Electric lamp and discharge devices: systems – Combined load device or load device temperature modifying... – Discharge device load with distributed parameter-type...
Reexamination Certificate
1999-08-30
2001-12-11
Lee, Benny T. (Department: 2817)
Electric lamp and discharge devices: systems
Combined load device or load device temperature modifying...
Discharge device load with distributed parameter-type...
C315S039510, C315S039630, C313S1030CM
Reexamination Certificate
active
06329753
ABSTRACT:
RELATED APPLICATION
The present application claims priority of Russian Application Ser. No. 98/10/0560, filed on Jan. 5, 1999, entitled “M-TYPE MICROWAVE DEVICE”, which turn claims priority from Russian Application Ser. No. 98/10/0569 filed Jan. 5, 1999, entitled “MAGNETRON”, the disclosures of which are incorporated by reference herein in their entirety.
1. Field of the Invention
The present invention relates generally to the field of electronics and, more particularly, to vacuum electronic devices intended to generate microwave electromagnetic radiation using an electron-transit time, namely to devices known as M-type microwave devices.
More specifically, the present invention relates to structural elements of such devices, namely to cathodes requiring no preliminary incandescence to perform electronic emission.
2. Background of the Invention
In the M-type microwave devices, there are widely used cathodes (which, due to complexity of their structure, would be more accurately identified as cathode assemblies), which make use of a combination of secondary electron emission caused by return to a cathode of a part of electrons traveling in the inter-electrode space along epicycloids, as well as ion bombardment with respect to the cathode, and field emission, that is the phenomenon of electron ejection from a conductor surface under the action of a fairly strong electric field, with the latter emission initiating and maintaining said secondary electron emission.
Methods of improving secondary-emission properties of the cathode are generally known and include fabrication thereof (or its surface coating) from materials such as oxides, in particular oxides of thorium, etc.
A required quantity of field emission is primarily afforded by the shape of corresponding elements and selection of their material, which governs operation of the electron release from a given material into vacuum. Among other things, planar elements (films) having microscopic points (roughness, unevenness) on their lateral surfaces are used as a field-electron emitter. So, the use of such field-emitter located on a focusing flange of the device is described in USSR Inventor's Certificate No. 320,852 granted Nov. 4, 1971 to L. G. Nekrasov et al., for “
Cathode For M
-
Type Microwave Devices”,
Int. Cl. H01J 1/32.
Location of field-electron emitters made in the form of washers along a cathode assembly rod is described in RU Patent No. 2,040,821 granted Jul. 27, 1995 to V. I. Makhov et al., for “
M
-
Type Microwave Device”,
Int. Cl. H01J 1/30. The RU Patent No. 821 is the closest prior art with respect to the present invention.
A need for improving effectiveness of using a working surface of field-electron emitters is still popular in the state of the art, since a field-emission current value is proportional to an emitting area of the field-electron emitter. In view of the fact that a magnetron anode constitutes a cylindrical surface cut by cavity slots, a primary current of the magnetron is dependent upon the location of field-electron emitters relative to an anode cylindrical part having a minimum distance to a working surface of the field-electron emitter.
The increase in primary current to a required value is possible by two ways: either by decreasing a film thickness of the field-electron emitter, resulting in the stepping-up of an electric-field intensity near the surface of an emitter end-face, or by the second way—at the expense of increasing an area participating in the emission, by enlarging a number of field-electron emitters. In doing so, the first way is characterized by augmentation of an effect exerted by electromechanical forces on a field-emission cathode, resulting in the decrease in its mechanical reliability and degradation of its volt-ampere characteristics, whereas the second way is characterized by the fact that a cathode structure of the magnetron becomes more complex, less adaptable to efficient manufacture and less reliable.
SUMMARY OF THE INVENTION
The principal objects of the present invention are: to improve effectiveness of using a working surface of the field-electron emitters; to improve their reliability while increasing stability of field emission and service life of a M-type microwave device, comprising an anode and a cathode having a cylindrical rod with field-electron emitters located on its surface and fabricated as planar discs, and secondary-electron emitters located in the plane perpendicular to a cathode axis, the said emitters providing a primary and secondary emission, respectively.
In accordance with the present invention, these objects are achieved in the arrangement of a M-type microwave device, comprising an anode encircling a cylindrical evacuated cavity and a cathode assembly disposed inside the anode, said cathode assembly comprising a cylindrical rod which is co-axial with the anode, a field-electron emitter made in the form of one or several planar elements mechanically and electrically connected to the cylindrical rod and extending therefrom with a working end-face towards the anode, and a secondary-electron emitter made in the form of one or several sections having an increased secondary electron-emission coefficient, said sections being located on the cylindrical rod surface, the above objects are solved when locating said planar elements such that the normal thereto makes an angle of more than 0 degrees with an axis of the cylindrical rod.
In a preferred embodiment of the present invention, a field-electron emitter in the form of a planar element is located at an angle of more than 5 degrees with respect to a radial plane which is perpendicular to the cylindrical rod axis.
In another preferred embodiment of the present invention, the field-electron emitter in the form of a planar element is located on a spiral path having an axis extending in register with the cylindrical rod axis.
In still another preferred embodiment of the present invention, the field-electron emitter in the form of a planar element is located such that the normal to the surface of said field-electron emitter is perpendicular to the cathode axis. In other words, the planar element surface is located in the plane parallel with an axis passing through the cylindrical rod axis.
According to the present invention, planar elements constituting the field-electron emitter may be isolated with a vacuum gap from those regions (cylindrical rod coatings) which constitute a secondary-electron emitter.
In the preferred embodiments of the present invention, material of field-electron emitters may include impurities of electropositive materials, or impurities of material of the same kind, or both simultaneously, where impurities of material of the same kind are advantageously located at a depth greater than that of the electropositive material.
It is also preferred that a working end-face of said field-electron emitter be fabricated from an amorphous material.
For a number of practical applications, a planar element constituting the field-electron emitter may have cavities in which a film of electropositive material is received. It may be also fabricated with its end-face in the form of a multilayer metal-insulator-metal structure, with each layer having a depth of 2-10 nm.
The field-electron emitter may be fabricated from either tungsten, molybdenum, tantalum, niobium, titanium, or hafnium silicides. It may be also fabricated from amorphous conducting metals and carbide-based alloy, including impurities of electropositive materials.
It is preferred that the working end-faces of planar elements of field-electron emitters be coated with a tunnel-thin dielectric layer also containing impurities of electropositive materials.
Essential distinctions of the proposed M-type microwave device consist in the presence of elements affording primary emission, the elements being disposed on the surfaces the normal to which is not parallel with the cathode axis and makes therewith an angle of more than 0 degrees.
This distinctive feature gives rise to the solution of objectives in accordance with the present inve
Gilman & Berner LLP
Hauptman Lowe
Lee Benny T.
Litton Systems Inc.
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