Frequency-tunable Sub-THz Gyrotrons with External Mirrors

An approach that ensures the implementation of sub-terahertz frequency-tunable gyrotrons on the basis of a combination of a low-Q irregular cavity and an external reflector is described. Numerical calculations and theoretical analysis predict possibilities for the realization of a fundamental-cyclotron-harmonic gyrotron operating in a wide (∼ 10%) frequency band with high (10% and higher) efficiencies. A similar gyrotron operating at the second harmonic of the electron cyclotron frequency can ensure an output wave efficiency of the order of 10% within a ∼ 1% band of the continuous frequency tuning.