Measurements on iris-structures with rectangular holes

By replacing the irises in an electron linac with rectangular slots a structure is obtained which is capable of focusing/defocusing an electron beam. Therefore, this kind of iris-geometry could be employed alone or in combination with conventional magnetic quadrupoles for transversal focusing in future linear colliders. A three-cell structure with rectangular irises was designed and tuned to nu /sub ph/=c at TM/sub 010/ 2 pi /3 mode. Perturbation measurements were performed in order to determine the fields and focusing strength of the structure.<>