Author: Gerth, C.
Paper Title Page
TUPP15
 DEOS: A New Scheme for Recording Electron Bunch Shapes With High Resolution and Record Recording Length - Principle and Tests at EuXFEL  
 
  • S. Bielawski
    PhLAM/CERCLA, Villeneuve d’Ascq Cedex, France
  • C. Evain, E. Roussel, C. Szwaj
    PhLAM/CERLA, Villeneuve d’Ascq, France
  • C. Gerth, B. Steffen
    DESY, Hamburg, Germany
  • B. Jalali
    UCLA, Los Angeles, California, USA
  
  Funding: CEMPI LABEX, CPER Photonics for society, ULTRASYNC ANR, METEOR CNRS MOMENTUM grant
Recording electron bunch longitudinal profiles in single-shot, and non-destructively is largely needed in accelerator operation. A common strategy consists in probing the near-field of the bunch using femtosecond laser pulses. These two last decades, such electro-optic detection schemes have evolved to compact and reliable techniques. However, serious limitations have been limiting the time-resolution, when long recording lengths are needed. This has been recognized as a fundamental bottleneck and even coined the term "Fourier limit". We present here a novel electro-optic sampling strategy that is theoretically capable to overcome this limit and achieve femtosecond resolution for any recording length. This new approach is based on the mathematical concept of information diversity. We present first results of DEOS (Diversity Electro-Optic Sampling) obtained both in table-top experiments, as well as at the European XFEL. This technique opens the way to electric field shape characterization with femtosecond resolution in new situations, including longitudinal bunch profile monitoring, studies of microbunching instabilities, and THz pulses generated at free-electron lasers.
https://arxiv.org/abs/2002.03782 		 
poster icon Poster TUPP15 [1.683 MB]  
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WEAO04
 Non-invasive Longitudinal Profile Measurements of Electron Bunches Simultaneously to FEL Operation at MHz Rates  
 
  • N.M. Lockmann, C. Gerth, B. Schmidt, S. Wesch
    DESY, Hamburg, Germany
  
  Hard X-ray FELs require ultra-short electron bunches with peak currents of several kiloamperes. Therefore, longitudinal bunch profile characterization with femtosecond resolution is essential for a successful operation and control of the accelerator as well as a wide field of photon experiments. The high electron beam energies of hard X-ray FELs enable non-invasive longitudinal form factor monitoring down to a few micrometers utilizing coherent diffraction radiation spectroscopy. For this purpose, a 4-staged grating spectrometer has been recently installed at European XFEL. Here, current profiles are reconstructed with femtosecond time resolution based on phase retrieval algorithms which are in excellent agreement to results obtained with a transverse deflecting structure. The fast pyroelectric detectors allow, for the first time, to measure the current profile of all bunches inside the bunch train with repetition rates of up to 2.2 MHz. The low latency electronic readout of the 120 channels of the spectrometer provides high potential for fast compression feedbacks and machine learning applications.  
slides icon Slides WEAO04 [1.358 MB]  
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