Keyword: resonance
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MOPC002 Flow Induced Vibrations of the CLIC X-band Accelerating Structures quadrupole, alignment, linac, synchrotron 65
 
  • T.K. Charles, K. Ryan
    Monash University, Melbourne, Australia
  • M.J. Boland
    ASCo, Clayton, Victoria, Australia
  • G. Riddone
    CERN, Geneva, Switzerland
  • A. Samoshkin
    JINR, Dubna, Moscow Region, Russia
  
  Turbulent cooling water in the Compact Linear Collider (CLIC) accelerating structures will inevitably induce some vibrations. The maximum acceptable amplitude of vibrations is small, as vibrations in the accelerating structure could lead to beam jitter and alignment difficulties. A Finite Element Analysis model is needed to identify the conditions under which turbulent instabilities and significant vibrations are induced. Due to the orders of magnitude difference between the fluid motion and the structure's motion, small vibrations of the structure will not contribute to the turbulence of the cooling fluid. Therefore the resonant conditions of the cooling channels presented in this paper, directly identify the natural frequencies of the accelerating structures to be avoided under normal operating conditions. In this paper a 2D model of the cooling channel is presented finding spots of turbulence being formed from a shear layer instability. This effect is observed through direct visualisation and wavelet analysis.  
 
MOPC019 Condition of MA Cut Cores in the RF Cavities of J-PARC Main Ring after Several Years of Operation impedance, cavity, ion, synchrotron 107
 
  • M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura, Japan
  • E. Ezura, K. Hasegawa, K. Takata
    KEK, Tokai, Ibaraki, Japan
  • K. Hara, C. Ohmori, M. Toda, M. Yoshii
    KEK/JAEA, Ibaraki-Ken, Japan
  • T. Sato, M. Yamamoto
    JAEA, Ibaraki-ken, Japan
  
  J-PARC 3 GeV RCS and 50 GeV Synchrotron (MR) employ RF cavities loaded with Magnetic Alloy (MA) cores to generate a high field gradient. The RF cavities in RCS use MA un-cut cores. On the other hand, the RF cavities in MR employ MA cut cores to increase the Q-value from 0.6 to 26. We observed the impedance reductions of all MR RF cavities during several years operation. Opening the RF cavities, we found that the impedance reductions were resulting from corrosion on the cut and polished surfaces of MA cores. Before installation of the RF cavities, we had 1000 and 2000 hours long tests at a test stand. We didn't observe the impedance reduction related to the corrosion on the MA core cut surfaces at the test stand. The only difference between the test stand and MR is the quality of cooling water. The MR cooling water contains copper ions for example from copper hollow conductors of the main magnets. We report the influence of the copper ions to the corrosion on the MA core cut surface. We also show plans how to solve the issue of MA core cut surface corrosion.  
 
MOPC036 Design of RF Cavity for Compact 9 MeV Cyclotron cavity, cyclotron, simulation, acceleration 151
 
  • H.S. Song, J.-S. Chai, H.W. Kim, B.N. Lee, J.H. Oh
    SKKU, Suwon, Republic of Korea
  
  The number of PET facility is rapidly increasing worldwide. To get PET image, circular accelerator such as cyclotron is needed. Compact 9 MeV H-cyclotron, which has a diameter of 1.25m is being designed at Sungkyunkwan University starting from July 2010 for getting F-18. It is expected to be constructed by next year. In this paper, RF system of 9 MeV cyclotron including design processes and detail analysis of result is reported. RF system mainly describes RF cavity design.  
 
MOPC049 Bead-pull Test Bench for Studying Accelerating Structures at RHUL cavity, rfq, quadrupole, controls 187
 
  • S. Molloy
    ESS, Lund, Sweden
  • R. Ainsworth, G.E. Boorman
    Royal Holloway, University of London, Surrey, United Kingdom
  • C. Gabor
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  • A. Garbayo
    AVS, Eibar, Gipuzkoa, Spain
  • A.P. Letchford
    STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
  • A. Lyapin
    JAI, Egham, Surrey, United Kingdom
  • P. Savage
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
  
  A bead-pull test stand has been constructed at Royal Holloway, University of London (RHUL) with the ability to provide electric field profile measurements along five degrees of freedom using the perturbation method. In this paper, we present example measurements using the test bench which include a field flatness profile of a 324MHz four vane Radio Frequency Quadrupole (RFQ) model designed as part of the Front End Test Stand (FETS) development at Rutherford Appleton Laboratory (RAL). Mechanical and operational details of the apparatus will also be described, as well as future plans for the development and usage of this facility.  
 
MOPC064 Upgrade and Commissioning of the 88-Inch Cyclotron Final Power Amplifier cyclotron, ion, impedance, cathode 229
 
  • M. Kireeff Covo, D.F. Byford, P.W. Casey, A. Hodgkinson, S. Kwiatkowski, C.M. Lyneis, L. Phair, A. Ratti, C.P. Reiter
    LBNL, Berkeley, California, USA
  
  Funding: This work was supported by the Director, Office of Science, Office of High Energy and Nuclear Physics, Division of Nuclear Physics, U.S. Department of Energy under Contract DE-AC02-05CH11231.
The RF system of the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory is a resonant system based on the quarter-wave cantilever type resonating structure. Power is fed to the Dee from the anode of the 500 kW RCA 6949 tetrode tube operating in grounded cathode configuration, which is capacitively coupled to the side of the Dee stem. The tube is obsolete and makes its continued use impractical. A new final power amplifier was designed and built using the commercially available tube Eimac 4W150,000E. The new amplifier was successfully commissioned and has been reliable and easy to operate. An overview of the system upgrade and details of the commissioning will be presented. 		 
 
MOPC083 Structural Mechanics of Superconducting CH Cavities cavity, simulation, controls, linac 268
 
  • M. Amberg, K. Aulenbacher
    HIM, Mainz, Germany
  • W.A. Barth, S. Mickat
    GSI, Darmstadt, Germany
  • M. Busch, F.D. Dziuba, H. Podlech, U. Ratzinger
    IAP, Frankfurt am Main, Germany
  
  The superconducting CH-structure (Crossbar-H-mode) is a multi-cell drift tube cavity for the low and medium energy range operated in the H21-mode, which has been developed at the Institute for Applied Physics (IAP) of Frankfurt University. With respect to different high power applications two types of superconducting CH-structures (f = 325 MHz, β = 0.16, seven cells and f = 217 MHz, β = 0.059, 15 cells) are presently under construction and accordingly under development. The structural mechanical simulation is a very important aspect of the cavity design. Furthermore, several simulations with ANSYS Workbench have been performed to predict the deformation of the cavity walls due to the cavity cool-down, pressure effects and mechanical vibrations. To readjust the fast frequency changes in consequence of the cavity shape deformation, a new concept for the dynamic frequency tuning has been investigated, including a novel type of bellow-tuner.  
 
MOPC109 Suppression of Coupler Kicks in 7-Cell Main Linac Cavities for Cornell's ERL cavity, linac, emittance, simulation 331
 
  • N.R.A. Valles, M. Liepe, V.D. Shemelin
    CLASSE, Ithaca, New York, USA
  
  Funding: Supported by NSF award DMR-0807731
Cornell is developing a 5 GeV Energy Recovery Linac operating at 100 mA with very small emittances (~30 pm at 77 pC bunch charge) in the horizontal and vertical directions. We investigate the effect of the fundamental RF power couplers of the main linac SRF cavities on the beam using the ACE3P software package. The cavities in the ERL main linac will be operated at very high loaded quality factors of up to 6.5·107, corresponding to a full bandwidth of only 20 Hz. Cavity microphonics will detune the cavities by more than one bandwidth during operation, thereby causing a time dependent change of the coupler kick in addition to its fast oscillation at the RF frequency. In order to investigate the dependence of the coupler kick on the cavity frequency, we calculate the coupler kick given to the beam for the case of a detuned RF cavity. We show that a compensation stub geometry located opposite to the input coupler port can be optimized to reduce the overall kick given to the beam and the emittace growth caused by its time dependence. 		 
 
MOPC123 Temperature Dependent Microphonics in the BNL Electron Cooler* cavity, electron, linac, cryogenics 370
 
  • P. Jain
    Stony Brook University, Stony Brook, USA
  • I. Ben-Zvi, C. Schultheiss
    BNL, Upton, Long Island, New York, USA
  
  An R&D Energy Recovery Linac (ERL), to be used in the BNL electron cooler, has been operational in a developmental setting. The ERL requires a cryogenic system to supply cooling to a superconducting RF gun and the 5-cell superconducting RF cavity system that is kept cold at 2K. The 2K superfluid bath is produced by pumping on the bath using a sub-atmospheric warm compression system. During a test run in October 2010, a resonance peak corresponding to a noise of 30 Hz was observed at 1.88K. This noise peak, present at all temperatures below 2K, is assumed to be of mechanical origin from the vibration of the cryopump. Another resonance noise peak of 16 Hz, characteristic of the system, was observed at 1.98K, which shifted towards the 30 Hz peak as the temperature of the cryostat varied from 1.98K to 1.88K. The 16 Hz resonance peak upon hitting the 30 Hz resonance peak, sets a resonance condition, thereby the 30 Hz peak getting amplified by more than five times. In this paper we explore the origin of the temperature dependent 16 Hz resonance peak and give a physical explanation of the resonance.  
 
