ABSTRACT

To solve this problem, we have adapted a new coupling scheme proposed by Tantawi and Nantista [8] that uses a TE-TM mode converter as coupling structure. A similar technique was also studied by I. Syratchev for use in the CLIC accelerating structure [9]. Our new scheme is shown in Figure I. A transition section is used to convert the TE mode (from the rectangular WR90 feed waveguide) to a TM mode (in a cylindrical copper waveguide). A tapered dielectric section is then used to transmit Rf power into the dielectric accelerator section. This scheme separates the dielectric loaded accelerator from the coupling structure by a tapered section. Such scheme makes the coupler independent of the dielectric properties, and the highest fields are developed in the accelerator section. Because the coupler is implemented in a section of circular waveguide, the aperture of the coupling slot is much larger than in the old scheme [I] so that the peak value of the EM field at the coupling aperture is much smaller than that of the old scheme under the same input power.