ANL, Argonne
HSRC, Higashi-Hiroshima
Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
In the selection of a new insertion device optimized for producing intense soft x-rays at the Advanced Photon Source, two different types of circular polarizing quasi-periodic undulators were studied. The magnetic structure of the undulators consists of pure permanent magnets for one of the undulators (an APPLE-II style undulator) and of electromagnets and pole pieces for the other type. The undulator period lengths were chosen so that the first harmonic energy occurs at 200 eV in linear horizontal polarization mode and at 400 eV in both linear vertical and circular polarization modes. Calculations of on-axis brilliance and on-axis flux spectra for both types of undulators and reductions of the spectral harmonics due to quasi-periodicity are presented. The introduction of quasi-periodicity of the magnetic fields shifts the higher spectral harmonics to a lower energy, hence reducing the so-called higher-order contamination dramatically. At the same time however, it reduces the first harmonic intensity by 20 40%. The non-sinusoidal shape of the horizontal and vertical magnetic fields of the electromagnetic undulator at high K values enhances the intensity of the first harmonic.
ANL, Argonne
Fermilab, Batavia
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An extensive R&D program is underway at the Advanced Photon Source (APS) with the aim of developing a technology capable of building a 2.4-m-long superconducting planar undulator for APS users. The initial phase of the project concentrates on using a NbTi superconductor and includes magnetic modeling, development of manufacturing techniques for the undulator magnet, and design and test of short prototypes. The current status of the R&D phase of the project is described in this paper.
ANL, Argonne
HSRC, Higashi-Hiroshima
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A request from the light source user community for insertion devices that provide only monochromatic light has led to development of quasi-periodic undulators (QPUs). These devices generate shifted harmonics in the photon energy spectrum, thus allowing suppression of higher harmonics by optical monochromator systems. Until now such undulators have been technically realized with pure permanent magnets or with hybrid structures. A concept for a superconducting quasi-periodic undulator (SCQPU) is suggested and described in this paper.
LBNL, Berkeley, California
Funding: This work is supported by the Director, Office of Science, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
In 2006, the 30mm period In-Vacuum Insertion Device (IVID) was operational for the femtosecond phenomena beamline at the Advanced Light Source (ALS) of Lawrence Berkeley National Laboratory. Since then the IVID has been demonstrating unexpected behaviors especially at small gaps (minimum gap = 5.5mm). The main observations related to these issues are partial or total beam losses as well as sudden pressure increases while operating the IVID gap. This paper is reporting these observations and describes the investigations and the repair attempt performed on this insertion device.
CERN, Geneva
In the CERN Large Hadron Collider, about 6 km of the UHV beam pipe are at ambient temperature and serve as experimental or utility insertions. The vacuum of these sectors rely on TiZrV non-evaporable getter (NEG) coating to achieve very low pressure. In the case of venting to atmosphere, the use of NEG coatings implies the bake-out of the vacuum sector to recover the low pressure and reactivate the NEG coatings. A new method to vent a vacuum sector to atmosphere allows performing short interventions without losing completely the performance of the already activated NEG coating. The principle is to over-pressurize the vacuum sector with neon gas which is not pumped by the NEG coatings, remove the faulty component and then pump down the sector again. The injection of such a gas in the vacuum sector aims at preserving the saturation of the NEG coatings during the exchange of the component. A detailed description of this new venting system will be presented and discussed. Preliminary results obtained from a laboratory venting system and its evaluation in the LHC tunnel to replace existing components will be presented.
LBNL, Berkeley, California
Funding: Supported by the U.S.Department of Energy under Contract No. DE-AC02-05CH11231.
Insertion quadrupoles with large aperture and high gradient are required to achieve the luminosity upgrade goal of 1035 cm-2 s-1 at the Large Hadron Collider (LHC). In 2004, the US Department of Energy established the LHC Accelerator Research Program (LARP) to develop a technology base for the upgrade. The focus of the magnet program, which is a collaboration of three US laboratories, BNL, FNAL and LBNL, is on development of high gradient quadrupoles using Nb3Sn in order to operate at high field and with sufficient temperature margin. Program components address technology issues regarding coil and structure fabrication, quench performance, field quality and alignment, length scale-up, quench protection, radiation hardness, conductor and cable. This paper reports the current status of model quadrupole development and outlines the long-term goals of the program.
