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coupling

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TUPLT184 Operational Measurement of Coupling by Skew Quadrupole Modulation focusing, electron, bunching, beamloading 1559
 
  • Y. Luo, P. Cameron, R. Lee, A. Marusic, F.C. Pilat, T. Roser, D. Trbojevic, J. Wei
    BNL, Upton, Long Island, New York
  The measurements of betatron coupling via skew quadrupole modulation is a new diagnostics technique that has been recently developed and tested at RHIC. By modulating the current of different skew quadrupole families with different frequencies and measuring the resulting eigentunes response with a high resolution phase lock loop (PLL) system, it is possible to determine the projections of the residual coupling coefficients. We report the results of extensive beam studies carried on at RHIC injection, store energy and on the ramp. The capability of measuring coupling on the ramp opens the possibility of continuous coupling corrections during acceleration.  
 
WEPLT060 Linear Coupling Theory of High Intensity Beams focusing, antiproton, bunching, impedance 1978
 
  • G. Franchetti, I. Hofmann
    GSI, Darmstadt
  • M. Aslaninejad
    IPM, Tehran
  It is planned to use linear coupling in the SIS18 in order to fully or partially equilibrate the transverse emittances before transfer to the projected SIS100 synchrotron. In this paper we show that space charge significantly modifies the coupling mechanism. In particular the width of the stop-band is dominated by the space charge tune shift for weak skew strength. The conditions are discussed, under which slow crossing of the coupling resonance leads to the desired goal of equalizing emittances while maintaining a sufficient matching of the beam to the ring and extraction optics.  
 
WEPLT061 Influence of Beam Tube Obstacles on the Emittance of the PITZ Photoinjector focusing, antiproton, bunching, impedance 1981
 
  • S. Setzer, W. Ackermann, S. Schnepp, T. Weiland
    TEMF, Darmstadt
  For detailed analysis of space charge dominated beams inside an RF Photoinjector PIC-Codes like MAFIA TS2/3 can be used. While the interaction of particles with the sourrounding geometries are taken into account, the applicability of such codes is restricted due to simulation time and memory consumption as well as by numercial noise. Therefore only smaller sections of the whole injector can be calculated. On the other hand codes like ASTRA can be used to simulate the whole injector but no interaction between bunch and geometry is included. To make use of the individual advantages of each code discribed above an interface for bidirectional bunch exchange between the two programs has been implemented. This approach allows for applying the right simulation method depending on the physical effects under investigation. To demonstrate the importance of such an approach the results of detailed numerical studies of the impact of beam tube obstacles like the laser mirror on the achievable emittance of the PITZ RF Photoinjector further downstream will be presented.  
 
WEPLT062 Wakefield Calculations for TTF-II focusing, antiproton, bunching, impedance 1984
 
  • I. Zagorodnov, T. Weiland
    TEMF, Darmstadt
  • M. Dohlus
    DESY, Hamburg
  In this paper we estimate long- and short-range wake functions for new elements to be used in TESLA Test Facility (TTF) - II. The wake potentials of the LOLA-IV structure and the 3rd harmonic section are calculated numerically for very short bunches and analytical approximations for wake functions in short and long ranges are obtained by fitting procedures based on analytical estimations. The numerical results are obtained with code ECHO for high relativistic Gaussian bunches with RMS deviation up to 0.015 mm. The calculations are carried out for the complete structures (including bellows, rounding of the irises and the different end cell geometries) supplied with ingoing and outgoing pipes. The low frequency spectra of the wake potentials is calculated using the Prony-Pisarenko method.  
 
