The effect of various design parameters on the performance of medium-power traveling-wave tubes

In the design of traveling-wave tubes, the effect of changing such design parameters as beam current, frequency, or helix diameter is usually not immediately obvious. This paper makes the effect of some major design parameters more apparent by introducing certain approximations. Within the limits of the approximations, the gain-helix radius product is shown to depend only on beam perveance and a geometry-determined factor F. For a given geometry (defined as the ratios of all radial dimensions),
C
and
QC
are derived from
\gamma a
and beam perveance. Thus, universal graphs for gain per unit length,
C
and
QC
, are evolved. By keeping
\gamma a
, beam perveance and tube geometry invariable, the RF behavior of traveling-wave tubes can be preserved. Consequently, scaling equations for traveling-wave tubes can be derived, and are presented in this paper.