Patent ID: 8159137

Claim:
A magnetron comprising: a cylindrical anode tube in which a plurality of plate-like vanes are radially disposed toward a central axis; a cathode disposed on the central axis of the anode tube by a cathode supporting rod, the cathode including a filament; and a pair of end hats provided in positions on the cathode supporting rod to sandwich the cathode in an axial direction; wherein: the filament is secured by the end hats and includes an axial free length part which is not touched by the end hats, a center of the axial free length part along the axial direction is displaced from a center of the plurality of plate-like vanes along the axial direction, a dimension of the axial free length part is smaller than an axial dimension of the plate-like vanes, a dimension of the entire axial free length part which faces the plate-like vanes is 50% or more and 80% or less of the axial dimension of the plate-like vanes, and an input-side end hat of the pair of end hats is configured such that a boss with a reduced outer diameter extends towards an interaction space, a smaller-diameter boss having a smaller diameter than the boss is formed with a step at the tip of the boss, the smaller-diameter boss of the input-side end hat and one end of a filament constituting the cathode are secured to each other, and the other end of the filament is secured to a boss of an output-side end hat.