Keyword: impedance
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MOPC013 Design, Fabrication and High Power RF Test of a C-band Accelerating Structure for Feasibility Study of the SPARC Photo-injector Energy Upgrade accelerating-gradient, klystron, FEL, radiation 89
 
  • D. Alesini, R. Boni, G. Di Pirro, R. D. Di Raddo, M. Ferrario, A. Gallo, V.L. Lollo, F. Marcellini
    INFN/LNF, Frascati (Roma), Italy
  • G. Campogiani, A. Mostacci, L. Palumbo, S. Persichelli, V. Spizzo
    Rome University La Sapienza, Roma, Italy
  • T. Higo, K. Kakihara, S. Matsumoto
    KEK, Ibaraki, Japan
  • S. Verdú-Andrés
    TERA, Novara, Italy
 
  The energy upgrade of the SPARC photo-injector from 170 to 250 MeV will be done by replacing a low gradient 3m S-Band structure with two 1.5m high gradient C-band structures. The structures are traveling wave, constant impedance sections, have symmetric waveguide input couplers and have been optimized to work with a SLED RF input pulse. A prototype with a reduced number of cells has been fabricated and tested at high power in KEK (Japan) giving very good performances in terms of breakdown rates at high accelerating gradient (>50 MV/m). The paper illustrates the design criteria of the structures, the fabrication procedure and the high power RF test results.  
 
MOPC016 Development of a New RF Accelerating Cavity for J-PARC Ring Accelerator cavity, simulation, ion, controls 98
 
  • Y. Morita, T. Kageyama
    KEK, Ibaraki, Japan
  • J. Kameda
    ICRR, Chiba, Japan
  • S. Yamashita
    ICEPP, Tokyo, Japan
 
  Funding: Japan Society for the Promotion of Science (JSPS)
To enhance the beam power delivered by the J-PARC* ring accelerators, upgrading the accelerating cavities is indispensable. In particular, long term stable operation of the present cavities for the RCS** is one of the important issues. Currently, the cavities are loaded with FINEMET*** cores cooled by water, where every core is coated with glass cloth and epoxy resin for waterproof. However, it was reported that some of the cores were damaged by thermal stress. We are developing a new cavity loaded with multi ring core modules. Each core module consists of three ring cores concentrically arranged and sandwiched between two glass epoxy plates with flow channels grooved. The ring cores without waterproof coating are cooled by the turbulent flow of a chemically inert liquid (Fluorinert), since FINEMET is subject to corrosion in water. We have designed and built a high power prototype cavity loaded with a single core module, then carried out low level measurement and high power test. Finally, the cavity has been stably operated up to an average power loss of 10 kW per core module, which is 1.7 times higher than that for the present RCS cavity.
*Japan Proton Accelerator Research Complex
**Rapid-Cycling Synchrotron
***FINEMET is an iron-based magnetic alloy produced by Hitachi Metals, Ltd..
 
 
MOPC019 Condition of MA Cut Cores in the RF Cavities of J-PARC Main Ring after Several Years of Operation cavity, resonance, ion, synchrotron 107
 
  • M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura, Japan
  • E. Ezura, K. Hasegawa, K. Takata
    KEK, Tokai, Ibaraki, Japan
  • K. Hara, C. Ohmori, M. Toda, M. Yoshii
    KEK/JAEA, Ibaraki-Ken, Japan
  • T. Sato, M. Yamamoto
    JAEA, Ibaraki-ken, Japan
 
  J-PARC 3 GeV RCS and 50 GeV Synchrotron (MR) employ RF cavities loaded with Magnetic Alloy (MA) cores to generate a high field gradient. The RF cavities in RCS use MA un-cut cores. On the other hand, the RF cavities in MR employ MA cut cores to increase the Q-value from 0.6 to 26. We observed the impedance reductions of all MR RF cavities during several years operation. Opening the RF cavities, we found that the impedance reductions were resulting from corrosion on the cut and polished surfaces of MA cores. Before installation of the RF cavities, we had 1000 and 2000 hours long tests at a test stand. We didn't observe the impedance reduction related to the corrosion on the MA core cut surfaces at the test stand. The only difference between the test stand and MR is the quality of cooling water. The MR cooling water contains copper ions for example from copper hollow conductors of the main magnets. We report the influence of the copper ions to the corrosion on the MA core cut surface. We also show plans how to solve the issue of MA core cut surface corrosion.  
 
MOPC021 Design of a Choke-mode Damped Accelerating Structure for CLIC Main Linac damping, wakefield, HOM, dipole 113
 
  • J. Shi, A. Grudiev, W. Wuensch
    CERN, Geneva, Switzerland
  • H. Chen, W.-H. Huang, C.-X. Tang, H. Zha
    TUB, Beijing, People's Republic of China
 
  Choke-mode damped accelerating structures are being studied as an alternative to the CLIC baseline structure by a CERN-Tsinghua collaboration. Choke-mode structures hold the potential for much lower levels of pulsed surface heating and, since milling is not needed, reduced cost. Structures with radial choke attached are simulated in Gdfidl to investigate the damping of the transverse wake. The first pass-band of the dipole modes is well damped, while the higher order dipole modes are possible to be reflected by the choke. Therefore, the geometry of the choke is tuned to minimize the reflection of these higher order dipoles. Based on this damping scheme, an accelerating structure with the same iris dimensions as the nominal CLIC design but with choke-mode damping has been designed. A prototype structure will be manufactured and high power tested in the near future.  
 
MOPC023 Design of a C-band 6 MeV Standing-wave Linear Accelerating Structure coupling, electron, bunching, simulation 119
 
  • J.H. Shao, H. Chen, Q.Z. Xing
    TUB, Beijing, People's Republic of China
 
  We design a C-band standing-wave biperiodic on-axis coupled linear accelerating structure for industrial and medical applications. It’s less than 300mm long; consists of 3 bunching cells and 9 normal cells. It can accelerate electrons to 6MeV and the pulsed beam current is 100mA. The RF power source is a 2.5MW magnetron. We implement 2D cells geometry optimization by SUPERFISH, beam dynamics study by PARMELA and full scale 3D calculations by MAFIA codes.  
 
MOPC026 MA Cavity for HIRFL-CSR cavity, simulation, plasma, radio-frequency 125
 
  • L.R. Mei, Z. Xu, Y.J. Yuan, H.W. Zhao
    IMP, Lanzhou, People's Republic of China
 
  To meet the requirements of conducting high energy density physics and plasma physics research at HIRFL-CSR. The higher accelerating gap voltage was required. A magnetic alloy (MA)-core loaded radio frequency (RF) cavity which can provide higher accelerating gap voltage has been studied in Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS), Lanzhou. To select proper MA material to load the RF cavity, measurement for MA cores has been conducted. The MA core with higher shunt impedance and lower than 1 quality factor (Q value) should be selected. The theoretical calculation and simulation for the MA-core loaded RF cavity can be consistent with each other well. Finally 1000kW power was needed to meet 50-kV accelerating gap voltage by calculation.  
 
MOPC030 The C-band Traveling-wave Accelerating Structure for Compact XFEL at SINAP* linac, vacuum, controls, status 133
 
  • W. Fang, Q. Gu, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  • D.C. Tong
    TUB, Beijing, People's Republic of China
 
  The R&D of C-band accelerating structure has been launched two years ago at Shanghai Institute of Applied Physics, it will be used for the future compact hard X-ray FEL. The 1st C-band traveling-wave accelerating structure is ready for the high power test now. This structure is the preliminary model for the research of the technology of microwave test and tuning, arts and crafts and high power test. This paper presents the process of fabrication, cold test and tuning results.  
 
MOPC039 Optimization of IH-DTL Resonator for UNDULAC-RF acceleration, focusing, ion, undulator 160
 
  • S.M. Polozov, A.S. Plastun, P.R. Safikanov
    MEPhI, Moscow, Russia
 
  The linear undulator accelerator (UNDULAC) was proposed early for ribbon ion beam acceleration*. UNDULAC can be realized using two non-synchronous spatial harmonics. One of them must be RF field harmonic and the second can be RF (UNDULAC-RF) or electrostatic (UNDULAC-E). The acceleration mechanism in UNDULAC is similar as inverse free electron laser (IFEL). The beam dynamics in both types of UNDULAC was studied early and the design of UNDUAC-RF resonator was started in **. Design of the 150 MHz IH-DTL for UNDULAC-RF will present. The optimization of the longitudinal field distributions will do. The most effective construction will show. Transverse electric field distributions within drift tube will optimize by blending support stems and drift tubes.
* E.S. Masunov, Sov. Phys. – Tech. Phys. 35(8), 962-965, 1990.
** S. M. Polozov, P. R. Safikanov, Proc. IPAC’10, Kyoto, Japan, p. 3762 (2010).
 
 
MOPC040 The Measurement of Transversal Shunt Impedance of RF Deflector cavity, simulation, dipole, emittance 163
 
  • A.Yu. Smirnov, M.V. Lalayan, N.P. Sobenin
    MEPhI, Moscow, Russia
  • A.A. Zavadtsev
    Nano, Moscow, Russia
 
  This paper presents the results of transverse shunt impedance measurement performed using field perturbation technique and comparison with numerical MWS simulations. The structure under test is the S-band 3-cell deflecting cavity. The mentioned cavity operates with a dipole TM11-like mode with a phase shift of 120 deg per cell. The analyses were carried out with use of two types of perturbing beads: dielectric beads and metallic rings. The latter type perturbs the on-axis magnetic field much stronger than the electric field, which allows us calculating transversal shunt impedance using on-axis EM fields values.  
 
MOPC047 RF Design of the Re-buncher Cavities for the LIPAC Deuteron Accelerator cavity, vacuum, linac, beam-transport 184
 
  • A. Lara, I. Podadera, F. Toral
    CIEMAT, Madrid, Spain
 
  Funding: Work partially supported by Spanish Ministry of Science and Innovation under project ENE2009-11230.
Re-buncher cavities are an essential component of LIPAC (Linear IFMIF Prototype Accelerator), presently being built at Rokkasho (Japan). The deuteron beam exiting from the RFQ (Radio Frequency Quadrupole) structure has to be properly adapted to the superconducting RF (SRF) linac. Re-bunchers are placed in the Medium Energy Beam Transport (MEBT) line and their objective is to longitudinally focus the deuteron beam. IFMIF re-bunchers must provide a 350 kV E0LT at 175 MHz continuous wave (CW). The available length for the re-buncher is limited by the general layout of the MEBT. The high power dissipation derived from the high effective voltage and the short available length is an important design challenge. Four different normal conducting cavity designs were investigated: the pillbox type, double gap coaxial resonators, and multi-gap quarter wave and H resonators. The performance of these cavities was studied with the numerical codes HFSS and ANSYS. The fundamental frequency and field pattern of each re-buncher was investigated in HFSS. This work presents the results of such analyses.
 