WEPLT063 Investigation of Cavity Induced Longitudinal Coupled Bunch Mode Instability Behaviour and Mechanisms focusing, antiproton, bunching, electron 1987
 
  • R.G. Heine, P. Hartmann, H. Huck, G. Schmidt, T. Weis
    DELTA, Dortmund
  The narrowband impedances of RF-resonators in a circular accelerator can drive coupled bunch mode - CBI - instabilities which might spoil the overall beam quality. Often, as in synchrotron radiation light sources e.g. the instability does not lead to beam loss but to a severe degradation of the source brilliance. Investigations of longitudinal CBIs have been performed at the DELTA storage ring with a single DORIS-type cavity for future comparision with the behaviour of a HOM-damped cavity to be tested at DELTA. This resonator is presently developed and built within an EU-collaboration. The beam was deliberately driven into instability using the beam current as well as the cavity temperature as individual parameters. The instability characterisations at low (542 MeV) and high (1,5 GeV) energy exhibit a complex behaviour. The strength of the instability measured by the bunch excursions in the case of longitudinal CBIs, but also the spreading of the instability across neighbouring modes depends on parameters such as beam energy, resonant impedance but also on counteracting mechanisms like synchrotron radiation and Landau damping. The paper will cover the experimental results together with estimations of the influence and mechanism of Landau damping.  
 
WEPLT064 2-nd Order Sextupole Effects on the Dynamic Aperture in HERA-e focusing, antiproton, bunching, electron 1990
 
  • M. Vogt
    DESY, Hamburg
  During the first year after the luminosity upgrade HERA-e was operated in a mode for which the accessible area in transverse tune space was determined by resonances driven by sextupoles in 2-nd order. It turned out that with typical total incoherent beam beam tune shifts (.05,.08) for 2 IPs this space was too small for stable operation. We have used 2-nd order canonical perturbation theory to analyze the impact of the increased sextupole strengths in the upgraded lattice on the relevant resonance strengths and the detuning. Moreover, we have studied whether it is possible to compensate the resonances with localized octupole schemes (6 or 9 independent magnets) to 1-st and 2-nd order, computed the resulting detuning and compared the results with 6D tracking.  
 
WEPLT065 Hybrid Dry Coolers in Cooling Systems of High Energy Physics Accelerators focusing, antiproton, bunching, electron 1993
 
  • J.-P. Jensen, B. Conrad, U. Schuetz, F.-R. Ullrich, A. Wanning
    DESY, Hamburg
  Wet water cooling towers in high energy physics accelerators are state of the art. The advantages are robustness, effectiveness and cost-effectiveness. The return water temperature is lower than the air temperature due to cooling via evaporation. The disadvantages are the high water consumption, which becomes more costly in the future, and the soiling of the heat exchangers. If the water source is taken from wells then the drawdown of the ground water level has to be taken into account. DESY plans to use hybrid dry coolers for the two future projects: The XFEL linac and the PETRA 3 synchrotron light source. A hybrid dry cooler is a combination of a dry air cooler during cold and moderate seasons and additional wet cooling during the hot summer season. The cooling surface is wetted by adding water to increase the cooling capability by a factor of 250 %. The hybrid dry cooler saves a lot of water. The water consumption can be reduced by 70% compared to a wet cooling system. This contribution presents the auxiliary water consumption, the requirement of this water and an estimate of the temperature control behaviour of the hybrid dry cooling system.  
 
WEPLT066 Beam Dynamics Study for PETRA III Including Damping Wigglers focusing, antiproton, damping, bunching 1996
 
  • Y.L. Li, K. Balewski, W. Decking
    DESY, Hamburg
  Damping wigglers will be installed in the storage ring PETRA III to control the beam emittance to 1 nmrad. These wigglers will produce linear and nonlinear perturbations on beam dynamics. A new expanded transport matrix method is developed to solve linear dynamics, and used to match linear lattice functions. The symplectic method is adopted to track particle through the whole ring including the damping wigglers. Halbach?s formulae are used to describe the wiggler field. The main parameters of the wigglers are derived from field calculations. In order to avoid dangerous resonances, tune scanning is implemented to find suitable working points. According to presently known field quality, the nonlinear effects of damping wigglers will not degrade the performance of PETRA III and the dynamic aperture is still larger than the physical aperture.  
 
