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impedance

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MOZBG01 Vacuum Performances in the Most Recent Third Generation Synchrotron Light Sources vacuum, storage-ring, synchrotron, radiation 31
 
  • E. Al-Dmour
    ALBA, Bellaterra
  Several 3rd generation synchrotron light sources were built and commissioned during the last ten years. The vacuum system of these light sources was designed using different approaches, but with the same objectives which guarantee the lowest outgassing rate and the highest pumping speed that by the end will achieve the lowest influence in the circulated beam (longest life time, the lowest impedance and instabilities, etc). The performance of recently commissioned rings (DIAMOND, SOLEIL and the Australian Light Source) are presented, together with a comparison of the different approaches which have been used in the design of the vacuum system and the lessons for the design of new vacuum systems.  
slides icon Slides  
 
MOPC060 Transverse Resistive-wall Wake of a Round Pipe with Finite Thickness and its Effect on the ERL Multi-bunch Beam simulation, vacuum, injection, lattice 202
 
  • N. Nakamura
    ISSP/SRL, Chiba
  We already started to study the effect of resistive-wall wake on the multi-bunch beam in an ERL (energy recovery linac)-based light source*, because resistive-wall beam breakup(RWBBU) could be caused by the cumulative transverse wake generated by interaction between the resistive vacuum pipe and the intense multi-bunch beam. However the resistive-wall wake function of a round pipe used so far for studying the RWBBU was valid only in a limited time range and improper to the RWBBU simulation for a longer time period. Therefore we analytically derived an exact expression of resistive-wall impedance of a round pipe with finite thickness over all the frequency range and numerically calculated the resistive-wall wake functions of several different pipes from the exact impedance expression. The calculated wake functions enabled us to study and simulate the beam behavior in an ERL made of the pipes accurately. We will present the transverse resistive-wall wake of a round pipe with finite thickness and its effect on the ERL multi-bunch beam.

*N. Nakamura et al., Proceedings of PAC07, Albuquerque, June 2007, pp. 1010-1012.

 
 
MOPC095 Mechanical and Thermal Prototype Testing for a Rotatable Collimator for the LHC Phase II Collimation Upgrade simulation, collimation, power-supply, beam-losses 286
 
  • J. C. Smith, J. E. Doyle, L. Keller, S. A. Lundgren, T. W. Markiewicz
    SLAC, Menlo Park, California
  The Phase II upgrade to the LHC collimation systems calls for complementing the 30 high robust Phase I graphite collimators with 30 high Z, low impedance Phase II collimators. The design for the collimation upgrade has not been finalized. One option is to use metallic rotatable collimators and this design will be discussed here. The Phase II collimators must be robust in various operating conditions and accident scenarios. A series of prototype collimator jaws have been tested for both mechanical and thermal compliance with the design goals. Collimator jaw shape after thermal expansion benchtop tests were compared to ANSYS simulation results. Mechanical tests were also performed to demonstrate fabrication precision and collimator movement operation as designed.  
 
MOPC096 Design of a Rotatable Copper Collimator for the LHC Phase II Collimation Upgrade collimation, simulation, shielding, insertion 289
 
  • J. C. Smith, J. E. Doyle, L. Keller, S. A. Lundgren, T. W. Markiewicz
    SLAC, Menlo Park, California
  • L. Lari
    EPFL, Lausanne
  The Phase II upgrade to the LHC collimation systems calls for complementing the 30 high robust Phase I graphite collimators with 30 high Z, low impedance Phase II collimators. The design for the collimation upgrade has not been finalized. One option is to use metallic rotatable collimators and this design will be discussed here. The Phase II collimators must be robust in various operating conditions and accident scenarios. Design issues include:
  1. Collimator jaw deflection due to heating and sagita must be small when operated in the steady state condition,
  2. Collimator jaws must withstand transitory periods of high beam impaction with no permanent damage,
  3. Jaws must recover from accident scenario where up to 8 full intensity beam pulses impact on the jaw surface and
  4. The beam impedance contribution due to the collimators must be small to minimize coherent beam instabilities.
The current design will be presented. 		 
 
MOPC119 Low-Output-Impedance RF System for the ISIS Second Harmonic Cavity synchrotron, beam-loading, controls, acceleration 343
 
  • Y. Irie, S. Fukumoto, K. Muto, A. Takagi
    KEK, Ibaraki
  • D. Bayley, I. S.K. Gardner, A. Seville, J. W.G. Thomason
    STFC/RAL/ISIS, Chilton, Didcot, Oxon
  • J. C. Dooling, D. Horan, R. Kustom, M. E. Middendorf
    ANL, Argonne, Illinois
  • T. Oki
    Tsukuba University, Ibaraki
  Low-output-impedance RF system for the second harmonic cavity in the ISIS synchrotron has been developed by the collaboration between Argonne National Laboratory, US, KEK, Japan and Rutherford Appleton Laboratory, UK. Low output impedance is realized by the feedback from plate output to grid input of the final triode amplifier, resulting in less than 30 Ω over the frequency range of interest. Precise control of the second harmonic voltage can then be realized without considering beam loading effects. Beam test scenario in the ISIS synchrotron is discussed.  
 
MOPC120 J-PARC RCS Non-linear Frequency Sweep Analysis resonance, controls, acceleration, damping 346
 
  • A. Schnase, K. Haga, K. Hasegawa, M. Nomura, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Toda, M. Yoshii
    KEK, Ibaraki
  A standard method to measure the S21-transfer function of a system of amplifier and cavity involves a network analyzer and a linear or logarithmic frequency sweep. However, to characterize the transfer function of the broadband (Q=2) RCS RF system, we measure and analyze several harmonics at the same time under high power ramping conditions. A pattern driven DDS system generates frequency and amplitude as in accelerator operation. During the 20ms acceleration part of the cycle, a large memory oscilloscope captures the RF-signals. The data are analyzed off-line with a down-conversion process like in a multi-harmonic LLRF-system, resulting in multi-harmonic amplitude and phase information. Using this setup in the cavity test phase we were able to find and cure resonances before installation into the tunnel. We show examples. RCS is in the commissioning phase and has reached the milestone of acceleration to final energy and beam extraction. 10 RF systems are in operation, and the low-level RF system controls the fundamental h(2) and the second harmonic h(4). Using a multi-harmonic analysis during beam operation allows checking the RF system behavior with and without beam-loading.  
 
MOPD019 Construction and Quality Control of Synchrotron SOLEIL Beam Position Monitors vacuum, controls, simulation, synchrotron 487
 
  • E. Cenni, M. Canetti, F. Gangini
    RIAL VACUUM S.p. A, Parma
  • J. L. Billaud
    Saint-Gobain C. R.E. E., Cavaillon
  • L. Cassinari, J.-C. Denard, C. Herbeaux
    SOLEIL, Gif-sur-Yvette
  SOLEIL is a third generation synchrotron light source located near Paris. Due to the high performance required for SOLEIL’s diagnostics, a special production procedure was tailored. During the production of 131 Beam Position Monitors (BPM) more than 500 feedthroughs were inspected; all of them passed strict tests at different stages of the production: Leak test (< 10-10 mbar l/s), Dimensional control (Displacement <0.050 mm), Vacuum test (Specific Outgassing < 10-12 mbar l/s cm2, Residual Gas Analysis) and Electrical test (Capacitance measure ~8pF, Insulation >50 MΩ, Impedance <0.1 Ω). All the established procedures and tests have been performed in a tight partnership that was more than a simple contractual framework, in which an intensive collaboration led to a knowledge transfer between SOLEIL and Rial Vacuum. The result has been a high percentage of success (few feedthroughs over 500 were replaced) during preliminary tests and a deeper knowledge of “BPM problem solving”; in this article are presented different test procedures to obtain high quality and high performance BPMs.  
 
MOPP007 Wakefield Calculations - Comparison between Simulations and Experimental Data simulation, emittance, collider, dipole 562
 
  • A. Bungau, R. J. Barlow
    UMAN, Manchester
  In linear colliders the collimator wakefields have a significant effect on emittance growth, beam jitter and background estimates. Each simulation code models the collimator wakefields using a different approach and a discussion of the formalism for incorporating wakefields into the particle tracking code Merlin is included in this paper. Using simple collimator types we present the different predictions for bunch shape effects, and also for the wakefield kicks. These kicks are also compared with experimental results from SLAC End Station A.  
 
MOPP045 Study of the Validity of K. Bane's Formulae for the CLIC Accelerating Structure dipole, RF-structure, target, luminosity 646
 
  • R. Zennaro
    CERN, Geneva
  The comprehension of short range wake is essential for the design of CLIC. Useful tools are the Karl Bane's formulae which predict the short range wake for periodic 2D symmetry structures. The comparison of 2D computations based on ABCI with predicted results and the study of the range of validity of these formulae are the subjects of this paper. A new fitting of the computational results is proposed for structures with very small aperture. A model for rounded iris structures is also proposed.  
 
MOPP049 Collective Effects in the CLIC Damping Rings space-charge, ion, damping, emittance 658
 
  • G. Rumolo, J. B. Jeanneret, Y. Papaphilippou, D. Quatraro
    CERN, Geneva
  The possible performance limitations coming from collective effects in the CLIC damping rings are the subject of this paper. In particular, the consequences of space charge, due to the very high beam brilliance, and of the resistive wall impedance, due to the locally very small beam pipe, are considered potentially dangerous in spite of the high beam energy. Hence, they have been studied in detail with the HEADTAIL code, which has been modified in order to take into account a finer lattice structure as well as multi-bunch effects of the resistive wall wake field. The study aims at setting the intensity thresholds determined by these phenomena.  
 
MOPP056 Beam Coupling Impedance in the ILC Damping Rings insertion, damping, vacuum, coupling 670
 
  • M. Korostelev, O. B. Malyshev, A. Wolski
    Cockcroft Institute, Warrington, Cheshire
  • A. F. Grant, J. Lucas
    STFC/DL, Daresbury, Warrington, Cheshire
  The ILC damping rings have stringent specifications for beam quality and stability. To avoid instabilities, the various components in the vacuum chamber will need to be carefully designed to minimize the longitudinal and transverse wake fields. We present the results of impedance calculations for various components that are expected to make a significant contribution to the overall machine impedance.  
 
