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resonance

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MOPC108 AGS Polarized Proton Operation in Run 8 polarization, injection, emittance, extraction 316
 
  • H. Huang, L. Ahrens, M. Bai, K. A. Brown, C. J. Gardner, J. W. Glenn, F. Lin, A. U. Luccio, W. W. MacKay, T. Roser, S. Tepikian, N. Tsoupas, K. Yip, A. Zelenski, K. Zeno
    BNL, Upton, Long Island, New York
  • H. M. Spinka, D. G. Underwood
    ANL, Argonne, Illinois
  A dual partial snake scheme has been used for AGS polarized proton operation for several years. It has provided polarized proton beams with 1.5*1011 protons per bunch and 65% polarization for the RHIC spin program. There is still residual polarization loss due to both snake resonances and horizontal resonances. Several schemes were tested in the AGS to mitigate the loss. This paper presents the experiment results and analysis.  
 
MOPC113 Head-on Beam-beam Compensation with Electron Lenses in the Relativistic Heavy Ion Collider proton, electron, emittance, simulation 328
 
  • Y. Luo, N. P. Abreu, E. N. Beebe, J. Beebe-Wang, C. Montag, M. Okamura, A. I. Pikin, G. Robert-Demolaize
    BNL, Upton, Long Island, New York
  The working points for polarized proton operation in the Relativistic Heavy Ion Collider (RHIC) are currently constrained between 2/3 and 7/10, and the beam and luminosity lifetimes are limited by head-on beam-beam effects. To further increase the bunch intensity, we propose a low energy Gaussian electron beam, or electron lens, to collide head-on with the proton beam in order to compensate the large tune shift and tune spread generated by the proton-proton collisions in 2 interaction points. In this article, outline of the RHIC head-on beam-beam compensation with e-lenses and parameters for both proton and electron beams are presented.  
 
MOPC117 Hybrid Snake Spin Resonance in RHIC lattice, sextupole, coupling, betatron 337
 
  • V. H. Ranjbar, D. T. Abell
    Tech-X, Boulder, Colorado
  • M. Bai, A. U. Luccio
    BNL, Upton, Long Island, New York
  Simulations reveal a potential polarization loss during low beta squeeze. This depolarization appears to be driven by a spin tune modulation caused by spin precession through the strong low beta quads due to the vertical fields. The modulation of the spin tune introduces an additional snake resonance condition at νs0 ± n νx - νz l = integer which while the same numerology as the well known sextupole resonance, can operate in the absence of sextupole elements.  
 
MOPC120 J-PARC RCS Non-linear Frequency Sweep Analysis controls, impedance, 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.  
 
MOPC130 Space Charge Loss Mechanisms Associated with Half Integer Resonance on the ISIS Synchrotron simulation, emittance, space-charge, synchrotron 373
 
  • C. M. Warsop, D. J. Adams, B. G. Pine
    STFC/RAL/ISIS, Chilton, Didcot, Oxon
  ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on a 50 Hz proton synchrotron, which accelerates ~3·1013 ppp from 70 to 800 MeV, corresponding to mean beam powers of 0.2 MW. Beam loss limits operational intensity, and a main contributing mechanism is the action of half integer resonance under high space charge. Progress on studies using particle in cell simulations to explore the evolution of envelope motion, associated 2:1 parametric halo, growth of particles from the outer core, and effects of dispersion and longitudinal motion is presented. Comparisons are made with relevant theoretical models and progress on experimental studies summarised, presently emphasising the simplified 2D coasting beam case.  
 
MOPC139 Refractory Ovens for ECR Ion Sources and Their Scaling plasma, ion, ion-source, electron 397
 
  • M. Cavenago, A. Galatà, M. Sattin
    INFN/LNL, Legnaro, Padova
  • T. Kulevoy, S. Petrenko
    ITEP, Moscow
  The radiofrequency (rf) oven can be used as a metal vapour injector for Electron Cyclotron Resonance ion source; the application to high temperature boiling metals (like Cr, Ti and V) was recently demonstrated. Duration and reusability of oven parts were excellent, since crucible only need to be maintained at a temperature Ts larger than other parts; for vanadium case, achieved Ts was up to 2300 K with about 280 W of rf power, with the present design and size, tailored to our 14.4 GHz ECRIS. Optimization for different sources is discussed, and modern design tools are reviewed. Materials, more than rf power coupling, emerge as ultimate limits. Comparisons of results with resistive oven and sputter probes and with different metals are briefly reported.  
 
MOPP061 Non Linear Dynamics Study of the CLIC Damping Rings Using Sympletic Integrators damping, sextupole, wiggler, emittance 682
 
  • Y. Papaphilippou
    CERN, Geneva
  • Ch. Skokos
    IMCCE, Paris
  A class of symplectic integrators with positive steps (SABA2) is applied to investigate the non-linear dynamics of the CLIC damping rings. The detrimental effect of the chromaticity sextupoles is studied using frequency and diffusion maps and verified with MADX ptc dynamic aperture tracking. The reduction of the dynamic aperture for off-momentum particles is also investigated.  
 
MOPP063 A New Chicane Experiment in PEP-II to Test Mitigations of the Electron Cloud Effect for Linear Colliders electron, dipole, simulation, vacuum 688
 
  • M. T.F. Pivi, D. Arnett, F. D. Cooper, D. Kharakh, F. King, R. E. Kirby, B. Kuekan, J. J. Lipari, M. Munro, J. S.T. Ng, J. Olszewski, T. O. Raubenheimer, J. Seeman, B. Smith, C. M. Spencer, L. Wang, W. Wittmer
    SLAC, Menlo Park, California
  • C. M. Celata, M. A. Furman
    LBNL, Berkeley, California
  Beam instability caused by the electron cloud has been observed in positron and proton storage rings and it is expected to be a limiting factor in the performance of the positron Damping Ring (DR) of future Linear Colliders such as ILC and CLIC. Possible remedies for the electron cloud effect include thin-film coatings, surface conditioning, antechamber, clearing electrodes, and chamber with grooves or slots. The effect is expected to be particularly severe in magnetic field regions. To test this and possible mitigation methods, we have installed a new 4-dipole chicane experiment in the PEP-II Low Energy Ring (LER). We have also installed test chambers in straight field free regions. The associated chamber consists of bare aluminum and TiN-coated inner surface sections. Each section is instrumented with arrays of readout electrodes and retarding grids. Installation of a grooved chamber is also planned. In this paper, we describe the ongoing R&D effort at SLAC to reduce the electron cloud effect in linear colliders. We present the design of the chicane, the chambers and diagnostics, as well as the experimental results obtained.  
 
MOPP074 Improvement of an S-band RF-gun cavity with a Cs-Te Photo-cathode cathode, electron, impedance, scattering 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.  
 
MOPP094 Reduction of Q-loss-effects in Ferrite-loaded Cavities damping, synchrotron, vacuum 772
 
  • H. G. Koenig, S. Schaefer
    GSI, Darmstadt
  Accelerating cavities loaded with Ni-Zn ferrites have been widely used in synchrotrons for many years. So far their performance is significantly limited by the so-called high-loss-effect (HLE) or quality-loss-effect (QLE). After some milliseconds, this effect leads to a sudden drop of the resonator's voltage namely under the following conditions: fixed frequencies with RF-power above a specific threshold level and a parallel DC-biasing. The mechanism of this unwanted loss has not been fully understood yet. Now a simple method has been found to work against this effect with the aid of mechanical damping of surface waves. For small samples of ferrites the QLE is fully suppressed by using a rubber belt around the circumference or by covering the surface with a thin layer of hot-melt adhesive. We were able to show that similar methods applied to full size rings lead to a significant increase of the onset voltage of the QLE. Most of the existing ferrite loaded accelerating cavities with QLE-limitations can be increased in their accelerating voltage by the above-mentioned modification.  
 
MOPP096 C-band Linac Optimization for a Race-track Microtron linac, coupling, simulation, impedance 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.  
 
