Keyword: damping
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MOOAB03 FACET First Beam Commissioning linac, emittance, sextupole, lattice 46
 
  • G. Yocky, C.I. Clarke, W.S. Colocho, F.-J. Decker, M.J. Hogan, N. Lipkowitz, J. Nelson, P.M. Schuh, J.T. Seeman, J. Sheppard, H. Smith, T.J. Smith, M. Stanek, Y. Sun, J.L. Turner, M.-H. Wang, S.P. Weathersby, G.R. White, U. Wienands, M. Woodley
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
The FACET (Facility for Advanced aCcelerator Experimental Tests) facility at SLAC has been under Construction since summer 2010. Its goal is to produce ultrashort and transversely small bunches of very high intensity (20kA peak current) to facilitate advanced acceleration experiments like PWFA and DLA. In June of 2011 the first electron beam was brought into the newly constructed bunch-compression chicane. Commissioning work included restarting the linac and damping ring, verifying hardware, establishing a good beam trajectory, verifying the optics of the chicane, commissioning diagnostic devices for transverse and longitudinal bunch size, and tuning up the beam size and bunch compression. Running a high-intensity beam through the linac without BNS damping and with large energy spread is a significant challenge. Optical aberrations as well as wakefields conspire to increase beam emittance and the bunch compression is quite sensitive to details of the beam energy and orbit, not unlike what will be encountered in a linear-collider final-focusing system. In this paper we outline the steps we took while commissioning as well as the challenges encountered and how they were overcome. 		 
slides icon Slides MOOAB03 [9.167 MB]  
 
MOOBC02 Status of Main Linac Cryomodule Development for Compact ERL Project linac, cavity, HOM, cryomodule 67
 
  • K. Umemori, K. Enami, T. Furuya, H. Sakai, M. Satoh, K. Shinoe
    KEK, Ibaraki, Japan
  • E. Cenni
    Sokendai, Ibaraki, Japan
  • M. Sawamura
    JAEA, Ibaraki-ken, Japan
  
  The Compact ERL, which is a test facility of ERL, is under construction at KEK, in Japan. For the main linac, one cryomodule, containing two 9-cell superconducting cavities, is under development. The cryomodule has been designed under High Pressure Gas Safety Code in Japan. Thermal design and cavity alignment have been also carefully considered. Two 9-cell cavities were already fabricated and their performances were confirmed by vertical tests. They satisfied ERL main linac specifications. Their accelerating field reached to 25 MV/m, without field limits. Two input couplers, three HOM absorbers and two Slide-Jack tuners are also under fabrication for the cryomodule. High power processing will be applied for input couplers, at a test stand using a 300 kW klystron. Cooling tolerance and HOM damping abilities were tested for HOM absorbers. Some performance studies were also applied for the tuner at room temperature condition. Cryomodule assembly is planned on this summer. After cooling tests and high power tests will be carried out, ERL beam operation will be started.  
slides icon Slides MOOBC02 [3.849 MB]  
 
MOEPPB004 A Compact Ring Design with Tunable Momentum Compaction dynamic-aperture, dipole, quadrupole, emittance 82
 
  • Y. Sun
    SLAC, Menlo Park, California, USA
  
  A storage ring with tunable momentum compaction has the advantage in achieving different RMS bunch length with similar RF capacity, which is potentially useful for many applications, such as linear collider damping ring and pre- damping ring where injected beam has a large energy spread and a large transverse emittance. A tunable bunch length also makes the commissioning and fine tuning easier in manipulating the single bunch instabilities. In this paper, a compact ring design based on a supercell is presented, which achieves a tunable momentum compaction while maintaining a large dynamic aperture.  
 
MOPPC027 Synchro-Betatron Effects in the Presence of Large Piwinski Angle and Crab Cavities at the HL-LHC betatron, luminosity, simulation, coupling 190
 
  • S.M. White
    BNL, Upton, Long Island, New York, USA
  • R. Calaga
    CERN, Geneva, Switzerland
  • R. Miyamoto
    ESS, Lund, Sweden
  
  Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP).
The reduction of beta-star at the collision points for the high luminosity LHC (HL-LHC) requires an increment in the crossing angle to maintain the normalized beam separation to suppress the effects of long-range beam-beam interactions. However, increase in crossing angle may give rise to synchro-betatron resonances which may negatively affect the beam emittance and lifetime. 6D weak-strong and strong-strong simulations are performed to study the effect of synchro-betatron resonances in the context of the HL-LHC layout and its suppression via crab crossing. 		 
 
MOPPC028 Coherent Beam-Beam Effects Observation and Mitigation at the RHIC Collider emittance, simulation, coupling, dipole 193
 
  • S.M. White, M. Bai, W. Fischer, Y. Luo, A. Marusic, M.G. Minty
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work partially supported by Brookhaven Science Associates, LARP, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In polarized proton operation in RHIC coherent beam-beam modes are routinely observed with beam transfer function measurements in the vertical plane. With the existence of coherent modes a larger space is required in the tune diagram than without them and stable conditions can be compromised for operation with high intensity beams as foreseen for future luminosity upgrades. We report on experiments and simulations carried out to understand the existence of coherent modes in the vertical plane and their absence in the horizontal plane, and investigate possible mitigation strategies. 		 
 
MOPPP062 Soleil Emittance Reduction using a Robinson Wiggler photon, emittance, brightness, wiggler 702
 
  • H.B. Abualrob, P. Brunelle, M.-E. Couprie, O. Marcouillé, A. Nadji, L.S. Nadolski, R. Nagaoka
    SOLEIL, Gif-sur-Yvette, France
  
  For both synchrotron light sources as SOLEIL and colliders, the emittance is one of the key parameters to increase the photon brightness and the beam luminosity. In order to decrease the emittance, the ring optics is built on very focusing lattices leading to large chromaticities and potential reduction of the dynamics aperture and momentum transverse acceptance. Thus, some facilities have installed damping wigglers in zero dispersion straight sections to relax the optics and to reach sub-nanometer horizontal emittances. This solution requires however tens or hundreds meters of insertion devices. For storage ring equipped with zero-gradient bending magnets, an alternative solution can be given by installing a single Robinson wiggler [1] in a dispersive section enabling to divide the emittance by a factor 2. The uniqueness of this wiggler results from the presence of an alternated gradient superimposed the main periodic magnetic field. This paper recalls the concept of the wiggler, presents the expected gain for SOLEIL storage ring with the impact on the linear optics and the brightness. A preliminary magnetic design is also proposed. [1] K.W. Robinson, Phys. Rev, p. 373 (1958).  
 
MOPPP079 Magnetic Tuning of the APS Wiggler as a Study for Tuning the NSLS-II Damping Wiggler wiggler, multipole, octupole, insertion 747
 
  • I. Vasserman, M. Abliz, E. Gluskin, E. Trakhtenberg, J.Z. Xu
    ANL, Argonne, USA
  
  Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
A wide variety of tuning techniques has been developed and employed at Advanced Photon Source (APS) in the course of tuning insertion devices for use on the APS storage ring, the APS free electron laser, and in assisting with the LCLS undulator tuning. The tuning requirements for the National Synchrotron Source II (NSLS-II) damping wigglers are very demanding and include limits on the off-midplane field integrals that are new in the repertoire of undulator magnetic tuning. The goal of this study was to assess the applicability of existing tuning techniques to meeting the off-midplane requirements of NSLS-II. Tests were run using an available APS 8.5-cm-period wiggler. In addition to existing techniques, a special new shim design was tested. This report summarizes the results of these tests and shows that the wiggler can be tuned to the required specifications on the midplane over the requested ±15 mm in the horizontal direction. In the vertical direction, however, the specifications could only be met within ±0.5 mm. This falls short of the ±15 mm by ± 3 mm good-field region that is sought by NSLS-II. 		 
 
MOPPR038 Bunch by Bunch Beam Diagnostics in SSRF betatron, wakefield, diagnostics, injection 861
 
  • Y.B. Leng, J. Chen, Z.C. Chen, Y.B. Yan, N. Zhang
    SSRF, Shanghai, People's Republic of China
  • B.P. Wang
    SINAP, Shanghai, People's Republic of China
  
  A set of broadband beam instruments including filling pattern monitor, scope based BPM processor and streak camera has been implemented in the storage ring of SSRF. Several parameters such as charge, lifetime, transverse position, betatron tune and beam length, can be measured for individual bunch by these devices. The operation experience and measurement results will be introduced. The preliminary effort to retrieve wake field information from these measurements will be presented as well.  
 
