The magnetron and the microwave oven: A unique and lasting relationship

Abstract

The advent of the microwave oven allowed the magnetron to avoid obsolescence and become the one well-known source of microwave power. Noteworthy were the cost and weight reductions by ~100 and achievement of ~70% efficiency at 1 kW power. Operation of the cooker magnetron is complex due to varying parameters such as microwave load, anode current (rectified) and the cold-start process. These phenomena include several types of moding, damaging voltage transients, axial electron discharges, end-space oscillations and arcing phenomena including a fireball at the magnetron antenna. Prominent are spurious space-charge oscillations similar to those in the M-type backward-wave oscillator, which are affected by filter-box impedance. Alternative but discarded designs include a GE 600 Volt magnetron for its 915 MHz range, the Kumpfer magnetron made by Samsung, ~1980, and a 400 Volt magnetron made by Panasonic. Failed attempts to replace the cooker magnetron include the multiple-beam klystron and solid-state. The future of the cooker magnetron is assured. Its performance reveals unexplained phenomena, the study of which is key for a complete understanding of the magnetron.