A MODEL OF INJECTION-LOCKED RELATIVISTIC KLYSTRON OSCILLATOR

By the use of a simple model, we explicitly incorporate the coupling b etween the driver cavity and the booster cavity in a relativistic klys tron amplifier (RKA), We show that this RKA configuration may turn int o an injection-locked oscillator only when the beam current is suffici ently high. Other features revealed by this model include: the downshi fted frequency mode (''0'' mode) is unstable whereas the upshifted fre quency mode (''pi'' mode) is stable; the growth rate of the ''0'' mode is relatively mild so that the oscillation can start only in an injec tion-locked mode; the oscillation does not require the presence of ref lected electrons; and the separation of the cavities must be sufficien tly short, These, and other features, are found to be in qualitative a greement with the recent experiments on the injection-locked relativis tic klystron oscillator (RKO) that were conducted at Philips Laborator y.