MOPPR064 Development of a Turn-by-Turn Beam Position Monitoring System for Multiple Bunch Operation of the ATF Damping Ring extraction, synchrotron, feedback, monitoring 930
 
  • P. Burrows, R. Apsimon, D.R. Bett, N. Blaskovic Kraljevic, G.B. Christian, M.R. Davis, A. Gerbershagen, C. Perry
    JAI, Oxford, United Kingdom
  • B. Constance
    CERN, Geneva, Switzerland
  • J. Resta-López
    IFIC, Valencia, Spain
  
  An FPGA-based monitoring system has been developed to study multi-bunch beam instabilities in the damping ring (DR) of the KEK Accelerator Test Facility (ATF). The system utilises a stripline beam position monitor (BPM) and a single-stage down-mixing BPM processor. The system is designed to record the horizontal and/or vertical positions of up to three bunches in the DR with c. 150ns bunch spacing, or the head bunch of up to three trains in a multi-bunch mode with bunch spacing of 5.6 ns. The FPGA firmware and data acquisition software allow the recording of turn-by-turn data. An overview of the system and performance results will be presented.  
 
TUEPPB003 Nonlinear Accelerator with Transverse Motion Integrable in Normalized Polar Coordinates lattice, simulation, focusing, insertion 1116
 
  • T.V. Zolkin
    University of Chicago, Chicago, Illinois, USA
  • Y. Kharkov, I.A. Morozov
    BINP SB RAS, Novosibirsk, Russia
  • S. Nagaitsev
    Fermilab, Batavia, USA
  
  Several families of nonlinear accelerator lattices with integrable transverse motion were suggested recently*. One of the requirements for the existence of two analytic invariants is a special longitudinal coordinate dependence of fields. This paper presents the particle motion analysis when a problem becomes integrable in the normalized polar coordinates. This case is distinguished from the others: it yields an exact analytical solution and has a uniform longitudinal coordinate dependence of the fields (since the corresponding nonlinear potential is invariant under the transformation from the Cartesian to the normalized coordinates). A number of interesting features are revealed: while the frequency of radial oscillations is independent of the amplitude, the spread of angular frequencies in a beam is absolute. A corresponding spread of frequencies of oscillations in the Cartesian coordinates is evaluated via the simulation of transverse Schottky noise.
V. Danilov and S. Nagaitsev, Phys. Rev. ST Accel. Beams 13 084002 (2010). 		 
 
TUPPC074 Study of Resonance Driving Term in Electron Storage Rings radiation, resonance, storage-ring, electron 1344
 
  • G. Liu, W. Li, L. Wang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  The resonance driving term (RDT) is useful to analyze and optimize the nonlinear performance of the storage ring. In addition to analytical calculation of RDT, experimental measurement of RDT has been made in some proton storage rings based on turn-by-turn BPM data. For electron storage rings, the analysis is more complicated due to decoherence effects and strong radiation damping. The relation between spectral decomposition of BPM data and RDT is derived and validated using beam numerical tracking data in this paper.  
 
TUPPC086 Conceptual Design of the CLIC damping rings emittance, wiggler, positron, vacuum 1368
 
  • Y. Papaphilippou, F. Antoniou, M.J. Barnes, S. Calatroni, P. Chiggiato, R. Corsini, A. Grudiev, J. Holma, T. Lefèvre, M. Martini, M. Modena, N. Mounet, A. Perin, Y. Renier, G. Rumolo, S. Russenschuck, H. Schmickler, D. Schoerling, D. Schulte, M. Taborelli, G. Vandoni, F. Zimmermann
    CERN, Geneva, Switzerland
  • C. Belver-Aguilar, A. Faus-Golfe
    IFIC, Valencia, Spain
  • A. Bernhard
    KIT, Karlsruhe, Germany
  • M.J. Boland
    ASCo, Clayton, Victoria, Australia
  • A.V. Bragin, E.B. Levichev, S.V. Sinyatkin, P. Vobly, K. Zolotarev
    BINP SB RAS, Novosibirsk, Russia
  • M. Korostelev
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • E. Koukovini
    EPFL, Lausanne, Switzerland
  • M.A. Palmer
    CLASSE, Ithaca, New York, USA
  • M.T.F. Pivi, S.R. Smith
    SLAC, Menlo Park, California, USA
  • R.P. Rassool, K.P. Wootton
    The University of Melbourne, Melbourne, Australia
  • L. Rinolfi
    JUAS, Archamps, France
  • A. Vivoli
    Fermilab, Batavia, USA
  
  The CLIC damping rings are designed to produce unprecedentedly low-emittances of 500 nm and 5 nm normalized at 2.86 GeV, in all beam dimensions with high bunch charge, necessary for the performance of the collider. The large beam brightness triggers a number of beam dynamics and technical challenges. Ring parameters such as energy, circumference, lattice, momentum compaction, bending and super-conducting wiggler fields are carefully chosen in order to provide the target emittances under the influence of intrabeam scattering but also reduce the impact of collective effects such as space-charge and coherent synchrotron radiation. Mitigation techniques for two stream instabilities have been identified and tested. The low vertical emittance is achieved by modern orbit and coupling correction techniques. Design considerations and plans for technical system, such as damping wigglers, transfer systems, vacuum, RF cavities, instrumentation and feedback are finally reviewed.  
 
TUPPD036 Novel Designs for Undulator Based Positron Sources positron, target, undulator, photon 1485
 
  • M. Jenkins
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • I.R. Bailey, M. Jenkins
    Lancaster University, Lancaster, United Kingdom
  
  At least three proposed future colliders(ILC, CLiC and LHeC) require a positron source with a yield greater than 1014 e+/s. An undulator based positron source has the potential to provide the required yield. This design generates gamma rays by using a high energy electron beam traveling through a superconducting helical undulator. The gamma rays then pair produce in a titanium alloy target to produce positrons. This is the ILC baseline positron source. Two drawbacks to the undulator-based positron source are that it couples the positron source to the electron beam operation and that it exhibits a low conversion efficiency of photons to positrons. A self-seeding undulator-based positron source has been proposed. This starts with a low intensity positron beam which travels through the undulator to produce more positrons which are recirculated through the source to increase the intensity until the design yield is achieved. Multiple targets have been added to increase the conversion efficiency of the positron source. In this study I present simulation results for such a design and consider the feasibility of this design at the ILC, CLiC or LHeC.  
 
TUPPP033 Exploration of a Tevatron-sized Ultimate Storage Ring emittance, storage-ring, brightness, sextupole 1683
 
  • M. Borland
    ANL, Argonne, USA
  
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
With the Tevatron now shut down and slated for decommissioning, it is only natural to think about other possible uses for the 6.3 km tunnel. Given that the brightness of electron storage rings naively scales as radius cubed, one exciting possibility is to build a so-called ultimate storage ring light source. This paper describes a somewhat speculative exploration of this idea, showing the potential for a storage ring x-ray source of unprecedented brightness. 		 
 
TUPPP043 Analysis of Coupled Bunch Instabilities in the NSLS-II Storage Ring with a 7-cell PETRA-III RF Structure HOM, impedance, cavity, simulation 1704
 
  • G. Bassi, A. Blednykh, S. Krinsky, J. Rose
    BNL, Upton, New York, USA
  
  Funding: Work supported by DOE contract No: DE-AC02-98CH10886.
A 7-cell PETRA-III cavity is considered to be installed for the commissioning Phase 1 in the NSLS-II storage ring at an average current of 25mA. In this contribution we study transverse and longitudinal coupled-bunch instabilities that may be driven by the higher order modes of the 7-cell PETRA-III cavity. The instability thresholds are calculated with the OASIS tracking code, with parameters of the bare lattice (no damping wigglers and Landau cavities). We study multibunch configurations with arbitrary fill-patterns and discuss the slow head-tail effect at positive chromaticity to increase the transverse instability thresholds. 		 
 
TUPPR003 The Design of Spin-Rotator with a Possibility of Helicity Switching for Polarized Positron at the ILC positron, solenoid, polarization, lattice 1813
 
  • L.I. Malysheva, O.S. Adeyemi, V.S. Kovalenko, G.A. Moortgat-Pick, A. Ushakov
    University of Hamburg, Hamburg, Germany
  • A.F. Hartin, B. List, N.J. Walker
    DESY, Hamburg, Germany
  • S. Riemann, F. Staufenbiel
    DESY Zeuthen, Zeuthen, Germany
  
  Funding: Work supported by German Federal Ministry of education and research. Joint Research project R&D Accelerator Spin Management, contract N 05H10CUE
At the ILC, positrons are produced with longitudinal polarization at the source. In order to preserve the polarization, the spin must be rotated into the vertical direction prior to injection into the damping rings. A new design of the spin rotator is presented that allows to randomly switch between the two vertical orientations between successive bunch trains. After rotating the spin back to longitudinal polarization, this corresponds to a choice between the two possible helicity states at the interaction point. The fast flipping is achieved by inserting two parallel spin rotation sections with opposite polarities, with a fast magnet that allows to choose between the sections. 		 
 
