A Novel Scheme for Gain and Power Enhancement of THz TWTs by Extended Interaction Cavities

A novel scheme is proposed for the enhancement of the gain and output power of terahertz (THz) traveling-wave tube (TWT) amplifiers. The scheme combines a slow-wave structure (SWS) and multigap resonant cavities, resulting in a complementary hybrid of traveling-wave and standing-wave elements, thus offering a compact circuit length. The idea has been verified by a specific design of a 220-GHz TWT amplifier by means of particle-in-cell (PIC) simulations. For an electron beam with a voltage of 21 kV and a current of 200 mA, a maximum gain of 42.22 dB and a 3-dB bandwidth of 6.5 GHz has been achieved while the overall circuit length is only 38 mm. For an input power of 11.25 mW, the CW peak power is predicted to be 187.5 W at 220 GHz, corresponding to an electronic efficiency of 4.47%. These simulation results predict a performance that well exceeds that reported for conventional TWTs, along with a significant reduction of the input power and circuit length.