Analysis of a large-orbit gyrotron in a coaxial waveguide under assistant background fields

The dispersion relation of a large-orbit gyrotron in a coaxial waveguide ex cited in the transverse-electric mode was developed starting from the beam- present wave equation. The relativistic Vlasov's equation was solved under tenuous beam approximations for the perturbed electron distribution functio n, hence the required current density to be used in the wave equation was f ound. The analysis was generalized, with respect to background fields, by c onsidering a de radial electric field and a de azimuthal magnetic field, ov er and above conventional de axial magnetic field. The dispersion relation was solved for the complex frequency far a given propagation constant and t he imaginary part interpreted for the growth rate as well as the saturated efficiency of the device. Similarly, for a given frequency, the dispersion relation was solved for the complex propagation constant and the imaginary part interpreted for the gain of the device, if configured as an amplifier. Two peaks were obtained in the gain-frequency response corresponding to tw o points of intersection between the beam-mode dispersion line and the wave guide-mode dispersion curve. The improvement in the growth rate, gain and s aturated efficiency was predicted by the application of the additional back ground fields. A redistribution of beam kinetic energy between the axial an d transverse electron velocities led to a remarkable enhanced saturated eff iciency at the second peak. A detailed study of the variation of device per formance with respect to the gain and saturated efficiency was presented, f or a wide range of the de background field and electron kinetic energy dist ribution parameters.