 
MOPC051 The 100 MHz RF System for the MAX IV Storage Rings cavity, LLRF, storage-ring, HOM 193
 
  • Å. Andersson, E. Elafifi, M. Eriksson, D. Kumbaro, P. Lilja, L. Malmgren, R. Nilsson, H. Svensson, P.F. Tavares
    MAX-lab, Lund, Sweden
  • J.H. Hottenbacher
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
  • A. Milan
    CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
  • A. Salom
    ELETTRA, Basovizza, Italy
 
  The construction of the MAX IV facility has started and user operation is scheduled to commence 2015. The facility is comprised of two storage rings optimized for different wavelength ranges, and a linac-based short pulse facility. In this paper the RF systems for the two storage rings are described. The RF systems will be based on either tetrode or solid state amplifiers working at 100 MHz. Circulators will be used to give isolation between cavity and power amplifier. The main cavities are of normal conducting, entire copper, capacity loaded type, where the present cavities at MAX-lab has served as prototypes. For the MAX IV ring operation it is essential to elongate bunches, in order to minimize the influence of intra beam scattering on beam transverse emittances. For this, 3rd harmonic passive (Landau-) cavities are employed. These are of similar type as the main cavities, mainly because the capacity loaded type has the advantage of pushing higher order modes to relatively high frequencies compared to pill-box cavities. Digital low level RF systems will be used, bearing in mind the possibility of post mortem analysis.  
 
MOPC057 Loss of Landau Damping in the LHC emittance, damping, injection, acceleration 211
 
  • E.N. Shaposhnikova, T. Argyropoulos, P. Baudrenghien, T. Bohl, A.C. Butterworth, J. Esteban Muller, T. Mastoridis, G. Papotti, J. Tückmantel, W. Venturini Delsolaro, U. Wehrle
    CERN, Geneva, Switzerland
  • C.M. Bhat
    Fermilab, Batavia, USA
 
  Loss of Landau damping leading to a single bunch longitudinal quadrupole instability has been observed in the LHC during the ramp and on the 3.5 TeV flat top for small injected longitudinal emittances. The first measurements are in good agreement with the threshold calculated for the expected longitudinal reactive impedance budget of the LHC as well as with the threshold dependence on beam energy. The cure is a controlled longitudinal emittance blow-up during the ramp which for constant threshold through the cycle should provide an emittance proportional to the square root of energy.  
 
MOPC058 Upgrade of the 200 MHz RF System in the CERN SPS cavity, emittance, extraction, acceleration 214
 
  • E.N. Shaposhnikova, E. Ciapala, E. Montesinos
    CERN, Geneva, Switzerland
 
  The 200 MHz RF system, used in the SPS to accelerate all beams including those for the LHC, has four travelling wave structure cavities of different length. To stabilize the future higher intensity LHC beams in the SPS a larger (than now) controlled longitudinal emittance blow-up and therefore larger bucket and voltage amplitude will be necessary. However less voltage will be available in the existing system (which has a maximum peak RF power of 1 MW per cavity) due to the increased beam loading, in particular in the long cavities. This issue will be critical for beam acceleration but especially for beam transfer into the 400 MHz RF system of the LHC. The proposed solution is to shorten the two long cavities and use the freed sections together with spare sections to make two extra cavities and install two new power plants of 1.3 MW each. After this upgrade, which is a major part of the more general SPS upgrade for high luminosity LHC to be completed during 2017, the performance of the SPS RF system with high intensity beams will be significantly improved and at the same time the total impedance of the system will be reduced.  
 
MOPC059 The Plane Wave Transformer Linac Development at NSRRC linac, simulation, cavity, electron 217
 
  • A. Sadeghipanah, J.-Y. Hwang, W.K. Lau
    NSRRC, Hsinchu, Taiwan
  • T.H. Chang
    NTHU, Hsinchu, Taiwan
 
  A Plane-Wave-Transformer (PWT), standing wave linac operating at S-band frequency (2.9979 GHz) is being developed at NSRRC. This structure offers the advantages of high efficiency, compactness, fabrication simplicity and cost. The PWT prototype at NSRRC consists of three cells with two half-cells at the ends, separated by a set of four flat disks suspended and cooled by four water tubes inside a large cylindrical tank. To fully understand its physical properties, numerical modeling of the PWT prototype has been carried out by using the 2-D code SUPERFISH and 3-D code MAFIA. In this paper, we describe the principle properties of this structure, the electric parameters obtained from numerical simulations, and heat dissipation calculation. The mechanical design for prototype linac is also reported.  
 
MOPC064 Upgrade and Commissioning of the 88-Inch Cyclotron Final Power Amplifier cyclotron, resonance, ion, cathode 229
 
  • M. Kireeff Covo, D.F. Byford, P.W. Casey, A. Hodgkinson, S. Kwiatkowski, C.M. Lyneis, L. Phair, A. Ratti, C.P. Reiter
    LBNL, Berkeley, California, USA
 
  Funding: This work was supported by the Director, Office of Science, Office of High Energy and Nuclear Physics, Division of Nuclear Physics, U.S. Department of Energy under Contract DE-AC02-05CH11231.
The RF system of the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory is a resonant system based on the quarter-wave cantilever type resonating structure. Power is fed to the Dee from the anode of the 500 kW RCA 6949 tetrode tube operating in grounded cathode configuration, which is capacitively coupled to the side of the Dee stem. The tube is obsolete and makes its continued use impractical. A new final power amplifier was designed and built using the commercially available tube Eimac 4W150,000E. The new amplifier was successfully commissioned and has been reliable and easy to operate. An overview of the system upgrade and details of the commissioning will be presented.
 
 
MOPC078 Operation of Superconducting Cavities in a Fast Ramping Electron Storage Ring cavity, HOM, acceleration, storage-ring 253
 
  • A. Roth, W. Hillert
    ELSA, Bonn, Germany
 
  Funding: Supported by German Research Foundation through SFB/TR 16.
The achievable maximum energy of a medium-sized electron accelerator is mainly limited by the accelerating voltage. Using superconducting (sc) cavities, the energy limitation can be shifted considerably. However, the operation of sc multi-cell cavities in a fast ramping storage ring causes additional problems which were investigated at the 3.5 GeV Electron Stretcher Accelerator ELSA. We studied the use of two 500 MHz sc cavities providing the necessary resonator voltage of up to 14 MV and replacing the normal conducting cavities of PETRA type. A large cavity coupling factor is required, so that using the existing 250 kW klystron, an internal beam of 50 mA can be accelerated up to 5 GeV. In addition, a fast detuning of the resonance frequency of the cavities must be implemented during beam injection and the energy ramp of 4 GeV/s. An appropriate 500 MHz structure is given by a five-cell cavity constructed for the JAERI-FEL-LINAC. Based on this geometry, HOM have been calculated from a numerical simulation. Since all monopole and a larger number of dipole HOM are well above the multibunch instabilities threshold, further studies about beam instabilities damping are essential.
 
 
MOPC080 First Considerations Concerning an Optimized Cavity Design for the Main Linac of BERLinPro cavity, HOM, linac, coupling 259
 
  • B. Riemann, T. Weis
    DELTA, Dortmund, Germany
  • W. Anders, J. Knobloch, A. Neumann
    HZB, Berlin, Germany
  • H.-W. Glock, C. Potratz, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • F. Marhauser
    JLAB, Newport News, Virginia, USA
 
  Funding: work supported by BMBF under contracts 05K10PEA and 05K10HRC
The Berlin Energy Recovery Linac Project (BERLinPro) is designed to develop and demonstrate CW linac technology and expertise required to drive next-generation Energy Recovery Linacs. Strongly HOM-damped multicell 1.3 GHz cavities are required for the main linac. The optimization of the cavities presented here is primarily based on the CEBAF 1.5 GHz 5-cell high-current cavity design, including HOM waveguide couplers. The cavity was scaled to 1.3 GHz and extended to 7 cells. Modifications to the end group design have also been studied. An effort was also made to reduce the ratio Epk/Eacc while still permitting HOMs to propagate.
 
 
MOPC121 Design of Low-frequency Superconducting Spoke Cavities for High-velocity Applications cavity, HOM, superconductivity, linac 364
 
  • J.R. Delayen, C.S. Hopper
    ODU, Norfolk, Virginia, USA
  • R.G. Olave
    Old Dominion University, Norfolk, Virginia, USA
 
  Superconducting single- and multi-spoke cavities have been designed to-date for particle velocities from β~0.15 to β~0.65. Superconducting spoke cavities may also be of interest for higher-velocity, low-frequency applications, either for hadrons or electrons. We present the design of 325 and 352 MHz spoke cavities optimized for β=0.8 and β=1.  
 
MOPC129 Compact Solid State RF-Modules for Direct Drive RF-linacs linac, vacuum, cavity, klystron 382
 
  • R. Irsigler, M. Back, R. Baumgartner, O. Heid, T.J.S. Hughes, M. Kaspar, T. Kluge, J. Sirtl, K. Weidner, M. Zerb
    Siemens AG, Erlangen, Germany
 
  We present a modular RF power source concept based on solid state RF-modules with novel SiC transistors. The concept offers lower cost, better reliability and reduced maintenance compared to traditional RF-source technology. No circulators are required, which makes the RF-module very compact and reliable. The SiC power transistor has a very low input capacitance and was optimized for low gate resistance to enable fast switching in the VHF range. It delivers a maximum pulsed drain saturation current of 65 A. The transistor provides at 350 V supply voltage and 150 MHz an output power of 5,6 kW at a gain of 15,8 dB. It is essential to avoid high parasitic source inductances at RF and good thermal conductivity is required for operation at high duty cycle. We have built very compact 75 x 90 mm ceramic amplifier modules using a planar interconnect technology (SIPLIT) to connect the bare die transistors to the DCB substrate. The modules have a fully symmetric push-pull topology (circlotron) with four transistors in parallel in each leg. The RF-modules delivered at 150 MHz an impressive RF output power in the range of 40 kW. Further tests at 324 MHz are planned and will be presented.  
 
MOPC143 A Reduced Gradient Output Design for SLAC's XL4 X-Band Klystron simulation, klystron, cavity, beam-loading 412
 
  • A. Jensen, C. Adolphsen, A.E. Candel, M.V. Fazio, E.N. Jongewaard, D.W. Sprehn, A.E. Vlieks, F. Wang
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported by the U.S. Department of Energy under contract DE-AC03-76SF00515.
X-band klystron work began at SLAC in the mid to late 1980's to develop high frequency (4 times the SLAC S-band klystron), high power RF sources for the linear collider designs under consideration at that time. This work culminated in the current workhorse X-band RF source, the XL4. To date 26 XL4 tubes have been built. The XL4 4-cell disk loaded traveling wave output structure has a high operating gradient. A new 6-cell structure has been designed to reduce breakdown and to further improve the klystron's robustness. Initial simulations show the 6-cell design reduces the gradient roughly 25% and that the structure is stable. A physical XL4 will be retrofitted with the new output cavity and hot tested in the near future.
 
 
MOPO003 A Broadband RF Stripline Kicker for Damping Transversal Multibunch Instabilities kicker, feedback, single-bunch, damping 481
 
  • M. Schedler, D. Heiliger, W. Hillert, A. Roth
    ELSA, Bonn, Germany
 
  When operating an RF feedback system, being able to reliably act upon every single bunch is a necessity. By employing a broadband RF stripline kicker, any bunch displacement can be corrected for. In a 500 MHz accelerator, the decay time of the electromagnetic field inside the kicker has to be less than 2 ns in order to avoid the following bunch to be affected. By designing the kicker as an RF coax device matched to the line impedance of the power cables, perturbing reflected signals are avoided. Additionally, the kicking strength and thus the shunt impedance should be maximized over the full spectrum from DC to 250 MHz. The kicker design has been optimized to meet the above requirements by relying on CST Microwave Studio simulations. Their results and first measurements are presented.  
 
