Fundamental and second harmonic frequency generation from cusptron

Microwave radiation at fundamental and second harmonic cyclotron frequencies is generated from a cusptron oscillator with a smooth wall circuit. A low-energy, axis-rotating beam of 28–30 kV and 0.8–1.2 A interacts with a single RF-mode in a circular cavity by the negative mass instability. The independently excited modes are TE
11
‘s and TE
21
‘s with radiation power of approximately 2.0 kW and an efficiency of 8.0%.