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MOXPA02 SCRF Test Facilities toward the ILC TTF, KEK, XFEL, linac 5
 
  • K. Saito
    KEK, Ibaraki
  After the ICFA selection of the superconducting linear collider technology in August 2004, many intensive R&D programs are in the planning stage or already underway. Work is proceeding in the three major geographical regions involved in the ILC: Europe(TTF), North America (SMTF) and Asia (STF). In this paper, the global activity represented by these superconducting RF test facilities will be reviewed. Their goals, plans, schedules and possible complementarities will be presented. The performance expected from the different R&D efforts by 2008, and the corresponding contribution to the ILC Technical Design Report, will be especially emphasized.  
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MOPCH010 High Power Tests of a High Duty Cycle, High Repetition Rate RF Photoinjector Gun for the BESSY FEL gun, PITZ, FEL, klystron 68
 
  • F. Marhauser
    BESSY GmbH, Berlin
  The proposed BESSY Soft X-ray FEL uses a normal conducting 1.3 GHz photoinjector RF gun cavity at comissioning phase. Due to the challenging RF pulse pattern the cavity has to cope with an average power of 75 kW. A 1.5-cell RF gun prototype has been built with a dedicated cooling layout. Results of the first high power RF tests are detailed in this paper.  
 
MOPCH012 FEL Disturbance by Ambient Magnetic Field Changes PETRA, proton, linac, electron 74
 
  • H. Kapitza, P. Göttlicher, N. Heidbrook, H. Schlarb
    DESY, Hamburg
  The VUV-FEL at DESY in Hamburg (Germany) is mostly located inside the circular accelerator PETRA which serves as an injector for the electron proton collider HERA. SASE was regularly lost in the VUV-FEL when protons were ramped to the injection energy in PETRA. This effect was mediated by magnetic field changes in the order of 1 microtesla, caused by time-dependent uncompensated magnet currents of more than 800 A which made PETRA act like a large current loop. The resulting beam displacements of several hundred micrometers in the undulators proved to be enough to make SASE fail. This serious disturbance of user runs was eliminated by introducing an improved compensation scheme which further limits residual currents in PETRA during proton injection. The consequences of this observation for the design of the XFEL are briefly discussed.  
 
MOPCH013 Slice Emittance Measurements at FLASH emittance, quadrupole, RF-structure, CSR 77
 
  • M. Roehrs, C. Gerth, M. Huening, H. Schlarb
    DESY, Hamburg
  The SASE process in Free Electron Lasers mainly depends on time-sliced parameters of charge density, energy spread and transverse emittance. At the VUV-FEL at DESY, electron bunches are compressed longitudinally in two magnetic chicanes in order to achieve high peak currents. The compression causes considerabe variations in slice emittance along the bunches. The vertically deflecting rf-structure LOLA, which is in operation at the VUV-FEL since early 2005, allows to resolve longitudinal variations in horizontal slice width for single bunches. The horizontal slice emittances can be determined by additionally varying the strengths of the quadrupoles upstream of LOLA. Results of slice emittance measurements using different bunch compression schemes are presented.  
 
MOPCH014 Energy-time Correlation Measurements Using a Vertically Deflecting RF Structure acceleration, CSR, emittance, FEL 80
 
  • M. Roehrs, C. Gerth, M. Huening, H. Schlarb
    DESY, Hamburg
  To initiate the lasing process in SASE-based Free Electron Lasers, electron bunches with high peak currents are necessary. At the VUV-FEL at DESY, high peak currents are produced by bunch shortening in magnetic chicanes induced by a linear energy-time gradient. The residual uncorrelated time-sliced energy width after compression is a crucial parameter for the lasing process. The final energy-time correlation provides important information about the compression process. This paper presents a measurement of slice energy spread and energy-time correlation using a vertically deflecting rf-structure (LOLA). The structure allows to map the time delay of bunch slices to the vertical axis of a screen. After dispersing the bunches horizontally with a dipole, the energy-time correlation can be directly obtained in a single shot measurement. Results for different bunch compression schemes are presented. The measured bunch length in case of a non-compressed beam is compared to streak camera measurements.  
 
MOPCH147 Developments in Conditioning Procedures for the TTF-III Power Couplers vacuum, electron, controls, monitoring 399
 
  • H. Jenhani, T. Garvey, P. Lepercq, M. Omeich, C.P. Prevost, V. Variola
    LAL, Orsay
  Despite extensive experience in many laboratories on power conditioning of couplers for RF superconducting accelerators, it is still not a well understood procedure and can produce many unpredictable phenomena. There remains considerable interest in reducing the power coupler conditioning time necessary for superconducting linear accelerators. This paper presents studies of optimisation of the conditioning procedure for the couplers intended for use on the European XFEL project.  
 
MOPCH151 Pulsed RF System for the ELBE Superconducting Accelerator ELBE, controls, klystron, vacuum 411
 
  • A. Buechner, F.G. Gabriel
    FZR/FWFE, Dresden
  • H. Buettig, U. Lehnert, P. Michel, Ch. Schneider, R. Schurig
    FZR, Dresden
  The RF system for the ELBE accelerator was originally designed for CW mode. Although this works problem-free tests have shown that it is possible to reach higher gradients in the TESLA cavities with a pulsed RF system. The new RF system will be presented together with measurements of the achievable gradients. Roughly 30% higher gradients could now be used in pulsed mode. As positive side effects the radiation by field emission is reduced by the duty cycle and an easy in situ RF conditioning of cavities and coupler windows is possible.  
 