MOPC132 Influences of the Inner-conductor on Microwave Characteristics in an L-band Relativistic Backward-wave Oscillator* simulation, plasma, space-charge, coupling 388
 
  • X.J. Ge, L. Liu, B.L. Qian, J. Zhang, H.H. Zhong
    National University of Defense Technology, Changsha, Kaifu District, People's Republic of China
  
  Funding: College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073, People’s Republic of China. *gexingjun230230@yahoo.com.cn
The influences of the inner-conductor on microwave characteristics in an L-band relativistic backward-wave oscillator (RBWO) are investigated theoretically and experimentally. The numerical results show that the resonance frequency decreases obviously with the increase in the inner-conductor radius. To verify the above conclusions, an L-band coaxial RBWO is investigated in detail with particle-in-cell (PIC) code. It is shown that the frequency is lowered from 1.63 GHz to 1.51 GHz when the inner-conductor radius increases from 0.5 cm to 2.5 cm. And the efficiency varies in the range of 35.4-27.7%. Furthermore, experiments are carried out at the Torch-01 accelerator. When the diode voltage is 887.6 kV and the current is 7.65 kA, the radiated microwave with frequency of 1.61 GHz, power of 2.13 GW and efficiency of 31.3% is generated. It is found that the frequency decreases from 1.64 GHz to 1.58 GHz when the inner-conductor radius increases from 0.5 cm to 1.5 cm. And the efficiency varies in the range of 31.3-29.8%. 		 
 
MOPC140 Phase and Frequency Locked Magnetrons for SRF Sources controls, cavity, shielding, SRF 406
 
  • M.L. Neubauer, M.A.C. Cummings, A. Dudas, R.P. Johnson, R. Sah
    Muons, Inc, Batavia, USA
  • A. Moretti, M. Popovic
    Fermilab, Batavia, USA
  
  Typically, high power sources for accelerator applications are multi-megawatt microwave tubes that may be combined together to form ultra-high-power localized power stations. The RF power is then distributed to multiple strings of cavities through high power waveguide systems which are problematic in terms of expense, efficiency, and reliability. Magnetrons are the lowest cost microwave source in dollars/kW, and they have the highest efficiency (typically greater than 85%). However, the frequency stability and phase stability of magnetrons are not adequate, when magnetrons are used as power sources for accelerators. Novel variable frequency cavity techniques have been developed which will be utilized to phase and frequency lock magnetrons, allowing their use for either individual cavities, or cavity strings. Ferrite or YIG (Yttrium Iron Garnet) materials will be attached in the regions of high magnetic field of radial-vaned, π−mode structures of a selected ordinary magnetron. The microwave characteristics of several materials have been tested with magnetic fields to control the frequency of the magnetron. These results will be presented and an optimum material chosen.  
 
MOPC153 Design and Implementation of Automatic Cavity Resonance Frequency Measurement and Tuning Procedure for FLASH and European XFEL Cryogenic Modules cavity, controls, klystron, LLRF 439
 
  • V. Ayvazyan, W. Koprek, D. Kostin, G. Kreps
    DESY, Hamburg, Germany
  • Z. Geng
    SLAC, Menlo Park, California, USA
  
  The superconducting cavities in FLASH and European XFEL should be tuned to the frequency of 1.3 GHz after cool down and adjusted to initial frequency before warm up by stepper motor tuners. The initial frequency is 300 kHz far from the operating frequency (1.3 GHz) to remove mechanical hysteresis of the tuner. The cavities should be relaxed to initial frequency to avoid a plastically deformation. In framework of digital low level RF and DOOCS control systems we have developed a simple automatic procedure for the remote resonance frequency measurement and simultaneous remote tuning for all cavities which are driven from the single klystron. The basic idea is based on frequency sweeping both for driving klystron and for generation of local oscillator frequency with constant RF frequency from master oscillator. The developed system has been used during FLASH commissioning in spring 2010 and is in use for cavity and cryogenic module test stands for European XFEL at DESY.  
 
MOPC160 Digital LLRF for IFMIF-EVEDA cavity, LLRF, controls, rfq 457
 
  • A. Salom, A. Arriaga, J.C. Calvo, I. Kirpitchev, P. Méndez, D. Regidor, M. Weber
    CIEMAT, Madrid, Spain
  • A. Mosnier
    CEA/IRFU, Gif-sur-Yvette, France
  • F. Pérez
    CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
  
  The IFMIF-EVEDA project aims to build a prototype accelerator (deuteron, 9MeV, 125mA) to be located at Rokkasho, Japan, for design validation of the IFMIF Accelerator. CIEMAT from Madrid, Spain, is in charge of providing the RF systems for this prototype accelerator. The LLRF will adjust the phase and amplitude of the RF drive and the resonance frequency of the cavities. This paper summarizes its main characteristics and Control System integrated in EPICS. The hardware is based on a commercial FPGA board, an analog front end and a local timing system. Each LLRF system will control and diagnose two RF chains and it will handle the RF fast Interlocks (vacuum, arcs, reflected power and multipacting). A specific LLRF will be developed for the special case of the RFQ cavity, with one Master LLRF and three Slave LLRFs to feed the 8 RF chains of the cavity. The conceptual design and other capabilities of the system like automatic conditioning, frequency tuning for startup and field flatness of the RFQ, etc, will be shown in this paper together with the first low power test results of the LLRF prototype and the performance of the Control System.  
 
MOPO022 Precision Beam Instrumentation and Feedback-Based Beam Control at RHIC feedback, coupling, acceleration, controls 526
 
  • M.G. Minty, W. Fischer, H. Huang, R.L. Hulsart, C. Liu, Y. Luo, G.J. Marr, A. Marusic, K. Mernick, R.J. Michnoff, V. Ptitsyn, G. Robert-Demolaize, T. Roser, V. Schoefer, S. Tepikian, M. Wilinski
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In this report we present advances in beam instrumentation required for feedback-based beam control at the Relativistic Heavy Ion Collider (RHIC). Improved resolution has contributed to enabling now routine acceleration with multiple feedback loops. Better measurement and control of the beam’s properties have allowed acceleration at a new working point and have facilitated challenging experimental studies. 		 
 
MOPO028 Modal Analysis and Measurement of Water Cooling Induced Vibrations on a CLIC Main Beam Quadrupole Prototype* quadrupole, ground-motion, controls, damping 541
 
  • K. Artoos, C.G.R.L. Collette, M. Esposito, P. Fernandez Carmona, M. Guinchard, S.M. Janssens, R. Leuxe, M. Modena, R. Moron Ballester, M. Struik
    CERN, Geneva, Switzerland
  • G. Deleglise, A. Jeremie
    IN2P3-LAPP, Annecy-le-Vieux, France
  
  Funding: The research leading to these results has received funding from the European Commission under the FP7 Research Infrastructures project EuCARD, grant agreement no. 227579.
To reach the Compact Linear Collider (CLIC) design luminosity, the mechanical jitter of the CLIC main beam quadrupoles should be smaller than 1.5 nm integrated root mean square (r.m.s.) displacement above 1 Hz. A stiff stabilization and nano-positioning system is being developed but the design and effectiveness of such a system will greatly depend on the stiffness of the quadrupole magnet which should be as high as possible. Modal vibration measurements were therefore performed on a first assembled prototype magnet to evaluate the different mechanical modes and their frequencies. The results were then compared with a Finite Element (FE) model. The vibrations induced by water-cooling without stabilization were measured with different flow rates. This paper describes and analyzes the measurement results. 		 
 
MOPS002 Mitigation of Space Charge and Nonlinear Resonance Induced Beam Loss in SIS100 beam-losses, space-charge, acceleration, simulation 589
 
  • G. Franchetti
    GSI, Darmstadt, Germany
  
  The control of beam loss in SIS100 is essential for avoiding vacuum instability and guarantee the delivery of the foreseen beam intensity. On the other hand simulations show that the simultaneous presence of space charge and lattice resonances creates during 1 second cycle a progressive beam loss exceeding the limit of 5%. Until now the mechanism of periodic resonance crossing were suspected to be, in conjunction with pure dynamic aperture effects, at the base of the beam loss. In this proceeding we present the state of the art in the beam loss prediction and we prove that the periodic resonance crossing is the deteriorating mechanism, and show that the compensation of a relevant resonance intercepting the space charge tune spread sensibly mitigate the beam loss. A short discussion on beam loss during acceleration is addressed as well.  
 