CERN, Geneva
A first stage collimation system has been installed for the 2008 first beam commissioning of the LHC. It consists of 88 collimators distributed around the ring and the two injection lines. Each collimator has two jaws for which positions and angles must be controlled and monitored with high precision. The LHC collimation system was put into operation from July to October 2008. The installed system is described and the first results from system operation without and with beam are presented. In particular, it is shown that the LHC collimation system achieved the specified accuracy and reproducibility of jaw positioning. The next steps in collimation commissioning and the expected system evolution are described. Planned system upgrades for high LHC beam intensities are outlined.
FZJ, Jülich
CEA, Gif-sur-Yvette
The driver of the International Fusion Material Irradiation Facility (IFMIF) consists of two 125 mA, 40 MeV cw deutron accelerators. A superconducting option for the 5 to 40 MeV linac is based on Half-Wave Resonators (HWR) has been choosen. The first cryomudule should contain 8 HWR's with resonant frequency of 175 MHz and beta=v/c=0.094. The paper describes RF design of half-wave length resonator. The requirents on high power coupler define its installation in the cavity central region. Few options of cavity tune were investigated, the capacitive tuner installed opposite to the coupler port have been accepted. The cavity structural analyses have been conducted and cavity stiffening has been worked out.
HRC, Santa Clara, California
Funding: Work performed under the auspices of the U.S. Department of Energy SBIR Grant No. DE-FG02-08ER85197.
The salient features and design parameters of a dual resonant ring system configured for evaluating the high gradient performance of 11.424 GHz TW linear accelerator structures are presented; and the inherent rapid protection mechanism that automatically limits energy deposition during breakdown of the structure, and minimizes RF source reflections, is discussed. The diagnostic characteristics of the RF bridge load monitors and their unique capability of detecting the power imbalance caused by a feedback loop phase change of less than 2 parts in 10000, representing a 2 to 3 degree phase change of the linac structure, is described. The transient and steady-state power apportionment within the ring system is analyzed; and, in considering initial high power tests using an 18-cavity CLIC/KEK/SLAC structure, the results indicate that the demonstration of an unloaded average accelerating gradient of 108 MV/m will require a source power of 26 MW.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
ALBA is the first 3rd generation synchrotron light source to be build in Spain. The project is in the process of installation, with the LINAC already commissioned, and the Booster and Storage Ring in the installation phase, and the building already completed. The Booster synchrotron is expected to be finish and commission by the end of summer 2009, and the storage ring commissioning should take place in spring 2010. Most of the major components are already delivered and tested in-house, among those the vacuum system, the magnets, the RF cavities, etc. In this paper, the status of the project and of the most relevant components is reviewed.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
J-PARC, KEK & JAEA, Ibaraki-ken
The beam loss issues connected to the nuclear scattering together with the multiple Coulomb scattering at the charge-exchange foil during the multi-turn injection has been studied in detail for the RCS (Rapid Cycling Synchrotron) of J-PARC (Japan Proton Accelerator Research Complex). Recently, during the beam commissioning of RCS, some experimental data related to such issue has been taken and thus a comparison of the measured beam loss to the estimated one is reported in this paper. When the beam loss from such a source is unavoidable, a realistic estimation is quite important for a fair design of the injection system and the vicinity in order to reduce especially, the uncontrolled beam loss.
Fermilab, Batavia
A new experimental area, the Muon Test Area, has been constructed to develop, test, and verify muon ionization apparatus using the 400-MeV proton beam from the Fermilab Linac. Since muon-cooling apparatus is being developed for facilities that involve the capture, collection and cooling of ~1013 muons at a repetition rate of 15 Hz, conclusive tests require full Linac beam, or ~1013 protons/pulse at 15 Hz. A beamline has been designed which includes specialized insertions for linac beam diagnostics and beam measurements, greatly enhancing the functionality of the line in addition to providing beam for MTA experiments. Installation of the beamline is complete and first beam was achieved in November, 2008. The design, operational flexibility, and characteristics of the MTA beamline will be presented.