MOPP074 Improvement of an S-band RF-gun cavity with a Cs-Te Photo-cathode cathode, electron, scattering, resonance 721
 
  • A. Murata, Y. Hama, T. Hirose, Y. Kato, K. Sakaue, T. Suzuki, M. Washio
    RISE, Tokyo
  • H. Hayano, N. Kudoh, T. T. Takatomi, N. Terunuma, J. Urakawa
    KEK, Ibaraki
  • Y. Kamiya
    University of Tokyo, Tokyo
  • S. Kashiwagi
    ISIR, Osaka
  • M. Kuriki
    Hiroshima University, Graduate School of Science, Higashi-Hiroshima
  • R. Kuroda
    AIST, Tsukuba, Ibaraki
  A 1.6cell S-band photo-cathode RF-Gun is one of the good alternatives of the short pulse electron source. Therefore,we are operating as a high brightness short pulse electron source for studying a reaction of radiation chemistry,an inverse Compton scattering at Waseda University and as an injector at KEK-ATF. To improve an electron beam quality and to reduce a dark current,we decided to improve the RF-Gun cavity. Frequency tuning of the half cell of existing RF-gun was performed by the torque control of Helicoflex seal on the cathode plate and two moving rod type tuners were installed on the full cell. Newly designed RF-Gun cavity has four compact tuners on each cell,which can be tune the frequency to deform the cavity wall,to remove the Helicoflex seal and tuning holes that were considered to be the major cause of electric discharge and/or a dark current source. According to these improvements,the Q-value and shunt impedance of the cavity is 30% larger than that of existing guns. As the result,the reduction of dark current is succeeded and the beam energy is reached up to 5.5MeV at 10MW RF input. The detailed results of electron beam generation will be reported at the conference.  
 
MOPP083 Status of High Power Tests of Normal Conducting Single-cell Structures klystron, vacuum, damping, electron 742
 
  • V. A. Dolgashev, S. G. Tantawi
    SLAC, Menlo Park, California
  • Y. Higashi, T. Higo
    KEK, Ibaraki
  We report results of ongoing high power tests of single cell traveling wave and standing wave structures. These tests are part of an experimental and theoretical study of rf breakdown in normal conducting structures at 11.4 GHz*. The goal of this study is to determine the gradient potential of normal-conducting, rf powered particle beam accelerators. The test setup consists of reusable mode launchers and short test structures and powered by SLAC’s XL-4 klystron. The mode launchers and structures were manufactured at SLAC and KEK and tested in SLAC klystron test laboratory.

*V. A. Dolgashev, S. G. Tantawi, et al. “High Power Tests of Normal Conducting Single Cell Structures,” SLAC-PUB-12956, PAC07, Albuquerque, New Mexico, 25-29 June 2007, pp 2430-2432.

 
 
MOPP085 Bench Characterization of a Prototype of a 3rd Harmonic Cavity for the LNLS Electron Storage Ring electron, storage-ring, synchrotron, controls 748
 
  • R. H.A. Farias, D. A. Nascimento, C. Pardine, P. F. Tavares
    LNLS, Campinas
  The UVX electron storage ring at the Brazilian Synchrotron Light Laboratory suffers from longitudinal instabilities driven by a HOM of one of the RF cavities. The operational difficulties related to these unstable modes were successfully overcome by determining the proper cavity temperature set point in combination with phase modulation of the RF fields at the second harmonic of the synchrotron frequency. However, a serious drawback of the method is to increase the energy spread of the electron beam, which is detrimental for the undulator emission spectrum. The use of higher harmonic cavities is a more appropriate technique since it provides damping of the longitudinal modes without increasing the energy spread. A full scale prototype of a 3rd harmonic cavity was manufactured at the LNLS workshops and had its main rf properties measured. Special care was taken to measure the shunt impedance of the fundamental resonant mode since it determines how many cavities will be necessary for the adequate operation of the system, which is designed to operate in passive mode. In this work we present the results of the bench characterization of the cavity.  
 
MOPP088 The High Harmonics Cavity System for the New Experimental Storage Ring at FAIR coupling, electron, bunching, emittance 757
 
  • R. G. Heine, C. Dimopoulou, U. Laier
    GSI, Darmstadt
  The "Facility for Antiproton and Ion Research" (FAIR) will consist of several synchrotrons and storage rings dedicated to target experiments as well as in-situ experiments. One of the in-situ experiments is ELISe, a head-on collision of a heavy ion beam in the new experimental storage ring(NESR) with an electron beam prepared in the electron ring (ER). The vertex is placed in a bypass to the NESR where both rings have a common straight section. To prepare the heavy ion beam for collision with the bunched electron beam circulating at a fixed repetition rate a dedicated RF system called high harmonics cavity system (HHC) operating at a frequency of 44.7MHz is needed. The HHC will be realised as a disk loaded coaxial quarter wave resonator. This paper deals with the actual development status of this RF system, including analytically derived voltage demands, multipactor thresholds and considerations on input coupling and HOM damping.  
 
MOPP092 Efficient Fan-out RF Vector Control Algorithm controls, coupling, proton 766
 
  • Y. W. Kang
    ORNL, Oak Ridge, Tennessee
  A new RF vector control algorithm for fan-out power distribution using reactive transmission line circuit parameters for maximum power efficiency is presented. This control with fan-out power distribution system is considered valuable for large scale SRF accelerator systems to reduce construction costs and save on operating costs. Other fixed power splitting systems with individual cavity voltage control at each cavity input may not deliver the power efficiency since excessive power needs to be maintained at each cavity input. In a fan-out RF power distribution system, feeding multiple accelerating cavities with a single RF power generator can be accomplished by adjusting phase delays between the load cavities and reactive loads at the cavity inputs for independent control of cavity RF voltage vectors. In this approach, the RF control parameters for a set of specified cavity RF voltage vectors is determined for a whole fan-out system. The reactive loads and phase shifts can be realized using high power RF phase shifters.  
 
MOPP096 C-band Linac Optimization for a Race-track Microtron linac, coupling, simulation, resonance 778
 
  • Yu. A. Kubyshin
    UPC, Barcelona
  • D. Carrillo, L. García-Tabarés, F. Toral
    CIEMAT, Madrid
  • A. V. Poseryaev, V. I. Shvedunov
    MSU, Moscow
  Optimization results of a C-band standing wave on-axis coupled linac for a miniature race-track microtron (RTM) are presented. The optimization procedure includes three steps: choice of the linac cells lengths and field strength following requirements of the RTM beam dynamics, 2D cells geometry optimization to maximize the shunt impedance and minimize the surface field strength and, finally, full scale 3D optimization. The 3D calculations were done independently with two codes: ANSYS and HFSS. Various methods of calculation of the coupling slots dimensions, including the waveguide-linac coupling slot, are described in detail.  
 
MOPP097 Measurements on the Rf Cavity for the ALBA Storage Ring coupling, storage-ring, vacuum, pick-up 781
 
  • M. L. Langlois, M. Cornelis, F. Pérez, P. Sanchez
    ALBA, Bellaterra
  ALBA storage ring will use 6 ambient temperature nose cone HOM damped cavities tuned at 500 MHz, designed at BESSY and known as the EU cavity. A first one, manufactured by ACCEL, was delivered in 2007 to investigate on its behaviour. This paper describes the data collected during investigation. First, bead-pull measurements were performed to assess impedance, both on fundamental and high order modes. Emphasis was put on E011, due to the discrepancy between expected values and results for this mode. The vacuum bake-out and related pressure are shown. Then, the cavity was conditioned and observations were made on multipacting levels, conditioning time and surface temperatures. The latter were found inhomogeneous and leads are detailed to avoid local overheating.  
 
MOPP098 A 201-MHz Normal Conducting RF Cavity for the International MICE Experiment coupling, vacuum, emittance, focusing 784
 
  • D. Li, A. J. DeMello, S. P. Virostek, M. S. Zisman
    LBNL, Berkeley, California
  • R. A. Rimmer
    Jefferson Lab, Newport News, Virginia
  MICE is a demonstration experiment for the ionization cooling of muon beams. Eight RF cavities are proposed to be used in the MICE cooling channel. These cavities will be operated in a strong magnetic field; therefore, they must be normal conducting. The cavity design and construction are based on the successful experience and techniques developed for a 201-MHz prototype cavity for the US MUCOOL program. Taking advantage of a muon beam’s penetration property, the cavity employs a pair of curved thin beryllium windows to terminate conventional beam irises and achieve higher cavity shunt impedance. The cavity resembles a round, closed pillbox cavity. Two half-shells spun from copper sheets are joined by e-beam welding to form the cavity body. There are four ports on the cavity equator for RF couplers, vacuum pumping and field probes. The ports are formed by means of an extruding technique.  
 
MOPP102 High Field Gradient RF System for a Spiral FFAG, RACCAM acceleration, extraction, vacuum, injection 793
 
  • C. Ohmori
    KEK, Ibaraki
  • J. Fourrier, J. Pasternak
    LPSC, Grenoble
  • F. Meot
    CEA, Gif-sur-Yvette
  A high field-gradient RF system for a spiral FFAG is described. It is wideband to cover the frequency of 3 to 7.5 MHz. The beam will be accelerated with a high repletion rate of 100 Hz to fit requirements for hadron therapy. The cavity has a wide aperture of 90 cm in horizontal direction to allow a large excursion for beam acceleration. It has less than 40 cm in length to fit a very short straight section.  
 
