CW Source of Two-Frequency K-Band Radiation Based on a Gyrotron With Output Reflections

We study a
${K}$
-band gyrotron operating at the second harmonics of the gyrofrequency with reflections of the output radiation from the mismatched vacuum window. We observe the regime of simultaneous excitation of neighboring axial cavity modes under conditions of close values of their quality factors. Two-frequency radiation with a mean power of about 0.5 kW and efficiency of about 3% is obtained.