NSRRC, Hsinchu
Bending Magnet, linear undulator, elliptical polarized undulator and wiggler are all regular synchrotron radiation power profile that accelerator engineers would encounter while they are designing the high heat load components. Due to their characteristic type of power distribution, some temperature solutions are available and can be used as a parametric study, as well as optimized tool applicable on the thermomechanical design such as mask absorber, photon absorber, mirror or other heat load subsystems. The analytical solutions and some interrelation studies are also presented in this paper.
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.
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.
Omega-P, Inc., New Haven, Connecticut
KEK, Ibaraki
Fermilab, Batavia
Measurements are reported for a one-third version of a L-band high-power ferroelectric phase shifter. The device is designed to allow fast adjustments of cavity coupling in an accelerator where microphonics, RF source fluctuations, or another uncontrolled fluctuations could cause undesired emittance growth. Experimental measurements of switching speed, phase shift and insertion loss vs. externally-applied voltage are presented. An average switching rate of 0.5 ns or better for each degree of RF phase has been observed.
INFN/LASA, Segrate (MI)
BESSY GmbH, Berlin
An extensive validation activity has been conducted since year 2007 for the coaxial Blade Tuner for TESLA SC cavities. During this activity, performances and limits of prototype models have been deeply investigated through detailed test sessions inside CHECHIA (DESY) and HoBiCaT (BESSY) horizontal cryostats as well as F.E. modeling and analyses. The result is an improved design for the Blade Tuner, specifically meant to satisfy the incoming ILC-level performance requirements, fulfill pressure vessels regulations and keep Ti / S.S. material compatibility. Recent Blade Tuner activities and results will be presented in this paper in view of the installation of 8 units in the second cryomodule of ILCTA facility at Fermilab, and also of our contribution to both incoming S1-Global (KEK) and ILC-HiGrade projects. The manufacturing process of the first set of 8 tuners, from production to room temperature validation for the whole series, will be also reviewed. Then results will be shown from the cold tests recently performed, where special effort has been made in evaluating the accuracy and repeatability of fast and slow tuning action at few Hz range.
ELETTRA, Basovizza
A full energy injector consisting of a 100 MeV linac and an up to 2.5 GeV booster is in operation since March 2008 replacing the previous 1 GeV linac injector to be used after refurbishing and upgrade for the new fourth generation light source (FEL) currently under construction at Sincrotrone Trieste. The measurements on the new injector, problems and solutions employed to increase its efficiency, reproducibility and reliability, aiming towards top-up operations in the near future, and its impact on the Elettra storage ring are presented and discussed.
ANL, Argonne
Slovak Academy of Sciences, Institute of Electrical Engineering, Bratislava
Funding: * Work at Argonne supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract no. DE-AC02-06CH11357.
Hall probe is the best way to do tuning and measurements of insertion devices. Horizontal Hall probe magnetic field measurements in the presence of a strong vertical magnetic field were tested in 1997. The next step of this investigation was reported at the 2004 FEL Conference. Hall probe horizontal field measurements in the presence of a vertical magnetic field are complicated due to the influence of the Planar Hall probe effect on the resulting Hall voltage. 2-axis Sentron Hall probe was used for the Linear Coherent Light Source devices. By positioning the Hall probe accurately in the vertical direction, the probe could be used for fast measurements and tuning of FEL devices. To eliminate the high sensitivity to the positioning of the probe, a new type of Hall probe, consisting of two sensors combined so as to cancel the influence of the PHE, was developed at the Institute of Electrical Engineering, Slovak Academy of Sciences. The results of tests done at the APS showed that it is not sensitive to vertical position and is 60 times less sensitive than a Bell probe to the angle between the Hall sensor current and the in-plane component of the field direction.
RadiaBeam, Marina del Rey
BNL, Upton, Long Island, New York
Funding: DOE
A High Temperature Superconducting Dysprosium Pole Undulator (HTS-DPU) is proposed to achieve an ultra-high peak field in a very short period undulator structure. This design utilizes the unique ferromagnetic properties of dysprosium (Dy) at liquid nitrogen temperature. The fabrication of textured Dy fabricated via economic and highly reproducible process is studied experimentally with the goal to achieve sufficient magnetic anisotropy and desired field saturation level at a practical cost. In addition, utilizing the latest capabilities of the 2G HTS wire is investigated. The practical implementation of HTS-DPU would enable the development of short period insertion devices with superior performance.
