The design, construction, and performance of an experimental low-noise backward-wave amplifier electronically tunable over a frequency range of 12 to 18 kmc are reported. The design objectives of a constant 50-mc bandwidth over the tuning range, and 20 db gain, led to an investigation of two- and three-helix cascade designs. The Currie-Forster curves for a two-helix cascade design were extended to a three-helix cascade design. Dielectric loading studies of rod- and flute-supported helices were made, and a DLF of 0.91 was obtained. The low-noise hollow-beam electron gun, and the construction used to minimize beam interception, are described. Several types of transducers were in-vestigated in order to avoid the more conventional, fragile, direct-pin transducer. The latter was finally employed after the objections to it were partially overcome. The performance of the experimental tubes is summarized, and possible reasons for the behavior of the tubes are given. Recommendations are made to guide any future activity of a similar nature.
展开▼