MOPP100 Performance of Compact Electron Injector on Evanescent Oscillations electron, gun, coupling, cathode 790
 
  • V. V. Mytrochenko, M. I. Ayzatskiy, I. V. Khodak, K. Kramarenko, V. A. Kushnir, A. Opanasenko, S. A. Perezhogin, D. L. Stepin, Z. V. Zhiglo
    NSC/KIPT, Kharkov
  An injector on the basis of a resonator structure with exponentially increasing amplitude of the electric field along an axis was developed at NSC KIPT. The injector is supplied with RF power through a rectangular-to-coaxial waveguide transition to provide axial symmetry of the accelerating field. The injector was designed to provide the output current up to 1 A at particle energy up to 1 MeV. Results of the injector test are presented in the work. Results obtained are compared with calculated ones.  
 
MOPP110 The SNS Resonance Control Cooling System Control Valve Upgrade Performance controls, linac, monitoring, feedback 814
 
  • D. C. Williams, J. P. Schubert, J. Y. Tang
    ORNL, Oak Ridge, Tennessee
  The normal-conducting linac of the Spallation Neutron Source (SNS) uses 10 separate Resonance Control Cooling System (RCCS) water skids to control the resonance of 6 Drift Tube Linac (DTL) and 4 Coupled Cavity Linac (CCL) accelerating structures. The RCCS water skids use 2 control valves; one to regulate the chilled water flow and the other is used to bypass water to a heat exchanger. These valves have hydraulic actuators that provide position and feedback to the control system. Frequency oscillations occur using these hydraulic actuators due to their coarse movement and control of the valves. New air actuator control positioners have been installed on the DTL3 RCCS water skid to give finer control and regulation of DTL3 cavity temperature. This paper shows a comparison of resonance control performance for two valve configurations.  
 
MOPP117 First Test of the Cornell Single-cavity Horizontal Cryomodule linac, cryogenics, radiation, vacuum 835
 
  • S. A. Belomestnykh, E. P. Chojnacki, R. Ehrlich, R. P.K. Kaplan, M. Liepe, V. Medjidzade, D. Meidlinger, H. Padamsee, P. Quigley, J. J. Reilly, D. M. Sabol, J. Sears, V. D. Shemelin, E. N. Smith, V. Veshcherevich, D. Widger
    CLASSE, Ithaca
  A single-cavity horizontal test cryomodule (HTC) has been designed and fabricated recently at Cornell University for ERL project. This cryomodule is a shortened version of the full injector cryomodule, which will house five superconducting cavities. It serves as a test bench for new design features and for testing fully dressed two-cell ERL injector cavities. The cryostat design has been optimized for precise cavity alignment, good magnetic shielding, and high cryogenic loads from the RF cavities, input couplers, and HOM loads. The HTC was made long enough so in the future it can accommodate longer, multicell cavities of the ERL main linac. In this paper we report on results from the first full test of the HTC, including RF system and superconducting cavity performance, cryomodule studies and operation of a new 1.8 K cryogenic system.  
 
MOPP129 Compensation of Lorentz Force Detuning for SC Linacs (with Piezo Tuners) controls, linac, monitoring, radio-frequency 862
 
  • M. K. Grecki, J. Andryszczak, T. Pozniak, K. P. Przygoda, P. M.S. Sekalski
    TUL-DMCS, Łódź
  The superconducting linacs use niobium cavities working with extremely high quality factor. Therefore the bandwidth of the cavity is very narrow and even subtle deformation caused by Lorentz force detunes the cavity a lot. For high gradient operation (over 15MV/m) the mechanical deformation of the cavity should be compensated by piezo tuner*. The paper presents design of a piezo control system and the results of measurements of its efficiency. It was demonstrated in FLASH accelerator that an initial detuning of 300Hz can be compensated by single pulse excitation of the piezo. The described system consist of multichannel programmable pulse generator driving a 8 channel piezo amplifiers capable to supply piezos with pulses up to 1A and up to 80V. It can compensate for Lorentz force detuning in all three FLASH cryhomodules equipped with piezos (ACC3,5,6).

*Liepe et al. "Dynamic Lorentz Force Compensation with a Fast Piezoelectric Tuner," PAC2001, pp. 1074-1076.

 
 
MOPP132 Progress Towards Development of an L-Band SC Traveling Wave Accelerating Structure with Feedback feedback, acceleration, coupling, linac 871
 
  • A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio
  • P. V. Avrakhov
    LPI, Moscow
  • S. Kazakov
    KEK, Ibaraki
  • N. Solyak, V. P. Yakovlev
    Fermilab, Batavia, Illinois
  We describe an ongoing experimental program and progress towards development of a conceptual design for a superconducting traveling wave accelerating structure for the ILC. The accelerating gradient can be significantly improved by the use of an RF feedback system redirecting the accelerating wave that passed through the superconducting traveling wave accelerator (STWA) section back to the input of the accelerating structure. The conceptual design of the SC traveling wave accelerator has been considered by P. Avrakhov et al. [PAC07, pp.2538], where shape optimization, coupler cell design and tuning issues in the feedback loop were presented. The proposed TW structure design gives an overall 24% increase in gradient over the 1 m long standing wave structure and potentially can reach 46% if a longer structure is employed. Experimental investigation of the TW SC structure considers tests of a single cavity having the same shape as the regular cell of the full-sized STWA structure, and the same ratio of the RF fields. The details of the individual parts, joint configurations along with some developments on forming and welding of the proposed cavity shapes are discussed.  
 
MOPP135 Vertical and Horizontal Test Results of 3.9 GHz Accelerating Cavities at FNAL electron, pick-up, instrumentation, alignment 874
 
  • T. N. Khabiboulline, H. T. Edwards, M. H. Foley, E. R. Harms, A. Hocker, D. V. Mitchell, A. M. Rowe, N. Solyak
    Fermilab, Batavia, Illinois
  The 3rd harmonic 3.9GHz accelerating cavity was proposed to improve the beam performance of the electron/positron linear accelerators. In the frame of a collaborative agreement, Fermilab will provide DESY with a cryomodule containing a string of four cavities. Several 9-cell Nb cavities were tested and they did reach accelerating gradient up to 24 MV/m almost twice more than design value of 14 MV/m. Two of these cavities are with new HOM couplers with improved design. In this paper we present all results of the vertical and horizontal tests.  
 
MOPP136 Performance of Single Crystal Niobium Cavities electron, cryogenics 877
 
  • P. Kneisel, G. Ciovati
    Jefferson Lab, Newport News, Virginia
  • A. Brinkmann, D. Reschke, W. Singer, X. Singer
    DESY, Hamburg
  We have fabricated and tested a total of six single cell niobium cavities, made from single crystal, high purity niobium. Two of the three cavities of the TESLA shape (1300 MHz) were made from Heraeus niobium by extending a smaller single crystals by rolling and annealing steps; the third cavity was made by spinning. The three other cavities of the scaled LL shape (2) and TESLA shape (1) resonated at 2.3 GHz and were fabricated from “as received” single crystals, both from Heraeus and CBMM niobium. After appropriate surface treatments by buffered chemical polishing and electropolishing all cavities performed quite nicely and peak surface magnetic fields of ~ 160 mT or above corresponding to accelerating gradients between 38 MV/m and 45 MV/m were reached. This paper reports about the performance of these cavities.  
 
MOPP149 Recent Developments of the Superconducting CH-Cavities simulation, cryogenics, beam-losses, linac 901
 
  • H. Podlech, A. Bechtold, M. Busch, F. Dziuba, H. Liebermann, U. Ratzinger
    IAP, Frankfurt am Main
  The Crossbar-H-mode (CH)-structure which has been developed at the IAP in Frankfurt is a multi-cell drift tube structure for the efficient acceleration of low and medium energy protons and ions. The superconducting low energy CH-prototype cavity has reached gradients of up to 7 MV/m, corresponding to an effective voltage gain of 5.6 MV. This shows that high real estate gradients can be achieved in superconducting low energy multi-cell cavities. Additionally, microphonics and tuning measurements have been performed at room temperature and at 4K. Optimized cavity geometry for high power beam projects and plans for the construction of a new superconducting cavity will be presented.  
 
