Author: Glock, H.-W.
Paper Title Page
MOPO060 Higher Order Modes for Beam Diagnostics in Third Harmonic 3.9 GHz Accelerating Modules 239
 
  • N. Baboi, P. Zhang
    DESY, Hamburg, Germany
  • N. Eddy
    Fermilab, Batavia, USA
  • T. Flisgen, H.-W. Glock
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • R.M. Jones, I.R.R. Shinton
    UMAN, Manchester, United Kingdom
 
  Funding: This work is supported in part by the European Commission under the FP7 Research Infrastructures project EuCARD, grant agreement 227579.
An international team is currently investigating the best way to use Higher Order Modes (HOM) for beam diagnostics in 3.9 GHz cavities. HOMs are excited by charged particles when passing through an accelerating structure. Third harmonic cavities working at 3.9 GHz have been installed in FLASH to linearize the bunch energy profile. A proof-of-principle of using HOMs for beam monitoring has been made at FLASH in the TESLA 1.3 GHz cavities. Since the wakefields generated in the 3.9 GHz cavities are significantly larger, their impact on the beam should be carefully minimized. Therefore our target is to monitor HOMs and minimize them by aligning the beam on the cavity axis. The difficulty is that, in comparison to the 1.3 GHz cavities, the HOM-spectrum is dense, making it difficult to identify individual modes. Also, most modes propagate through the whole cryo-module containing several cavities, making it difficult to measure local beam properties. In this paper the options for the HOM-based beam position monitors are discussed.