• I.R.R. Shinton, R.M. Jones, N. Juntong
  UMAN, Manchester
• N. Baboi
  DESY, Hamburg
• N. Eddy, T.N. Khabiboulline
  Fermilab, Batavia
• T. Flisgen, H.-W. Glock, U. van Rienen
  Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock

We analyse the higher order modes in the 3.9GHz bunch shaping cavities recently installed in the XFEL/FLASH facility at DESY. We report on recent experimental results on the frequency spectrum, both beam and probe based. These are compared to those predicted by finite element computer codes, globalised scattering matrix calculations and a two-band circuit model. This study is focused on the dipole component of the multiband expansion of the wakefield.

• N. Juntong, R.M. Jones
  UMAN, Manchester

We present an optimized geometry for a 1.3 GHz superconducting cavity in which the surface electromagnetic fields have been minimized and the bandwidth of the fundamental mode has been maximized. We refer to this design as the New Low Surface Field (NLSF) cavity*. Earlier work* focused the fundamental mode properties. Here we study higher order modes (HOMs), means of damping them, and short range wakefields. A two-band circuit model is employed in order to facilitate rapid characteristic of the HOMs in the cavity.

* N. Juntong and R.M. Jones, High-Gradient SRF Cavity with Minimized Surface E.M. Fields and Superior Bandwidth for The ILC, SRF2009, THPPO024, 2009.