A large-signal analysis of beam-type crossed-field traveling-wave tubes

The equations describing a two-dimensional model of a beam-type crossed-field device are presented in a form adaptable to numerical computations. A method of computing the space-charge forces similar to that used by Tien, Walker, and Wolontis in describing the ordinary traveling-wave tube is outlined and the difficulties associated with this method are pointed out. Numerical results covering the interaction of a thin beam with a backward or a forward wave are presented for a variety of space-charge conditions. Space-charge effects reduce the large-signal gain of a backward-wave amplifier; it appears that 70 per cent conversion of available potential energy to RF energy would be excellent efficiency. Space-charge fields appear to have little influence on forward-wave interaction. For either forward- or backward-wave interaction, the computations indicate that a large fraction of the beam current is collected on a very short length of circuit, thus placing a limitation on the average power capabilities of such a crossed-field device.