Author: Gerth, C.
Paper Title Page
Synchrotron Radiation Monitor for Beam Energy Measurements at the European XFEL  
  • M. Sachwitz, N. Leuschner, F. Perlick
    DESY Zeuthen, Zeuthen, Germany
  • C. Gerth, H. Huegelmann
    DESY, Hamburg, Germany
  Monitoring of the electron beam energies after the various accelerating sections of the European XFEL is essential for an optimal beam delivery system. Synchrotron radiation that is emitted in the dispersive section of the magnetic chicanes employed for longitudinal bunch compression can be used to determine the energy spectrum of the electron bunches. At European XFEL, vacuum chambers with an aperture of 400 mm will be installed for flexible operation of different bunch compression scenarios. Therefore, the in-vacuum mirror deflecting the visible light through a vacuum window to a camera is located on a motor driven carrier. An additional mover allows an angular adjustment of the mirror. In this paper we report on the conceptual design of the synchrotron monitor. Results obtained with a prototype setup in the laboratory are presented and several options for the synchrotron light detection are discussed.  
Recent Developments for the Improved Bunch Arrival Time Monitors at FLASH and for the European XFEL  
  • M.K. Czwalinna, H. Dinter, C. Gerth, H. Schlarb
    DESY, Hamburg, Germany
  • S. Bou Habib
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  • J. Szewiński
    NCBJ, Świerk/Otwock, Poland
  At today's free-electron lasers, pump-probe experiments and seeding schemes put high demands on the timing stability of electron bunches. At FLASH and the upcoming European XFEL a reliable and precise arrival time detection down to the femtosecond level has to cover a broad range of bunch charges, which may even change from 1 nC down to 20 pC within a bunch train. At FLASH, the new bunch arrival time monitor has to cope with the special operation mode where the MHz repetition rate bunch train is separated into two segments for FLASH1 and FLASH2 beam lines. Each of the two segments will exhibit individual timing jitter characteristics since they are generated from two different injector lasers and can be accelerated with individual energy gain settings. This operation mode places high demands on both, the hardware and the required servers for the bunch arrival time monitor, with regard to automated control and exception handling. In this paper, we describe the adapted electro-optical subsystem and show latest results from the newly implemented read-out electronics based on the MTCA.4 platform.  
THP069 Performance Study of High Bandwidth Pickups Installed at FLASH and ELBE for Femtosecond-Precision Arrival Time Monitors 893
  • M.K. Czwalinna, C. Gerth, H. Schlarb, C. Sydlo
    DESY, Hamburg, Germany
  • A. Angelovski, R. Jakoby, A. Penirschke
    TU Darmstadt, Darmstadt, Germany
  • M. Gensch, M. Kuntzsch
    HZDR, Dresden, Germany
  • M. Kuntzsch
    TU Dresden, Dresden, Germany
  • T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  At today's free-electron lasers, high-resolution electron bunch arrival time measurements have become increasingly more important in fast feedback systems for a timing jitter reduction down to the femtosecond level as well as for time-resolved pump-probe experiments. This is fulfilled by arrival time monitors which employ an electro-optical detection scheme by means of synchronised ultrashort laser pulses. Even more, at FLASH and the European XFEL the measurement has to cover a wide range of bunch charges from 1 nC down to 20 pC with equally sub-10 fs resolution. To meet these requirements, recently a high bandwidth pickup electrode with a cut-off frequency above 40 GHz has been developed. These pickups are installed at the macro-pulsed SRF accelerator of the free-electron laser FLASH and at the macro-pulsed continuous wave SRF accelerator ELBE. In this paper we present an evaluation of the pickup performance by direct signal measurements with high bandwidth oscilloscopes and by use of the electro-optical arrival time monitor.  
THP075 Design of TDS-based Multi-screen Electron Beam Diagnostics for the European XFEL 909
  • J. Wychowaniak
    TUL-DMCS, Łódź, Poland
  • C. Gerth, M. Yan
    DESY, Hamburg, Germany
  Dedicated longitudinal electron beam diagnostics is essential for successful operation of modern free-electron lasers. Demand for diagnostic data includes the longitudinal bunch profile, bunch length and slice emittance of the electron bunches. Experimental setups based on transverse deflecting structures (TDS) are excellent candidates for this purpose. At the Free-Electron Laser in Hamburg (FLASH), such a longitudinal bunch profile monitor utilizing a TDS, a fast kicker magnet and an off-axis imaging screen, has been put into operation. It enables the measurement of a single bunch out of a bunch train without affecting the remaining bunches. At the European X-ray Free-Electron Laser (XFEL) multiscreen stations in combination with TDS are planned to be installed. In order to allow for flexible measurements of longitudinal bunch profile and slice emittance, a configurable timing and trigger distribution to the fast kicker magnets and screen stations is required. In this paper, we discuss various operation patterns and the corresponding realization based on MTCA.4 technology.  