TUPPR013 Design Integration and Vision Sharing for the ILC lattice, linear-collider, linac, collider 1837
 
  • B. List, L. Hagge, S. Sühl, N.J. Walker, N. Welle
    DESY, Hamburg, Germany
  
  The Global Design Effort for the International Linear Collider is currently preparing the Technical Design Report, which will be released in early 2013. The starting point of a consistent and correct design is the accelerator lattice, which defines the layout of the machine. Integrating the lattice geometrically and optically provides the basis for civil engineering and conventional facilities planning and finally the cost estimate. Tools that provide three-dimensional visualization of the lattice and tunnel help to perform the design integration and allow sharing a common vision of the final accelerator. We will present the process that was established to arrive at such an integrated design and the tools that were developed to support that process by analyzing and visualizing lattice files.  
 
TUPPR015 Choke-Mode Damped Structure Design for the CLIC Main Linac wakefield, simulation, impedance, dipole 1840
 
  • H. Zha, H. Chen, W.-H. Huang, C.-X. Tang
    TUB, Beijing, People's Republic of China
  • A. Grudiev, J. Shi, W. Wuensch
    CERN, Geneva, Switzerland
  
  Choke-mode damped accelerating structures are being studied as an alternative to the CLIC waveguide damped baseline structure. Choke-mode structures hold the potential for much lower pulsed surface heating and reduced cost since no milling is required. We propose a new choke geometry which has significant suppression of higher order dipoles. By impedance matching and detuning of the first dipole pass-band, the wakefield suppression is comparable to the baseline design with waveguide damping. A fully featured choke mode structure with the same accelerating gradient profile and filling time as the nominal CLIC design has been designed. It has the potential to replace the waveguide damped design without changing any of the machine layout or the beam parameters.  
 
TUPPR016 Final Cross Section Design of the Stripline Kicker for the CLIC Damping Rings impedance, kicker, extraction, wakefield 1843
 
  • C. Belver-Aguilar, A. Faus-Golfe
    IFIC, Valencia, Spain
  • M.J. Barnes
    CERN, Geneva, Switzerland
  • F. Toral
    CIEMAT, Madrid, Spain
  
  Funding: IDC-20101074 and FPA2010-21456-C02-01
The CLIC design relies on the presence of Pre-Damping Rings (PDR) and Damping Rings (DR) to achieve, through synchrotron radiation, the very low emittance needed to fulfill the luminosity requirements. Kicker systems are required to inject and extract the beam from the Pre-Damping and Damping Rings. In order to achieve low beam coupling impedance and reasonable broadband impedance matching to the electrical circuit, striplines have been chosen for the kicker elements. In this paper the final design for the DR kicker is presented, including an optimization of the geometric parameters to achieve the requirements for both characteristic impedance and field homogeneity. In addition, a sensitivity analysis of characteristic impedance and field homogeneity to geometric parameters is reported. 		 
 
TUPPR018 Beam Impedance Study of the Stripline Kicker for the CLIC Damping Ring impedance, coupling, kicker, simulation 1849
 
  • C. Belver-Aguilar, A. Faus-Golfe
    IFIC, Valencia, Spain
  • M.J. Barnes
    CERN, Geneva, Switzerland
  • I. Podadera, F. Toral
    CIEMAT, Madrid, Spain
  
  Funding: FPA2010-21456-C02-01
CLIC Pre-Damping (PDR) and Damping Rings (DR) are required for reducing the emittance of the electron and positron beams before being accelerated in the main linac. Several stripline kicker systems are used to inject and extract the beam from the PDR and DR. Wakefields produced by the charged particles when passing through the aperture of the stripline kickers may become an important source of emittance growth; for this reason, simulations of longitudinal and transverse beam impedance in the frequency domain, and their equivalent in the time domain are needed. First analytical approaches, future simulations and tests planned are presented in this paper. 		 
 
TUPPR026 Conceptual Design of the CLIC Damping Ring RF System cavity, beam-loading, linac, coupling 1870
 
  • A. Grudiev
    CERN, Geneva, Switzerland
  
  In order to achieve high luminosity in CLIC, ultra-low emittance bunches have to be generated in both electron and positron damping rings. To achieve this goal, big energy loss per turn in the wigglers has to be compensated by the RF system. This results in very strong beam loading transients affecting the longitudinal bunch position and bunch length. In this paper, conceptual design of the RF system for the CLIC damping ring is presented. Baseline and several alternatives are discussed and the corresponding requirements for the cavities and the RF power sources are presented in order to meet stringent tolerances on the bunch-to-bunch phase and bunch length variations.  
 
TUPPR039 Beam Dynamics Studies for the CLIC Main Linac wakefield, linac, emittance, simulation 1903
 
  • I. Nesmiyan, R.M. Jones
    UMAN, Manchester, United Kingdom
  • A. Latina, D. Schulte
    CERN, Geneva, Switzerland
  
  Implications of the long-range wakefield on beam quality are investigated through a detailed beam dynamics study. Injection offsets are considered and the resulting emittance dilution recorded, including systematic and random sources of error. These simulations have been conducted for damped and detuned structures (DDS) and for waveguide damped structures–both for the CLIC collider.  
 
TUPPR043 New Baseline Design of the ILC RTML System positron, electron, linac, optics 1915
 
  • N. Solyak, V.V. Kapin, A. Vivoli
    Fermilab, Batavia, USA
  • S. Seletskiy
    BNL, Upton, Long Island, New York, USA
  
  The new ILC baseline was proposed in 2009 (Strawman baseline - SB2009) to minimize cost of the machine and accommodate many changes made in the design of the accelerator systems. The biggest changes are made in the central area, where BDS, RTML, DR, electron and positron sources are sharing the tunnels. A new layout of the compact DR and re-location of the electron and positron sources to the main tunnel requires a new lattice design for all beamlines in this area. The lattice design was coordinated between accelerator systems and Convention Facility and Siting (CFS) group to eliminate conflicts between beamlines and satisfy construction requirements. In this paper we present a new design of the RTML electron and positron lattices in the central area and other modifications made in the RTML line to accommodate changes to the beamline layouts.  
 
TUPPR047 Vibration Model Validation for Linear Collider Detector Platforms simulation, luminosity, ground-motion, coupling 1921
 
  • K.J. Bertsche, J.W. Amann, T.W. Markiewicz, M. Oriunno, A.W. Weidemann, G.R. White
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515.
The ILC and CLIC reference designs incorporate reinforced-concrete platforms underneath the detectors so that the two detectors can each be moved onto and off of the beamline in a Push-Pull configuration. These platforms could potentially amplify ground vibrations which would reduce luminosity. In this paper we compare vibration models to experimental data on reinforced concrete structures, estimate the impact on luminosity, and summarize implications for the design of a reinforced concrete platform for the ILC or CLIC detectors. 		 
 
TUPPR051 Development of L-Band Positron Capture Accelerating Structure with Kanthal-coated Collinear Load for SuperKEKB solenoid, cavity, target, positron 1933
 
  • F. Miyahara, Y. Arakida, T. Higo, N. Iida, K. Kakihara, T. Kamitani, S. Matsumoto
    KEK, Ibaraki, Japan
  • L. Lilje
    DESY, Hamburg, Germany
  
  In order to achieve a luminosity of 8x1035 cm-2 s-1, the SuperKEKB injector is required to provide both e+e− beams higher in intensity by a factor 4-5 than those for KEKB, and with a low emittance of about 20 um. A damping ring is used to fulfill this low emittance requirement for e+, but the intensity increase is realized by a larger yield from the conversion target to the damping ring. To this end, the L-band capture system is adopted to increase the transverse and longitudinal acceptance. The capture section consists of a Tungsten conversion target with flux concentrator followed by two L-band 2.4m-long accelerating structures and continuing to the large aperture S-band 2m-long ones. The L-band frequency of 1.3 GHz, 5/11 times S-band one, was adopted to suppress the satellite bunches in the S-band system. This L-band system is surrounded by a solenoid magnet producing 4kG on axis. To compose compact magnet system, the output coupler of the L-band accelerating structure is replaced by the Kanthal coated collinear load section. In this paper, we will discuss the design of the accelerating structure and present the studies of Kanthal layer coated on copper.  
 
TUPPR056 Parametric Study of the CLIC Damping Rings Delay Ring for Reaching Isochronicity Conditions dipole, sextupole, optics, quadrupole 1948
 
  • P. Zisopoulos, F. Antoniou, Y. Papaphilippou
    CERN, Geneva, Switzerland
  
  A delay ring in the CLIC damping rings complex is necessary for recombining the two trains to one with the nominal bunch separation of 0.5ns. The preservation of the longitudinal bunch distribution demands an optics design, which eliminates momentum compaction factor up to high order, allowing the delay ring to function under isochronous conditions. Taking into account thin lens approximation, a qualitative estimation of parameters of the cell that will be used in the delay ring, is given, so as to obtain isochronicity conditions. Considerations on the possibility of tuning the cell under those requirements are finally presented.  
 
