A 2 kW CW L-band traveling-wave tube with octave bandwidth

This paper describes the work to date on the development of a 2 kilowatt CW octave bandwidth traveling-wave tube. The tube is being designed as a light-weight tube which is cooled with vapor phase cooling. The tube uses a helix structure supported by brazed beryllia wedges. The tube is focused by a lightweight aluminum foil solenoid which focuses a perveance
7 \times 10^{-6}
solid electron beam. The solenoid was selected to focus this tube, because it resulted in the smallest sized over-all tube and system package. The total weight of the tube, including the solenoid, is approximately 5 pounds. The tube is 15 inches long and has a maximum diameter, less the connectors, of 2 inches. The tube operates from 700 to 1400 mc. The best results to date have been a measured 1200 watts of CW power. The collector has been operated at 5500 watts of power while being cooled with water which is converted to 100 per cent steam. Efficiencies have been measured greater than 24 per cent beam efficiency and 30 per cent over-all efficiency with collector depression over an octave bandwidth.