MOPS003 Coherent Beam-beam Resonances in SuperB with Asymmetric Rings luminosity, simulation, collider, dynamic-aperture 592
 
  • M. Zobov
    INFN/LNF, Frascati (Roma), Italy
  • Y. Zhang
    IHEP Beijing, Beijing, People's Republic of China
  
  One of the latest options of SuperB foresees exploiting rings with unequal circumferences. In such a configuration additional coherent beam-beam resonances can arise. In this paper we discuss the possible impact of the resonances on beam dynamics in SuperB, maximum achievable tune shifts and working point choice.  
 
MOPS012 Optics Considerations for Lowering Transition Energy in the SPS optics, injection, emittance, lattice 619
 
  • H. Bartosik, G. Arduini, Y. Papaphilippou
    CERN, Geneva, Switzerland
  
  Beam stability for high intensity LHC beams in the SPS can be improved by increasing the slippage factor, i.e. reducing the transition energy. In this paper, possible ways of modifying the optics of the SPS for lower transition energy are reviewed. In particular, a threefold increase of the slippage factor at injection can be achieved by decreasing the integer part of the tunes by 6 units. The properties of this new low-transition optics are compared with the nominal SPS optics, including working point and resonance behavior. Possible limitations are discussed.  
 
MOPS014 Tune and Space Charge Studies for High-brightness and High-intensity Beams at CERN PS emittance, space-charge, injection, beam-losses 625
 
  • S.S. Gilardoni, S. Aumon, J. Brenas, P. Freyermuth, A. Huschauer, R. Maillet, E. Matli, R.R. Steerenberg, B. Vandorpe
    CERN, Geneva, Switzerland
  • E. Benedetto
    National Technical University of Athens, Zografou, Greece
  
  The current 1.4 GeV CERN PS injection energy limits the maximum intensity required by the future High-Luminosity LHC. The bare-machine large chromaticity combined with the non-linear space charge forces make high-brightness and high-intensity beams crossing betatron resonances along the injection flat bottom, inducing transverse emittance blow-up and beam losses. A scan of the working point plane {Qx,Qy} was done in order to identify beam destructive resonances, in the framework of a possible 2 GeV injection energy upgrade which would reduce the space charge effect on the tune. Experiments were carried out in order to review the maximum space charge tune shift for which no transverse emittance blow-up is observed. The results of measurements and simulations will be presented in this paper.  
 
MOPS016 First Observations of Intensity-dependent Effects for Transversally Split Beams extraction, space-charge, booster, coupling 631
 
  • S.S. Gilardoni, M. Giovannozzi
    CERN, Geneva, Switzerland
  
  During the commissioning of the CERN PS Multi-Turn Extraction (MTE) tests with different beam intensities were performed. The beam current before transverse splitting was varied and the properties of the five beamlets obtained by crossing the fourth-order horizontal resonance were studied. A clear dependence of the beamlets’ parameters on the total intensity was found, which is a first observation of intensity-dependent effects for such a peculiar beam type. The experimental results are presented and discussed in this paper.  
 
MOPS018 Simulation and Measurement of Half Integer Resonance in Coasting Beams on the ISIS Ring emittance, simulation, injection, space-charge 637
 
  • C.M. Warsop
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  • D.J. Adams, B. Jones, B.G. Pine, H. V. Smith, R.E. Williamson
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  
  ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on an 800 MeV rapid cycling synchrotron (RCS), which provides 3·1013 protons per pulse at 50 Hz, corresponding to a beam power of 0.2 MW. In common with many lower energy, high intensity proton rings, a key loss mechanism on ISIS is half integer resonance under space charge. This paper summarises experimental and simulation work studying half integer resonance in a “2D” coasting beam in the ISIS ring: understanding this is an essential prerequisite for explaining the more complicated case of RCS operation. For coasting beam experiments, the ring is reconfigured to storage ring mode with RF off and main magnets powered on DC current only. A 70 MeV beam is injected, painted appropriately, and manipulated so as to approach resonance. Understanding how the resonant condition develops is central to explaining observations, so realistic simulations of resonance, including injection, ramping of intensity and tunes are being developed. Results from the ORBIT code are presented and compared with experimental and theoretical results. Finally, future plans are summarized.  
 
MOPS027 Stability Charts for the IFMIF SRF-Linac emittance, linac, SRF, space-charge 658
 
  • W. Simeoni, N. Chauvin
    CEA/IRFU, Gif-sur-Yvette, France
  • A. Mosnier, P.A.P. Nghiem, D. Uriot
    CEA/DSM/IRFU, France
  
  Among the most recent projects, the IFMIF-EVEDA accelerators break the record of high intensity, leading to a multi-MW beam power at relatively low energy. The concern for such accelerated beams is the predominance of the self-field energy upon the beam energy. In these conditions, the space charge effect is at its maximum, which triggers different nonlinear mechanisms implying emittance growth, halo formation and sudden particle lost. In this proceeding we show the stability charts constructed for the IFMIF SRF-Linac, with which are identified the collective space charge resonances responsible of transverse-longitudinal emittance exchange and emittance growth.  
 
MOPS045 Coupling Impedance of Rough Resistive Pipe* impedance, coupling, vacuum, wakefield 700
 
  • M. Ivanyan, V.M. Tsakanov
    CANDLE, Yerevan, Armenia
  
  A new version of modelling of the surface roughness impact by thin dielectric layer in the round resistive beam pipe is suggested. The calculation method of coupled resistive-roughness impedance is developed.  
 
MOPS064 Longitudinal Beam Stability and Related Effects at the ALBA Storage Ring kicker, impedance, vacuum, injection 748
 
  • T.F. Günzel
    CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
  
  The risk of longitudinal instabilities excited by narrowband and broadband resonator impedance was studied. A campaign for the search of modes trapped in vacuum chamber elements of the ALBA storage ring via electromagnetic simulation was initiated. Several critical vacuum elements in the ring like the vertical scraper, the injection and feedback kickers were identified. The outlets of the injection kicker had to be protected with RF-fingers whereas the scraper only produces dangerous modes in the withdrawn state, both do not pose a real problem. However, the calculated power distribution generated in the feedback kickers could be an obstacle for reaching the nominal current of 400mA. Furthermore, the budget of Z(n)/n of the storage ring was computed and checked on the risk of microwave instability using the Boussard criterion.  
 
MOPS083 Update on Electron Cloud Mitigation Studies at Cesr-TA* electron, wiggler, positron, photon 796
 
  • J.R. Calvey, M.G. Billing, J.V. Conway, G. Dugan, S. Greenwald, Y. Li, X. Liu, J.A. Livezey, J. Makita, R.E. Meller, M.A. Palmer, S. Santos, R.M. Schwartz, J.P. Sikora, C.R. Strohman
    CLASSE, Ithaca, New York, USA
  • S. Calatroni, G. Rumolo
    CERN, Geneva, Switzerland
  • K. Kanazawa, Y. Suetsugu
    KEK, Ibaraki, Japan
  • M.T.F. Pivi, L. Wang
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by the US National Science Foundation (PHY-0734867) and Department of Energy (DE-FC02-08ER41538)
Over the course of the past three years, the Cornell Electron Storage Ring (CESR) has been reconfigured to serve as a test facility for next generation particle accelerators. A significant part of this program has been the installation of several diagnostic devices to measure and quantify the electron cloud effect, a potential limiting factor in these machines. In particular, more than 30 Retarding Field Analyzers (RFAs) have been installed in CESR. These devices measure the local electron cloud density and energy distribution, and can be used to evaluate the efficacy of different cloud mitigation techniques. This paper will provide an overview of RFA results obtained at CesrTA over the past year, including measurements taken as function of bunch spacing and wiggler magnetic field. Understanding these results provides a great deal of insight into the behavior of the electron cloud. 		 
 
