Experimental Study on 100MW X-band Relativistic Backward Wave Oscillator

An rippled-wall RBWO is operated at the beam voltage of 250~400kV and current of 2.1~3.4 kA using the 130nsec, single shot using Seoul National University´s electron beam accelerator (SEBA). SEBA produces a hollow beam of 19.2mm-outer radius, 0.7-thickness guided by an axial magnetic field of 1.7-3.4 Tesla. The uniform ripple has a period of 11mm, mean radius of 14mm and ripple amplitude of 2mm. A single cavity-type reflector which excites a TM₀₂ mode and cutoff a TM₀₁ mode at the operating frequency is chosen. Microwave generated by the RB WO is radiated through an 11 cm-diameter horn antenna. The radiation pattern of TM₀₁ mode is measured by fluorescent lamps. The measured and simulated angle of radiation is about 14.9 degree and 13.1 degree, respectively. 110MW microwave was measured at the operating diode voltage of 330kV, the beam current of 2.8kA with the guiding magnetic field of 3.0 T. Efficiency of 12% is obtained by both numerically and experimentally. A typical 20 nsec microwave pulse is measured in the preliminary experiment. The frequency of 11.8GHz is measured by a heterodyne method