WEPLT067 Space Charge Problem in Low Energy Super-conducting Accelerator antiproton, damping, bunching, electron 1999
 
  • N.E. Vasyukhin, R. Maier, Y. Senichev
    FZJ/IKP, Jülich
  At present the super-conducting option of linear accelerators is considered for low energy, and new type of RF cavities is considered for this purpose. However, together with electrodynamics problems we should solve the transverse stability problem, since in structures with external focusing elements the focusing period is longer, and in higher accelerating field the defocusing factor increases as well. In this paper we consider the transverse stability problem, taking into account the non-linear space charge problem. The fundamental mechanism of hallo creation in super-conducting linear accelerators is investigated to minimize the particle losses. The theoretical results are supported by numerical simulation.  
 
WEPLT068 Momentum Compaction Factor and Nonlinear Dispersion at the ANKA Storage Ring antiproton, damping, bunching, booster 2002
 
  • A.-S. Müller, A. Ben Kalefa, I. Birkel, E. Huttel, M. Pont, F. Pérez
    FZK-ISS-ANKA, Karlsruhe
  The ANKA electron storage ring operates in the energy range from 0.5 to 2.5 GeV. In order to improve machine performance a precise modelling of linear and nonlinear optics is mandatory. Apart from higher order chromaticity also momentum compaction factor and dispersion have to be controlled. In this framework, the higher order momentum compaction factor has been determined exploiting the extraordinary precision of the resonant spin depolarisation method. Furthermore the nonlinear horizontal dispersion was measured as a function of the momentum deviation for different chromaticities. This paper discusses the experimental results and compares the findings to different simulations.  
 
WEPLT069 Investigation of Scraper Induced Wake Fields at ANKA antiproton, damping, bunching, booster 2005
 
  • A.-S. Müller, I. Birkel, E. Huttel, M. Pont, F. Pérez
    FZK-ISS-ANKA, Karlsruhe
  • F. Zimmermann
    CERN, Geneva
  The ANKA synchrotron light source operates in the energy range from 0.5 to 2.5 GeV. Typical requirements for light sources include small beam sizes, large lifetimes and high currents to provide the highest possible photon flux. The understanding of impedance and instability related issues is very important in order to improve the machine performance, in particular when small aperture insertion devices are installed that require protection by a scraper. In the framework of an impedance survey the transverse and longitudinal wake fields induced by a vertical scraper have been measured and analysed. This paper reports the beam observations and compares them with the expectation.  
 
WEPLT070 Studies of Current Dependent Effects at ANKA antiproton, damping, bunching, booster 2008
 
  • A.-S. Müller, I. Birkel, E. Huttel, M. Pont, F. Pérez
    FZK-ISS-ANKA, Karlsruhe
  • F. Zimmermann
    CERN, Geneva
  The ANKA electron storage ring is operated at energies between 0.5 and 2.5 GeV. A major requirement for a synchrotron light source, such as ANKA, is to achieve a high beam current. A multitude of mostly impedance related effects depend on either bunch or total beam current. This paper gives an overview over the various beam studies performed at ANKA in this context, specifically the observation of current dependent detuning, the dermination of the bunch length change with current from a measurement of the ratio between coherent and incoherent synchrotron tune and an assessment of the effective longitudinal loss factor from the current dependent horizontal closed orbit distortion.  
 
WEPLT071 Longitudinal Resonances and Emittance Growth Using QWR/HWR in a Linac antiproton, damping, booster, focusing 2011
 
  • P. Bertrand
    GANIL, Caen
  In the frame of the SPIRAL II project at GANIL, we present an analytical approach allowing us to understand in a simple way the longitudinal behaviour of a beam , transmitted in bunching mode or accelerated in a Linac designed with QWR or HWR cavities. In particular, we make appear the strong relationship with the Henon map properties.  
 
