Analysis of helically arbitrarily-shaped groove-waveguide traveling-wave-tube (TWT)

Summary form only given. A TWT using helically grooved waveguide can be used for the generation of the high-power millimeter waves taking its advantages of a large transverse size, excellent thermal dissipation capability and low loss over the conventional TWT´s. This work first gives a general theoretical analysis of the helical arbitrarily-shaped groove waveguides, which is applicable to both slow-wave and fast-wave regimes. The unified expressions are derived and the properties obtained for dispersion relation, phase velocity, power flow and interaction impedance. The drawn conclusions are (1) the influence of the groove shape on the low cut-off frequency, phase velocity, group velocity and the power flow in system are great at certain groove depth; (2) the helical swallow-tailed groove waveguide with a deep groove depth has weakest dispersion in comparison with the other ones having different groove profile; (3) the helical triangle-shaped one is proposed for use as interaction system for gyro-TWT, with advantages of wide frequency range and larger transverse electric field.