Design and Analysis of an Overmoded Slow Wave Structure for High Power Terahertz BWO

New micromachining techniques now provide the technology to fabricate slow wave structure (SWS) which are commonly used in the backward wave oscillators (BWOs) with dimensions suitable for operation in the terahertz region. In this paper, results of theoretical and numerical simulation studies of a large cross section, cylindrical SWS with the rectangluarly corrugated inner wall are presented. The dispersion relation of the overmoded SWS with various dimensional parameters is analyzed, and the distribution of the electrical fields in the specific SWS is also determined. It is found that the steady-state, single-mode operation in this overmoded situation could be realized by the performance of surface wave near the upper cutoff point. Under the condition of 550 kV beam voltage and 1 kA beam current, 2.5 D particle-in-cell simulation predicted that the proposed SWS could be employed in the BWO system to deliver an output power above 40 MW at the frequency of about 0.144 THz with perfect time plot and fine spectrum characteristic.