Author: Gerth, C.
Paper Title Page
MOPC32 Development Status of Optical Synchronization for the European XFEL 135
  • C. Sydlo, M.K. Czwalinna, M. Felber, C. Gerth, T. Lamb, H. Schlarb, S. Schulz, F. Zummack
    DESY, Hamburg, Germany
  • S. Jabłoński
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  Precise timing synchronization on the femtosecond timescale is crucial for time resolved experiments at modern free-electron lasers (FELs) like FLASH and the upcoming European XFEL. The required precision can only be achieved by a laser-based synchronization system. The pulsed laser-based scheme at FLASH, based on the distribution of femtosecond laser pulses over actively stabilized optical fibers, has evolved over the years from a prototype setup to a mature and reliable system. At the same time, the present implementation serves as prototype for the synchronization infrastructure at the European XFEL. Due to a factor of ten increase of the length of the accelerator and an increased number of timing-critical subsystems, new challenges arise. This paper reports on the current development progress of the XFEL optical synchronization, discusses major complications and their solutions.  
MOPC37 Longitudinal Bunch Profile Reconstruction Using Broadband Coherent Radiation at FLASH 154
  • E. Hass
    Uni HH, Hamburg, Germany
  • C. Behrens, C. Gerth, B. Schmidt, M. Yan
    DESY, Hamburg, Germany
  • S. Wesch
    HZB, Berlin, Germany
  The required high peak current in free-electron lasers is realized by longitudinal compression of the electron bunches to sub-picosecond length. Measurement of the absolute spectral intensity of coherent radiation emitted by an electron bunch allows monitoring and reconstruction of the longitudinal bunch profile. To measure coherent radiation in the teraherz and infrared range a in-vacuum coherent radiation intensity spectrometer was developed for the free-electron laser in Hamburg(FLASH). The spectrometer is equipped with five consecutive dispersion gratings and 120 parallel readout channels: it can be operated either in short (5-44 um) or in long wavelength mode (45-430 um). Fast parallel readout permits the monitoring of coherent radiation from single electron bunches. Large wavelength coverage and superb absolute calibration of the device allows reconstruction of the longitudinal bunch profile using Kramers-Kronig based phase retrieval technique. The device is used as a bunch length monitor and tuning tool during routine operation at FLASH. Comparative measurements with radio-frequency transverse deflecting structure show excellent agreement of both methods.  
TUPC29 Grounded Coplanar Waveguide Transmission Lines as Pickups for Beam Position Monitoring in Particle Accelerators 438
  • A. Penirschke, A. Angelovski, R. Jakoby
    TU Darmstadt, Darmstadt, Germany
  • C. Gerth, U. Mavrič, D. Nölle, C. Sydlo, S. Vilcins
    DESY, Hamburg, Germany
  Funding: The work was supported by the MSK group at DESY Hamburg. The authors would like to thank the CST AG for providing the CST Software Package.
Energy beam position monitors (EBPM) based on grounded co-planar waveguide (GCPW) transmission lines have been designed for installation in the dispersive sections of the bunch compressor chicanes at the European XFEL. In combination with beam position monitors at the entrance and exit of the bunch compressor chicanes, measurements of the beam energy with single bunch resolution are feasible. The EBPM consists of transversely mounted stripline pickups in a rectangular beam pipe section. The signal detection for the measurement of the phases of the pulses at each end of the pickups is based on the standard down-conversion and phase detection scheme used for the low-level RF-system. A measurement resolution within the lower micrometer range can be achieved for input signal reflections at the pickup of less than -25 dB at 3 GHz. In this paper, simulation results of a novel pickup geometry utilized with GCPW pickup structures and optimized transitions to perpendicular mounted coaxial connectors are presented. The simulation results exhibit small reflection coefficients with reflected signal components having less than 2% of the peak voltage signal.
TUPC33 Femtosecond Stable Laser-to-RF Phase Detection for Optical Synchronization Systems 447
  • T. Lamb, M.K. Czwalinna, M. Felber, C. Gerth, H. Schlarb, S. Schulz, C. Sydlo, M. Titberidze, F. Zummack
    DESY, Hamburg, Germany
  • E. Janas
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  • J. Szewiński
    NCBJ, Świerk/Otwock, Poland
  Optical reference distributions have become an indispensable asset for femtosecond precision synchronization of free-electron lasers. At FLASH and for the future European XFEL, laser pulses are distributed over large distances in round-trip time stabilized fibers to all critical facility sub-systems. Novel Laser-to-RF phase detectors will be used to provide ultra phase stable and long-term drift free microwave signals for the accelerator RF controls. In this paper, we present the recent progress on the design of a fully integrated and engineered version of the L2RF phase detector, together with first experimental results demonstrating so-far unrivaled performance.  
poster icon Poster TUPC33 [18.910 MB]  
TUPC34 Precision Synchronization of Optical Lasers Based on MTCA.4 Electronics 451
  • U. Mavrič, Ł. Butkowski, H.T. Duhme, M. Felber, M. Fenner, C. Gerth, P. Peier, H. Schlarb, B. Steffen
    DESY, Hamburg, Germany
  • T. Kozak, P. Predki
    TUL-DMCS, Łódź, Poland
  Optical laser have become an integral part of free-electron laser facilities for the purposes of electron bunch generation, external seeding, diagnostics and pump-probe experiments. The ultra-short electron bunches demand a high timing stability and precision synchronization of the optical lasers. In this paper, we present the proof-of-principle for a laser locking application implemented on a MTCA.4 platform. The system design relies on existing MTCA.4 compliant off-the-shelf modules that are available on the market or have been developed for other applications within the particle accelerator community. Besides performance and cost, we also tried to minimize the number of out-of-crate components. Preliminary measurements of laser locking at the FLASH and REGAE particle accelerators are presented, and an outlook for further system development in the area of laser-to-RF synchronization is given.  
