# US 4,395,657 A · Magnetron unit with a magnetic field compensating means

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- Number: US 4,395,657 A
- Document ID: US4395657A
- Status: Granted
- Kind: A
- Application number: 06/216,677
- Filed: 1980-12-15
- Granted: 1983-07-26
- Earliest claimed: 1979-12-21
- Assignees: Tokyo Shibaura Denki Kabushiki Kaisha
- Inventors: Isao Tada; Toshio Okamura; Akira Kousaka; Kaichiro Nakai
- Web page: https://patentgrep.com/patent/US4395657A

## CPC

- H01J 23/10: Magnet systems for directing or deflecting the discharge along a desired path, e.g. a spiral path (magnetic focusing arrangements H01J23/08)
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## 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.

## Claims

### Claim 1

A magnetron unit comprising:
an anode cylinder having a number of resonant cavities;
a cathode disposed within the anode cylinder and extending along the axis of the anode cylinder with an interaction space defined between the resonant cavities and the cathode;
a pair of pole pieces for generating a magnetic field in the interaction space;
cover means for hermetically sealing the anode cylinder;
a pair of permanent magnet members made of ferrite, disposed outside the anode cylinder and magnetically coupled with the pole pieces, thereby defining a main magnetic flux path in the interaction space; and
at least one magnetic member made of magnetic compensating alloy, disposed between the permanent magnet members and magnetically coupled with the permanent magnet members, thereby defining a magnetic flux bypath parallel to the main magnetic flux path, the magnetic permeability of the magnetic member being reduced as the magnetic member is heated by heat generated in the anode cylinder.

### Claim 2 (depends on 1)

A magnetron unit according to claim 1, wherein said magnetic member is plate-shaped and is attached to the outer circumference of the anode cylinder in such a manner that its plate surface is substantially parallel to the central axis of the anode cylinder.

### Claim 3 (depends on 1)

A magnetron unit according to claim 1, wherein said magnetic member is plate-shaped and its plate surface oppose the outer circumference of the anode cylinder.

### Claim 4 (depends on 1)

A magnetron unit according to claim 1, wherein said magnetic member is plate-shaped and its edge opposes the outer circumference of the anode cylinder.

### Claim 5

A magnetron unit comprising:
an anode cylinder provided with a number of resonant cavities therein;
a cathode disposed within the anode cylinder and along the axis of the anode cylinder, an interaction space being defined between the anode resonant cavities and the cathode;
at least one pole piece for supplying a magnetic field in the interaction space;
cover means for hermetically sealing the anode cylinder;
at least one permanent magnet member disposed outside the anode cylinder and magnetically coupled with the pole piece;
a magnetic flux path being formed in the pole piece and the interaction space; and
an additional permanent magnet for generating magnetic flux in the interaction space in the opposite direction to the magnetic flux supplied from said permanent magnet member, the magnetomotive force of said additional permanent magnet being reduced as the temperature of said additional permanent magnet is raised by heat generated in the anode cylinder.

### Claim 6 (depends on 5)

A magnetron unit according to claim 5, wherein said additional permanent magnet comprises a ferrite magnet.

### Claim 7 (depends on 5)

A magnetron unit according to claim 5, wherein said additional permanent magnet is ring-shaped, and the anode cylinder is located inside said ring-shaped magnet.