Dispersion characteristics of spiral-corrugated cylindrical waveguide for a gyro-TWT amplifier

Summary form only given, as follows. The electromagnetic wave dispersion characteristics of a cylindrical waveguide can be modified by a wall perturbation in the form of a spiral corrugation, to create a periodic structure which resonantly couples modes of differing azimuthal order. Due to asymmetry of the coupling with respect to left- and right-handed modes, and to forward and backward waves, a propagating eigenmode may exist having infinite phase velocity (k/sub 2/=0) but nonzero group velocity. For a traveling wave amplifier, such a dispersion characteristic may permit operation with increased bandwidth and reduced sensitivity to beam velocity spread by operating close to the point k/sub 2/=0. Numerical calculations are presented to show the beam-coupled dispersion characteristics, stability and gain profiles of such an amplifier based upon a simple, coupled wave theory.