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Steffen, B.

Paper Title Page
WEPPH047 Electro-Optic Spectral Decoding for Single-Shot Characterisation of the Coherent Transition Radiation Time Structure at FLASH 453
 
  • E.-A. Knabbe, B. Schmidt, P. Schmüser, B. Steffen, V. R. Arsov
    DESY, Hamburg
 
  Characterisation of the longitudinal profiles of ultrashort electron bunches is of primary importance for controlling the lasing process of SASE FEL. Non-destructive, single-shot techniques, are preferable. Presently the most promising ones are the Electro-Оptic (EO) laser diagnostics and the THz spectroscopy of coherent transition radiation (CTR). Whereas the former are applied directly in the electron beam line, the latter offer possibility to detect shorter temporal structures, but outside the tunnel. Therefore it is important to know the transfer function of the CTR beam line. We present a single-shot EO detection of temporal CTR profiles, generated from electron bunches, kicked to an off-axis screen at DESY's VUV-FEL (FLASH). The THz radiation is transported through a 20 m long line from the accelerator tunnel to an experimental station outside. The measurements are performed in air and in vacuum with 0.5 mm ZnTe and 0.175 mm GaP crystals in crossed-polarisers detection scheme. Pulses with less than 1 ps FWHM have been measured.  
WEBAU04 Single-Shot Longitudinal Bunch Profile Measurements at FLASH Using Electro-Optic Detection: Experiment, Simulation, and Validation 310
 
  • V. R. Arsov, E.-A. Knabbe, B. Schmidt, P. Schmüser, B. Steffen
    DESY, Hamburg
  • G. Berden, A. F.G. van der Meer
    FOM Rijnhuizen, Nieuwegein
  • W. A. Gillespie, P. J. Phillips
    University of Dundee, Nethergate, Dundee, Scotland
  • S. P. Jamison
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • A. MacLeod
    UAD, Dundee
 
  At the superconducting linac of FLASH at DESY, we have installed an electro-optic experiment for single shot, non-destructive measurements of the longitudinal electric charge distribution of individual electron bunches. The profile of the electric bunch field is electro-optically encoded onto a stretched Ti:Sa laser pulse. In the decoding step, the profile is retrieved from a cross-correlation of the encoded pulse with a 35 fs laser pulse, obtained from the same laser. At FLASH, sub-100 fs electron bunches have been measured during FEL operation with a resolution of better than 50 fs. The electro-optic encoding process in gallium phosphide as well as the decoding step in a frequency doubling BBO crystal were numerically simulated using bunch shapes simultaneously measured with a transverse-deflecting rf structure as input data. In this contribution, we present electro-optically measured profiles and compare them with the simulation.  
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