MOPCH154 Dry-ice Cleaning on SRF Cavities superconductivity, controls, linac, vacuum 418
 
  • A. Brinkmann, J.I. Iversen, D. Reschke, J. Ziegler
    DESY, Hamburg
  High pressure rinsing with ultra-pure water is the well-proven standard cleaning step after chemical or electrochemical surface treatment of SRF cavities. Dry-ice cleaning (DIC) is a powerful additional cleaning option which depends on the sublimation-impulse method. Particles and film contaminations, especially hydro-carbons, are removed without residues. Furthermore DIC offers the possibility of a final horizontal cleaning of a fully equipped cavity because water is not present in the cleaning process. Horizontal cleaning tests on single-cell cavities showed promising high gradient, high Q-value performances, but field emission is still the limiting effect. On the basis of these tests a new IR-heater module is installed to keep a high temperature gradient between the CO2 jet and the cavity surface. New test results for this optimized cleaning set-up will be presented.  
 
MOPCH155 Performance Limitations of Tesla Cavities in the Flash Accelerator and their Relation to the Assembly Process vacuum, TESLA, pick-up, controls 421
 
  • L. Lilje
    DESY, Hamburg
  Several accelerator modules with superconducting cavities have been assembled for TTF. The paper reviews the performance of these structures and will try to correlate their performance to information about the assembly process. In some cases a performace degradation could be attributed to problems in this process. The introduction of additional quality control steps improved accelerator module performance. For example, the more recently assembled modules have shown the expected acceleration gradients and no vacuum leaks.  
 
MOPCH171 ILC Coaxial Blade Tuner TTF, LEFT, electron, linear-collider 466
 
  • C. Pagani, A. Bosotti, P. Michelato, N. Panzeri, R. Paparella, P. Pierini
    INFN/LASA, Segrate (MI)
  A coaxial (blade) tuner solution has been developed for the compensation of the Lorentz force detuning of the superconducting cavities under the high gradient pulsed operation foreseen for ILC operation. The device is based on prototypes successfully tested at DESY in 2002 both on CHECHIA and on the superstructures inserted in the TTF string. During both tests the blade tuner performed as expected in terms of stiffness, frequency sensitivity and tuning capabilities. An improvement of the tuner characteristics has been designed by the integration of fast tuning capabilities by means of piezo-ceramic element. Two prototipes of the new INFN coaxial piezo blade tuner have just been manufactured and they will be tested at DESY and BESSY after the cavity integration. In this paper the blade tuner design and main characteristics are presented, together with the early interpretation of the cold test results.  
 
MOPCH174 Optimization of the BCP Processing of Elliptical Nb SRF Cavities simulation, LEFT, extraction, insertion 469
 
  • C. Boffo, C. A. Cooper, A.M. Rowe
    Fermilab, Batavia, Illinois
  • G. Galasso
    University of Udine, Udine
  Bulk niobium (Nb) electropolished SRF cavities performing at or above 35 MV/m is an aggressive goal recently put forth by the International Linear Collider (ILC) collaboration. Buffered chemical polishing (BCP) is still the most cost effective and least complex processing technique known today to optimize the surface properties of high gradient single crystal and relatively low gradient polycrystalline SRF cavities. BCP will be the preferred chemical process in the production of the nine-cell third harmonic 3.9 GHz cavities at Fermilab. The internal shape of these cavities will result in uneven material removal rates between iris and equator of the cells. We will describe a thermal-fluid finite element model adopted to simulate the etching process, and thus revealing the issues at hand. Experimental work, such as flow visualization tests performed to verify the simulation, will also be discussed. Finally we are presenting results obtained with a novel device, which allows to homogenize the flow pattern and to resolve the problem.  
 
MOPCH179 Design of a New Electropolishing System for SRF Cavities KEK, TESLA, controls, LANL 484
 
  • T. Tajima
    LANL, Los Alamos, New Mexico
  • C. Boffo
    Fermilab, Batavia, Illinois
  • M.P. Kelly
    ANL, Argonne, Illinois
  • J. Mammosser
    Jefferson Lab, Newport News, Virginia
  Electropolishing (EP) is considered the baseline surface treatment for Superconducting RF (SRF) cavities to achieve >35 MV/m accelerating gradient for the International Linear Collider (ILC). Based on the lessons learned at the forerunners such as KEK/Nomura, DESY and JLAB and on the recent studies, we have started a new design of the next EP system that will be installed in the US. This paper presents requirements, specifications, and the detail of the system design as well as the path forward towards the future industrialization.  
 
MOPLS063 Accelerator Component Vibration Studies and Tools quadrupole, TESLA, resonance, vacuum 688
 
  • R. Amirikas, A. Bertolini, W. Bialowons
    DESY, Hamburg
  This talk will cover a research program on accelerator component vibrations. Ground motion and technical noise, such as vacuum and refrigeration systems, couple to the beam, mainly via quadrupoles, making the design of their supports, especially, in the case of the superconducting magnets, critical. This program includes investigation of cold mass vibration of the superconducting quadrupoles inside an accelerating module and sensor performance in the main or fringe field of a linear collider detector. Seismometer accuracy limitations in correlated ground motion measurements are also being investigated.  
 
MOPLS064 Measurement of Ground Motion in Various Sites site, ground-motion, LHC, synchrotron 691
 
  • W. Bialowons, R. Amirikas, A. Bertolini, D. Kruecker
    DESY, Hamburg
  This presentation will be an overview of a study program, initiated in DESY, to measure ground vibration of various sites which can be used for site characterization for the International Linear Collider (ILC) design. Commercial broadband seismometers have been used to measure ground motion, correlation and surface wave velocity. The database of measured ground vibrations is available to the scientific community. A parameterization of the spectra will also be presented.  
 