MOPP103 High Field Gradient RF System for Bunch Rotation in PRISM-FFAG power-supply, controls, cathode, synchrotron 796
 
  • C. Ohmori
    KEK, Ibaraki
  • M. Aoki, Y. Arimoto, I. Itahashi, Y. Kuno, Y. Kuriyama, A. Sato, M. Y. Yoshida
    Osaka University, Osaka
  • Y. Iwashita
    Kyoto ICR, Uji, Kyoto
  • Y. Mori
    KURRI, Osaka
  The PRISM project aims to supply a high quality muon beam using a wide aperture FFAG for mu-e conversion experiment. The low energy muon which has a large momentum spread will be manipulated in the FFAG using a bunch rotation technique with a low frequency RF around 3.5 MHz. Because of a short lifetime of muon, the rotation should be end in 5-6 turns in the FFAG and more than 2 MV is needed. The low frequency RF system using a magnetic alloy is designed to achieve a very high field gradient of more than 200 kV/m. The whole system is designed for a very low duty pulse operation to minimize the cost. The system has been modified to operate at 2 MHz for the beam test using alpha particle. A field gradient of more than 100 kV/m has been obtained by the preliminary test.  
 
MOPP104 Possible Upgrade Scenario for J-PARC Ring RF synchrotron, acceleration, power-supply, linac 799
 
  • C. Ohmori, K. Hara, A. Takagi, M. Toda, M. Yoshii
    KEK, Ibaraki
  • K. Hasegawa, M. Nomura, A. Schnase, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  The whole J-PARC RCS RF system is operational and during beam commissioning in 2007 the beam in RCS was successfully accelerated to final energy and then extracted. The Main Ring RF system has been installed in the tunnel. Both Ring RF systems are based on the new technology using magnetic alloy loaded cavities and have achieved higher field gradient than existing ferrite base RF systems in this frequency region. For the future upgrade of the J-PARC Main Ring, a short accelerating cycle is required to increase the average beam current. In this paper, a possible upgrade scenario for RF cavities based on improvements of the magnetic alloy ring cores will be described.  
 
MOPP108 Status of HOM Damped Room-temperature Cavities for the ESRF Storage Ring coupling, simulation, storage-ring, damping 808
 
  • V. Serriere, A. K. Bandyopadhyay, L. Goirand, J. Jacob, D. Jalas, B. Ogier, A. Triantafyllou
    ESRF, Grenoble
  • N. Guillotin
    SOLEIL, Gif-sur-Yvette
  At the ESRF, longitudinal coupled bunch instabilities driven by cavity HOM are currently avoided up to the nominal current of 200 mA by precisely controlling the temperatures of the six five-cell cavities installed on the storage ring. A longitudinal bunch by bunch feedback has recently allowed to overcome the remaining HOM and thereby increase the current in the storage ring to 300 mA. In parallel, HOM damped room-temperature cavities are being developed for highly reliable passive operation at 300 mA. They are designed for a possible later upgrade to higher currents.  
 
MOPP128 Comparison of Stretched-wire, Bead-pull and Numerical Impedance Calculations on 3.9 GHz Dipole Cavities dipole, simulation, higher-order-mode, radio-frequency 859
 
  • P. Goudket, C. D. Beard, P. A. McIntosh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • G. Burt, A. C. Dexter
    Cockcroft Institute, Lancaster University, Lancaster
  • R. M. Jones
    Cockcroft Institute, Warrington, Cheshire
  In order to verify detailed impedance and wakefield simulations, the resonant modes in an aluminium model of the 9-cell ILC crab cavity were investigated using a stretched-wire frequency domain measurement, as well as frequency-domain bead-pull measurements. These measurements were compared to numerical simulations in order to verify that the complete cavity mode spectrum could be experimentally characterised for this high frequency structure. The analysis of the results and the accuracy and/or limitations of each method is presented.  
 
MOPP140 Status and Test Results of High Current 5-cell SRF Cavities Developed at JLAB damping, dipole, simulation, quadrupole 886
 
  • F. Marhauser, G. Cheng, G. Ciovati, W. A. Clemens, E. Daly, D. Forehand, J. Henry, P. Kneisel, S. Manning, R. Manus, R. A. Rimmer, C. Tennant, H. Wang
    Jefferson Lab, Newport News, Virginia
  A new compact CW cryomodule development for use in future ERLs and FELs is underway at JLAB. Five-cell SRF cavities have been built at 1497 MHz for moderate RF input power scenarios with waveguide endgroups to efficiently transfer the beam induced HOM energy to room temperature loads. Effort has been made as well to provide a good real-estate gradient, cryogenic efficiency and HOMs tuned to safe frequencies to minimize HOM power extracted from the beam. Preliminary tests carried out earlier for two single-cell cavities at 1497 MHz cavity -one with a waveguide endgroup- and a bare 1497 MHz five-cell cavity have exceeded gradient and Qo specifications with no signs of multipacting and encouraged us to built two fully equipped 1497 MHz five-cell cavities. We report on the latest test results and the HOM impedance budget of the cavity used to evaluate BBU limits based on special machine optics.  
 
MOPP152 Bunch Lengthening Harmonic System for NSLS-II ion, damping, injection, emittance 904
 
  • J. Rose, N. A. Towne
    BNL, Upton, Long Island, New York
  NSLS-II is a new ultra-bright 3GeV 3rd generation synchrotron radiation light source. The performance goals require operation with a beam current of 500mA and a bunch current of at least 0.5mA. Ion clearing gaps are required to suppress ion effects on the beam. The natural bunch length of 3mm is planned to be lengthened by means of a third harmonic cavity in order to provide a margin for the Touschek limited lifetime and for instability threshold currents. The paper presents the analysis of the bunch lengthening in this dual RF system consisting of a 500MHz fundamental and 1500 MHz harmonic system in presence of strong transient beam loading. A conceptual design of a 1500MHz SCRF cavity is developed and design performance is discussed.  
 
TUOBG03 Electron Beam Dynamics in the Long-pulse, High-current DARHT-II Linear Induction Accelerator electron, induction, focusing, dipole 968
 
  • C. Ekdahl, E. O. Abeyta, P. Aragon, R. D. Archuleta, G. V. Cook, D. Dalmas, K. Esquibel, R. J. Gallegos, R. W. Garnett, J. F. Harrison, E. B. Jacquez, J. Johnson, B. T. McCuistian, N. Montoya, S. Nath, K. Nielsen, D. Oro, L. J. Rowton, M. Sanchez, R. D. Scarpetti, M. Schauer, G. J. Seitz, H. V. Smith, R. Temple
    LANL, Los Alamos, New Mexico
  • H. Bender, W. Broste, C. Carlson, D. Frayer, D. Johnson, C.-Y. Tom, C. P. Trainham, J. T. Williams
    NSTec, Los Alamos, New Mexico
  • T. C. Genoni, T. P. Hughes, C. H. Thoma
    Voss Scientific, Albuquerque, New Mexico
  • B. A. Prichard, M. E. Schulze
    SAIC, Los Alamos, New Mexico
  We are now operating the full-scale DARHT-II linear induction accelerator (LIA) at its rated energy, accelerating 2-kA electron beams to more than 17 MeV. The injector produces a beam pulse with a full-width at half maximum (FWHM) greater than 2.5 microseconds, and a ~0.5 microsecond rise time. This long risetime is deliberately scraped off in a special beam-head cleanup zone (BCUZ) before entering the 68-cell main accelerator. The accelerated electron beam pulse has a flat-top region where the final electron kinetic energy varies by less than 1% for more than 1.5 microseconds. We will discuss the tuning of the injector, BCUZ, and accelerator; and we will present data for the resulting beam transport and dynamics. We will also present beam stability data, which we will relate to previous stability experiments at lower current and energy*.

*Carl Ekdahl et al. "Long-pulse beam stability experiments on the DARHT-II linear induction accelerator," IEEE Trans. Plasma. Sci. Vol. 34, 2006, pp. 460-466.

 
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TUOBM02 The Development of the Separated Function RFQ Accelerator in Peking University rfq, simulation, focusing, acceleration 1007
 
  • X. Q. Yan, J.-E. Chen, J. X. Fang, S. L. Gao, Z. Y. Guo, Y. R. Lu, Z. Wang, K. Zhu
    PKU/IHIP, Beijing
  The progress of the Separated Function RFQ (SFRFQ) accelerator, which can raise the field gradient of acceleration while maintaining the transverse focusing power sufficient for high current beam, is presented. In order to demonstrate the feasibilities of the novel accelerator, a prototype cavity was designed and constructed. Correspondingly, a code SFRFQCODEV1.0 was developed specially for cavity design and beam dynamics simulation. The prototype cavity will be verified as a post-accelerator for ISR RFQ-1000 (Integral Split Ring RFQ) and accelerate O+ from 1 MeV to 1.6 MeV. To inject a higher current oxygen beam for the prototype cavity, the beam current of ISR RFQ-1000 was upgraded to 2 mA. The status of high power and beam test of the prototype cavity are presented in this paper.  
slides icon Slides  
 
TUPC010 Single Bunch Studies at the Australian Synchrotron single-bunch, storage-ring, synchrotron, diagnostics 1062
 
  • R. T. Dowd, M. J. Boland, G. LeBlanc, M. J. Spencer, Y. E. Tan
    ASP, Clayton, Victoria
  Studies using a single high charge electron bunch have been conducted at the Australian Synchrotron to characterise the impedance of the machine at various stages of commissioning and insertion device configuration. This paper will present the results of these studies and show the time evolution of machine impedance with increasing number of insertion devices.  
 
TUPC021 High Bandwidth Wall Current Monitor for CTF3 resonance, coupling, shielding, electromagnetic-fields 1092
 
  • A. D'Elia, R. Fandos, L. Soby
    CERN, Geneva
  Wall Current Monitors (WCM) are commonly used to observe the time profile and spectra of a particle beam by detecting its image current. For the 3rd CLIC Test Facility (CTF3), a WCM having a very large bandwidth (100kHz-20GHz) is in principle required. This very stringent request was critically reviewed because the low cut-off frequency of 100 kHz is quite outstanding. It was initially chosen because of the bunch train length but, in reality, because of the high frequency cut-off of 20GHz, the low frequency cut-off should rather be related to the maximum expected Missing Bunch Ratio (MBR). The solution that we propose has a low frequency cut-off of 2GHz corresponding to an MBR of 1/6 for 83ps bunch spacing. If needed, it could be lowered to 400MHz (MBR equal to 1/30). That solution has been fully characterized both from an electromagnetic and from a mechanical point of view. The first tests of a prototype are foreseen in February 2008.  
 
