CLS, Saskatoon, Saskatchewan
Upgrades to the orbit control system at the Canadian Light Source (CLS) have resulted in increased beam stability and reproducibility. These upgrades include improving position information from the beam position monitors (BPMs) by modifying the data acquisition algorithm and switching to a real-time operating system. Beam motion has been reduced to an RMS deviation of less than 1 micron in both planes. Limiting the maximum corrector step has allowed the use of all singular values when inverting the BPM response matrix, resulting in much better orbit reproducibility. As well, improved lookup tables have been developed to compensate for the effects of changing undulator gaps and polarizations. Presently, work is underway to develop fast orbit correction with rates up to 100 Hz. Fast orbit correction will further reduce the residual perturbations caused by undulator activity and will allow fast ramping of superconducting wigglers.
IHEP Beijing, Beijing
Funding: Work supported by National Natural Science Foundation of China contract 10725525
The upgraded project of the Beijing Electron-Positron Collider (BEPCII) can be operated not only for high energy physics experiments as a charm factory, but for synchrotron radiation users as a first generation light source. The design of the synchrotron radiation (SR) mode of the BEPCII storage ring keeps all the original beam lines of the BEPC. The lattice based on the layout of the collider can meet all the requirements of the SR users, and the emittance is minimized. Optimization of the SR mode focuses on reducing the effects from wigglers around the ring. Some results from the operations of the SR mode are also given.
JASRI/SPring-8, Hyogo-ken
An ultra-low emittance storage ring with an energy of 6 GeV was proposed as a next generation synchrotron radiation source*. The storage ring has the same circumference as that of SPring-8 storage ring so as to be able to replace the existing storage ring, but has not four long straight sections. Accordingly, the storage ring beam line is slightly different from that of SPring-8 and the positions of photon beam lines are also different from the existing one. To avoid this, a storage ring with four long straight sections has been designed. The beam line position of the new storage ring is the same as the existing one. The storage ring consists of twenty ten-bend achromat cells, four five-bend achromat cells and four long straight sections. The long straight section length is 34.0 m and the short one is 6.6 m. The natural emittance is less than 100 pm-rad. In the paper, the dynamic aperture problem is discussed and the other ring characteristics are presented.
*K. Tsumaki and N. Kumagai, EPAC’06, 3362.
LSU/CAMD, Baton Rouge, Louisiana
CAEP/IFP, Mainyang, Sichuan
At the CAMD Light Source a new optic has been developed for the lattice having small vertical beta function in each of the 4 long straight sections. This optic will be necessary to operate the multipole wigglers with small vertical aperture which are planned to be installed in the near future. Results are presented of the tests which have been made with this optic, particularly in the critical area of injection, which is made low energy. The lattice functions have been characterized using LOCO software and the reduced vertical aperture confirmed with an adjustable scraper.
FEL/Duke University, Durham, North Carolina
PKU/IHIP, Beijing
Funding: Work supported by US Air Force Office of Scientific Research medical FEL grant FA9550-04-01-0086.
The storage ring based free electron laser (FEL) oscillator serves as a photon driver for the High Intensity Gamma-Ray Source (HIGS) at Duke University. The FEL cavity consists of two concave mirrors with a large radius of curvature of more than 27 m. Both cavity mirrors see very high intensity intracavity FEL power; the downstream mirror also receives higher harmonic spontaneous UV-VUV radiation of wigglers. The large heat load by various types of radiation can deform the mirror surface, causing FEL mode distortion. The FEL mirror can also be damaged by intense UV-VUV wiggler harmonic radiation. To mitigate these problems, a pair of water-cooled, in-vacuum apertures have been installed inside the FEL cavity. These apertures are ideal for manipulating the FEL transverse profile. This paper reports our study on the FEL transverse mode shaping using these apertures, including the characterization of the transverse mode structure of the FEL beam under a variety of operation conditions. These studies allow us to minimize the diffraction loss of the fundamental mode of the FEL while effectively reducing the impact of off-axis UV-VUV wiggler radiation on the FEL mirrors.
FEL/Duke University, Durham, North Carolina
Funding: This work is supported by US Air Force Office of Scientific Research medical FEL grant FA9550-04-01-0086.
