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Dohlus, M.

Paper Title Page
TPAT006 Impact of Optics on CSR-Related Emittance Growth in Bunch Compressor Chicanes 1015
 
  • T. Limberg, M. Dohlus
    DESY, Hamburg
  
  The dependence of emittance growth due to Coherent Synchrotron Radiation (CSR) in bunch compressor chicanes on optics has been noticed and empirically studied in the past. We revisit the subject, suggesting a model to explain slice emittance growth dependence on chicane optics. A simplified model to calculate projected emittance growth when it is mainly caused by transverse slice centroid offsets is presented. It is then used to find optimal compensation of centroid kicks in the single chicanes of a two-stage compression system by adjusting the phase advance of the transport in between and the ration of the compression factors.  
WPAT083 Steering and Focusing Effects in TESLA Cavity Due to High Order Mode and Input Couplers 4135
 
  • P. Piot
    Fermilab, Batavia, Illinois
  • M. Dohlus, K. Floettmann, M. Marx, S.G. Wipf
    DESY, Hamburg
  
  Funding: This work was supported by Universities Research Association Inc. under contract DE-AC02-76CH00300 with the U.S. Department of Energy, and by NICADD.

Many state-of-art electron accelerator proposals incorporate TESLA-type superconducting standing wave cavities. These cavities include input coupler (to feed the RF power into the cavity) and a pairs of high order mode couplers (HOM) to absorb the energy associated to HOM field excited as the bunch passes through the cavity. In the present paper we investigate, using numerical simulations, the impact of the input and HOM couplers on the beam dynamics. We show the overall effects are: a dipole kick (zeroth order) and normal and skew quadrupole-type focusing (first order). We present parametric studies of the strength of these effect for various operating gradients and incoming beam energies. We finally study the impact of this non-asymmetric field on the beam dynamics, taking as an example the low energy section of the European X-FEL injector.

 
RPPT011 Optimized Bunch Compression System for the European XFEL 1236
 
  • T. Limberg, V. Balandin, R. Brinkmann, W. Decking, M. Dohlus, K. Floettmann, N. Golubeva, Y. Kim, E. Schneidmiller
    DESY, Hamburg
  
  The European XFEL bunch compressor system has been optimized for greater flexibility in parameter space. Operation beyond the XFEL design parameters is discussed in two directions: achieving the uppermost number of photons in a single pulse on one hand and reaching the necessary peak current for lasing with a pulse as short as possible on the other. Results of start-to-end calculations including 3D-CSR effects, space charge forces and the impact on wake fields demonstrate the potential of the XFEL for further improvement or, respectively, its safety margin for operation at design values.