High-power, lightweight, PPM-focused coupled-cavity TWTs

The achievement of high power with light weight and compact size in Varian´s coupled-cavity TWTs is accomplished by using several unique design features not commonly used in other coupled-cavity tube designs. These features include stability and sever designs that allow small magnet sizes, the use of relatively large diameter electron beams reducing the required magnetic focusing fields, and the use of high energy product magnets. The sever designs used also lead to excellent gain and phase ripple performance. Polepiece designs provided with extra thermal conductive capacity and giving low transverse magnetic fields are also used in these tubes. These, and other design features leading to high-average power with good beam focusing, are discussed. Performance data, using the design features discussed, will be presented on several X-band TWTs. Special air-cooling designs for depressed collector operation will also be shown and discussed.