The paper presents a novel technique of measuring the gain of a storage ring based FEL oscillator. As opposed to the conventional technique of measuring the FEL gain from its macro-pulse envelope, this new technique is based upon the measurement of pass-by-pass FELμpulses. To record the growth of the optical energy in the FEL micro-pulse train, we use fast photo-diodes and photo-multiplier tubes (PMTs). PMTs are usually employed at the very beginning of the FEL lasing development, while the photodiodes are used at the latter stages when the FEL power is fully developed and saturated. This new gain measurement technique provides a powerful tool to study the details of the FEL gain process starting from spontaneous radiation to saturation. It allows us to investigate five to seven orders of magnitude of the FEL energy growth. As fast photo-detectors with a sub-nanosecond time response become available, this new technique can be adopted for many oscillator FELs, including those driven by super-conducting linacs. Special attention is paid to the dynamic non-linearity issues of the photodiodes and PMTs associated with short length of FEL pulses.
FEL/Duke University, Durham, North Carolina
Funding: This work is supported by US Air Force Office of Scientific Research medical FEL grant FA9550-04-01-0086 and US Department of Energy grant DE-FG02-01ER41175.
The Duke Free-Electron Laser Laboratory (DFELL) operates several accelerators as a driver for storage ring based Free-Electron Lasers (FELs) and Compton gamma-ray source, the High Intensity Gamma-ray Source (HIGS). The HIGS is the most powerful Compton gamma-ray source in the world below 100 MeV. Since completing a major upgrade of the HIGS in 2007, the Duke storage ring FEL and HIGS gamma source have been operated extensively for user research programs. In 2008, the DFELL was merged with the Triangle Universities Nuclear Laboratory (TUNL) to become a major accelerator facility of the TUNL. The accelerator physics program at the DFELL covers a wide range of activities, from nonlinear dynamics research, to the study of beam instability with advanced feedback systems, to light source research and development, in particular, the FEL research and Compton light source development. In this paper, we will report our recent progress in accelerator physics research and light source development to meet new challenges of today's and future accelerators.
FEL/Duke University, Durham, North Carolina
Funding: This work was supported by US Department of Defense Medical FEL Program as administered by the AROSR under contract number FA9550- 04-01-0086 and US Department of Energy grant DE-FG05-91ER40665.
Accurate simultaneous measurements of storage ring free-electron laser (SRFEL) average power output and electron beam energy spread has been achieved at the Duke FEL Laboratory. It is well known that the SRFEL power is limited by the electron beam synchrotron radiation power and the induced energy spread of the electron beam. The two-wiggler spectrum of an optical klystron can be used to determine the energy spread of the electron beam. Measuring the interference pattern of the modulated spontaneous spectrum with the FEL turned on, we are able to study the FEL power output as a function of electron beam energy spread. As the energy spread increases, the modulation in the two-wiggler spectrum reduces, resulting in a smaller FEL gain. During this process, the operation of an optical klystron degrades back to that of a conventional FEL. This paper reports our recent experiment study of transition of the FEL operation from an optical klystron to a conventional FEL.
LBNL, Berkeley, California
LLNL, Livermore, California
SLAC, Menlo Park, California
Funding: This work was supported by the Office of Science, U. S. Department of Energy, under Contract No. DE-AC02-05CH11231.
A new set of resonances for electron cloud dynamics in the presence of a magnetic field has been found. For short beam bunch lengths and low magnetic fields where lb << 2*π/ωc, (lb = bunch duration, ωc = non-relativistic cyclotron frequency) resonances between the bunch frequency and harmonics of the cyclotron frequency cause an increase in the electron cloud density in narrow ranges of magnetic field near the resonances. For ILC parameters the increase in the density is up to a factor of approximately 3, and the spatial distribution of the electrons is broader near resonances, lacking the well-defined density "stripes" of multipactoring found for non-resonant cases. Simulations with the 2D computer code POSINST, as well as a single-particle tracking code, were used to elucidate the physics of the dynamics. The resonances are expected to affect the electron cloud dynamics in the fringe fields of conventional lattice magnets and in wigglers, where the magnetic fields are low. Results of the simulations, the reason for the bunch-length dependence, and details of the dynamics will be discussed.
C.M. Celata is presently also a visitor in Physics, Mathematics, and Astronomy at California Institute of Technology.