MOPO004 A Longitudinal Kicker Cavity for a Bunch-by-bunch Feedback System at ELSA cavity, kicker, simulation, feedback 484
 
  • N. Heurich, W. Hillert, A. Roth, R. Zimmermann
    ELSA, Bonn, Germany
 
  At the Electron Stretcher Facility ELSA of Bonn University, a longitudinal bunch-by-bunch feedback system is currently being installed in order to damp multibunch instabilities and to enable a future intensity upgrade of up to 200 mA. As a main component, a longitudinal kicker cavity was developed and manufactured. The kicker requires a bandwidth of 250~MHz taking into account the bunch spacing of 2 ns at ELSA. Existing designs used at other facilities were optimized in view of the considerably larger bunch lenght at ELSA. The choice of 1.125 GHz as a center frequency is a result of these considerations. With the resulting low quality factor, the design had to be optimized in order to maximize the shunt impedance. The longitudinal feedback is succesfully working with the prototype installed in the stretcher ring. The design and detailed simulations of the geometry are discussed and laboratory measurements are presented.  
 
MOPO007 Resonant Strip-line Type Longitudinal Kicker kicker, simulation, feedback, wakefield 493
 
  • T. Nakamura
    JASRI/SPring-8, Hyogo-ken, Japan
 
  The longitudinal feedback for the SPring-8 storage ring is under consideration as the device for suppression of the longitudinal instabilities driven by higher order modes of cavities, observed at test operation with 4 to 6 GeV low energy beam. As the beam energy and the ring circumference are rather high, and the length of the space for the longitudinal kickers is limited, high efficiency kicker per length is required in the our case. As a candidate of such kicker, we propose a resonant strip-line type longitudinal kicker with drive frequency of 13/4 of RF frequency. The shut impedance per length is higher than over-loaded cavities and the drive circuits can be simplified because of higher drive frequency. The design consideration, the result of the simulation and measurement of the prototype model, and the detail of the drive circuit will be reported in the presentation.  
 
MOPO008 Design and Simulation of the Transverse Feedback Kicker for the HLSⅡ kicker, feedback, simulation, vacuum 496
 
  • W.B. Li, P. Lu, B.G. Sun, F.F. Wu, Y.L. Yang, Z.R. Zhou
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  In order to suppress the coupled bunch instabilities in the HLSⅡ storage ring, a transverse feedback system is required. The vital component of the system is the kicker that is the feedback actuator. We design a stripline kicker for the HLSⅡ. The horizontal and vertical electrodes are combined in a structure on account of the space limit. In addition to the design issues, this paper focuses on the simulation results for the kicker using the computer codes. By the 2D code POSSION, we calculate and optimize the characteristic impedance of the stripline kicker to match the 50Ω external transmission lines so as to reduce the reflected power. The reflection coefficient and the shunt impedance in the working frequency range are obtained by the 3D code HFSS. The simulation results provide many important supports for the structure design.  
 
MOPS004 Mitigation of Beam Instability due to Space Charge Effects at 3 GeV RCS in J-PARC space-charge, kicker, bunching, injection 595
 
  • Y. Shobuda, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • Y.H. Chin
    KEK, Ibaraki, Japan
  • F. Tamura
    KEK/JAEA, Ibaraki-Ken, Japan
 
  In order to accomplish high intensity proton beams, it is important to identify the impedance source in accelerators. At 3 GeV rapid cycling synchrotron (RCS) in Japan Proton Research Complex (J-PARC), the kicker impedance is the most dominant among such impedance sources. Beam instability can be observed by correcting chromaticity during the acceleration. Growth rate due to the beam instability can be reduced by making peak current larger (bunching factor smaller). In other words, it is experimentally found that space charge effects mitigate the beam instability.  
 
MOPS006 Beam Tilt due to Transverse Wakefields for DAΦNE, SuperB, KEKB and SuperKEKB closed-orbit, wakefield, collider, vacuum 601
 
  • D.M. Zhou, K. Ohmi
    KEK, Ibaraki, Japan
  • A. Chao
    SLAC, Menlo Park, California, USA
 
  When a beam bunch traverses a transverse impedance, the bunch head generates a transverse wakefield that kicks the bunch tail, generating a betatron motion of the tail relative to the head. In a storage ring, in a steady state, this kick to the bunch tail produces a transverse closed orbit (e.g. in the y-direction) of the bunch tail relative to the bunch head, which means the beam now has a y-z tilt. Such beam tilt due to transverse wakefields may cause a loss of luminosity in storage ring colliders or loss of brightness in light sources. In this paper, we present a preliminary study of the beam tilt effect for the colliders DAΦNE, SuperB, KEKB and SuperKEKB.  
 
MOPS007 Interference of CSR Fields in a Curved Waveguide positron, damping, storage-ring, wakefield 604
 
  • D.M. Zhou, K. Ohmi
    KEK, Ibaraki, Japan
 
  CSR fields generated by a bunched beam passing through a series of bending magnets may interfere with each other due the reflections of outer chamber wall. This kind of multi-bend interference causes sharp peaks and long-range tail in the CSR impedance and wake potentials, respectively. Using a dedicated computer code, CSRZ, we calculated the longitudinal CSR impedance in the SuperKEKB positron damping ring for purpose of demonstration. It was found that multi-bend interference may enhance the CSR fields within a distance comparable to the bunch length, which is typically in the order of several millimeters. A simple instability analysis was performed and it suggested that multi-bend interference might play a role in the single-bunch instabilities of small electron/positron rings.  
 
MOPS013 Transverse Low Frequency Broad-band Impedance Measurements in the CERN PS proton, space-charge, extraction, injection 622
 
  • S. Aumon
    EPFL, Lausanne, Switzerland
  • P. Freyermuth, S.S. Gilardoni, O. Hans, E. Métral, G. Rumolo
    CERN, Geneva, Switzerland
 
  The base-line scenario for the High-Luminosity LHC upgrade foresees an intensity increase delivered by the injectors. With its 53 years, the CERN PS would have to operate beyond the limit of its performances to match the future requirements. Beam instabilities driven by transverse impedance are an important issue for the operation of high intensity beams as for the high-brightness LHC beams. Measurements of transverse tune dependence with beam intensity were performed at injection kinetic energy 1.4~GeV and at LHC beam extraction momentum 26~GeV/c. This allows deducing the low frequency inductive broad-band impedance of the machine. Then an estimation of the real part of the impedance is made by the rise time measurement of a fast transverse instability believed to be a TMCI type. Those are the first step towards a global machine impedance characterization in order to push forward the performances of the accelerator.  
 
MOPS045 Coupling Impedance of Rough Resistive Pipe* coupling, resonance, vacuum, wakefield 700
 
  • M. Ivanyan, V.M. Tsakanov
    CANDLE, Yerevan, Armenia
 
  A new version of modelling of the surface roughness impact by thin dielectric layer in the round resistive beam pipe is suggested. The calculation method of coupled resistive-roughness impedance is developed.  
 
MOPS046 Impedances and Wakes in Round Three-layer Ceramic Waveguide acceleration, radiation, damping, accumulation 703
 
  • M. Ivanyan, A.V. Tsakanian
    CANDLE, Yerevan, Armenia
 
  The round ceramic waveguide with inner and outer thin metal coating is considered. Using the exact methods the longitudinal impedances and potentials are calculated. Identification of the main patterns of changes in their properties by varying the electrodynamic and geometric parameters of the waveguide is performed as well. The possibility of optimizing the parameters of the waveguide for the effective implementation of two-beam acceleration is discussed.  
 
MOPS052 Analytical and Numerical Calculations of Beam Pipe Impedances at Low Frequencies with Application to Thin SIS100 Pipe coupling, synchrotron, shielding, betatron 721
 
  • U. Niedermayer, O. Boine-Frankenheim, L. Hänichen
    TEMF, TU Darmstadt, Darmstadt, Germany
 
  The projected fast ramped synchrotron SIS100 for FAIR uses an elliptical stainless steel beam pipe of 0.3 mm thickness. The lowest coherent betatron sidebands reach down to 100 kHz which demands accurate impedance calculations in the low frequency (LF) regime. For these frequencies, i.e. skin depth greater than wall thickness, structures behind the pipe may contribute to the impedance. Due to the extremely large wake length numerical methods in the time domain are not applicable. The longitudinal and transverse impedance of the thin SIS100 beam pipe including structures behind the pipe are obtained numerically by a method using power loss in the frequency domain. We compare different analytical models for simplified pipe structures to the numerical results. The dc and ultra-relativistic limits are investigated. The interpretation of bench measurements in the LF regime is discussed.  
 
MOPS054 Impedance of the Pulse Power Converter for the SIS100 Bipolar Extraction Kicker System kicker, coupling, simulation, extraction 727
 
  • K. Samuelsson, V. Hinrichsen
    TU Darmstadt, Darmstadt, Germany
  • U. Blell, P.J. Spiller
    GSI, Darmstadt, Germany
 
  SIS100 will be operated with high intensity heavy-ion and proton beams. The reduction of ring impedances is therefore of great importance in order to avoid coherent beam instabilities. The kicker system is one of the main contributors to the overall ring impedance in SIS100. This paper will focus on the contribution of the external network to the kicker impedance. Calculations as well as experimental impedance measurements of the network contribution have already been carried out for the SIS18 and ESR kickers. The SIS100 will be equipped with a bipolar kicker system, which uses a Pulse Forming Network (PFN) as energy storage. For potential detachment purposes an insulation transformer will be installed. Since this setup is new in several ways it is important to know its contribution to the coupling impedance of the kicker system. In this contribution the corresponding numerical calculation is presented.  
 
MOPS055 Observation of Intensity Dependent Single Bunch Effects at the Synchrotron Light Source PETRA III emittance, synchrotron, single-bunch, electron 730
 
  • R. Wanzenberg, K. Balewski
    DESY, Hamburg, Germany
 
  At DESY the PETRA ring is operated as a synchrotron radiation facility with a very low emittance of 1 nm. Regular user operation has started in summer 2010. A summary of observations and measurements of intensity dependent single bunch effects is presented in this report. The longitudinal impedance of the ring is estimated from the measured bunch length versus beam intensity. The results are compared with predictions from the impedance model. Furthermore measurements of the single bunch intensity limit due to the transverse mode coupling instability (TMCI) are reported. The tune and phase shift around the ring has been measured as a function of the beam intensity. At PETRA III tune spectra have been observed with some characteristics which have been observed at other storage rings in connection with electron cloud effects. The present status of the observations of potential electron cloud effects is also discussed.  
 
MOPS059 Transverse Impedance Calculation for Simplified Model of Ferrite Kicker Magnet with Beta < 1 kicker, coupling, extraction, proton 742
 
  • N. Wang, Q. Qin
    IHEP Beijing, Beijing, People's Republic of China
 
  In high intensity rings, kicker magnet is usually considered as a main source to the total impedance. Transverse coupling impedance of a simplified kicker model has been derived analytically in the ultrarelativistic limit. We extend the result to the general case of v < c, and present the analytical formulae of both horizontal and vertical transverse impedances. Numerical results are given for the CSNS extraction kicker magnets.  
 
