10 KW and up from a helix TWT?

Abstract

It is well known that wideband helix traveling wave tubes have been limited to peak power levels of several kilowatts, due to the occurrence of backward wave oscillations (BWO). Continuing advancements in TWT technology, however, have made this restriction a thing of the past. Octave bandwidth TWTs have been developed using helix pitch steps, diameter steps, or resonant loss for BWO stability. It would appear that peak power levels in excess of 50 kW are possible by using a combination of these approaches. This paper will first discuss the design and present performance data of a high peak power 10 kw, octave bandwidth, PPM-focused, conduction-cooled, helix TWT, in which "resonant loss" is the only oscillation suppression technique employed. Secondly, by extending this basic tube design, it will be shown that higher peak power levels can easily be achieved.