LNLS, Campinas
UVX is a 1.37 GeV electron storage ring at the Brazilian Synchrotron Light Laboratory (LNLS). The ring is composed of a 6-fold symmetric double-bend achromat lattice with 4 sections reserved for insertion devices. The storage ring was commissioned in 1997 in a mode of operation with high (~12 m) vertical betatron functions in the insertion straights. However, the need for operation with reduced vertical aperture arose with the gradual installation of insertion devices over the years and is particularly important for operation with a 14 mm vertical aperture superconducting wiggler scheduled for installation in late 2009. To cope with this restricted aperture, a new mode with low (~0.8 m) vertical betatron function in all six long straights was deemed necessary and was implemented at the end of 2008. In this report we present the commissioning results of the low vertical beta mode and the advantages in operating in this mode with insertions.
USTC/NSRL, Hefei, Anhui
Hefei Light Source is a second generation VUV light source, whose performance cannot meet the requirements of synchrotron radiation users at the present time. One year ago, the concept of the Hefei Advanced Light Source, whose main features are ultra low beam emittance and high brilliance in VUV and soft X-ray range, was brought forward. In the preliminary design study, a medium scale storage ring and multi bend achromat focusing structure were adopted to achieve beam emittance lower than 0.2 nm.rad. Linear and nonlinear parameter optimizations were performed to obtain large on-momentum and off-momentum dynamic aperture. The design status will be introduced briefly in the presentation.
BNG, Würzburg
KIT, Karlsruhe
FZK, Karlsruhe
University Erlangen-Nuernberg, Erlangen
Superconducting insertion devices (IDs) are very attractive for synchrotron light sources since they allow increasing the flux and/or the photon energy with respect to permanent magnet IDs. Babcock Noell GmbH (BNG) is completing the fabrication of a 1.5 m long unit for ANKA at FZK. The period length of the device is 15 mm for a total of 100.5 full periods plus an additional matching period at each end. The key specifications of the system are: a K value higher than 2 and the capability of withstanding a 4 W beam heat load and a phase error of 3.5 degrees. In addition, during the injection phase of the machine, the nominal gap of 5 mm can be increased up to 25 mm. The magnets have been tested with liquid helium in a vertical dewar and are now being installed in the cryostat. This paper describes the technical design concepts of the device and the status of the assembly process.
SOLEIL, Gif-sur-Yvette
BNL, Upton, Long Island, New York
SOLEIL storage ring presents a very high fraction of the total circumference dedicated to accommodate insertion devices. Over the presently planned 25 insertion devices presenting a large variety of systems, 15 have been already installed and commissioned by the end of 2008. The UV-VUV region is covered with electromagnetic devices (one HU640 and 3 HU256), offering tuneable polarisations. An electromagnet/permanent magnet undulator using copper sheets as coils for fast switching of the helicity is under construction. 13 APPLE-II types undulators, with period ranging from 80 down to 36 mm, provide photons in the 0.1-10 keV region, some of them featuring tapering or quasi-periodicity. 5 U20 in-vacuum undulators cover the 3-30 keV range whereas an in-vacuum wiggler, with magnetic forces compensation via adequate springs is designed to cover the 10-50 keV spectral domain. R&D on cryogenic in-vacuum undulator has also been launched. A magnetic chicane using permanent magnet dipoles has also been designed in order to accommodate two canted undulators on the same straight section. The processes for optimizing the insertion devices and their achieved performances will be described.
KIT, Karlsruhe
CERN, Geneva
FZ Karlsruhe, Karlsruhe
NbTi wires are relatively easy to handle and are therefore up to now the preferred material for superconductive insertion devices. Yet other materials, like Nb3Sn, MgB2 or high temperature superconductors, are less sensitive to beam heat load and/or are able to produce higher magnetic fields. In this paper the different superconducting materials and their advantages and challenges are discussed. Additionally this paper describes new designs for special insertion devices like damping wigglers and undulators for laser wakefield accelerators.
KIT, Karlsruhe
FZK, Karlsruhe
University Erlangen-Nuernberg, Erlangen
Recently a new concept for automatically reducing magnetic field errors in superconductive undulators was proposed. According to this proposal the field errors are compensated by an array of coupled high temperature superconductor loops attached to the surface of the superconductive undulator. The field errors induce currents in the coupled type II-superconducting loops and, as a result, the magnetic field generated by these currents minimizes the field errors. In this paper the results of a first successful experimental test of this concept are described.