SLRI, Nakhon Ratchasima
NSRRC, Hsinchu
Highest photon beam brightnesses are achieved in radiation from undulators. Very short period length and high fields, reached only in superconducting undulators, are desired to produce hard X-rays. In lower energy storage rings this is not enough, but radiation at higher harmonics(7th and up) are desirable. This is possible only if the undulator fields and periods are near perfect. Shimming methods as applied for room temperature permanent magnet undulators cannot be used for such superconducting magnets. The effect of field and period tolerances on higher harmonics photon beam brightnesses will be presented and limiting tolerances will be discussed. A variety of different field optimization techniques together with some measurements on test magnets will be discussed and evaluated to their usefulness as a high photon energy and high brightness radiation source.
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
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.
CERN, Geneva
The Large Hadron Collider extends the present state-of-the-art in stored beam energy by 2-3 orders of magnitude. A sophisticated system of collimators is implemented along the 27 km ring and mainly in two dedicated cleaning insertions, to intercept and absorb unavoidable beam losses which could induce quenches in the superconducting magnets. 88 collimators per beam are initially installed for the so called Phase 1. An optimized strategy for the commissioning of this considerable number of collimators has been defined. This optimized strategy maximizes cleaning efficiency and tolerances available for operation, while minimizing the required beam time for collimator setup and ensuring at all times the required passive machine protection. It is shown that operational tolerances from collimation can initially significantly relaxed.
CERN, Geneva
The different levels of LHC collimators must be set up by respecting a strict setting hierarchy in order to guarantee the required performance and protection during the different operational machine stages. The available margins are a fraction of a beam σ. Two different sub-systems establish betatron and momentum collimation for the LHC. Collimator betatronic phase space cuts are defined for a central on-momentum particle. However, due to the chromatic features of the LHC optics and energy deviations of particles, the different phase space cuts become coupled. Starting from the basic equation of the transverse beam dynamics, the influence of off-momentum beta-beat and dispersion on the effective collimator settings has been calculated. The results are presented, defining the allowed phase space regions from LHC collimation. The impacts on collimation-related setting tolerances and the choice of an optimized LHC optics are discussed.
CERN, Geneva
The TOTEM experiment requires special high beta optics solutions. We report on studies of optics for an intermediate beta* = 90 m, as well as a solutions for a very high beta* of 1540 m, which respect all known constraints. These optics are rather different from the normal physics optics and will require global tune changes or adjustments.
EPFL, Lausanne
CERN, Geneva
KIT, Karlsruhe
Due to the known limitations of Phase I LHC collimators in stable physics conditions, the LHC collimation system will be complemented by additional 30 Phase II collimators. The Phase II collimation system is designed to improve cleaning efficiency and to minimize the collimator-induced impedance with the main function of protecting the Super Conducting (SC) magnets from quenching due to beam particle losses. To fulfil these requirements, different possible innovative collimation designs were taken in consideration. Advanced jaw materials, including new composite materials (e.g. CuDiamond), jaw SiC insertions, coating foil, in-jaw instrumentation (e.g. BPM) and improved mechanical robustness of the jaw are the main features of these new promising Phase II collimator designs developed at CERN. The FLUKA Monte Carlo code is extensively used to evaluate the behavior of these collimators in the most radioactive areas of LHC, supporting the mechanical integration. These studies aim to identify the possible critical points along the IR7 line.
CERN, Geneva
While the Large Hadron Collider (LHC) at CERN is starting operation with beam, aiming to achieve nominal performance in the shortest term, the upgrade of the LHC interaction regions is actively pursued in order to enhance the physics reach of the machine. Its first phase, with the target of increasing the LHC luminosity to 2-3 1034 cm-2 s-1, relies on the mature Nb-Ti superconducting magnet technology and is intended to maximize the use of the existing infrastructure. The impact of the increased power of the collision debris has been investigated through detailed energy deposition studies, considering the new aperture requirements for the low-beta quadrupoles and a number of other elements in the insertions. Effective solutions in terms of shielding options and design/layout optimization have been envisaged and the crucial factors have been pointed out.
