Mode control in an overmoded gyrotron oscillator via priming

Control of axial modes is accomplished in a gyrotron oscillator by injection of an external signal into the oscillator. It is found that the external signal need be present only during the initial stages of the pulsed oscillator buildup. It is also noted that the oscillation is not phase locked, due to the low input power level. From these two facts it is seen that priming is the mechanism responsible for the mode control effect. An analysis of the priming phenomenon is made using a quasi-linear theory (in the mode amplitudes) to understand the dependence of the degree of mode control on the external power level.