Keyword: damping
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MOPEA023 Lattice Design for the ILSF Booster Synchrotron booster, sextupole, emittance, quadrupole 121
 
  • E. Ahmadi, H. Ghasem, F. Saeidi
    ILSF, Tehran, Iran
  • H. Ghasem
    IPM, Tehran, Iran
  
  ILSF booster synchrotron is a full energy 3GeV injector with the circumference of 192m will be housed in a separate tunnel from storage ring. In order to keep low the emittance, a theoretical minimum emittance lattice in which the dipoles and quadrupoles have sextupole component has been considered for the booster. In this paper, the lattice concept and main features of the booster will be reported. The variation of emittance and beam size during booster ramping is also investigated. Finally the effect of existed eddy current on the chromaticity and dynamic aperture will be presented.  
 
MOPME018 BEAM OSCILLATION MONITOR FOR THE MULTI-BUNCH BEAM kicker, linac, wakefield, extraction 506
 
  • T. Naito, S. Araki, H. Hayano, K. Kubo, S. Kuroda, T. Okugi, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  
  In order to observe the motion of bunch-by-bunch beam oscillation of multi-bunch in the storage ring, we developed two measurement tools. One is a signal process electronics circuit using fast analogue switches. The circuit picks up one of the selected bunch signal of the beam position monitor from the multi-bunch. The selected beam position signal can be processed as a single bunch beam. By changing the gate timing, arbitrary bunch signal can be selected. The other is a waveform memory using a high bandwidth oscilloscope. The long waveform memory of the oscilloscope has a capability to acquire the multi-turn waveform of the button electrode signals. The beam test of the circuit has been carried out at KEK-ATF damping ring in the cases of 2.8ns bunch spacing and 5.6ns bunch spacing, respectively. The detail of the hardware and the result of the beam test are reported.  
 
MOPWA017 Design of the 500 kA Linear Transformer Driver Stage simulation, pulsed-power, high-voltage, induction 696
 
  • T.X. Liang, X.F. Jiang, A.C. Qiu, F.J. Sun, Z.G. Wang, J.H. Yin, Z. Zhang
    NINT, Xi'an, People's Republic of China
  
  Funding: Supported by the funding of National Natural Science of China (Grant No. 51077111) and Stage Key Laboratory of Electrical Insulation and Power Equipment(Grant No.51077111) , Xi’an Jiaotong Univercity.
Linear transformer driver (LTD) is a novel fast discharge high pulsed power source. It can realize many LTD stages in series or parallel conveniently, and can directly acquire 100~200ns high power pulse. The pulse maybe realizes to directly drive load without any pulse compressing and forming unit. This paper introduces the latest development of fast LTD technology in abroad. The 100kV/500kA LTD stage with the rise time of 150ns has been designed. The stage is consisting of 20 discharging bricks in parallel. The simplified circuit model of LTD stage is given and the output parameters are simulated with universal circuit simulation software program, and the matched load current of 500kA and the rise time of about 150ns is obtained at the charging voltage of the capacitors about ±80kV.
Tianxue Liang is with the State Key Laboratory of Environment Simulation and Effect for Intense Pulsed Radiation, Northwest Institute of Nuclear Technology, P. O. Box 69-10, Xi’an 710024, China(phone:86-029-84767380; e-mail: liangtxlkk@163.com). 		 
 
MOPWA018 CW-type HV Power Supply of 50 Hz and its Application in Accelerator Power Supply high-voltage, electron, power-supply, impedance 699
 
  • Z.-F. He, D.M. Li, Y.H. Liu, S.L. Wang, J.-L. Zhang, Y.-T. Zhang
    SINAP, Shanghai, People's Republic of China
  
  Funding: The Knowledge Innovation Program of Chinese Academy of Sciences
　　The high-voltage power supply is an integral part of accelerator technology, as its stable and reliable output is an important guarantee for accelerator properly working. In a number of engineering practice of accelerator design and construction, we tried to use the Cockcroft-Walton (CW) type of power supply driven by 50 Hz and got success. It is of simple structure, low cost, easy maintenance, and high efficiency. This report describes the technical difficulties and the solutions in the CW-type power supply driven by 50 Hz. It also gives an introduction of the latest design of 800 kV/30 mA electron accelerator, which is being assembled at SINAP. Recent work has shown that it is an option to choose 50 Hz driven power system when it is more lenient on the voltage ripple but needed to be as high as possible on the energy conversion efficiency. 		 
 
MOPWA033 Modelling of Parasitic Inductances of a High Precision Inductive Adder for CLIC impedance, kicker, coupling, emittance 738
 
  • J. Holma, M.J. Barnes
    CERN, Geneva, Switzerland
  • S.J. Ovaska
    Aalto University, School of Science and Technology, Aalto, Finland
  
  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 pre-damping rings and damping rings will produce, through synchrotron radiation, ultra-low emittance beam with high bunch charge. To avoid beam emittance increase, the damping ring kicker systems must provide extremely flat, high-voltage, pulses. The specifications for the extraction kickers of the DRs are particularly demanding: the flat-top of the pulses must be ±12.5 kV with a combined ripple and droop of not more than ±0.02 % (±2.5 V). An inductive adder is a very promising approach to meeting the specifications. However, the output impedance of the inductive adder needs to be well matched to the system impedance. The primary leakage inductance, which cannot be computed accurately analytically, has a significant effect upon the output impedance of the inductive adder. This paper presents predictions, obtained by modelling the 3D geometry of the adder structure and printed circuit boards using the FastHenry code, for primary leakage inductance.  
 
MOPWA051 ZEMAX Simulations for an Optical System for a Diffraction Radiation Monitor at CesrTA target, radiation, simulation, electron 789
 
  • T. Aumeyr, V. Karataev
    JAI, Egham, Surrey, United Kingdom
  • M.G. Billing
    CLASSE, Ithaca, New York, USA
  • L.M. Bobb, B. Bolzon, T. Lefèvre, S. Mazzoni
    CERN, Geneva, Switzerland
  
  Diffraction Radiation (DR) is produced when a relativistic charged particle moves in the vicinity of a medium. The target atoms are polarized by the electric field of the charged particle, which then oscillate thus emitting radiation with a very broad spectrum. The spatial-spectral properties of DR are sensitive to various electron beam parameters. Since the energy loss due to DR is so small that the electron beam parameters are unchanged, DR can be used to develop non-invasive diagnostic tools. The aim of this project is to measure the transverse (vertical) beam size using incoherent DR. To achieve the micron-scale resolution required by CLIC, DR in the UV and X-ray spectral-range must be studied. During the next few years, experimental validation of such a scheme will be conducted on the CesrTA at Cornell University, USA. This paper reports on simulations carried out with ZEMAX, studying the optical system used to image the emitted radiation.  
 
MOPWO003 Multibunch Tracking Code Development to Account for Passive Landau Cavities cavity, electron, impedance, radiation 885
 
  • M. Klein, R. Nagaoka
    SOLEIL, Gif-sur-Yvette, France
  
  The MAX IV 3 GeV storage ring will achieve an ultra-low horizontal emittance of 0.24 nm rad by using a multibend achromat lattice. Passive harmonic cavities are introduced to relax the Touschek-lifetime and intrabeam scattering issues as well as fight collective beam instabilities via Landau damping. Since instabilities occur during injection, when the passive harmonic cavity potential is also time varying, it became important to simulate this transient process. The most promising approach was considered to be multibunch tracking which also allows for an arbitrary filling pattern. Since every bunch is represented by numerous macroparticles, internal motions as well as microstructures in the charge distribution can be followed.  
 
MOPWO011 Surface Field Optimization of Accelerating Structures for CLIC using ACE3P on Remote Computing Facility simulation, linac, GUI, target 909
 
  • K.N. Sjobak, E. Adli
    University of Oslo, Oslo, Norway
  • A. Grudiev
    CERN, Geneva, Switzerland
  
  Funding: Research Council of Norway
This paper presents a computer program for searching for the optimum shape of an accelerating structure cell by scanning a multidimensional geometry parameter space. For each geometry, RF parameters and peak surface fields are calculated using ACE3P on a remote high-performance computational system. Parameter point selection, mesh generation, result storage and post-analysis are handled by a GUI program running on the user’s workstation. This pa- per describes the program, AcdOptiGui. AcdOptiGui also includes some capability for automatically selecting scan points based on results from earlier simulations, which en- ables rapid optimization of a given parameterized geome- try. The software has previously been used as a part of the design process for accelerating structures for a 500 GeV CLIC. 		 
 
