The multiple-beam klystron

The multiple-beam klystron (MBK) is a device for extending klystron power generation capability at a given frequency by a factor of ten or more. The MBK utilizes a multiplicity of electron beams in conjunction with multiwavelength waveguide circuits. These circuits are periodically loaded and operate in thepi/2-mode. The efficiency, bandwidth, gain and stability of the MBK are equal to or better than that of the single-beam prototype klystron. Furthermore, the MBK permits generation of a given power level at an unusually low voltage, thus minimizing insulation, X-radiation, and modulator problems. An MBK utilizing ten external-circuit klystrons has been built for 750-Mc operation to demonstrate the principle of the device. A single main magnetic circuit is used to focus all beams simultaneously. An RF power output ten times that of one klystron was measured, corresponding to an efficiency of 44 per cent. Bandwidth and gain were identical with single-beam prototype operation. Individual beam drop-out tests were made which showed no disruption of operation in case of the failure of one or more beams. Limited tests tend to confirm the conclusion that the harmonic content of an MBK can be lower than that of a single-beam klystron.