Patent ID: 6985042

Claim:
A magnetron comprising: an anode comprising plural vanes whose one end is fixed on the inner wall of a cylindrical anode shell and their inner ends opposite to the one ends are radially extended toward the center of the anode shell, and of plural hollow confined spaces formed between adjacent ones of the plural vanes; a cathode provided at the center of the anode; and a pair of pole pieces arranged at both sides of side surfaces of the vanes in such a manner that a magnetic field nearly parallel to the cathode can be applied on the interaction space where the inner ends of the vanes and the cathode face with each other; wherein at least one of the pair pole pieces is so positioned that an inner end of the pair of pole pieces is within 0.015 λ from the side surfaces of the vanes in the range extending from the inner ends of the vanes to a point at least ⅓ of the vane length; wherein λ is the oscillation wavelength of the magnetron, and said vane length is a distance from said one end to said inner end wherein the vane length is a distance from said one end to said inner end of a respective vane.