MOPWO022 Design and Manufacturing Description of the Prototype Striplines for the Extraction Kicker of the CLIC Damping Rings impedance, kicker, extraction, vacuum 930
 
  • C. Belver-Aguilar, A. Faus-Golfe
    IFIC, Valencia, Spain
  • M.J. Barnes
    CERN, Geneva, Switzerland
  • J. Gómez
    Trinos Vacuum Projects, Paterna, Spain
  • D. Gutiérrez Arribas
    Trinos Vacuum Projects, S.L., Paterna - Valencia, Spain
  • F. Toral
    CIEMAT, Madrid, Spain
  
  The Pre-Damping Rings (PDRs) and Damping Rings (DRs) of CLIC are needed to reduce the beam emittances to the small values required for the main linacs. The injection and extraction, from the PDRs and DRs, are carried out by kicker systems. In order to achieve both low beam coupling impedance and reasonable broadband impedance matching to the electrical circuit, striplines have been chosen for the kicker elements. The design of the stripline kicker was previously carried out by modelling the striplines with simulation codes such as HFSS, Quickfield and CST Particle Studio. In order to have a complete analysis of the striplines, the effect of electrodes supports and coaxial feedthroughs have been studied in detail. In this paper, electromagnetic analyses of the complete striplines, including fabrication tolerances, are reported. Furthermore, a new idea for impedance matching is presented.  
 
MOPWO024 Design of the CLIC Pre-Main Linac Collimation System collimation, emittance, linac, wakefield 936
 
  • R. Apsimon, A. Latina, D. Schulte, J.A. Uythoven
    CERN, Geneva, Switzerland
  • J. Resta-López
    IFIC, Valencia, Spain
  
  A main beam collimation system, upstream of the main linac, is essential to protect the linac from particles in the beam halo. The proposed system consists of an energy collimation (EC) system just after the booster linac near the start of the Ring-to-Main Linac (RTML) transfer line and an EC and betatron collimation (BC) system at the end of the RTML, just before the main linac. The design requirements are presented and the cleaning efficiency of the proposed systems is analysed for different design choices.  
 
MOPWO025 Optics and Protection of the Injection and Extraction Regions of the CLIC Damping Rings extraction, injection, kicker, septum 939
 
  • R. Apsimon, B. Balhan, M.J. Barnes, J. Borburgh, B. Goddard, Y. Papaphilippou, J.A. Uythoven
    CERN, Geneva, Switzerland
  
  The optics design of the injection and extraction regions for the CLIC damping rings is presented. The design defines the parameters for the kicker magnets and septa in these regions and has been optimised to minimise the length of the insertions within the parameter space of the system. Failure modes of the injection and extraction elements are identified and their severity assessed. Protection elements for the injection and extraction regions are optimised based on the conclusions of the failure mode analysis.  
 
MOPWO080 GPU-optimized Code for Long-term Simulations of Beam-beam Effects in Colliders simulation, luminosity, collider, electron 1064
 
  • Y. Roblin, V.S. Morozov, B. Terzić
    JLAB, Newport News, Virginia, USA
  • M. Aturban, D. Ranjan, M. Zubair
    ODU CS, Norfolk, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We report on the development of the new code for long-term simulation of beam-beam effects in particle colliders. The underlying physical model relies on a matrix-based arbitrary-order symplectic particle tracking for beam transport and the Bassetti-Erskine approximation for beam-beam interaction. The computations are accelerated through a parallel implementation on a hybrid GPU/CPU platform. With the new code, a previously computationally prohibitive long-term simulations become tractable. We use the new code to model the proposed medium-energy electron-ion collider (MEIC) at Jefferson Lab. 		 
 
MOPWO087 Parameter Estimation of the Exponentially Damped Sinusoid for Noisy Signals closed-orbit, neutron, feedback, synchrotron 1079
 
  • T.A. Pelaia
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725
The damped sinusoid equation is a common model for many scientific processes involving damped periodic signals. Here we present two methods for estimating the damped sinusoid parameters for noisy signals. Both methods are based upon an exact, closed form solution to fit the parameters for signals without noise, and they estimate the parameters for the noisy signals by the statistical maximum likelihood criterion. The first method relies on an optimizer to minimize the mean square signal error. The second method estimates the parameters by direct calculation and is suitable when the signal noise is small and the frequencies are sufficiently far from the integer and half integer values. 		 
 
TUYB102 Summary of the ILC R&D and Design positron, electron, linac, cavity 1101
 
  • B.C. Barish
    CALTECH, Pasadena, California, USA
  
  This talk should provide a summary of the main activities of ILC-GDE since 2005, and an overview of the Technical Design Report with prospects for the next steps for the future.  
slides icon Slides TUYB102 [6.544 MB]  
 
TUODB102 Intrabeam Scattering Studies for Low Emittance of BAPS emittance, wiggler, storage-ring, lattice 1123
 
  • S.K. Tian, Y. Jiao, J.Q. Wang, G. Xu
    IHEP, Beijing, People's Republic of China
  
  In modern storage ring light sources, intra-beam scattering (IBS) is often thought of as a fundamental limitation to achieving ultra-low emittance and hence higher brightness. Beijing Advanced Photon Source (BAPS) is under design at Institute of High Energy Physics (IHEP) which aims to emittance less than 1nm at 5GeV. To improve the coherence and high brightness, low emittance- in both transverse planes at the diffraction limit for the range of x-ray wavelengths(≈10 pm)- is being pursued. Thus, due to the very low emittance, intra-beam scattering effect is an issue. Accurate estimation to check if the design goal can be reached is necessary. In this paper, we use the 6-D accelerator simulation code-elegant and Accelerator Toolbox (AT)-a collection of tools to model storage rings in the MATLAB environment. Based on a temporary design lattice of BAPS, we present the results of particle simulation study of intra-beam scattering effect versus the beam energy, the emittance coupling factor, the bunch length, the bunch current and so on. We also studied the mitigating method by adopting damping wigglers in one or more dispersion-free regions.  
slides icon Slides TUODB102 [2.338 MB]  
 
TUODB103 Recent Results from CesrTA Intrabeam Scattering Investigations emittance, coupling, simulation, scattering 1126
 
  • M. P. Ehrlichman, A. Chatterjee, W. Hartung, D.P. Peterson, N.T. Rider, D. L. Rubin, D. Sagan, J.P. Shanks, S. Wang
    CLASSE, Ithaca, New York, USA
  
  Funding: This research was supported by NSF and DOE contracts PHY-0734867, PHY-1002467, PHYS-1068662, DE-FC02-08ER41538, DE-SC0006505.
Manifestation of intrabeam scattering (IBS) in an electron/positron storage ring depends on the radiation damping time in two ways. First, the beam size is the equilibrium of the IBS growth rate in each of the three degrees of freedom and corresponding damping rates. Second, scattering events that occur less frequently than order once per damping time contribute to non-Gaussian tails that are invisible to our beam size monitors. The tail cut procedure excludes these relatively rare events in the calculation of equilibrium beam size. In machines with short damping times, the tail cut significantly reduces the effective IBS growth rate. At CesrTA, we measure the dependence of beam size on bunch charge in IBS-dominated beams. We vary the vertical emittance using a closed optics bump that increases the vertical dispersion and transverse coupling in the wiggler regions. Measurements are taken at both 2.1 and 2.3 GeV. Here we report the results of these experiments and compare those results to theory. 		 
slides icon Slides TUODB103 [1.221 MB]  
 
TUPFI031 Effect of Collision Pattern in the LHC on the Beam Stability: Requirements from Experiments and Operational Considerations luminosity, injection, proton, collider 1409
 
  • W. Herr, G. Arduini, R. Giachino, E. Métral, G. Papotti, T. Pieloni
    CERN, Geneva, Switzerland
  • X. Buffat, N. Mounet
    EPFL, Lausanne, Switzerland
  • S.M. White
    BNL, Upton, Long Island, New York, USA
  
  Coherent instabilities of bunches in the LHC bunch train can be observed when the tune spread from beam-beam interactions becomes insufficient to ensure Landau damping. In particular these effects are seen on bunches with a reduced number of beam-beam interactions due to their collision pattern. Furthermore, such a reduction of the necessary stability can occur during the processes when the beams are prepared for collisions or during the optimization procedure. We discuss the observations and possible countermeasures, in particular alternatives to the existing beam manipulation processes where such a situation can occur.  
 