MOPLS084 Experimental Comparison at KEK of High Gradient Performance of Different Single Cell Superconducting Cavity Designs KEK, TESLA, controls, superconductivity 750
 
  • F. Furuta, Y. Higashi, T. Higo, I.H. Inoue, S. Kazakov, Y. Kobayashi, H. Matsumoto, Y. Morozumi, R.S. Orr, T. Saeki, K. Saito, K. Ueno, H. Yamaoka
    KEK, Ibaraki
  • J.S. Sekutowicz
    DESY, Hamburg
  We have performed a series of vertical tests of three different designs of single cell Niobium superconducting cavities at 2 degrees Kelvin. These tests aimed at establishing that an accelerating gradient of 45 MV/m could be reached in any of the designs, while using the standard KEK surface preparation. The designs tested were the Cornell re-entrant shape (RE), the DESY/KEK low loss shape (LL), and the KEK ICHIRO series. The cavities underwent surface preparation consisting of centrifugal barrel polishing, light chemical polishing, electropolishing, and finally a high pressure water rinse. All three kinds of cavities were used in a series of vertical tests to investigate details of the surface treatment. When using ultra-pure water for the high pressure rinse, the LL cavity reproducibly exceeded a gradient of 45 MV/m, the RE design reproducibly reached a gradient of between 50 MV/m and 52 MV/m, and three of the six ICHIRO cavities reached a gradient of between 45 MV/m and 49 MV/m.  
 
MOPLS104 The Progress in Developing Superconducting Third Harmonic Cavity simulation, coupling, XFEL, TTF 804
 
  • N. Solyak, H. Edwards, M. Foley, I.G. Gonin, E.R. Harms, T.K. Khabiboulline, D.V. Mitchell, D.O. Olis, A.M. Rowe
    Fermilab, Batavia, Illinois
  XFEL and TTF facilities are planning to use section with a few third harmonic cavities (3.9GHz) upstream of the bunch compressor to improve beam performances [1-2]. Fermilab is developing superconducting third harmonic section for TTFII upgrade. This section will include four cavities equiped with couplers and blade tuners, installed in cryostat. Up to now, two cavities are complete and one of them is under test. The status of the cavity development and preliminary test results are presented in the paper.  
 
MOPLS110 ILC Linac R&D at SLAC SLAC, klystron, linac, collider 822
 
  • C. Adolphsen
    SLAC, Menlo Park, California
  Since the ITRP recommendation in 2004 to use superconducting rf technology for a next generation linear collider, the former NLC group at SLAC has been actively pursuing a broad range of R&D for this collider (the ILC). In this paper, we review the progress of those programs relating to linac technology. These include the development of a Marx-style modulator (120 kV, 120 A, 1.5 ms, 5 Hz) and a 10 MW sheet-beam klystron, construction of an L-band (1.3 GHz) rf source using a SNS HVCM modulator and commercial klystrons, fabrication and testing of a five-cell L-band cavity prototype for the ILC positron capture accelerator, high power tests of cavity coupler components, beam tests of prototype S-band linac beam position monitors and measurements of the magnetic center stability of an ILC prototype superconducting quadrupole magnet built by the CIEMAT group in Spain.  
 
TUPCH007 High Resolution BPM for the Linear Colliders pick-up, dipole, simulation, collider 1004
 
  • C. Simon, S. Chel, M. Luong, O. Napoly, J. Novo, D. Roudier
    CEA, Gif-sur-Yvette
  • N. Rouvière
    IPN, Orsay
  The beam-based alignment and feedback systems which are essential for the operation of the future colliders use some high resolution Beam Position Monitors (BPM). In the framework of CARE/SRF, the task of CEA/DSM/DAPNIA (Saclay) is the design, the fabrication and the beam test of a BPM in collaboration with DESY. This system is composed of a RF re-entrant cavity with a beam pipe radius of 78mm and an analog electronics having several signal processing steps to reject the monopole mode. Thanks to its high position resolution (better than 1μm) and its high time-resolution (around 10ns), it is a candidate for the X-FEL at DESY and the ILC. Indeed the chosen coupling allows the bunch to bunch measurement and the separation between the monopole and dipole modes. Moreover, this BPM is designed to be used in a clean environment, at the cryogenic and room temperatures.  
 
TUPCH016 Numerical Simulation of Synchrotron Radiation for Bunch Diagnostics simulation, radiation, vacuum, synchrotron 1031
 
  • A. Paech, W. Ackermann, T. Weiland
    TEMF, Darmstadt
  • O. Grimm
    DESY, Hamburg
  For the operation of the VUV-FEL at DESY, Hamburg, the longitudinal charge distribution of the electron bunches that drive the free electron laser is of high importance. One novel method to measure the bunch shape is to analyze the coherent far-infrared synchrotron radiation generated at the last dipole magnet of the first bunch compressor. For the correct interpretation of the results it is mandatory to know how various parameters, like the bunch shape and path, the vacuum chamber walls, the optical beamline, etc., influence the observed spectrum. The aim of this work is to calculate the generation of synchrotron radiation inside the bunch compressor with the emphasis of including the effects of the vertical and horizontal vacuum chamber walls in the vicinity of the last dipole magnet. Challenging problems for the numerical simulations are the very short wavelength and the broad frequency range of interest. As a first step, it is shown how the radiation leaving the vacuum chamber, that is generated by a single point charge, can be calculated with the help of the uniform theory of diffraction (UTD).  
 
TUPCH021 Principles of longitudinal beam diagnostics with coherent radiation electron, radiation, diagnostics, laser 1040
 
  • O. Grimm
    DESY, Hamburg
  The Kramers-Kronig dispersion relation connects the real and imaginary part of a response function under very general assumptions. It is used in the context of accelerator physics for longitudinal bunch diagnostics as a phase retrieval technique: the modulus of the complex form factor (the Fourier transform of the charge distribution) is accessible experimentally, and the missing phase then (partially) reconstructed to allow an inversion of the Fourier transform. Contrary to real and imaginary part, the connection between modulus and phase is not unique anymore due to the possibility of zeros of the form factor in the complex frequency plane that cannot be measured. This paper gives a mathematically explicit, step-by-step derivation of the phase reconstruction technique for bunch diagnostics, and it explains the problem of zeros and their practical effect with some examples. The intention is not utmost mathematical rigour, but a clear, accessible explanation of all steps involved.  
 
