Effective use of dispersion shaping in broadband helix TWT circuits

This paper presents the measured performance characteristics of four broadband TWTs which used various amounts and methods of circuit loading in order to control the helix dispersion. The tubes used identical guns, collectors, and focusing structures, so direct comparisons of the circuit performances could be made. The most heavily loaded circuit, with anomalous dispersion over a large part of the frequency range, performed well over more than two octaves, compared with one octave for a conventional unloaded circuit. The various circuits are described and some factors influencing the choice of a "best" circuit are presented.