A two-cavity extended interaction klystron yielding 65 per cent efficiency

Results of experiments with a two-cavity extended interaction klystron are given. The tube is nominally capable of 1 kw-CW at
S
band and consists of two five-gap short-slot-coupled cavities coupled to the input and output lines by means of TWT matching sections with adjustable mismatches. The unusual features of the tube are 1) the length of extension of the resonant cavities (five electron ballistic wavelengths) and 2) the incorporation of different and controllable beam-circuit synchronism conditions for the input and output cavities. The results of principal interest are the low velocity spread in the spent beam entering the collector providing high total conversion efficiency (65 per cent) with collector depression and stable gain in excess of 15 db. Some treatment of the relationship of efficiency and oscillation stability is included, as well as comments on the usefulness of such a design for high power millimeter wave amplification.