TUPFI032 Observation of Instabilities in the LHC due to Missing Head-on Beam-beam Interactions octupole, luminosity, beam-beam-effects, betatron 1412
 
  • W. Herr, G. Arduini, R. Giachino, E. Métral, G. Papotti, T. Pieloni
    CERN, Geneva, Switzerland
  • X. Buffat, N. Mounet
    EPFL, Lausanne, Switzerland
  
  We report the observation of coherent instabilities on individual bunches out of the LHC bunch train. These instabilities occured spontaneously after several hours of stable beam while in other cases they were related to the application of a small transverse beam separation during a luminosity optimization. Only few bunches were affected, depending on there collision scheme and following various tests we interprete these instabilities as a sudden loss of Landau damping when the tune spread from the beam-beam interaction became insufficient.  
 
TUPFI034 Observations of Two-beam Instabilities during the 2012 LHC Physics Run octupole, betatron, impedance, luminosity 1418
 
  • T. Pieloni
    EPFL, Lausanne, Switzerland
  • G. Arduini, X. Buffat, R. Giachino, W. Herr, M. Lamont, N. Mounet, E. Métral, G. Papotti, B. Salvant, J. Wenninger
    CERN, Geneva, Switzerland
  • S.M. White
    BNL, Upton, Long Island, New York, USA
  
  During the 2012 run coherent beam instabilities have been observed in the LHC at 4 TeV, during the betatron squeeze and in collision for special filling patterns. Several studies to characterize these instabilities have been carried out during operation and in special dedicated experiments. In this paper we summarize the observations collected for different machine parameters and the present understanding of the origin of these instabilities.  
 
TUPFI035 Head-on and Long range Beam-beam Interactions in the LHC: Effective Tune Spread and Beam Stability due to Landau Damping octupole, luminosity, lattice, feedback 1421
 
  • X. Buffat
    EPFL, Lausanne, Switzerland
  • W. Herr, N. Mounet, E. Métral, T. Pieloni
    CERN, Geneva, Switzerland
  
  We discuss the Landau damping of coherent instabilities in the presence of betatron tune spread. This tune spread can originate from dedicated non-linear magnets such as octupoles, or through the beam-beam interaction. In the latter case we have to distinguish the contribution from head-on and parasitic beam-beam interactions and the collision pattern of different bunches plays an important role. The interplay of these sources of tune spread and the resulting stability is discussed for the case of the LHC.  
 
TUPFI036 Observation of Beam Instabilities with Very Tight Collimation impedance, collimation, proton, octupole 1424
 
  • H. Burkhardt, N. Mounet, T. Pieloni
    CERN, Geneva, Switzerland
  
  We report about the observation of instabilities in the LHC in special runs with high β* and very tight collimation down to 2 σ which increases the transverse impedance significantly. The losses appeared primarily on the highest intensity, non-colliding bunches which can be interpreted as evidence for insufficient Landau damping. We describe the beam conditions, observations and possible explanations for the observed effects.  
 
TUPFI042 Beam Parameters and Luminosity Time Evolution for an 80-km VHE-LHC emittance, luminosity, radiation, collider 1442
 
  • C.O. Domínguez, F. Zimmermann
    CERN, Geneva, Switzerland
  
  The Very High Energy LHC (VHE-LHC) is a recently proposed proton-proton collider in a new 80-km tunnel. With a dipole field of 15-20 T it would provide a collision energy of 76-100 TeV c.m. We discuss the VHE-LHC beam parameters and compute the time evolution of luminosity, beam current, emittances, bunch length, and beam-beam tune shift during a physics store. The results for VHE-LHC are compared with those for HE-LHC, a 33-TeV (20-T field) collider located in the existing LHC tunnel.  
 
TUPME002 Design Integration at the International Linear Collider lattice, positron, electron, civil-engineering 1559
 
  • B. List, L. Hagge, J. Kreutzkamp, N.J. Walker
    DESY, Hamburg, Germany
  
  In preparation for the Technical Design Report of the International Linear Collider, a comprehensive design of the accelerator has been compiled. DESY has contributed a systematic design integration approach, which helps to achieve a complete, correct and consistent design. We use the lattice as the leading element for design integration. Geometry information including 3D visualization models are derived from the lattice, and are used to ensure that the beamlines fit and suited for access and installation. The 3D models are also used as basis for tunnel and cavern layout. As detailed designs of components become available, the lattice is adjusted and the overall models are iterated. Lists of components are derived from the lattice and are used to generate a component bill of materials, which in turn serves as basis for cost estimation and installation planning. An integrated 3D model of the entire accelerator and all the civil construction elements helps to optimize the design for example with regard to space efficiency, ease of access for installation, and life safety. Setting up design integration in an early project stage results in a better design helps to reduce costs.  
 
TUPME004 Spin Tracking at the International Linear Collider resonance, dipole, polarization, positron 1565
 
  • V.S. Kovalenko, G.A. Moortgat-Pick, A. Ushakov
    University of Hamburg, Hamburg, Germany
  • S. Riemann
    DESY Zeuthen, Zeuthen, Germany
  • M. Vogt
    DESY, Hamburg, Germany
  • A. Wolski
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  Funding: This work is supported by the German Federal Ministry of Education and Research, Joint Research Project R&D Accelerator "Spin Optimization", contract number 19XL7Ic4
In the baseline design for the International Linear collider an helical undulator-based positron source has been chosen that can provide positrons with a polarization of 60% as an upgrade option motivated by physics reasons. But even the baseline configuration would already provide about 30%. In order to match the high precision requirements from physics and to optimize the physics outcome one has to control systematic uncertainties to a very high level. Therefore it is needed to run both beams polarized but provide also an unpolarized set-up for control reasons. In our study we present results on precise spin tracking and propose also an minimal machine set-up to run in an unpolarized mode within the baseline design. 		 
 
TUPME005 Preparations for Beam Tests of a CLIC Damping Wiggler Prototype at ANKA wiggler, emittance, target, storage-ring 1568
 
  • A. Bernhard, E. Huttel, P. Peiffer
    KIT, Karlsruhe, Germany
  • A.V. Bragin, N.A. Mezentsev, V.M. Syrovatin, K. Zolotarev
    BINP SB RAS, Novosibirsk, Russia
  • P. Ferracin, D. Schoerling
    CERN, Geneva, Switzerland
  
  The Compact Linear Collider (CLIC) will require ultra-low emittance electron and positron beams. The targeted emittance will be achieved by radiative damping in the CLIC damping rings. For an efficient damping high-field short-period superconducting damping wigglers will be employed. In the conceptual design phase of CLIC, the basic layout of these wigglers has been elaborated at CERN. In the course of the CLIC technical feasibility studies a full-scale damping wiggler prototype will be installed and tested in the ANKA storage ring. The device is currently under design and construction at the Budker Institute of Nuclear Physics, Russia. Above the magnetic requirements, the main design challenges for the prototype are scalability –- particularly of the cooling concept –-, modularity and the capability of sustaining a high radiative heat load. The experiments at ANKA aim at a validation of the technical concepts applied to meet these requirements. Beyond that an extended experimental program on beam dynamics and alternative technical solutions is envisaged. This contribution gives an overview over the current status of the project and the further planning.  
 
