Author: Delsim-Hashemi, H.
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MOPRI027 Dark Current Studies at Relativistic Electron Gun for Atomic Exploration – REGAE 649
 
  • H. Delsim-Hashemi, K. Flöttmann
    DESY, Hamburg, Germany
 
  Electron diffraction is a tool for exploring structural dynamics of matter. The scattering cross section is orders of magnitude higher for electrons than for X-rays so that only a small number of electrons is required to achieve comparable results. However, the required electron beam quality is extraordinary. To study e. g. proteins a coherence length of 30 nm is required which translates into a transverse emittance of 5 nm at a spot size of 0.4mm. In addition short bunch lengths down to 10 fs and a temporal stability of the same order are required in order to study chemical reactions or phase transitions in pump probe type experiments. These are challenging parameters for an electron source, which demand improvements at many frontiers. Dark current degrades contrast of diffraction patterns in all experiments. Understanding dark-current generation and propagation can lead to better methods to decrease it. In this paper dark current studies that are performed at REGAE will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI027  
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THPME119 Transverse emittance measurement at REGAE 3515
 
  • S. Bayesteh
    Uni HH, Hamburg, Germany
  • H. Delsim-Hashemi, K. Flöttmann
    DESY, Hamburg, Germany
 
  A new linac, named REGAE (Relativistic Electron Gun for Atomic Exploration) has been built at DESY and operates as an electron source for ultra-fast electron diffraction. An RF photocathode gun provides electron bunches of high coherence, sub-pC charge and energies of 2-5 MeV. In order to film time-resolved structural changes of excited specimens, bunch lengths of several femtoseconds need to be created. Taking into account these critical parameters, beam diagnostics at REGAE is very challenging. The existing diagnostics consists of energy, energy spread, beam profile, beam charge and emittance measurements. For transversal diagnostics, specific approaches have to be considered to overcome complications associated with the low charge and to carry out the beam diagnostics in single shot. In this paper, the contribution of the transversal diagnostics to the measurement of the transverse emittance is presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME119  
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THPRI033 Design of New Buncher Cavity for Relativistic Electron Gun for Atomic Exploration – REGAE 3840
 
  • M. Fakhari, H. Delsim-Hashemi, K. Flöttmann, M. Hüning, S. Pfeiffer, H. Schlarb
    DESY, Hamburg, Germany
  • J. Roßbach
    Uni HH, Hamburg, Germany
 
  The Relativistic Electron Gun for Atomic Exploration, REGAE, is a small electron accelerator build and operated at DESY. Its main application is to provide high quality electron bunches for time resolved diffraction experiments. The RF system of REGAE contains different parts such as low level RF, preamplifier, modulator, phase shifter, and cavities. A photocathode gun cavity to produce the electrons and a buncher cavity to compress the electron bunches in the following drift tube. Since the difference between the operating mode of the existing buncher and its adjacent mode is too small, the input power excites the other modes in addition to the operating mode which affects the beam parameters. A new buncher cavity is designed in order to improve the mode separation. Furthermore the whole cavity is modeled by a circuit which can be useful especially during the tuning process. Beam dynamics simulations have been performed in order to compare the new designed cavity with the old one which declare that the effects of the adjacent modes on the beam parameters are decreased.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI033  
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