Computation of wakefields in structures containing dispersive materials

Ferrite has a variety of applications in accelerator components, and the capability to model this magnetic material in the time domain is an important adjunct to currently available accelerator modeling tools. In this paper is described a general dispersive material model which is suitable for a wide variety of media, including ferrite. Based on this model we have developed a representation of the time-domain magnetic properties of PE11BL, the ferrite used in the induction modules of the ETA-II (Experimental Test Accelerator -II) induction linac at LLNL. This material is characteristic of the soft ferrites commonly used in induction accelerators. The model has been implemented in 1-D and 2-D finite-difference time-domain (FDTD) electromagnetic simulators, and comparisons with analytic and experimental results are presented. (Author) tab., 6 figs., 11 refs