TUPME009 Measurement and Vibration Studies on the Final Focus Doublet at DAΦNE and new collider Implications collider, luminosity, resonance, factory 1580
 
  • S. Tomassini
    INFN/LNF, Frascati (Roma), Italy
  
  Funding: Work supported by the European Commission under the FP7 Research Infrastructures project Eu-CARD, grant agreement no. 227579.
A Super Flavour Factory, to be built in the Tor Vergata University campus near Frascati, Italy, will have nano-beams in order to reach the design luminosity. The knowledge and compensation of the vibrations induced on the beams by the anthropic noise is then fundamental. The DAΦNE Phi-factory at LNF, Frascati, was upgraded in the second half of 2007 in order to implement the large Piwinski angle and crab waist collision scheme and in 2010 the KLOE experiment was rolled in for a new data taking and physic program. A measurement campaign has been performed on DAΦNE to find out the actual vibration sensitivity of the final focus doublets. Vibration measurements were performed on the Final Focus doublet because of luminosity losses and photon beam lines instability evidences. Results and stabilization technique to mitigate the effects of the ground motion induced by the “cultural noise” are presented. Implications on the design and stabilization of a Flavour Factory Final Focus doublets will be discussed. 		 
 
TUPME014 Coherent Synchrotron Radiation Predicted at the SuperKEKB Damping Ring linac, vacuum, emittance, simulation 1595
 
  • H. Ikeda, M. Kikuchi, K. Ohmi, K. Oide, D. Zhou
    KEK, Ibaraki, Japan
  
  The damping ring of SuperKEKB is under construction in order to inject low emittance positron beam into the main ring. We calculated the bunch lengthening and the energy spread caused by the longitudinal wake, which is dominated by the CSR wake field. The result was within the tolerance level.  
 
TUPME017 Validation of the Microwave Instability in the Damping Ring of SuperKEKB using VFP Solver impedance, simulation, wakefield, synchrotron 1604
 
  • L. Wang
    SLAC, Menlo Park, California, USA
  • H. Ikeda, K. Ohmi, K. Oide, D. Zhou
    KEK, Ibaraki, Japan
  
  Microwave instability driven by CSR impedance in the damping ring of Super-KEKB is a concern due to its high bunch current. To understand the beam dynamics, we simulate the microwave instability using Vlasov-Fokker-Planck (VFP) solver. The longitudinal wake potential is calculated as a sum of the contributions due to vacuum chamber components distributed around the ring, including geometry wake field and CSR wake. To improve the accuracy of the simulation of microwave instability, the coherent synchrotron radiation impedance is calculated to very high frequency to get more accurate wake field with a short bunch. The CSR wake is much larger than the geometry wake. The threshold is just above the design current and saw-tooth type of instability is found above the threshold.  
 
TUPME042 The SPS as an Ultra-low Emittance Damping Ring Test Facility for CLIC emittance, wiggler, optics, target 1661
 
  • Y. Papaphilippou, R. Corsini, L.R. Evans
    CERN, Geneva, Switzerland
  
  In view of the plans for a future electron/positron linear collider based on the CLIC technology, an ultra-low emittance damping ring test facility is proposed, using the CERN SPS. Optics modification, required wiggler length and characteristics, energy and RF parameters are presented in order to reach CLIC performance requirements, including the effect of Intrabeam Scattering. Considerations about the necessary injected beam characteristics, its production and transfer through the existing CERN accelerator complex are also discussed.  
 
TUPME045 Turn-by-turn Measurements in the KEK-ATF synchrotron, injection, betatron, emittance 1664
 
  • Y. Renier, Y. Papaphilippou, R. Tomás, M. Wendt
    CERN, Geneva, Switzerland
  • N. Eddy
    Fermilab, Batavia, USA
  • K. Kubo, S. Kuroda, T. Naito, T. Okugi, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  
  The ATF damping ring has been upgraded with new read-out electronics for the beam position monitors (BPM), capable to acquire the beam orbits on a turn-by-turn basis, as well as in a high resolution averaging mode. The new BPM system allows to improve optic corrections and to achieve an even smaller vertical emittance (<2pm). Experimental results are presented based on turn-by-turn beam orbit measurements in the ring, for estimating the beta functions and dispersion along the lattice. A fast method to measure spectral line amplitude in a few turns is also presented, including the evaluation of chromaticity.  
 
TUPME056 3.5 GeV Superconducting Stacking Ring for Compton Based Polarized Positrons Source of CLIC positron, injection, synchrotron, emittance 1697
 
  • E.V. Bulyak, P. Gladkikh, A.A. Kalamayko
    NSC/KIPT, Kharkov, Ukraine
  • T. Omori, J. Urakawa, K. Yokoya
    KEK, Ibaraki, Japan
  • L. Rinolfi, F. Zimmermann
    CERN, Geneva, Switzerland
  
  This paper describes 3.5 GeV superconducting storage ring dedicated to positron accumulation as part of a polarized positron source for CLIC, based on Compton scattering in a Compton storage ring. The superconducting stacking ring can provide a synchrotron damping time of order 250 microseconds. Together with combined injection scheme in the longitudinal and transverse plane, such a ring may solve the problem of accumulating a positron beam with efficiency close to 95 % and with the beam intensity required for CLIC.  
 
TUPME061 Emittance Growth with Crab Cavity and Damper Noise in LHC emittance, simulation, pick-up, resonance 1706
 
  • S. Paret, J. Qiang
    LBNL, Berkeley, California, USA
  
  Funding: This work was partially supported by the U.S. LARP and the NERSC of the U.S. Department of Energy under contract No. DE-AC02-05CH11231.
Strong-strong beam-beam simulations are employed to investigate the noise sensitivity of the emittance in the future High Luminosity (HL)-LHC. Noise in the accelerator causes fluctuations of the bunch centroids at the interaction points (IPs) which cause emittance growth for large beam-beam parameters. Two noise sources are examined: Crab cavities and the transverse damper. The damper noise is adjusted to bring simulations in agreement with an emittance measurement in a past LHC run. Results from simulations with HL-LHC beam parameters using different noise levels, damper gains and working points are discussed. 		 
 
TUPME066 CESR Low Emittance Upgrade with Combined Function Bends wiggler, quadrupole, emittance, focusing 1718
 
  • D. L. Rubin, Y. Li, A.A. Mikhailichenko, S. Wang
    CLASSE, Ithaca, New York, USA
  
  Funding: Work supported by the National Science Foundation and Department of Energy under contract numbers PHY-1002467, DMR-0936384 and DE-SC0006505
The Cornell Electron Storage Ring is the laboratory for the CESR Test Accelerator damping ring R&D program, and the source of x-rays for CHESS. A peculiarity of the layout of the storage ring is that horizontal emittance is generated predominantly by the strong bends in the sextant of the ring that was designed with a long straight to accommodate the interaction region required for operation as an electron-positron collider. By reconfiguring that single sextant we reduce the emittance by 60% to 20 nm-rad at 5.3 GeV for x-ray production and with damping wigglers to 1.3 nm-rad at 2.1 GeV for investigations of low emittance phenomena. The 35 meter radius of curvature, 3.2 meter long dipoles are refitted as combined function (vertically focusing) magnets to create simple achromats. The layout can accommodate six, 3 meter long undulators, in addition to the six existing superconducting damping wigglers. With reduced horizontal emittance and energy spread, the reconfiguration enhances the sensitivity of CESR to the emittance diluting effects that are the subject of the CesrTA study. Capability of the x-ray source is significantly improved with six new undulator beam lines. 		 
 
