Observation of Multi-Frequency Oscillations at Second-Harmonics with a Two-Cavity Sub-THz Gyrotron

The frequency step tuning with second harmonic oscillations in a frequency range from 240 to 360-GHz has been demonstrated. A two-cavity configuration was introduced in order to increase the number of operating frequencies and to decrease their frequency intervals. Each cavity has a series of oscillation modes. These modes can be selectively excited according to the changes in the magnetic field strength, electron beam radii and the velocity pitch factor in the cavity. The experimental results suggest further multi-frequency operation is possible with multiply connected cavities.