Wakefield Excitation by a Sequence of Electron Bunches in a Rectangular Waveguide Lined with Dielectric Slabs

A rectangular dielectric‐lined metallic structure was studied that has an advantage over a cylindrical structure from the possibility of exciting by a sequence of bunches many equally‐spaced modes, thereby building up a larger mode‐locked wakefield. A rectangular vacuum copper waveguide was lined with two dielectric slabs, the size of which was calculated to provide resonant excitation of the fundamental LSM mode by a sequence of bunches with repetition frequency f0=2805 MHz, produced by linear resonant electron accelerator (4.5 MeV, number of bunches 6.103, diameter 1cm, duration 60 ps each, distance between bunches 300 ps, number of electrons in each bunch 109). The waveguide has cross section 85 mm × 180 mm, and Teflon (e = 2.1) plates were placed along the smaller sides of the waveguide, their thickness from the calculation being 22 mm. In experiments, the length of the resonator was 535mm. We found that the total wakefield is three times larger than the fundamental mode; thus a greater number of exci...