TUPC041 Design of Cold BPM Feedthrough simulation, resonance, insertion, cryogenics 1146
 
  • K. Iwamoto, Y. Ikeda
    KFG, NEUSS
  • T. Kitamura, T. Matsuoka
    KYOCERA Corporation, Higashiomi-city, Shiga
  We have designed many BPM feedthrough used metallized ceramic components. We select the best material of ceramic and metal ajusted for magnetism and the material of chamber. The request for accelerator application that low temperature and RF property has increased in recent years. In this presentation,we report on the design of the BPM feedthrough for low temperature and for the RF up to 20GHz. We appreciated the bonding strength for ceramic and metal in low temperature 4K,77K. Mo/Mn metallised ceramic is brazed between Fe-Ni-Co Alloy metal components using Ag-Cu brazing material. Ceramic is 99% Alumina which is commonly used for UHV application. The tensile strength in low temperature is lower than in R. T.approximately 10%, but the dispersion affected by brazing flow condition is bigger than this temperature effect. The influence of low temperature is less than brazing flow condition, therefore the bonding strength of metallised ceramic is enough for UHV application at 4K.  
 
TUPC054 Pulse-by-pulse Photon Beam Monitor with Microstripline Structure in NSRRC photon, storage-ring, synchrotron, synchrotron-radiation 1176
 
  • C. K. Kuan, C. L. Chen, J.-R. Chen, G.-Y. Hsiung, I. C. Sheng, Z.-D. Tsai, D.-J. Wang
    NSRRC, Hsinchu
  • H. Aoyagi, H. Kitamura, S. Takahashi
    JASRI/SPring-8, Hyogo-ken
  In order to diagnostic pulse-by-pulse beam movement of photon beam, NSRRC(Taiwan) and SPring-8 (Japan) have worked together to develop a front end beam monitor with microstripline structure, which is designed to have specific impedance of 50 ohm. The detector head is composed of a metal line (copper), ceramic plates (aluminum nitride) and a cooling base (copper tungsten). The metal line functions as a photocathode. The metal line is directly connected to SMA feed-through connectors to have fast response time. The detector head has been fabricated in SPring-8, and mounted on the monitor chamber and installed in NSRRC Superconducting Wiggler (SW) front end. The beam monitor can be used to examine not only pulse-by-pulse photon beam, but also the storage ring intensity and the pulse timing. Unique feature of the monitor is to produce unipolar short pulses. The design, fabrication and the measurement will be presented in this paper.  
 
TUPD003 Upgrading the Fast Extraction Kicker System in SPS LSS6 kicker, extraction, proton, pick-up 1437
 
  • M. J. Barnes, L. Ducimetière, B. Goddard, J. A. Uythoven
    CERN, Geneva
  A fast extraction system, located in the LSS6 region of the CERN SPS accelerator, transfers 450 GeV/c protons, as well as ions, via the transfer line TI 2 towards the LHC. The system includes three travelling wave kicker magnets, all powered in series, energised by a single Pulse Forming Network (PFN) and terminated by a short circuit. The specification for the system requires a kick flattop of 7800 ns duration with a ripple of not more than ±0.5%. Recent measurements with beam show that the ±0.5% kick specification is achieved over the initial 7100 ns of the kick flattop; however the ripple over 7800 ns is ±0.7%. Electrical measurements have been carried out on each of the three magnets: these have been compared with the beam measurements and the contribution of each magnet to the detailed shape of the flattop kick has been determined. This paper reports the results of measurements and describes the plans to upgrade the system to fully meet the kick specification.  
 
TUPD008 Marx Bank Technology for Accelerators and Colliders controls, collider, diagnostics, linear-collider 1449
 
  • J. A. Casey, F. O. Arntz, M. P.J. Gaudreau, M. K. Kempkes, I. Roth
    Diversified Technologies, Inc., Bedford, Massachusetts
  Diversified Technologies, Inc. (DTI) has developed high power, solid-state Marx Bank designs for a range of accelerator and collider designs. We estimate the Marx topology can deliver equivalent performance to conventional designs, while reducing acquisition costs by 25-50%. In this paper DTI will describe the application of Marx based technology to two different designs: a long-pulse ILC focused design (140 kV, 160 A, 1.5 ms), and a short-pulse design (500 kV, 265 A, 3 us). These designs span the known requirements for future accelerator modulators. For the ILC design, the primary challenge is minimizing the overall size and cost of the storage capacitors in the modulator. For the short-pulse design, the primary challenge is high speed operation, to limit the energy lost in the pulse rise-time while providing a very tight (± 3%) voltage flattop. Each design demands unique choices in components and controls, including the use of electrolytic capacitors in the ILC Marx design. This paper will review recent progress in the development and testing of both of these prototype Marx designs, being built under two separate DOE Phase II SBIR grants.  
 
TUPD014 Detailed Design, Manufacturing and Testing of a Strip-line Extraction Kicker for CTF3 Combiner Ring kicker, simulation, vacuum, extraction 1458
 
  • I. Rodriguez, L. García-Tabarés, E. Rodríguez García, F. Toral
    CIEMAT, Madrid
  • D. Alesini, A. Ghigo, F. Marcellini, M. Zobov
    INFN/LNF, Frascati (Roma)
  • T. Fowler, I. Syratchev
    CERN, Geneva
  The first calculations to design the CTF3 Combiner Ring extraction kicker are reported elsewhere. The last computing step before fabrication is the wakefield analysis, to determine if the bunch disturbance is acceptable. Two different codes have been used for cross-checking: CST Particle Studio and GDFidl. The computation is challenging because of the long structure (2.4 m) with a short bunch (3 mm). Besides, both transitions are not equal, because of different straight sections of the input and output beam pipe, and then the solution method is more complex. On the other hand, the main challenges for manufacturing are the long electrodes support via ceramic stand-offs and the flexible electrical connections to allow for electrodes thermal differential displacement. Special tooling has also been developed for assembly within the required tolerances. The device has been successfully leak tested. High frequency transmission coefficients and high voltage dielectric strength were also measured.  
 
TUPD021 Sliding Force Measurements on the LHC RF Contact Plug in Modules at 15 K and in UHV vacuum, cryogenics 1473
 
  • K. Artoos, M. Guinchard, T. Renaglia
    CERN, Geneva
  Some sliding RF contacts mounted in the Plug In Modules in the LHC interconnects failed during a thermal cycle between 4.2 K and room temperature. Gold-coated copper-beryllium RF fingers buckled during the warm up of the machine, indicating that one or more parameters during operation (e.g., the friction coefficient under vacuum) might be different from what was used in the calculations. This report describes the measurement of the longitudinal forces acting on the sliding RF fingers at operating vacuum and temperatures.  
 
TUPD038 Beam Test of a Movable Collimator (Mask) with Low Beam Impedance positron, vacuum, simulation, collider 1511
 
  • Y. Suetsugu, K. Shibata
    KEK, Ibaraki
  • A. Morishige, Y. Suzuki, M. Tsuchiya
    Kinzoku Giken Co. Ltd., Ebina
  A movable collimator with low beam impedance for future high-intensity machines has been investigated in KEK*. The metal head of the collimator is supported by a dielectric material in order to reduce the interference with beams. The first test model was installed into the KEK B-factory (KEKB) positron ring last year. The head and the support was alumina ceramic, but only the head was coated by copper to realize a conductive layer. The support, however, was finally melted during the beam operation due to the overheating by intense electromagnetic fields induced by bunches. Based on the experience, the design was revised and the second test model was manufactured, where the head and the support were made of graphite and artificial diamond, respectively. Graphite is a conductive material with high thermal strength, and diamond, on the other hand, is a dielectric material with high thermal conductivity as well as the strength. The second test model is installed in the spring of this year, and tested again with beams during the beam operation to prove the principle. The results of the beam tests will be presented here.

* Y. Suetsugu, K. Shibata, A. Morishige, Y. Suzuki, M. Tsuchiya, “Design Study of a Movable Mask with Low Bema Impedance”, PRST-AB, 9, 2006, 103501.

 
 
TUPP019 Wakefield and RF Kicks due to Coupler Asymmetry in TESLA-type Accelerating Cavities emittance, linac, coupling, collider 1571
 
  • K. L.F. Bane, C. Adolphsen, Z. Li
    SLAC, Menlo Park, California
  • M. Dohlus, I. Zagorodnov
    DESY, Hamburg
  • E. Gjonaj, T. Weiland
    TEMF, Darmstadt
  • I. G. Gonin, A. Lunin, N. Solyak, V. P. Yakovlev
    Fermilab, Batavia, Illinois
  In a future linear collider, such as the International Linear Collider (ILC), trains of high current, low emittance bunches will be accelerated in a linac before colliding at the interaction point. Asymmetries in the accelerating cavities of the linac will generate asymmetries in the fields that will kick the beam and tend to degrade the beam emittance and thus the collider performance. In the main linac of the ILC, which is filled with TESLA-type superconducting cavities, it is the fundamental and higher mode couplers that are asymmetric and thus the source of such kicks. The kicks are of two types: one, due to (the asymmetries in) the fundamental RF fields and the other, due to transverse wakefields that are generated even when the beam is on axis. For the ILC configuration we numerically and analytically study both types of kicks and their effect on beam emittance. For the wakefield effect this is quite challenging since the bunches are very short (rms length of 300 microns), the cavity is very long (~1 m), and the distance to steady-state is even longer (~6 m). Finally, we study changes in the coupler design that can greatly reduce the effect.  
 
TUPP020 Analysis of Collective Effects at the Diamond Storage Ring single-bunch, simulation, collective-effects, storage-ring 1574
 
  • R. Bartolini, C. Christou, R. T. Fielder, M. Jensen, A. F.D. Morgan, S. A. Pande, G. Rehm, C. A. Thomas
    Diamond, Oxfordshire
  The Diamond storage ring has achieved its nominal operating current of 300 mA in multi-bunch mode and up to 10 mA in single bunch mode. Several collective instabilities have been observed and their dependence on machine parameters such as chromaticities, RF voltage and fill pattern have been investigated. We report here the analysis of the observed current thresholds and rise times of the instabilities compared with analytical estimates and tracking simulations. We also present the results of the MAFIA simulations performed with the aim of understanding the main contribution to the impedance of the ring and establishing a machine impedance database.  
 