TUOAB01 Lattice Design of a Very Low-emittance Storage Ring for SPring-8-II lattice, dynamic-aperture, emittance, alignment 942
 
  • Y. Shimosaki, K.K. Kaneki, T. Nakamura, H. Ohkuma, J. Schimizu, K. Soutome, M. Takao
    JASRI/SPring-8, Hyogo-ken, Japan
  
  The design work for an upgrade project of the SPring-8, the SPring-8-II, is in progress. Its ultimate goal is to provide a superior brilliance of photons by reducing emittance of electrons until a diffraction limit. A multi-bend lattice has been adopted for the emittance reduction; a double-bend lattice (natural emittance of 2000 pmrad at 6 GeV), a triple-bend lattice (400 pmrad) and a quadruple-bend lattice (170 pmrad) were designed step by step for studying its feasibility*. For an additional emittance reduction, beam dynamic issues for a sextuple-bend lattice have been examined for the first candidate. In this case, the natural emittance is about 70 pmrad. The dynamic aperture has been enlarged by studying beam dynamic phenomena caused by nonlinear dispersion, nonlinear chromaticity, nonlinear resonance, etc., and by optimizing linear and nonlinear optics. The lattice design for the coming upgrade of SPring-8 will be presented in detail.
* K. Soutome et al., "Design Study of a very Low-emittance Storage Ring for the Future Upgrade Plan of SPring-8", Proc. of IPAC10, WEPEA032, p. 2555 (2010). 		 
slides icon Slides TUOAB01 [4.812 MB]  
 
TUPC062 Electron Beam Energy Measurement at the Australian Synchrotron Storage Ring storage-ring, electron, synchrotron, scattering 1138
 
  • M.J. Boland
    ASCo, Clayton, Victoria, Australia
  • H. Panopoulos, R.P. Rassool, K.P. Wootton
    The University of Melbourne, Melbourne, Australia
  
  The technique of resonant spin depolarization was used to precisely measure the electron beam energy in the storage ring at the Australian Synchrotron. A detector and data acquisition system dedicated to the measurement were developed. Using the system, the long term energy stability of the storage ring was monitored and a mechanical realignment of the ring was clearly seen in the energy data. Details of the parameters used to optimize the measurement are also discussed.  
 
TUPC073 Emittance Variation Dependence on Resonance Extraction Parameters at ELSA emittance, extraction, sextupole, septum 1168
 
  • S. Zander, O. Boldt, F. Frommberger, W. Hillert, O. Preisner
    ELSA, Bonn, Germany
  
  Funding: Funded by the DFG within the SFB / TR 16.
The Electron Stretcher Facility ELSA consists of several accelerator stages, the last one being a stretcher ring providing a beam of polarized electrons with an energy of up to 3.5~GeV. In order to guarantee a high duty cycle, a slow extraction via a third integer resonance is applied to the stretcher ring. The emittance of the extracted beam as well as the efficiency of the extraction process depend on different parameters as the sextupole strength being necessary for the excitation of the third integer resonance or the adjusted tune. In order to optimize the quality of the extracted beam, an accurate comprehension of the influence of these parameters is indispensable. Beam profiles are detected using dedicated synchrotron light monitors optimized for low intensities. The emittance was investigated by the method of quadrupole scan. The experimental studies are accompanied by numerical simulation studies. The results of the change of the emittance depending on different resonance extraction setups obtained by the experimental as well as by the theoretical studies will be presented. 		 
 
TUPC077 Investigations on High Sensitive Sensor Cavity for Longitudinal and Transversal Schottky for the CR at FAIR cavity, coupling, dipole, simulation 1180
 
  • M. Hansli, A. Angelovski, R. Jakoby, A. Penirschke
    TU Darmstadt, Darmstadt, Germany
  • W. Ackermann, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  • P. Hülsmann
    GSI, Darmstadt, Germany
  
  Funding: Funded by the Federal Ministry of Education and Research (BMBF): 06DA90351
For the Collector Ring (CR) at the FAIR (Facility for Antiproton and Ion Research) accelerator complex a sensitive Schottky sensor is required. The CR covers different modes of operation, like pre-cooling of antiprotons at 3 GeV, pre-cooling of rare isotope beams at 740 MeV/u and an isochronous mode for mass measurements. For longitudinal Schottky measurements the concept of a resonant cavity had been introduced [Hansli2011]. Due to limited space inside the ring, the integration of transversal Schottky analysis into this cavity is desired. In this paper the demands and required changes to implement also transversal Schottky measurements are discussed. An analysis of the expected signal characteristics featuring equivalent circuit is shown, as well as numerical full wave simulations of the cavity.
* M. Hansli, A. Penirschke, R. Jakoby, W. Kaufmann, W. Ackermann, T. Weiland, "Conceptual Design of a High Sensitive Versatile Schottky Sensor for the Collector Ring at FAIR", DIPAC2011. 		 
 
TUPC080 Pickup Design with Beta Matching pick-up, impedance, simulation, kicker 1189
 
  • J.A. Tsemo Kamga, W.F.O. Müller, K.K. Stavrakakis, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  
  Funding: Work supported by GSI
The main goal of this project is to investigate the Schottky noise of an ion beam in the frequency range from 3 to 5 GHz. In order to accomplish this task, a pickup design is required. For an efficient study of this Schottky noise the pickup sensitivity for low beta must be increased. A design for such a problem has been developed by McGinnis for a fixed beam velocity but can also be used for variable beta by using a tunable material (ferroelectric) inside the waveguide. Since such tunable materials like for instance BST (Barium Strontium Titanate) are lossy, the impact of dielectric losses on the pickup sensitivity will also be investigated in this work. Additionally to the classical parameter studies where multiple simulation runs based on the original numerical model are initiated to characterize the various design parameters it is also possible to utilize a reduced model instead. In particular one is interested in a fast evaluation of the frequency response while taking also material variations into account. In this work, a multivariate parameterized dynamical system is set up and used complementary to the full model for the required beam characterization. 		 
 
TUPC089 New Digital NMR System for an Old Analyzing Magnet controls, power-supply, cyclotron, feedback 1215
 
  • Z. Kormány, I. Ander
    ATOMKI, Debrecen, Hungary
  
  The analyzing magnet of the ATOMKI cyclotron measures the beam energy with high precision and can lower its energy spread to ~5x10-4. The highly stable magnetic field is achieved by a NMR-feedback in the control loop of the power supply. The original analog system was designed and built over 25 years ago applying mainly obsolete, partly nowadays unavailable components. Maintaining and keeping the system running required increasing efforts every year. A new digital system has been developed to replace the old one. Except the high-frequency signal domain (HF oscillator and preamplifier) it performs every processing digitally. Its heart is a mixed-signal microcontroller that generates the signals for the NMR-probe, measures the amplitude and frequency of the oscillation, evaluates the demodulated signal and controls the power supply. A fast NMR-pulse detection algorithm was developed; as a result the embedded program can perform all measuring, detecting and controlling tasks in real-time. A PC connects to the controller, sends commands and displays the received signals and status data. The control software allows easy handling of the complete system with nearly automated operation.  
 
TUPC107 Some Preliminary Experiments using LIBERA BPMs in BEPCII* coupling, injection, kicker, feedback 1266
 
  • Y. Zhang, H.Z. Ma, J. Yue
    IHEP Beijing, Beijing, People's Republic of China
  
  Funding: Supported by the National Natural Science Foundation of China (10805051)
There are total 16 LIBERA BPMs in BEPCII, which is a double ring e+e− collider. The turn-by-turn BPMs serve as only tune measurement system in most cases during normal operation. We tried to do some more machine study using them: the local coupling parameter at the BPM, the resonance driving term, the decoherence parameter which could be used to calibrate the strength of octupole in the ring. We also compare the difference from the different exciting method: single time kick with injection kicker or sinusoidal kick with feedback system. 		 
 
TUPC141 LHC Beam Loss Pattern Recognition beam-losses, monitoring, proton, collider 1353
 
  • A. Marsili, E.B. Holzer, P.M. Puzo
    CERN, Geneva, Switzerland
  
  One of the systems protecting CERN's Large Hadron Collider (LHC) is the Beam Loss Monitoring system (BLM). More than 3600 monitors are installed around the ring. The beam losses are permanently integrated over 12 different time intervals (from 40 microseconds to 84 seconds). When any loss exceeds the thresholds defined for the integration window, the beam is removed from the machine. Understanding the origin of a beam loss is crucial for machine operation, as it can help to avoid a repeat of the same scenario. The signals read from given monitors can be considered as entries of a vector. This article presents how a loss map of unknown cause can be decomposed using vector based analysis derived from well-known loss scenarios. The algorithms achieving this decomposition are described, as well as the accuracy of the results.  
 
TUPC159 Energy Measurements with Resonant Spin Depolarisation at Diamond electron, storage-ring, feedback, quadrupole 1404
 
  • I.P.S. Martin, M. Apollonio, R.T. Fielder, G. Rehm
    Diamond, Oxfordshire, United Kingdom
  • R. Bartolini
    JAI, Oxford, United Kingdom
  
  A precise knowledge of the electron beam energy is critical for the accurate determination of many light source parameters, such as momentum compaction factor, natural chromaticity, energy stability and undulator spectra. In common with other facilities, a method of energy measurement based on resonant spin depolarisation has been developed at Diamond. In this paper we report on progress towards storage ring characterisation using this method, as well as describing the diagnostics developments that have enabled these measurements to be made.  
 
