EP0121564B1 - Method for fabricating a dispenser-reservoir housing for a dispenser cathode - Google Patents
Method for fabricating a dispenser-reservoir housing for a dispenser cathode Download PDFInfo
- Publication number
- EP0121564B1 EP0121564B1 EP83903655A EP83903655A EP0121564B1 EP 0121564 B1 EP0121564 B1 EP 0121564B1 EP 83903655 A EP83903655 A EP 83903655A EP 83903655 A EP83903655 A EP 83903655A EP 0121564 B1 EP0121564 B1 EP 0121564B1
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- EP
- European Patent Office
- Prior art keywords
- mandrel
- coating
- dispenser
- reservoir
- housing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- 238000000034 method Methods 0.000 title claims abstract description 18
- 239000000463 material Substances 0.000 claims abstract description 59
- 239000011248 coating agent Substances 0.000 claims abstract description 24
- 238000000576 coating method Methods 0.000 claims abstract description 24
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 17
- 239000010937 tungsten Substances 0.000 claims abstract description 17
- 238000005229 chemical vapour deposition Methods 0.000 claims abstract description 8
- 238000004891 communication Methods 0.000 claims description 3
- 238000005530 etching Methods 0.000 claims description 2
- 238000005553 drilling Methods 0.000 abstract description 2
- 230000003213 activating effect Effects 0.000 description 19
- 238000013459 approach Methods 0.000 description 7
- 238000005219 brazing Methods 0.000 description 7
- 239000011888 foil Substances 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 229910052788 barium Inorganic materials 0.000 description 4
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical group [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 4
- QVQLCTNNEUAWMS-UHFFFAOYSA-N barium oxide Chemical compound [Ba]=O QVQLCTNNEUAWMS-UHFFFAOYSA-N 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 3
- FQNGWRSKYZLJDK-UHFFFAOYSA-N [Ca].[Ba] Chemical compound [Ca].[Ba] FQNGWRSKYZLJDK-UHFFFAOYSA-N 0.000 description 3
- 229910052750 molybdenum Inorganic materials 0.000 description 3
- 239000011733 molybdenum Substances 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 238000005382 thermal cycling Methods 0.000 description 3
- 238000007740 vapor deposition Methods 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical group O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000009760 electrical discharge machining Methods 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- -1 tungsten metal compound Chemical class 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
- H01J1/02—Main electrodes
- H01J1/13—Solid thermionic cathodes
- H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
- H01J1/28—Dispenser-type cathodes, e.g. L-cathode
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
Definitions
- This invention relates to control porosity dispenser cathodes and methods for making the same.
- This invention is a further advance pertaining to the structure of and the method for fabricating controlled porosity dispenser cathodes.
- Thermionic emission cathodes of the type that can be used in microwave tubes such as traveling wave tubes are, in many applications, required to have high reliability and long life. It is also desirable that all areas of the cathode surface be operated in a space charge limited mode for more stable operation.
- cathodes such as the "B”, the "S” and the “M” types, are made of random porosity structures impregnated with barium calcium aluminate compounds and generally tend to provide a non-uniform emission over the surface of the cathode. The result is that excessive temperatures are required to assure that space charge limited emission is achieved in less active areas of the cathode surface. Consequently, the more active areas become excessively hot resulting in decreased reliability and shortened life. The end result is that emission is gradually reduced as the pores become depleted of the impregnant. Examples of these types of cathodes are disclosed in U.S. Patent No. 2,700,000, issued on January 18, 1955 to R. Levi et al. and U.S. Patent No. 2,722,626, issued on November 1, 1955 to P. P. Coppola et al.
- a method for fabricating a dispenser-reservoir housing for a controlled porosity dispenser cathode characterised by the steps of:
- the step of coating is by chemical vapor deposition and the coating material is tungsten.
- the mandrel is removed such as by etching it away, thereby leaving the hollow housing of tungsten which will serve as a reservoir for an activating material.
