Mode control is achieved for the first time in a highly overmoded, pulsed rf oscillator by injection of an external electromagnetic signal (priming). The drive signal power, frequency, and time of application determine the degree of mode control. The regime of parameter space over which a primed gyrotron operates in a single stable mode is increased by ∼40%. A coupled mode theory is used to model the drive power dependency of the priming effect. Priming may allow gyrotrons to operate at increased efficiency as well as stabilize other overmoded coherent radiation sources.

• Received 19 November 1987

DOI:https://doi.org/10.1103/PhysRevLett.61.2316