MOPS060 Study on Resistive Wall Instability in CSNS/RCS simulation, injection, wakefield, extraction 745
 
  • L. Huang, Y.D. Liu, S. Wang
    IHEP Beijing, Bejing, People's Republic of China
 
  Rapid Cycling Synchrotron of the China Spallation Neutron Source is a high intensity proton accelerator, with average beam power of 100kW. The collective effects caused by the coupling impedance may be the limit to beam power. The impedance estimation for components on beam line shows that the resistive wall impedance and its instability are more serious than any others. Based on the impedance budget, the instability is theoretically estimated. And a simple resistive wall wake field model is used to simulate the bunch oscillation and the growth rate instability. In this model, the continuous resistive wall wake field is equivalent to a point wake field and long bunch is sliced into many micro-bunches. By tracking the dynamics of the macro-bunches, the transverse growth rate are obtained and the result are analyzed.  
 
MOPS064 Longitudinal Beam Stability and Related Effects at the ALBA Storage Ring kicker, resonance, vacuum, injection 748
 
  • T.F. Günzel
    CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
 
  The risk of longitudinal instabilities excited by narrowband and broadband resonator impedance was studied. A campaign for the search of modes trapped in vacuum chamber elements of the ALBA storage ring via electromagnetic simulation was initiated. Several critical vacuum elements in the ring like the vertical scraper, the injection and feedback kickers were identified. The outlets of the injection kicker had to be protected with RF-fingers whereas the scraper only produces dangerous modes in the withdrawn state, both do not pose a real problem. However, the calculated power distribution generated in the feedback kickers could be an obstacle for reaching the nominal current of 400mA. Furthermore, the budget of Z(n)/n of the storage ring was computed and checked on the risk of microwave instability using the Boussard criterion.  
 
MOPS065 Transverse Instability Studies at the ALBA Storage Ring vacuum, single-bunch, kicker, storage-ring 751
 
  • T.F. Günzel
    CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
 
  In the first phase of the ALBA storage ring operation 3 NEG-coated aluminum chambers, 2 in-vacuum undulators and one wiggler chamber will be installed. Under particular consideration of the multilayer character of these chambers and the injection kickers the thresholds of the transverse mode coupled instability(TMCI) were calculated using MOSES*. The thresholds 17.5mA/40.5mA vertical/horizontal leave a rather large operative margin. The detrimental effect of the NEG-coating on the TMCI is relatively limited and on the resistive wall instability is even negligible. As well the thresholds of the head-tail instability were computed as function of chromaticity. Also the incoherent tune shifts generated by the quadrupolar resistive wall wake fields due to the flatness of the vacuum chambers were calculated. The computed results have been compared to first measurements of the storage ring commissioning.
* Y.H.Chin, MOSES 2.0, CERN/LEP-TH/88-05
 
 
MOPS066 Collective Effects in the MAX IV 3 GeV Ring cavity, damping, storage-ring, synchrotron 754
 
  • P.F. Tavares
    MAX-lab, Lund, Sweden
  • T.F. Günzel
    CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
  • R. Nagaoka
    SOLEIL, Gif-sur-Yvette, France
 
  We present calculations of collective instability effects in the 3 GeV electron storage ring of the MAX IV facility currently under construction in Lund, Sweden. The storage ring is designed to deliver ultra-low emittance down to 0.24 nm rad so as to provide high brightness synchrotron radiation from undulators. This is achieved in a comparatively small machine (528 m circumference) through the use of a multi-bend achromat lattice and a compact magnet design featuring multi-purpose narrow gap magnet blocks. This design features small dispersion leading to low momentum compaction, which, together with the small circular (11 mm radius) chambers, poses a challenge to reach the design current (500 mA in 176 bunches) without exciting instabilities and degrading beam parameters due to the interaction with the machine impedance. Particularly important are multi-bunch resistive wall effects in the NEG coated copper chamber as well single-bunch instabilities driven by the broad-band impedance. A low RF frequency (100 MHz) and harmonic cavities are foreseen to lengthen the bunches and increase instability thresholds.  
 
MOPS068 Localization of Transverse Impedance Sources in the SPS using HEADTAIL Macroparticle Simulations quadrupole, lattice, simulation, ion 757
 
  • N. Biancacci, G. Arduini, E. Métral, D. Quatraro, G. Rumolo, B. Salvant, R. Tomás
    CERN, Geneva, Switzerland
  • N. Biancacci, M. Migliorati, L. Palumbo
    Rome University La Sapienza, Roma, Italy
  • R. Calaga
    BNL, Upton, Long Island, New York, USA
 
  In particle accelerators, beam coupling impedance is one of the main contributors to instability phenomena that lead to particle losses and beam quality deterioration. For this reason these machines are continuously monitored and the global and local amount of impedance needs to be evaluated. In this work we present our studies on the local transverse impedance detection algorithm. The main assumptions behind the algorithm are described in order to understand limits in reconstructing the impedance location. The phase advance response matrix is analyzed in particular for the SPS lattice, studying the different response from 90,180,270 degrees phase advance sections. The thin lenses scheme is also implemented and new analytical formulas for phase advance beating were derived. This avails us to put reconstructing lenses everywhere in the lattice, and to study their positioning scheme. Limits in linear response are analyzed. This sets the upper and lower limits in reconstruction to the phase advance measurement accuracy and the linear response regime limit.  
 
MOPS070 Electromagnetic Modeling of C Shape Ferrite Loaded Kickers kicker, simulation, vacuum, ion 763
 
  • C. Zannini
    EPFL, Lausanne, Switzerland
  • E. Métral, G. Rumolo, B. Salvant, V.G. Vaccaro, C. Zannini
    CERN, Geneva, Switzerland
 
  The kickers are major contributors to the CERN SPS beam coupling impedance. As such, they may represent a limitation to increasing the SPS bunch current in the frame of an intensity upgrade of the LHC. In this paper, analytical approach and CST Particle Studio time domain electromagnetic simulations are performed to obtain the longitudinal and transverse impedances/wake potentials of models of ferrite loaded kickers. It turns out that the existing models are not sufficient to characterize correctly these components from the coupling impedance point of view. In particular the results show that below few hundred MHz the real C-structure of the magnet cannot be neglected. Therefore an analytical model was developed and benchmarked with EM simulations to take into account the C-shape of the magnet.  
 
MOPS071 Simulations of the Impedance of the New PS Wire Scanner Tank simulation, beam-losses, extraction, vacuum 766
 
  • B. Salvant
    EPFL, Lausanne, Switzerland
  • W. Andreazza, F. Caspers, A. Grudiev, J.F. Herranz Alvarez, E. Métral, G. Rumolo
    CERN, Geneva, Switzerland
 
  The CERN PS is equipped with 4 wire scanners. It was identified that the small aperture of the current wire scanner tank causes beam losses and a new tank design was needed. The interaction of the PS bunches with the beam coupling impedance of this new tank may lead to beam degradation and wire damage. This contribution presents impedance studies of the current PS tank as well as the new design in order to assess the need to modify the design and/or install lossy materials plates dedicated to damp higher order cavity modes and reduce the total power deposited by the beam in the tank.  
 
MOPS072 Broadband Electromagnetic Characterization of Materials for Accelerator Components simulation, kicker, damping, RF-structure 769
 
  • C. Zannini, A. Grudiev, E. Métral, T. Pieloni, G. Rumolo
    CERN, Geneva, Switzerland
  • G. De Michele
    PSI, Villigen, Switzerland
  • C. Zannini
    EPFL, Lausanne, Switzerland
 
  Electromagnetic (EM) characterization of materials up to high frequencies is a major requirement for the correct modeling of many accelerator components: collimators, kickers, high order modes damping devices for accelerating cavities. In this scenario, the coaxial line method has gained much importance compared to other methods because of its applicability in a wide range of frequencies. In this paper we describe a new coaxial line method that allows using only one measurement setup to characterize the material in a range of frequency from few MHz up to several GHz. A coaxial cable fed at one side is filled with the material under test and closed on a known load on the other side. The properties of the material are obtained from the measured reflection coefficient by using it as input for a transmission line (TL) model or for 3D EM simulations, which describe the measurements setup. We have applied this method to characterize samples of SiC (Silicon Carbide) which could be used for LHC collimators and for CLIC accelerating structures and NiZn ferrite used for kicker magnets.  
 
MOPS073 Impedance Calculation for Simple Models of Kickers in the Non-ultrarelativistic Regime kicker, vacuum, coupling, neutron 772
 
  • N. Biancacci, N. Mounet, E. Métral, B. Salvant, C. Zannini
    CERN, Geneva, Switzerland
  • N. Biancacci, M. Migliorati, A. Mostacci, L. Palumbo
    Rome University La Sapienza, Roma, Italy
  • Q. Qin, N. Wang
    IHEP Beijing, Beijing, People's Republic of China
 
  Kicker magnets are usually significant contributors to the beam coupling impedance of particle accelerators. An accurate understanding of their impedance is required in order to correctly assess the machine intensity limitations. The field matching method derived by H. Tsutsui for the longitudinal and transverse dipolar (driving) impedance of simple models of kickers in the ultrarelativistic regime was already extended to the non-ultrarelativistic case, and to the quadrupolar (detuning) impedance in the ultrarelativistic case. This contribution presents the extension to the quadrupolar impedance in the non-ultrarelativistic case, as well as benchmarks with other available methods to compute the impedance. In particular, all the components of the impedances are benchmarked with Tsutsui's model, i.e. in the ultrarelativistic limit, with the model for a flat chamber impedance recently computed by N. Mounet and E. Métral, in the case of finite relativistic gamma, and with CST Particle Studio simulations.  
 
MOPS075 Simulation of Multibunch Motion with the HEADTAIL Code and Application to the CERN SPS and LHC wakefield, simulation, synchrotron, coupling 778
 
  • N. Mounet
    EPFL, Lausanne, Switzerland
  • N. Mounet, E. Métral, G. Rumolo
    CERN, Geneva, Switzerland
 
  Multibunch instabilities due to beam-coupling impedance can be a critical limitation for synchrotrons operating with many bunches. It is particularly true for the LHC under nominal conditions, where according to theoretical predictions the 2808 bunches rely entirely on the performance of the transverse feedback system to remain stable. To study these instabilities, the HEADTAIL code has been extended to simulate the motion of many bunches under the action of wake fields. All the features already present in the single-bunch version of the code, such as synchrotron motion, chromaticity, amplitude detuning due to octupoles and the ability to load any kind of wake fields through tables, have remained available. This new code has been then parallelized in order to track thousands of bunches in a reasonable amount of time. The code was benchmarked against theory and exhibited a good agreement. We also show results for bunch trains in the LHC and compare them with beam-based measurements.  
 
