Abstract: In a microwave oven magnetron, a first metal cylinder and a ring-like permanent magnet are provided on a magnetron body. Second and third metal cylinders are coaxially arranged in the first metal cylinder so that choking grooves for choking second and fourth harmonic waves are formed between the first and second metal cylinders and the second and third metal cylinders. A ferromagnetic cylinder made of iron or iron alloy is arranged around the first metal cylinder. Thus, a magnetic flux supplied from the permanent magnet into a space inside of the second metal cylinder have axial components which are greater than or equal to 400 gauss in over half the inner space.

Abstract: In a magnetron, anode vanes are radially arranged in an anode cylinder and fixed to the inner surface of the anode cylinder. A cathode is arranged along a tube axis in the anode cylinder. Pole pieces of dish like shape are fixed to openings of the anode cylinder and the anode cylinder is hermetically sealed by cylindrical chambers. Permanent magnet rings are arranged around the cylindrical chambers, respectively, and are magnetically coupled by a yoke. Each of the pole pieces has a flange section, a flat inner disk section and a coupling section extending from the flange section to flat inner disk section. The outer diameter of pole piece is larger than 160% the diameter of an envelope defined by inner ends of the anode vanes. A envelope space contacting the inner ends of the anode vanes has a predetermined magnetic field intensity distribution that is produced by a magnetic flux supplied from the pole pieces and has a difference of not more than 15% along the tube axis.

Abstract: A magnetron comprises a ceramic stem having a cathode support structure. Sealing metal plates are sealed hermetically to the cathode side of the ceramic stem, closing off hermetically the holes running through the stem for the outer connecting leads. The outer connecting leads are connected electrically to the sealing metal plates. The cathode, which is disposed in the center of the anode, is supported by a pair of cathode support rods. The cathode support rods are fixed to the sealing metal plates. In another embodiment, the end-face of the ceramic stem is formed such that the part of the surface of the stem to which the cylindrical metal container, which constitutes part of the envelope of the stem, is sealed by brazing, and those parts of the surface to which the sealing metal plates are sealed by brazing, are positioned substantially on the same plane.

Abstract: A magnetron unit has a magnetic flux path for magnetic flux supplied from a permanent magnet to the interaction space. A magnetic member is disposed outside the anode cylinder for providing a by-path for the magnetic flux supplied from the permanent magnet. This magnetic member is made of a magnetic compensating alloy whose magnetic permeability decreases with an increase in temperature.

Abstract: A magnetron comprises an anode having an inner cylindrical wall and a plurality of copper vanes extending inwardly from the inner cylindrical wall, each vane having a notch in the top and bottom edges thereof. Each notch has an inner side edge, an outer side edge and a bottom edge. Inner and outer ring straps made of metal having a larger tensile strength than the vanes are placed in the notches. The inner ring strap is fixed to the inner side edge of alternative vanes. The inner side edge also has a slanting edge between the connection of the inner ring strap and the bottom edge to prevent cracking.