MEMS-integrated ultra-wideband terahertz traveling wave tube amplifier

An ultra-wideband TWT amplifier is being developed for THz communication, sensing, and imaging applications. Using FDTD-PIC simulation, we demonstrated that, for an electron beam power of 5 kW, a staggered double grating array produces 150 to 275 W, corresponding to 3 - 5.5% efficiency, at 0.22 THz over ~ 30% bandwidth with greater than 12 dB/cm growth rate. The Ka-band cold-test of this circuit has shown excellent agreement with both a theoretical model and simulation analysis in dispersion and attenuation plots, showing a 25% dynamic bandwidth and 0.15 dB/cm attenuation. The circuit has been fabricated by both UV LIGA and high precision CNC machining with ~ 2 - 3 ¿m dimensional tolerance and ~ 30 nm surface roughness and its cold-test setup has been completed. The MEMS-fabricated 0.22 THz electronic circuit will be tested for its dispersion and attenuation measurement. Also, a scandate nano-powder (SC₂O₃-W) cathode has successfully emitted the requisite high current density electron beam of 80 A/cm² (space charge limited) at 1150°C for 800 hrs and currently it is planned to incorporate it in the electron gun and PCM magnet design.