DEVELOPMENT OF A MILLIMETER WAVE GENERATOR USING A FIELD EMISSION CATHODE

A feasibility study is reported for the development of electron guns with field emission cathodes, and of the application of these guns to microwave and millimeter wave oscillators. Experimental data were obtained with both coated and uncoated tungsten emitters, and also with several electron gun configurations. Data were obtained at both X-band (10 gigacycles) and at 70 gigacycles. Two X-band models of the 1-3/4 mode FDTK were successfully operated. Good agreement was obtained between the calculated and measured values of beam conductance required to start oscillations. A peak power output of 16 watts was obtained. It was determined that a short magnetic lens was the focusing best suited for the 70 gigacycle oscillator. A zirconium-coated tungsten cathode was used so that all of the emitted beam would be well within the 20 to 25 degree acceptance angle of the lens. The beam conductance was increased by spacing gridless decelerating electrodes along the converging portion of the beam. The potential distribution on these electrodes was such that the beam voltage was decreased by a factor of four prior to entering the cavity. Guns of this type were successfully tested, but in the assembled oscillator tube the beam conductance obtained was below the value required to start oscillations. (Author) Available copy will not permit fully legible reproduction. Reproduction will be made if requested by users of DDC. Copy is available for public sale. See also: AD-417 279.