Theoretical background of electron cyclotron plasma maser

Summary form only given, as follows. Theoretically, all benefits of plasma can be saved at rather low plasma density in the electron cyclotron plasma maser or plasma-filled gyrotron. It exploits the cyclotron instability of a gyrating beam in a smooth waveguide filled with a tenuous magnetized plasma. A tenuous magnetized plasma can significantly modify the electromagnetic properties of TE modes splitting their dispersion curves just in the narrow frequency band. In this frequency band, plasma also causes a significant growth of the azimuthal electric field which provides azimuthal bunching of the gyrating electron beam. It will be shown that a rather tenuous plasma can substantially improve the beam-wave coupling, increase bandwidth, tunability, and output power compared to conventional vacuum gyrotrons, whereas all above-mentioned negative effects become less serious compared to the devices of traditional plasma electronics.