MOPS076 Long Range Wakefields in the SwissFEL C-band Linac wakefield, HOM, linac, simulation 781
 
  • A. Citterio, M. Aiba, R. Zennaro
    PSI, Villigen, Switzerland
 
  The SwissFEL main linac consists of more than hundred constant gradient C-band accelerating structures which boost the beam energy from 410 MeV at the injector to the final nominal energy of 5.8 GeV. With a repetition rate of 100 Hz, two bunches per pulse can be accelerated with a spacing of 28 ns to feed simultaneously two different FEL arms*. Rising of the long range wakefields, both longitudinal and transverse, could affect this multibunch operation, causing degenerative effects on the quality of the second bunch. A direct computation of the longitudinal and transverse wakes by means of time domain simulations is compared with a model based on the computation of the dispersion curves of the wake modes by frequency domain simulations. A good agreement is obtained for both the synchronous frequency and impedance of all the main modes contributing to the wakefields. Moreover, the total longitudinal wake at 28 ns is below the thighter tolerances required by the beam dynamics, so that neither Higher Order Modes (HOMs) either beam loading require compensation. The effects on the beam of the long range transverse wakefields are also negligeable.
*R. Ganter et al, SwissFEL CDR, PSI report n. 10-04; http://www.psi.ch/swissfel/CurrentSwissFELPublicationsEN/SwissFELCDR_v1903.03.11-small.pdf
 
 
MOPS078 Coaxial Wire Measurements of Ferrite Kicker Magnets kicker, simulation, injection, extraction 784
 
  • H.A. Day, R.M. Jones
    UMAN, Manchester, United Kingdom
  • M.J. Barnes, F. Caspers, H.A. Day, E. Métral, B. Salvant, C. Zannini
    CERN, Geneva, Switzerland
 
  Fast kicker magnets are used to inject beam into and eject beam out of the CERN accelerator rings. These kickers are generally transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the yoke can provoke significant beam induced heating, especially for high intensities. In addition the impedance may contribute to beam instabilities. The results of longitudinal and transverse impedance measurements, for various kicker magnets, are presented and compared with analytical calculations: in addition predictions from a numerical analysis are discussed.  
 
MOPS079 Simulations of Coaxial Wire Measurements of the Impedance of Asymmetric Structures simulation, coupling, kicker, synchrotron 787
 
  • H.A. Day, R.M. Jones
    UMAN, Manchester, United Kingdom
  • F. Caspers, H.A. Day, E. Métral
    CERN, Geneva, Switzerland
 
  Coaxial wire measurements have provided a simple and effective way to measure the beam coupling impedance of accelerator structures for a number of years. It has been known how to measure the longitudinal and dipolar transverse impedance using one and two wires for some time. Recently the ability to measure the quadrupolar impedance of structures exhibiting top/bottom and left/right symmetry has been demonstrated. A method for measuring the beam coupling impedance of asymmetric structures using displaced single wires and two wire measurements is proposed. Simulations of the measurement system are presented with further work proposed.  
 
MOPS080 Comparison of the Current LHC Collimators and the SLAC Phase 2 Collimator Impedances coupling, simulation, cavity, collimation 790
 
  • H.A. Day, R.M. Jones
    UMAN, Manchester, United Kingdom
  • F. Caspers, H.A. Day, E. Métral, B. Salvant
    CERN, Geneva, Switzerland
 
  One of the key sources of transverse impedance in the LHC has been the secondary graphite collimators that sit close to the beam at all energies. This limits the stable bunch intensity due to transverse coupled-bunch instabilities and transverse mode coupling instability. To counteract this, new secondary collimators have been proposed for the phase II upgrade of the LHC collimation system. A number of designs based on different jaw materials and mechanical designs have been proposed. A comparison of the beam coupling impedance of these different designs derived from simulations are presented, with reference to the existing phase I secondary collimator design.  
 
TUODB01 Progress of the Construction for the TPS Vacuum System vacuum, photon, ion, storage-ring 976
 
  • G.-Y. Hsiung, C.K. Chan, C.H. Chang, C.-C. Chang, C.L. Chen, C.M. Cheng, Y.T. Cheng, S-N. Hsu, H.P. Hsueh, I.T. Huang, T.Y. Lee, I.C. Sheng, L.H. Wu, H.Y. Yan, Y.C. Yang, C.S. huang
    NSRRC, Hsinchu, Taiwan
  • J.-R. Chen
    National Tsing Hua University, Hsinchu, Taiwan
 
  Vacuum system for the 3 GeV Taiwan Photon Source (TPS) has been started the construction since 2010. The critical components such as the bellows and gate valves with rf-contact shielding, pulsed magnet kicker ceramic chambers, BPM, crotch absorbers, etc. have been manufactured and tested. Aluminum alloy (Al-) vacuum chambers for the arc-cells have been machined and undergoing the in-house welding. Mass production of the vacuum equipments including the ion gauges, ion pumps, NEG pumps, and gate valves, has been contracted out and partially delivering following the schedule of the cell assembling. Each cell, contains two short Al-straight chambers and two Al-bending chambers, has been started the assembling and on-site welding on the pre-aligned girders in clean room forming an one-piece vacuum vessel about 14 m in length following by the vacuum baking to the ultra-high vacuum. The conceptual design of the vacuum systems for the long straight sections, the concentric booster, and the transport lines, will be addressed. The progress of prototyping development and the status of construction for the TPS vacuum system will be described in this paper.  
slides icon Slides TUODB01 [35.595 MB]  
 
TUPC007 Kicker and Monitor for CTF3 Phase Feed Forward kicker, pick-up, coupling, collider 1000
 
  • F. Marcellini, D. Alesini, A. Ghigo
    INFN/LNF, Frascati (Roma), Italy
 
  Funding: Work partially supported by the EuCARD research programme, Grant Agreement 227579, within the 'Assessment of Novel Accelerator Concepts'.
In the Compact LInear Collider (CLIC) the synchronization of the Drive Beam and the Main Beam has to be assured in the femtosecond range to avoid luminosity reduction of the collider. The Drive and Main Beams arrival time is measured with longitudinal monitors and the correction is applied changing the path length of one beam respect to the other in a magnetic chicane by means of two transverse fast stripline kicker. The performance of the feed forward system will be tested in the CLIC Test Facility (CTF3) measuring the phase at the linac exit, correcting in the chicane after the combination rings and comparing the longitudinal position change before the power RF production system. The developed phase monitors and kicker magnets for the test in CTF3 are described.
 
 
TUPC011 Striplines for CLIC Pre-Damping and Damping Rings* kicker, vacuum, damping, extraction 1012
 
  • C. Belver-Aguilar, A. Faus-Golfe
    IFIC, Valencia, Spain
  • M.J. Barnes, G. Rumolo
    CERN, Geneva, Switzerland
  • F. Toral
    CIEMAT, Madrid, Spain
  • C. Zannini
    EPFL, Lausanne, Switzerland
 
  The Compact Linear Collider (CLIC) study explores the scheme for an electron-positron collider with high luminosity and a nominal center-of-mass energy of 3 TeV: CLIC would complement LHC physics in the multi-TeV range. 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 fulfil the luminosity requirements. The specifications for the kicker systems are very challenging and include very low beam coupling impedance and excellent field homogeneity: striplines have been chosen for the kicker elements. Analytical calculations have been carried out to determine the effect of tapering upon the high frequency beam coupling impedance. In addition detailed numerical modeling of the field homogeneity has been performed and the sensitivity of the homogeneity to various parameters, including stripline cross-section, has been studied. This paper presents the main conclusions of the beam impedance calculations and field homogeneity predictions.  
 
TUPC015 Comparative Wakefield Analysis of a First Prototype of a DDS Structure for CLIC Main Linac wakefield, simulation, dipole, damping 1024
 
  • A. D'Elia, A. Grudiev, V.F. Khan, W. Wuensch
    CERN, Geneva, Switzerland
  • R.M. Jones
    UMAN, Manchester, United Kingdom
 
  A Damped Detuned Structure (DDS) for CLIC main linac has been proposed as an alternative to the present baseline design which is based on heavy damping. A first prototype, CLICDDSA, for high power tests has been already designed and is under construction. It is also foreseen to design a further prototype, CLICDDSB, to test both the wakefield suppression and high power performances. Wakefield calculations for DDS are, in the early design stage, based on single infinitely periodic cells. Though cell-to-cell interaction is taken into account to calculate the wakefields, it is important to study full structure properties using computational tools. In particular this is fundamental for defining the input parameters for the HOM coupler that is crucial for the performances of DDS. In the following a full analysis of wakefields and impedances based on simulations conducted with finite difference based electromagnetic computer code GdfidL will be presented.  
 
TUPC050 Impedance Effects in the CLIC Damping Rings wiggler, damping, simulation, vacuum 1111
 
  • E. Koukovini, K.S.B. Li, N. Mounet, G. Rumolo, B. Salvant
    CERN, Geneva, Switzerland
 
  Due to the unprecedented brilliance of the beams, the performance of the Compact Linear Collider (CLIC) damping rings is affected by collective effects. Single bunch instability thresholds based on a broad-band resonator model and the associated coherent tune shifts have been evaluated with the HEADTAIL code. Simulations performed for positive and negative values of chromaticity proved that higher order bunch modes can be potentially dangerous for the beam stability. This study also includes the effects of high frequency resistive wall impedance due to different coatings applied on the chambers of the wigglers for e-cloud mitigation and/or ultra-low vacuum pressure. The impact of the resistive-wall wake fields on the transverse impedance budget is finally discussed.  
 
TUPC080 Pickup Design with Beta Matching pick-up, simulation, resonance, kicker 1189
 
  • J.A. Tsemo Kamga, W.F.O. Müller, K.K. Stavrakakis, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
 
  Funding: Work supported by GSI
The main goal of this project is to investigate the Schottky noise of an ion beam in the frequency range from 3 to 5 GHz. In order to accomplish this task, a pickup design is required. For an efficient study of this Schottky noise the pickup sensitivity for low beta must be increased. A design for such a problem has been developed by McGinnis for a fixed beam velocity but can also be used for variable beta by using a tunable material (ferroelectric) inside the waveguide. Since such tunable materials like for instance BST (Barium Strontium Titanate) are lossy, the impact of dielectric losses on the pickup sensitivity will also be investigated in this work. Additionally to the classical parameter studies where multiple simulation runs based on the original numerical model are initiated to characterize the various design parameters it is also possible to utilize a reduced model instead. In particular one is interested in a fast evaluation of the frequency response while taking also material variations into account. In this work, a multivariate parameterized dynamical system is set up and used complementary to the full model for the required beam characterization.
 
 
TUPS026 Specification of New Vacuum Chambers for the LHC Experimental Interactions vacuum, alignment, injection, optics 1584
 
  • R. Veness, R.W. Assmann, A. Ball, A. Behrens, C. Bracco, G. Bregliozzi, R. Bruce, H. Burkhardt, G. Corti, M.A. Gallilee, M. Giovannozzi, B. Goddard, D. Mergelkuhl, E. Métral, M. Nessi, W. Riegler, J. Wenninger
    CERN, Geneva, Switzerland
  • N. Mounet, B. Salvant
    EPFL, Lausanne, Switzerland
 
  The apertures for the vacuum chambers at the interaction points inside the LHC experiments are key both to the safe operation of the LHC machine and to obtaining the best physics performance from the experiments. Following the successful startup of the LHC physics programme the ALICE, ATLAS and CMS experiments have launched projects to improve physics performance by adding detector layers closer to the beam. To achieve this they have requested smaller aperture vacuum chambers to be installed. The first periods of LHC operation have yielded much information both on the performance of the LHC and the stability and alignment of the experiments. In this paper, the new information relating to the aperture of these chambers is presented and a summary is made of analysis of parameters required to safely reduce the vacuum chambers apertures for the high-luminosity experiments ATLAS and CMS.  
 