TUPWA005 Study of Collective Beam Instabilities for the MAX IV 3 GeV Ring impedance, simulation, vacuum, wakefield 1730
 
  • M. Klein, R. Nagaoka
    SOLEIL, Gif-sur-Yvette, France
  • G. Skripka, P.F. Tavares, E.J. Wallén
    MAX-lab, Lund, Sweden
  
  The present paper reports on a systematic simulation study made on the collective beam instability in the MAX IV 3 GeV ring. We study both single and multibunch instabilities in the longitudinal plane. Specifically, we focus on the microwave instabilities which are considered to be particularly dangerous for MAX IV, in view of its small effective radius of aperture (beff < 11 mm), the high intensity (500 mA) and the low emittance (0.24 nm.rad) nature of the circulating beam. Single and multibunch tracking are performed using wake fields that were numerically obtained using GdfidL for the ensemble of the vacuum components. A special effort was made to include dynamically the effect of harmonic cavities that lengthen the bunch and introduce Landau damping, whose details are described in the companion paper *. The study aims to confirm the effectiveness of storing long bunches in the 100 MHz RF system, where tune spreads are further increased by the harmonic cavities, in order to fight against collective instabilities.
* M. Klein and R. Nagaoka "Multibunch Tracking Code Development to Account for Passive Landau Cavities", these proceedings 		 
 
TUPWA013 Study of the C-ADS Longitudinal Beam Instabilities Caused by HOMS HOM, linac, emittance, simulation 1751
 
  • P. Cheng, Z. Li, J.Y. Tang, J.Q. Wang
    IHEP, Beijing, People's Republic of China
  
  The C-ADS accelerator is a CW proton linac which accelerates the beam to 1.5GeV. It has the characteristics of being very high beam power and very high reliability that are not posed by any of the existing proton linacs. The accelerator uses two families (β=0.63 and β=0.82 ) of elliptical five cell superconducting cavities. High Order Modes can severely limit the operation of these cavities. Monopole modes are found by Microwave Studio CST. Then the longitudinal instability caused by these monopole modes are primarily investigated with code bbusim, taking into account of effects like High Order Modes frequency spread, beam input jitters and other beam and RF parameters of the beams and cavities. Preliminary simulation results show that monopole modes induced instability is not a problem if High Order Modes frequency spread is not less than 1MHz. However, further investigations are necessary in order to make a critical decision such as whether HOM damper will be adopted. Study on the transverse case is under way.  
 
TUPWA038 Equilibrium Bunch Density Distribution with Passive Harmonic Cavities in the MAX IV 3 GeV Storage Ring cavity, impedance, storage-ring, emittance 1790
 
  • P.F. Tavares, Å. Andersson, A. Hansson
    MAX-lab, Lund, Sweden
  
  The MAX IV storage rings will use third harmonic cavities operated passively to lengthen the bunches and alleviate collective instabilities. These cavities are an essential ingredient in the MAX IV design concept and are required for achieving the final design goals in terms of stored current, beam emittance and beam lifetime. This paper reports on fully self-consistent calculations of the longitudinal bunch density distribution in the MAX IV 3 GeV storage ring, which indicate that up to a factor 5 increase in RMS bunch length is achievable with a purely passive system.  
 
TUPWA040 Loss of Landau Damping for Inductive Impedance in a Double RF System emittance, synchrotron, simulation, impedance 1796
 
  • T. Argyropoulos, E.N. Shaposhnikova
    CERN, Geneva, Switzerland
  • A.V. Burov
    Fermilab, Batavia, USA
  
  In this paper the thresholds of the loss of Landau damping due to the presence of inductive impedance in a single and double harmonic RF systems are determined, both from calculations and particle simulations. High harmonic RF system, operating in bunch lengthening mode is used in many accelerators with space charge or inductive impedance to reduce the peak line density or stabilize the beam. An analytical approach, based on emerging of the discrete Van Kampen modes, shows that improved stability in a double RF system can be achieved only below some critical value of longitudinal emittance. Above this threshold, a phase shift of more than 15 degrees between the two RF components is proven to stabilize the bunch. These results, confirmed also by particle simulations, are able to explain now observations during the ppbar operation of the SPS. The thresholds in bunch shortening mode as well as in a single RF case are compared with this regime.  
 
TUPWA042 Lessons Learned and Mitigation Measures for the CERN LHC Equipment with RF Fingers impedance, resonance, vacuum, simulation 1802
 
  • E. Métral, O. Aberle, R.W. Aßmann, V. Baglin, M.J. Barnes, O.E. Berrig, A. Bertarelli, G. Bregliozzi, S. Calatroni, F. Carra, F. Caspers, H.A. Day, M. Ferro-Luzzi, M.A. Gallilee, C. Garion, M. Garlaschè, A. Grudiev, J.M. Jimenez, O.R. Jones, O. Kononenko, R. Losito, J.L. Nougaret, V. Parma, S. Redaelli, B. Salvant, P.M. Strubin, R. Veness, C. Vollinger, W.J.M. Weterings
    CERN, Geneva, Switzerland
  
  Beam-induced RF heating has been observed in several LHC components when the bunch/beam intensity was increased and/or the bunch length reduced. In particular eight bellows, out of the ten double-bellows modules present in the machine in 2011, were found with the spring, which should keep the RF fingers in good electrical contact with the central insert, broken. Following these observations, the designs of all the components of the LHC equipped with RF fingers have been reviewed. The lessons learnt and mitigation measures are presented in this paper.  
 
TUPWA044 Longitudinal Coupled-Bunch Oscillation Studies in the CERN PS feedback, kicker, cavity, emittance 1808
 
  • H. Damerau, S. Hancock, M.M. Paoluzzi
    CERN, Geneva, Switzerland
  • M. Migliorati, L. Ventura
    Rome University La Sapienza, Roma, Italy
  
  Longitudinal coupled-bunch oscillations are an important limitation for the high-brightness beams accelerated in the CERN PS. Up to the present intensities they are suppressed by a dedicated feedback system limited to the two dominant oscillation modes. In view of the proposed installation of a wide-band feedback kicker cavity within the framework of the LHC Injectors Upgrade project (LIU), measurements have been performed with the existing damping system with the aim of dimensioning the new one. Following the excitation of well-defined oscillation modes, damping times and corresponding longitudinal kick strength are analysed. The paper summarizes the results of the observations and gives an outlook on the expected performance with the new coupled-bunch feedback.  
 
TUPWA062 Dependence of Beam Instabilities Caused by Electron Clouds at CesrTA on Variations in Bunch Spacing and Chromaticity electron, dipole, positron, resonance 1844
 
  • M.G. Billing, K.R. Butler, G. Dugan, M.J. Forster, R.E. Meller, M.A. Palmer, G. Ramirez, 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.W. Flanagan
    KEK, Ibaraki, Japan
  
  Funding: Work supported by DOE Award DE-FC02-08ER41538, NSF Award PHY-0734867 and the Lepton Collider R&D Coop Agreement: NSF Award PHY-1002467
Experiments have been performed at the Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) to probe the interaction of the electron cloud with a 2.1 Gev stored positron beam. The purpose of these experiments was to characterize the dependence of beam–electron cloud interactions on the bunch spacing and the vertical chromaticity. These experiments were performed on a 30-bunch positron train, at a fixed current of 0.75mA/bunch. The bunch spacing was varied between 4 and 28 ns at three different vertical chromaticity settings. The beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using: 1) a gated Beam Position Monitor (BPM) and spectrum analyzer to measure the bunch-by-bunch frequency spectrum of the bunch trains; 2) an x-ray beam size monitor to record the bunch-by-bunch, turn-by-turn vertical size of each bunch within the trains. In this paper we report on the observations from these experiments and analyze the effects of the electron cloud on the stability of bunches within these different trains. 		 
 
TUPWA069 Longitudinal Phase Space Dynamics with Novel Diagnostic Techniques at FACET linac, wakefield, klystron, radiation 1865
 
  • S.J. Gessner, E. Adli, F.-J. Decker, M.J. Hogan, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  • A. Scheinker
    LANL, Los Alamos, New Mexico, USA
  
  Funding: Work supported [optional: in part] by the U.S. Department of Energy under contract number DE-AC02-76SF00515.
FACET produces high energy density electron beams for Plasma Wakefield Acceleration (PWFA) experiments. The high energy density beams are created by chirping the electron beam with accelerating sections and compressing the beam in magnetic chicanes. Precise control of the longitudinal beam profile is needed for the drive-witness bunch PWFA experiments currently underway at FACET. We discuss the simulations, controls, and diagnostics used to achieve FACET's unique longitudinal phase space. 		 
 
