A 3 KW pulsed, 10% duty cycle, high gain X-band helix TWT

This paper describes the design and performance of a 3 00 W average, X-band travelling wave tube. The beam is formed with a shadow gridded gun and focused with periodic permanent magnets. Although designed for a narrow-band radar application, peak power of over 3 KW is obtained over the band 7 to 11 GHz. A peak power level of over 4 KW is obtained with optimum adjustment. Gain at saturated output power varies from over 60 db at 7 GHz to 48 db at 11 GHz. Basic efficiency over 20% and depressed collector efficiency of 3 0% is achieved. Excellent stability against oscillation is achieved at all power levels. This is obtained by the use of a fastwave backward wave oscillation suppression technique. The rf design, including oscillation suppression, was carried out with the aid of a large signal computer simulation program. Thermal design includes a special helix support technique which provides high thermal conductivity with minimum dielectric loading of the slow wave structure. Prototype tubes were operated in air cooled ebullient packages, however the high efficiency of this tube would allow cooling by conduction to a base plate.