TUPCH024 Comparative Study of Bunch Length and Arrival Time Measurements at FLASH laser, electron, SASE, FEL 1049
 
  • H. Schlarb, A. Azima, S. Düsterer, M. Huening, E.-A. Knabbe, M. Roehrs, R. Rybnikov, B. Schmidt, B. Steffen
    DESY, Hamburg
  • M.C. Ross
    SLAC, Menlo Park, California
  • P. Schmüser, A. Winter
    Uni HH, Hamburg
  Diagnostic devices to precisely measure the longitudinal electron beam profile and the bunch arrival time require elaborate new instrumentation techniques. At the VUV-FEL, two entirely different methods are used. The bunch profile can be determined with high precision by a transverse deflecting RF structure. The method is disruptive and does not allow to monitor multiple bunches in a macro-pulse train. Therefore, it is augmented by two non-disruptive electro-optical devices, called EO and TEO. The EO setup uses a dedicated diagnostic laser synchronized to the machine RF. The longitudinal electron beam profile is encoded in the intensity profile of a chirped laser pulse and analyzed by looking at the spectral composition of the pulse. The second setup, TEO, utilizes the TiSa-based laser system used for pump-probe experiments. Here, the temporal electron shape is encoded into a spatial dimension of laser pulse by an intersection angle between the laser and the electron beam at the EO-crystal. In this paper, we present a comparative study of bunch length and arrival time measurements performed simultaneously with all three experimental techniques.  
 
TUPCH027 Time Resolved Single-shot Measurements of Transition Radiation at the THz Beamline of FLASH using Electro-optic Spectral Decoding radiation, electron, laser, FEL 1058
 
  • B. Steffen, E.-A. Knabbe, B. Schmidt
    DESY, Hamburg
  • G. Berden, A.F.G. van der Meer
    FOM Rijnhuizen, Nieuwegein
  • W.A. Gillespie, P.J. Phillips
    University of Dundee, Nethergate, Dundee, Scotland
  • S.P. Jamison, A. MacLeod
    UAD, Dundee
  • P. Schmüser
    Uni HH, Hamburg
  Single-shot electro-optic detection was used to measure the temporal profile of coherent transition radiation (CTR) pulses at the VUV-FEL at DESY. The CTR was generated from single bunches kicked to an off-axis screen, with the radiation transported through a 20m long transfer line imaging the CTR from a radiation screen to an experimental station outside the accelerator tunnel. Bipolar pulses with a FWHM less than 1ps have been measured and are consistent with simulations of the propagation of radiation through the transfer line.  
 
TUPCH028 Layout of the Optical Synchronization System for FLASH laser, electron, diagnostics, feedback 1061
 
  • A. Winter, P. Schmüser, A. Winter
    Uni HH, Hamburg
  • F. Loehl, F. Ludwig, H. Schlarb, B. Schmidt
    DESY, Hamburg
  The present RF synchronization system of the VUV-FEL can typically stabilize the arrival time of the electron bunches at the undulator to about 200 fs on a timescale of minutes and to several picoseconds on a timescale of hours. To improve the machine stability and to ensure optimal performance for the VUV-FEL user facility, a new ultra-precise timing system is mandatory. The optical synchronization system under construction will satisfy three goals: Firstly, it provides a local oscillator frequency with the same stability as the existing low-level RF regulation, secondly, it can synchronize the experimental lasers of the FEL users with a precision in the order of 30 fs, thirdly, it provides an ultra-stable reference for beam arrival time measurements and enables a feedback on the electron beam to compensate residual drifts and timing jitter. The optical synchronization system is based on an optical pulse train from a mode-locked laser with a highly stabilized repetition rate. This paper describes the proposed layout of the optical synchronization system, the integration into the machine layout and the diagnostic experiments to monitor the performance of the system.  
 
TUPCH029 High-precision Laser Master Oscillators for Optical Timing Distribution Systems in Future Light Sources laser, feedback, FEL, linac 1064
 
  • A. Winter, P. Schmüser, A. Winter
    Uni HH, Hamburg
  • J. Chen, F.X. Kaertner
    MIT, Cambridge, Massachusetts
  • F.O. Ilday
    Bilkent University, Bilkent, Ankara
  • F. Ludwig, H. Schlarb
    DESY, Hamburg
  X-ray pulses with a pulse duration in the 10 fs regime or even less are needed for numerous experiments planned at next generation free electron lasers. A synchronization of probe laser pulses to the x-ray pulses with a stability on the order of the pulse width is highly desirable for these experiments. This requirement can be fulfilled by distributing an ultra-stable timing signal to various subsystems of the machine and to the experimental area to provide synchronization at the fs level over distances of several kilometers. Mode-locked fiber lasers serve as laser master oscillators (LMO), generating the frequencies required in the machine. The pulse train is distributed through length-stabilized fiber links. This paper focuses on the LMO, devoting special attention to the phase noise properties of the frequencies to be generated, its reliability to operate in an accelerator environment, and the residual timing jitter and drifts of the RF feedback for the fiber links. A prototype experimental system has been constructed and tested in an accelerator environment and its performance characteristics will be evaluated.  
 
