Evaluation of wake fields of disk loaded structure for Japan Linear Collider

The numerical estimation of the long range wake fields of the accelerating structure for JLC was carried out by using various computer codes; TBCI, KN7C, TRANSVRS, and URMEL. It provides the basis of the argument on the energy distribution or the emittance growth of a multi-bunched beam. A large portion of the transverse wake field was found to be occupied by a dominant mode, lowest in frequency, while the contribution of the other modes were found at most twenty percent. On the wake field of the dominant mode, the estimation of the amount calculated by the above codes agreed within ten percent. The dependence of the wake fields on a geometric variation, i.e. an aperture, was also investigated. (author)