TUOBG02 Study of Beam Dynamics During the Crossing of Resonances in the VEPP-4M Storage Ring octupole, emittance, collider, betatron 965
 
  • P. A. Piminov, V. A. Kiselev, E. B. Levichev, O. I. Meshkov, S. A. Nikitin
    BINP SB RAS, Novosibirsk
  The influence of resonances on the beam dynamics in the storage rings is of a substantial interest for the accelerator physics. For example, a fast crossing of resonances occurs in the damping rings of future linear colliders during the beam damping due to the coherent shift that can result in a loss of particles. We have studied experimentally the crossing of resonances of different power nearby the working point of the VEPP-4M storage ring. The observation of the beam sizes and particle losses has been done with a single-turn time resolution. The comparison with the numerical simulation has been made.  
slides icon Slides  
 
TUPC021 High Bandwidth Wall Current Monitor for CTF3 coupling, impedance, 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.  
 
TUPC023 Design of the Transverse C-band Deflecting Structure for Measurement of Bunch Length in X-FEL coupling, RF-structure, simulation, klystron 1098
 
  • H. Ego
    JASRI/SPring-8, Hyogo-ken
  • Y. Otake
    RIKEN/SPring-8, Hyogo
  In SPring-8, the 8 GeV X-FEL with a short length of about 700 m is under construction. An electron beam with a bunch length in duration of less than 200 fs is indispensable for stable and brilliant X-ray radiation. We planned to measure the short bunch length with a transverse RF deflector. A bunch measuring system including the deflector must be located within 15 m of a bunch compressor at a beam energy of 1.45 GeV. To install the system in the restricted space, we need a deflector generating a transverse deflecting voltage over 40 MV. Therefore a new C-band deflecting structure was designed. It is a periodic disk-loaded structure with a racetrack-shaped iris in the center of each disk. The deflecting resonant mode is the HEM11-5π/6 mode of a backward traveling-wave and its transverse shunt impedance is more than 12 MΩ/m. The racetrack-shaped iris serves both as a cell-to-cell coupler and a beam passing hole, prevents rotation of the deflection plane of the HEM11 mode and makes the deflecting mode resonant stably. We represent the details and merits of the C-band structure with the demanded performance in this paper.  
 
TUPC041 Design of Cold BPM Feedthrough simulation, insertion, impedance, 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.  
 
TUPC042 Limitations of Electro-optic Longitudinal Electron Bunch Length Measurements simulation, laser, diagnostics, coupling 1149
 
  • S. P. Jamison
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • G. Berden
    FOM Rijnhuizen, Nieuwegein
  • W. A. Gillespie, P. J. Phillips
    University of Dundee, Nethergate, Dundee, Scotland
  • A. MacLeod
    UAD, Dundee
  Electro-optic (EO) techniques are becoming increasingly important in ultrafast electron bunch longitudinal diagnostics and have been implemented at various accelerator labs. A crucial aspect of any implementation is a robust assessment of its resolution capabilities. However the assessments of the temporal limitations often differ between groups and the assumptions employed in deriving these limitations are frequently not addressed. With EO measurements of intense CTR pulses and ultrafast Coulomb fields, it may also be necessary to reconsider the validity of the usual interpretation of the EO effect as a phase retardation proportional to the Coulomb field. From a generic analysis of various sources of the temporal limitations we present a summary of the capability of various EO techniques which can be applied to specific implementations with differing laser and bunch parameters. As well as specifying the quantitative limitations and their scaling with experimental parameters, the qualitative effects of distortion in the measured profile are also summarised. Additional limitations, which arise from a breakdown of the phase-retardation interpretation of the EO effect, are discussed.  
 
TUPC081 Single-shot Longitudinal Bunch Profile Measurements at FLASH Using Electro-optic Detection Techniques electron, laser, linac, simulation 1242
 
  • P. J. Phillips, W. A. Gillespie
    University of Dundee, Nethergate, Dundee, Scotland
  • V. R. Arsov, H. Schlarb, B. Schmidt, P. Schmüser
    DESY, Hamburg
  • G. Berden, A. F.G. van der Meer
    FOM Rijnhuizen, Nieuwegein
  • S. P. Jamison
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • A. MacLeod
    UAD, Dundee
  • B. Steffen
    PSI, Villigen
  At the superconducting linac of FLASH at DESY, we have installed an electro-optic experiment for single-shot, non destructive measurements of the longitudinal electric charge distribution of individual electron bunches. The profile of the electron bunch field is electro-optically encoded onto a streched Ti:Sa laser pulse. In the decoding step, the profile is retrieved from a spectral measurement of the encoded pulse or from a cross-correlation of the encoded pulse with a 35 fs laser pulse , obtained from the same laser. At FLASH, sub-100 fs electron bunches have been measured during FEL operation with a resolution of better than 50 fs. The electro-optic measurements have been validated with a tranverse deflecting cavity measurements.  
 
TUPC141 Concept and Implementation of the SC Cavity Resonance Frequency Monitor for the Digital RF Field Controller controls, klystron, laser, monitoring 1398
 
  • W. Jalmuzna, A. Napieralski
    TUL-DMCS, Łódź
  • S. Simrock
    DESY, Hamburg
  New generations of digital control systems offer large number of computation resources together with precise ADCs (analog to digital converters) and DACs (digital to analog converters) which can be used to generate almost any klystron driving signal. This gives the possibility to implement such features as digital SEL (self excited loop) and frequency sweep mode. They can be used to monitor resonance frequency of SC cavities. This information can be used by tuning system to adjust cavity tuner settings. Such functionality is valuable especially during the first RF station start up when the cavities may be detuned even by a large frequency. The paper presents the concept of such system and summarizes implementation and tests performed at FLASH facility (DESY, Hamburg).  
 
TUPC145 FPGA Implementation of Multichannel Detuning Computation for SC Linacs controls, linac, diagnostics, feedback 1410
 
  • K. P. Przygoda, J. Andryszczak, W. Jalmuzna, A. Napieralski, T. Pozniak
    TUL-DMCS, Łódź
  The paper presents a multi-cavity system for active compensation of SC cavities' deformations in linear accelerators like Free Electron Laser. Described system consists of digital controller, analog amplifiers and mechanical actuators. The previously developed control algorithms were implemented in SIMCON 3.1 board and allow online calculations of Lorentz force detuning only for one cavity. The recent development in the field is based on serial pipelined computations which allow a real time detuning measurements of 8 and more cavities. Moreover, the SIMCON DSP board was used for 10 ns latency computations. The new approach enables integrating the algorithm dedicated for cavity shape control with the LLRF control system using optical transmission. Furthermore the 8-channels amplifiers have been successfully added to the compensation system for driving the piezoelectric actuators. The system is tested in FLASH at DESY. The accelerating modules ACC 3, 5 and 6 with high operating gradients cavities have been taken into account. The multilayer piezostacks from PI and NOLIAC are used for the compensation purpose of cavities' deformations.  
 
TUPC146 Real Time, Distributed, Hardware-software Simulation of Multicavity RF Station for LLRF System Development in FLASH and XFEL simulation, klystron, controls, diagnostics 1413
 
  • P. Pucyk, S. Simrock
    DESY, Hamburg
  • W. Jalmuzna
    TUL-DMCS, Łódź
  The paper describes the implementation of distributed (FPGA, DSP, GPP) system for simulation of multiple TESLA cavities together with high power distribution chain. The applied models simulate the system behavior with the performance close to the response time of the real RF station and cryomodules. Parametrized architecture of the simulator allows to find compromise between the features of the model and the available resources it can be implemented in. The results of driving the simulator using the FLASH LLRF system are presented and compared with the real measurements. Proposed solution is the important tool for LLRF system development and testing, and can be, in many cases, a replacement for the tests in the real superconducting test facilities reducing the development costs and time.  
 