TUPCH081 Technical Aspects of the Integration of the Optical Replica Synthesizer for the Diagnostics of Ultra-short Bunches in FLASH at DESY laser, electron, undulator, vacuum 1199
 
  • V.G. Ziemann
    UU/ISV, Uppsala
  • N.X. Javahiraly, P. van der Meulen
    FYSIKUM, AlbaNova, Stockholm University, Stockholm
  • M. Larsson
    Stockholm University, Department of Physics, Stockholm
  • E. Saldin, H. Schlarb, E. Schneidmiller, A. Winter, M.V. Yurkov
    DESY, Hamburg
  In this paper we present an overview of current status of the Optical Replica synthesizer at DESY. The method is based on producing an "optical copy" of the electron bunch with its subsequent analysis with optical techniques*. To this end, a near-IR laser beam is superimposed on the electron beam in the first undulator of an optical klystron. In the following dispersive section the laser-induced energy modulation is transformed into a density modulation . The modulated electron bunch then produces a strong optical pulse in the second undulator. Analysis of this near-IR pulse (the optical copy) then provides information about the profile, the slice emittance and the slice energy spread of the electron bunch. We discuss the implementation of such a measurement set-up at the FLASH facility at DESY and investigate the influence of various parameters on the performance of the device. Topics we address include the dispersive chicane, as well as the requirements for the seed laser pulses and the detection and analysis of the near-IR pulse.

*E. Saldin, et al. "A simple method for the determination of the structure of ultrashort relativistic electron bunches," Nucl. Inst. and Methods A 539 (2005) 499.

 
 
TUPCH116 Waveguide Distribution Systems for the European XFEL XFEL, klystron, linac, coupling 1286
 
  • V.V. Katalev, S. Choroba
    DESY, Hamburg
  In the European X-ray FEL 32 superconducting cavities are connected to a 10 MW multibeam klystron through a waveguide distribution system. The basic waveguide system is a linear system. The XFEL tunnel has limited space for the waveguide system and therefore some new compact high power waveguide components like a motor driven phaseshifter, an iris tuner and an asymmetric shunt tee have been developed. Also alternative layouts of the waveguide distribution system which may have certain advantages have been designed. In this report we will present the different layouts and report on the status of the development of the different new waveguide components.  
 
TUPCH117 Experience with the 208MHz and 52MHz RF Systems for the HERA Proton Accelerator feedback, beam-loading, controls, injection 1289
 
  • R. Wagner, S. Choroba, A. Gamp, T.G. Grevsmuehl, G.M. Moeller
    DESY, Hamburg
  • A.B. Bienkowski
    The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
  The RF System for the Hera Proton Ring consists of four 208MHz systems and two 52MHz systems. At injection three of the 208MHz systems are at 70 kV and one System is at 190kV with a phase of 180 degree. The 52 MHz Systems are at 70kV each. During ramping the RF voltage of all cavities follows a ramp table. At flat top at 920GeV both 52 MHz systems are at 50kV and three of the 208MHz Systems are at 190kV while the 180 degree phased system is reduced to 30kV. The typical beam current is 100mA in 180 bunches with a bunch separation of 96 ns. About one year before shutdown of HERA this presentation gives an review of about 14 years operation of the Proton RF System. It is also an overview of the hardware including the beam loading compensation (fast feedback) the tuning system and the other components.  
 
TUPCH187 DSP-based Low Level RF Control as an Integrated Part of DOOCS Control System controls, feedback, linac, electron 1450
 
  • V. Ayvazyan, A. Brandt, O. Hensler, G.M. Petrosyan, L.M. Petrosyan, K. Rehlich, S. Simrock, P. Vetrov
    DESY, Hamburg
  The Distributed Object Oriented Control System (DOOCS) has been developed at DESY as a control system for TTF/VUV-FEL. The DSP based low level RF control system is one of the main subsystems of the linac. Several DOOCS device servers and client applications have been developed to integrate low level RF control into the TTF/VUV-FEL control system. The DOOCS approach defines each hardware device as a separate object and this object is represented in a network by a device server, which handles all device functions. A client application can have access to the server data using the DOOCS application programming interface. A set of generic and specially devoted programs provide the tools for the operators to control the RF system. The RF operation at the linac is being automated by the implementation of DOOCS finite state machine servers.  
 
TUPCH189 FPGA-based RF Field Control at the Photocathode RF Gun of the DESY VUV-FEL controls, gun, FIR, electron 1456
 
  • E. Vogel, W. Koprek, P. Pucyk
    DESY, Hamburg
  At the DESY Vacuum Ultraviolet Free Electron Laser (VUV-FEL) bunch peak current and the SASE effect are (amongst other parameters) sensitive to beam energy and beam phase variations. The electron bunches are created in an rf gun, which does not have field probes. Variations of the gun rf field cause beam energy and phase variations. They have a significant influence on the overall performance of the facility. DSP based rf field control used previously was only able to stabilize the rf output of the klystron. This was due to the lack of processing power and the over-all loop delay. The controller was not able to provide satisfactory rf field stability in the gun. Replacing the DSP hardware by the new FPGA-based hardware Simulation Controller (SimCon), we are able to reduce the latency within the digital part significantly allowing for higher loop gain. Furthermore SimCon provides sufficient processing power for calculating a probe signal from the forward and reflected power as input for PI and adaptive feed forward (AFF) control. In this paper we describe the algorithms implemented and the gun rf field stability obtained.  
 
TUPCH191 Considerations for the Choice of the Intermediate Frequency and Sampling Rate for Digital RF Control controls, feedback, laser, simulation 1462
 
  • S. Simrock, M. Hoffmann, F. Ludwig
    DESY, Hamburg
  • M.K. Grecki, T. Jezynski
    TUL-DMCS, Lodz
  Modern FPGA-based rf control systems employ digital field detectors where an intermediate frequency (IF) in the range of 10 to more than 100 MHz is sampled with a synchronized clock. Present ADC technology with 14-16 bit resolution allows for maximum sampling rates up to 250 MHz. While higher IF's increase the sensitivity to clock jitter, lower IF frequencies are more susceptible to electromagnetic noise. The choice of intermediate frequency and sampling rate should minimize the overall detector noise, provide high measurement bandwidth and low latency in field detection, and support algorithms for optimal field estimation.  
 