- This housing then has an array of apertures drilled in the top surface such as by a pulsed laser thereby creating a controlled porosity emitter-dispenser surface.
- the reservoir of the structure can be filled from the open end with a barium calcium aluminate compound or other barium bearing compound that will decompose when heated, thereby supplying activating material to the emitter-dispenser surface through the array of apertures.
- the filled housing can then be attached to a heater structure to make a complete dispenser cathode.
- This housing is featured in that it is constructed of a single material wherein the crystalline-atomic bonding of the top surface and the side walls of the housing forms an essentially monolithic or single piece.
- Several advantages include control over the crystalline orientation in the top surface member which becomes the emitter-dispenser surface and the fact that there is little likelihood of contaminates forming on the emission-dispenser surface during fabrication. Consequently, the work function of the surface is generally uniform whereupon there is a high degree of emission uniformity across this surface.
- the dispenser cathode can be operated at a lower temperature than other dispenser cathodes of the controlled porosity type as a result of the feature of the support-thermal cross members which tend to distribute the heat more deeply and uniformly into the activating material and to the emitter-dispenser surface. As a consequence, it is able to produce a higher emission density for a given temperature than was heretofore obtained and a more stable emission at these lower temperatures. Moreover, at these lower temperatures there is a lower evaporation rate thereby resulting in a reduced loss of the activating material barium and barium oxide (Ba + BO).
- Still another advantage is that the structure is not likely to delaminate or fail during thermal cycling as a result of its unitary and single material construction.
- the process and structure has the added manufacturing advantages that it: reduces the number of manufacturing steps; reduces the hand work required; is suitable for large scale production; allows very thin wall structures to be readily fabricated; and results in an easily replicated, precision structure.
- FIG. 1 is illustrative of a first step of fabrication in which a mandrel is formed having a configuration generally similar to the configuration of the final emitter-reservoir housing.
- the mandrel 20 is cylindrical and is made of molybdenum. It should be understood that the mandrel could be made of other materials which are capable of withstanding the temperatures at which the subsequent fabrication steps take place and which are otherwise compatible with these steps.
- the end face 22 of the mandrel 20 is slotted with two intersecting slots 24 and 26 which extend into the body of the material at right angles to each other and are preferably both in a plane coextensive with or collateral with the axis of the mandrel.
- the slots 24 and 26 extend across the diameter of the mandrel.
- These strips are of the same material that the remainder of the emitter-reservoir housing will be made from. While tungsten is used in the preferred embodiment, it could be of any other material which has an attractive work function and which is capable of withstanding the operating temperature of the control porosity dispenser cathode over extended periods of time.
- These strips 28 and 30 are brazed together and in place by copper brazing material 32.
- the mandrel 20 is machined down to remove the surplus brazing material 32 and the edges of the strips 28 and 30 which protrude beyond the side and end surfaces of the mandrel 20 so that the strip edges are flush with the surface of the mandrel.
- a shoulder 34 is formed.
- the mandrel 20 is subjected to chemical vapor deposition process in which a tungsten coating 36 (not drawn to scale) 0.1016 mm (0.004 of an inch) thick is formed on the mandrel surface. During this chemical vapor deposition step, the edges of the strips 28 and 30 atomically bond to the tungsten coating 36.
- This vapor deposition step can be accomplished in a quartz reaction chamber in which reactive gases of the tungsten metal compound will flow across the heated mandrel to form the deposited layer.
- the heat for the mandrel can be supplied by an inductive type power supply and the flow rate of the gases can be controlled.
- end surface 22 of the mandrel is machined into a spherical- radius concave surface 38 such as by electrical discharge machining.
- This surface 38 is dependent upon the end application of the cathode and the type of beam focusing to be used. Thus, this surface 38 could have been left flat or have other configurations for certain types of applications and beam focusing.
- tungsten 40 is formed upon the exposed surface of the first tungsten coating 36 and the exposed mandrel concave surface 38 by means of the chemical vapor deposition process.
