Study of a High-Efficiency 34-GHz Sheet Beam Extended Interaction Oscillator With Low Filling Factor

In this paper, high-efficiency low-filling-factor sheet beam extended interaction oscillator (SB-EIO) with an improved ladder structure is discussed. The Ka-band cavity with nine gaps is designed to operate at 2π mode. A sheet beam (8 mm × 0.6 mm) of 34 kV and 3.5 A is injected into SB-EIO through a beam tunnel of 12 mm×1.2 mm. The axial electric field distribution and the synchronization conditions are optimized to improve the beam-wave interaction efficiency. An effective method is explored and utilized to suppress the mode competition. A stable output power of 35.9 kW and 30% efficiency are obtained for a 0.56 filling factor in narrow direction and 0.67 filling factor in wide direction. An output power of 22.8 kW and 19.1% efficiency are also attained even with a 0.4 filling factor in narrow direction and 0.67 filling factor in wide direction.