Author: Schlarb, H.
Paper Title Page
Longitudinal Bunch Shape Control and Feedback in FEL Driver Linear Accelerators  
  • H. Schlarb
    DESY, Hamburg, Germany
  This presentation should include a description of precise manipulation of the longitudinal bunch shape in the FEL driver linear accelerators. It should review the diagnostic devices and feedback strategies that are implemented and planned at FEL facilities worldwide.  
slides icon Slides WEYB201 [6.475 MB]  
WEPWA009 RF Bunch Compression Studies for FLUTE 2144
  • M. Schuh, E. Huttel, S. Marsching, A.-S. Müller, S. Naknaimueang, M.J. Nasse, R. Rossmanith, R. Ruprecht, M. Schreck, M. Schwarz, M. Weber, P. Wesolowski
    KIT, Karlsruhe, Germany
  • R.W. Aßmann, K. Flöttmann, H. Schlarb
    DESY, Hamburg, Germany
  FLUTE is a planned 40 to 50 MeV accelerator test facility consisting, in the first phase, of an electron gun with an output energy of about 7 MeV, a traveling wave linac and a magnet chicane bunch compressor. The machine will serve as a source of intense THz radiation using coherent synchrotron radiation (CSR), coherent transition radiation (CTR), and coherent edge radiation (CER) as generation mechanisms. It is planned to operate the machine in the charge regime from a few pC up to several nC in order to study bunch compression schemes as well as the THz radiation generation. In this contribution the effect of velocity bunching by using a dedicated buncher cavity at low energy and operating the linac off-crest is studied in order to deliver RMS bunch lengths in the femtosecond range at low charge.  
WEPWA010 FLUTE: A Versatile Linac-based THz Source Generating Ultra-short Pulses 2147
  • M.J. Nasse, E. Huttel, S. Marsching, A.-S. Müller, S. Naknaimueang, R. Rossmanith, R. Ruprecht, M. Schreck, M. Schuh, M. Schwarz, P. Wesolowski
    KIT, Karlsruhe, Germany
  • R.W. Aßmann, M. Felber, K. Flöttmann, M. Hoffmann, H. Schlarb
    DESY, Hamburg, Germany
  • H.-H. Braun, R. Ganter, L. Stingelin
    PSI, Villigen PSI, Switzerland
  FLUTE is a linac-based accelerator test facility and a THz source currently being constructed at KIT with an electron beam energy of ~41 MeV. It is designed to cover a large charge range from a few pC to ~3 nC. FLUTE is optimized to provide ultra-short electron bunches with an RMS length down to a few fs. In this contribution, we focus on the layout of the machine from the RF gun & gun laser over the linac and the compressor to the THz beamline for the generation of coherent synchrotron, transition and edge radiation (CSR, CTR, CER).  
poster icon Poster WEPWA010 [0.802 MB]  
WEPME006 Optical Synchronization and Electron Bunch Diagnostic at ELBE 2932
  • M. Kuntzsch, M. Gensch, U. Lehnert, F. Röser, R. Schurig
    HZDR, Dresden, Germany
  • M. Bousonville, M.K. Czwalinna, H. Schlarb, S. Schulz, S. Vilcins
    DESY, Hamburg, Germany
  The continuous wave electron accelerator ELBE is upgraded to generate short and highly charged electron bunches (~200fs duration, up to 1 nC) . In the last years a prototype of an optical synchronization system using a mode locked fiber laser has been build up at ELBE which is now in commissioning phase. The stabilized pulse train can be used for new methods of electron bunch diagnostics like bunch arrival time measurements with the potential of femtosecond resolution. At ELBE a bunch arrival time monitor (BAM) has been designed and tested at the accelerator. The contribution will show the design of the BAM and first measurement results at the ELBE accelerator.  
WEPME008 Precision LLRF Controls for the S-Band Accelerator REGAE 2938
  • M. Hoffmann, H. Kay, U. Mavrič, H. Schlarb, Ch. Schmidt
    DESY, Hamburg, Germany
  • W. Jałmużna, T. Kozak, A. Piotrowski
    TUL-DMCS, Łódź, Poland
  The linear accelerator REGAE (Relativistic Electron Gun for Atomic Exploration) at DESY delivers electron bunches with a few femtosecond duration for time-resolved experiments of material structure in pump-probe configuration. To achieve the desired 10 fs resolution, the Low Level RF controls for the normal conducting S-band cavities must provide field stability of 0.01% in amplitude and of 0.01deg in phase. To achieve these demanding stability a recently developed LLRF controller based on the Micro-Telecommunications Computing Architecture (MTCA.4) have been installed and commission. In this paper, we report on measurement performance of the LLRF system, the achieved stability and current limitations.  
WEPME009 Recent Developments of the European XFEL LLRF System 2941
  • Ch. Schmidt, G. Ayvazyan, V. Ayvazyan, J. Branlard, Ł. Butkowski, M.K. Grecki, M. Hoffmann, T. Jeżyński, F. Ludwig, U. Mavrič, S. Pfeiffer, H. Schlarb, H.C. Weddig, B.Y. Yang
    DESY, Hamburg, Germany
  • P. Barmuta, S. Bou Habib, K. Czuba, M. Grzegrzółka, E. Janas, J. Piekarski, I. Rutkowski, D. Sikora, Ł. Zembala, M. Żukociński
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  • W. Cichalewski, K. Gnidzińska, W. Jałmużna, D.R. Makowski, A. Mielczarek, A. Napieralski, P. Perek, A. Piotrowski, T. Pożniak, K.P. Przygoda
    TUL-DMCS, Łódź, Poland
  • S. Korolczuk, I.M. Kudla, J. Szewiński
    NCBJ, Świerk/Otwock, Poland
  • K. Oliwa, W. Wierba
    IFJ-PAN, Kraków, Poland
  The European XFEL is comprised of more than 800 TESLA-type super-conducting accelerator cavities which are driven by 25 high-power multi-beam klystrons. For reliable, reproducible and maintainable operation of linac, the LLRF system will process more than 3000 RF channels. Beside the large number of RF channels to be processed, stable FEL operation demands field stability better than 0.010deg in phase and 0.01% in amplitude. To cope with these challenges the LLRF system is developed on MTCA.4 platform. In this paper, we will give an update of the latest electronics developments, advances in the feedback controller algorithm and measurement results at FLASH.  
