High-Power Interdigital Magnetrons

This paper deals with the pill-box-cavity interdigital magnetrons operating in the cavity mode. An analysis of the cathode coupling problem indicates the desirability of cathode decoupling chokes presenting a capacitive impedance to the cathode-anode space. Cold tests and operating tests have confirmed this analysis. The high efficiency to be expected from operation in this mode has been realized, measured efficiencies being comparable to the best obtained in conventional magnetrons. Peak power outputs up to 1.4 kw and continuous outputs up to 500 watts have been obtained in the vicinity of 10 cm wavelength, with efficiencies of about 70 per cent. Tubes built without cathode decoupling chokes operated unstably, gave little power in the cavity mode, and had a strong tendency to operate in the first-order mode.