Abstract: A method for suppressing second and higher harmonic power generation in a klystron is described. The klystron includes a series of cavities that are connected to a series of connecting drift tubes, and one or more waveguide loads are placed on selected ones of the drift tubes or cavities, for reducing the second and higher harmonic power by causing it to be loaded out progressively, at predetermined discrete intervals. In the preferred embodiment, the inner diameter of the drift tubes is such that the cutoff frequency is above the fundamental operating frequency of the klystron, which will allow frequencies greater than the fundamental frequency, and particularly the second harmonic frequency, for example 22.848 GHz, to propagate. In one example, each of the four pre-selected drift tubes is loaded with two generally diametrically oppositely positioned waveguide loads. In another example, each of four drift tubes is loaded with three equidistally positioned waveguide loads.

Abstract: A waveguide window contains a central transverse pane of a material with high dielectric constant such as alumina ceramic. The central pane is an integral number of half-wavelengths thick. On each side of the central pane and immediately adjacent it is a side pane of material with relatively low dielectric constant such as fused quartz. The side panes are odd numbers of quarter-wavelengths thick. The dielectric constants of the side panes are preferably the square root of the dielectric constant of the central pane. The improved wave impedance matching provides a low wave reflection over a wide frequency band.