TUPC147 Analogue LLRF for the ALBA Booster booster, controls, synchrotron, injection 1416
 
  • H. Hassanzadegan, F. Pérez
    ALBA, Bellaterra
  ALBA Booster will inject up to 2 mA of current, at 3 Hz, in the 3 GeV 3rd generation Synchrotron Light Source ALBA, that is in the construction phase in Cerdanyola, Spain. The Booster will ramp the beam energy from 100 MeV to 3 GeV, the RF voltage will be ramped as well from <100 kV to 1 MV to improve injection efficiency and maintain the beam stable. The Booster RF System will have to provide up to 1 MV of accelerating voltage and have a high dynamic range. An Analogue LLRF prototype has been developed for the Booster 5 cell RF Cavity. The prototype is based on the IQ modulation/demodulation technique and it has been designed completely in house. The prototype has been installed in the high power RF lab of CELLS and tested to control up to 80 kW on the real Booster Cavity. The test results of the control loops (amplitude, phase and tuning) will be presented, as well as the hardware structure and the system interface.  
 
TUPC148 Digital LLRF for ALBA Storage Ring controls, vacuum, diagnostics, storage-ring 1419
 
  • A. Salom, F. Pérez
    ALBA, Bellaterra
  ALBA is a 3 GeV, 400 mA, 3rd generation Synchrotron Light Source that is in the construction phase in Cerdanyola, Spain. The RF System will have to provide 3.6 MV of accelerating voltage and restore up to 540 kW of power to the electron beam. A Digital LLRF prototype has been developed for the Storage Ring RF Cavity. The prototype is based on the IQ modulation/demodulation technique and it has been implemented using a commercial FPGA cPCI board. The prototype has been installed in the high power RF lab of CELLS and tested to control up to 80 kW on the real Storage Ring Cavity. The test results of the control loops (amplitude, phase and tuning) will be presented, as well as the hardware structure (digital boards, analogue front ends, timing, etc.) and the system interface.  
 
TUPD024 Results of ELBE Window and Coupler Tests with a Resonant Ring vacuum, klystron, controls, coupling 1479
 
  • A. Buechner, H. Buettig, R. Schurig, G. Staats, A. Winter
    FZD, Dresden
  A new test bench based on a resonant ring has been built at ELBE to run window as well as coupler tests. The resonant ring is driven by a 10 kW klystron and allows tests with RF power up to 100 kW in CW mode and about 200 kW in pulsed mode. Coupler tests are done with liquid Nitrogen cooling under almost real conditions. The results of warm window and coupler tests in pulsed and CW mode are presented. Also details about the ring and a special designed coupler tip to rectangular waveguide transition are given.  
 
TUPP015 Investigations into Cost Reductions of X-band Instrumentation instrumentation, klystron, controls, coupling 1559
 
  • D. Van Winkle, V. A. Dolgashev, J. D. Fox, S. G. Tantawi
    SLAC, Menlo Park, California
  The prohibitive costs of commercial test equipment for making fast and accurate pulsed phase and amplitude measurements at X-band result in decreased productivity due to shortages of shared equipment across the test laboratory. In addition, most current set-ups rely on the use of pulsed power heads which do not allow for the measurement of phase thereby limiting the flexibility of available measurements. In this paper, we investigate less expensive in-house designed instrumentation based upon commercial satellite down converters and widely available logarithmic detector amplifiers and phase detectors. The techniques are used to measure X-band pulses with widths of 50 ns to 10’s of usec. We expect a dynamic range of 30-40 dB with accuracies of less than ± 0.1 dB. We show results of the built and tested systems with particular attention focused on temperature performance and accuracy. Block diagrams of the down conversion scheme, and the architecture of a multi-signal X-band RF monitor and measurement system is illustrated. Measured results, and possible modifications and upgrades are presented.  
 
TUPP024 Electron Cyclotron Resonances in Electron Cloud Dynamics electron, simulation, cyclotron, wiggler 1583
 
  • C. M. Celata, M. A. Furman, J.-L. Vay, J. W. Yu
    LBNL, Berkeley, California
  We report a previously unknown resonance for electron cloud dynamics. The 2D simulation code “POSINST” was used to study the electron cloud buildup at different z positions in the International Linear Collider positron damping ring wiggler. At magnetic field values, B, for which the bunch frequency is an integral multiple of the electron cyclotron frequency an enhancement of up to a factor of 3 in the electron cloud equilibrium density was found. At low magnetic fields the effects of the resonance are prominent, but when B exceeds ~ (2πme/elb), with lb = bunch length, effects of the resonance disappear. Thus short bunches and low B fields are required for observing the effect. We believe this accounts for the fact that this resonance has not been reported before in the electron cloud literature. The reason for the B field dependence, an explanation of the dynamics, and the results of the 2D simulations and of a single-particle tracking code used to elucidate details of the dynamics will be discussed, along with results from 3D simulations.  
 
TUPP029 Beam Coupling Impedance Measurement and Mitigation for a TOTEM Roman Pot impedance, 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.  
 
TUPP054 A Model of an Electrical Discharge in the Flange Contacts with Omega Seals at High Currents in PEP-II radiation, vacuum, synchrotron, synchrotron-radiation 1667
 
  • A. Novokhatski, J. Seeman, M. K. Sullivan
    SLAC, Menlo Park, California
  During operation with high currents at HER (High Energy Ring), high temperature elevation was found at almost every location of the vacuum chamber flange contacts. Omega RF seals were strongly damaged or even evaporated by sparks and electrical discharge. We suggest a physical model, which may explain this effect.  
 
TUPP055 Loss Factor of the PEP-II Rings radiation, synchrotron, synchrotron-radiation, luminosity 1670
 
  • A. Novokhatski, M. K. Sullivan
    SLAC, Menlo Park, California
  RF power balance method is used to measure the synchrotron radiation losses and the wake field losses. We present the history of the loss factor during the last several runs, which reveals many interesting correlations with vacuum chamber improvement and processing.  
 
TUPP058 Impedance Estimation of Diamond Cavities impedance, simulation, storage-ring, vacuum 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.  
 
TUPP062 Beam Coupling Impedance Studies on LHC FP420 Multi-pocket Beam Pipe Prototype impedance, simulation, coupling, 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 impedance, vacuum, coupling, simulation 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.  
 
TUPP076 Longitudinal and Transverse Impedances of XFEL Kicker Vacuum Chamber impedance, vacuum, kicker, dipole 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.  
 
TUPP095 Computation of Resistive Wall Wakefields with the PBCI Code simulation, impedance, 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.  
 
TUPP097 New Formalism in the Spin Tracking Code Spink synchrotron, quadrupole, radio-frequency, extraction 1756
 
  • A. U. Luccio, F. Lin
    BNL, Upton, Long Island, New York
  The code Spink*, in use for more than 10 years to track polarized hadrons in a synchrotron, was overhauled with the introduction of a new system of coordinates based on a generalized Frenet-Serret system in all dimensions in space, which allows a better treatment of the curvature of the reference orbit. Two more improvements are (a) treatment of tensor polarization for particles like polarized deuterons, and (b) inclusion of space charge and beam-beam effects, so the code can be used to track spin in synchrotrons with high luminosity like new generation colliders.

*A. U. Luccio. Proc. Adriatico Research Conf. on Trends in Colliders
Spin Physics. Trieste, Italy, 12/5-8, 1995.

 
 
TUPP119 Lattice Design of a Carbon Ion Synchrotron for Cancer Therapy extraction, lattice, betatron, synchrotron 1803
 
  • H.-S. Kang, H. S. Suh
    PAL, Pohang, Kyungbuk
  A synchrotron accelerator for carbon ion cancer therapy was designed to be compact for a hospital based therapy facility. The circumference of the synchrotron is only 60 meter and the lattice is the FODO structure of 6 cells. Each cell has two dipole magnets with a angle of 30 degree. The lattice satisfies the requirement of Hardt condition for slow beam extraction which is to align the separatrices of different momenta of the particles.  
 
TUPP123 SCENT300, A Superconducting Cyclotron For Hadrontherapy cyclotron, extraction, emittance, ion 1812
 
  • M. M. Maggiore, L. Calabretta, D. Campo, D. Garufi, L. A.C. Piazza, M. Re
    INFN/LNS, Catania
  • E. Samsonov
    JINR, Dubna, Moscow Region
  SCENT300 is a superconducting cyclotron able to deliver proton and C beam at 260 and 300 AMeV respectively. The study of the machine is near to be completed. The mechanical and magnetic design will be presented. The mechanical drawing and size of the cyclotron will be presented. The characteristics of the main coil and magnetic field will be presented. The method to change the magnetic setting for H2 and Carbon acceleration will be described. The acceleration system consisting of 4 RF cavities will be also described.  
 
