DEVELOPMENT OF THE OROTRONS AT MILLIMETER AND SUBMILLIMETER WAVELENGTH RANGE

摘要

The frequency range 0.1-1 THz is very attractive for a number of research and technical applications including spectroscopy, diagnostics of various media, communications, etc. However, sources of the coherent radiation in this frequency band are developed much less than the sources of longer waves. For the conventional vacuum tubes based on the stimulated Cherenkov and transition radiation, the main difficulty in the advancement into shorter waves is a dramatic decreasing of the transverse size of the interaction region. Small size also leads to the significant increase of the electron current density. The transverse size of the interaction region can not be increased due to severe mode competition, which can not be avoided in the devices with closed electrodynamical systems. As in lasers and in vacuum tubes based on the Bremsstrahlung radiation (gyrotrons and free electron lasers), this difficulty can be avoided by use of open electrodynamical systems. As for slow-waves devices, this method is used only in the orotron, or diffraction radiation generator (DRG) [1-3]. The open cavity, which is used in orotrons, provides effective selection of transverse modes and allows significant increase of the transverse dimensions of interaction region and increasing the electron current. Therefore, the orotrons and DRGs provide higher output microwave power as compared with backward wave oscillators (BWOs) [4], the most spread oscillators in millimeter and submillimeter wavelength range. Another advantage of the orotron is the high cavity Q-factor that ensures high stability of the frequency. At the same time, the high Q-factor results in a narrow band of electronic frequency tuning.