CLASSE, Ithaca, New York
Funding: Work supported by the National Science Foundation and the US Department of Energy
The Cornell Electron Storage Ring has been reconfigured as a test accelerator (CesrTA) for the investigation of the beam physics of a linear collider damping ring. The low beta interaction region optics have been replaced with simple FOFO lattice structures. Superconducting damping wigglers are located in straights where horizontal dispersion can be constrained to be zero to minimize horizontal emittance. The flexibility of the CESR optics allows for an energy reach of 1.5 GeV /beam→ 6.0GeV/beam and a wide range of emittances and radiation damping times. We exploit that flexibility for measurements of the dependencies of various phenomena, on energy, emittance, and damping rate. At 2GeV beam energy, with no damping wigglers, the minimum horizontal emittance is 10nm. With 16 meters of wiggler magnets operating at 1.9 T, the horizontal emittance is reduced by a factor of four to 2.5 nm and the radiation damping time to 56ms. With tuning and alignment we expect to reach a vertical emittance approaching that of the International Linear Collider (ILC) damping rings. We report on the details of the CesrTA optics and the measurements of optical parameters.
CERN, Geneva
BINP SB RAS, Novosibirsk
INFN/LNF, Frascati (Roma)
Optics design optimisation studies have been undertaken for the CLIC damping ring lattice. Main parameters such as the ring energy and output longitudinal emittance were reconsidered in order to reduce the detrimental effect of collective instabilities. In this respect, the low emittance arc cell length was rationalized taking into account space and magnet design requirements. The straight section cell filled with super-conducting wigglers was modified to accommodate a robust absorption scheme. Several low emittance rings were considered and compared with respect to their dynamic aperture and the IBS-dominated output emittances.
National Technical University of Athens, Zografou
CERN, Geneva
The CLIC pre-damping rings have to accommodate a large emittance beam, coming in particular from the positron target and reduce its size to low enough values for injection into the main damping rings. In particular, polarized positron stacking imposes stringent requirements with respect to longitudinal acceptance and damping times. Linear lattice design options based on low-emittance cells, multiple bend cells and the inclusion of damping wigglers are compared with respect to linear optics functions, tunability, chromatic properties and acceptance. The optics of special regions for the placement of injection, extraction and RF elements are also presented. Non-linear dynamics simulations are finally undertaken for evaluating and maximizing the rings dynamic aperture, especially for large momentum spreads.
JLAB, Newport News, Virginia
Funding: Work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the Air Force Research Laboratory, and by the DOE Contract DEAC05-84ER40150.
As the only currently operating free electron laser (FEL) based on a CW superconducting energy recovering linac (ERL), the Jefferson Laboratory FEL Upgrade remains unique as an FEL driver. The present system represents the culmination of years of effort in the areas of SRF technology, ERL operation, lattice design, high power optics and DC photocathode gun technology. In 2001 the FEL Demo generated 2.1 kW of laser power. Following extensive upgrades, in 2006 the FEL Upgrade generated 14.3 kW of laser power breaking the previous world record. The FEL Upgrade remains a valuable testbed for studying a variety of collective effects, such as the beam breakup instability, longitudinal space charge and coherent synchrotron radiation. Additionally, there has been exploration of operation with lower injection energy and higher bunch charge. Recent progress and achievements in these areas will be presented, and two recent milestones installation of a UV FEL and establishment of a DC gun test stand will be discussed. Additionally, a review of the longitudinal matching scheme and the use of incomplete energy and its implications will be presented.
FEL/Duke University, Durham, North Carolina
TUNL, Durham, North Carolina
Funding: This work is supported by US Air Force Office of Scientific Research medical FEL grant FA9550-04-01-0086 and by US Department of Energy grant DE-FG02-01ER41175.
Since 2008, the upgraded High Intensity Gamma-ray Source (HIGS) at the Duke FEL Lab has provided users with gamma beams of unprecedented quality for scientific research. The recently completed accelerator upgrades include a HOM-damped RF cavity, a full-energy top-off booster injector, redesigned storage ring straight sections, and two new FELs. The HIGS facility is now capable of producing a high intensity gamma beam in a wide energy range (1 - 100 MeV) using commercial FEL mirrors. It has achieved an exceptionally high flux, up to ~1010 g/s total (< 20 MeV), making it the world's most powerful Compton gamma source. It produces almost 100% polarized gammas, either linear or circular. At the HIGS, the gamma energy can be changed rapidly within a factor of three in minutes. Operated by Triangle Universities Nuclear Laboratory since summer 2008, the HIGS is a dedicated Compton gamma source, capable of producing more than 2,000 h of gamma beam time per year with a five-day, two-shift schedule. Future development at the HIGS includes higher energy gamma beams toward the pion threshold and a rapid switch of circular polarization.
