Author: Rutkowski, I.
Paper Title Page
MOPGF093 Real-time Beam Loading Compensation for Single SRF Cavity LLRF Regulation 1
  • I. Rutkowski, M. Grzegrzólka
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  • Ł. Butkowski, Ch. Schmidt
    DESY, Hamburg, Germany
  • M. Kuntzsch
    HZDR, Dresden, Germany
  Stable and reproducible generation of a photon beam at Free Electron Lasers (FELs) necessitates a low energy spread of the electron beam. A low level radio frequency (LLRF) control system stabilizes the RF field inside accelerating modules. An electron beam passing through the cavity induces a drop in the actual stored field proportional to the charge, the cavity shunt impedance, and the bunch repetition rate. The feedback loop compensates for the perturbation after the accelerating gradient drops. Due to the digital loop delay and limited bandwidth of the closed loop system, this disturbance induces control errors which can increase beam energy spread. An open-loop controller uses information obtained from the beam diagnostic systems accounting in real-time for fluctuations of the beam current. This paper describes the bunch charge detection scheme, its implementation, as well as results of the tests performed on the ELBE (Electron Linac for beams with high Brilliance and low Emittance) radiation source at the HZDR (Helmholtz-Zentrum Dresden-Rossendorf) facility.  
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