TUPC170 Resonant TE Wave Measurements of Electron Cloud Densities at CesrTA cavity, electron, plasma, damping 1434
 
  • J.P. Sikora, M.G. Billing, M.A. Palmer, K.G. Sonnad
    CLASSE, Ithaca, New York, USA
  • B.T. Carlson
    CMU, Pittsburgh, Pennsylvania, USA
  • S. De Santis
    LBNL, Berkeley, California, USA
  • K.C. Hammond
    Harvard University, Cambridge, Massachusetts, USA
  
  Funding: This work is supported by the US National Science Foundation PHY-0734867, and the US Department of Energy DE-FC02-08ER41538.
The Cornell Electron Storage Ring has been reconfigured as a test accelerator (CesrTA). Measurements of electron cloud densities have been made at CesrTA using the TE Wave transmission technique. However, interpretation of the data based on single pass transmission is problematic because of the reflections and standing waves produced by discontinuities in the beam pipe - from pumps, bellows, etc. that are normally present in an accelerator vacuum chamber. An alternative model is that of a resonant cavity, formed by the beampipe and its discontinuities. The theory for the measurement of plasma densities in cavities is well established. This paper will apply this theory to electron cloud measurements, present some simplified measurements on waveguide, and apply this model to the interpretation of some of the data taken at CesrTA. 		 
 
TUPS085 Mass Production Report of C-band Choke Mode Accelerating Structure and RF Pulse Compressor coupling, cavity, acceleration, electron 1737
 
  • S. Miura, T. Hashirano, F. Inoue, K. Okihira
    MHI, Hiroshima, Japan
  • T. Inagaki
    RIKEN/SPring-8, Hyogo, Japan
  • H. Maesaka, T. Shintake
    RIKEN Spring-8 Harima, Hyogo, Japan
  
  RIKEN and JASRI already completed the construction of XFEL/SPring8. Recently the facility was named “SACLA” (SPring-8 Angstrom Compact Free Electron LAser). The commissioning team succeeded in acceleration of 8 GeV electron beam and observation of the undulator light of 0.8 angstrom wavelength in March 2011. Now the accelerator is stably operated for the XFEL commissioning. In this project, a C-band (5712 MHz) choke mode accelerating structures and C-band RF pulse compressors are employed to obtain a high acceleration gradient of more than 35 MeV/m. We completed the fabrication of 128 accelerating structures, 64 RF pulse compressors, and 64 units of waveguide components and conducted RF measurements on them until May 2010. We report the result of the mass-production of these 64 C-Band units.  
 
TUPZ035 RHIC Polarized Proton Status and Operation Highlights polarization, feedback, emittance, controls 1888
 
  • H. Huang, L. A. Ahrens, I.G. Alekseev, E.C. Aschenauer, G. Atoian, M. Bai, A. Bazilevsky, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, A. Dion, K.A. Drees, W. Fischer, J.W. Glenn, X. Gu, L.T. Hoff, C. Liu, Y. Luo, W.W. MacKay, Y. Makdisi, G.J. Marr, A. Marusic, F. Méot, M.G. Minty, C. Montag, J. Morris, A. Poblaguev, V. Ptitsyn, G. Robert-Demolaize, T. Roser, W.B. Schmidke, V. Schoefer, D. Smirnov, S. Tepikian, J.E. Tuozzolo, G. Wang, K. Yip, A. Zaltsman, A. Zelenski, S.Y. Zhang
    BNL, Upton, Long Island, New York, USA
  • D. Svirida
    ITEP, Moscow, Russia
  
  RHIC op­er­a­tion as the po­lar­ized pro­ton col­lid­er pre­sents unique chal­lenges since both lu­mi­nos­i­ty and spin po­lar­iza­tion are im­por­tant. A lot of up­grades and mod­i­fi­ca­tions have been made since last po­lar­ized pro­ton op­er­a­tion. A 9 MHz rf sys­tem has been in­stalled to im­prove lon­gi­tu­di­nal match at in­jec­tion and to in­crease lu­mi­nos­i­ty. A ver­ti­cal sur­vey of RHIC was per­formed be­fore the run to get bet­ter mag­net align­ment. The orbit con­trol has also been im­proved this year. AGS po­lar­iza­tion trans­fer ef­fi­cien­cy is improved by a horizontal tune jump system. To pre­serve po­lar­iza­tion on the ramp, a new work­ing point was cho­sen with the ver­ti­cal tune near a third order res­o­nance. The orbit and tune control are essential for polarization preservation. To calibrate the polarization level at 250 GeV, polarized protons were accelerated up to 250GeV and decelerated back to 100GeV. The tune, orbit and chromaticity feedback is essential for this operation. The new record of luminosity was achieved with higher polarization at 250 GeV in this run. The overview of the changes and op­er­a­tion re­sults are pre­sent­ed in this paper.  
 
TUPZ039 Modelling of the AGS Using Zgoubi - Status dipole, multipole, quadrupole, simulation 1897
 
  • F. Méot, L. A. Ahrens, Y. Dutheil, J.W. Glenn, H. Huang, T. Roser, N. Tsoupas
    BNL, Upton, Long Island, New York, USA
  
  Models of the Alternating Gradient Synchrotron, based on stepwise ray-tracing methods using both mathematical modelling or field maps so to represent the optical elements, including the siberian snakes, are being developed based on stepwise ray-tracing numerical tools. The topic is introduced in earlier PAC and IPAC publications, a status is given here.  
 
WEZA01 Round Beam Collisions at VEPP-2000* luminosity, positron, lattice, betatron 1926
 
  • Y.M. Shatunov, D.E. Berkaev, A.N. Kirpotin, I. Koop, A.P. Lysenko, I. Nesterenko, E. Perevedentsev, Yu. A. Rogovsky, A.L. Romanov, P.Yu. Shatunov, D.B. Shwartz, A.N. Skrinsky, I. Zemlyansky
    BINP SB RAS, Novosibirsk, Russia
  
  The idea of round beams collision was proposed more than 20 years ago for the Novosibirsk Phi-factory design. It requires equal emittances, equal small fractional tunes, equal beta functions at the IP, no betatron coupling in the collider arcs. A 90° rotation at each passage of the transverse oscillation plane by means of solenoids in the interaction regions provides conservation of the longitudinal component of the angular moment. Thus the transverse motion becomes one-dimensional. Such a scheme helps to eliminate all betatron coupling resonances that are of crucial importance for beam-beam tune shift saturation and lifetime degradation. Only recently, the round beam concept was successfully tested at the electron-positron collider VEPP2000 at the energy of 510 MeV. Despite the low energy a high single bunch luminosity of 1031 cm-2s−1 was achieved together with a maximum tune shift as high as 0.1. At present the work is in progress to increase the energy of the collider to explore the range between 510 MeV and 1 GeV in collision.  
slides icon Slides WEZA01 [3.740 MB]  
 
WEPC015 Tuning Methods for HIMAC Multiple-energy Operation betatron, acceleration, beam-losses, synchrotron 2037
 
  • K. Katagiri, T. Furukawa, Y. Iwata, K. Noda, S. Sato, T. Shirai
    NIRS, Chiba-shi, Japan
  • K. Mizushima
    Chiba University, Graduate School of Science and Technology, Chiba, Japan
  • E. Takeshita
    Gunma University, Heavy-Ion Medical Research Center, Maebashi-Gunma, Japan
  
  Beam stability of multiple-energy operation at HIMAC synchrotron was improved for the fast raster-scanning irradiation. In order to improve the transverse stability, the working point of the betatron tune was investigated during one operation cycle. The signals were collected from the beam position monitor using a fast data-acquisition unit. The temporal evolution of the horizontal and vertical betatron tune was evaluated by using the short time Fourier transform. Analyzed results showed that variation of the betatron tune in the acceleration interval passed through the 3rd-order coupling resonance line, and it caused undesirable emittance growth. In order to keep the working point within the desirable operating region, the current pattern of the power supplies for the quadrupole magnets was corrected by using the variation of the betatron tune. The experimental results showed that the working point could be successfully stabilized, and the undesirable beam losses could be reduced during the acceleration interval.  
 
WEPC030 Measurement of Coupling Resonance Driving Terms in the LHC with AC Dipoles dipole, kicker, optics, quadrupole 2067
 
  • R. Miyamoto, R. Calaga
    BNL, Upton, Long Island, New York, USA
  • M. Aiba
    PSI, Villigen, Switzerland
  • R. Tomás, G. Vanbavinckhove
    CERN, Geneva, Switzerland
  
  Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP).
Transverse betatron coupling in the LHC is measured from Fourier analysis of turn-by-turn beam oscillations excited by AC dipoles. The use of the AC dipole for optics measurements induces a small systematic error which can be corrected with an appropriate data interpretation. An algorithm to apply this correction to the measurement of the coupling resonance driving terms is developed for the first time. This paper will review this new algorithm and present results of its application to the LHC. 		 
 
