The work reported here is aimed at investigating the feasibility of achieving low noise microwave amplificationspecifically: 20 db gain, 6 db noise figure at 10 kMc, and 1 kMc bandwidth -by using tunneling. It has been concluded that the most promising approach to achieving these objectives is through the use of a thin film cathode operating in conjunction with a microwave structure. At present, it is possible to build tunnel cathodes which exhibit sufficient current density to permit their use

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... in a 10 kMc travelingwave tube. However, the life of the cathodes under both dc and pulsed operation is by no means satisfactory. For this reason, efforts were directed towards obtaining better stability and life by improving the uniformity and dielectric strength of the thin inculating layer. To demonstrate the usefulness of tunnel cathodes in a travelingwave tube, some prototype cathodes were built and incorporated in a suitable gun structure. The focused electron beam was imaged on a phosphor scr&-en. The emission appeared to be quite uniform in this structure as well as in a projection tube image. Work was continued towards controlling the insulator thickness by ellipsometry.