A 20 kW CW X-band traveling-wave tube

A 20 kW CW traveling wave tube with 200 Mc bandwidth at 7.8 Gc has been designed and tested successfully. Full design bandwidth has been achieved at the 20 kW CW level at efficiencies in excess of 40 per cent. Maximum power output at band center is 30.2 kW at 41.5 per cent efficiency. Depressed collector operation using a single stage collector has permitted CW operation at 46 per cent efficiency. High duty pulsed operation has yielded efficiencies in excess of 50 per cent with depressed collector. The circuit used in this tube is of the coupled cavity type with 5.3 per cent cold bandwidth and midband Pierce impedance of 112 ohms in the first forward space harmonic. An eight-cavity, unsevered circuit provided 16-20 db small signal gain. A confined flow, solid convergent beam at 0.8 microperveance was used with a single stage collector. Focusing was achieved with an open yoke electromagnet.