TUPLS134 Managing the Quality Assurance Documentation of Accelerator Components Using an EDMS quadrupole, XFEL, TTF, PETRA 1819
 
  • L. Hagge, J. Buerger, J.A. Dammann, J. Kreutzkamp, K. Lappe
    DESY, Hamburg
  Quality assurance (QA) documents are often collected locally on a per-component basis by the manufacturing teams, while project engineers require global evaluations of the QA documents e.g. for production control or during installation and commissioning of the machine. DESY is using an Engineering Data Management System (EDMS) for supporting and unifying the QA documentation of different accelerator components. The EDMS provides dedicated user interfaces which are optimized for the needs of the specific engineering teams which are working on the components (including industrial manufacturers), and at the same time integrates the QA documents into a central database for further overall analysis and applications. The poster introduces the general structure of QA procedures, describes the benefits of using an EDMS for QA documentation and describes examples from different applications at XFEL and PETRA III.  
 
WEPCH015 Measurement and Correction of Dispersion in the VUV-FEL undulator, quadrupole, simulation, electron 1951
 
  • E. Prat, W. Decking, T. Limberg
    DESY, Hamburg
  Increase in transverse beam size in the undulator caused by dispersive effects is one of the major limitations for the operation of FLASH, the VUV-FEL at DESY. Sources of the (spurious) dispersion are field errors and stray magnet fields in the undulator beam line as well as spurious dispersion created upstream of the undulator by, for instance, rf coupler kicks, magnet misalignments and field errors. The impact of these errors on dispersion generation depends on the actual operating conditions of the accelerator, so the dispersion must be measured and controlled frequently. In this paper we present numerical studies of spurious dispersion generation, first dispersion measurements and correction results.  
 
WEPCH114 On the Development of a Self-consistent Particle-in-cell (PIC) Code Using a Time-adaptive Mesh Technique simulation, gun, PITZ, ASTRA 2182
 
  • S. Schnepp, E. Gjonaj, T. Weiland
    TEMF, Darmstadt
  For a large class of problems the self-consistent simulation of charged particle beams in linear accelerators is necessary. Especially, in all low-energetic sections such as injectors the self-consistent interaction of particles and fields has to be taken into account. Well-known programs like the MAFIA TS Modules typically use the Particle-in-cell (PIC) method for beam dynamics simulations. Since they use a fixed computational grid which has to resolve the bunch adequately, they suffer from enormous memory consumption. Therefore and especially in the 3D case, only rather short sections can be simulated. A remedy to this limitation is the usage of a grid which refines itself in the vicinity of particles. For this purpose, a new code called SMOVE based on a time-adaptive grid is being developed. First promising results will be presented at the conference.  
 
WEPCH120 Simulation of 3D Space-charge Fields of Bunches in a Beam Pipe of Elliptical Shape space-charge, ASTRA, simulation, damping 2200
 
  • A. Markovik, G. Pöplau, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock
  • K. Floettmann
    DESY, Hamburg
  Recent applications in accelerator design require precise 3D calculations of space-charge fields of bunches of charged particles additionally taking into account the shape of the beam pipe. An actual problem of this kind is the simulation of e-clouds in damping rings. In this paper a simulation tool for 3D space-charge fields is presented where a beam pipe with an arbitrary elliptical shape is assumed. The discretization of the Poisson equation by the method of finite differences on a Cartesian grid is performed having the space charge field solved only in the points inside the elliptical cross-section of the beam pipe taking care of the conducting boundaries of the pipe. The new routine will be implemented in the tracking code ASTRA. Numerical examples demonstrate the performance of the solution strategy underling the new routine. Further tracking results with the new method are compared to established space-charge algorithms such as the FFT-approach.  
 
WEPCH121 3D Space-charge Calculations for Bunches in the Tracking Code ASTRA space-charge, ASTRA, electron, simulation 2203
 
  • G. Pöplau, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock
  • K. Floettmann
    DESY, Hamburg
  Precise and fast 3D space-charge calculations for bunches of charged particles are of growing importance in recent accelerator designs. One of the possible approaches is the particle-mesh method computing the potential of the bunch in the rest frame by means of Poisson's equation. In that, the charge of the particles are distributed on a mesh. Fast methods for solving Poisson's equation are the direct solution applying Fast Fourier Methods (FFT) and a finite difference discretization combined with a multigrid method for solving the resulting linear system of equations. Both approaches have been implemented in the tracking code ASTRA. In this paper the properties of these two algorithms are discussed. Numerical examples will demonstrate the advantages and disadvantages of each method, respectively.  
 
WEPCH123 Large Simulation of High Order Short Range Wakefields simulation, higher-order-mode, dipole, SLAC 2209
 
  • A. Bungau
    Cockcroft Institute, Warrington, Cheshire
  • R.J. Barlow
    UMAN, Manchester
  We present a formalism for incorporating intra-bunch wake fields into particle-by-particle tracking codes, such as MERLIN and BDSIM. Higher order wake field effects are incorporated in a manner which is computationally efficient. Standard formulae for geometric, resistive and dielectric wake fields are included for various apertures, particularly those relevant for ILC collimators. Numerous examples are given.  
 
WEPLS042 Design and Experimental Investigation of an X-band Multilayer Dielectric Accelerating Structure simulation, impedance, vacuum, coupling 2466
 
  • A. Kanareykin, C.-J. Jing, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio
  • W. Gai, J.G. Power
    ANL, Argonne, Illinois
  A new project to significantly improve the efficiency of high gradient DLA structures is presented. A multilayer DLA where the single dielectric layer is replaced by a multiple coaxial layers of differing permittivity have been developed. The power attenuation in the multilayer structure is reduced by the Bragg Fiber principle where the dielectric layers are used to create multiple reflections in order to confine the accelerating mode fields for the most part in the dielectric, reducing the axial current on the conducting outer boundary. A design for an X-band multilayer structure operating in the TM03 mode using alternating dielectric layers with permittivities of 38 and 9.7 is discussed. In order to transfer the RF from the rectangular waveguide to the cylindrical one at TM03 mode, a special coupling and mode conversion scheme was developed. A prototype structure has been constructed and bench test results of the multilayer 11.424 GHz accelerator is presented.  
 
