Patent ID: 7023137

Claim:
A magnetron comprising: an anode portion having a cylindrical anode and a plurality of vanes secured to the inner wall of said anode and disposed radially, a cathode portion having a coil-shaped filament disposed substantially coaxial with said anode portion, a pair of magnetic poles disposed at the upper and lower ends of said filament in the axial direction of the cylinder of said anode portion, ring-shaped permanent magnets disposed substantially coaxial with said anode portion and magnetically coupled to said pair of magnetic poles, respectively, thereby forming a magnetic circuit, and an input portion and an output portion disposed on the outsides of said pair of magnetic poles, respectively, in said axial direction of the cylinder, wherein the diameter of the inscribed circle at the cathode-side ends of said vanes constituting said anode portion is in the range of 7.5 to 8.5 mm, and the height of said vanes in said axial direction of the cylinder is 9.0 mm or more when the outside diameter of said coil-shaped filament constituting said cathode portion is in the range of 3.4 to 3.6 mm, and when the ratio G/(G+T) of the gap G between the cathode-side ends of the adjacent vanes and the thickness T of said vanes is in the range of 0.20 to 0.25.