Patent ID: 8120258
Filing Date: 2012-02-21
Classification: H01J

Abstract:
1. A magnetron comprising: an anode cylinder having an inner wall on which a plurality of anode vanes are provided; a pole piece provided on an end side of the anode cylinder; a circular magnet provided on the vicinity of the pole piece; and a magnet ring provided between the anode cylinder and the circular magnet, wherein an outer diameter of the magnet ring is smaller than or equal to the outer diameter of the circular magnet and larger than or equal to the outer diameter of the pole piece, wherein: an outer periphery of the magnet ring has a portion having a thickness which is different from a thickness of the magnet ring at an inner periphery of the magnet ring, and a first thickness of the magnetic ring between a first position corresponding to the outer diameter of the anode cylinder and the outer periphery as a second position are different from a second thickness of the remaining part of the magnet ring, wherein the first thickness of the magnet ring between the first position and the second position is smaller than the second thickness of the remaining part of the magnet ring.