TUPWO063 Reducing HLS-II Emittance by Radiation Damping Partition Factor Exchange wiggler, emittance, storage-ring, lattice 2009
 
  • J.Y. Li
    FEL/Duke University, Durham, North Carolina, USA
  • W. Li, G. Liu, W. Xu
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • Y. Li
    BNL, Upton, Long Island, New York, USA
  
  Funding: The Introduction of Outstanding Technological Talents Program of Chinese Academy of Sciences, 2010.
In this paper, we present a preliminary study on using a Robinson wiggler, a wiggler with transverse gradient, to reduce the horizontal beam emittance of the Hefei Light Source II (HLS-II) storage ring. A proof-of-principle study demonstrates that it is possible to further reduce the horizontal beam emittance by 50\% using a 2-meter long Robinson wiggler installed on a dispersive straight section. This encouraging result suggests a feasible option to significantly improve the HLS-II performance at a relative low cost and without significant modification to its global configuration in the near future. 		 
 
TUPWO065 Anomalously Long Bunches from the SLAC North Damping Ring electron, linac, simulation, klystron 2015
 
  • G. Yocky, F.-J. Decker, N. Lipkowitz, U. Wienands, M. Woodley
    SLAC, Menlo Park, California, USA
  
  The SLC damping ring provides emittance reduced beam to the beginning of the FACET accelerator. In measurements conducted during the 2012 FACET run, we find the bunch-length to be ~20% longer than canonical. A study is performed with longitudinal simulation code to determine the impact on the various stages of compression for FACET experimental running.  
 
WEOAB102 CSR-driven Longitudinal Single Bunch Instability Thresholds impedance, synchrotron, resonance, electron 2041
 
  • P. Kuske
    BESSY GmbH, Berlin, Germany
  
  According to Bane, et al.* threshold currents should follow a quite simple scaling law. More detailed theoretical results for the underlying shielded CSR-interaction have been performed for BESSY-II and the MLS and will be presented in comparison with observations at these storage rings. It is found that there are parameter regions where the instability is weak and thus thresholds depend on damping time and synchrotron tune. Theoretical findings are in surprisingly good agreement with most of the observed instability features.
* K.L. Bane, et al., Phys. Rev. ST-AB 13, 104402 (2010) 		 
slides icon Slides WEOAB102 [0.779 MB]  
 
WEPWA001 Wigglers at Danfysik wiggler, electron, radiation, emittance 2123
 
  • C.W.O. Ostenfeld, M. Pedersen
    Danfysik A/S, Taastrup, Denmark
  
  In the past 2 years, a number of insertion devices have been designed, assembled and tested at Danfysik. They are used for a variety of applications at free electron lasers and synchrotron radiation facilities. In this paper, we highlight 3 different wiggler projects: A 2.0 T wiggler for Astrid-II in Århus, Denmark, a fixed-gap electromagnetic wiggler for Helmholtz Center Dresden-Rossendorf, and 6 identical damping wigglers for NSLS-2 at Brookhaven National Laboratory (BNL). For the Astrid-2 facility in Aarhus, Denmark, we have designed and built a 6 period wiggler, with a peak field of 2.0 T. The magnetic design and performance is presented and discussed. As part of the ELBE THz facility, at Helmholtz Center Dresden-Rossendorf, we have designed and built a fixed-gap electromagnetic wiggler, with 300 mm period length, and a peak field of 0.39 T. We present the design and magnetic results. For the NSLS-2 project at BNL, damping wigglers are an integral part of the design, both as a means of reducing the emittance, but also as a source of intense radiation sources for users. We present the mechanical and magnetic design, as well as magnetic results obtained for the wigglers.  
 
WEPWO026 HOM Parameters Simulation and Measurement Result of the IHEP02 Low-loss Cavity HOM, cavity, dipole, wakefield 2372
 
  • H.J. Zheng, J. Gao, S. Jin, Y. Liu, Z.C. Liu, Z.H. Mi, J.Y. Zhai, T.X. Zhao
    IHEP, Beijing, People's Republic of China
  • H. Yuan
    BIAM, Beijing, People's Republic of China
  
  In cavities , there exists not only the fundamental mode which is used to accelerate the beam but also higher order modes(HOMs). The higher order modes excited by beam can seriously affect beam quality, especially for the higher R/Q mode. This paper reports on recent measurements of higher order modes in the IHEP-2 low-loss SRF cavity. Using different methods, the Qext of the dangerous modes passband are got. This result is compared with TESLA result. R/Q of the first three passbands are also got by CST and compared with the results of TESLA cavity and STFBaseline cavity.  
 
WEPWO048 Investigation of a Ridge-loaded Waveguide Structure for CLIC X-band Crab Cavity cavity, HOM, beam-loading, impedance 2411
 
  • V.F. Khan, R. Calaga, A. Grudiev
    CERN, Geneva, Switzerland
  
  In conventional crab cavities the TM11 mode is used to deflect the beam. In a linear collider such as CLIC, it is necessary to damp all the other modes, namely the accelerating i.e. lower order mode (LOM), same order mode (SOM) and higher order modes (HOMs). In addition to this, as the TM11 mode is not the fundamental mode, it is generally not excited with the highest shunt impedance. This necessitates damping of the high shunt impedance modes to acceptable level. Here we report on the investigation of an alternative design of the X-band crab cavity for CLIC based on ridge-loaded waveguide. In this type of cavity, the deflecting mode is the fundamental mode and has the maximum shunt impedance. However, the geometry of the cavity is chosen to optimise the ratio of group velocity to shunt impedance to minimise the effect of beam loading. The other modes are excited above the crabbing mode and are damped using wave-guides. Another advantage of this type of cavity is, unlike the conventional TM11 mode cavities, the e.m. surface fields do not peak at the iris. This provides ample margin to optimise the cavity geometry and reach the desired field distribution.  
 
WEPWO059 Cornell's HOM Beamline Absorbers HOM, linac, cavity, cryomodule 2441
 
  • R. Eichhorn, J.V. Conway, Y. He, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, P. Quigley, J. Sears, V.D. Shemelin, N.R.A. Valles
    CLASSE, Ithaca, New York, USA
  
  The proposed energy recovery linac at Cornell aims for high beam currents and short bunch lengths, the combination of which requires efficient damping of the higher order modes (HOMs) being present in the superconducting cavities. Numerical simulations show that the expected HOM power could be as high as 200 W per cavity with frequencies ranging to 40 GHz. Consequently, a beam line absorber approach was chosen. We will review the design, report on first results from a prototype and discuss further improvements.  
 
WEPWO060 The CW Linac Cryo-module for Cornell’s ERL linac, cavity, HOM, status 2444
 
  • R. Eichhorn, Y. He, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
    CLASSE, Ithaca, New York, USA
  
  Cornell University has proposed an energy-recovery linac (ERL) based synchrotron-light facility which can provide greatly improved X-ray beams due to the high electron-beam quality that is available from a linac. As part of the phase 1 R&D program, critical challenges in the design were addressed, one of them being a full linac cryo-module. It houses 6 superconducting cavities- operated at 1.8 K in cw mode- HOM absorbers and a magnet/ BPM section. We will present the design being finalized recently and report on the fabrication status that started in late 2012.  
 
WEPWO072 HOM Damping Coupler Design for the 400-MHz RF Dipole Compact Crab Cavity for the LHC HiLumi Upgrade HOM, cavity, dipole, coupling 2468
 
  • Z. Li, L. Ge
    SLAC, Menlo Park, California, USA
  • S.U. De Silva, J.R. Delayen
    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.
Crab cavities are adapted as the baseline design for the LHC HiLumi upgrade to achieve head-on beam-beam collisions for further improvement in luminosity. A 400-MHz compact RF dipole crab cavity design was developed by a joint effort between Old Dominion University and SLAC under the support of US LARP program. This design has shown very favorable RF parameters and can fit into the available beamline spacing for either vertical and horizontal crabbing schemes. A niobium prototype cavity based on such a design has been manufactured for vertical test. In addition, there are stringent wakefield requirements that needed to be met for such a cavity in order to preserve the quality of the circulating beams. In this paper, we will discuss different damping schemes for such a compact design and present the HOM coupler designs to meet the damping requirements. 		 
 
