Author: Noelle, D.     [Nölle, D.]
Paper Title Page
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.
WEPC21 Design and Beam Test Results of Button BPMs for the European XFEL 723
  • D.M. Treyer, R. Baldinger, R. Ditter, B. Keil, W. Koprek, G. Marinkovic, M. Roggli
    PSI, Villigen PSI, Switzerland
  • D. Lipka, D. Nölle, S. Vilcins
    DESY, Hamburg, Germany
  Funding: Swiss State Secretariat for Education, Research and Innovation
The European X-ray Free Electron Laser (E-XFEL) will use a total ~300 button BPMs along the whole accelerator, as well as 160 cavity BPMs. The pickups for the button BPMs have been designed by DESY, whereas the electronics has been developed by PSI. This paper gives an overview of the button BPM system, with focus on the RF front end electronics, signal processing, and overall system performance. Measurement results achieved with prototypes installed at FLASH/DESY and at the SwissFEL Injector Test Facility (SITF) are presented. The position noise obtained with button pickups in a 40.5 mm aperture beam pipe is as low as ~11 um at 20 pC bunch charge.
poster icon Poster WEPC21 [1.595 MB]  
WEPF03 Scintillating Screen Monitors for Transverse Electron Beam Profile Diagnostics at the European XFEL 807
  • Ch. Wiebers, M. Holz, G. Kube, D. Nölle, G. Priebe, H.-C. Schröder
    DESY, Hamburg, Germany
  Transverse beam profile diagnostics in modern electron linear accelerators like FELs or injector LINACs are mainly based on optical transition radiation (OTR) as standard technique which is observed in backward direction when a charged particle beam crosses the boundary between two media with different dielectric properties. The experience from modern LINAC based 4th generation light sources shows that OTR diagnostics might fail because of coherence effects in the OTR emission process. As a consequence, for the European XFEL which is currently under construction in Hamburg, transverse beam profile measurements are based on scintillating screen monitors. The LYSO:Ce screens are oriented such that coherent OTR generated at the screen boundaries will be geometrically suppressed. An additional advantage is that the imaging optics operate in Scheimpflug condition thus adjusting the plane of sharp focus with respect to the CCD chip and significantly increasing the apparent depth of field. This report gives an overview of the measuring principle and the monitor setup together with results of laboratory test measurements and a first prototype test at FLASH (DESY, Hamburg).  
Production of Cavity BPMs for the European XFEL  
  • D. Lipka, D. Nölle, S. Vilcins
    DESY, Hamburg, Germany
  The DESY colleagues gave a comprehensive presentation of the large-scale cavity BPM system required for the XFEL (DESY), with most details are self-explaining by the slides. The XFEL cavity BPM pickup is based on a design from T. Shintake (Spring-8), a compact setup of waveguide loaded dipole mode and reference cavities, both utilizing a “magnetic”(loop) waveguide-to-coaxial transition for the signals. Both XFEL cavity BPM variants, for the beamline and the undulator, are made of stainless steel, to ensure a low-Q of ~70 (3.3GHz operating frequency), ensuring single bunch detection (bunch spacing 222ns). Details on the performance and manufacturing of the N-type feedthrough were given, which is based on a design of Shintake. Dirk went through the entire production process of the cavity BPMs, starting from the first prototypes until the full production series, which included some surprises. This contribution was very comprehensive, and most questions were answered by the presentation. On the cross coupling between the planes, Dirk mentioned better than 40dB!  
slides icon Slides FRWMJ5 [1.025 MB]