Transient operation of the relativistic S-band magnetron with radial output

Abstract

The influence of the time-varying accelerating voltage and electromagnetic waves reflected from the output window of the antenna on the operation of a relativistic S-band magnetron with radial output is analyzed. It is shown that within the range of radiation frequencies generated by the magnetron, the antenna with the dielectric window and feed waveguide can be considered as a resonant load. Depending on the phase relations between the reflected electromagnetic waves and those traveling in the magnetron, minimal coupling between the magnetron cavities adjacent to the place of microwave extraction can be realized. In this regime, the magnetron represents an open-end chain of coupled cavities and maintains the effective interaction of the electron flow and generated electromagnetic wave at a decreasing voltage. As the drift velocity of electrons decreases and its difference from the electromagnetic wave phase velocity increases, the microwave frequency changes. The changed frequencies do not necessarily belong to and are not limited by the discrete spectrum of closed resonant ring waveguide structures.