WEXG01 Performance of KEKB with Crab Cavities luminosity, simulation, coupling, collider 1893
 
  • Y. Funakoshi
    KEK, Ibaraki
  20 years after they were initially proposed, in February 2007 crab cavities are for the first time installed in an operating collider, KEKB. The commissioning of KEKB with crab cavities is presented, and the performance of the collider is compared to the performance without crab cavities. Lessons learned from the operation with such cavities for future projects are discussed.  
slides icon Slides  
 
WEOBG02 Experimental Results of a Plasma Wakefield Accelerator Using Multiple Electron Bunches plasma, electron, simulation, diagnostics 1912
 
  • E. Kallos, T. C. Katsouleas, P. Muggli
    USC, Los Angeles, California
  • W. D. Kimura
    STI, Washington
  • K. Kusche, J. H. Park, I. Pogorelsky, D. Stolyarov, V. Yakimenko
    BNL, Upton, Long Island, New York
  We present some preliminary experimental results of a plasma wakefield accelerator technique which utilizes multiple electron bunches in order to drive a plasma wave. The experiments were performed at the Accelerator Test Facility of Brookhaven National Laboratory where 5-8 equidistant bunches with a spacing which was varied between 100-250 m were fed into a 6mm-long capillary discharge plasma. By varying the time delay of the bunches with respect to the discharge different plasma densities could be tuned, and the effects of the plasma on the bunches were recorded. Such multiple bunch schemes are of great interest because they can provide increased efficiencies and high transformer ratios for advanced accelerators.  
slides icon Slides  
 
WEPC002 Analysis of Beam Orbit Stability and Ground Vibrations at the Diamond Storage Ring quadrupole, feedback, ground-motion, storage-ring 1980
 
  • R. Bartolini, H. C. Huang, J. Kay, I. P.S. Martin
    Diamond, Oxfordshire
  With the aim of understanding and improving the beam orbit stability at the Diamond storage ring we launched an extensive campaign of ground and magnets vibration measurements in order to identify the sources of ground vibration and how they affect the beam orbit stability through the girder resonances. We present here the results of the measurements performed during 2007 along with a discussion of the possible remedies and the implications for the orbit feedback systems.  
 
WEPC025 First 18 Months Operation of the Diamond Storage Ring RF System storage-ring, vacuum, controls, synchrotron 2037
 
  • M. Jensen, M. Maddock, P. J. Marten, S. A. Pande, S. Rains, A. F. Rankin, D. Spink, A. V. Watkins
    Diamond, Oxfordshire
  Since the Diamond Light Source became operational in January 2007, the storage ring RF system has operated for 5000 hours in 2007 and is scheduled to operate for 5350 hrs in 2008. This paper presents some of the key challenges of the storage ring RF system including reliability, performance observations and future improvements.  
 
WEPC045 Alternative Lattice Settings for ALBA Storage Ring sextupole, lattice, optics, dynamic-aperture 2088
 
  • M. Munoz, G. Benedetti, D. Einfeld, Z. Martí
    ALBA, Bellaterra
  ALBA is a 3 GeV synchrotron light source under construction in Spain. The lattice for the standard operational mode is based in a DBA-like structure, with finite dispersion in the straight sections and extra space in the arcs. This solution provides small emittance with a large available space for insertion devices, RF and diagnostic components, and large dynamic aperture and energy acceptance. Other optic modes has been investigated, in order to facilitate the commissioning procedure or to provide different operating modes to the users: pure achromatic lattice, without dispersion in the straight section; achromatic arcs, where the dispersion is zero in the long straight; or a relaxed lattice, offering higher emittance. This paper review the performance of this alternative options, including the non-linear performance.  
 
WEPC051 Upgrade Plans for the ESRF Storage Ring Lattice lattice, quadrupole, sextupole, simulation 2106
 
  • A. Ropert, L. Farvacque
    ESRF, Grenoble
  The lattice of the ESRF storage ring is of the Double Bend Achromat type with 32 straight sections of alternating high and low horizontal beta values, currently providing 5 m of available space for insertion devices. As part of the ESRF Upgrade Programme, it is proposed to increase the length of selected insertion device straight sections from 5 to 7 m. In this paper, we will describe the different steps towards longer straight sections: implementation of a new lattice in which the straight section quadrupole triplets are replaced by doublets, design of modified straight sections with replacing the long quadrupoles by shorter ones and moving the adjacent sextupoles, experiments carried out to simulate the lattice symmetry breaking induced by a 7 m long straight section.  
 
WEPP002 The Effect of Head-on Beam-beam Compensation on the Stochastic Boundaries and Particle Diffusion in RHIC emittance, proton, simulation, electron 2521
 
  • N. P. Abreu, W. Fischer, Y. Luo, G. Robert-Demolaize
    BNL, Upton, Long Island, New York
  To compensate the effects from the head-on beam-beam interactions in the polarized proton operation in the Relativistic Heavy Ion Collider (RHIC), an electron lens (e-lens) is proposed to collide head-on with the proton beam. We used an extended version of SixTrack for multiparticle beam-beam simulation in order to study the effect of the e-lens on the stochastic boundary and also on diffusion. The stochastic boundary was analyzed using Lypunov exponents and the diffusion was characterized as the average rms spread of the action after 104 turns. For both studies the simulations were performed with and without the e-lens and with full and partial compensation.  
 
WEPP024 Non-linear Correction Schemes for the Phase 1 LHC Insertion Region Upgrade and Dynamic Aperture Studies dynamic-aperture, quadrupole, optics, insertion 2569
 
  • R. Tomas, M. Giovannozzi, R. de Maria
    CERN, Geneva
  The Phase 1 LHC Interaction Region (IR) upgrade aims at increasing the machine luminosity essentially by reducing the beam size at the Interaction Point (IP). This requires a total redesign of the full IR. A large set of options have been proposed with conceptually different designs. This paper reports on a general approach for the compensation of the multipolar errors of the IR magnets in the design phase. The goal is to use the same correction approach for the different designs. The correction algorithm is based on the computation of the IR transfer map. Its performance is tested using the dynamic aperture as figure of merit.  
 
WEPP026 Reliable Operation of the AC Dipole in the LHC dipole, emittance, simulation, injection 2575
 
  • R. Tomas, S. D. Fartoukh, J. Serrano
    CERN, Geneva
  The AC dipole in the LHC will not only provide transverse oscillations without emittance growth but also with a safety guarantee. These two features are due to the adiabaticity of the excitation. However chromaticity and non-linear fields spoil this adiabaticity. This paper assesses the margins of the relevant parameters for a reliable and safe operation of AC dipoles in the LHC.  
 
WEPP034 Study of Beam-beam effect at various collision scheme in LHC luminosity, simulation, emittance, proton 2593
 
  • K. Ohmi
    KEK, Ibaraki
  LHC is designed as two major collision points with finite crossing angle of 140μrad (half). The Piwinski angle is 0.4 for the design. Upgrade plans have been studied to increase the luminosity 10 times. Large Piwinski angle scheme is one of the option for the upgrade. The one turn map with the two beam-beam interactions can be expanded by Taylor series. Analyzing the one turn map gives information of resonance behavior of the beam-beam interactions. We discuss the one turn map for the design LHC and upgrade scheme.  
 
WEPP035 Study of Beam-beam Issue for KEKB Crab Crossing luminosity, coupling, lattice, simulation 2596
 
  • K. Ohmi, J. W. Flanagan, Y. Funakoshi, N. Iida, H. Koiso, A. Morita, Y. Ohnishi, K. Oide, Y. Seimiya
    KEK, Ibaraki
  A short lifetime at collision is one of the limits on luminosity performance at KEKB in crab crossing mode. The beam-beam halo was evaluated via simulation. The beam lifetime and profile were measured for various beam conditions, vertical emittances, tunes and collision offsets. We discuss why the lifetime is shortened by the beam-beam interaction.  
 