WEPC032 First Measurements of Higher Order Optics Parameters in the LHC simulation, optics, injection, kicker 2073
 
  • G. Vanbavinckhove
    NIKHEF, Amsterdam, The Netherlands
  • M. Aiba
    PSI, Villigen, Switzerland
  • R. Bartolini
    Diamond, Oxfordshire, United Kingdom
  • R. Calaga, R. Miyamoto
    BNL, Upton, Long Island, New York, USA
  • M. Giovannozzi, F. Schmidt, R. Tomás
    CERN, Geneva, Switzerland
  • E.H. Maclean
    JAI, Oxford, United Kingdom
  
  Higher order effects can play an important role in the performance of the LHC. Lack of knowledge of these parameters can increase the tune footprint and compromise the beam lifetime. First measurements of these parameters at injection and flattop have been conducted. Detailed simulations are compared to the measurements together with discussions on the measurement limitations.  
 
WEPC033 Decoupling Problem of Weakly Linear Coupled Double Mini-beta-y Lattice of TPS Storage Ring coupling, lattice, betatron, storage-ring 2076
 
  • H.-P. Chang, C.C. Chiang, M.-S. Chiu
    NSRRC, Hsinchu, Taiwan
  
  Three double mini-beta-y (DMBy) lattice design of the TPS storage ring is in progress to enhance the photon sources at three of the six long straight sections. For the estimation of Touschek beam lifetime, the TRACY code is used to calculate the momentum acceptance of the linear coupled TPS 3-DMBy lattice. The weak linear coupling was generated by adding some random skew quadrupoles at all quadrupole locations in order to create 1% coupling. Using the Teng’s symplectic rotation form in program may cause trouble in decoupling the one-turn coupled matrix. This report describes how we solve this decoupling problem and some useful references and comments are also presented.  
 
WEPC052 Spinor Based Calculation of Depolarizing Effects in Circular Lepton Accelerators synchrotron, polarization, lepton, photon 2130
 
  • O. Boldt, A. Dieckmann, F. Frommberger, W. Hillert
    ELSA, Bonn, Germany
  
  Funding: BMBF
The emission of synchrotron radiation strongly influences the beam dynamics in case of ultra relativistic leptons. When storing or accelerating leptons in circular accelerators, the acting magnetic field shows an oscillating behavior in the rest frame of the leptons. Its properties can be determined by a spectral analysis. The stochastic emission of synchrotron light leads to a line broadening within the magnetic field spectrum. This spectrum can be used to simulate depolarizing effects in circular accelerators. Our contribution will present a tracking based calculation of the mentioned spectrum and a spinor-based determination of the resulting population of the spin-up state. These calculations base on the lattice of the electron stretcher accelerator (ELSA, Bonn) and are confirmed by measurements of the polarization. 		 
 
WEPC053 Crossing of Depolarizing Resonances in Circular Electron Accelerators polarization, electron, closed-orbit, quadrupole 2133
 
  • W. Hillert, A. Balling, O. Boldt, A. Dieckmann, F. Frommberger
    ELSA, Bonn, Germany
  
  Funding: Supported by the German Research Foundation (DFG) through SFB/TR 16
In flat electron storage rings, only the vertical component of the beam polarization is preserved. During acceleration, the crossing of several depolarizing resonances may cause severe beam depolarization. Even in case of fast ramping speeds of up to 6 GeV/sec, first order effects like imperfection and intrinsic resonances have to be compensated by dedicated measures. At the accelerator facility ELSA, schemes like fast tune jumping and harmonic orbit correction are successfully applied on the fast energy ramp up to 3.2 GeV. Characteristics of the setup as well as the optimization efforts to improve the resonance compensation will be reported in detail. 		 
 
WEPC056 Beam Test of Slow Extraction from the ESR extraction, septum, sextupole, ion 2142
 
  • A. Dolinskii, C. Dimopoulou, O.E. Gorda, S.A. Litvinov, F. Nolden, M. Steck
    GSI, Darmstadt, Germany
  
  In the frame of a dedicated ESR machine development the conventional third order resonant slow extraction was theoretically investigated and experimentally tested. The possibility to extract a beam from the ESR by preparing a resonant closed orbit, which has strong nonlinear characteristics, was demonstrated. A third-integer resonance slow extraction has been adopted for the 100 MeV/u Ar beam.  
 
WEPC057 Estimation of the Dynamic Aperture by Transverse Beam Excitation with Noise Close to a Resonance dynamic-aperture, lattice, beam-losses, sextupole 2145
 
  • S. Sorge, G. Franchetti
    GSI, Darmstadt, Germany
  
  The present heavy ion synchrotron SIS-18 will be upgraded to be used as a booster for further synchrotrons being part of the FAIR project underway at GSI. Recently, a method was developed to measure the physical aperture of SIS-18 using transverse RF noise. This method is based on the transverse expansion of the beam with noise beyond the limiting aperture generating beam loss. The aperture was determined from the comparison of the resulting time evolution of the beam current in the machine with that obtained from a numerical simulation. In this study we attempt to apply this method to determine the dynamic aperture of SIS-18.  
 
WEPC059 Optimization of the Sextupole Scheme and Compensation of the Time-Dependent Field Errors during Slow Extraction from the Superconducting Synchrotron SIS300 extraction, sextupole, lattice, dipole 2151
 
  • A. Saa Hernandez, P.J. Spiller
    GSI, Darmstadt, Germany
  • U. Ratzinger
    IAP, Frankfurt am Main, Germany
  
  The SIS300 synchrotron, planned for the new Facility for Antiproton and Ion Research (FAIR) at GSI-Darmstadt, will become the first superconducting synchrotron worldwide using cos(θ) magnets for resonant slow extraction. A multi-objective optimization algorithm has been developed for the design of the non-linear magnet scheme. The optimization algorithm makes use of the analytical model for the slow extraction from Kobayashi, the analytical description of the resonance excitation and amplitude-dependent tune-shift from Bengtsson, and corrects the chromaticity in order to fulfill the Hardt condition. As a result, the placement of the chromatic and harmonic sextupole magnets in SIS300, the number of sextupole families and the gradients of these families have been optimized for a high efficiency slow extraction. The algorithm accounts also for the sextupole errors on the dipole magnets, compensating its effects. Furthermore, optimized time-dependent settings for the sextupole magnets are generated to compensate the persistent current decay occurring at slow extraction. Tolerances for the magnets are set for the limits where the compensation is no longer valid.  
 
WEPC069 Impact of Nonlinear Resonances on Beam Dynamics at the SPring-8 Storage Ring injection, storage-ring, coupling, betatron 2181
 
  • M. Takao, J. Schimizu, Y. Shimosaki, K. Soutome
    JASRI/SPring-8, Hyogo-ken, Japan
  
  For a low emittance storage ring like high brilliant light sources, the improvement of nonlinear beam dynamics is necessary for the stable operation, or for providing large dynamic aperture and momentum acceptance for efficient injection and long Touschek lifetime. At the SPring-8 storage ring it is observed that injection efficiency is affected by the gap heights of the magnet arrays of the in-vacuum insertion devices. The fact that the injected beam of fundamentally oscillating in horizontal direction is limited by the vertical aperture means that coupling resonances influence the beam dynamics. To clarify the phenomena, we studied the nonlinear beam dynamics of transverse betatron motion by means of turn-by-turn method. Then, we found some nonlinear coupling resonances, such as the one by skew sextupole field, are excited to enhance vertical oscillation and to deteriorate the injection efficiency. By analyzing these results, we developed measures to suppress the effect of the nonlinear coupling resonances and to improve the injection efficiency.  
 
WEPC080 Non-linear Dynamics Optimization of the CLIC Damping Rings emittance, dynamic-aperture, lattice, quadrupole 2205
 
  • Y. Renier, F. Antoniou, H. Bartosik, Y. Papaphilippou
    CERN, Geneva, Switzerland
  • K.P. Wootton
    The University of Melbourne, Melbourne, Australia
  
  Non-linear dynamics studies are undertaken in order to optimize the dynamic aperture of the CLIC damping rings. In this respect, advanced methods such as frequency map and resonance driving term analysis are used in order to explore the working point space with respect to single particle stability. The impact of magnet errors and misalignments, and in particular, the effect of the super-conducting damping wigglers is evaluated. Additional considerations for the working point choice are presented.  
 
WEPC098 Automatic Pole and Q-Value Extraction for RF Structures scattering, cavity, RF-structure, cryomodule 2241
 
  • C. Potratz, H.-W. Glock, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • F. Marhauser
    JLAB, Newport News, Virginia, USA
  
  The experimental characterization of RF structures like accelerating cavities often demands for measuring resonant frequencies of Eigenmodes and corresponding (loaded) Q-values over a wide spectral range. A common procedure to determine the Q-values is the -3dB method, which works well for isolated poles, but may not be applicable directly in case of multiple poles residing in close proximity (e.g. for adjacent transverse modes differing by polarization). Although alternative methods may be used in such cases, this often comes at the expense of inherent systematic errors. We have developed an automation algorithm, which not only speeds up the measurement time significantly, but is also able to extract Eigenfrequencies and Q-values both for well isolated and overlapping poles. At the same time the measurement accuracy may be improved as a major benefit. To utilize this procedure merely complex scattering parameters have to be recorded for the spectral range of interest. In this paper we present the proposed algorithm applied to experimental data recorded for superconducting higher-order-mode damped multi-cell cavities as an application of high importance.  
 