WEPLT072 Preliminary Design of the RF Systems for the SPIRAL 2 SC Linac antiproton, damping, booster, focusing 2014
 
  • M. Di Giacomo, B. Ducoudret, J.F. Leyge
    GANIL, Caen
  • J.F. Denis, M. Desmons, M. Luong, A. Mosnier
    CEA/DSM/DAPNIA, Gif-sur-Yvette
  In the SPIRAL 2 Linac, a 5 mA, CW , Deuteron beam is accelerated up to 40 MeV, through a normal conducting RFQ and 26 independent-phase SC quarter wave resonators, working at 88,05 MHz. Tube and solid state amplifiers derived from the standard FM transmitter modules are used while a new digital control system has been designed for the feed-back and feed-forward control system. The paper presents the power and low level systems for both the normal and superconducting cavities and results of simulations of the RF system in operating conditions.  
 
WEPLT073 VDHL Design and Simulation of a Fast Beam Loss Interlock for TTF2 antiproton, damping, booster, focusing 2017
 
  • A. Hamdi
    CEA/Saclay, Gif-sur-Yvette
  • M. Luong
    CEA/DSM/DAPNIA, Gif-sur-Yvette
  • M. Werner
    DESY, Hamburg
  The TTF2 fast beam loss interlock provides different modes of protection. Based on the differential beam charge monitoring over a macropulse, a pulse slice or bunch-by-bunch, the signal processing time should be as short as the bunch repetition period (110 ns). The signal delivered by the toroid-like inductive current transformer always shows an envelope droop due to its self-inductance to resistance ratio. When the macropulse length is comparable to this ratio, the charge of each bunch must be derived from the difference of the top to the bottom level on the signal. This necessity combined to the various protection modes leads to a digital implementation. All the processing functionalities are designed with VHDL for a Xilinx FPGA. Because the interlock involves other control signals in addition to the toroid signal with specific shapes, which cannot be easily reproduced for the design validation before the TTF2 completion, VHDL provides meanwhile the possibility for an exhaustive validation of the system with a software test bench including all timing information.  
 
WEPLT075 Status Report on the Beam Dynamics Developments for the SPIRAL 2 Project antiproton, damping, booster, focusing 2020
 
  • R. Duperrier, D. Uriot
    CEA/DSM/DAPNIA, Gif-sur-Yvette
  • P. Bertrand, F. Varenne
    GANIL, Caen
  • J.-L. Biarrotte
    IPN, Orsay
  • J.-M. De Conto
    ISN, Grenoble
  • E. Froidefond
    LPSC, Grenoble
  • N. Pichoff
    CEA/DAM, Bruyères-le-Châtel
  The driver for the SPIRAL 2 project aims to accelerate a 5 mA D+ beam up to 20 A.MeV and a 1 mA beam for Q/A=1/3 up to 14.5 A.MeV. It operates in a continuous wave regime (cw), is designed for a maximum efficiency in the transmission of intense beams. Recent studies have led to change the reference design. The current design consists in an injector (ECR sources + LEBTs with the possibility to inject from several sources + a Radio Frequency Quadrupole) followed by a superconducting section based on an array of independently phased cavities where the transverse focalisation is performed by warm quadrupoles. This paper presents the beam dynamics studies associated to these new choices, the HEBT design and the fast chopping in the MEBT.  
 
WEPLT076 SPIRAL 2 RFQ Design antiproton, damping, booster, focusing 2023
 
  • R. Ferdinand, G. Congretel, A. Curtoni, O.D. Delferriere, A. France, D.L. Leboeuf, J. Thinel, J.-C. Toussaint
    CEA/DSM/DAPNIA, Gif-sur-Yvette
  • M. Di Giacomo
    GANIL, Caen
  The SPIRAL2 RFQ is designed to accelerate at 88MHz two kinds of charge-over-mass ratio, Q/A, particles. The proposed injector can accelerate a 5 mA deuteron beam (Q/A=1/2) or a 1 mA particles beam with q/A=1/3 up to 0.75 MeV/A. It is a CW machine which has to show stable operation, provide the request availability, have the minimum losses in order to minimize the activation constraints and show the best quality/cost ratio. It will be a 4-vane RFQ type, with a mechanical assembly, the global assumption being to build an RFQ without any brazing step. Extensive modelisation was made to ensure a good vane position under RF. A 1-m long hot model prototype is under construction in order to validate the manufacturing concept.  
 