TUPPR057 Intrabeam Scattering Studies at the Swiss Light Source emittance, scattering, storage-ring, monitoring 1951
 
  • F. Antoniou, Y. Papaphilippou
    CERN, Geneva, Switzerland
  • M. Aiba, M. Böge, N. Milas, A. Streun
    Paul Scherrer Institut, Villigen, Switzerland
  • T. Demma
    INFN/LNF, Frascati (Roma), Italy
  
  The target parameters of modern ultra-low emittance rings are entering into a regime where intra-beam scattering (IBS) becomes important and, in the case of linear collider damping rings, even a limitation for the delivered emittances. The Swiss Light Source (SLS) storage ring, as it has achieved a vertical geometrical emittance of around 2 pm at 2.4 GeV, and it has the ability to run at even lower energies, and the availability of emittance monitoring diagnostics, is an ideal test bed for IBS studies. Simulations using the classical IBS theories and tracking codes are undertaken in order to explore the possibilities and limitations for IBS measurements at the SLS. In this respect, comparison between the theories and codes is first discussed. The dependence of the output emittances, taking into account the effect of IBS, with respect to energy, bunch charge and zero current vertical and longitudinal emittance is also studied, in order to define the regimes where the IBS effect can be significant. First measurement results from the SLS running at lower energies are finally presented.  
 
TUPPR061 First Magnetic Test of a Superconducting Nb3Sn Wiggler Magnet for CLIC wiggler, emittance, plasma, electron 1957
 
  • D. Schoerling, P. Ferracin, P. Fessia, M. Karppinen, J. Mazet, S. Russenschuck
    CERN, Geneva, Switzerland
  • A.W. Grau
    Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
  • P. Peiffer
    KIT, Karlsruhe, Germany
  
  In the Compact Linear Collider (CLIC) the normalized horizontal and vertical emittances of the electron and positron beams must be reduced to 500 nm and 5 nm before the beams enter the 3 TeV linear accelerators. An effective way to accomplish ultra-low emittances are damping rings. Damping rings are storage rings equipped with strong wiggler magnets. In a first approximation damping wigglers are more effective the shorter the period length and the stronger the magnetic field is. Only superconducting wiggler magnets meet the demanding magnetic specifications of the CLIC damping rings. Nb-Ti damping wiggler magnets fulfill the specifications of CLIC but Nb3Sn wiggler magnets would reach higher magnetic fields leading to even better beam properties for CLIC. Moreover, they have at the same time higher thermal and magnetic margins. Therefore, Nb3Sn wiggler magnets are under investigation at CERN despite the challenging manufacturing process. This paper presents first results of Nb3Sn coils and short model tests and outlines the further plans for developing Nb3Sn wiggler magnets at CERN.  
 
TUPPR062 The Conceptual Design of a Vacuum System for the ILC Damping Rings Incorporating Electron Cloud Mitigation Techniques vacuum, wiggler, electron, photon 1960
 
  • J.V. Conway, Y. Li, M.A. Palmer
    CLASSE, Ithaca, New York, USA
  
  Funding: Work Supported by DOE Award DE-SC0006505.
We describe the conceptual design of the vacuum system for the damping rings of the International Linear Collider. The design incorporates a range of techniques to suppress the development of the electron cloud (EC) in the positron ring. These techniques include coatings with low secondary electron yield (SEY), grooved chambers, clearing electrodes and antechambers for photoelectron control. The EC mitigation choices are based on the ILC Electron Cloud R&D program, which has been conducted at the Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) and at other collaborating institutions*. The conceptual designs for vacuum chambers in drifts, dipoles, wigglers and quadrupoles are presented.
* The International Linear Collider: A Technical Progress Report, E. Elsen et al., Eds., pp. 71-81 (2011).
 		 
 
TUPPR065 Wiggler Magnet Design Development for the ILC Damping Rings wiggler, vacuum, lattice, linear-collider 1969
 
  • J.A. Crittenden, M.A. Palmer, D. L. Rubin
    CLASSE, Ithaca, New York, USA
  
  Funding: Work supported by the U.S. Department of Energy DE-SC0006506.
The baseline damping ring lattice design for the International Linear Collider employs nearly 60 2.2-m-long superconducting wiggler magnets to provide the damping necessary to achieve the specified horizontal emittance. We describe the OPERA-based finite-element model developed for the 14-pole, 30-cm period, 7.62-cm gap superferric design which meets the 2.1 T peak field requirement. Transfer functions and field uniformity results are discussed. We present results for the accuracy of the optimized analytic model needed for symplectic tracking algorithms, as well as implications for the updated engineering design. 		 
 
TUPPR066 Characterization of Single Particle Dynamics for the International Linear Collider Damping Ring Lattice emittance, wiggler, lattice, multipole 1972
 
  • J.P. Shanks, J.A. Crittenden, M.A. Palmer
    CLASSE, Ithaca, New York, USA
  • D.L. Rubin
    Cornell University, Ithaca, New York, USA
  
  Funding: DOE Award DE-SC0006506
The baseline design for the International Linear Collider damping rings is a 3.2 km circumference racetrack, with 5 GeV beam energy. The transverse damping time is 26 ms and the normalized horizontal emittance 5 mm-mrad. Nearly 60 2.2-m-long superconducting wigglers per ring increase the radiation damping rate by an order of magnitude and reduce horizontal emittance by a factor of 5. We characterize the sensitivity to magnet misalignments and field errors, and establish the minimum numbers of corrector magnets and beam position monitors required for tuning vertical emittance to less than 20 nm-rad. We validate the specified tolerable guide field multipole errors consistent with adequate dynamic aperture. Tune scans are used to identify stable working points. In tracking studies we use a wiggler model based on fits to 3-dimensional field maps. 		 
 
TUPPR069 Calculation of Wakefields in 17-GHz Beam-Driven Photonic Bandgap Accelerator Structure dipole, wakefield, simulation, electron 1981
 
  • M. Hu, B.J. Munroe, M.A. Shapiro, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts, USA
  
  We present computer simulations of the wakefields in a six cell Photonic Bandgap (PBG) structure at 17GHz. Using the commercial code CST Particle Studio, the major accelerating mode (TM01) and dipole mode (TM11) are identified. The modes are excited by passing an 18MeV electron beam through the structure. The comparisons of the wakefields in an elliptical-rod PBG structure, round-rod PBG structure, and disc-loaded waveguide structure are carried out to verify experimental results. Various parameters, such as the beam charge and position, are varied to analyze the amplitude and decay time of the wakefields in the three structures. All of the simulation results will guide the design of next generation high gradient accelerator PBG structures.  
 
TUPPR070 High-Gradient Photonic Band-gap (PBG) Structure Breakdown Testing at Ku-Band diagnostics, lattice, HOM, coupling 1984
 
  • B.J. Munroe, A.M. Cook, M.A. Shapiro, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts, USA
  
  Photonic Band-gap (PBG) structures continue to be a promising area of research forfuture accelerator structures. Previous experiments at X-Band have demonstrated that PBG structures can operate at high gradient and low breakdown probability, provided that pulsed heating is controlled. Two single-cell standing-wave structures have been constructed at MIT to investigate breakdown performance of PBG structures. A metallic structure with small rods will be used to test performance with very high surface temperature rise, while an over-moded structure with dielectric rods will investigate alternative solutions to the issue of surface temperature rise. Both structures are expected to reach gradients of at least 100 MV/m and will utilize novel diagnostics, including fast camera imaging and optical spectroscopy of breakdowns.  
 
TUPPR071 Experimental High-Gradient Testing of an Elliptical-Rod Photonic Band-Gap (PBG) Structure at X-Band wakefield, klystron, HOM, lattice 1987
 
  • B.J. Munroe, M.A. Shapiro, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts, USA
  • V.A. Dolgashev, S.G. Tantawi, A.D. Yeremian
    SLAC, Menlo Park, California, USA
  • R.A. Marsh
    LLNL, Livermore, California, USA
  
  An 11.4 GHz Photonic Band-gap (PBG) structure where the rods in the inner row have an elliptical cross-section has been designed at MIT and tested at high power and high repetition rate at SLAC. This structure exhibits lower surface magnetic fields on the rods relative to previous round-rod PBG structures tested at SLAC, which reduces the ohmic heating of the rod surface in an effort to reduce pulsed heating damage. This improved PBG structure was tested experimentally such as to avoid excessively high breakdown rates and surface temperature rise. The structure demonstrated performance comparable to disc-loaded waveguide (DLWG) structures with the same iris geometry, achieving greater than 100 MV/m gradient at a breakdown probability of less than 10-3 per pulse per m for 150 ns pulses. This level of performance demonstrates that elliptical-rod PBG structures could be candidates for future accelerator applications.  
 
