Mode competition in a large-orbit coaxial-waveguide cyclotron autoresonance maser (CARM) amplifier

Physics issues of mode competition in a large-orbit coaxial-waveguide cyclotron autoresonance maser (CARM) amplifier are investigated. It is shown that the use of a coaxial waveguide brings about two peculiarities: possible enhancement of the transverse dimensional size and the rarefied spectrum and that the applications of a large-orbit electron beam and CARM mechanism can efficiently exclude the parasitic effect of the cyclotron harmonics and spurious oscillations of undesired modes. The dispersion diagram and numerical simulation demonstrate that mode competition and spurious gyrotron-like or CARM-like oscillations can be suppressed when a large-orbit coaxial-waveguide CARM amplifier operates in a higher-order mode