Generation of Chaotic Terahertz-band Radiation Based on Frequency Multiplication in Gyrotrons

We consider the possibilities of producing wideband chaotic terahertz-range radiation in gyrotrons with excitation of cyclotron harmonics. The transition to the chaotic generation mode in gyrotrons requires a significant excess of the operating current over the starting value, which excludes selective operation at cyclotron harmonics due to the intensification of mode competition. At the same time, it is attractive to use a competition-free frequency multiplication effect that arises due to the nonlinear properties of the electron beam. The implementation of the frequency multiplication regime is simplified when using low-energy electron beams. Based on the averaged model of electron-wave interaction, we simulate generation in a 250-GHz low-voltage gyrotron and demonstrate the regime of a double frequency multiplication providing 0.5 THz chaotic radiation with a bandwidth of about 20 GHz and an average power of 0.5 mW. A significant expansion of the spectrum is achieved through to additional resonant interaction at the intersection points of the dispersion characteristics of the operating mode and the electron beam at the second cyclotron harmonic.