WEPC108 CSR Impedance for an Ultrarelativistic Beam moving in a Curved Trajectory impedance, shielding, vacuum, radiation 2268
 
  • D.M. Zhou, K. Ohmi, K. Oide
    KEK, Ibaraki, Japan
  
  A dedicated computer code, CSRZ, has been developed to calculate the coherent synchrotron radiation (CSR) impedance for an ultrarelativistic beam moving in a curved trajectory. Following the pioneering work of T. Agoh and K. Yokoya*, the code solves the parabolic equation in the frequency domain in a curvilinear coordinate system. The beam is assumed to move along a vacuum chamber which has a uniform rectangular cross section but with variable bending radius. Using this code, we did investigations in calculating the longitudinal CSR impedance of a single and a series of bending magnets. The calculation results indicate that the shielding effect due to outer chamber wall can be well explained by a simple optical approximation model at high frequencies. The CSR fields reflected by the outer wall may interfere with each other in a long bending magnet and lead to sharp narrow peaks in the CSR impedance.
* T. Agoh and K. Yokoya, Phys. Rev. ST Accel. Beams, 7(5):054403 (2004). 		 
 
WEPS006 CNAO RF System: Hardware Description. cavity, proton, controls, impedance 2493
 
  • L. Falbo, G. Burato
    CNAO Foundation, Milan, Italy
  • M.M. Paoluzzi, G. Primadei
    CERN, Geneva, Switzerland
  
  CNAO is the Italian National Center of Oncological Hadrontherapy in Pavia. Proton beams are accelerated in the synchrotron and extracted in the energy range 60 to 250 MeV/u and carbon ion beams in the energy range 120 to 400 MeV/u. Trapping at the injection energy of 7 MeV/u and acceleration up to the extraction energy are done by an RF cavity which covers the needed wide range of frequency (0.4 to 3 MHz) and voltage (25 V to 5 kV) thanks to the use of a Vitrovac amorphous alloy. RF Gymnastics, including phase jumps to increase the momentum spread and empty bucket channelling, is requested and has been performed. A description of the hardware characteristics of the CNAO RF system and of its performance in terms of dynamic and static behaviour are reported in this paper.  
 
WEPS041 Tuning of the New 4-Rod RFQ for FNAL rfq, simulation, pick-up, linac 2580
 
  • J.S. Schmidt, B. Koubek, A. Schempp
    IAP, Frankfurt am Main, Germany
  
  For the injector upgrade at FNAL a 4-rod Radio Frequency Quadrupole (RFQ) with a resonance frequency of 200 MHz has been build. With this short structure of only 1.3 m a very compact injector design has been realized. Simulations with CST Microwave Studio® were performed for the design. Their results leading to the RF characterizations of the RFQ and the final RF setup which has been accomplished at IAP of the Goethe-University Frankfurt are presented in this paper.  
 
WEPS104 Transverse Beam Dynamics for the ISIS Synchrotron with Higher Energy Injection space-charge, simulation, injection, synchrotron 2754
 
  • B.G. Pine, C.M. Warsop
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  
  ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on an 800 MeV rapid cycling synchrotron, which provides 3·1013 protons per pulse at 50 Hz, corresponding to a beam power of 200 kW. Studies are underway to increase the energy of the ISIS linac from 70 to 180 MeV. This would reduce space charge in the synchrotron, and enable a larger current to be accumulated, possibly up to 0.5 MW. As part of the study, transverse beam dynamics have been re-examined on ISIS, building up models from incoherent space charge tune shift, through smooth focusing models with space charge to 2D alternating gradient lattice simulations. These later simulations, using the in-house space charge code Set, include harmonic perturbations to the focusing lattice, closed orbits and images. A clearer picture of the dynamics is emerging, where there may be important constraints on the highest intensities, including half integer resonance, image induced structure resonances and transverse instabilities.  
 
WEPZ009 Parametric-Resonance Ionization Cooling in Twin-Helix quadrupole, simulation, multipole, betatron 2784
 
  • V.S. Morozov, Y.S. Derbenev
    JLAB, Newport News, Virginia, USA
  • A. Afanasev, R.P. Johnson
    Muons, Inc, Batavia, USA
  • B. Erdelyi, J.A. Maloney
    Northern Illinois University, DeKalb, Illinois, USA
  
  Funding: Supported in part by DOE SBIR grant DE-SC0005589. Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Parametric-resonance Ionization Cooling (PIC) is proposed as the final 6D cooling stage of a high-luminosity muon collider. For the implementation of PIC, we developed an epicyclic twin-helix channel with correlated optics. Wedge-shaped absorbers immediately followed by short rf cavities are placed into the twin-helix channel. Parametric resonances are induced in both planes using helical quadrupole harmonics. We demonstrate resonant dynamics and cooling with stochastic effects off using GEANT4/ G4beamline. We illustrate compensation of spherical aberrations and benchmark COSY Infinity, a powerful tool for aberration analysis and compensation. 		 
 
THPPA01 EPS-AG Sacherer Prize: Beam Optics Developments for SPS, RHIC, LHC, CLIC and ATF2 sextupole, optics, dipole, extraction 2894
 
  • R. Tomás
    CERN, Geneva, Switzerland
  
  Highlights of linear and nonlinear optics studies are presented from various accelerators. At the LHC, optics correction is of critical importance to guarantee safe beam operation. Preparation for LHC optics measurements and corrections has been a major activity during the last decade. In particular, SPS and RHIC have served as excellent research and development machines to test new techniques and instrumentation, such as the measurement of resonance driving terms with and without AC dipoles. Together with a meticulous field quality specification, a careful installation strategy and an elaborate magnet model, these efforts have paid off in the LHC, where a record low beta-beating for hadron colliders below 10% has been achieved. Looking further into the future, the performance of the Final Focus System (FFS) is of critical importance for a future linear collider like CLIC, since it determines the IP beam spot sizes. The large chromatic aberrations required the development of novel non-linear optimization methods. Such techniques have successfully increased the CLIC design luminosity by 70% and an experimental test has been proposed for ATF2 to halve the design IP beam spot sizes.  
slides icon Slides THPPA01 [1.514 MB]  
 
THPC074 Dynamic Aperture and Tolerances for PEP-X Ultimate Storage Ring Design sextupole, dynamic-aperture, quadrupole, coupling 3065
 
  • M.-H. Wang, Y. Cai, R.O. Hettel, Y. Nosochkov
    SLAC, Menlo Park, California, USA
  • M. Borland
    ANL, Argonne, USA
  
  Funding: Work supported by the Department of Energy Contract DE-AC02-76SF00515.
A lattice for the PEP-X ultimate storage ring light source[1], having 11 pm-rad natural emittance at a beam energy of 4.5 GeV at zero current, using 90 m of damping wiggler and fitting into the existing 2.2-km PEP-II tunnel, has been recently designed[2]. Such a low emittance lattice requires very strong sextupoles for chromaticity correction, which in turn introduce strong non-linear field effects that limit the beam dynamic aperture. In order to maximize the dynamic aperture we choose the cell phases to cancel the third and fourth order geometric resonances in each 8-cell arc. Four families of chromatic sextupoles and six families of geometric (or harmonic) sextupoles are added to correct the chromatic and amplitude-dependent tunes. To find the best settings of the ten sextupole families, we use a Multi-Objective Genetic Optimizer employing elegant[3] to optimize the beam lifetime and dynamic aperture simultaneously. Then we evaluate dynamic aperture reduction caused by magnetic field multipole errors, magnet fabrication errors and misalignments. A sufficient dynamic aperture is obtained for injection, as well as workable beam lifetime[2]. 		 
 
THPC084 Optical Afterburner for a SASE FEL: First Results from FLASH electron, radiation, FEL, undulator 3089
 
  • M. Foerst
    CFEL, Hamburg, Germany
  • M. Gensch
    HZDR, Dresden, Germany
  • R. Riedel, E. Schneidmiller, N. Stojanovic, F. Tavella, M.V. Yurkov
    DESY, Hamburg, Germany
  
  Radiation Pulse from a Self-Amplified Spontaneous Emission Free Electron Laser (SASE FEL) consists out of spikes (wavepackets). Energy loss in the electron beam (averaged over radiation wavelength) also exhibits spiky behaviour on a typical scale of coherence length, and follows the radiation pulse envelope. These modulations of the electron beam energy are converted into large density (current) modulations on the same temporal scale with the help of a dispersion section, installed behind the x-ray undulator. Powerful optical radiation is then generated with the help of a dedicated radiator (afterburner). Envelope of the optical afterburner pulse is closely resembles the envelope of the x-ray pulse. We have recently demonstrated this principle at the Free Electron Laser in Hamburg (FLASH). We use THz undulator that is installed after the main X-ray as both dispersive element and radiator simultaneously. We characterize properties of the optical pulse using standard laser diagnostics techniques (i.e. FROG). Main result comes from the pulse duration measurement that we use to derive envelope of the x-ray radiation pulse duration which is in sub-100 fs range.  
 