CERN, Geneva
EPFL, Lausanne
IHEP Protvino, Protvino, Moscow Region
Bent crystals are promised to provide a path towards significant improvement of cleaning efficiency for high power collimation systems. In this paper a possible implementation of a crystal-enhanced collimation system is evaluated for the LHC. Simulation studies were performed with the same state-of the art tracking codes as used for the design of the conventional LHC collimation system. The numerical models are described and predictions for the local and global cleaning efficiency with a crystal-based LHC collimation system are presented. Open issues and further work towards a crystal collimation design for the LHC are discussed.
Sheffield University, Sheffield
The MICE experiment requires a beam of low energy muons to test muon cooling. This beam is derived parasitically from the ISIS accelerator at the Rutherford Appleton Laboratory. A novel target mechanism has been developed which allows the insertion of a small titanium target into the proton beam on demand, for the final couple of milliseconds before extraction. The first operational linear drive was installed onto ISIS in January of 2008. Since then, it has operated for over 100,000 actuations. Studies have been performed of particle production and collection by the MICE beam-line, as well as verification of the reliability of the target drive itself. The target data acquisition system records not only the position of the target throughout the ISIS acceleration cycle, but also the outputs from beam loss monitors placed around the synchrotron. Data will be presented showing the stability of the target’s motion and the correlation of beam loss and particle production with the timing and depth of the target’s intersection with the circulating beam.
Sheffield University, Sheffield
The MICE Experiment requires a beam of low energy muons to demonstrate muon cooling. This beam is derived parasitically from the ISIS accelerator. A novel target mechanism has been developed that inserts a small titanium target into the proton beam on demand. The target remains outside the beam envelope during acceleration and then overtakes the shrinking beam envelope to enter the proton beam during the last 2 ms before beam extraction. The technical specifications for the target mechanism are demanding, requiring large accelerations and precise and reproducible location of the target each cycle. The mechanism operates in a high radiation environment, and the moving parts are compatible with the stringent requirements of the accelerator’s vacuum system. This paper will describe the design of the MICE target and how it is able to achieve its required acceleration whilst still meeting all of the necessary requirements for operation within the ISIS vacuum. The first operational linear electromagnetic drive was installed onto ISIS in January 2008 and has since been operated for over one hundred thousand actuations.
CERN, Geneva
Collimation and halo cleaning for the LHC beams are performed separately for betatron and momentum losses, requiring two dedicated insertions for collimation. Betatron cleaning is performed in IR7 while momentum cleaning is performed in IR3. A study has been performed to evaluate the performance reach for a combined betatron and momentum cleaning system in IR3. The results are presented.
BNL, Upton, Long Island, New York
The NSLS-II Light Source being built at Brookhaven National Laboratory is expected to provide submicron stability of the electron orbit in the storage ring in order to utilize fully the very small emittances and electron beam sizes. This requires high stability supports for BPM pick-up electrodes, located near insertion device source. Description of the efforts for development of supports including carbon tubes and invar rods is presented.
Diamond, Oxfordshire
JAI, Oxford
A proposal has been developed to modify a long insertion straight (~11.4 m long) of the DIAMOND storage ring. Additional quadrupoles provide two sections with small vertical beta-function values, in order to accommodate two canted in-vacuum undulators for the imaging and coherence branches of the I13 beam line. A further requirement was to provide a horizontal focussing of the emitted undulator radiation by means of a positive alpha-x in the second section. This optic is obtained using a small relaxation in the “pitrick”, approximately preserving the on-momentum nonlinear dynamics of the ring. The effects of the optic on beam dynamics (i.e. beam lifetime, injection etc.) and possible compensation schemes are presented.
CERN, Geneva
As for the final focus systems of linear colliders, the chromatic aberrations induced by low-beta insertions can seriously limit the performance of circular colliders. The impact is two-fold: (1) a substantial off-momentum beta-beating wave travelling all around of the ring leading to a net reduction of the mechanical aperture of the low-beta quadrupoles but also impacting on the hierarchy of the collimator and protection devices of the machine, (2) a huge non-linear chromaticity, essentially Q’’ and Q’’’, which, when combined with the geometric non-linear imperfection of the machine could substantially reduce the momentum acceptance of the ring by sending slightly off-momentum particles towards non-linear resonances. These effects will be analyzed and illustrated in the framework of the LHC insertions upgrade and a strategy for correction will be developed, requiring a deep modification of the LHC overall optics.
