Experimental Demonstration of a 0.34-THz Backward-Wave Oscillator With a Sinusoidally Corrugated Slow-Wave Structure

The design and experimental demonstration of a 0.34-THz backward-wave oscillator (BWO) with a sinusoidally corrugated circular waveguide is presented. The dimensions of the sinusoidally corrugated structure are at the submillimeter scale. Particle-in-cell simulations have predicted that this miniature slow-wave structure (SWS) should be capable of 0.34-THz radiation. The miniature SWS was successfully fabricated using high precision computer numerical control machining and electric discharge machining. In experimental tests, the resulting BWO produced pulse radiation with a peak RF power of ~600 kW and a pulsewidth of 1.66 ns when driven by a 100-kV, 900-A weakly relativistic electron beam. The measured frequency was in the range of 0.32-0.36 THz and the device achieved stable operation at a pulse repetition rate of 10 Hz. We describe the experimental measurement methods of pulsewidth, frequency, and power for the high-power nanosecond terahertz signal. The work is a proof-of-principle demonstration of BWO frequency extension to above 300 GHz through structure miniaturization and precision machining.