WEPLS051 Dark Current Investigation of TTF and PITZ RF Guns cathode, gun, PITZ, LEFT 2493
 
  • L. Monaco, P. Michelato, C. Pagani, P. Pierini, D. Sertore
    INFN/LASA, Segrate (MI)
  • J.H. Han, S. Schreiber
    DESY, Hamburg
  • M. Krasilnikov, F. Stephan
    DESY Zeuthen, Zeuthen
  The dark current is one of the limiting factor in the operation of RF guns at high gradient. The continuous request of higher brilliance sources and further emittance minimization, leads to apply higher gradients in the RF gun cavity, with the consequence of a significant dark current production. In this context we set up a collaborative effort to identify the dark current sources in the gun, in order to discriminate between the gun and cathode contribution. A critical analysis and organization of dark current measurements, taken during the operation of TTF and PITZ guns, with several cathodes operated at different accelerating fields and solenoids focusing, is presented. Potential areas of improvement are also discussed, together with a possible associated program.  
 
WEPLS096 Design and Calculation of a Superferric Combined Magnet for XFEL quadrupole, dipole, XFEL, background 2598
 
  • F. Toral, P. Abramian, J.L. Gutierrez, E. Rodriguez, I. Rodriguez, S. Sanz, C. Vazquez
    CIEMAT, Madrid
  • R. Bandelmann, H. Brueck
    DESY, Hamburg
  • J. Calero, L. García-Tabarés
    CEDEX, Madrid
  • J. Lucas
    Elytt Energy, Madrid
  A planned European X-ray Free Electron Laser so-called XFEL is being developed within the framework of an international collaboration. The design and fabrication of a prototype of a combined magnet is part of the Spanish contribution to this project. This magnet consists of a superferric quadrupole for focusing and two dipoles (horizontal and vertical) for steering, glued around the beam tube. The magnet will be operated in a superfluid helium bath. The aperture is 78 mm. The quadrupole gradient is 35 T/m whereas each dipole field is about 0.04 T. The magnetic saturation is limited to 5% at nominal current, which is quite a challenging specification for such aperture and gradient. As the overall length of the helium vessel is just 300 mm, the calculation of the magnetic field is a pure 3-D problem which has been solved and optimized using two different FEM codes to cross-check the results. This paper also gives some guidelines about the fabrication techniques most suitable for the first prototype, which is now under construction.  
 
THPPA02 High-Gradient Superconducting Radiofrequency Cavities for Particle Acceleration TESLA, XFEL, radio-frequency, acceleration 2752
 
  • L. Lilje
    DESY, Hamburg
  The development of radiofrequency superconductivity for particle acceleration has reached a level where many projects consider its use. One of the many attractive features of these accelerating structures is to achieve very high accelerating fields efficiently. The technology has been developped to a stage where accelerating gradients of more than 25 MV/m are being implemented in accelerator modules. In single-cell test resonators even higher gradients were already achieved. To operate cavities at these gradients efficiently their frequency needs to be kept stable to reduce the need for an overhead in radiofrequency power. Introducing active elements like piezoelectric actuators allows to achieve these goals.  
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THOBFI01 A Sub 100 fs Electron Bunch Arrival-time Monitor System for FLASH laser, pick-up, electron, FEL 2781
 
  • F. Loehl, K.E. Hacker, F. Ludwig, H. Schlarb, B. Schmidt
    DESY, Hamburg
  • A. Winter
    Uni HH, Hamburg
  The stability of free-electron lasers and experiments carried out in pump-probe configurations depends sensitively on precise synchronization between the photo-injector laser, low-level RF-systems, probe lasers, and other components in the FEL. A measurement of the jitter in the arrival-time of the electron bunch with respect to the clock signal of a master oscillator is, therefore, of special importance. For this task, we propose an arrival-time monitor based on a beam pick-up with more than 10GHz bandwidth which permits measurements in the sub 100 fs regime. The RF-signal from the beam pick-up is sampled by an ultra-short laser pulse using a broad-band electro-optical modulator. The modulator converts the electron bunch arrival-time jitter into an amplitude modulation of the laser pulse. This modulation is detected by a photo detector and sampled by a fast ADC. By directly using the laser pulses from the master laser oscillator of the machine, any additional timing jitter is avoided. In this paper we present the layout of the system and first experimental results.  
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THPCH036 Wakefield Calculations for 3D Collimators SLAC, simulation, LEFT, impedance 2859
 
  • I. Zagorodnov
    DESY, Hamburg
  • K.L.F. Bane
    SLAC, Menlo Park, California
  The wakefield effects of the collimators is of concern for future projects. To relax the wakefield effects a gradual transition from a large to a small aperture is used. The impedance of a smooth round collimator is understood well and a good agreement between measurements, theory and simulations is achieved. However, for rectangular flat collimators there is noticeable difference between theory and experiment. Using recently developed time domain numerical approach, which is able to model curved boundaries and does not suffer from dispersion in longitudinal direction, we calculate the short-range geometric wakefields of 3D collimators. This method together with developed by us recently indirect 3D integration algorithm allows to obtain accurate numerical estimations, which are compared to measurements and to analytical results. The applicability range for the analytical formulas is highlighted.  
 