THP083 Coherent Radiation Diagnostics for Longitudinal Bunch Characterization at European XFEL 925
  • P. Peier, H. Dinter, C. Gerth
    DESY, Hamburg, Germany
  European XFEL comprises a 17.5 GeV linear accelerator for the generation of hard X-rays. Electron bunches from 20 pC to 1 nC will be produced with a length of a few ps in the RF gun and compressed by three orders of magnitude in three bunch compressor (BC) stages. European XFEL is designed to operate at 10 Hz delivering bunch trains with up to 2700 bunches separated by 222 ns. The high intra-bunch train repetition rate offers the unique possibility of stabilizing the machine with an intra-bunch train feedback, which puts in turn very high demand on fast longitudinal diagnostics. Two different systems will be installed in several positions of the machine. Five bunch compression monitors (BCM) will monitor the compression factor of each BC stage and used for intra-bunch train feedbacks. A THz spectrometer will be used to measure parasitically the longitudinal bunch profile after the energy collimator at 17.5 GeV beam energy. We will present concepts for fast longitudinal diagnostic for European XFEL based on coherent radiation, newest developments for high repetition rate measurements and simulations for the feedback capability of the system.  
THP088 Comparison of Quadrupole Scan and Multi-screen Method for the Measurement of Projected and Slice Emittance at the SwissFEL Injector Test Facility 941
  • M. Yan, B. Beutner, C. Gerth
    DESY, Hamburg, Germany
  • R. Ischebeck, E. Prat
    PSI, Villigen PSI, Switzerland
  High-brightness electron bunches with small transverse emittance are required to drive X-ray free-electron lasers (FELs). For the measurement of the transverse emittance, the quadrupole scan and multi-screen methods are the two most common procedures. By employing a transverse deflecting structure, the measurement of the slice emittance becomes feasible. The quadrupole scan is more flexible in freely choosing the data points during the scan, while the multi-screen method allows on-line emittance measurements utilising off-axis screens in combination with fast kicker magnets. The latter is especially the case for high-repetition multi-bunch FELs, such as the European XFEL, which offer the possibility of on-line diagnostics. In this paper, we present comparative measurements of projected and slice emittance applying these two methods at the SwissFEL Injector Test Facility and discuss the implementation of on-line diagnostics at the European XFEL.  
Compact Synchronization of Optical Lasers to the Accelerator RF based on MTCA.4  
  • C. Gerth, Ł. Butkowski, M. Felber, U. Mavrič, P. Peier, H. Schlarb, B. Steffen
    DESY, Hamburg, Germany
  • E. Janas
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  • T. Kozak, P. Prędki, K.P. Przygoda
    TUL-DMCS, Łódź, Poland
  X-ray free-electron laser facilities utilize a variety of optical short-pulse lasers to fully exploit the femtosecond time structure of the electron bunches and photon pulses. For temporal overlap, a precision synchronization of the optical lasers to the radio-frequency (RF) system of the FEL accelerator is required. A compact scheme for laser to external RF synchronization has been developed based on a digital controller implemented in MTCA.4 technology. An RF section is employed for the generation of electrical signals from the laser pulses. Further processing of the RF signals and phase locking to the reference is realized with commercially available MTCA.4 compliant modules. In this paper, we present a performance evaluation of the newly designed RF section, which consists of three printed circuit boards, as well as results from the synchronization of an Yb-fiber (1030 nm) and Er-fiber (1550 nm) laser to an RF reference source.  
THP090 Femtosecond Timing Distribution for the European XFEL 945
  • 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
  Accurate timing synchronization on the femtosecond timescale is an essential installation for time-resolved experiments at free-electron lasers (FELs) such as FLASH and the upcoming European XFEL. To date the required precision levels can only be achieved by a laser-based synchronization system. Such a system has been successfully deployed at FLASH and is based on the distribution of femtosecond laser pulses over actively stabilized optical fibers. Albeit its maturity and proven performance this system had to undergo a major redesign for the upcoming European XFEL due to the enlarged number of stabilized optical fibers and an increase by a factor of up to 10 in length. The experience and knowledge gathered from the operation of the optical synchronization system at FLASH has led to an elaborate and modular precision instrument which can stabilize polarization maintaining fibers for highest accuracy as well as economic single mode fibers for shorter lengths. This paper reports on the laser-based synchronization system focusing on the active fiber stabilization units for the European XFEL, discusses major complications, their solutions and and the most recent performance results.