A nonreentrant crossed-field amplifier with cycloiding injected beam

Nonreentrant injected-beam crossed-field amplifiers usually employ a thin laminar beam positioned well above the sole electrode. In operation, the beam is gradually bunched by a phase-focusing action. This paper describes the analysis and demonstration of such an amplifier, with an important difference: the electrons of the beam have random cycloidal trajectories extending to the sole instead of following the usual linear paths, Rapid and effective bunching is accomplished by collecting antiphase electrons on the sole. Experimental results are presented to show that the approach is useful for high current beams. For example, an output power of 600 watts was obtained at 10 dB gain from an 800 mA beam. The advantages and disadvantages of the cycloidal motion are discussed. The results of computations are given to show the desirable characteristics attainable; for example, a design for an amplifier with a cycloiding beam requires only 35 percent of the interaction length of a laminar-beam type for the same computed power output, gain and efficiency at the same cathode voltage.