TUPP022 Measurements of Broad Band Impedance Related Longitudinal Properties of Electron Bunches at DELTA single-bunch, undulator, synchrotron, klystron 1577
 
  • R. Burek, H. Huck, G. Schmidt, T. Weis, K. Wille
    DELTA, Dortmund
  DELTA is a 1.5 GeV synchrotron light source which can be operated also at 550 MeV for FEL experiments. Due to interactions with the vacuum chamber, the beam induces wake fields, which act back on the beam and result in a disturbed bunch profile because of potential well distortion and turbulent bunch lengthening. These interactions limit the obtainable bunch length and achievable peak current and therefore strongly affect the FEL-operation. Recent results obtained by streak camera measurements have shown that for short bunches with maximum bunch lengths of 40 ps the longitudinal broad band impedance has to be scaled (SPEAR-scaling) to explain the measurements. The broad band impedance fits well to impedance measurements and calculations performed throughout the last years. The energy spread related to the bunch lengthening has been measured by analysing the undulator spectrum.  
 
TUPP025 Preliminary Impedance Budget for the TPS Storage Ring storage-ring, single-bunch, vacuum, coupling 1586
 
  • A. Rusanov
    NSRRC, Hsinchu
  Taiwan Photon Source (TPS) is a new third generation low-emittance synchrotron storage ring which will be built at the present site of the NSRRC in Hsinchu, Taiwan. Preliminary results of the ongoing impedance studies of the TPS are presented in this paper. The overall impedance of the vacuum chamber has been evaluated with focus on the longitudinal broad-band impedance, which can lead to bunch lengthening and microwave instability. Wakepotentials and impedances produced by each component of the storage ring have been evaluated by using 3D electromagnetic code GdfidL. Then longitudinal loss factor, longitudinal broad-band impedance and transverse kick factors were computed. Results are summarized in the table. Numerically obtained data is compared to analytical results for simplified geometries of the vacuum chamber components.  
 
TUPP026 Impedance of Ultrarelativistic Charged Distributions in Tapering Geometries vacuum, simulation 1589
 
  • D. A. Burton, D. C. Christie, R. W. Tucker
    Lancaster University, Lancaster
  We develop a scheme for obtaining the impedance, at any frequency, of a gradually tapered geometry of arbitrary cross-section containing a bunch of arbitrary profile travelling at the speed of light parallel to the axis of the taper. Coordinate-free expressions for Maxwell's equations are 2+2-split in a coordinate system adapted to the particle beam and the taper and, using an asymptotic expansion for a gradual taper, a coupled hierarchy of Poisson equations are obtained. Applications of the scheme are presented.  
 
TUPP028 Bunch Length and Impedance Measurements at SPEAR3 single-bunch, lattice, storage-ring, coupling 1595
 
  • W. J. Corbett, W. X. Cheng, A. S. Fisher, X. Huang
    SLAC, Menlo Park, California
  A series of bunch length measurements have been made for different lattice configurations in SPEAR3 as a function of single-bunch current. The lattices include achromatic optics, low-emittance optics and short-bunch, low-momentum compaction optics (low-alpha). The streak-camera data clearly demonstrates effects of both resistive and reactive chamber impedance and shows levels of microwave instability threshold. In the low-alpha mode, signs of bunch length ‘bursting’ were observed. Fitted bunch-profile data, impedance calculations and bursting data are presented.  
 
TUPP029 Beam Coupling Impedance Measurement and Mitigation for a TOTEM Roman Pot resonance, insertion, coupling, vacuum 1598
 
  • M. Deile, F. Caspers, T. Kroyer, M. Oriunno, E. Radermacher, A. Soter
    CERN, Geneva
  • F. Roncarolo
    UMAN, Manchester
  The longitudinal and transverse beam coupling impedance of the first final TOTEM Roman Pot unit has been measured in the laboratory with the wire method. For the evaluation of transverse impedance the wire position has been kept constant, and the insertions of the RP were moved asymmetrically. With the original configuration of the RP, resonances with fairly high Q values were observed. In order to mitigate this problem, RF-absorbing ferrite plates were mounted in appropriate locations. As a result, all resonances were sufficiently damped to meet the stringent LHC beam coupling impedance requirements.  
 
TUPP035 Analysis of Intensity Instability Threshold at Transition in RHIC octupole, emittance, electron, coupling 1616
 
  • W. Fischer, I. Blackler, M. Blaskiewicz, P. Cameron, C. Montag, V. Ptitsyn, T. Roser
    BNL, Upton, Long Island, New York
  The beam intensity of ion beams in RHIC is limited by a fast transverse instability at transition, driven by the machine impedance and electron clouds. For gold and deuteron beams we analyze the dependence of the instability threshold on beam and machine parameters from recent operational data and dedicated experiments. We fit the machine impedance to the experimental data.  
 
TUPP037 Impedance and Instabilities for the ALBA Storage Ring damping, synchrotron, vacuum, storage-ring 1622
 
  • T. F. Günzel, F. Pérez
    ALBA, Bellaterra
  The geometrical impedance in all 3 planes for most of the vacuum chamber elements of the ALBA storage ring was computed with the 3D-solver GdfidL. Optimisation of some element geometries was carried out in order to reduce dissipative losses and in general the impedance. Resistive wall impedance was calculated analytically. The thresholds of various instabilities were determined on the basis of analytically formulated threshold criteria. The most important are a HOM-driven longitudinal multibunch instability and the transverse resistive wall instability. It is proposed to combat the first one by Landau damping using partial filling and the second one by a transverse feedback system.  
 
TUPP038 On the Longitudinal Coupling Impedance and Transmission Coefficient from Uniform and Hollow Ring Sources space-charge, coupling, synchrotron, electromagnetic-fields 1625
 
  • A. M. Al-Khateeb, O. Boine-Frankenheim, R. W. Hasse
    GSI, Darmstadt
  • J. M. Shobaki
    Yarmouk, Irbid
  The longitudinal coupling impedance and the transmission coefficient resulting from a thin ring and from a uniform disk are obtained analytically for a resistive cylindrical beam-pipe of finite wall thickness. The impedances are derived and then compared with the well known corresponding expression for perturbations on a uniform, coasting beam. The transmission coefficients from both sources are found to be exactly the same. Differences do appear in the expressions for the electromagnetic fields within the beam region, and therefore leading to different coupling impedances. By applying the results to parameters relevant for the SIS-18 synchrotron at GSI, it is found that the formula from the ring source underestimates the space-charge impedance at all beam energies and it shows a noticeable deviation from the disk formula for all frequencies. Although their mathematical expressions are different, resistive-wall impedances from the two sources are found to be numerically equal. The space-charge impedances become equal asymptotically only in the so called ultra-relativistic limit.

A. Al-Khateeb is on leave from Yarmouk University, Irbid, Jordan

 
 
TUPP043 Computational Beam Dynamics Studies of Collective Instabilities Observed in SNS proton, simulation, electron, kicker 1640
 
  • J. A. Holmes, S. M. Cousineau, V. V. Danilov, A. P. Shishlo
    ORNL, Oak Ridge, Tennessee
  • L. K. Jain
    UW/Physics, Waterloo, Ontario
  During the commissioning and early operation of the Spallation Neutron Source, some physcics shifts were set aside for high intensity stability studies. Under certain, especially contrived conditions, a number of beam instabilities were induced. These included both electron cloud and ring impedance driven phenomena. In this paper we apply both simple analytic models and the ORBIT Code to the description and simulation of these observed instabilities.  
 
TUPP051 Coupling Impedance of DAΦNE Upgraded Vacuum Chamber vacuum, coupling, electron, simulation 1661
 
  • F. Marcellini, D. Alesini, P. Raimondi, G. Sensolini, B. Spataro, A. Stella, S. Tomassini, M. Zobov
    INFN/LNF, Frascati (Roma)
  The DAΦNE Phi-factory at INFN LNF has been ugraded in the second half of 2007 with a scope to test a recently proposed scheme of crab waist collisions. The vacuum chamber of the collider has been substantially modified: two new low impedance interaction regions have been designed and installed, the new stripline injection kickers have been implemented, the old bellows have been substituted by the new ones and all ion clearing electrodes have been removed. In the paper we present the machine impedance study of these new vacuum chamber components and compare bunch lengthening measurements in the modified DAΦNE with simulation results.  
 
TUPP053 Radiolocation of a HOM Source in the PEP-II Rings vacuum, single-bunch, coupling, luminosity 1664
 
  • A. Novokhatski, J. Seeman, M. K. Sullivan
    SLAC, Menlo Park, California
  A signal from the antenna situated in the LER (Low Energy Ring) helped to find a broken shielded bellows in the HER (High Energy Ring) during a single HER bunch operation.  
 
TUPP058 Impedance Estimation of Diamond Cavities simulation, storage-ring, vacuum, resonance 1673
 
  • S. A. Pande, R. T. Fielder, M. Jensen
    Diamond, Oxfordshire
  • R. Bartolini
    JAI, Oxford
  The RF straight section of the Diamond storage ring presently consist of two CESR type SCRF cavities with a provision to install a third cavity in the future. The cavities are equipped with HOM loads and are joined to the adjacent storage ring beam pipe using tapered transitions. The RF cavities are simulated with MAFIA, CST Studio and ABCI to estimate their contribution to the total ring impedance. We also measured the resonant frequencies and Q factors of residual HOMs in these cavities. In this paper, we present the results of our measurements and simulations which lead us to an estimation of the impedance of the RF straight.  
 
