Simulations of stretched wire measurements of 3.9GHZ cavities for the ILC

We present simulations on the transverse modes in crab cavities required in the beam delivery system of the ILC to maximise the luminosity of the beam. We utilize both finite difference and finite element computer codes to simulate the electromagnetic fields in these cavities in the presence of a stretched wire. This study is intended to both predict the wake-field in experiments on the modal characterisation of 3.9 GHz cavities in progress at the Cockcroft Institute. A scattering matrix approach is used on multi-cell cavities and compared with experimental data. Results are presented on the modes in crab cavity structures subjected to infinitely periodic boundary conditions.