TUPS029 Development of a Feedthrough with Small Reflection for the TPS BPM synchrotron, controls, vacuum 1593
 
  • Huang, Y.T. Huang, C.-C. Chang, C.L. Chen, G.-Y. Hsiung, S-N. Hsu, H.P. Hsueh
    NSRRC, Hsinchu, Taiwan
  • J.-R. Chen
    National Tsing Hua University, Hsinchu, Taiwan
 
  The TPS BPM feedthrough is a coaxial cable with a structure of a kind for which power loss occurs readily at places at which exists an impedance mismatch. With an impedance equation for a simple coaxial cable combined with a multi-dielectric modification, a model feedthrough with small reflection has been designed. With careful setting of brazing conditions and precise control of the dimensions of devices, a TPS prototypical BPM feedthrough having a reflection coefficient less than 0.05 was manufactured. The eccentricity was constrained within 0.03 mm, and the deviation of measured capacitance of button electrodes was less than 7 %.  
 
TUPS036 High Energy Beam Impacts on Beam Intercepting Devices: Advanced Numerical Methods and Experimental Set-up simulation, emittance 1614
 
  • A. Bertarelli, V. Boccone, F. Carra, F. Cerutti, A. Dallocchio, N. Mariani, M.A. Timmins
    CERN, Geneva, Switzerland
  • L. Peroni, M. Scapin
    Politecnico di Torino, Torino, Italy
 
  Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program.
Beam Intercepting Devices are potentially exposed to severe accidental events triggered by direct impacts of energetic particle beams. State-of-the-art numerical methods are required to simulate the behavior of affected components. A review of the different dynamic response regimes is presented, along with an indication of the most suited tools to treat each of them. The consequences on LHC Tungsten Collimators of a number of beam abort scenarios were extensively studied, resorting to a novel category of numerical explicit methods, named Hydrocodes. Full shower simulations were performed providing the energy deposition distribution. Structural dynamics and shock wave propagation analyses were carried out with varying beam parameters, identifying important thresholds for collimator operation, ranging from onset of permanent damage up to catastrophic failure. Since the main limitation of these tools lies in the limited information available on constitutive material models under extreme conditions, a dedicated experimental program is proposed, relying on the HiRadMat test facility at CERN. Experimental aspects such as sample-holder design and test set-up are described.
 
 
TUPS040 Driving the LHC Collimators' Stepping Motors over 1 km with High Accuracy avoiding EMI Effects controls, feedback, beam-losses, radiation 1626
 
  • A. Masi, G. Conte, R. Losito, M. Martino
    CERN, Geneva, Switzerland
 
  The LHC collimators are exposed to very high levels of radiation, which means that the power drivers must be installed far from the stepping motors that they drive. Due to the geometry of the underground installations, the distances can be up to 1 km. The long cables that connect the drivers to the motors behave as transmission lines modifying dramatically the impedance seen by the drivers and consequently jeopardizing the control performance of Pulse Width Modulation (PWM) drivers. In this paper we address this problem, provide an analytical model of the driver-cable-motor system and describe the analog solution we have developed to improve the performance of a typical off the shelf driver. Finally we characterize the improvement of the performances with measurements of positioning repeatability and show that electromagnetic emissions from the long cables are drastically reduced, making the use of stepping motors compatible with extremely sensitive instrumentation such as the LHC Beam Loss Monitors (BLM).  
 
TUPS062 The Ground Testing of TPS Ground System site, synchrotron, storage-ring, background 1677
 
  • T.-S. Ueng, J.-C. Chang, C.K. Kuan, Y.-C. Lin
    NSRRC, Hsinchu, Taiwan
 
  A ground grid of 4 rings and 62 vertical electrodes has been constructed for the TPS storage ring. The ground resistance was designed to be smaller than 0.2 ohms in order to give a good protection of the TPS electrical facility and personnel. In order to match the building construction schedule the TPS ground grid has been installed about 1/6 segment of the construction project each period. The ground impedance of each segment was measured right after the installation. The ground grid with the diameter of 200 m of outside ring and its low impedance value, also the limit testing space, challenged the measurement of ground resistance. Several different methods of ground testing have been used and the measured results are compared each other. These methods include fall-of-potential method, slope method, intersecting curves method and the test-current-reversal method. The final TPS ground impedance will be measured and compared with the calculation from combining the previous several segment measurements. The actual TPS ground resistance should have a smaller value than expected.  
 
TUPS075 Experimental determination of impedance and delay time of the 100 Ω meander transmission line for the SPIRAL2 Single Bunch Selector ion, simulation, single-bunch, site 1710
 
  • M. Di Giacomo
    GANIL, Caen, France
  • P. Balleyguier
    CEA/DAM/DPTA/SP2A, Bruyères-le-Châtel, France
  • A.C. Caruso, F. Consoli
    INFN/LNS, Catania, Italy
  • A. Longhitano
    ALTEK, San Gregorio (CATANIA), Italy
 
  The Spiral2 driver requires a Single Bunch Selector to reduce the bunch repetition rate at the experimental targets. A 100 Ω meander line is used in the beta 0.04 medium energy line of the Spiral2 driver. The non standard characteristic impedance figure helps to reduce the pulsed power but introduces the problem of calibrated measurements. The paper describes the results of the different methods used to measure the impedance and the delay of the electrodes.  
 
TUPS092 Research of Thermal Deformation on a Compact Cyclotron CYCHU-10 cavity, cyclotron, vacuum, radio-frequency 1753
 
  • K.F. Liu
    HUST, Wuhan, People's Republic of China
 
  Nowadays, a cyclotron CYCHU-10 used for PET is under construction in Huazhong University of Science and Technology (HUST) due to the growing demands in medical applications. For space-saving and low energy consumption, the CYCHU-10 was designed compactly and accurately, especially for the RF cavity consists of the valley of the magnetic pole and the dee electrodes installed on the vacuum chamber. The RF system will supply a 10kw power and large part of it will transform into thermal energy. This paper will introduce the thermal deformation of the RF cavity and the main vacuum chamber. Meanwhile the finite elements analysis thermal deformation with ANSYS Products will be present. Finally, the cooling system for the RF cavity will be carefully designed due to the result of thermo analysis and the mechanical tolerance demand in the RF system. Keywords- thermal deformation; mechanical tolerance; FEA;RF power.  
 
TUPS101 A Fast 650V Chopper Driver controls, linac, status, kicker 1777
 
  • M.M. Paoluzzi
    CERN, Geneva, Switzerland
 
  In the framework of Linac4 and the Superconducting Proton Linac (SPL) studies at CERN, the design for a beam chopper has been carried out. The chopper is basically a kicker that deviates part of the beam towards a dump. It is made of two 50 Ω, slow wave lines facing each other, matching the beam velocity and driven with a minimum of 500 V. Due to the bunch spacing of 2.84 ns, a system rise and fall time (3 %-90 %) below 2.5 ns is required with pulse lengths ranging from 8 ns to hundreds of μs. Although different solutions for the driver amplifier where devised in the past, none of the achievements was entirely satisfactory. This paper describes a new design and prototype that meets all the required specifications.  
 
TUPS103 High Temperature Radio Frequency Loads simulation, coupling, vacuum, instrumentation 1783
 
  • S. Federmann, F. Caspers, A. Grudiev, E. Montesinos, I. Syratchev
    CERN, Geneva, Switzerland
 
  In the context of energy saving and recovery requirements the design of reliable and robust RF power loads which permit a high outlet temperature and high pressure of the cooling water is desirable. Cooling water arriving at the outlet with 150 deg C and more than 20 bar has a certain value. Normal RF power loads containing dielectric and sensitive windows usually do not permit going much higher than 50 deg C. Here we present and discuss several design concepts for narrow-band “metal only” RF high power loads. One concept is the application of normal steel corrugated waveguides structures near cutoff .This concept could find practical use above several GHz. Another solution are resonant structures made of normal magnetic steel to be installed in large waveguides for frequencies of 500 MHz or lower. Similar resonant structures above 100 MHz taking advantage the rather high losses of normal steel may also be used in coaxial line geometries with large dimensions.  
 
WEPC093 Various Approaches to Electromagnetic Field Simulations for RF Cavities simulation, cavity, HOM, higher-order-mode 2226
 
  • C. Liu, W. Ackermann, W.F.O. Müller, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
 
  Funding: Work supported by BMBF under contract 05H09RD5
In the Superconducting Proton Linac (SPL) cavity, there is not only the fundamental mode for the particle acceleration but also many higher order modes (HOMs), which can lead to particle beam instabilities. This is very dangerous for SPL cavity. Therefore it is necessary to simulate the electromagnetic field in the SPL cavity, so that the field distribution and the shunt impedance for every higher order mode can be precisely calculated. At TEMF this research work can be done in three different ways: field simulation with hexahedron mesh in frequency domain, field simulation with hexahedron mesh in time domain and field simulation with tetrahedral mesh and higher order curvilinear elements. Finally the HOM coupler will be considered for the effective damping of higher order modes in the SPL cavity.
 
 
WEPC095 Simulations of the Microbunching Instability at ANKA using a Vlasov-Fokker-Planck Solver radiation, electron, synchrotron, simulation 2232
 
  • M. Klein, A.-S. Müller
    KIT, Karlsruhe, Germany
  • K.G. Sonnad
    CLASSE, Ithaca, New York, USA
 
  In order to produce coherent synchrotron radiation the ANKA light source is operated frequently in short bunch mode. It is known that during this procedure strong self fields caused by high electron densities can enforce initial density fluctuations and thus lead to microbunching. The build-up of those substructures is accompanied by bursting radiation which provides higher radiation power for the users. Damping and diffusion due to incoherent radiation smoothens the bunch shape again and hence lead to periodic or chaotic bursting cycles. The evolution of the electron bunch density under the influence of self fields can be described by the Vlasov-Fokker-Plank (VFP) equation. We present results from a numerical solution of the VFP-equation for parameters used in standard short bunch mode at ANKA.  
 
WEPC108 CSR Impedance for an Ultrarelativistic Beam moving in a Curved Trajectory shielding, vacuum, resonance, radiation 2268
 
  • D.M. Zhou, K. Ohmi, K. Oide
    KEK, Ibaraki, Japan
 
  A dedicated computer code, CSRZ, has been developed to calculate the coherent synchrotron radiation (CSR) impedance for an ultrarelativistic beam moving in a curved trajectory. Following the pioneering work of T. Agoh and K. Yokoya*, the code solves the parabolic equation in the frequency domain in a curvilinear coordinate system. The beam is assumed to move along a vacuum chamber which has a uniform rectangular cross section but with variable bending radius. Using this code, we did investigations in calculating the longitudinal CSR impedance of a single and a series of bending magnets. The calculation results indicate that the shielding effect due to outer chamber wall can be well explained by a simple optical approximation model at high frequencies. The CSR fields reflected by the outer wall may interfere with each other in a long bending magnet and lead to sharp narrow peaks in the CSR impedance.
* T. Agoh and K. Yokoya, Phys. Rev. ST Accel. Beams, 7(5):054403 (2004).
 
 
WEPC123 Numerical Algorithm based on the PDE Method for the Solution of the Fokker-Planck Equation simulation, pick-up, kicker, storage-ring 2298
 
  • M. Dolinska
    NASU/INR, Kiev, Ukraine
  • C. Dimopoulou, A. Dolinskii, F. Nolden, M. Steck
    GSI, Darmstadt, Germany
 
  Funding: Work supported by HIC for FAIR
This paper discus a fast and accurate algorithm for numerical solution of Fokker-Planck equation based on the solution of the parabolic Partial Differential Equations (PDE), where the Crank–Nicholson scheme is used. The stability, convergence and round-off errors of the algorithm are studied. The numerical results on Fokker–Planck equation solution with PDE method are compared with other numerical methods. Using the PDE solver, we will be able to predict the stochastic cooling process of notch filter in storage rings.
 
