Patent ID: 7548026

Claim:
A magnetron comprising: an anode assembly having an approximately cylindrical anode tube body, an even number of plate shaped vanes fixedly mounted to an inner circumference of the anode tube body and radially arranged from the inner circumference of the anode tube body to a central axis, and large and small strap rings for electrically connecting the plate shaped vanes to each other; and a cathode assembly inserted on the central axis of the anode assembly, wherein an end portion of each plate shaped vane positioned on the central axis of the anode tube body is formed in a step shape whose thickness in a range of a predetermined length L from the end thereof is smaller than other portion, and wherein the step shape, when viewed in the direction of the central axis, creates a reduced thickness in the innermost portion of each plate shaped vane, wherein, when a plate thickness of the base substrate of the plate shaped vanes is t 0 , the thickness of the end portion which is thinned in a step shape is t 1 , a distance between ends of adjacent plate shaped vanes is w, and the number of the plate shaped vanes is N, and wherein N, L, t 0 and t 1 satisfy the following equations: w /(t 1 + w )≦0.5 L ≧{(t 0 −t 1 )/2}÷tan (180/ N ).