A high-power hollow-beam traveling-wave amplifier

The average power capability of beam type microwave amplifiers is limited by the intercepted beam power density in the interaction region. In order to increase the area of the slow-wave structure adjacent to the beam a novel circuit consisting of an inner and outer coaxial structure suitable for interaction with a hollow beam has been developed. The combination of this circuit and a hollow-beam gun of the magnetron injection type has resulted in a traveling-wave amplifier with very unusual characteristics. The Hughes Microwave Tube Division has developed a hollow-beam traveling-wave amplifier using these principles, which provides 100 kw ot peak power, with 10 db gain, over a 10% bandwidth at X-band and possesses a 25 kw average power capability. Moreover, the use of a high perveance hollow beam has resulted in a low voltage design with high C operation. The characteristics of this amplifier are similar to solid-beam amplifiers utilizing coupled-cavity type slow-wave circuits, with the important difference of providing a tremendous increase in the average power capability.