Abstract :
An experimental 2-cavity klystron with a variable drift space has been constructed to investigate velocity-modulated electron beams. The operating frequency is 300 Mc/s. Previous experimental work with this valve has shown that the space-charge-wave theory accurately predicts both the optimum drift length and the output r.f. current, provided that small signals are used. Recent theoretical work on large-signal conditions has enabled some experimental results with large signals to be compared with calculations for similar, though not quite identical, conditions. Both the experiments and the theory show that the optimum drift length is considerably reduced when the input signal is large. The parameter that determines whether the signal is large is not merely the ratio of the modulating r.f. voltage to the beam accelerating voltage but is this quantity multiplied by the ratio of signal frequency to plasma frequency.