NSRRC, Hsinchu
The orbit feedback system of the TLS has been deployed for a decade to stabilize electron closed orbit. As the upgrades of digital bpm electronics and switching power supply, the infrastructure of orbit feedback system has also been dramatically modified and rebuilt. The most primary works for the upgrade plan have been done including installation of new bpm and power supply since it was first proposed. After the ordered computer blade ready and the current updated rate raised from 1 kHz to 5 kHz or even 10 kHz, the system will evolve to a newly fast orbit feedback system. It is new scheduled to be commissioned in 2009 spring and can be expected to achieve a submicron stability of the electron beam at a bandwidth of at least 60 Hz.
JLAB, Newport News, Virginia
RUBYTRON, Rye Brook, New York
In-air test fixtures for beamline elements typically utilize an X-Y positioning stage, and a wire antenna excited by an RF source. In most cases, the antenna contains a standing wave, and is useful only for coarse alignment measurements in CW mode. A surface-wave (SW) based transmission line permits RF energy to be launched on the wire, travel through the beamline component, and then be absorbed in a load. Since SW transmission lines employ traveling waves, the RF energy can be made to resemble the electron beam, limited only by ohmic losses and dispersion. Although lossy coaxial systems are also a consideration, the diameter of the coax introduces large uncertainties in centroid location. A SW wire is easily constructed out of 200 micron magnet wire, which more accurately approximates the physical profile of the electron beam. Benefits of this test fixture include accurate field mapping, absolute calibration for given beam currents, Z-axis independence, and temporal response measurements of sub-nanosecond pulse structures. Descriptions of the surface wave launching technique, transmission line, and receiver electronics are presented, along with measurement data.
KEK, Ibaraki
KURRI, Osaka
Straight section in scaling FFAG accelerator has been explored and scaling law for straight section has been investigated. Under these studies, dispersion suppressed straight section, which could be useful for efficient RF acceleration, can be designed in ordinary scaling FFAG ring accelerator.
KEK, Ibaraki
KURRI, Osaka
Harmonic number jump (HNJ) acceleration in scaling FFAG accelerator, especially for muon acceleration in neutrino factory, has been studied. Criterions for HNJ acceleration were clarified and beam tracking simulations have been carried out.
LBNL, Berkeley, California
Funding: Supported by DOE BES contract DE-AC03-76SF00098.
Recently there has been a proposal to use pulsed high order multipole elements for injection. One of the advantages of this proposed injection scheme would be that it would be less disruptive to the stored beam and thus advantageous for Top-off operation. In addition to Top-off, such novel injectors might open the door to operating storage rings in more desirable lattice settings. In this paper we will explore some of the possibilities for taking advantage of high order multipole pulsed kick injection.
TUB, Beijing
Funding: This work is supported by National Natural Science Foundation of China (Project 10735050) and National Basic Research Program of China (973 Program) (Grant No. 2007CB815102).
The feasibility study of optical stochastic cooling (OSC) utilizing a compact storage ring is presented in this paper. We present the general layout of the scheme, as well as the lattice design of the storage ring. The results of beam dynamics simulation are likewise presented.
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.
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.
CERN, Geneva
The 2008 collimation system of the CERN Large Hadron Collider (LHC) included 80 movable collimators for a total of 316 degrees of freedom. Before beam operation, the final controls implementation was deployed and commissioned. The control system enabled remote control and appropriate diagnostics of the relevant parameters. The collimator motion is driven with time-functions, synchronized with other accelerator systems, which allows controlling the collimator jaw positions with a micrometer accuracy during all machine phases. The machine protection functionality of the system, which also relies on function-based tolerance windows, was also fully validated. The collimator control challenges are reviewed and the final system architecture is presented. The results of the remote system commissioning and the operational experience are discussed. The system tests performed for the 2009 beam operation are also reviewed.