TUPP061 Comparison between Laboratory Measurements, Simulations and Analytical Predictions of the Resistive Wall Transverse Beam Impedance at Low Frequencies simulation, coupling, damping, luminosity 1679
 
  • F. Roncarolo
    UMAN, Manchester
  • F. Caspers, T. Kroyer, E. Métral
    CERN, Geneva
  • B. Salvant
    EPFL, Lausanne
  The prediction of the resistive wall transverse beam impedance at the first unstable betatron line (8 kHz) of the CERN Large Hadron Collider (LHC) is of paramount importance for understanding and controlling the related coupled-bunch instability. Until now only novel analytical formulas were available at this frequency. Recently, laboratory measurements and numerical simulations were performed to crosscheck the analytical predictions. The experimental results based on the measurement of the variation of a probe coil inductance in the presence of i) sample graphite plates, ii) stand-alone LHC collimator jaws and iii) a full LHC collimator assembly are presented in detail. The measurement results are compared to both analytical theories and simulations. In addition, the consequences for the understanding of the LHC impedance are discussed.  
 
TUPP062 Beam Coupling Impedance Studies on LHC FP420 Multi-pocket Beam Pipe Prototype simulation, coupling, resonance, scattering 1682
 
  • F. Roncarolo, R. Appleby, R. M. Jones
    UMAN, Manchester
  The LHC FP420 collaboration is assessing the feasibility of installing forward proton detectors 420m from the ATLAS and/or CMS interaction points. The latest prototype of a FP420 station consists of a modified LHC beam pipe in which two pockets hosting the detectors introduce an abrupt cross-section variation of the pipe. During the FP420 proposed operation, each station is moved towards the beam as close as 3 mm (~ 10 σx). The impact on the LHC beam coupling impedance has been evaluated with a laboratory wire measurement and a suite of numerical simulations. In addition, we describe a proposed modification of the beam pipe design which minimizes the impedance of the resonances without compromising the FP420 detector signal to background ratio.  
 
TUPP063 Characterization of the ATLAS Roman Pots Beam Coupling Impedance and Mechanics vacuum, coupling, simulation, resonance 1685
 
  • F. Roncarolo, R. M. Jones
    UMAN, Manchester
  • F. Caspers, B. Di Girolamo, T. Kroyer
    CERN, Geneva
  At the LHC, four Roman Pot (RP) type detectors will be installed on both sides of the ATLAS experiment with the aim of measuring elastic scattering at very small angles and determining the absolute luminosity at the interaction point. During dedicated LHC runs, the detectors will be positioned at about 1 mm from the nominal beam orbit. Numerical simulations and laboratory measurements were carried out to characterize the RP impact on the total LHC beam coupling impedance. The measurement results assess the effectiveness of RF-absorbing ferrite plates that have been mounted in convenient locations in order to damp high Q resonances of the RP structure. In addition, we review the RP mechanics emphasizing the accuracy and reproducibility of the positioning system.  
 
TUPP066 CERN SPS Impedance in 2007 kicker, quadrupole, shielding, synchrotron 1691
 
  • E. Métral, G. Arduini, T. Bohl, H. Burkhardt, F. Caspers, H. Damerau, T. Kroyer, H. Medina, G. Rumolo, M. Schokker, E. N. Shaposhnikova, J. Tuckmantel
    CERN, Geneva
  • R. Calaga
    BNL, Upton, Long Island, New York
  • B. Salvant
    EPFL, Lausanne
  • B. Spataro
    INFN/LNF, Frascati (Roma)
  Each year several measurements of the beam coupling impedance are performed in both longitudinal and transverse planes of the CERN Super Proton Synchrotron to keep track of its evolution. In parallel, after the extensive and successful campaign of identification, classification and cure of the possible sources of (mainly longitudinal) impedance between 1998 and 2001, a new campaign (essentially for the transverse impedance this time) has started few years ago, in view of the operation of the SPS with higher intensity for the LHC luminosity upgrade. The present paper summarizes the results obtained from the measurements performed over the last few years and compares them to our predictions. In particular, it reveals that the longitudinal impedance is reasonably well understood and the main contributors have already been identified. However, the situation is quite different in the transverse plane: albeit the relative evolution of the transverse impedance over the last few years can be well explained by the introduction of the nine MKE kickers necessary for beam extraction towards the LHC, significant contributors to the SPS transverse impedance have not been identified yet.  
 
TUPP067 Transverse Mode-coupling Instability in the CERN SPS: Comparing MOSES Analytical Calculations and HEADTAIL Simulations with Experiments in the SPS simulation, kicker, injection, coupling 1694
 
  • B. Salvant
    EPFL, Lausanne
  • G. Arduini, E. Métral, G. Papotti, G. Rumolo, R. J. Steinhagen, R. Tomas
    CERN, Geneva
  • R. Calaga
    BNL, Upton, Long Island, New York
  Since 2003, single bunches of protons with high intensity (1.2·1011 protons) and low longitudinal emittance (0.2 eVs) have been observed to suffer from heavy losses in less than one synchrotron period after injection at 26 GeV/c in the CERN Super Proton Synchrotron (SPS) when the vertical chromaticity is corrected. Understanding the mechanisms underlying this instability is crucial to assess the feasibility of an anticipated upgrade of the SPS, which requires bunches of 4·1011 protons. Analytical calculations from MOSES and macroparticle tracking simulations using HEADTAIL with an SPS transverse impedance modelled as a broadband resonator had already qualitatively and quantitatively agreed in predicting the intensity threshold of a fast instability. A sensitive frequency analysis of the HEADTAIL simulations output was then done using SUSSIX, and brought to light the fine structure of the mode spectrum of the bunch coherent motion. A coupling between the azimuthal modes -2 and -3 was clearly observed to be the reason for this fast instability. The aim of the present paper is to compare the HEADTAIL simulations with dedicated measurements performed in the SPS in 2007.  
 
TUPP068 Bench Measurements of the Low Frequency Transverse Impedance of the CERN LHC Beam Vacuum Interconnects with RF Contacts vacuum, cryogenics, coupling, betatron 1697
 
  • B. Salvant
    EPFL, Lausanne
  • F. Caspers, E. Métral
    CERN, Geneva
  • F. Roncarolo
    UMAN, Manchester
  The low frequency longitudinal and transverse impedances of the CERN Large Hadron Collider (LHC) have to be specifically minimized to prevent the onset of coherent instabilities. The LHC beam vacuum interconnects were designed as Plug In Modules (PIMs) with RF contacts to reduce their coupling impedances, but the resulting contact resistance is a concern, as this effect is difficult to estimate. High sensitivity measurements of the transverse impedance of a PIM at low frequency using a coil probe are presented. In particular, the increase of the transverse impedance of the PIM when it is elongated to its operating position is discussed in detail. Finally, the issue of non-conforming contact resistance is also addressed.  
 
TUPP073 Bench-top Impedance Measurements for a Rotatable Copper Collimator for the LHC Phase II Collimation Upgrade vacuum, collimation, simulation, target 1703
 
  • J. C. Smith, K. L.F. Bane, J. E. Doyle, L. Keller, S. A. Lundgren, T. W. Markiewicz, C.-K. Ng, L. Xiao
    SLAC, Menlo Park, California
  The Phase II upgrade to the LHC collimation system calls for complementing the 30 high robust Phase I graphite collimators with 30 high Z, low impedance Phase II collimators. The design for the collimation upgrade has not been finalized. One option is to use metallic rotatable collimators and this design will be discussed here. Simulations have been performed in MAFIA to study both the resistive wall and geometric impedance contributions of our rotatable collimator design. Benchtop stretched coil probe impedance measurements have also been performed on prototype components to directly measure the low frequency impedance contributions. The design also calls for an RF contact interface at the jaw end. This contact resistance must be a small fraction of a milliohm in order to limit transverse impedance. DC resistance measurements in a custom built test chamber have been performed to test the performance of various metal pairs and surface coatings.  
 
TUPP074 A New RF Shielded Bellows for the DAΦNE Upgrade shielding, coupling, simulation, storage-ring 1706
 
  • S. Tomassini, F. Marcellini, P. Raimondi, G. Sensolini
    INFN/LNF, Frascati (Roma)
  A new RF shielded bellows, using the technology of omega shaped strip of beryllium copper material, has been developed and tested on the DAΦNE Upgrade*. The RF omega shield is composed by many Be-Cu strips held by an external floating ring**. Thermal power loss on strips can be easily extracted and dissipated allowing high beam current operation. Leakage of beam induced e.m. fields through the RF shield is almost suppressed. Twenty omega bellows were manufactured and installed in the DAΦNE storage rings and showed good properties up to a stored beam current of 700 mA.

*DAΦNE upgrade: A New magnetic and mechanical layout. PAC07. pp. 1466-1468, Albuquerque.
**Design and E. M. Analysis of the New DAΦNE Interaction Region. PAC07, Albuquerque, pp 3988.

 
 
TUPP075 Numerical Studies of Resistive Wall Effects vacuum, electromagnetic-fields, emittance, electron 1709
 
  • A. V. Tsakanian
    Uni HH, Hamburg
  • M. Dohlus, I. Zagorodnov
    DESY, Hamburg
  In this paper we describe a new numerical code to calculate wakefields of resistive wall geometries. Our code is based on conformal implicit scheme. It allows to estimate wakefields of very short bunches taking into account transitive effects neglected in the European XFEL impedance budget so far.  
 
TUPP076 Longitudinal and Transverse Impedances of XFEL Kicker Vacuum Chamber vacuum, kicker, dipole, resonance 1712
 
  • A. V. Tsakanian, J. Rossbach
    Uni HH, Hamburg
  • M. Ivanyan
    CANDLE, Yerevan
  In European XFEL project beam delivery system the kicker magnet vacuum chamber design is composed of the ceramic pipe coated with Titanium Stabilized High Gradient Steel. In this paper the results of the study for the longitudinal and transverse impedances for such a laminated vacuum chamber are presented. The field matching technique is used to calculate the vacuum chamber impedances. The loss and kick factors are given.  
 
