sources is investigated. 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 50 microns level. In the same time the corrector strengths are weaker enough in the correction scheme.
USTC/NSRL, Hefei, Anhui
To enhance the performance of Hefei Light Source, an upgrade project is undergoing. The magnet lattice of storage ring will be reconstructed with 4 DBA cells, whose advantages are lower beam emittance and more straight section available for insertion devices. In order to assure smooth beam accumulation process under new low emittance lattice, the injector, which is composed of electron linac and beam transfer line, would be updated. The detail of upgrading Hefei Light Source transport line will be described in this paper. It include the upgrading of lattice, the orbit control of beam transfer line and others. It is hopeful to realize a high transfer efficiency and high injection efficiency for new lower beam emittance storage ring.