Terahertz transverse-magnetic-wave cyclotron autoresonance maser with a large-orbit relativistic electron beam

The cyclotron autoresonance maser (CARM) operating in a transverse-magnetic (TM) wave by employing a large-orbit relativistic electron beam shows a peculiarity that the growth rate range of coherent amplification of the TM wave is split into two branches as the electrons' cyclotron frequency increases: the upper branch is quite favorable to terahertz operation, whereas the lower branch can lead to a backward-wave CARM mechanism which is suitable to sub-terahertz operation. Compared to a terahertz large-orbit transverse-electric-wave gyrotrons and gyro-amplifiers which are experimentally realized up to date, a terahertz large-orbit TM-wave CARM requires much lower operating magnetic field and allows the cavity to have larger transverse dimension.