 
WEPC144 Beam Monitor Deformation by Tohoku Earthquake and its Recovery Project cavity, vacuum, linac, DTL 2328
 
  • A. Miura, K. Hasegawa, H. Oguri, N. Ouchi
    JAEA/J-PARC, Tokai-mura, Japan
  • Z. Igarashi, M. Ikegami, T. Miyao
    KEK, Ibaraki, Japan
 
  On March 11, 2011, the biggest earthquake occurred at Tohoku and North Kanto area in Japan. This earthquake and related ones have attacked J-PARC accelerators and caused the big damage. As for the linac beam monitors, some commissioning tools which were installed in the linac had damage and the air leakage was observed. In the first step of the recovery work, we checked the damage and put the emergency treatment for vacuum of the cavities. All beam monitors were observed, the leak from the vacuum devices was tested and the conduction of the signal cables was measured to compare the previous performance. In the next step, we started to order the new devices which should be replaced and to obtain the calibration data. We found the leakage from the phase monitors. The earthquake caused the crack and deformation at the welded points between the metallic parts and ceramic parts. And a wire of the profile monitor was broken while the beam position monitors have no damage. We are continuing this recovery work ongoingly.  
 
WEPS002 Limitations in Mitigating Collective Effects in the Beta-Beam Decay Ring by the Use of Octupoles octupole, ion, damping, injection 2481
 
  • C. Hansen
    CERN, Geneva, Switzerland
  • E. Benedetto
    National Technical University of Athens, Zografou, Greece
  • A. Chancé, J. Payet
    CEA/DSM/IRFU, France
 
  Funding: I acknowledge the financial support of the European Community under the European Commission Framework Programme 7 Design Study: EUROnu, Project Number 212372.
The beta-beam concept relies on the production, by beta decay of radioactive ions of a very high flux, of an electron neutrino and anti-neutrino beam towards a distant detector. After production and acceleration in an accelerator complex consisting of a rapid cycling synchrotron, the CERN PS and the CERN SPS, the radioactive isotopes are injected into a long racetrack-shaped ring, called the decay ring, where they orbit until they decay or are lost. The required intensities to store in the decay ring to reach the aimed neutrino fluxes are very high. Among the collective effects, the head tail effect, caused by transversal resonance impedance, is one of the main issues: the beam was shown to be unstable with the previous decay ring lattice. The lattice was changed to handle this problem; e.g. octupoles were included to increase the stability limit with an amplitude detuning. We here report on the improvement on the beta-beam performance with respect to amplitude detuning in the decay ring and discuss other mitigation attempts.
 
 
WEPS006 CNAO RF System: Hardware Description. cavity, proton, resonance, controls 2493
 
  • L. Falbo, G. Burato
    CNAO Foundation, Milan, Italy
  • M.M. Paoluzzi, G. Primadei
    CERN, Geneva, Switzerland
 
  CNAO is the Italian National Center of Oncological Hadrontherapy in Pavia. Proton beams are accelerated in the synchrotron and extracted in the energy range 60 to 250 MeV/u and carbon ion beams in the energy range 120 to 400 MeV/u. Trapping at the injection energy of 7 MeV/u and acceleration up to the extraction energy are done by an RF cavity which covers the needed wide range of frequency (0.4 to 3 MHz) and voltage (25 V to 5 kV) thanks to the use of a Vitrovac amorphous alloy. RF Gymnastics, including phase jumps to increase the momentum spread and empty bucket channelling, is requested and has been performed. A description of the hardware characteristics of the CNAO RF system and of its performance in terms of dynamic and static behaviour are reported in this paper.  
 
WEPS010 Acceleration of High Intensity Proton Beams in the J-PARC Synchrotrons cavity, injection, acceleration, synchrotron 2502
 
  • M. Yoshii
    KEK/JAEA, Ibaraki-Ken, Japan
  • E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, K. Takata, M. Toda
    KEK, Ibaraki, Japan
  • T. Minamikawa
    University of Fukui, Fukui, Japan
  • M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura, Japan
 
  The J-PARC accelerator complex consists of the linac, the 3GeV rapid cycling synchrotron (RCS) and the 50GeV main synchrotron (MR). These synchrotrons are the first MW-class proton accelerators which employ the high electric field gradient magnetic alloy (MA) loaded RF cavities. The beam commissioning was started in October 2007 for RCS and in May 2008 for MR. High intensity beam operation studies and user runs have been performed, while carefully controlling and minimizing the beam loss. The cycle to cycle beam operation is reproducible and quite stable, because of the stable linac beam energy and the reproducible bending field in both synchrotrons. The MA loaded RF systems and the full digital LLRF also guarantee the stable longitudinal particle motion and precise beam transfer synchronization from RCS to the MLF user facility as well as to the MR. A high intensity proton beam of 2.5·1013 ppp is accelerated in RCS. And in MR, a beam intensity up to ~100 Tera ppp was obtained. We summarize the RF systems and the longitudinal parameters in both rings.  
 
WEPS025 First Beam Experiments at ISIS with a Low Output-impedance Second Harmonic Cavity cavity, simulation, proton, synchrotron 2538
 
  • Y. Irie, S. Fukumoto, K. Muto, H. Nakanishi, T. Oki, A. Takagi
    KEK, Ibaraki, Japan
  • D. Bayley, I.S.K. Gardner, R.J. Mathieson, A. Seville, J.W.G. Thomason
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • J.C. Dooling, D. Horan, R. Kustom
    ANL, Argonne, USA
  • M.E. Middendorf
    ORNL RAD, Oak Ridge, Tennessee, USA
 
  A Low Output-Impedance (LOI) rf drive, which may be suitable for future high intensity accelerator applications, has been developed jointly by ANL, ISIS and KEK for an ISIS synchrotron second harmonic cavity. The cavity is ferrite-loaded, and is driven by a high-power triode (240 kW plate dissipation) with a plate-to-grid feedback circuit. The impedance is designed to be 20~30 ohms over a 2-6 MHz frequency range. Beam induced voltage has been measured with the ISIS beam, and compared with that calculated from the designed output impedance.  
 
WEPS034 A CW RFQ Prototype rfq, simulation, linac, vacuum 2559
 
  • U. Bartz, A. Schempp
    IAP, Frankfurt am Main, Germany
 
  A short RFQ prototype was built for RF-tests of high power RFQ structures. We will study thermal effects and determine critical points of the design. HF-simulations with CST Microwave Studio and measurements were done. The cw-tests with 20 kW/m RF-power and simulations of thermal effects with ALGOR were finished successfully. The optimization of some details of the HF design is on focus now. First results and the status of the project will be presented.  
 
WEPS075 Induction Sector Cyclotron for Cluster Ions acceleration, induction, ion, cyclotron 2679
 
  • K. Takayama
    KEK, Ibaraki, Japan
  • T. Adachi
    Sokendai, Ibaraki, Japan
  • W. Jiang
    Nagaoka University of Technology, Nagaoka, Niigata, Japan
  • H. Tsutsui
    SHI, Tokyo, Japan
 
  A novel scheme of a sector cyclotron to accelerate extremely heavy cluster ions, called Induction Sector Cyclotron (ISC)*, is described. Its key feature is fast induction acceleration. An ion bunch is accelerated and captured with pulse voltages generated by transformers**. The acceleration and confinement in the longitudinal direction can be independently handled. Since the transformers are energized by the switching power supply, in which turning on/off of the switching gate is maneuvered by gate signals digitally manipulated from the circulating beam signal of an ion bunch, acceleration synchronizing with the revolution of ion beam is always guaranteed. A cluster ion beam such as C-60, which so far there has been no way to repeatedly accelerate, can be accelerated from extremely low energy to high energy. The fundamental concept of ISC is introduced and beam dynamical issues such as a life time of cluster ions under strong guide fields and repeatedly exerted pulse voltages in the existence of residual molecules are addressed. In addition, the present status of R&D works on a race track-shape induction accelerating cell will be presented.
* K.Takayama et al., submitted for publication (2011).
** K.Takayama and R.J.Briggs, Chapter 11 and 12 in Induction Accelerators (Springer, 2010).
 
 
WEPS096 Injection Energy Recovery of J-PARC RCS power-supply, injection, beam-losses, septum 2730
 
  • N. Hayashi, H. Hotchi, J. Kamiya, P.K. Saha, T. Takayanagi, K. Yamamoto, M. Yamamoto, Y. Yamazaki
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
 
  The J-PARC RCS is a high beam power Rapid-Cycling Synchrotron (RCS). The original designed injection energy is 400MeV, although presently it is 181MeV, and its beam power is limited to 0.6MW. Works to recover the Linac energy are ongoing and injection magnets power supplies upgrade are required in the RCS. In order to achieve 1MW designed beam power, new instrumentation is also planned simultaneously. Activities related injection energy recovery in the J-PARC RCS is presented.  
 
WEPS097 Performance of Multi-harmonic RF Feedforward System for Beam Loading Compensation in the J-PARC RCS cavity, beam-loading, acceleration, beam-losses 2733
 
  • F. Tamura, M. Nomura, A. Schnase, T. Shimada, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • K. Hara, C. Ohmori, M. Toda, M. Yoshii
    KEK/JAEA, Ibaraki-Ken, Japan
  • K. Hasegawa
    KEK, Tokai, Ibaraki, Japan
 
  The beam loading compensation is a key part for acceleration of high intensity proton beams in the J-PARC RCS. In the wide-band MA-loaded RF cavity, the wake voltage consists of not only the accelerating harmonic component but also the higher harmonics. The higher harmonic components cause the RF bucket distortion. We employ the RF feedforward method to compensate the multi-harmonic beam loading. The full-digital feedforward system is developed, which compensates the first three harmonic components of the beam loading. We present the results of the beam test with a high intensity proton beam (2.5·1013 ppp). The impedance seen by the beam is greatly reduced, the impedance of the fundamental accelerating harmonic is reduced to less than 25 ohms in a full accelerating cycle, while the shunt resistance of the cavity is in the order of 800 ohms. The performance of the feedforward system is promising for achievement of the design beam power, 1 MW, in the future.  
 
WEPZ004 Solid Pulse Transforming Line for DWA coupling, simulation, induction, high-voltage 2769
 
  • L. Zhang
    CAEP/IFP, Mainyang, Sichuan, People's Republic of China
 
  This paper introduces the research work about solid pulse transforming line for dielectric wall accelerator(DWA). We will discuss the impedence of the solid pulse transforming line due to different material. Some research of PCSS(photoconductive semiconductor switch),which was used for DWA, will also be described.  
 
WEPZ007 Multi-mode, Two-beam Accelerator with Feedback cavity, feedback, accelerating-gradient, RF-structure 2778
 
  • S.V. Kuzikov, M.E. Plotkin
    IAP/RAS, Nizhny Novgorod, Russia
 
  A high-gradient accelerator consisted of the test and the drive beam structures is reported. The accelerating structure can be based on dielectric or corrugated cavities separated each other by irises. Each cavity is operated by several axisymmetric, TM-like eigen-modes with longitudinal indices to be related to frequencies. These modes are excited at Fourier harmonics of the drive current which consists of bunches spaced with the same period as test bunches. The superposition of the excited modes introduces a short RF pulse propagated in-phase with a moving test bunch and after reflection by iris (a feedback) this pulse can accelerate next bunch. Such longitudinally-sweeping RF field promises a reduction of the exposure time and due to compact space shape can help to obtain high shunt impedance.  
 
