Experimental analysis of biased gap klystron

A commercially available multicavity klystron rated at 45 percent efficiency and equipped with external cavities was modified so that a dc potential could be applied across the interaction gaps. When the tube was carefully tuned, an efficiency of 60 percent was obtained; when an accelerating bias was applied across the penultimate gap of the tube, efficiencies of 66 percent were recorded without collector depression, and of over 70 percent with collector depression. In addition, applying bias to the tube made possible efficiencies in excess of 60 percent for a five to one range of power levels (for different cathode voltages). Furthermore, it was possible to apply bias to the tube in such a way that, for a constant drive level, the power output remained constant, the efficiency remained constant at over 50 percent, but the phase could be varied through more than 180°.