THPCH037 Wakefields Effects of New ILC Cavity Shapes linac, emittance, TESLA, simulation 2862
 
  • I. Zagorodnov
    DESY, Hamburg
  • N. Solyak
    Fermilab, Batavia, Illinois
  The operation of International Linear Collider (ILC) requires high gradients and quality factors in accelerating structure. One way to reach it is to modify the cavity shape to reduce the ratio of peak surface magnetic to accelerating field. Two candidate shapes are suggested recently: the Re-entrant shape and the Low-Loss shape. In this paper we estimate numerically longitudinal and transverse short range wake functions for the new shapes. The obtained analytical expressions are used in beam dynamic simulations for ILC lattice. We show that ILC will tolerate the cavities with the new shape and the smaller iris diameter.  
 
THPCH110 The New Control System for the Future Low-emittance Light Source PETRA 3 at DESY controls, PETRA, linac, synchrotron 3059
 
  • R. Bacher
    DESY, Hamburg
  At DESY, the existing high-energy physics booster synchrotron PETRA 2 will be transformed into a 3rd-generation light source (PETRA 3) after the final shutdowm of HERA operation mid 2007. In addition, the technical systems and components of the pre-accelerators LINAC 2 and DESY 2 will be improved. Within the scope of this project, the control system and the front-end electronics will be upgraded. Key elements of the conceptual design are TINE (Threefold Integrated Network Environment) as integrating software bus to provide efficient data communication mechanisms and support services, control room applications based on the thick-client model for optimum visualization and performance and Java as programming language to ensure platform independence, server-side control APIs in various languages to allow choice of the language that is best suited for the control task to be done, a common device interface for generic access to various field buses, and CANopen as interface standard for device electronics to ensure long-term maintenance. The complete conceptual design and the current project status will be presented.  
 
THPCH175 Automatic Resonant Excitation Based System for Lorentz Force Compensation for Flash controls, radio-frequency, resonance, injection 3206
 
  • P.M. Sekalski, A. Napieralski
    TUL-DMCS, Lodz
  • S. Simrock
    DESY, Hamburg
  The cavity is the key element of each linear accelerator used for high-energy physics purpose. The resonant frequency of cavities depends on its shape. Due to the pulse operation, they are deformed by dynamic Lorentz force (LF) caused by accelerating electromechanical field. As a consequence, the cavities are not working on resonance but they are detuned from master oscillator frequency by few hundreds of Hertz depending on accelerating field gradient. The paper presents an automatic control system for LF compensation applied to fast tuning mechanism CTS. The active element is multilayer low-voltage piezoelectric stack (EPCOS). The resonant excitation with adaptive feed forward algorithm is used to drive the actuator. Test performed at FLASH (former name VUV-FEL) on cav5/ACC1 showed that detuning during flat-top period (800us) might remain below 10Hz for accelerating field gradient of 20MV/m.  
 
THPLS020 Progress Report on PETRA III PETRA, wiggler, vacuum, emittance 3317
 
  • K. Balewski
    DESY, Hamburg
  Starting from the middle of 2007, the existing storage ring PETRA II at DESY will be converted into the hard x-ray light source PETRA III. The project was launched in 2002, and in preparation of the conversion a technical design report was published in 2004. Since then detailed design and construction of technical components have begun. Prototypes have been built and tested and the procurement of major parts of the machine components such as magnets and vacuum chambers has started. The project is well underway and in line with the goal of starting the rebuilding in 2007 and the commissioning in 2009. In addition to an overall status report, the development of components and measurement results of prototypes will be presented.  
 
THPLS092 Nb-Pb Superconducting RF-Gun dipole, cathode, laser, emittance 3493
 
  • J.S. Sekutowicz, J.I. Iversen, D. Klinke, D. Kostin, W.-D. Möller
    DESY, Hamburg
  • I. Ben-Zvi, A. Burrill, T. Rao, J. Smedley
    BNL, Upton, Long Island, New York
  • M. Ferrario
    INFN/LNF, Frascati (Roma)
  • P. Kneisel
    Jefferson Lab, Newport News, Virginia
  • K. Ko, L. Xiao
    SLAC, Menlo Park, California
  • J. Langner, P. Strzyzewski
    The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
  • R.S. Lefferts, A.R. Lipski
    SBUNSL, Stony Brook, New York
  • J.B. Rosenzweig
    UCLA, Los Angeles, California
  • K. Szalowski
    University of Lodz, Lodz
  We report on the status of an electron RF-gun made of two superconductors: niobium and lead. The presented design combines the advantages of the RF performance of bulk niobium superconducting cavities and the reasonably high quantum efficiency of lead, as compared to other superconducting metals. The concept, mentioned in a previous paper, follows the attractive approach of all niobium superconducting RF-gun as it has been proposed by the BNL group. Measured values of quantum efficiency for lead at various photon energies, analysis of recombination time of photon-broken Cooper pairs for lead and niobium, and preliminary cold test results are discussed in this paper.  
 
THPLS121 Status of the PETRA III Damping Wigglers wiggler, damping, vacuum, PETRA 3565
 
  • M. Tischer, K. Balewski, M. Seidel, L. Yongjun
    DESY, Hamburg
  • A.A. Krasnov, V. Kuzminykh, E. Levichev, P. Vobly, K. Zolotarev
    BINP SB RAS, Novosibirsk
  After mid-2007, the present PETRA storage ring at DESY will be reconstructed towards a dedicated third generation light source operating at 6 GeV. An emittance reduction down to 1 nm can be achieved by means of damping wigglers. 20 permanent magnet wigglers will be installed in two of the long straights of the machine. The wiggler segments are compact fixed gap devices surrounded by iron enclosures to reduce the leakage flux. Each device will provide a damping integral of 4 T2m per segment and generate a synchrotron radiation power of 42 kW. Every wiggler segment will be followed by an SR-absorber to protect all downstream components, the accumulated on-axis power of about 200 kW will be taken up by a final absorber at the damping section end. The wiggler's magnetic design, field properties and correction schemes have previously been proven by a one period long prototype. At present, the first full length (4m) prototype wiggler has been assembled and characterized magnetically.