THPKF016 The Metrology Light Source of the Physikalisch-Technische Bundesanstalt in Berlin-Adlershof wakefield, beamloading, lattice, beamlosses 2290
 
  • R. Klein, G. Ulm
    PTB, Berlin
  • M. Abo-Bakr, P. Budz, K. Bürkmann, D. Krämer, J. Rahn, G. Wustefeld
    BESSY GmbH, Berlin
  PTB, the German National Metrology Institute, has gained approval for the construction of a low-energy electron storage ring in the close vicinity of BESSY II, where PTB operates a laboratory for X-ray radiometry. The new storage ring, named 'Metrology Light Source MLS' will be dedicated to metrology and technology development in the UV and EUV spectral range and so will fill the gap that is present since the shut down of BESSY I. The MLS is designed in close cooperation with BESSY and is located adjacent to the BESSY II facility. Construction will start 2004 and user operation is scheduled to begin in 2008. The MLS has a circumference of 48 m, injection will be from a 100 MeV microtron. The electrons energy is ramped to an eligible value in the range from 200 MeV to 600 MeV. The MLS will be equipped with all the instrumentation necessary to measure the storage ring parameters needed for the calculation of the spectral photon flux according to the Schwinger theory with low uncertainty, enabling PTB to operate the MLS as a primary source standard. Moreover, provision is taken to operated the MLS in a low alpha mode for the production of coherent synchrotron radiation in the far IR and THz region.  
 
THPKF017 Status of the Synchrotron Light Source DELTA wakefield, beamloading, lattice, beamlosses 2293
 
  • D. Schirmer, U. Berges, J. Friedl, A. Gasper, M. Grewe, P. Hartmann, R.G. Heine, H. Huck, G. Schmidt, C. Sternemann, M. Tolan, T. Weis, C. Westphal, K. Wille
    DELTA, Dortmund
  Since 1999, the Dortmunder 1.5 GeV electron storage ring DELTA was continuously extended. The facility serves universities and industries as a source of synchrotron radiation on a regional level. The consolidation of the machine was finally completed in 2002. By now, DELTA, operated for 3000 hours per year, has reached a reliability comparable to other facilities in the world. Large improvements have been made in the installation of the beamlines. At present, two undulator beamlines and several dipole beamlines in the range of soft X-rays are in operation. The 5.3 T superconducting asymmetric wiggler (SAW) serves three beamlines in the hard X-ray regime with circular polarized light. Also the accelerator physics research program has been promoted. The vacuum system was revised during the last year to provide extra space for test sections and additional diagnostics. Substantial progress was achieved by SVD based orbit correction and LOCO based optics modelling as well as detailed CBM studies and a new method for fast tune measurements has been implemented. Future developments for machine improvements, such as DSP-based fast local orbit feedback and a frequent injection mode are in preparation.  
 
THPKF071 Linear Coupling and Lifetime Issues in the DIAMOND Storage Ring target, vacuum, gun, simulation 2427
 
  • R. Bartolini
    Diamond, Oxfordshire
  • N.G. Wyles
    CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
  In synchrotron light sources the correction of the linear coupling is an important issue related to the brightness of the photon beam and to the beam lifetime. The vertical emittance of the electron beam in the DIAMOND storage ring will be controlled using 168 skew quadrupoles embedded in the sextupoles of the ring. In this paper we report the linear coupling estimates for the expected misalignment errors and we compare the results of coupling correction with different correction strategies. The effect on lifetimes is also discussed.  
 
