Mode selectivity in multiple-beam klystrons

A general method is developed for calculating the coupling coefficients of multiple beamlets of an arbitrary geometry to resonator fields having an arbitrary transverse distribution. A number of examples illustrate the effectiveness of this method for calculating coupling coefficients and show the effect of device parameters on the coupling of a given multiple electron beam to competing modes of multiple-beam klystrons (MBKs) operating in high-order modes. The method can be used for evaluating the mode selectivity and the “monotron instability” in MBKs. It can also be used for determining the Pierce gain parameter in multiple-beam traveling-wave tubes.