Development of a 0.32-THz Folded Waveguide Traveling Wave Tube

A traveling wave tube amplifier operating above 300 GHz based on folded waveguide (FWG) slow-wave structure is presented in this paper. The design and test results of key components are presented, including FWG slow-wave structure, electron optic system, and RF windows. The FWG slow-wave structure of this prototype tube was fabricated by the high-speed precision milling technology; the dimension tolerance achieves $\pm 5~\mu \text{m}$ , and fabricated surface roughness achieves 300-nm Ra. This amplifier demonstrates over 130 mW of maximum output power and 19.6 dB of small-signal gain at 318.24 GHz from a 16.9-kV, 16-mA electron beam with a duty cycle of 10%. The operation voltage rising induced by fabrication errors is also discussed.