THPKF072 Progress with the Diamond Light Source gun, simulation, insertion, target 2430
 
  • R.P. Walker
    Diamond, Oxfordshire
  Construction of Diamond, the UK?s new 3 GeV, 3rd generation synchrotron light source, is well underway and progressing in-line with the original target of starting storage ring commissioning in January 2006 and being operational for users in January 2007. Having completed the foundations, the main building works are now proceeding at their maximum rate. Most of the major machine components are also under construction, aiming towards the key target date of starting machine installation in September 2004. As well as reporting on the overall status, detailed design developments and component choices will be summarised. The results of tests of various prototype components, including magnets, vacuum vessels and girders, will also be presented.  
 
THPKF073 CIRCE, the Coherent InfraRed CEnter at the ALS gun, simulation, insertion, target 2433
 
  • J.M. Byrd, S. De Santis, J.-Y. Jung, M.C. Martin, W.R. McKinney, D.V. Munson, H. Nishimura, D. Robin, F. Sannibale, R.D. Schlueter, M. Venturini, W. Wan, M.S. Zolotorev
    LBNL, Berkeley, California
  CIRCE (Coherent InfraRed Center) is a new electron storage ring to be built at the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory (LBNL). The ring design is optimized for the generation of coherent synchrotron radiation (CSR) in the terahertz frequency range. CIRCE operation includes three possible modes: ultra stable CSR, femtosecond laser slicing CSR and broadband SASE. CSR will allow CIRCE to produce an extremely high flux in the terahertz frequency region. The many orders of magnitude increase in the intensity is the basis of our project and enables new kinds of science. The characteristics of CIRCE and of the different modes of operation are described in this paper.  
 
THPKF075 LUX - A Recirculating Linac-based Facility for Ultrafast X-ray Science radiation, electron, linac, simulation 2436
 
  • J.N. Corlett, W.A. Barletta, S. De Santis, L.R. Doolittle, W. Fawley, P.A. Heimann, S.R. Leone, D. Li, S.M. Lidia, G. Penn, A. Ratti, M. Reinsch, R.W. Schoenlein, J.W.  Staples, G.D. Stover, S.P. Virostek, W. Wan, R. Wells, R.B. Wilcox, A. Wolski, J.S. Wurtele, A. Zholents
    LBNL, Berkeley, California
  We present design concepts for LUX - a proposed source of ultra-fast synchrotron radiation pulses based on a recirculating superconducting linac. The source produces high-flux VUV-x-ray pulses with duration of 100 fs or less at a 10 kHz repetition rate, optimized for the study of ultra-fast dynamics across many fields of science. Cascaded harmonic generation in free-electron lasers (FEL's) produces coherent radiation in the VUV-soft x-ray regime, and a specialized technique is used to compress spontaneous emission for ultra-short-pulse photon production in the 1 - 10 keV range. High-brightness electron bunches of 2-3 mm-mrad emittance at 1 nC charge in 30 ps duration are produced in an rf photocathode gun and compressed to 3 ps duration following an injector linac, and recirculated three times through a 1 GeV main linac. In each return path, harmonic cascades are inserted to produce seeded FEL radiation in selected photon energy ranges from approximately 20 eV with a single stage of harmonic generation, to 1 keV with a four-stage cascade. The lattice is designed to minimize emittance growth from effects such as coherent synchrotron radiation (CSR), and to propagate electron beams carrying nm-scale density modulation in the final stages of cascaded harmonic generation. Synchronization of tens of femtoseconds is achieved by use of an optical master oscillator distributing timing signals over actively stabilized fiber, and generation of rf signals from the optical master oscillator. We describe technical developments in key areas including injection from a high repetition rate rf photocathode gun, lattice design, UV and soft x-ray production by high-gain harmonic generation, a kicker design for rapid transfer of the electron beam between radiator beamlines, lasers systems concepts, and synchronization between experimental pump lasers and the x-ray pulse.