WEPP045 Suppression of Beam-beam Resonances in Crab Waist Collisions luminosity, sextupole, betatron, collider 2620
 
  • M. Zobov, P. Raimondi
    INFN/LNF, Frascati (Roma)
  • D. N. Shatilov
    BINP SB RAS, Novosibirsk
  The recently proposed Crab Waist scheme of beam-beam collisions can substantially increase the collider luminosity since it combines several potentially advantageous ideas. One of the basic ingredients of the scheme is the use of dedicated sextupoles in the interaction region for the vertical beta function waist rotation at the interaction point. In this paper we show how this nonlinear focusing helps to suppress betatron and synchrobetatron resonances arising in beam-beam collisions due to particles’ vertical motion modulation by their horizontal oscillations.  
 
WEPP093 Prototype of Parallel Coupled Accelerating Structure coupling, focusing, controls, linac 2737
 
  • A. E. Levichev, V. M. Pavlov
    BINP SB RAS, Novosibirsk
  • Y. D. Chernousov
    ICKC, Novosibirsk
  • V. Ivannikov, I. V. Shebolaev
    ICKC SB RAS, Novosibirsk
  The prototype of parallel coupled accelerating structure is developed. It consists of five accelerating cavities, common excitation cavity and RF power waveguide feeder. The excitation cavity is a segment of rectangular waveguide loaded by cupper pins. The excitation cavity operate mode is TE105. Connection between excitation cavity and accelerating cavities is performed by magnetic field. The expressions for coupled factor excitation cavity to accelerating cavities and coefficient of efficiency for RF power transmission from generator to accelerating cavities are obtained using coupled cavities theory. The parallel coupled accelerating structure electrodynamic characteristics are measured.  
 
WEPP125 Analysis of the Vertical Beam Instability in CTF3 Combiner Ring and New RF Deflector Design controls, emittance, simulation, impedance 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.  
 
WEPP140 X-band PASER Experiment acceleration, dipole, electron, laser 2824
 
  • A. Kanareykin, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio
  • S. P. Antipov
    ANL, Argonne, Illinois
  • L. Schächter
    Technion, Haifa
  The PASER concept for particle acceleration entails the direct transfer of energy from an active medium to a charged particle beam. The PASER was originally formulated for optical (laser) media; we are pursuing a PASER demonstration experiment based on an optically pumped paramagnetic medium active in the X-band. We report on the development of a relatively high energy density microwave active medium consisting of a fullerene (C60) derivative in a toluene solution. We discuss both the bench test of an amplifier and a beam acceleration experiment under construction that employ this medium as a power source. Applications of the technology to accelerators and microwave components will be presented.  
 
WEPP142 Simulation of and Progress towards a Micron-scale Laser-powered Dielectric Electron Source simulation, laser, vacuum, coupling 2827
 
  • G. Travish, J. B. Rosenzweig, J. Xu
    UCLA, Los Angeles, California
  • S. Boucher
    RadiaBeam, Marina del Rey
  • R. B. Yoder
    Manhattan College, Riverdale, New York
  A dielectric, slab-symmetric structure for generating and accelerating low-energy electrons has been under study for the past two years. The resonant device is driven by a side-coupled laser and is configured to maintain field provide necessary for synchronous acceleration and focusing of nonrelativistic particles. Intended applications of the structure include the production of radiation for medical treatments, imaging, and industrial uses. The details of the structure geometry and its resonant properties have been studied with 2D and 3D electromagnetic codes, the results of which are present here.  
 
WEPP147 Aberration-free Muon Transport Line for Extreme Ionization Cooling: a Study of Epicyclic Helical Channel simulation, cyclotron, collider, dipole 2833
 
  • A. Afanasev, R. P. Johnson
    Muons, Inc, Batavia
  • Y. S. Derbenev
    Jefferson Lab, Newport News, Virginia
  Once the normalized transverse emittances of a muon beam have been cooled to some hundreds of microns, new techniques such as Parametric-resonance Ionization Cooling and Reverse Emittance Exchange can be used to focus the beam very tightly on beryllium energy absorbers for further transverse emittance reduction. The transport lines for these techniques have stringent requirements for the betatron tunes so that resonance conditions are properly controlled and for the dispersion function so that the longitudinal emittance can be controlled by emittance exchange using wedge-shaped absorbers. The extreme angular divergence of the beam at the absorbers implies large beam extension between the absorbers such that these techniques are very sensitive to chromatic and spherical aberrations. In this work we describe general and specific solutions to the problem of compensating these aberrations for these new muon cooling channels.  
 
WEPP149 Advances in Parametric-resonance Ionization Cooling emittance, coupling, space-charge, betatron 2838
 
  • Y. S. Derbenev
    Jefferson Lab, Newport News, Virginia
  • R. P. Johnson
    Muons, Inc, Batavia
  Parametric-resonance ionization cooling (PIC) is a muon-cooling technique that is useful for low-emittance muon colliders. This method requires a well-tuned focusing channel that is free of chromatic and spherical aberrations. The dispersion function of the channel must be large where the correction magnets are placed for aberration control but small and non-zero where the ionization cooling beryllium wedges are located to provide emittance exchange to maintain small momentum spread. In order to be of practical use in a muon collider, it also necessary that the focusing channel be as short as possible to minimize muon loss due to decay. A compact PIC focusing channel is described in which new magnet concepts are used to generate the required lattice functions.  
 
THYM02 Incoherent Effects of Space Charge and Electron Cloud incoherent-effects, beam-losses, emittance, space-charge 2942
 
  • G. Franchetti, I. Hofmann
    GSI, Darmstadt
  • F. Zimmermann
    CERN, Geneva
  Trapping in, or scattering off, resonances driven by space charge or electron cloud in conjunction with synchrotron motion can explain numerous observations of slow beam loss and emittance growth, which are often accompanied by changes in the longitudinal beam profile. This talk will review recent progress in understanding and modelling the underlying mechanisms, highlight the differences and similarities between space charge and electron cloud, and discuss simulation results in the light of experimental observations, e.g., at GSI, CERN and BNL.  
slides icon Slides  
 
THPPGM01 A Control and Systems Theory Approach to the High Gradient Cavity Detuning Compensation controls, feedback, coupling 2952
 
  • R. Paparella
    INFN/LASA, Segrate (MI)
  The compensation of dynamic detuning is of primary importance in order to operate TESLA type cavities at the high accelerating gradient foreseen for the ILC (31.5 MV/m). This article firstly resumes recent successful experiences of open loop compensation of the Lorentz force detuning, repetitive and synchronous to the RF pulse, using fast piezoelectric actuators with different fast tuning systems. Possible strategies and results for the closed loop compensation of the stochastic microphonic detuning are also presented. Lastly, a deep characterization of the system under control is given, exploiting the system transfer functions acquired through both installed piezo actuators/sensors and phase locked measurements. This ultimately allows the analytical modeling of the behavior of cavity detuning and of its active compensation with piezoelectric actuators.  
slides icon Slides  
 
THPC023 Optimization of the AGS Superconducting Helical Partial Snake Strength polarization, betatron, acceleration, simulation 3026
 
  • F. Lin, H. Huang, A. U. Luccio, T. Roser
    BNL, Upton, Long Island, New York
  Two helical partial snakes, one is superconducting (called cold snake) and one is normal conducting (called warm snake), have preserved the polarization of proton beam up to 65% at the AGS extraction energy with the inject 82% polarization. In order to overcome the spin resonances, stronger partial snake is required. However, the stronger partial snake, the more titled stable spin direction that results in stronger horizontal intrinsic resonance. The balance between raising the spin tune gap generated by the snakes and reducing the titled stable spin direction has to be considered to maintain the polarization. Because the magnetic field of the warm snake is constant, only the cold snake with a maximum 3T magnetic field can be varied to find out the optimized snake strength. The paper presents the simulation results from the spin tracking with different cold snake magnetic fields. Some experimental data are also analyzed.  
 