BNL, Upton, Long Island, New York
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract DE-AC02-98CH10886.
The NSLS-II Light Source being built at Brookhaven National Laboratory is expected to provide very small emittances and electron beam sizes. High resolution imaging systems are required in order to provide robust measurements. The pinhole cameras will utilize 5-fold magnification with a pinhole placed inside a crotch absorber. The pinhole is protected from high power synchrotron radiation with a filter made of refractory metal. In this paper we provide resolution analyses, heat load calculations, and optimization of NSLS-II pinhole cameras including beamline design.
CLASSE, Ithaca, New York
LBNL, Berkeley, California
KEK, Ibaraki
SLAC, Menlo Park, California
Funding: Work supported by the National Science Foundation, the US Department of Energy, and the Japan/US Cooperation Program
Wiggler magnets are one of the key components in the ILC Damping Ring. It is critical to the ILCDR GDE to understand electron cloud (EC) growth and patterns, and to develop EC suppression techniques in the wiggler beampipes. The CESR-c superconducting wigglers, closely matching the parameters of the ILCDR wigglers, serve as unique testing vehicles. As part of the CesrTA project, we replaced the copper beampipes of two SCWs with EC diagnostic beampipes, where one of the beampipes is uncoated and the second is coated with a thin TiN film. Each of the EC diagnostic beampipes is equipped with three retarding field analyzers (RFAs) at strategic longitudinal locations in the wiggler field. Each of the RFAs has 12-fold segmentation to measure the horizontal EC density distribution. To maintain sufficient vertical beam aperture and to fit within the SCW warm bore, a thin style of RFA (with a thickness of 2.5 mm) has been developed and deployed. These SCWs with RFA-equipped beampipe have been installed and successfully operated in the re-configured CesrTA vacuum system. This paper describes the design and the construction of the RFA-equipped SCW beampipes and operational experience.
CLASSE, Ithaca, New York
Funding: Support provided by the US National Science Foundation and the US Department of Energy.
A central component of the operation of the Cornell Electron Storage Ring as a Test Accelerator (CesrTA) for ILC Damping Rings R&D is the characterization of electron cloud growth in each of the principal vacuum chamber types in use in the storage ring. In order to facilitate measurements in chambers with tightly constrained external apertures, retarding field analyzers have been developed that can be deployed in regions with as little as 3mm of available aperture. We report on the design, fabrication, characterization and operation of devices that are presently deployed in CESR drift, dipole, and wiggler chambers.
The University of Liverpool, Liverpool
Cockcroft Institute, Warrington, Cheshire
Analytic descriptions of arbitrary magnetic fields can be calculated from the generalised gradients* of the on-axis field. Using magnetic field data, measured or computed on the surface of a cylinder, the generalised gradients can be calculated by solving Laplace's equation to find the three-dimensional multipole expansion of the field within the cylinder. After a suitable transformation, this description can be combined with a symplectic integrator allowing the transfer map to be calculated. A new tracking code is under development in C++, which makes use of a differential algebra class to calculate the transfer map. The code has been heavily optimised to give a fast, accurate calculation of the transfer map for an arbitrary field. The multipole nature of the field description gives additional insights into fringe-field and pseudo-multipole effects and allows a deeper understanding of the beam dynamics.
*Venturini M. and Dragt A., NIM Phys. Res. Sect. A, 427, 387 (1999)
UMD, College Park, Maryland
Funding: DOE grant DEFG02-96ER40949
Transfer maps for magnetic elements in storage and damping rings can depend sensitively on nonlinear fringe-field and high-order-multipole effects. The inclusion of these effects requires a detailed and realistic model of the interior and fringe magnetic fields, including their high spatial derivatives. A collection of surface fitting methods has been developed for extracting this information accurately from 3-dimensional magnetic field data on a grid, as provided by various 3-dimensional finite element field codes. The virtue of surface methods is that they exactly satisfy the Maxwell equations and are relatively insensitive to numerical noise in the data. These techniques can be used to compute, in Lie-algebraic form, realistic transfer maps for LHC final-focus quadrupoles and for the proposed ILC Damping Ring wigglers. An exactly-soluble but numerically challenging model field is used to provide a rigorous collection of performance benchmarks.
