Electron bunching and output gap interaction in broad-band klystrons

Broad-band klystron operation is investigated using a large-signal digital computer simulation of electron bunching and output gap interaction. Electron bunching is examined as a function of beam voltage and perveance for a prototype series of klystrons. The development of a low energy "spur" of electrons is shown to limit efficiency at high perveance, particularly at the high band edge. The output gap interaction is computed in a broad fashion so that klystron performance can be evaluated for a variety of cold output cavity impedances. Application is made to a practical commercial klystron. Measured klystron efficiency is shown to agree well with computed efficiency over most of the frequency band. The limitations of using the "merit figure" concept for efficiency are discussed.