TUPPR084 HOM Damping and Multipacting Analysis of the Quarter-wave Crab Cavity cavity, HOM, simulation, electron 2020
 
  • Q. Wu, S.A. Belomestnykh, I. Ben-Zvi
    BNL, Upton, Long Island, New York, USA
  • R. Calaga
    CERN, Geneva, Switzerland
  
  The Quarter-Wave Crab Cavity design has been analyzed further to accommodate LHC requirements. The goal for the design is to provide strong deflecting voltage to the proton bunches at the IP, while keeping the effective length as short as possible. We will evaluate the Higher Order Mode damping with two magnetic coupling dampers of 90 degrees apart. In this paper, we also show possible multipacting locations which are simulated by 3D code.  
 
WEYA02 Studies at CesrTA of Electron-Cloud-Induced Beam Dynamics for Future Damping Rings electron, simulation, emittance, dipole 2081
 
  • G. Dugan, M.G. Billing, K.R. Butler, J.A. Crittenden, M.J. Forster, D.L. Kreinick, R.E. Meller, M.A. Palmer, G. Ramirez, M.C. Rendina, N.T. Rider, K.G. Sonnad, H.A. Williams
    CLASSE, Ithaca, New York, USA
  • R.F. Campbell, R. Holtzapple, M. Randazzo
    CalPoly, San Luis Obispo, California, USA
  • J.Y. Chu
    CMU, Pittsburgh, Pennsylvania, USA
  • J.W. Flanagan, K. Ohmi
    KEK, Ibaraki, Japan
  • M.A. Furman, M. Venturini
    LBNL, Berkeley, California, USA
  • M.T.F. Pivi
    SLAC, Menlo Park, California, USA
  
  Funding: US National Science Foundation PHY-0734867, PHY-1002467, and PHY-1068662; US Dept. of Energy DE-FC02-08ER41538; and the Japan/US Cooperation Program.
Electron clouds can adversely affect the performance of accelerators, and are of particular concern for the design of future low emittance damping rings. Studies of the impact of electron clouds on the dynamics of bunch trains in CESR have been a major focus of the CESR Test Accelerator program. In this paper, we report measurements of coherent tune shifts, emittance growth, and coherent instabilities carried out using a variety of bunch currents, train configurations, beam energies, and transverse emittances, similar to the design values for the ILC damping rings. We also compare the measurements with simulations which model the effects of electron clouds on beam dynamics, to extract simulation model parameters and to quantify the validity of the simulation codes. 		 
slides icon Slides WEYA02 [2.033 MB]  
 
WEEPPB008 HOM Coupler Optimisation for the Superconducting RF Cavities in ESS HOM, cavity, neutron, target 2182
 
  • R. Ainsworth
    Royal Holloway, University of London, Surrey, United Kingdom
  • R. Calaga
    CERN, Geneva, Switzerland
  • S. Molloy
    ESS, Lund, Sweden
  
  The European Spallation Source (ESS) will be the world’s most powerful next generation neutron source. It consists of a linear accelerator, target, and instruments for neutron experiments. The linac is designed to accelerate protons to a final energy of 2.5 GeV , with an average design beam power of 5 MW, for collision with a target used to produce a high neutron flux. A section of the linac will contain Superconducting RF (SCRF) cavities designed to resonate at 704 MHz. Dangerous beam induced modes in these cavities may make the beam unstable and increase the cryogenic load and so couplers are usually installed to provide damping. Previous studies have shown potential designs are susceptible to multipacting, a resonant process which can absorb RF power and lead to heating effects. This paper will show how a coupler suffering from multipacting has been redesigned to limit this effect.  Optimisation of the RF damping is also discussed.  
 
WEEPPB010 RF Modeling Using Parallel Codes ACE3P for the 400-MHz Parallel-Bar/Ridged-Waveguide Compact Crab Cavity for the LHC HiLumi Upgrade cavity, HOM, impedance, dipole 2185
 
  • Z. Li, L. Ge
    SLAC, Menlo Park, California, USA
  • J.R. Delayen, S.D. Silva
    ODU, Norfolk, Virginia, USA
  
  Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515.
Schemes utilizing crab cavities to achieve head-on beam-beam collisions were proposed for the LHC HiLumi upgrade. These crabbing schemes require that the crab cavities be compact in order to fit into the tight spacing available in the existing LHC beamlines at the location where the crab cavities will be installed. Under the support of US LARP program, Old Dominion University and SLAC have joint efforts to develop a 400-MHz compact superconducting crab cavity to meet the HiLumi upgrade requirements. In this paper, we will present the RF modeling and analysis of a parallel-bar/ridged-waveguide shaped 400-MHz compact cavity design that can be used for both the horizontal and vertical crabbing schemes. We will also present schemes for HOM damping and multipacting analysis for such a design. 		 
 
WEPPC028 Slim Elliptical Cavity at 800 MHz for Local Crab Crossing cavity, coupling, impedance, HOM 2263
 
  • L. Ficcadenti, J. Tückmantel
    CERN, Geneva, Switzerland
  
  A slim highly eccentric elliptical Crab cavity with vertical deflection at 800 MHz, compatible to beam line distances everywhere in the LHC ring, was designed. It is a good fall-back solution in case of problems with new compact 400 MHz designs. Simulated RF characteristics of the delfecting mode, HOM spectra and damping, tuning and multipacting effects are presented. First the most simple HOM coupling system was investigated. The rejection of the working mode was not sufficient and a notch filter was added. Results of both cases will be presented.  
 
WEPPC072 High Current Operation of the Cornell ERL Superconducting RF Injector Cryomodule HOM, SRF, cavity, cryomodule 2378
 
  • M. Liepe, G.H. Hoffstaetter, S. Posen, P. Quigley, V. Veshcherevich
    CLASSE, Ithaca, New York, USA
  
  Cornell University has developed a SCRF injector cryomodule for the acceleration of high current, low emittance beams in continuous wave operation. This cryomodule is based on superconducting RF technology, and is currently under extensive testing in the Cornell ERL injector prototype with CW beam currents exceeding 25 mA. Strong damping of Higher-Order-Modes in the cavities is essential for high beam current operation, and is achieved by beamline RF absorber located at cryogenic temperatures in the beam pipe sections between the cavities. This paper gives an overview of the experience gained during the high beam current operation of the cryomodule.  
 
WEPPC086 Higher Order Modes Damping Analysis for the SPX Deflecting Cavity Cyromodule cavity, HOM, dipole, impedance 2414
 
  • L. Xiao, Z. Li, C.-K. Ng
    SLAC, Menlo Park, California, USA
  • A. Nassiri, G.J. Waldschmidt, G. Wu
    ANL, Argonne, USA
  • R.A. Rimmer, H. Wang
    JLAB, Newport News, Virginia, USA
  
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A single-cell superconducting deflecting cavity operating at 2.812 GHz has been proposed and designed for the Short Pulse X-ray (SPX) project for the Advanced Photon Source upgrade. A cryomodule of 4 such cavities will be needed to produce the required 2-MV deflecting voltage. Each deflecting cavity is equipped with one fundamental power coupler (FPC), one lower order mode (LOM) coupler, and two higher order mode (HOM) couplers to achieve the stringent damping requirements for the unwanted modes. The damping of the HOM/LOM modes below the beampipe cutoff has been analyzed in the single cavity geometry and shown to meet the design requirements. The HOMs above beam pipe cutoff in the 4-cavity cyromodule, however, may result in cross coupling which may affect the HOM damping and potentially trapped modes between the cavities which could produce RF heating to the beamline bellows and even be detrimental to the beam. We have evaluated the HOM damping and trapped modes in the 4-cavity cryomodule using the parallel finite element EM code ACE3P developed at SLAC. We will present the results of the cryomodule analysis in this paper. 		 
 
WEPPC100 Design of Electron and Ion Crabbing Cavities for an Electron-Ion Collider cavity, HOM, electron, ion 2447
 
  • A. Castilla, J.R. Delayen, G.A. Krafft
    ODU, Norfolk, Virginia, USA
  • A. Castilla
    JLAB, Newport News, Virginia, USA
  
  Beyond the 12 GeV upgrade at the Jefferson Lab a Medium Energy Electron-Ion Collider (MEIC) has been considered. In order to achieve the desired high luminosities at the Interaction Points (IP), the use of crabbing cavities is under study. In this work, we will present to-date designs of superconducting cavities, considered for crabbing both ion and electron bunches. A discussion of properties such as peak surface fields and higher-order mode separation will be presented.  
 