- the term "thin” as used herein is about 0.0254 mm (0.001 of an inch) thick in the preferred embodiment. However, it could also be somewhat less or somewhat greater depending upon the structural integrity of the layer or upon the ease at which the electron emitting material is to migrate to the emitting surface. For example, the range could be between about 0.0127 mm (0.0005 of an inch) and 0.127 mm (0.005 of an inch) or, in some cases, more. Care must be taken to be sure that this layer is not so thin that the activating material will readily evaporate or so thick that the activating material will not readily migrate to the emitter surface through the pores to be formed.
- the two layers of tungsten 36 and 40 bond together by atomic crystalline growth to form a monolithic or single piece of a single material with a somewhat thickened side wall.
- the tungsten coating which forms the concave emitter-dispenser 42 atomically bonds to the exposed edges of the strips 28 and 30 which form the mechanical- thermal supports. These strips serve to hold the thin wall emitter-dispenser 42 in its precise configuration and will subsequently serve to distribute heat into an activating material as well as to the emitter surface.
- the end segment of the mandrel 20 holding the configured tungsten coating is cut off at about a plane coextensive with the lower edges of strips 28 and 30, and the molybdenum mandrel 20 is removed such as by a differential solvent thereby forming a hollow housing with a reservoir 44 formed therein.
- a differential solvent which has been found to be effective is nitric acid which etches the molybdenum and any remaining copper brazing material 32 but does not significantly affect the tungsten.
- mandrel 20 is used for the mandrel 20, or the housing 48, it may be necessary to use another differential solvent.
- an array of apertures 46 is formed through the emitter-dispenser 42 in open communication with the reservoir 44. It is preferable that these apertures be of small diameter, closely spaced and in a precise pattern. Accordingly, one way that these apertures have been formed is by laser drilling in which apertures 5.0 microns in diameter on centers spaced 15.0 microns apart have been formed. This results in a controlled porosity emitter-dispenser 42.
- the reservoir 44 of the hollow emitter-dispenser housing 48 is filled with an activating material 50 through the open end thereof.
- activating material 50 which has been found to be particularly useful is a mixture of 80% by weight of barium calcium aluminate having a 5:3:2 mole ratio and 20% by weight of tungsten powder.
- barium bearing compounds that will decompose when heated to supply activating material to the emitter surface of the emitter-dispenser 42 can be used.
- a controlled ' porosity dispenser cathode is formed by attaching the filled emitter-dispenser housing 48 to a heater assembly 54.
- the heater assembly 54 includes a hollow support member 56 made of a high temperature resistant material such as tungsten which encloses a heater coil 58 potted in a thermally conductive material 60 such as aluminum oxide AI 2 0 3 .
- the emitter-reservoir housing 48 is affixed to the end thereof such as by brazing. Thereafter, heat from the heater coil 58 is conducted to the activating material 50 thereby causing barium and barium oxide to migrate both along the interspace between the emitter-dispenser 42 and the activating material 50 and directly through the apertures 46 to the emitter surface of the emitter-dispenser 42 thereby continuously replenishing the activating material on the surface as it is used up during electron emission.
- the strips 28 and 30 also provide thermal conductivity into the activating material 50 and to the emitter surface thereby providing for efficient operation of the overall device.
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Vapour Deposition (AREA)
- Cold Cathode And The Manufacture (AREA)
Abstract
Description
- This invention relates to control porosity dispenser cathodes and methods for making the same.
- This invention is a further advance pertaining to the structure of and the method for fabricating controlled porosity dispenser cathodes.
- Thermionic emission cathodes of the type that can be used in microwave tubes such as traveling wave tubes are, in many applications, required to have high reliability and long life. It is also desirable that all areas of the cathode surface be operated in a space charge limited mode for more stable operation.