THPC026 Measurement of Complex Coupling Driving Term of Linear Difference Resonance Using Turn-by-turn Beam Position Monitors coupling, betatron, quadrupole, storage-ring 3035
 
  • M. Masaki, K. Soutome, S. Takano, M. Takao
    JASRI/SPring-8, Hyogo-ken
  X-Y emittance coupling is one of the important measures of beam quality in an electron storage ring for high brilliant light source. We have developed a method of measuring complex coupling driving term C of linear difference resonance using turn-by-turn beam position monitors (BPMs), assuming the perturbation theory with the single resonance approximation. Since both amplitude and phase of the driving term are derived, we can uniquely determine the strength of two-degree-of-freedom skew quadrupole magnets for correction of the linear resonance coupling. Before the correction, the driving term was measured by the developed method at the SPring-8 storage ring where small skew quadrupole components are distributed as error magnetic fields. On the other hand, the linear resonance coupling was corrected using the counter skew quadrupole magnets, the strength of which was adjusted to minimize vertical beam size near the linear difference resonance. The measured driving term C was broadly consistent with the counter term calculated from the adjusted strength of skew quadrupole magnets for the coupling correction.  
 
THPC049 Progress in the Beam Preparation for the Multi-turn Extraction at the CERN Proton Synchrotron extraction, octupole, sextupole, proton 3089
 
  • S. S. Gilardoni, F. Franchi, M. Giovannozzi
    CERN, Geneva
  A new type of extraction based on beam trapping inside stable islands in the horizontal phase space will become operational during 2008 at the CERN Proton Synchrotron. A series of beam experiments was carried out to prove loss-less capture with high intensity and multi-bunched beams, up to 1500·1010 protons per pulse, in preparation of the extraction commissioning. These fundamental steps for the new Multi-turn Extraction are presented and discussed in details.  
 
THPC050 Experimental Evidence of Beam Trapping with One-third and One-fifth Resonance Crossing octupole, proton, sextupole, synchrotron 3092
 
  • S. S. Gilardoni, F. Franchi, M. Giovannozzi
    CERN, Geneva
  Beam trapping in stable islands of the horizontal phase space generated by non-linear magnetic fields is realized by means of a given tune variation so to cross a resonance of order n. Whenever the resonance is stable, n+1 beamlets are created whereas if the resonance is unstable, the beam is split in n parts. Experiments at the CERN Proton Synchrotron showed protons trapped in stable islands while crossing the one-third and one-fifth resonance with the creation of 3 and 6 stable beamlets, respectively. The results are presented and discussed in details.  
 
THPC051 Adiabaticity and Reversibility Studies for Beam Splitting Using Stable Resonances synchrotron, coupling, emittance, proton 3095
 
  • S. S. Gilardoni, F. Franchi, M. Giovannozzi
    CERN, Geneva
  At the CERN Proton Synchrotron, a series of beam experiments proved beam splitting by crossing the one-fourth resonance. Depending on the speed at which the horizontal resonance is crossed, the splitting process is more or less adiabatic, and a different fraction of the initial beam is trapped in the islands. Experiments prove that when the trapping process is reversed and the islands merged together, the final distribution features thick tails. The beam population in such tails is correlated to the speed of the resonance crossing and to the fraction of the beam trapped in the stable islands. Experiments, simulations, and possible theoretical explanations are discussed.  
 
THPC053 Turn-by-turn Data Analysis at the Diamond Storage Ring betatron, storage-ring, optics, quadrupole 3101
 
  • R. Bartolini, I. P.S. Martin, G. Rehm, J. Rowland
    Diamond, Oxfordshire
  The Diamond Storage Ring has been recently equipped with a set of two pinger magnets that can excite betatron oscillations to large amplitudes in both planes of motion. In conjunction with the turn-by-turn capabilities available at all BPMs, the system provides a powerful diagnostic tools for the characterisation of the linear and non-linear beam dynamics of the electron beam in the storage ring. We report the first results on the application of the Frequency Map Analysis and the measurement of the resonant driving terms at the Diamond Storage Ring.  
 
THPC056 Stability Change of Fourth-order Resonance with Application to Multi-turn Extraction Schemes extraction, simulation, emittance, synchrotron 3110
 
  • M. Giovannozzi, D. Quatraro
    CERN, Geneva
  • G. Turchetti
    Bologna University, Bologna
  Recently, a novel multi-turn extraction scheme was proposed, based on particle trapping inside stable resonances. Numerical simulations and experimental tests confirmed the feasibility of such a scheme for low order resonances. While the 3rd order resonance is generically unstable and those higher than 4th order are generically stable, the 4th order resonance can be either stable or unstable depending on the details of the system under consideration. By means of the normal form approach a general formula to control the stability of the 4th order resonance is derived. Numerical simulations confirm the analytical results and show that by crossing the unstable 4th order resonance the region around the centre of phase space is depleted and particles are trapped only in the four stable islands. This indicates that a four-turn extraction could be envisaged based on this technique.  
 
THPC058 High Order Super-periodic Structural Resonances lattice, storage-ring, synchrotron, synchrotron-radiation 3116
 
  • Y. Jiao, S. X. Fang, J. Q. Wang
    IHEP Beijing, Beijing
  High order super-periodic structural resonances, which arise from the study of SSRF lattice optimization, are found to have large effects on beam dynamics. The mechanism and feature of this kind of resonances are described in the text. The limit to beam dynamics of other light sources are also found from these resonances.  
 
THPC060 Spin Flip of Deuterons in COSY - Spink Tracking dipole, simulation, polarization, betatron 3122
 
  • A. U. Luccio
    BNL, Upton, Long Island, New York
  • A. Lehrach
    FZJ, Jülich
  The spin tracking code Spink, as recently overhauled*, has been used to study the deuteron spin resonances and spin flipping induced by a RF dipole and a RF solenoid. The modifications of the code followed extended discussions on the formalism used to model spin evolution in a synchrotron. The simulation shows a good agreement with published results of the measurements**.

*A. U. Luccio et al. See another contribution to this Conference.
**A. D. Krisch et al. PR-STAB 10, 07100-1, 2007.

 
 
THPC066 Measuring Ring Nonlinear Components via Induced Linear "Feed-down" sextupole, simulation, beam-losses, closed-orbit 3137
 
  • A. S. Parfenova, G. Franchetti, I. Hofmann
    GSI, Darmstadt
  The knowledge of the distribution in a ring of the non-linear components is important for the resonance compensation. We present a method to measure the lattice nonlinear components based on the non-linear tune response to a locally controlled closed orbit deformation. A test of this concept in the SIS18 synchrotron is presented and discussed.  
 
THPC067 ALBA Dynamic Aperture Optimization dynamic-aperture, sextupole, lattice, betatron 3140
 
  • P. A. Piminov, E. B. Levichev
    BINP SB RAS, Novosibirsk
  • D. Einfeld
    ALBA, Bellaterra
  The lattice of ALBA, the 3 GeV synchrotron light source in Spain, provides extremely low emittance of the beam. It is known that such lattices require strong sextupole magnets to compensate natural chromaticities. The paper describes strategy and results of the ALBA dynamic aperture optimization including both tune point selecting and sextupoles arrangement to increase the DA size.  
 
THPC072 Impact of Betatron Motion on Path Lengthening and Momentum Aperture in a Storage Ring betatron, storage-ring, optics, undulator 3152
 
  • M. Takao
    JASRI/SPring-8, Hyogo-ken
  The amplitude of the betatron motion in an electron storage ring becomes large in some cases, e.g. Touschek scattered electrons or injected beam. Then we cannot ignore the effect of a finite amplitude of betatron motion on the beam dynamics. The path lengthening of the central trajectory of betatron motion is one of the most serious manifestations of such an influence. Due to the synchrotron motion, the variation of the path length is converted into the energy deviation, so that the betatron motion gives the impact on the momentum aperture in the storage ring. In this paper the path lengthening by a finite amplitude betatron motion is calculated by means of the canonical perturbation method. The derived formula for the path lengthening is simply represented by the product of the chromaticity and the invariant amplitude. Using the formula, we discuss the impact of the betatron motion on momentum aperture in a Touschek effect.  
 