WEPPC102 Design and Development of Superconducting Parallel-bar Deflecting/Crabbing Cavities cavity, HOM, luminosity, pick-up 2453
 
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • S.U. De Silva
    JLAB, Newport News, Virginia, USA
  
  The superconducting parallel-bar cavity is a deflecting/crabbing cavity with attractive properties that is being considered for a number of applications. We present the designs of a 499 MHz deflecting cavity developed for the Jefferson Lab 12 GeV Upgrade and a 400 MHz crabbing cavity for the LHC High Luminosity Upgrade. Prototypes of these two cavities are now under development and fabrication.  
 
WEPPC113 Progress on the High-Current 704 MHz Superconducting RF Cavity at BNL cavity, HOM, higher-order-mode, impedance 2486
 
  • W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn, P. Jain
    BNL, Upton, Long Island, New York, USA
  • C.M. Astefanous, M.D. Cole, J.P. Deacutis, D. Holmes
    AES, Medford, NY, USA
  
  Funding: This work was supported by Sotny Brook under contract No. DE-SC0002496 and Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The 704 MHz high current superconducting cavity has been designed with consideration of both performance of fundamental mode and damping of higher order modes. A copper prototype cavity was fabricated by AES and delivered to BNL. RF measurements were carried out on this prototype cavity, including fundamental pass-band and HOM spectrum measurements, HOM studies using bead-pull setup, prototyping of antenna-type HOM couplers. The measurements show that the cavity has very good damping for the higher-order modes, which was one of the main goals for the high current cavity design. 3D cavity models were simulated with Omega3P code developed by SLAC to compare with the measurements. The paper describes the cavity design, RF measurement setups for the copper prototype, and presents comparison of the experimental results with computer simulations. The progress with the niobium cavity fabrication will also be described. 		 
 
WEPPD045 An Application of Multi-stage Adjustable Shock Absorbers for the Girders of Storage Ring in Taiwan Photon Source acceleration, controls, storage-ring, photon 2615
 
  • C.-S. Lin, J.-R. Chen, M.L. Chen, H.C. Ho, K.H. Hsu, D.-G. Huang, C.K. Kuan, W.Y. Lai, C.J. Lin, H.M. Luo, S.Y. Perng, P.L. Sung, Y.L. Tsai, T.C. Tseng, H.S. Wang, M.H. Wu
    NSRRC, Hsinchu, Taiwan
  • D.-Y. Chiang
    NCKU, Tainan city, Taiwan
  
  Beam stability is a major concern for the operation of the Taiwan Photon Source (TPS). One of the many factors to instability of electron beam is mechanical vibration of the accelerator components. The TPS uses steel girders to support the magnets and vacuum chambers in the storage ring. Three pedestal and six mover assemblies support the girders. Multi-stage adjustable shock absorbers are designed for passive vibration damping, and presently installed between the girders and the pedestals. Through adjusting the amount of hydraulic fluid which bypasses the damping passage between two hydraulic chambers, the desired damping coefficient of the damping absorbers can be achieved. Experimental results of modal testing presented in this paper show that the multi-stage adjustable damping absorbers under the assembly of the girders reduced the level of girder vibration.  
 
WEPPD079 Measurements of Magnetic Permeability of Soft Steel at High Frequencies impedance, booster, dipole, vacuum 2711
 
  • Y. Tokpanov, V.A. Lebedev, W. Pellico
    Fermilab, Batavia, USA
  
  The Fermilab Booster does not have a vacuum chamber which would screen the beam from laminations its dipoles cores. Therefore the booster impedance is mainly driven by the impedance of these dipoles. Recently an analytical model of the laminated dipole impedances was developed. However to match the impedance measurements with calculations one needs an accurate measurement of soft steel magnetic permeability. This paper presents the measurement results of the permeability in a frequency range from ~10 MHz to 1 GHz. Measurements of e.-m. wave propagation in 30 cm long strip line built from soft steel were used to compute the permeability. Measurements were performed in a DC magnetic field to observe the effect of steel saturation on the high frequency permeability. Both real and imaginary parts of the permeability were measured. As expected their values were decreasing with frequency increase from 10 MHz to 1 GHz and with saturation of steel DC permeability.
Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. 		 
 
WEPPP018 A New Beam Injection Scheme for a Compact Low-energy Storage Ring injection, kicker, storage-ring, acceleration 2761
 
  • Y. Honda
    KEK, Ibaraki, Japan
  
  A very compact storage ring at low energy has an unique application such as Compton X-ray source. Scheme for efficient injection is an issue for such a compact storage ring. Utilizing a phase-shift in the non-relativistic energy region, a new idea for accumulating the incoming bunch on an already circulating bunch without any kicker or orbit bump has been presented. Its applicable parameter range will be presented.  
 
WEPPP031 To the Possibility of Bound States between Two Electrons electron, emittance, positron, proton 2792
 
  • A.A. Mikhailichenko
    CLASSE, Ithaca, New York, USA
  
  We analyze the possibility to compress dynamically the polarized electron bunch so that the distance between some electrons in the bunch comes close to the Compton wavelength, arranging a bound state, as the attraction by the magnetic momentum-induced force at this distance dominates repulsion by the electrostatic force for the appropriately prepared orientation of the magnetic moments of the electron-electron pair. This electron pair behaves like a boson now, so the restriction for the minimal emittance of the beam becomes eliminated. Some properties of such degenerated electron gas represented also.  
 
WEPPP059 First Measurements with Multibunch Feedback Systems at the Fast Ramping Stretcher Ring ELSA feedback, kicker, cavity, electron 2840
 
  • M. Schedler, F. Frommberger, N. Heurich, W. Hillert, A. Roth, R. Zimmermann
    ELSA, Bonn, Germany
  
  Funding: Supported by German Research Foundation through SFB/TR 16.
At the Electron Stretcher Facility ELSA of Bonn University, an upgrade of the maximum stored beam current from 20 mA to 200 mA is planned. The storage ring operates applying a fast energy ramp of 4 GeV/s from 1.2 GeV to 3.5 GeV. The intended upgrade is mainly limited due to the excitation of multibunch instabilities. As a countermeasure, we succesfully commissioned state-of-the-art bunch by bunch feedback systems in the longitudinal and the two transverse dimensions. First results concerning the commissioning of the systems as well as the operation during the fast energy ramp will be presented. In particular, the performance while controlling the motion of every single bunch, especially in controlled bunch cleaning, will be discussed. 		 
 
WEPPP078 Status of the Mixed-signal Active Feedback Damper System for Controlling Electron-proton Instabilities for the Spallation Neutron Source feedback, pick-up, kicker, proton 2894
 
  • Z.P. Xie, M.J. Schulte
    UW-Madison, Madison, Wisconsin, USA
  • C. Deibele
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: Work supported by Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy
As the beam intensity at the Spallation Neutron Source (SNS) in Oak Ridge National Laboratory (ORNL) is leveled up, it becomes necessary to have greater control over the electron-proton (e-p) instability. This paper presents an updated design of a mixed-signal transverse feedback system for active damping of the e-p instability. It describes the design, features and results of this feedback damper and reviews several experimental studies to understand the system performance and its limitations. The updated mixed-signal feedback damper system employs power amplifiers (PAs), analog-to-digital converters (ADCs), multiple field programmable gate array (FPGA) chips, and digital-to-analog converters (DACs) to provide feedback damping and system monitoring. Unlike existing analog damping systems, FPGA-based feedback damping systems offer programmability while maintaining high performance. The system gain, delay and digital signal processing components can be programmed during the fly to perform timing adjustments, correct for ring harmonics, and equalize magnitude and phase dispersions. 		 
 
WEPPP083 Near Real-time Response Matrix Calibration for 10-Hz GOFB feedback, dipole, injection, quadrupole 2903
 
  • C. Liu, R.L. Hulsart, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The 10-Hz global orbit feedback, for damping the trajectory perturbation (~10 Hz) due to the vibrations of the triplets, is operational for injection and store in RHIC. The operation of the system has been performed using transfer functions between the beam position monitors and correctors obtained from the online optics model and a correction algorithm based on singular value decomposition (SVD). Calibration of the transfer functions by measuring the beam position oscillations while modulating the dedicated correctors has been carried out. The feedback results with model matrix and measured matrix will be compared. 		 
 
WEPPR001 Experimental Observation of Space Charge Effects in Transverse Bunch Oscillations in the SIS18 Synchrotron space-charge, synchrotron, simulation, ion 2931
 
  • V. Kornilov, O. Boine-Frankenheim
    GSI, Darmstadt, Germany
  
  Coherent signals from transverse bunch oscillations in the heavy-ion synchrotron SIS18 are used for direct measurements of the space charge effect. The bunch oscillations are excited by a transverse kick and the resulting decoherence is observed. The transverse coherent motion in the SIS18 experiments is strongly affected by space charge. The bunches are long, thus the nonlinear motion in the rf bucket plays an important role and must be taken into account. The signals from the measurements are analyzed and explained using analytical and numerical models.  
 