TUPP081 Longitudinal Wakefields and Impedance in the CSNS/RCS extraction, injection, kicker, vacuum 1718
 
  • N. Wang, Q. Qin
    IHEP Beijing, Beijing
  With the more general expressions developed for the wakefield generated by nonrelativistic beam*, the impedances of some main vacuum parts of the Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) are calculated and compared with the relativistic case. An impedance model is then proposed for the ring. With this impedance model, beam instabilities in the CSNS/RCS are investigated.

*N. Wang and Q. Qin, Phys. Rev. ST Accel. Beams 10, 111003 (2007)

 
 
TUPP082 Longitudinal Stability of Flat Bunches with Space-charge or Inductive Impedance damping, synchrotron, space-charge, dipole 1721
 
  • F. Zimmermann
    CERN, Geneva
  • I. Santiago Gonzalez
    University of the Basque Country, Bilbao
  We study the loss of Landau damping for the longitudinal plane via the ''Sacherer formalism''. Stability limits are calculated for several longitudinal beam distributions, in particular for two types of flat bunches, which could be of interest to the LHC upgrade. The resulting Landau stability diagrams are computed and displayed for different azimuthal modes. A general recipe is given for calculating the threshold intensity in the case of a capacitive impedance below transition or, equivalently, for a purely inductive impedance above transition. Specific results are finally presented for the case of the PS Booster, as an example of space-charge impedance below transition, and for the SPS, as an example of inductive impedance above transition.  
 
TUPP095 Computation of Resistive Wall Wakefields with the PBCI Code simulation, resonance, linear-collider, collider 1753
 
  • T. Lau, E. Gjonaj, T. Weiland
    TEMF, Darmstadt
  • R. Maekinen
    TUT, Tampere
  Both geometric disturbances and resistive wall loss of accelerator cavities contribute to the impedance causing the beam to lose energy. Impedance due to arbitrary three-dimensional (3-D) geometries can be computed with the Parallel Beam Cavity Interaction (PBCI), a parallelized, 3D-wakefield code. However, the contribution of wall loss is often significant. The contribution of this work is to incorporate resistive wall loss into 3-D time-domain simulation. Surface-impedance concept is used to consider wide-band skin-effect loss of metal. In theory, the proposed approach can be extended to consider high-frequency phenomena such as frequency-dependent conductivity of metal and anomalous skin effect.  
 
WEPC006 Beam Lifetime and Collective Effects in Taiwan Photon Source ion, insertion, insertion-device, vacuum 1992
 
  • P. J. Chou, H.-P. Chang, C.-C. Kuo, W. T. Liu, H.-J. Tsai
    NSRRC, Hsinchu
  The design of Taiwan Photon Source (TPS) has a natural emittance less than 2 nm-rad and low emittance coupling. The nominal rms bunch length is less than 3 mm. Several small-gap undulators are planned to provide x-ray photon beam with extremely high brightness. The vertical gap of these undulators are in the range of 5-7 mm. The TPS ring will be operated at top-up mode with high beam current. Various collective effects due to high beam current are investigated. Impacts of small-gap undulators to the beam lifetime are carefully studied. The results of theoretical analysis are presented. Proposals to overcome deleterious effects due to high beam current and small-gap undulators are also discussed.  
 
WEPC143 System for Local Magnetic Field Measurement System Based on a Coil with Three Square Millimeter undulator, multipole, alignment 2344
 
  • J. F. Citadini, R. Basilio, M. Potye, G. Tosin
    LNLS, Campinas
  We present a magnetic field measurement system based on a rotating coil with 3mm2 active area and approximately 500 turns to measure local magnetic field. The structure of a coil is not so complex, simplifying the evaluation of its sources of errors. The steps used to build the coil are shown as well as the performance of the measurement system. The calibration of the coil was made against a magnetic field generated by a solenoid with very well determined geometry.  
 
WEPP001 Energy Loss of Coasting Gold Ions and Deutrons in RHIC synchrotron, radiation, synchrotron-radiation, ion 2518
 
  • N. P. Abreu, M. Blaskiewicz, K. A. Brown, J. J. Butler, W. Fischer, M. Harvey, S. Tepikian
    BNL, Upton, Long Island, New York
  • H. Burkhardt
    CERN, Geneva
  The total energy loss of coasting gold ion beams was measured at RHIC at two energies, corresponding to a gamma of 75.2 and 107.4. We describe the experiment and observations and compare the measured total energy loss with expectations from ionization losses at the residual gas, the energy loss due to impedance and synchrotron radiation. We find that the measured energy losses are below what is expected from free space synchrotron radiation. We believe that this shows evidence for suppression of synchrotron radiation which is cut off at long wavelength by the presence of the conducting beam pipe.  
 
WEPP007 Crab Compensation for LHC Beams damping, optics, collimation, luminosity 2536
 
  • R. Calaga
    BNL, Upton, Long Island, New York
  • Y. Sun, R. Tomas, F. Zimmermann
    CERN, Geneva
  An R&D program to establish a road map for the installation of crab cavities in the LHC is rapidly advancing. Both local and global crab schemes are under investigation to develop cavities that will be compatible with LHC optics and meet aperture requirements. The design of a prototype TM110 cavity and pertinent RF requirements including impedance estimates and damping are discussed. Some alternate cavity designs are also explored. The required optics modifications to accommodate the crab cavities and some particle stability studies are presented.  
 
WEPP041 High-current Effects in the PEP-II Storage Rings kicker, vacuum, feedback, ion 2611
 
  • U. Wienands, W. X. Cheng, W. S. Colocho, S. DeBarger, F.-J. Decker, S. Ecklund, A. S. Fisher, D. Kharakh, A. Krasnykh, A. Novokhatski, M. K. Sullivan
    SLAC, Menlo Park, California
  High beam currents, 2A(HER) & 3A(LER), in PEP-II has been a challenge for the vacuum system. For the ~1 cm long bunches peak currents reach 50 A. Thus modest impedances can give rise to voltage spikes and discharges. A weakness was uncovered during Run 6: rf seals at the "flex flanges" that join the HER arc dipole and quadrupole chambers became a source of an increasing number of HER beam aborts. Vacuum activity was seen and thermal sensors on these flanges saw temperature spikes. Inspection of the seals found arcing and melting, prompting us to replace all of these seals with an improved design using Inconel instead of GlidCop fingers. We believe the GlidCop fingers do not maintain elasticity and hence can not follow chamber motion due to thermal effects. The Run 7 startup confirmed the success of this repair. However, high bunch current in the LER caused breakdown in a LER kicker. This limited the LER bunch current to about 1 mA. Inspection revealed damage to one of the recently added Macor pins that help support the electrodes. Failure analysis revealed heating of the pin & post-facto modeling shows high fields coming from a combination of HOM impedance and high peak currents.  
 
WEPP071 Preliminary Exploratory Study of Different Phase II Collimators simulation, collimation, radiation, luminosity 2683
 
  • L. Lari, R. W. Assmann, A. Bertarelli, C. Bracco, M. Brugger, F. Cerutti, A. Dallocchio, A. Ferrari, M. Mauri, S. Roesler, L. Sarchiapone, V. Vlachoudis
    CERN, Geneva
  • J. E. Doyle, L. Keller, S. A. Lundgren, T. W. Markiewicz, J. C. Smith
    SLAC, Menlo Park, California
  • L. Lari
    EPFL, Lausanne
  The LHC collimation system is installed and commissioned in different phases, following the natural evolution of the LHC performance. To improve cleaning efficiency towards the end of the low beta squeeze at 7TeV, and in stable physics conditions, it is foreseen to complement the 30 highly robust Phase I secondary collimators with low impedance Phase II collimators. At this stage, their design is not yet finalized. Possible options include metallic collimators, graphite jaws with a movable metallic foil, or collimators with metallic rotating jaws. As part of the evaluation of the different designs, the FLUKA Monte Carlo code is extensively used for calculating energy deposition and studying material damage and activation. This report outlines the simulation approach and defines the critical quantities involved.  
 
WEPP083 Development of an X-band Hybrid Dielectric-iris-loaded Accelerator electron, gun, longitudinal-dynamics, linac 2713
 
  • X. D. He, S. Dong, G. Feng, Y. J. Pei, C.-F. Wu
    USTC/NSRL, Hefei, Anhui
  A compact x-band hybrid dielectric-iris-loaded travelling-wave linac with constant impendence structure has been designed. By adjusting the values of and the numbers of cells, the beam energy of 29 MeV, the capture efficiency about 50% and the energy spread about with the beam current being 70 mA and the electric gun voltage being 50KeV are obtained through longitudinal dynamics calculation. The length of accelerator tube is 1.12m . The maximum accelerating gradient is less than 45MV/m. By using electromagnetic code such as MAFIA, the attenuation per unit length of structure , the shunt impedance , the quality factor Q, the group velocity and the phase velocity are got by optimizing the dimensions of the cavities.  
 
WEPP097 Simulation of Wakefield Effect in ILC IR Chamber simulation, luminosity, linac, collider 2743
 
  • S. Pei, T. O. Raubenheimer, A. Seryi, J. C. Smith
    SLAC, Menlo Park, California
  To achieve super high luminosity, high current beams with very short bunch length are needed, which carry high intensity EM fields. For ILC, two bunch trains with bunch length of 300μm and bunch charge of 3.2nC are needed to collide at the IR to achieve the ILC luminosity goals. When the 300μm bunches pass through the IR chamber, wakefields will be excited, which will cause HOM power flowing through the IR chamber beam pipe to the final doublets due to the high frequency characteristic of the induced wakefields. Since superconducting technology is adopted for the final doublets of ILC BDS, whose operation stability might be affected by the HOM power produced at the IR chamber, quench might happen. In this paper, we did some analytical estimation and numerical simulation on the wakefield effects in ILC IR chamber.  
 