THOBB02 High Gradient Magnetic Alloy Cavities for J-PARC Upgrade cavity, synchrotron, proton, status 2885
 
  • C. Ohmori, O. Araoka, E. Ezura, K. Hara, K. Hasegawa, A. Koda, Y. Makida, Y. Miyake, R. Muto, K. Nishiyama, T. Ogitsu, H. Ohhata, K. Shimomura, A. Takagi, K. Takata, K.H. Tanaka, M. Toda, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
  • T. Minamikawa
    University of Fukui, Fukui, Japan
  • M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura, Japan
 
  Magnetic alloy cavities are used for both MR and RCS synchrotrons. Both cavity systems operate successfully and they generate a higher voltage than could be achieved by an ordinary ferrite cavity system. For the future upgrade of J-PARC, a higher RF voltage is needed. A new RF cavity system using the material, FT3L, is designed to achieve this higher field gradient. A large production system using an old cyclotron magnet was constructed to anneal 85-cm size FT3L cores in the J-PARC Hadron Experiment Hall. The muSR (Muon Spin Rotation/Relaxation/Resonance) Experiments were also carried out to study the magnetic alloy. The status of development on the J-PARC site and a new RF system design will be reported.  
slides icon Slides THOBB02 [2.729 MB]  
 
THOBB03 Research and Development of Novel Advanced Materials for Next-generation Collimators radiation, target, collimation, beam-losses 2888
 
  • A. Bertarelli, G. Arnau-Izquierdo, F. Carra, A. Dallocchio, M. Gil Costa, N. Mariani
    CERN, Geneva, Switzerland
 
  Funding: This work has partly been carried out through the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program.
The study of innovative collimators is essential to handle the high energy particle beams required to explore unknown territory in basic research. This calls for the development of novel advanced materials, as no existing metal-based or carbon-based material possesses the combination of physical, thermal, electrical and mechanical properties, imposed by collimator extreme working conditions. A new family of materials, with promising features, has been identified: metal-diamond composites. These materials are to combine the outstanding thermal and physical properties of diamond with the electrical and mechanical properties of metals. The best candidates are Copper-Diamond (Cu-CD) and Molybdenum-Diamond (Mo-CD). In particular, Mo-CD may provide interesting properties as to mechanical strength, melting temperature, thermal shock resistance and, thanks to its balanced material density, energy absorption. The research program carried out on these materials at CERN and collaborating partners is presented, mainly focusing on the theoretical investigation, material characterization, and manufacturing processes.
 
slides icon Slides THOBB03 [3.948 MB]  
 
THPC183 Application of the Balanced Hybrid Mode in Overmoded Corrugated Waveguides to Short Wavelength Dynamic Undulators undulator, cavity, FEL, electron 3326
 
  • S.G. Tantawi, G.B. Bowden, C. Chang, J. Neilson, M. Shumail
    SLAC, Menlo Park, California, USA
  • C. Pellegrini
    UCLA, Los Angeles, California, USA
 
  Funding: Work Supported by the US Department of Energy
Inspired by recent developments in low-loss overmoded components and systems for ultra-high power RF systems, we explored several overmoded waveguide systems that could function as RF undulators. One promising structure is a corrugated waveguide system operating at the hybrid HE11 mode. This is a new application for that mode. Initial calculations indicate that such a system can be operated at relatively low power levels while obtaining large values for the undulator parameters. RF surface fields are typically low enough to permit superconducting operation. This technology could realize an undulator with short wavelengths and also dynamic control of the undulator parameters including polarization. We introduce the scaling laws governing such a structures, and then show with exact simulations an undulator design that have a wavelength of about 1.4 cm with an undulator parameter K~1. This undulator is intended to be powered by a 50 MW source at a frequency of 11.4 GHz. We describe the experimental setup for testing such a technology.
 
 
THPO016 Design and Implementation the LLC Resonant Transformer power-supply, simulation, controls 3370
 
  • C.-Y. Liu, Y.S. Wong
    NSRRC, Hsinchu, Taiwan
 
  The energy and dc to dc conversion voltage waveform of the LLC resonant transformer are required to achieve optimal working condition of the resonant region frequency. To meet this requirement, a reliable and precise instrument is needed to scan the resonant cure of the LLC resonant transformer such that its output power performance can meet the required specification. In this paper, the design and model of a new LLC resonant transformer deployed in NSRRC is described. This LLC resonant transformer is capable of delivering energy conversion with high efficiency performance, which is better than traditional transformer, and the voltage transfer ratio is depended on the resonant Frequency. Using the simulation circuit model to develop a power converter of it is also included in the design of this new LLC resonant transformer. It has been tested and proven to be working well in power conversion with excellent efficiency and performance.  
 
THPO024 Development of a Non-Linear Kicker System to Facilitate a New Injection Scheme for the BESSY II Storage Ring kicker, injection, vacuum, storage-ring 3394
 
  • O. Dressler, T. Atkinson, M. Dirsat, P. Kuske
    HZB, Berlin, Germany
  • H. Rast
    DELTA, Dortmund, Germany
 
  Top-Up injections without noticeable motion of the stored beam is a challenge. The common method of beam accumulation with a local bump formed by four independent pulsed dipole kicker magnets usually causes beam oscillations. The matching of the four independent kicker systems regarding pulse jitters and shapes is technologically limited. Afterward the beam excitation was reduced more when two kicker magnets on each side of the septum were powered in series by one pulser unit. An even more promising approach is to adopt an alternative injection method deploying a single non-linear kicker magnet with zero Bx,y-field in the center and an off-axis maximum, By, which is horizontally displaced by 10-12 mm. There the injected beam gets kicked and looses half of its transverse momentum. Such a magnet was designed and built as a short in-vacuum magnet with a small vertical gap height. For first beam tests the kicker was placed in the second straight section after the injection point, and the 1.5 μs pulse was designed to deflect the 1.72 GeV beam by 1 mrad. In this paper, the calculations of the magnetic fields, the mechanical design as well as the electrical pulser circuit are described.
*New injection scheme using a pulsed quadrupole magnet in electron storage rings, Kentaro Harada, PHYSICAL REVIEW SPECIAL TOPICS - AB 10, 123501 (2007)
 
 
THPO029 Microwave Beating Generated by a Dual Beam Accelerator beat-wave, plasma, coupling, electron 3406
 
  • G.L. Li, Z.X. Jin, L. Liu, T. Shu, J.H. Yang, C.W. Yuan, J. Zhang
    National University of Defense Technology, Changsha, Kaifu District, People's Republic of China
 
  Funding: National University of Defense Technology
As high power microwave (HPM) technologies gradually matured, the technologies for enhancing the output capacity of HPMs are becoming more and more attractive. However, limited by physics and technology, the approaches for enhancing the output capacity with a single HPM source have encountered difficulties. An alternative method for enhancing the output capacity of HPM sources is the coupling output of dual channel HPM sources. However, if the microwave sources have some coupling with each other, they maybe inter modulate with each other, and the phase-locking of the HPM sources may occur. In order to make sure that the beat waves are generating on the right way, a waveguide diplexer is introduced. Each channel has disjoint pass frequency band, and dual-channel HPM sources are isolated. As the dual-channel electron beams are driven by one accelerator, the HPM sources are expected to have a better match with the accelerator, and even higher microwave power is possible. In the high power experiments, the radiated powers of the beat waves are measured to be about 4.3 GW, 40 ns, the frequencies are about 9.41 GHz and 9.59 GHz.
Correspondence: Guolin Li, College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha, 410073, P. R. China. Email: nudt-liguolin@hotmail.com
 
 
THPO032 Preliminary Design of an Inductive Adder for CLIC Damping Rings kicker, damping, emittance, collider 3409
 
  • J. Holma, M.J. Barnes
    CERN, Geneva, Switzerland
 
  The Compact Linear Collider (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 ultra-low emittance, with high bunch charge, necessary for the luminosity performance of the collider. To limit the beam emittance blow-up due to oscillations, the pulse power modulators for the damping rings kickers must provide extremely flat, high-voltage pulses: specifications call for a 160 ns duration flattop of 12.5 kV, 250 A, with a combined ripple and droop of not more than ±0.02 %. A solid-state modulator, the inductive adder, is a very promising approach to meeting the demanding specifications; this topology allows the use of both digital and analogue modulation. To effectively use modulation techniques to achieve such low ripple and droop requires an in-depth knowledge of the behaviour of the solid-state switching components and their gate drivers, as well as a good understanding of the overall circuit behaviour. This paper describes the initial design of the inductive adder.  
 
THPS023 Automatic Tuner Unit Design, Simulation and Measurement for Automatic Operation of the RF System in the ESS-Bilbao H+ Ion Source plasma, controls, ion, ion-source 3469
 
  • L. Muguira, I. Arredondo, D. Belver, M. Eguiraun, F.J. Fernandez Huerta, J. Feuchtwanger, N. Garmendia, O. Gonzalez, J. Verdu
    ESS-Bilbao, Zamudio, Spain
  • V. Etxebarria, J. Jugo, J. Portilla
    University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
 
  Funding: The present work is supported by the Basque Government and Spanish Ministry of Science and Innovation.
The Ion Source responsible intended to generate a high current and low emittance proton beam for the ESS-Bilbao is currently under construction. The plasma in the source is generated by coupling the 2.72 GHz power input from a Klystron through a magnetic field with an intensity close to the electron cyclotron resonance (ECR) field at the input RF frequency. The electrical behavior of the plasma strongly depends on different plasma characteristics which, at the same time, also depend on the microwave absorption. Thus, in order to maximize the RF power transferred to the plasma, a waveguide automatic tuner unit is employed to match the generator output to the electric impedance of the plasma. This device is generally adjusted manually. In this paper, the design, the 1D and 3D simulation, and measurements are presented which allows us to propose an automatic and real time control of the device. In a first approximation, with the aim of testing the proper operation of the automatic tuner unit, an in-house variable phase shifter and attenuator has been designed and manufactured to simulate the electric behavior of the plasma.
 
 
FRXAA01 Theory of Microwave Instability and Coherent Synchrotron Radiation in Electron Storage Rings synchrotron, electron, shielding, storage-ring 3774
 
  • Y. Cai
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported by Department of Energy Contract No. DE-AC02-76SF00515.
Bursting of coherent synchrotron radiation has been observed and in fact used to generate THz radiation in many electron storage rings. In order to understand and control the bursting, we return to the study of the microwave instability. In this talk, we will report on the theoretical understanding, including recent developments, of the microwave instability in electron storage rings. The historical progress of the theories will be surveyed, starting from the dispersion relation of coasting beams, to the work of Sacherer on a bunched beam, and ending with the Oide and Yokoya method of discretization. This theoretical survey will be supplemented with key experimental results over the years. Finally, we will describe the recent theoretical development of utilizing the Laguerre polynomials in the presence of potential-well distortion. This self-consistent method will be applied to study the microwave instability driven by commonly known impedances, including that of coherent synchrotron radiation.
 
slides icon Slides FRXAA01 [0.948 MB]