TUPC35 Upgrade of the Read-out Electronics for the Energy Beam Position Monitors at FLASH and European XFEL 454
  • U. Mavrič, C. Gerth, H. Schlarb
    DESY, Hamburg, Germany
  • A. Piotrowski
    TUL-DMCS, Łódź, Poland
  The dispersive sections of magnetic bunch compressor chicanes at free-electron lasers are excellent candidates for beam energy measurements. In the rectangular beamline sections of the bunch compressors at FLASH, energy beam position monitors (EBPM) with transversely mounted stripline pickups are installed. In this paper, we present the upgrade of the read-out electronics for signal detection of the EBPM installed at FLASH. The system is based on the MTCA.4 standard and reuses already available MTCA.4 compliant modules. This is also true for gateware and software development which fits into standard MTCA.4 framework development. The performance of the instrument was studied at FLASH during user operation and the results are presented.  
TUPC36 First Realization and Performance Study of a Single-Shot Longitudinal Bunch Profile Monitor Utilizing a Transverse Deflecting Structure 456
  • M. Yan, C. Behrens, C. Gerth, R. Kammering, A. Langner, F. Obier, V. Rybnikov
    DESY, Hamburg, Germany
  • J. Wychowaniak
    TUL-DMCS, Łódź, Poland
  For the control and optimization of electron beam parameters at modern free-electron lasers (FEL), transverse deflecting structures (TDS) in combination with imaging screens have been widely used as robust longitudinal diagnostics with single-shot capability, high resolution and large dynamic range. At the free-electron laser in Hamburg (FLASH), a longitudinal bunch profile monitor utilizing a TDS has been realized. In combined use with a fast kicker magnet and an off-axis imaging screen, selection and measurement of a single bunch out of the bunch train with bunch spacing down to 1us can be achieved without affecting the remaining bunches which continue to generate FEL radiation during user operation. Technical obstacles have been overcome such as suppression of coherent transition radiation from the imaging screen, the continuous image acquisition and processing with the bunch train repetition rate of 10Hz. The monitor, which provides the longitudinal bunch profile and length, has been used routinely at FLASH. In this paper, we present the setup and operation of the longitudinal bunch profile monitor as well as the performance during user operation.  
WEPC31 New Design of the 40 GHz Bunch Arrival Time Monitor Using MTCA.4 Electronics at FLASH and for the European XFEL 749
  • M.K. Czwalinna, C. Gerth, H. Schlarb
    DESY, Hamburg, Germany
  • S. Bou Habib
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  • S. Korolczuk, J. Szewiński
    NCBJ, Świerk/Otwock, Poland
  • A. Kuhl
    Uni HH, Hamburg, Germany
  At free-electron lasers, today's pump-probe experiments and seeding schemes make high demands on the electron bunch timing stability with an arrival time jitter reduction down to the femtosecond level. At FLASH and the upcoming European XFEL, the bunch train structures with their high bunch repetition rates allow for an accurate intra-train stabilisation. To realise longitudinal beam-based feedbacks a reliable and precise arrival time detection over a broad range of bunch charges, which can even change from 1 nC down to 20 pC within a bunch train, is essential. Benefitting from the experience at FLASH, the current bunch arrival time monitors (BAMs), based on detection of RF signals from broad-band pick-ups by use of electro-optic modulators, are further developed to cope with the increased requirements. In this paper, we present the new BAM prototype, including an adapted electro-optical front-end and the latest development of the read-out electronics based on the MTCA.4 platform.  
WEPC41 Comparative Analysis of Different Electro-Optical Intensity Modulator Candidates for the New 40 GHz Bunch Arrival Time Monitor System for FLASH and European XFEL 782
  • A. Kuhl, J. Rönsch-Schulenburg, J. Roßbach
    Uni HH, Hamburg, Germany
  • M.K. Czwalinna, C. Gerth, H. Schlarb, C. Sydlo
    DESY, Hamburg, Germany
  • S. Schnepp
    ETH Zurich, Institute of Electromagnetic Fields (IFH), Zurich, Switzerland
  • T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  Funding: The work is supported by Federal Ministry of Education and Research of Germany (BMBF) within FSP 301 under the contract numbers 05K10GU2 and 05K10RDA.
The currently installed Bunch Arrival time Monitors (BAMs) at the Free electron LASer in Hamburg (FLASH) achieved a time resolution of less than 10 fs for bunch charges higher than 500 pC. In order to achieve single spike FEL pulses at FLASH, electron bunch charges down to 20 pC are of interest. With these BAMs the required time resolution is not reachable for bunch charges below 500 pC. Therefore new pickups with a bandwidth of up to 40 GHz are designed and manufactured*. The signal evaluation takes place with a time-stabilized reference laser pulse train which is modulated with an Electro-Optical intensity Modulator (EOM). The new BAM system also requires new EOMs for the electro-optical frontend. The available selection of commercial EOM candidates for the new frontend is very limited. In this paper we present a comparison between different EOM candidates for the new electro optical frontend.
* A. Angelovski et al. Proceedings Phys. Rev ST AB, DOI:10.1103/PhysRevSTAB.15.112803
poster icon Poster WEPC41 [0.619 MB]