WEPP125 Analysis of the Vertical Beam Instability in CTF3 Combiner Ring and New RF Deflector Design controls, resonance, emittance, simulation 2791
 
  • D. Alesini, C. Biscari, A. Ghigo, F. Marcellini
    INFN/LNF, Frascati (Roma)
  In the last CTF3 run (November 2007) a vertical beam instability has been found in the Combiner Ring during operation. Possible sources of the instability are the vertical deflecting modes excited by the beam in the RF deflectors. In the first part of the paper we illustrate the results of the beam dynamics analysis obtained by a dedicated tracking code that allows including the induced transverse wake field and the multi-bunch multi-passage effects. To reduce the effects of such vertical trapped modes, the RF deflectors have been modified and two new deflectors have been designed. They have been made in aluminium and have two more ports in the input and output coupler cells to absorb the beam induced field on the vertical modes. The design of the new deflectors and the RF measurements are then presented in the paper.  
 
WEPP166 Comparison of Collimator Wakefields Formulae dipole, quadrupole, electron, vacuum 2877
 
  • A. M. Toader, R. J. Barlow
    UMAN, Manchester
  There is an extensive literature on transverse wakefield kick factors in collimators. We present a compendium of the formulae and discuss their agreement and disagreement with each other and with experimental results.  
 
THXM03 Status of the European HOM Damped Normal Conducting Cavity vacuum, brilliance, simulation, damping 2932
 
  • E. Weihreter
    BESSY GmbH, Berlin
  Cavities with damped higher order modes (HOMs) are an essential ingredient for state of the art storage ring based high brilliance synchrotron radiation sources to avoid degradation of the beam quality due to coupled bunch instabilities. Starting with a review of the concepts of existing HOM damped cavities the status of a normal conducting 500 MHz cavity is presented which has been developed for low and medium energy high brilliance synchrotron light sources within the frame of an EC funded collaboration. The results of numerical simulations and of low power impedance measurements are reported together with conceptional improvements, expected performance, and first operational achievements in the Metrology Light Source in Berlin.  
slides icon Slides  
 
THPC124 The Manufacturing and Tests of The New Vertical Feedback Stripline at Soleil feedback, vacuum, simulation, kicker 3275
 
  • C. Mariette, J.-C. Denard, R. Nagaoka
    SOLEIL, Gif-sur-Yvette
  This paper describes the development of the kicker striplines for the bunch-by-bunch transverse instability feedback system at Soleil. A careful design of the striplines and of their vacuum feedthroughs was aimed at maximizing the effectiveness of the excitation power and minimizing the power taken from the beam. The excitation effectiveness improves with the shunt impedance. But, simultaneously, the beam impedance should be made as small as possible. We also found useful to estimate the temperature of the feedthroughs at high beam currents, especially on the ceramic-to-metal seals. We also report on the difficulties encountered with obtaining good feedthroughs.  
 
THPC125 Modeling and Simulation of the Longitudinal Beam Dynamics-RF Station Interaction in the LHC Rings simulation, klystron, feedback, controls 3278
 
  • T. Mastorides, J. D. Fox, C. H. Rivetta, D. Van Winkle
    SLAC, Menlo Park, California
  • P. Baudrenghien, J. Tuckmantel
    CERN, Geneva
  A non-linear time-domain simulation has been developed to study the interaction between longitudinal beam dynamics and RF stations in the LHC rings. The motivation for this tool is to study the effect of RF station noise, impedance, and perturbations on the beam life and longitudinal emittance. It will be also used to determine optimal LLRF configurations, to study system sensitivity on various parameters, and to define the operational and technology limits. It allows the study of alternative LLRF implementations and control algorithms. The insight and experience gained from our PEP-II simulation is important for this work. In this paper we discuss properties of the simulation tool that will be helpful in analyzing the LHC RF system and its initial results. Partial verification of the model with data taken during the LHC RF station commissioning is presented.  
 
THPP002 EMMA RF Cavity Design and Prototype Testing at Daresbury acceleration, vacuum, kicker, electron 3374
 
  • C. D. Beard, P. A. Corlett, D. M. Dykes, P. Goudket, C. Hill, P. A. McIntosh, A. J. Moss, J. F. Orrett, J. H.P. Rogers, A. E. Wheelhouse, E. Wooldridge
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • N. Bliss
    STFC/DL, Daresbury, Warrington, Cheshire
  • A. E. Bogle, T. L. Grimm, A. A. Kolka
    Niowave, Inc., Lansing, Michigan
  At PAC’07 we discussed the design of a prototype cavity to be used on EMMA*. EMMA is a prototype non-scalling FFAG. It will contain 19 RF cavities operating at 1.3 GHz with a baseline accelerating voltage of 120 kV. A prototype cavity has been manufactured by Niowave, Inc. and we will present a discussion of its RF and mechanical design. This cavity was put through low power tests, to determine frequency, tuning range, shunt impedance and Q of the cavity; and high power tests, to confirm power handling ability, when it arrived at Daresbury Laboratory this spring. The results of these tests were compared to the simulations and a bead pull was carried out to obtain the field profile. The cavities for EMMA are likely to be powered by IOTs, these will be used for the high power tests, which will demonstrate cavity operation to the required maximum of 180 kV.

*E. Wooldridge et al. "RF Cavity Development for FFAG Application on ERLP at Daresbury," Proceedings of PAC’07, Albuquerque, NM (2007).

 
 
THPP026 IH Accelerating Structures with PMQ Focusing for Low-energy Light Ions focusing, simulation, quadrupole, ion 3428
 
  • S. S. Kurennoy, S. Konecni, J. F. O'Hara, L. Rybarcyk
    LANL, Los Alamos, New Mexico
  We are developing high-efficiency room-temperature RF accelerating structures for beam velocities in the range of a few percent of the speed of light by merging two well-known ideas: inter-digital H-mode (IH) cavities and the transverse beam focusing with permanent-magnet quadrupoles (PMQ). Combining electromagnetic 3-D modeling with beam dynamics simulations and thermal-stress analysis, we have proved that such structures provide a very efficient and practical accelerator for light-ion beams of considerable currents. The IH accelerating structures with PMQ focusing following a short RFQ can be used in the front end of ion linacs or in stand-alone applications such as a compact deuteron-beam accelerator up to the energy of a few MeV.  
 
THPP027 Heating and Stress in the LANSCE Side-coupled Linac RF Cavities coupling, linac 3431
 
  • S. S. Kurennoy, S. Konecni, J. F. O'Hara, L. Rybarcyk
    LANL, Los Alamos, New Mexico
  RF heating and related temperature distribution and stress are important problems in room-temperature accelerating cavities operating at high duty factors. To evaluate feasibility of higher duty operations of the Los Alamos Neutron Science Center (LANSCE) side-coupled linac (SCL), we have performed a combined 3-D electromagnetic (EM) and thermal-stress analysis of the SCL RF cavities. In the process, we have developed a procedure and interface for data exchange between the electromagnetic (MicroWave Studio) and engineering (COSMOS) codes for the combined EM-engineering analysis. This interface can be useful for other applications involving room-temperature accelerating cavities.  
 
THPP097 Commissioning Results of the Kicker Magnet in J-PARC RCS kicker, extraction, power-supply, proton 3590
 
  • J. Kamiya, M. Kinsho, M. Kuramochi, T. Takayanagi, T. Togashi, T. Ueno, M. Watanabe, M. Yoshimoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  Installation of the kickers in the extraction section of the RCS in J-PARC facility was completed. And they succeeded to extract the 3GeV proton beams in the first beam test. The operation parameters of the kickers agreed well with the parameters which were estimated from the magnetic field measurement and the current test of the power supplys. In this report, we summarized the results of the excitation test and the commissioning of the kicker magnet. The results of the magnetic field measurement showed the good uniformity in the wide range of the aperture. The characteristic feature of each kicker power supply was also measured precisely. Although the rise time and jitter of the output pulse have some minor variation due to the different characteristics of the thyratrons, the degree of variation was acceptably small. Combining the results of the magnetic field measurements, the relation between the charging voltage and the magnetic field was obtained for each kicker. The accelerated beam was successfully extracted at the operation parameters which were obtained from the relationship. The measurements result which was obtained by using the beam is also reported.  
 
THPP125 Performance Evaluation of the Switching Mode AC Power Supply power-supply, booster, controls, dipole 3652
 
  • C.-Y. Liu, Y.-C. Chien, H. M. Shih
    NSRRC, Hsinchu
  In order to improve the injection efficiency, the output current waveform of the AC power supplies must be great. Therefore, to ensure smooth and efficient injection of the booster ring, the phase jitter of the AC power supplies current must be less than ±4ns. A new AC power supply is constructed and employ IGBT modules operating at higher switching frequency than the old GTO-based system for the dipole magnet. This new power supply will not only improve the phase jitter but also increase the operating efficiency than the old power supply. The measured dynamic range of the of the 10 Hz sine wave current output is better than 75dB and phase jitter is less than ±4ns. The improved performance evaluation is illustrated in the paper.  
 
THPP143 Vacuum Design of the TPS Relates to the Beam Effects vacuum, electron, ion, photon 3699
 
  • G.-Y. Hsiung, C. K. Chan, C.-C. Chang, H. P. Hsueh, Z.-D. Tsai
    NSRRC, Hsinchu
  • J.-R. Chen
    NTHU, Hsinchu
  The concept of the vacuum design for the 3 GeV Taiwan Photon Source (TPS) considers several points of view which relates to the beam effects. The vacuum design of the low outgassing rate and the effective pumping configurations to obtain the lowest average pressure in the electron storage ring is to obtain the longer beam life time and the least of the ion trapping effect and the consequent problem of beam ion instability. The inner structure of the beam ducts provides the lower impedance which reduces the problems of the collective beam instability and the heating dissipation and damage to the vacuum components. The thin wall of the beam ducts and the bellows are designed for the sextupoles that offers the function of fast feedback orbit correction of the beam. The final performance of the third generation light source with low emittance will rely on the original design of vacuum systems for the electron beam. The design philosophy of the vacuum systems for the TPS will be described.  
 
FRXBGM01 Impedance Computation and Measurement in Modern Storage Rings storage-ring, simulation, kicker, single-bunch 3728
 
  • R. Nagaoka
    SOLEIL, Gif-sur-Yvette
  Recent progress in the evaluation of machine impedance and instability thresholds will be reviewed, and comparisons made between measurements and predicted impedance in recently commissioned storage rings.  
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