New technologies used for the 1 THz backward-wave oscillator

For the needs of local oscillators in radiotelescopes, a backward-wave oscillator (BWO) in type 850-1000-GHz bandwidth with 1-mW output power was built. These tubes were fitted with classical vane-type delay lines machined by milling. Because of its small dimensions, the delay line is extremely difficult to build by the standard milling process. A technology has been developed which consists of engraving 100- mu m-thick molds of silicon or polyimide, and then filling them with electrolytic copper. At the present time, BWOs fitted with these delay lines have not oscillated, and the reasons for this behavior are analyzed.<>