TEMF, TU Darmstadt, Darmstadt
DESY, Hamburg
The rf and wakefield transverse kicks resulting from the asymmetry of input and HOM couplers in the third harmonic module for the XFEL are investigated. The fundamental mode is computed using eigenvalue analysis. The short range wakefields in a string of cavities are simulated with the PBCI code. Using the simulation data, the transverse kick factors associated with the presence of cavity couplers are evaluated.
* P. Pierini, "Third Harmonic Superconducting Cavity Prototypes for the XFEL", LINAC08.
** T. Khabiboulline, "New HOM Coupler Design For 3.9 Ghz Superconducting Cavities At FNAL", PAC07.
TEMF, TU Darmstadt, Darmstadt
We report on a new numerical technique for the computation of geometrical wakes in three-dimensional LINAC structures. The method utilises an explicit Finite-Volume Time-Domain (FVTD) formulation. The numerical dispersion in all three axial directions is completely eliminated by choice of an appropriate staggering of the field components on the grid. Thus, contrary to most of the previously reported techniques no splitting of the time-evolution operator is necessary. This results in large savings in computational time as well as in an improved numerical accuracy. We have implemented this new technique in PBCI code and present some preliminary results.