MOCLA —  Time Resolved Diagnostics and Synchronization   (14-Sep-15   14:00—15:30)
Chair: S.R. Smith, SLAC, Menlo Park, California, USA
Paper Title Page
MOCLA01 Microbunching Instability in Relativistic Electron Bunches: Direct Observations of the Microstructures Using Ultrafast YBCO Detectors 1
  • E. Roussel, S. Bielawski, C. Evain, C. Szwaj
    PhLAM/CERLA, Villeneuve d'Ascq, France
  • M. Adachi, M. Katoh, S.I. Kimura, T. Konomi
    UVSOR, Okazaki, Japan
  • M. Hofherr, K.S. Ilin, J. Raasch, A. Scheuring, M. Siegel, P. Thoma, S. Wuensch
    KIT, Karlsruhe, Germany
  • M. Hosaka, Y. Takashima, N. Yamamoto
    Nagoya University, Nagoya, Japan
  • H. Zen
    Kyoto University, Kyoto, Japan
  Relativistic electron bunches circulating in accelerators are subjected to a dynamical instability leading to microstructures at millimeter to centimeter scale. Although this is a well-known fact, direct experimental observations of the structures, or the field that they emit, remained up to now an open problem. Here, we report the direct, shot-by-shot, time-resolved recording of the shapes (including envelope and carrier) of the pulses of coherent synchrotron radiation that are emitted, and that are a 'signature' of the electron bunch microstructure. The experiments are performed on the UVSOR-III storage ring, using electrical field sensitive YBa2Cu3O7−x thin-film ultrafast detectors. The observed patterns are subjected to permanent drifts, that can be explained from a reasoning in phase space, using macroparticle simulations.
slides icon Slides MOCLA01 [37.740 MB]  
MOCLA02 Design of a Compact L-band Transverse Deflecting Cavity with Arbitrary Polarisations for the SACLA Injector 1
  • H. Maesaka, T. Asaka, T. Ohshima, Y. Otake, H. Tanaka
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • S. Matsubara
    JASRI/SPring-8, Hyogo, Japan
  We are planning to install a transverse deflecting cavity (TCAV) in the injector of the X-ray free electron laser (XFEL) facility, SACLA [*], in order to measure longitudinal bunch profiles after a velocity bunching process. This is because the longitudinal bunch profile in the injector is critically important for reproducing the XFEL performance [**]. The TCAV will be installed at the end of the velocity bunching section, where the bunch length ranges from 10 ps to several 100 ps, the kinetic energy of the beam is approximately 1 MeV, and the transverse beam motion is rotated by solenoid lenses. Considering these conditions, we designed a compact L-band (1428 MHz) TM110-mode pillbox-shape TCAV (~300 mm-diameter and ~100 mm-long) with two input ports intersecting at a right angle. One of the advantages of this TCAV is that the polarisation of a deflecting rf field can be freely chosen, e.g. linear or circular, by changing the amplitude and phase at each rf port. We can select the linear polarisation for linear streaking with an arbitrary direction, or the circular one for axially symmetric deflection to reduce transverse mixing due to a solenoid B-field, depending on the situation.
[*] T. Ishikawa, et al., Nature Photonics 6, 540-544 (2012).
[**] T. Asaka, et al., Proceedings of LINAC2012, 486-488, TUPB006, (2012).
slides icon Slides MOCLA02 [11.991 MB]  
Fully Intensity and Timing Jitter Compensated Ultra-Fast Experiments at Accelerator-Driven Photonsources at High Repetition Rates  
  • S. Kovalev, M. Gensch, B.W. Green
    HZDR, Dresden, Germany
  • A.S. Fisher
    SLAC, Menlo Park, California, USA
  • T. Golz, N. Stojanovic
    DESY, Hamburg, Germany
  • T. Kampfrath
    FHI, Berlin, Germany
  Funding: European Union through project EUCALL
Timing jitter and power instabilities are crucial parameters which greatly reduce the applicability of accelerator driven light sources for time-resolved experiments. In this contribution we present a technique that allows achieving few 10 fs time-resolution in experiments operating at cw repetition rates of up to 100 kHz by employing high repetition rate data acquisition. The method employs a fs-level arrival time monitor based on electro-optic sampling* ** of residual pulses from a coherent diffraction radiator and a fast THz detector allowing for pulse to pulse detection of arrival time and pump intensity. The monitor can operate at high repetition rates cw (presently up to a few 100 kHz) and low electron bunch charges (sub pC). The prototype device has been tested at the quasi CW SRF accelerator (ELBE) by performing an ultra-fast THz driven magnetization dynamics experiment***. Our method has high potential to provide few fs level timing on next generation large scale X-ray photon sources based on high repetition rate electron accelerators such as LCLSII. A demonstrator aiming at operation up to 4.7 MHz is under development for the European X-FEL.
* Z. Jiang, X. C. Zhang, IEEE Journal of Quantum Electronics, 36, 1214, 2000
** I. Wilke et al., Phys. Rev. Lett., 88, 124801, 2002.
*** S. Kovalev et. al., under review (2015).