WEPEA027 Nonlinear Model Calibration in Electron Storage Rings via Frequency Analysis radiation, sextupole, betatron, storage-ring 2558
 
  • G. Liu, W. Li, L. Wang, K. Xuan
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  Frequency analysis of turn-by-turn BPM data is a very useful numerical method for analysing the detrimental effect of the nonlinear resonances in storage rings, and which has been widely used for nonlinear resonances measurement and correction. We applied this method in this paper for calibrating the nonlinear model by numerical fitting of the sextupole components with the effect of radiation damping and decoherence of the betatron oscillation in HLSII storage ring.  
 
WEPFI006 Broad and Narrow Band Feedback Systems at ELSA feedback, cavity, kicker, HOM 2714
 
  • M. Schedler, F. Frommberger, P. Hänisch, W. Hillert, C. Reinsch
    ELSA, Bonn, Germany
  
  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 6 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. In addition, a narrow band cavity based feedback system for damping the most harmful longitudinal multi bunch mode caused by a HOM of the accelerating cavities is under construction.  
 
WEPFI013 The Damped C-band RF Structures for the European ELI-NP Proposal linac, beam-loading, dipole, photon 2726
 
  • D. Alesini, R. Boni, R. D. Di Raddo, V.L. Lollo, B. Spataro, C. Vaccarezza
    INFN/LNF, Frascati (Roma), Italy
  • L. Ficcadenti, V. Pettinacci
    INFN-Roma, Roma, Italy
  • M. Migliorati, A. Mostacci, L. Palumbo
    URLS, Rome, Italy
  • L. Serafini
    Istituto Nazionale di Fisica Nucleare, Milano, Italy
  
  The gamma beam system of the European ELI-NP proposal foresees the use of a multi-bunch train colliding with a high intensity recirculated laser pulse. The linac energy booster is composed of 14 travelling wave C-Band structures, 1.8 m long with a field phase advance per cell of 2π/3 and a repetition rate of 100 Hz. Because of the multi-bunch operation, the structures have been designed with a damping of the HOM dipoles modes in order to avoid beam break-up (BBU). In the paper we discuss the design criteria of the structures also illustrating the effectiveness of the damping in the control of the BBU. Prototype activity is finally illustrated.  
 
WEPFI018 Comparison of High Gradient Performance in Varying Cavity Geometries vacuum, coupling, acceleration, HOM 2741
 
  • T. Higo, T. Abe, Y. Arakida, Y. Higashi, S. Matsumoto, T. Shidara, T. Takatomi, M. Yamanaka
    KEK, Ibaraki, Japan
  • A. Grudiev, G. Riddone, W. Wuensch
    CERN, Geneva, Switzerland
  
  Four types of CLIC prototype TW accelerator structures were high-gradient tested at Nextef, KEK, up to 100 MV/m level and the fifth is under test now. The ramping speed of each processing and the resultant breakdown rate were compared among them. From this comparison, it was found that the ramping speed of the structures with opening ports for HOM damping with magnetic coupling became slow and the resultant breakdown rate became high. It was also found that that with lower surface magnetic field showed faster ramping in processing and lower breakdown rate. This indicates the role of the magnetic field on vacuum breakdowns in copper structure at the region of several tens to 100 MV/m. In this paper, we review the processing stage and the high gradient performance of these structures trying to discuss the relevant parameters, surface electric field, surface magnetic field and other parameters such as Sc, “complex pointing vector”, to the performance difference.  
 
WEPFI031 Development of an X-Band Metallic Power Extractor for the Argonne Wakefield Accelerator impedance, extraction, simulation, cavity 2771
 
  • J. Shi, H.B. Chen, Q. Gao, X.W. Wu, Y. Yang, H. Zha
    TUB, Beijing, People's Republic of China
  • W. Gai, C.-J. Jing
    ANL, Argonne, USA
  
  An X-band (11.7GHz) power extractor has been developed for RF power generation at Argonne Wakefield Accelerator (AWA). The structure is a 2pi/3-mode disk-loaded structure with group velocity of 22% of the speed of light and a total length of about 300mm. It is build with copper disks brazed together. This note presents the design and the fabrication of this structure, as well as the RF measurement results.  
 
WEPFI032 New Calibration Method for Radial Line Experiment wakefield, collider, cavity, linear-collider 2774
 
  • X.W. Wu, H.B. Chen, J. Shi, H. Zha
    TUB, Beijing, People's Republic of China
  
  A radial line experiment is proposed to test the SiC load disks of the choke-mode structure. However, the general calibration cannot work out in this situation due to lack of matched load. A new calibration method named multi-offset short calibration is proposed. The principles of the method and the calibration steps involved are presented and the results of actual experimentation are used to validate the method. The results show multi-offset short calibration is a feasible method and that this method can provide a viable calibration scheme for radial line measurements.  
 
WEPFI033 Development of the HLS 40kW Solid State Amplifier rf-amplifier, power-supply, storage-ring, synchrotron 2777
 
  • L. Lin, G. Huang, C. Li, Y.T. Liu, W. Zhou
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  A 40kW RF Solid State Amplifier (SSA) will replace the 25kW tetrode amplifier as the new RF power generator of HLS 800MeV electron storage ring. This SSA contains sixty-five 650W amplifier units (one unit drives sixty-four’s), with two-stage combination to reach the 40kW output. All of the components of SSA are prepared and tested, each of them meets the design requirements. The SSA has been assembled, and is in off-line testing now. The process of SSA’s design and manufacture, and the test results are presented in this paper.  
 
WEPFI090 An X-band Dielectric-based Wakefield Power Extractor wakefield, simulation, vacuum, impedance 2908
 
  • C.-J. Jing, S.P. Antipov, A. Kanareykin, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • M.E. Conde, W. Gai, J.G. Power
    ANL, Argonne, USA
  • V.A. Dolgashev, J.R. Lewandowski, S.G. Tantawi, S.P. Weathersby
    SLAC, Menlo Park, California, USA
  • I. Syratchev
    CERN, Geneva, Switzerland
  
  Funding: US DoE SBIR Phase II project under Contract#DE-SC0004322
An X-band dielectric-based wakefield power extractor is under development to function as a high power rf source primarily for Two Beam Accelerator applications. A low surface electric field to gradient ratio and low fabrication cost are two main advantages of the dielectric-loaded accelerating/decelerating structure. We have designed a 12 GHz dielectric-based power extractor that has similar performance parameters to the CLIC PETS (23 mm beam channel, 240 ns pulse duration, 135 MW output per structure) using the CLIC drive beam. In order to study potential rf breakdown issues, as a first step we built a 11.424 GHz dielectric-based power extractor scaled from the 12 GHz design. A high power rf test will be conducted using the SLAC 11.424 GHz high power rf source in Dec. 2012. Results of the high power testing will be reported. Meanwhile, the 12 GHz fully featured dielectric power extractor is also under construction; construction progress and bench tests will be discussed. 		 
 
WEPME011 Beam Tests and Plans for the CERN PS Transverse Damper System emittance, injection, betatron, kicker 2947
 
  • A. Blas, S.S. Gilardoni, G. Sterbini
    CERN, Geneva, Switzerland
  
  The CERN Proton Synchrotron (CPS) has been running without any transverse damping equipment since 1998, thanks to the stabilizing effect of the linear coupling applied between horizontal and vertical planes. Lately, the demand for an active damper strongly emerged for two main reasons: to avoid restrictions as imposed on the betatron tune settings by the linear coupling and to cure instabilities appearing with high intensity beams, especially at the extraction energy. Late in 2012, two electronic prototype units, newly developed for the CPS one-turn-feedback, were programmed with a firmware designed to satisfy the transverse feedback (TFB) requirements in both planes. The main achievements were to automatically adapt the loop delay to the particles' time-of-flight variation within a nanosecond precision and to compensate the changing betatron phase advance between pick-up and kicker during the entire accelerating cycle. With the power equipment limited to the modest bandwidth of 23 MHz and 2 x 800 W per plane, encouraging results were obtained such as fast damping of injection oscillations caused by injection errors, reduction of beam losses along the cycle and damping of instabilities at all CPS energies.  
 
