Behavior of magnetically focused large-signal traveling-wave amplifiers

Many high-power traveling-wave amplifiers operate under confined-flow conditions (high magnetic field) so that there is little radial motion of the electrons. However, the trend in recent years has been toward utilizing near-Brillouin magnetic fields (uniform and ppm) for beam focusing in order to achieve a small, lightweight device. In such a device operating under large-signal conditions, the radial excursions of the electrons can become quite large and may result in premature saturation, a reduction in gain and appreciable circuit current interception, seriously degrading its performance. It is thus of considerable interest to determine the minimum magnetic fields necessary to constrain the beam under large-signal conditions.