CLASSE, Ithaca, New York
LBNL, Berkeley, California
KEK, Ibaraki
ANL, Argonne
Fermilab, Batavia
CalPoly, San Luis Obispo, CA
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
SLAC, Menlo Park, California
Cornell University, Ithaca, New York
Cockcroft Institute, Warrington, Cheshire
Funding: Support provided by the US National Science Foundation, the US Department of Energy, and the Japan/US Cooperation Program.
In March of 2008, the Cornell Electron Storage Ring (CESR) concluded twenty eight years of colliding beam operations for the CLEO high energy physics experiment. We have reconfigured CESR as an ultra low emittance damping ring for use as a test accelerator (CesrTA) for International Linear Collider (ILC) damping ring R&D. The primary goals of the CesrTA program are to achieve a beam emittance approaching that of the ILC Damping Rings with a positron beam, to investigate the interaction of the electron cloud with both low emittance positron and electron beams, to explore methods to suppress the electron cloud, and to develop suitable advanced instrumentation required for these experimental studies (in particular a fast x-ray beam size monitor capable of single pass measurements of individual bunches). We report on progress with the CESR conversion activities, the status and schedule for the experimental program, and the first experimental results that have been obtained.
SLAC, Menlo Park, California
We describe a set of tools that interface to the Tracy particle tracking library. The state of the machine including misalignments, multipole errors and corrector settings is captured in a 'flat' file, or 'machine' file. There are three types of tools designed around this flat file: 1) flat file creation tools. 2) flat file manipulation tools. 3) tracking tools. We describe the status of these tools, and give some examples of how they have been used in the design process for NSLS-II.
CLASSE, Ithaca, New York
LBNL, Berkeley, California
ANL, Argonne
KEK, Ibaraki
SLAC, Menlo Park, California
Funding: Supported by the US National Science Foundation, the US Department of Energy under Contracts No. DE-AC02-06CH11357, DE-AC02-05CH11231, and DE-AC02-76SF00515, and by the Japan/US Cooperation Program.
CESR at Cornell has been operating as a damping ring test accelerator (CesrTA) with beam parameters approaching those anticipated for the ILC damping rings. A core component of the research program is to fully understand electron cloud effects in CesrTA. As a local probe of the electron cloud, several segmented retarding field analyzers (RFAs) have been installed in CesrTA in dipole, drift and wiggler regions. Using these RFAs, the energy spectrum of the time-average electron cloud current density striking the walls has been measured for a variety of bunch train patterns; with bunch populations up to 2x1010 per bunch, beam energies from 2 to 5 GeV, horizontal geometric emittances from roughly 10 to 133 nm, and bunch lengths of about 1 cm; and for both positron and electron beams. The effect of mitigation measures, such as coatings, has also been studied. This paper will compare these measurements with the predictions of simulation programs, and discuss the implications of these comparisons for our understanding of the physics of electron cloud generation and mitigation in ILC-like damping rings.
KEK, Ibaraki
SLAC, Menlo Park, California
Funding: The Japan/US Cooperation Program
Beam instability caused by the electron cloud is expected to be a limiting factor in the performance of future advanced positron and proton storage rings. In a wiggler section of the positron ring of the KEK B-factory (KEKB), we have installed a vacuum chamber with an insertion that can be replaced and including different techniques to study the mitigation of the electron-cloud effect in a high magnetic field region. We have installed an insertion with strip-line clearing electrode, an insertion with triangular grooves and an insertion with a smooth surface, and compared them each other under the same conditions. The electrode insertion is composed of a thin tungsten layer formed on a thin alumina ceramic layer. The groove insertion is composed of TiN-coated triangular grooves running longitudinally. In this paper, we report about the tests in the KEKB and about the large reduction in the measured electron cloud density when the clearing electrode and groove sections are installed with respect to the smooth insertion. These experiments are the first ones demonstrating the principle of the clearing electrode and groove insertions in a magnetic field.
INFN/LNF, Frascati (Roma)
KEK, Ibaraki
Funding: Work supported in part by the “Ministero degli Affari Esteri, Direzione Generale per la Promozione e la Cooperazione Culturale”
A strong horizontal instability has been observed in the DAΦNE positron ring since 2003. Experimental observations suggest an electron cloud induced coupled bunch instability as a possible explanation. In this communication we present a simulation study of the electron cloud coupled bunch instability for the DAΦNE positron ring, performed with the code PEI-M, and compare the numerical results with experimental observations.