WEPME035 Overview of the RF Synchronization System for the European XFEL 3001
  • K. Czuba, D. Sikora, Ł. Zembala
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  • J. Branlard, F. Ludwig, H. Schlarb, H.C. Weddig
    DESY, Hamburg, Germany
  One of the most important requirements for the European XFEL RF system is to assure a very precise RF field stability within the accelerating cavities. The required amplitude and phase stability equals respectively dA/A <3·10-5, dphi<0.01 deg @ 1.3GHz in the injector and dA/A<10-3, dphi <0.1 deg @1.3GHz in the main LINAC section. Fulfilling such requirements for the 3.4 km long facility is a very challenging task. Thousands of electronic and RF devices must be precisely phase synchronized by means of harmonic RF signals. We describe the proposed architecture of the RF Master Oscillator and the Phase Reference Distribution System designed to assure high precision and reliability. A system of RF cable based interferometers supported by femtosecond-stable optical links will be used to distribute RF reference signals with required short and long term phase stability. We also present test results of prototype devices performed to validate our concept.  
THPEA030 Improved Vector Modulator Card for MTCA-based LLRF Control System for Linear Accelerators 3207
  • I. Rutkowski, K. Czuba, M. Grzegrzólka
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  • D.R. Makowski, A. Mielczarek, P. Perek
    TUL-DMCS, Łódź, Poland
  • H. Schlarb
    DESY, Hamburg, Germany
  Modern linear accelerators require high-precision RF field regulation of accelerating cavities. A critical component to achieve high-precision in the feedback loop a Low Level Radio Frequency (LLRF) controller is the vector modulator driving the high power RF chain. At FLASH, the Free Electron Laser in Hamburg and European XFEL the LLRF controls are based on MTCA.4 platform. This paper describes the concept, design and performance of an improved vector modulator module (DRTM-VM2). It is constructed as Rear Transition Module (RTM). The module consists of digital, analog, diagnostic and management subsystems. FPGA from Xilinx Spartan 6 family receives data from control module (AMC) using Multi-Gigabit Transceivers (MGTs). The FPGA controls the analog part which includes fast, high-precision DACs, I/Q modulator chips, programmable attenuators, power amplifier and fast RF gates for external interlock system. Pin assignment on the Zone3 connector is compliant with digital class D1.2 recommendations proposed by DESY. The design has been optimized for mass production and for easy extends to wider frequency range. Electronic switches offer software configuration of power and clock sources.  
THPEA031 REGAE LLRF Control System Overview 3210
  • I. Rutkowski, Ł. Butkowski
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  • M. Hoffmann, H. Schlarb, Ch. Schmidt
    DESY, Hamburg, Germany
  The linear accelerator REGAE (Relativistic Electron Gun for Atomic Exploration) at DESY delivers electron bunches with a few femtosecond duration for time-resolved investigation of material structures in pump-probe configuration. To achieve sub-10fs resolution, the Low Level RF controls for the normal conducting S-band cavities must provide field stability of .005% in amplitude and of .005deg in phase. To achieve these demands, the recently developed LLRF control modules based on the Micro-Telecommunications Computing Architecture (MTCA.4) platform are used. For precise field detection and control a rear transition module (DRTM-DWC8VM1) housing 8 down-converters and 1 vector-modulator has been developed. The down-converted signals are transmitted to low-noise ADCs on an advanced mezzanine card (SIS8300L) with two high speed DACs driving the vector-modulator. The on board FPGA device runs the advanced control algorithms with minimum latency. Shot-to-shot learning feed forward and ultra-fast analog and digital feedbacks are applied. In this paper, the first results of the new RTM-AMC module pairs are presented together with the achievements and limitations on the RF field stability.  
THPWA003 Novel Crate Standard MTCA.4 for Industry and Research 3633
  • T. Walter, F. Ludwig, K. Rehlich, H. Schlarb
    DESY, Hamburg, Germany
  Funding: This project is funded by the Helmholtz Association (Helmholtz Validation Fund HVF-0016).
MTCA.4 is a novel electronic standard derived from the Telecommunication Computing Architecture (TCA) and championed by the xTCA for physics group, a network of physics research institutes and electronics manufacturers. MTCA.4 was released as an official standard by the PCI Industrial Manufacturers Group (PICMG) in 2011. Although the standard is originally physics-driven, it holds promise for applications in many other fields with equally challenging requirements. With substantial funding from the Helmholtz Association for a two-year validation project, DESY currently develops novel, fully MTCA.4-compliant components to lower the barriers to adoption in a wide range of industrial and research use scenarios. Core activities of the project are: refinement, test and qualification of existing components; market research, market education (web information services, workshops); coordinated development of missing MTCA.4 components; further advancement of the standard beyond the current PICMG specification; investigation of measures to counteract electro-magnetic interferences and incompatibilities; training, support and consultancy. This paper summarizes intermediate results and lessons learned at project half-time.