WEB —  Electron Diagnostics, Timing, Controls   (23-Aug-17   10:30—12:00)
Chair: H.-S. Kang, PAL, Pohang, Kyungbuk, Republic of Korea
Paper Title Page
Characterization of High-Brightness Electron Beams at the Frontiers of Temporal and Spatial Resolution  
  • R. Tarkeshian, T. Feurer, M. Hayati, Z. Ollmann
    Universität Bern, Institute of Applied Physics, Bern, Switzerland
  • T. Garvey, R. Ischebeck, E. Prat, S. Reiche, V. Schlott
    PSI, Villigen PSI, Switzerland
  • P. Krejcik
    SLAC, Menlo Park, California, USA
  • W. Leemans, R. Lehé, S. Steinke
    LBNL, Berkeley, California, USA
  We present two novel diagnostics to characterize high-brightness electron beams. The first technique, based on the tunnel ionization of a neutral gas by the intense (GV/m) self-field of the electron beam, can be used to measure the volumetric charge density of the beam, for example to reconstruct pulse durations shorter than few femtoseconds or to measure transverse beam sizes below the micron level. Experiments with sub-femtosecond unipolar self-field of electron beam, that approach the through-the-barrier tunneling times, could further deepen our understanding of quantum tunneling process. The second method can be used to streak electron beams with single cycle THz radiation concentrated in a micrometer gap of a resonant antenna, creating an enhanced electric near-field distribution. With this diagnostic one can measure with sub-femtosecond resolution the longitudinal duration, the slice emittance and energy spread of beams with energies up to tens of MeV. We show the validity of both methods with analytical calculations and particle-in-cell code simulations. We finally present practical implementation of both diagnostics at LCLS, in the XLEAP* experiment, and BELLA.
* X-Ray Laser Enhanced Altosecond Pulse Generation (XLEAP) For LCLS.
Characterization of Electron Bunches in Ultrafast Electron Diffraction Beamlines at KAERI  
  • H.W. Kim, I.H. Baek, K.H. Jang, Y.U. Jeong, K. Lee, J.H. Nam, N.A. Vinokurov
    University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
  • I.H. Baek, B.A. Gudkov, B. Han, K.H. Jang, Y.U. Jeong, H.W. Kim, Y.-C. Kim, K. Lee, S.V. Miginsky, J.H. Nam, S. Park, S. Setiniyaz
    KAERI, Daejon, Republic of Korea
  • R. Fabian, H. Ihee, J. Kim, K.Y. Oang, H. Yang
    KAIST, Daejeon, Republic of Korea
  • K.W. Kim
    Chung Buk National University, Cheongju, Republic of Korea
  • S.V. Miginsky, N.A. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
  Ultrashort electron bunches from ultrafast electron diffraction (UED) beamlines at the Korea Atomic Energy Research Institute (KAERI) has been characterized for sub-100-femtosecond-accuracy time-resolved diffraction experiments. The UED beamlines are designed to deliver electron bunches of 30 fs (rms) duration and 10 fs (rms) timing fluctuation with pumping laser pulses. We have two UED beamlines for solid and gas-phase samples. The energy of the electron beam is ~3 MeV and the bunch charge is more than 1 pC. We measured single-shot and multi-shot electron diffraction patterns of single-crystalline-silicon and poly-crystalline-gold films to confirm the electron beam quality. The temporal characteristics of the electron bunches are investigated by using laser-induced ponderomotive deflecting and spectral decoding of coherent transition radiation from the electron bunch by pumping IR pulse.  
WEB03 R&D at SLAC on Nanosecond-Range Multi-MW Systems for Advanced FEL Facilities 1
  • A.K. Krasnykh, A.L. Benwell, T.G. Beukers, D.F. Ratner
    SLAC, Menlo Park, California, USA
  Funding: Work supported by US Department of Energy contract DE-AC02-76SF00515
A nanosecond-range, multi-MW system containing TEM mode electrodynamic structures fed by controllable pulsers are needed for (1) fast injection systems in multi-bend achromat upgraded (MBA-U) storage rings and for (2) arrays of FEL beamlines powered by a superconducting linear accelerators operating with MHz-bunch repetition rate. The R&D effort covers both type (1) and (2) layouts. This report discuss the experimental results of several concepts for a generation of the nanosecond range multi MW pulsers. Compression of the initially formed electromagnetic (EM) power is employed for a generation of the nanosecond pulses in all concepts discussed here. A solid-state nonlinear media assists the EM compression. Features of the materials and components used in the design will be presented. The results will be included in the design of the kicker systems for advanced FEL facilities. For example, in the LCLS-II, the nanosecond range pulse allows for distributing closely spaced bunches to multiple undulators allowing experimenters to take advantage of combining different colored x-rays.
slides icon Slides WEB03 [1.864 MB]  
WEB04 Laser-to-RF Synchronization with Femtosecond Precision 1
  • T. Lamb, Ł. Butkowski, E.P. Felber, M. Felber, M. Fenner, S. Jabłoński, T. Kozak, J.M. Müller, P. Prędki, H. Schlarb, C. Sydlo, M. Titberidze, F. Zummack
    DESY, Hamburg, Germany
  Optical synchronization systems are already in regular operation in many FELs, or they will eventually be implemented in the future. In FLASH and the European XFEL, phase-stable optical reference signals are provided by a pulsed optical synchronization system in order to achieve low timing jitter FEL performance. The generation of phase-stable RF signals from a pulsed optical synchronization system is still a field of active research. The optical reference module (REFM-OPT), designed at DESY for operation in both FELs, employs a laser-to-RF phase detector, based on an integrated Mach-Zehnder interferometer. The phase drift of the 1.3 GHz RF reference signals with respect to the optical pulses is measured and actively corrected within the REFM-OPT at multiple locations in the accelerator. Therefore the REFM-OPT provides phase stable 1.3 GHz RF reference signals at these locations. The short-term and long-term performance in the accelerator tunnel of the European XFEL is presented and carefully reviewed.  
slides icon Slides WEB04 [5.679 MB]  
ICS Diagnostic of FEL's Electron Beam Based on 6D Wigner Function Approach  
  • A. Malyzhenkov, N.A. Yampolsky
    LANL, Los Alamos, New Mexico, USA
  We report on the design of the Inverse Compton Scattering (ICS) based diagnostic system for the electron beam in the free electron laser. Novel 6D Wigner function ICS theory analytically relates the phase space of emitted radiation to the phase space of the electron beam at the interaction point. Based on this theory, we find signatures of the electron beam phase space features in the emitted ICS radiation. Then, we analyze which of these signatures can be measured in the existing experimental setups and compare reconstructed electron beam phase space features to simulation results from the beam tracking codes. Finally, we inverse the 6D Wigner function ICS theory to find the electron phase space distribution dependence on characteristics of emitted radiation and propose the design of the new diagnostic system to reconstruct desirable 2D projections of the 6D electron phase space.