THPO011 Practical Experience with Self-optimizing, High Dynamic Control of Accelerator Magnet Power Supplies controls, power-supply, proton, feedback 3355
 
  • H. Jäckle
    PSI, Villigen, Switzerland
  • F. Jenni, X.H. Ke
    FHNW, Windisch, Switzerland
  
  In 1999, the first fully digitally controlled magnet power supplies were commissioned at PSI (Paul Scherrer Institute, Switzerland). Today, approximately 1000 of them are in use at PSI and a multiple of that worldwide. An extended PI structure is used for control. PI control is very effective and simple to use but the attainable dynamic performance is usually limited by the higher order characteristics of the output filter and the load. For the future we expect increasing requirements from highly dynamic applications, such as beam orbit feedback systems and fast scanning magnets for proton irradiation of tumors. Therefore, a self-optimizing power supply control system was developed in collaboration with the University of Applied Sciences Northwestern Switzerland. It is based on the second generation of PSI digital power electronics controller, which allows more complex control algorithms and higher sampling rates. This paper presents the achieved dynamic performance of the new control structure for various types of power supplies and magnets and compares them with the dynamic performance obtained using standard PI control.  
 
THPO028 Upgrade Design of the Bump System in the J-PARC 3-GeV RCS power-supply, injection, linac, betatron 3403
 
  • T. Takayanagi, N. Hayashi, M. Kinsho, Y. Watanabe
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  
  The 3-GeV RCS aims at providing at least 300 kW output beam power with the injection beam at 181 MeV. In the second stage, the upgrade of the LINAC beam energy to 400 MeV was funded and started in March 2009. This plan will be completed in 2012. Consequently, the 3-GeV RCS will aim at 1 MW beam power. The injection bump system of the RCS is composed of the shift bump-magnets, the horizontal paint bump-magnets and the vertical paint magnets.  
 
THPS001 Experimental Studies of Beam Loss during Low Energy Operation with Electron Cooled Heavy Ions in the ESR ion, emittance, bunching, space-charge 3424
 
  • P.A. Görgen, O. Boine-Frankenheim
    TEMF, TU Darmstadt, Darmstadt, Germany
  • S. Appel, C. Dimopoulou, S.A. Litvinov, M. Steck
    GSI, Darmstadt, Germany
  
  At the ESR at GSI electron cooled heavy ion beams are decelerated to 4 MeV/u and extracted for the HITRAP experiment. We will report about cooling equilibrium measurements at 4 and 30 MeV/u for Ar18+ coasting beams. We compare the equilibrium beam parameters with results from beam dynamics simulations using the BETACOOL code and an analytic model of reduced complexity. The time slot in which HITRAP accepts beam is 2μs long. For optimum efficiency the beam has to be bunched to this length before extraction. The obtained bunch profiles are compared to longitudinal beam dynamics simulations. Our measurements show that at both energies bunching leads to severe beam loss. The estimated transverse space charge tune shifts during the rf bunching indicate that resonance crossing might be responsible for the observed the beam loss. The influence of the tune shift will be further evaluated through resonance measurements.  
 
THPS029 Simulations of Various Driving Mechisms for the 3rd Order Resonant Extraction from the MedAustron Medical Synchrotron extraction, betatron, lattice, synchrotron 3481
 
  • G. Feldbauer, M. Benedikt
    CERN, Geneva, Switzerland
  • U. Dorda
    EBG MedAustron, Wr. Neustadt, Austria
  
  The MedAustron medical synchrotron is based on the CERN-PIMMS design and its technical implementation by CNAO [1]. This document elaborates on studies performed on the baseline betatron-core driven extraction method and investigates the feasibility of alternative resonance driving mechanisms like RF-knockout, RF-noise and the lattice tune. Single particle tracking results are presented, explained and compared to analytical results.
[1] M. Pullia, ‘‘Status Report on the Centro Nazionale di Adroterapia Oncologica (CNAO)'', 11th EPAC'08, Genoa, Itlay, June 2008, p. 982 		 
 
THPS039 Diffusion of a Circulating Beam by the RF-Knockout with a Spectrum including Many Bands synchrotron, extraction, simulation, controls 3508
 
  • M. Tashiro, T. Nakanishi
    Nihon University, Narashino, Chiba, Japan
  
  The fast control of beam spill extracted from a synchrotron is a key function for the spot scanning irradiation in cancer therapy application. The authors have proposed the extraction method for the application which uses the control of a quadruple field of fast response as well as the RFKO (QAR method). The RF signal for the RFKO should cover a frequency band corresponding to a tune spread. A simulation with continuous RFKO operation, however, showed a spill intensity changes with time largely with only this band. The large change of spill is due to not uniform diffusion of circulating beam and it makes a constant spill difficult in the QAR method. A wider band gives a uniform spill, but it requires a larger Amp power. We proposed a spectrum including many bands around the resonances to reduce the power, since the bands outside around the resonances do not contribute to the diffusion. Such a spectrum has also an advantage to increase spill intensity for the QAR method, using a band so that the RFKO diffuses more inside particles of the separatrix but also it affects little them near the boundary. We can extract several times particles with a same shrink ratio of the separatrix.  
 
THPS058 Third Integer Resonance Slow Extraction Using RFKO at High Space Charge. extraction, dipole, betatron, space-charge 3559
 
  • V.P. Nagaslaev, J.F. Amundson, J.A. Johnstone, C.S. Park, S.J. Werkema
    Fermilab, Batavia, USA
  
  A proposal to search for direct mu->e conversion at Fermilab requires slow, resonant extraction of an intense proton beam. Large space charge forces will present challenges, partly due to the substantial betatron tune spread. The main challenges will be maintaining a uniform spill shape and moderate losses at the septum. We propose to use "radio frequency knockout" (RFKO) for fine tuning the extraction. Strategies for the RFKO method will be discussed here in the context of the mu->e experiment. Feasibility of this method has been demonstrated using simulations.  
 
THPS094 New Approaches in High Power RFQ Technology rfq, vacuum, linac, RF-structure 3654
 
  • A. Bechtold, J.M. Maus, G. Ritter
    NTG Neue Technologien GmbH & Co KG, Gelnhausen, Germany
  
  There is a clear tendency for the utilization of continuous wave c.w. high power RFQs in a huge variety of applications like nuclear waste transmutation or material research. They can serve as injectors for the production of secondary particles like neutrons or rare isotopes and can be applied for post acceleration of the latter ones. These RF-structures have to withstand an enormous amount of RF-power dissipated on the surfaces (up to several 10s kW per meter) and the associated thermal load. NTG Company gained lots of experience especially in the field of 4-rod c.w. RFQ design. Most recent developments to handle such high RF-power dissipation shall be reported.  
 
THPZ008 Strong-strong Simulations for Super B Factories II simulation, luminosity, factory, positron 3696
 
  • K. Ohmi
    KEK, Ibaraki, Japan
  
  Trials for the strong-strong simulation for study of beam-beam effect in large Piwinski angle (LPA) collision adopted in Super B factories. So far a combination method of particle in cell method and soft-Gaussian model has been used. We now show complete strong-strong simulation for LPA collision scheme. Collisions between many slices of two bunches are evaluated by particle in cell method with shifted Green function.  
 
THPZ011 Optimization of Chromatic Sextupoles in Electron Storage Rings Using Genetic Algorithms sextupole, dynamic-aperture, storage-ring, emittance 3705
 
  • Z. Duan
    IHEP Beijng, Beijing, People's Republic of China
  • Q. Qin
    IHEP Beijing, Beijing, People's Republic of China
  
  Funding: Work supported by National Science Foundation of China contract 10725525.
In order to suppress the head-tail instability, strong chromatic sextupoles are used in modern electron storage rings to correct large chromaticities due to small emittance or strong insertion quadrupoles to squeeze the bunch size at some places. However, the introduction of strong chromatic sextupoles also brings severe nonlinearity and might reduce dynamic aperture drastically. In the case of several sextupole families, the genetic algorithms are applied to find suitable configurations of sextupole strengths, directly maximizing dynamic aperture. A GeneRepair operator is introduced into the algorithm to correct chromaticities and optimize the dynamic aperture simultaneously in electron storage rings.