A Novel Chevron-Shape Double-Staggered Grating Waveguide Slow Wave Structure for Terahertz Traveling Wave Tubes

A novel slow wave structure (SWS), called the chevron-shapeddouble-staggeredgrating waveguide structure, is proposed for traveling wave tube (TWT) amplifier for the terahertz (THz) region. The potential of this SWS is that it provides higher interaction impedance and has low phase velocity; thus, higher output power can be expected at a lower beam voltage. The electromagnetic characteristics and particle-in-cell (PIC) large-signal simulations were performed with CST Microwave Studio software. The SWS was optimized for the central frequency of 200 GHz, which synchronizes with a beam voltage of 18.8 kV in the second spatial harmonic (2π - 3π). A sheet electron beam with a current density of 133 A/cm
²
was used to excite the structure, which interacts with the longitudinal electric field component to provide gain. The reflection coefficient at the port interface is less than -15 dB over the frequency range 181-220 GHz, and a small-signal gain of 30.98 dB is achieved for a tube length of 60 mm.