Millimeter-wave orotron oscillation - Part II: Experiment

Experimental observation of orotron oscillation is reported in the frequency band from 53 to 73 GHz. The output power in a quasi-CW mode and beyond an output window is approximately 100 mW at a beam current of 90-100 mA. Oscillation has been observed on several modes of the open resonator of the orotron, with starting currents ranging from 35 to 82 mA. The electronic tuning transconductance within a single mode was measured by mixing the orotron signal with another signal from a klystron, yielding MHz/V. The spectrum of the orotron output signal was also measured by this method, and the linewidth was determined to be less than 0.4 MHz at 70 GHz.