TWT delay lines—Part II: Design and experimental tubes

A voltage-variable delay line with octave bandwidth in L band and a delay range of 500 ns has been developed. This entailed the development of a low energy spread electron beam as the signal carrier. The physical causes of velocity dispersion are discussed, and the expected form of the velocity distribution function is derived. Detailed design considerations and experimental results on several L-band tubes are presented. In particular, the theoretical prediction of a sharp rise in attenuation at a particular delay was confirmed experimentally.