Wake Fields Analysis of Curved Tube Section of Particle Accelerator by Time-Domain BEM Considering Lienard-Wiechert Fields of Electron Bunch

Electron beam dynamics in bunch compressor section of X-ray FEL and Linear Collider is very sensitive for various external disturbances, and should be carefully considered in the machine design. One of difficulties in the design of bunch compressor is exact evaluation of effects of wake fields on the beam motion at curved section of accelerator tube. In particular, it is not easy to simulate wake fields and evaluate influences on the beam dynamics at slightly curved beam tube section by using standard FDTD scheme due to its grid discretization. Authors have been working in development of time-domain boundary element method (TDBEM) to simulate the wake fields in the slightly curved beam tube section, and it was shown that the wake fields can be evaluated appropriately even for very small signal of rotating component of surface current on the beam tube by the TDBEM <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]–[3]</sup>. Then, original bunch self-fields, which induce the wake field inside the beam tube, were approximated by static electromagnetic fields in the conventional TDBEM analysis. In this work, we evaluate the bunch self-fields strictly by using the following Lienard-Wiechert fields