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
TU Darmstadt, Darmstadt
Funding: This work was supported by DFG through SFB 634.
Based on the moment approach a fast tracking code named V-Code has been implemented at TEMF. Instead of using the particle distribution itself this method applies a discrete set of moments of the particle distribution. The time evolution of each moment can be deduced from the Vlasov equation when all essential external forces are known. These forces are given by the Lorentz equation in combination with the distribution of electric and magnetic fields. For efficiency reasons the 3D fields in the vicinity of the bunch trajectory are reconstructed in V-Code from one-dimensional field components by means of proper multipole expansions for the individual beam line elements. The entire beam line is represented in the code as a successive alignment of separate independent beam line elements. The proximity of some beam forming elements may lead to overlapping fringe fields between consecutive elements. In order to simulate even such beam lines with the V-Code, its database of disjunctive beam line elements has to be enhanced to deal also with superposed fields. In this paper a summary of issues regarding the implementation complemented with simulation results will be provided.