Construction of a multi-cell resonator for a 94 GHz extended interaction klystron

Summary form only given, as follows. Microwave generation at 94 GHz allows high resolution radar, using small antennas and taking advantage of the transmission window of air at that frequency. In communications the higher frequency will allow a larger bandwidth. In an extended interaction klystron a theoretical conversion efficiency of electron beam energy into microwave energy of about 50% is indicated. The available microwave power could be about 30% of the beam power. The intermediate goal is to generated 1 kW available microwave power from a 50 keV, 100 mA electron beam in 16 cells. The construction of the resonator is a critical aspect of the klystron. The cavities are built using a silver soldered sandwich of copper and iron layers which are then turned to a cylinder of about 2.5 mm diameter. The cylinder is copper plated and brazed into a copper tube. A central hole is then drilled and the iron removed using sulfuric acid. A 4-cell resonator will have an outer diameter and an overall, length of about 3.2 mm. Several 4-cell resonators have been built. The surface quality of the resonators has to be improved and the low melting solder has to be replaced with a higher conductivity silver alloy.