WEPME023 Study of the Vibration of the AC Dipole and Magnetic Measurement Girder for CSNS/RCS dipole, acceleration, resonance, synchrotron 2980
 
  • R.H. Liu, L. Kang, H. Qu, G.Y. Wang, H.J. Wang, J. S. Zhang
    IHEP, Beijing, People's Republic of China
  
  The dipole magnet of the China Spallation Neutron Source Rapid-cycling Synchrotron (RCS) will be operated at a 25Hz sinusoidal alternating current which causes severe vibration. The vibration will influence the long-term safety and reliable operation of the magnet. By taking the magnet and magnetic measurement girder as a specific model system, a method for analyzing and studying the dynamic characteristic of the system is put forward by combining theoretical calculation with experimental testing. And the ctive vibration of magnet is different with passive vibration which was causes by ground vibration, so a new isolator was designed to decrease the vibratory force and avoid the resonance phenomenon.  
 
WEPME043 Performance of the LHC Transverse Damper with Bunch Trains feedback, injection, kicker, pick-up 3022
 
  • W. Höfle, F. Dubouchet, G. Kotzian, D. Valuch
    CERN, Geneva, Switzerland
  
  In 2012 the LHC has operated for Physics with bunch trains at 50 ns spacing. Tests have been performed with the nominal design bunch spacing of 25 ns. The transverse damper has been an essential element to provide beam stability for the multi-bunch beam with up to 1380 bunches used at 50 ns spacing. We report on the experience gained with 50 ns spacing and the improvements in the signal processing tested for the future 25 ns operation. The increase in bandwidth required for 25 ns spacing constituted a particular challenge. The response of the system was carefully measured and the results used to digitally pre-distort the drive signal to compensate for a drop in gain of the power system for higher frequencies. The bunch-by-bunch data collected from the feedback signal path provided valuable information during the 2012 Physics run that can be further explored for beam diagnostics purposes and instability analysis in the future. Performance estimates are given for the 7 TeV run planned for 2015, at 25 ns bunch spacing.  
 
WEPME047 Identification of Sources of Orbital Distortions in Corrector Space quadrupole, alignment, feedback, controls 3034
 
  • M. Böge, M. Aiba, A. Saá Hernández, A. Streun
    PSI, Villigen PSI, Switzerland
  
  Since modern ring and linear accelerator based light sources feature fast orbit feedback (FOFB) systems which transform orbital oscillations in beam position monitor (BPM) space into corrector (C) space over a wide frequency range, most perturbations can be directly analyzed utilizing the C pattern. In C space the localization of sources of distortions is facilitated since the large (per unit phase) number of BPMs and Cs involved provides a good spatial resolution. Applications of this technique include the beam-assisted girder alignment where changes in the C pattern are interactively analyzed while girder positions are remotely altered or the beam-based alignment of quadrupole/BPM pairs where the variation of C values as the result of quadrupole variations are observed. In both cases large oscillations in BPM space are completely surpressed by the FOFB leading to well controlled and stable conditions during the measurement.  
 
WEPME060 First Results and Analysis of the Performance of a 4 GS/s Intra-bunch Vertical Feedback System at the SPS feedback, controls, kicker, injection 3070
 
  • J.M. Cesaratto, J.E. Dusatko, J.D. Fox, J.J. Olsen, K.M. Pollock, C.H. Rivetta, O. Turgut
    SLAC, Menlo Park, California, USA
  • H. Bartosik, W. Höfle, G. Kotzian, U. Wehrle
    CERN, Geneva, Switzerland
  
  Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research program ( LARP)
We present experimental measurements taken from SPS machine development studies with an intra-bunch feedback channel. These studies use a digital signal processing system to implement general-purpose control algorithms on multiple samples across a single SPS bunch ( for ease of synchronization with the SPS RF frequency a sampling frequency of 3.2 GS/sec. is implemented). These initial studies concentrate on single-bunch motion, and study the vertical betatron motion as the feedback control is varied. The studies are focused on validating simulation models of the beam dynamics with feedback. Time and frequency domain results include excitation and damping of intra-bunch motion with positive and negative feedback. We present an overview of the challenges of intra-bunch feedback, and highlight methods to time-align the pickup and kicker signals within the closed-loop feedback channel. 		 
 
THYB101 Suppressing Transverse Beam Halo with Nonlinear Magnetic Fields lattice, resonance, space-charge, octupole 3099
 
  • S.D. Webb, D.T. Abell, D.L. Bruhwiler, J.R. Cary
    Tech-X, Boulder, Colorado, USA
  • V.V. Danilov
    ORNL, Oak Ridge, Tennessee, USA
  • S. Nagaitsev, A. Valishev
    Fermilab, Batavia, USA
  
  Funding: This work was supported in part by the US Department of Energy's Office of Science, Office of High Energy Physics, under grant No. DE-SC0006247.
Traditional space charge driven resonances, such as beam halo, arise due to the underlying linear nature of accelerator lattices. In this talk, we present initial results on a new class of intrinsically nonlinear lattices, which introduce a large tune spread naturally. The resulting nonlinear decoherence suppresses the onset of beam halo. 		 
slides icon Slides THYB101 [63.510 MB]  
 
THPFI047 Design Guidelines for Ferrite Absorbers Submitted to RF-induced Heating radiation, HOM, pick-up, FEL 3394
 
  • A. Bertarelli, M. Garlaschè
    CERN, Geneva, Switzerland
  
  The use of ferrite absorbers is one of the most effective means of damping potentially harmful high order RF modes, which may lead to beam instabilities and excessive power losses in accelerator devices. However, the power deposited on ferrite absorbers themselves may lead to ferrite exceeding its Curie temperature, losing its damping properties. An evaluation of the ferrite capability to dissipate deposited heat is hence of paramount importance for the safe design of particle accelerator devices. In this paper, figures of merit are proposed to assess the maximum specific power allowed on a generic ferrite tile, before it reaches its Curie temperature. Due to its inherent brittleness, sufficient contact pressure between ferrite and its housing, allowing heat transmission by conduction, can hardly be applied. A semi-analytical study is thus performed, assuming that ferrite is evacuating heat solely through radiation. The described method is then exemplified in the case of the BPM-embedded tertiary collimator (TCTP) designed in the framework of the LHC collimation upgrade.  
 
THPFI090 Accuracy of Measurements of ε and μ of Lossy Materials HOM, simulation, higher-order-mode, insertion 3499
 
  • V.D. Shemelin, J.J. Kaufman
    CLASSE, Ithaca, New York, USA
  
  Funding: NSF award DMR-0807731
Measurements of samples of lossy ceramic and ferrites for Higher Order Mode Loads are performed routinely in our Lab. Some difference of results for different batches of materials can be explained not only by technological deviations in the material production but also by errors in the dimensions of the measured samples. Simulations with MicroWave Studio for samples in the form of coaxial washers in the frequency range from 1 to 12.4 GHz helped to define the main sources of errors and to improve accuracy of measurements. 		 
 
FRXCA01 Progress in Transverse Feedbacks and Related Diagnostics for Hadron Machines feedback, injection, kicker, hadron 3990
 
  • W. Höfle
    CERN, Geneva, Switzerland
  
  Today Hadron Accelerators with high intensity and high brightness beams increasingly rely on transverse feedback systems for the control of instabilities and the preservation of the transverse emittance. With particular emphasis, but not limited, to the CERN Hadron Accelerator Chain the progress made in recent years and the performances achieved are reviewed. Hadron colliders such as the LHC represent a particular challenge as they ask for low noise electronic systems in these feedbacks for acceptable emittance growth. Achievements of the LHC transverse feedback system used for damping injection oscillations and to provide stability throughout the cycle are summarized. This includes its use for abort gap and injection cleaning as well as transverse blow-up for diagnostics purposes. Beyond systems already in operation, advances in technology and modern digital signal processing with increasingly higher digitization rates have made systems conceivable to cure intra-bunch motion. With its capabilities to both acquire beam oscillations and to actively excite motion, transverse feedback systems have a large variety of applications for beam diagnostics purposes.  
slides icon Slides FRXCA01 [4.985 MB]