Permanent magnets of different magnetic materials for magnetrons
AssigneeTokyo Shibaura Electric Co., Ltd.
InventorHiroshi Miura
Life of this patent
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Abstract
A magnetron comprises an anode cylinder, vanes extending from the inner surface of the anode cylinder toward the central axis of the anode cylinder, a cathode disposed at the central axis of the anode cylinder, an output antenna coupled in a high frequency coupling mode to the vanes, and a set of permanent magnets for creating a magnetic field having a line of magnetic force directed toward the axis of the anode cylinder. The set of permanent magnets constitutes a combination of, for example, an alnico magnet and rare earth magnet differing in coercive force.
Claims17
A magnetron comprising:
- an anode in which resonance cavities are defined,
- a cathode disposed at the axis of the anode,
- a pair of permanent magnets creating a magnetic field in a direction substantially vertical to an electric field produced between the anode and cathode,
- one of the permanent magnets being made and readily magnetizable and demagnetizable magnetic material and the other being made of difficultly magnetizable and demagnetizable magnetic material having a larger coercive force than that of the magnetic material of the said one of the permanent magnets,
- A yoke magnetically coupled to the pair of permanent magnets, and
- sealing means for hermetically sealing the anode.
A vane-type magnetron comprising:
- an anode having an anode cylinder and vanes extending from the inner suface of the anode cylinder toward the axis of the anode cylinder to define resonance cavities within the anode cylinder,
- a pair of permanent magnets disposed at both opening ends of the anode cylinder, respectively and in alignment with the axis of the anode cylinder to create a magnetic field in a direction substantially vertical to an electric field created between the vane and the cathode and in a direction transverse to the axis of the anode cylinder,
- one of the permanent magnets being made of readily magnetizable and demagnetizable magnetic material and the other being made of difficultly magnetizable and demagnetizable magnetic material having a larger coercive force than that of the magnetic material of the said one of the permanent magnets,
- a yoke extending outside the anode cylinder and magnetically coupled to the pair of permanent magnets, and
- sealing means for hermetically sealing the anode.
A method for manufacturing a magnetron comprising an anode in which resonance cavities are defined, a cathode disposed at the axis of the anode, a pair of permanent magnets creating a magnetic field in a direction substantially vertical to an electric field produced between the anode and cathode, one of the permanent magnets being made of readily magnetizable and demagnetizable magnetic material and the other being made of difficultly magnetizable and demagnetizable magnetic material having a larger coercive force than that of the magnetic material of the said one of the permanent magnets, a yoke magnetically coupled to the pair of permanent magnets, and sealing means for hermetically sealing the anode, the method comprising:
- magnetizing the said other permanent magnet of difficultly magnetizable and demagnetizable magnetic material before it is incorporated into a magnetron;
- magnetizing the said one permanent magnet after it is incorporated into the magnetron together with the said other permanent magnet;
- and
- adjustably demagnetizing the said one permanent magnet by a magnetic field of an intensity as not to cause demagnetization of the said other permanent magnet to create a predetermined magnetic field in a space between the anode and the cathode.
Dependencies are inferred from the claim text.