WEPPR005 Study of Electron Cloud Instability in Fermilab Main Injector electron, injection, simulation, proton 2943
 
  • K. Ohmi
    KEK, Ibaraki, Japan
  • R.M. Zwaska
    Fermilab, Batavia, USA
  
  Electron cloud has been observed in Fermilab main injector. Electron signal is enhanced near the transition. The slippage factor which suppress instabilities approach to zero at the transition. Instabilities must be most serious near the transition. The instability caused by the electron cloud is an important issue for high intensity operation and the future toward Project-X. Simulations of electron cloud instability near the transition is presented.  
 
WEPPR049 The Impact of Fill Patterns on the Fast Ion Instability in the ILC Damping Ring ion, emittance, feedback, electron 3036
 
  • G.X. Xia
    MPI-P, München, Germany
  
  The ions produced via collisional ionization of the residual gas molecules in vacuum pipe with the circulating electron beam have deleterious effect on the beam properties and may become a limiting factor in the machine’s performance. In this paper, the various beam fill patterns are investigated and their effects on the fast ion instability are discussed. The simulations show that an optimal fill pattern can reduce growth rate of the fast ion instability significantly.  
 
WEPPR052 Octupole Magnets for the Instability Damping at the J-PARC Main Ring octupole, resonance, sextupole, dynamic-aperture 3045
 
  • S. Igarashi, T. Koseki, K. Ohmi, M.J. Shirakata, H. Someya, T. Toyama
    KEK, Ibaraki, Japan
  • A. Ando
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  
  Octupole magnets have been installed for the instability damping at the J-PARC main ring. The transverse instability was observed during the injection and acceleration periods and caused the beam losses. The chromaticity tuning and bunch-by-bunch feedback system have been applied to suppress the instability. Octupole magnets were considered to create a larger amplitude dependent betatron tune shift and to supply additional option for the instability damping. The side effects of the dynamic aperture reduction and the resonances have been studied.  
 
WEPPR054 Calculation of Coherent Wiggler Radiation using Eigenfunction Expansion Method wiggler, impedance, radiation, space-charge 3048
 
  • D. Zhou, Y.H. Chin, K. Ohmi
    KEK, Ibaraki, Japan
  • G.V. Stupakov
    SLAC, Menlo Park, California, USA
  
  An analytic method originated by Y. H. Chin* was extended to calculate the electromagnetic fields and the longitudinal impedance due to coherent wiggler radiation (CWR) in a rectangular chamber. The method used dyadic Green functions based on eigenfunction expansion method in electromagnetic theory and was rigorous for the case of straight chamber. We re-derived the theory and did find the full expressions for the longitudinal impedance of a wiggler with finite length. With shielding of chamber, the CWR impedance indicated resonant properties which were not seen in the theory for CWR in free space.
* Y.H. Chin, LBL-29981, 1990. 		 
 
WEPPR061 Thresholds of Longitudinal Single Bunch Instability in Single and Double RF Systems in the CERN SPS simulation, impedance, synchrotron, emittance 3066
 
  • T. Argyropoulos, T. Bohl, J. Esteban Muller, E.N. Shaposhnikova, H. Timko
    CERN, Geneva, Switzerland
  • C.M. Bhat
    Fermilab, Batavia, USA
  
  A fourth harmonic RF system is used in the SPS as a Landau cavity, in order to stabilize the high intensity LHC proton beam against the longitudinal instabilities. Numerous studies proved that operating the two RF systems, through the whole cycle, in bunch shortening mode is necessary to provide a good quality beam at extraction to the LHC. Furthermore, it was shown that the choice of RF parameters as voltage amplitude ratio and relative phase are critical for the beam stability. This paper presents the results of single bunch measurements performed in single and double RF systems with various RF settings and compares them with the results of macroparticle simulations for the SPS impedance model.  
 
WEPPR068 Mitigation of Electron Cloud Instabilities in the LHC Using Sextupoles and Octupoles electron, octupole, sextupole, resonance 3084
 
  • K.S.B. Li, G. Rumolo
    CERN, Geneva, Switzerland
  
  Coherent electron cloud instabilities pose a serious limitation for luminosity upgrades in the Large Hadron Collider (LHC) at CERN. In particular, when bunch spacings reach below 50 ns, electron cloud formation is enhanced which in turn drives beam instabilities. The beam can be stabilised by shifting the tune and by increasing the tune spread using sextupoles or octupoles, respectively. The resulting values for the chromaticity and the detuning parameters must be selected with care, however, in order not to run into head-tail instabilities or to considerably reduce the dynamic aperture. A simulation study has been launched to estimate the parameters necessary for stabilisation of the beam under the influence of electron clouds.  
 
WEPPR077 Analysis of Long-range Wakefields in CLIC Main Linac Accelerating Structures with Damping Loads wakefield, simulation, HOM, resonance 3111
 
  • G. De Michele
    Paul Scherrer Institut, Villigen, Switzerland
  • G. De Michele
    EPFL, Lausanne, Switzerland
  • A. Grudiev
    CERN, Geneva, Switzerland
  
  The baseline design of the CLIC accelerating structure foresees a moderate detuning and heavy damping of high order modes (HOMs), which are the source of long-range transverse wakefields. Such unwanted fields produce bunch-to-bunch instabilities so the HOMs must be suppressed. In order to damp these modes, the CLIC RF structure is equipped with lossy material inserted into four rectangular waveguides coupled to each accelerating cell. The lossy material absorbs EM (electromagnetic) wave energy with little reflection back to the accelerating cells. In the past, computations of the long-range wake of CLIC accelerating modes have been done using perfectly absorbing boundaries to terminate the damping waveguides. In this paper, 3D EM simulations of CLIC baseline accelerating structure with HOMs damping loads will be presented. A comparison between different EM codes (GdfidL, CST PARTICLE STUDIO®) will be discussed as well as the analysis of different types of absorbing materials with respect to the wakefields damping.  
 
WEPPR084 Measurement of Coherent Damping Rate of the APS Storage Ring feedback, kicker, storage-ring, pick-up 3126
 
  • C. Yao, K.C. Harkay, H. Shang, C.-X. Wang
    ANL, Argonne, USA
  
  Funding: Work supported by U.S. Department of Energy, Offices of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The APS storage ring is a 7-GeV electron storage ring with a single-bunch current of up to 16 mA during normal user operations. To overcome beam instability we employ both chromatic correction and bunch-by- bunch feedback system. Typically we run a chromaticity of 4 for a 24-single fill pattern and 9 for a hybrids fill pattern in both planes with the feedback system loops closed. The APS upgrade (APS-U) calls for a beam current of 150 mA and installation of vertical deflecting cavities for short X-ray (SPX) production. In order to estimate whether the current chromatic correction and feedback system are adequate for the upgrade, we performed coherent damping rate measurements with two methods: kicking the beam with a kicker pulse and exciting the beam with the feedback system. We conclude that with a chromaticity of 4 in both planes, we can achieve a damping rate of 3 kHz in the x- plane and 2 kHz in the y-plane with feedback loops closed. Similar damping rates can also be achieved with chromatic correction alone. A special fitting program was developed to perform the damping rate analysis. This report presents the measurement data and results of the analysis. 		 
 
WEPPR085 Observation of Instabilities of Coherent Transverse Ocillations in the Fermilab Booster coupling, booster, injection, space-charge 3129
 
  • Y. Alexahin, N. Eddy, E. Gianfelice-Wendt, V.A. Lebedev, W.L. Marsh, W. Pellico, A.K. Triplett
    Fermilab, Batavia, USA
  
  Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
The Fermilab Booster - built more than 40 years ago - operates well above the design proton beam intensity of 4.e12 ppp. Still, the Fermilab neutrino experiments call for even higher intensity of 5.5·1012 ppp. A multitude of intensity related effects must be overcome in order to meet this goal including suppression of coherent dipole instabilities of transverse oscillations which manifest themselves as a sudden drop in the beam current. In this report we present the results of observation of these instabilities at different tune, coupling and chromaticity settings and discuss possible cures. 		 
 
