Planar accelerator structures for millimeter wavelengths

The fabrication of a muffin-tin planar accelerator structure for operation in the 90 GHz range have been discussed. Fabrication problems subsequently encountered led us to consider an alternative structure, a structure which can be thought of as a muffin-tin with the sides removed and replaced by a pair of side chambers which act as side terminations. With the side chambers removed, the structure when viewed from the side presents two periodic arrays of vanes facing one another from above and below the beam plane and which extend towards the beam plane from upper and lower plane metallic surfaces. The vane pairs are the analogs of the beam iris in cylindrical structures, and the space between the irises and terminated by the upper and lower plane metallic surfaces correspond to the cavities. Because the general appearance of this view is zipper like, we refer to the structure as the "zipper" structure. The side chambers are envisaged as extending with uniform cross section from the input to the output cavities.