THPC073 Measurement of Resonance Driving Terms in the ATF Damping Ring coupling, sextupole, simulation, kicker 3155
 
  • R. Tomas, F. Zimmermann
    CERN, Geneva
  • K. Kubo, S. Kuroda, T. Naito, T. Okugi, J. Urakawa
    KEK, Ibaraki
  The measurement of resonance driving terms in the Damping Ring of the Accelerator Test Facility in KEK could help finding possible machine imperfections and even to optimize single particle stability through the minimization of non-linearities. The first experimental attempts of this enterprise are reported in this note.  
 
THPC082 Wire Excitation Experiments in the CERN SPS simulation, beam-losses, coupling, optics 3176
 
  • U. Dorda, J.-P. Koutchouk, R. Tomas, J. Wenninger, F. Zimmermann
    CERN, Geneva
  • R. Calaga, W. Fischer
    BNL, Upton, Long Island, New York
  In order to study the effect of long range interaction and its wire compensation experimentally, current carrying wires are installed in the CERN Super Proton Synchrotron (SPS). In this paper we summarize the main results of the 2007 wire excitation results at 26, 37 and 55 GeV including wire-current-, beam-wire distance and chromaticity scans. A strong dependence on the chromaticity and indications of a threshold effect at 37 and 55 GeV was found. The results are compared to simulation, to a simple analytic scaling law and to experimental results from RHIC. Wire-driven resonances have been observed through the Fourier spectrum of experimental BPM data and compared to simulations.  
 
THPC089 Electron-cloud Intrabunch Density Modulation electron, dipole, simulation, proton 3197
 
  • G. Franchetti
    GSI, Darmstadt
  • F. Zimmermann
    CERN, Geneva
  During the passage of a proton bunch through an electron cloud a complicated electron density modulation arises, with characteristic ring and stripe patterns of high density regions that move radially outward along the bunch. We present simulation results as well as a simple analytical model to reveal the morphology and main features of this phenomenon as well as its dependence on key parameters like bunch length, beam size, and bunch charge.  
 
THPC097 A Full Analytical Method to Determine Equilibrium Quantities of Mismatched Charged Particle Beams evolving in Linear Channels emittance, simulation, focusing, coupling 3203
 
  • R. P. Nunes, F. B. Rizzato
    IF-UFRGS, Porto Alegre
  The focus of this work is to show a full analytical expression to determine relevant equilibrium quantities of a magnetically focused and high-intensity charged particle beam when evolving in a linear channel. Through the current approach, some intermediate steps of our original hybrid model which have to be solved numerically now can be eliminated, leading to the obtainment of a full analytical expression. This expression relates initial beam parameters with those obtained at equilibrium, allowing that the fraction of halo particles f can be evaluated. As a consequence, through the developed model, beam quantities like the envelope and emittance can be naturally determined. This is important in the accelerator engineering, since halo characteristics is a factor to be considered in the design of its confinement structure. For validation, full self-consistent N-particle beam numerical simulations have been carried out and its results compared with the predictions supplied by the full analytical model. The agreement is shown to be nice as with the simulations as with the hybrid numerical-analytical version of the model.  
 
THPC100 Collisionless Relaxation in the Transport of Space Charge Dominated Beams simulation, focusing, space-charge, plasma 3209
 
  • R. Pakter, Y. Levin, T. N. Teles
    IF-UFRGS, Porto Alegre
  Relaxation to a final stationary state of particles interacting through long-range forces, such as Coulomb, is intrinsically different than that of systems with short-range interactions. While in the latter case it is known that the interparticle collisions drive the system to an equilibrium Maxwell-Boltzmann distribution, in the former case, the collision duration time diverges and the state of thermodynamic equilibrium is never reached. In this paper, a theory is presented which allows to quantitatively predict the final stationary state achieved by a transported space-charge dominated beam during a process of collisionless relaxation*. It is shown that a fully matched beam relaxes to a Fermi-Dirac distribution. However, when a mismatch is present and the beam oscillates, halo formation leads to a phase separation. The theory developed allows to quantitatively predict both the density and the velocity distributions in the final stationary state, including the halo.

* Y. Levin, R. Pakter, and T. N. Teles, Phys. Rev. Lett., 100, 040604 (2008).

 
 
THPP011 Beam Acceleration Studies of Proton NS-FFAG acceleration, lattice, emittance, proton 3398
 
  • T. Yokoi, J. H. Cobb
    OXFORDphysics, Oxford, Oxon
  • K. J. Peach, S. L. Sheehy
    JAI, Oxford
  The NS-FFAG is a novel idea of a fixed field accelerator which has advantages in flexible design and machine operation for fixed field accelerator. However, due to the large tune variation with energy, fast acceleration is a key issue to circumvent the resonance problem in a linear NS-FFAG. At the moment, there is no numerical study of how fast it needs be. In this paper, using a lattice of a NS-FFAG for particle therapy, results of tracking study including acceleration rate, positioning tolerance are presented.  
 
THPP022 IH Linac with Higher-order Modes linac, acceleration, ion, heavy-ion 3419
 
  • N. Hayashizaki, T. Hattori
    RLNR, Tokyo
  As one of a drift tube type linac, an Interdigital H-type (IH) linac has been applied for ion acceleration in low beta range. It can realize a resonant cavity of convenient size at low frequency band and higher shunt impedance at low velocity range. These characteristics are advantageous especially for heavy ion acceleration; therefore, this structure has been applied for heavy ion cancer therapy. The RF field is resonated in TE111 mode and the electric field does not have the axial field component. The accelerating field is excited by using the electrode of Interdigital shape. In order to apply this structure to intermediate beta range, we propose a IH linac with the TE11n mode of the higher-order mode (HOM). Although the operating frequency becomes higher by using HOM, it is convenient to accelerate ion beam of intermediate energy. The design of the cavity structure and the possibility are presented.  
 
THPP060 Simultaneous Extraction of Two Stable Beams for ISAC extraction, cyclotron, target, feedback 3503
 
  • G. Dutto, R. A. Baartman, P. G. Bricault, I. V. Bylinskii, A. Hurst, R. E. Laxdal, Y.-N. Rao, L. W. Root, P. Schmor, G. M. Stinson
    TRIUMF, Vancouver
  • J. M. Schippers
    PSI, Villigen
  The TRIUMF cyclotron was originally conceived for several proton beams extracted simultaneously at different energies. Recent operation includes a 500 MeV beam up to150 μA for meson users, a 500 MeV beam up to 80 μA for rare isotope production, and a 100 MeV beam up to 70μA for medical isotopes. The extraction of an additional high intensity proton beam, at an energy between 450 and 500 MeV for ISAC has now been given priority. With the rare ions produced from the existing and future primary beam lines, we will be able to operate two of the existing experimental areas simultaneously. Upgrading the cyclotron for higher intensity is in progress. A necessary goal for ISAC is the extraction of both primary proton beams with stability better than 1% to allow the highest possible temperatures to be reliably maintained at the ion production targets. A successful solution implemented for the existing primary ISAC beam has been simulated to be adaptable for both primary beams, given the particular angular separation between the two strippers in the cyclotron. Progress on intensity and stability studies and the layout of the extraction system will be presented.  
 
THPP068 Acceleration in spiral FFAG using field map data acceleration, extraction, injection, proton 3515
 
  • J. Pasternak, J. Fourrier
    LPSC, Grenoble
  • F. Meot
    CEA, Gif-sur-Yvette
  This paper presents beam dynamics studies regarding the variable energy operation of a spiral scaling FFAG (Fixed Field Alternating Gradient) accelerator designed for producing 70 to 180 MeV protons and acceleration simulations for different operation modes, corresponding to different extraction energies.  
 
THPP098 Simulations on a Beam Transport System for the Frankfurt Funneling Experiment rfq, simulation, ion, ion-source 3593
 
  • P. Kolb, N. Mueller, A. Schempp
    IAP, Frankfurt am Main
  The goal of the Frankfurt Funneling Experiment is to multiply beam currents by mergeing two low energy ion beams. Our setup consists of two ion sources, a two beam RFQ accelerator, a multigap deflector and a beam diagnostics. Current work is the design of a new beam transport between RFQ accelerator and deflector and first simulations will be presented.