Author: Schlarb, H.
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TUB04 Operation of FLASH with Short SASE-FEL Radiation Pulses 342
  • J. Rönsch-Schulenburg, E. Hass, N.M. Lockmann, T. Plath, M. Rehders, J. Roßbach
    Uni HH, Hamburg, Germany
  • G. Brenner, S. Dziarzhytski, T. Golz, H. Schlarb, B. Schmidt, E. Schneidmiller, S. Schreiber, B. Steffen, N. Stojanovic, S. Wunderlich, M.V. Yurkov
    DESY, Hamburg, Germany
  Funding: The project has been supported by the Federal Ministry of Education and Research of Germany (BMBF) under contract No. 05K10GU2 and FSP301
This paper describes the experimental activity on the generation of very short FEL pulses in the soft x-ray range in the SASE-mode at the high-gain free-electron laser FLASH [1, 2]. The key element, a photo-injector laser which is able to generate laser pulses of about 2 ps FWHM has been optimized and commissioned. It allows the generation of shorter bunches with low bunch charge (of up to 200 pC) directly at the photo-cathode. Initially shorter injector laser pulses and thus shorter bunches eases the required bunch compression factor for short pulses below 10 fs duration which makes operation of the electron beam formation system to be more robust with respect to jitters and collective effects. As a result, overall stability of SASE FEL performance is improved. In the optimal case single-spike operation can be achieved. In this paper the experimental results on production of short electron bunches and the SASE performance using the new injector laser will be shown and the measured electron bunch and FEL radiation properties are discussed. In addition, optimizations of bunch diagnostics for low charge and short bunches are discussed.
slides icon Slides TUB04 [1.201 MB]  
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.  
THP076 Measurements of the Timing Stability at the FLASH1 Seeding Experiment 913
  • C. Lechner, A. Azima, M. Drescher, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Rönsch-Schulenburg, J. Roßbach, M. Wieland
    Uni HH, Hamburg, Germany
  • S. Ackermann, J. Bödewadt, H. Dachraoui, N. Ekanayake, B. Faatz, M. Felber, K. Honkavaara, T. Laarmann, J.M. Mueller, H. Schlarb, S. Schreiber, S. Schulz
    DESY, Hamburg, Germany
  • G. Angelova Hamberg
    Uppsala University, Uppsala, Sweden
  • K.E. Hacker, S. Khan, R. Molo
    DELTA, Dortmund, Germany
  • P.M. Salen, P. van der Meulen
    FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden
  Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K10PE1, 05K10PE3, 05K13GU4 and 05K13PE3 and the German Research Foundation programme graduate school 1355.
For seeding of a free-electron laser, the spatial and temporal overlap of the seed laser pulse and the electron bunch in the modulator is critical. To establish the temporal overlap, the time difference between pulses from the seed laser and spontaneous undulator radiation is reduced to a few pico-seconds with a combination of a photomultiplier tube and a streak camera. Finally, for the precise overlap the impact of the seed laser pulses on the electron bunches is observed. In this contribution, we describe the current experimental setup, discuss the techniques applied to establish the temporal overlap and analyze its stability.
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.