Ultra-Wide-Band, Frequency-Tunable, Terahertz Gyro-BWO

Cheng-Hung Tsai^1*, Tsun-Hsu Chang¹, Yuusuke Yamaguchi², Toshitaka Idehara²

¹Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
²Research Center for Development of Far-Infrared Region, Fukui University, Fukui, Japan

* Presenter:Cheng-Hung Tsai, email:arthur770410@gmail.com

Gyrotron Backward-Wave Oscillator (Gyro-BWO) with the frequency-tunable capability is a promising source for the frequency-sensitive applications in the terahertz region, such as the hyper-fine structure of positronium and the dynamic nuclear polarization of nuclear magnetic resonance. The frequency tunability is attributed to the internal feedback between the forward-moving electron beam and backward propagating wave . We proposed a tapered cavity structure operated at TE02 mode and centered at 203 GHz with the high-quality beam generated from a non-adiabatic electron source. Simulations carried out by our 2D particle tracing, self-consistent code, and verified with the 3D commercial CST PIC solver, suggests a 3-dB tuning bandwidth of 8.5 GHz. Experimental data, however, shows an even wider bandwidth of 20 GHz by overlapping the adjacent waveguide modes, especially for the TE22 mode. The continuous frequency tunability over a wide bandwidth demonstrates that the proposed Gyro-BWO is an excellent terahertz wave source for many applications.

Keywords: Gyrotrons, Backward Wave Oscillator, Electron Gun