Three-Dimensional Wake Field Computations Based on Scattered-Field Time Domain Boundary Element Method

We present time domain 3-D wake field calculations based on Scattered-field Time Domain Boundary Element Method (S-TDBEM), which is retarded Kirchhoff's boundary integral equations of scattered electromagnetic fields formulated on interior region problem and has no numerical dispersion in all spatial direction. We propose two main types of S-TDBEM schemes: full 3-D scheme for general 3-D geometries and a so-called 2.5-D scheme for transverse wake field calculation in axis-symmetric structures. Several numerical examples are demonstrated for typical accelerator structures: elliptical pillbox and the TESLA 9-cell cavities. The developed 3-D/2.5-D S-TDBEM codes are verified by comparison with the modal analysis and the finite integration technique (FIT) in the numerical examples. Finally, as one of the most meaningful applications of the S-TDBEM, we demonstrate wake field simulations of a curved trajectory bunch with the developed 3-D S-TDBEM code.