WEPPR091 Multi-Particle Simulation Codes Implementation to Include Models of a Novel Single-bunch Feedback System and Intra-beam Scattering feedback, emittance, simulation, electron 3147
 
  • M.T.F. Pivi, A. Chao, C.H. Rivetta
    SLAC, Menlo Park, California, USA
  • F. Antoniou, K.S.B. Li, Y. Papaphilippou
    CERN, Geneva, Switzerland
  • M. Boscolo, T. Demma
    INFN/LNF, Frascati (Roma), Italy
  • K.G. Sonnad
    CLASSE, Ithaca, New York, USA
  
  Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP).
The beam tracking codes C-MAD and HEAD-TAIL have been enhanced to include a detailed model of a single-bunch feedback system. Such a system is under development to mitigate the electron cloud and the transverse mode coupling instability (TMCI) in the SPS and LHC at CERN. This paper presents the model of the feedback sub-systems: receiver, processing channel, filter, amplifier and kicker, which takes into account the frequency response, noise, mismatching and technological limits. With a realistic model of the hardware, it is possible to study the prototypes installed in the SPS and design a novel feedback system. The C-MAD code, which is parallel and optimized for speed, now also includes radiation damping and quantum excitation and a detailed model of Intra-Beam Scattering (IBS) based on the Zenkevich-Bolshakov algorithm, to investigate the IBS during damping and its effect on the beam distribution, especially the beam tails, that analytical methods cannot investigate. Intra-beam scattering is a limiting factor for ultra-low emittance rings such as CLIC and Super-B. 		 
 
WEPPR092 Beam Ion Instability in ILC Damping Ring with Multi-gas Species ion, vacuum, simulation, lattice 3150
 
  • L. Wang, M.T.F. Pivi
    SLAC, Menlo Park, California, USA
  
  Ion induced beam instability is one critical issue for the electron damping ring of the International Linear Collider (ILC) due to its ultra small emittance of 2 pm. The beam ion instability with various beam filling patterns for the latest lattice DTC02 is studied using code IONCLOUD. The code has been benchmarked with SPEAR3 experimental data and there is a good agreement between the simulation and observations. It uses the optics from MAD and can handle arbitrary beam filling pattern and vacuum. Different from previous studies, multi-gas species have been used simultaneously in the simulation. This feature makes it more accurate.  
 
THPPC011 Design of an Accelerating Structure for a 500 GeV CLIC using Ace3P linac, wakefield, simulation, beam-loading 3296
 
  • K.N. Sjobak, E. Adli
    University of Oslo, Oslo, Norway
  • A. Grudiev, W. Wuensch
    CERN, Geneva, Switzerland
  
  Funding: Research Council of Norway
An optimized design of the main linac accelerating structure for a 500 GeV first stage of CLIC is presented. A similar long-range wakefield suppression scheme as for 3 TeV CLIC based on heavy waveguide damping is adopted. The accelerating gradient for the lower energy machine is 80 MV/m. The 500 GeV design has larger aperture radius in order to increase the maximum bunch charge and length which is limited by the short-range wakefields. The cell geometries have been optimized using a new parametric optimizer for Ace3P and details of the RF cell design are described. Parameters of the full structure are calculated and optimized using a power flow equation. 		 
 
THPPC022 Enhanced Coupling Design of a Detuned Damped Structure for CLIC wakefield, coupling, simulation, dipole 3323
 
  • A. D'Elia, A. Grudiev, V.F. Khan, W. Wuensch
    CERN, Geneva, Switzerland
  • T. Higo
    KEK, Ibaraki, Japan
  • R.M. Jones
    UMAN, Manchester, United Kingdom
  
  The key feature of the improved coupling design in the Damped Detuned Structure (DDS) is focused on the four manifolds. Rectangular geometry slots and rectangular manifolds are used. This results in a significantly stronger coupling to the manifolds compared to the previous design. We describe the new design together with its wakefield damping properties.  
 
THPPC029 High-power Waveguide Dampers for the Short-Pulse X-Ray Project at the Advanced Photon Source HOM, cavity, vacuum, cryomodule 3344
 
  • G.J. Waldschmidt, B. Brajuskovic, J. Liu, M.E. Middendorf, A. Nassiri, T.L. Smith, G. Wu
    ANL, Argonne, USA
  • J. Henry, J.D. Mammosser, R.A. Rimmer, M. Wiseman
    JLAB, Newport News, Virginia, USA
  
  Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
High-power waveguide dampers have been designed and prototyped for the Short-Pulse X-ray (SPX) cavities at the Advanced Photon Source. The cavities will operate at 2.815 GHz and utilize the TM110 dipole mode. As a result, higher-order (HOM) and lower-order mode (LOM) in-vacuum dampers have been designed to satisfy the demanding broadband damping requirements in the APS storage ring. The SPX single-cell cavity consists of two WR284 waveguides for damping the HOMs and one WR284 waveguide for primarily damping the LOM where up to 2kW will be dissipated in the damping material. The damper designs and high-power experimental results will be discussed in this paper. 		 
 
THPPC036 The Alpha Ferrite-loaded Coaxial Resonator Cavity cavity, resonance, storage-ring, radiation 3365
 
  • A.N. Pham, S.-Y. Lee, T.H. Luo
    IUCEEM, Bloomington, Indiana, USA
  
  Funding: Grant N00164-08-GM03 P00004 from the NSWC Crane Division, DOE Grant DE-FG02-92ER40747, and NSF Grant PHY-0852368 (IU: 48-432-31).
The Advanced Electron Photon Facility (ALPHA)*,** is a joint collaboration between the Indiana University Center for Exploration of Energy and Matter and the Crane Naval Surface Warfare Center. The ALPHA storage ring will serve as a debuncher in single pass mode of operation. With a set of two gradient damping wigglers, the storage ring can also accumulate to achieve high charge density beams. In this report, we present the design, fabrication, and testing of the 15 MHz ferrite-loaded quarter-wave rf coaxial resonator cavity that will be utilized in the ALPHA storage ring. Topics pertaining to beam lifetime, radiation damping, ferrite-loaded transmission lines, and key cavity parameters will be discussed.
* S.Y. Lee, P.E. Sokol, et al, "The ALPHA Project at IU CEEM," Proceedings of the IPAC2010.
** S.Y. Lee, et al, "A low energy electron storage ring with tunable compaction factor," RSI 78, 2007. 		 
 
THPPC074 High Frequency High Power RF Generation using a Relativistic Electron Beam wakefield, electron, extraction, impedance 3458
 
  • C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • H. Chen, Y. Yang
    TUB, Beijing, People's Republic of China
  • M.E. Conde, W. Gai, J.G. Power
    ANL, Argonne, USA
  
  High frequency, high power rf sources are required for many applications. Benefiting from the ~10 GW beam power provided by the high current linac at the Argonne Wakefield Accelerator facility, we propose to develop a series of high power rf sources based on the extraction of coherent Cherenkov radiation from the relativistic electron beam. The frequencies cover from C-band up to W-band with different structures. Simulations show that ~1 GW 20 ns rf pulse can be generated for an 11.7 GHz structure, ~400 MW for a 26 GHz structure, and ~14 MW for a 91 GHz structure.  
 
THPPD076 Evaluation of Components for the High Precision Inductive Adder for the CLIC Damping Rings kicker, emittance, collider, luminosity 3692
 
  • J. Holma, M.J. Barnes
    CERN, Geneva, Switzerland
  
  The CLIC study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC damping rings will produce, through synchrotron radiation, ultra-low emittance beam with high bunch charge, necessary for the luminosity performance of the collider. To limit the beam emittance blow-up due to oscillations, the pulse generators for the damping ring kickers must provide extremely flat, high-voltage pulses. The specifications for the extraction kickers of the CLIC damping rings are particularly demanding: the flattop of the output pulse must be 160 ns duration, 12.5 kV and 250 A, with a combined ripple and droop of not more than ±0.02 %. An inductive adder allows the use of different modulation techniques and is therefore a very promising approach to meeting the specifications. In addition to semiconductors working in their saturated region, semiconductors working in their linear region are needed for applying analogue modulation techniques. Simulations have been carried out to define component specifications for the inductive adder: this paper reports the results of tests and measurements of various components.  
 
THPPP019 Tune Determination of Strongly Coupled Betatron Oscillations in a Fast Ramping Synchrotron coupling, booster, betatron, quadrupole 3770
 
  • Y. Alexahin, E. Gianfelice-Wendt, W.L. Marsh, A.K. Triplett
    Fermilab, Batavia, USA
  
  Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Tune identification - i.e. attribution of the spectral peak to a particular normal mode of oscillations - can present a significant difficulty in the presence of strong transverse coupling when the normal mode with a lower damping rate dominates spectra of Turn-by-Turn oscillations in both planes. The introduced earlier phased sum algorithm* helped to recover the weaker normal mode signal from the noise, but by itself proved to be insufficient for automatic peak identification in the case of close phase advance distribution in both planes. To resolve this difficulty we modified the algorithm by taking and analyzing Turn-by-Turn data for two different ramps with the beam oscillation excited in each plane in turn. Comparison of the relative amplitudes of Fourier components allows for automatic correct tune identification. The proposed algorithm was implemented in the Fermilab Booster B38 console application and successfully used in tune, coupling and chromaticity measurements.
* Y. Alexahin, E. Gianfelice-Wendt, W. Marsh, Proc. IPAC10, Kyoto, May 2010, p. 1179.