Flat-field Planar Structures Designed for Small and Large Aspect Ratios*

* This work is supported by DOE SBIR No. DE-FG03-96ER82213. Abstract We consider novel designs that provide field flatness of fundamental mode in transverse dimensions of planar rf structures. These designs include waveguides with slotted irises and/or dielectric loaded side openings. The specially modified, advanced planar structures can be produced with available technology for a number of purposes. Highaspect ratio structures are suitable for mm-wave generation in sheet-beam klystrons (SBK) and for industrial, medical and research linacs. Small aspect-ratio planar structures having “flat” impedance in central area may be applicable to linear colliders. Impedance flatness better than 1/1,000 over half of aperture cross-section is demonstrated in simulations done for sample structures.