Patent ID: 7053556

Claim:
A magnetron comprising: an anode cylindrical body; a plurality of anode vanes provided to project from an inner wall surface of the anode cylindrical body toward a central axis; a large-diameter equalizing ring and a small-diameter equalizing ring for electrically connecting the plurality of vanes to every other vane; and a pair of funnel-shaped pole pieces provided at ends of both openings of the anode cylindrical body in an axial direction, wherein a radius Rp of a flat portion of the pole piece closer to an upper or lower edge of the anode vane is equal to or larger than a radius Rs 2 of an inner circumference of the large-diameter equalizing ring, and when a radius of an outer circumference of the small-diameter equalizing ring is Rs 1 , a radius of the inner circumference of the large-diameter equalizing ring is Rs 2 , a radius of a circle inscribed in a leading edge of the anode vane is Ra, and a minimum length between the pole pieces in the axial direction is Lg, the values of Ra, Rs 1 , Rs 2 , and Lg are set so as to satisfy the following Expressions 1 and 2: 1.85 Ra ≦( Rs 1+ Rs 2)/2≦1.96 Ra , and [Expression 1] 2.84 Ra≦Lg≦ 3.0 Ra. [Expression 2]