- Conventional cathodes, such as the "B", the "S" and the "M" types, are made of random porosity structures impregnated with barium calcium aluminate compounds and generally tend to provide a non-uniform emission over the surface of the cathode. The result is that excessive temperatures are required to assure that space charge limited emission is achieved in less active areas of the cathode surface. Consequently, the more active areas become excessively hot resulting in decreased reliability and shortened life. The end result is that emission is gradually reduced as the pores become depleted of the impregnant. Examples of these types of cathodes are disclosed in U.S. Patent No. 2,700,000, issued on January 18, 1955 to R. Levi et al. and U.S. Patent No. 2,722,626, issued on November 1, 1955 to P. P. Coppola et al.
- In order to attain the goals of long life and reliability, a number of approaches have-heretofore been used. Previously, a thin layer of porous metal was formed directly on the emitting surface of the reservoir of activating material such as by evaporation in a vacuum, by electroplating or by vapor deposition. These approaches are disclosed in U.S. Patent No. 3,155,864, issued to P. P. Coppola on November 3,1964 and in U.S. Patents Nos. 3,243,637 and 3,243,638 issued to J. H. Affleck III on March 29, 1966.
- Shortcomings in these approaches are that the porosity of the emitter surface is random rather than precise and coating directly to the activating material could block many of the pores.
- One of these more recent approaches is disclosed in U.S. Patent No. 4,101,800, issued on July 18,1978 to R. E. Thomas wherein a reservoir of activating material is covered by a perforated metal foil. The perforations enable migration of electron emitting material from the reservoir of activating material to the foil surface to coat the surface thereby providing a cathode surface of somewhat uniform emissivity.
- Subsequently, an advance was made in the fabrication of such structures as disclosed in U.S. Patent No. 4,310,603, issued on January 12, 1982 to L. R. Falce. In this approach, a perforated metal foil having an appropriate pattern of pore size apertures therein is formed. Thereafter, this foil is bonded to a generally cylindrical housing such as by brazing, welding or diffusion bonding.
- Several disadvantages of this last approach are that: the high temperatures associated with the bonding process cause recrystallisation of the foil material; the use of dissimilar brazing materials subject the foil surface to contaminates whereupon the foil has a non-uniform work function; and the braze material can block some of the apertures in the emitter surface. On top of this, the brazing or welding with unlike materials creates a distinct possibility that the bond will fail during thermal cycling. Moreover, fabrication of this kind of device requires a large number of hand processing steps.
- According to the present invention, there is provided a method for fabricating a dispenser-reservoir housing for a controlled porosity dispenser cathode characterised by the steps of:
- coating the side surface and adjacent end surface of a mandrel with a layer of a material to form a monolithic coating of said material by means of crystalline growth;
- removing the mandrel to obtain a housing of said material having a side wall and an end wall which define a reservoir; and
- forming an array of apertures through the end wall in open communication with the reservoir to form an emitter-dispenser surface.
- Preferably, the step of coating is by chemical vapor deposition and the coating material is tungsten.
- After some additional machining the mandrel is removed such as by etching it away, thereby leaving the hollow housing of tungsten which will serve as a reservoir for an activating material. This housing then has an array of apertures drilled in the top surface such as by a pulsed laser thereby creating a controlled porosity emitter-dispenser surface.
- At this time, the reservoir of the structure can be filled from the open end with a barium calcium aluminate compound or other barium bearing compound that will decompose when heated, thereby supplying activating material to the emitter-dispenser surface through the array of apertures.
- The filled housing can then be attached to a heater structure to make a complete dispenser cathode.
- This housing is featured in that it is constructed of a single material wherein the crystalline-atomic bonding of the top surface and the side walls of the housing forms an essentially monolithic or single piece. Several advantages include control over the crystalline orientation in the top surface member which becomes the emitter-dispenser surface and the fact that there is little likelihood of contaminates forming on the emission-dispenser surface during fabrication. Consequently, the work function of the surface is generally uniform whereupon there is a high degree of emission uniformity across this surface.
- Another advantage is that the dispenser cathode can be operated at a lower temperature than other dispenser cathodes of the controlled porosity type as a result of the feature of the support-thermal cross members which tend to distribute the heat more deeply and uniformly into the activating material and to the emitter-dispenser surface. As a consequence, it is able to produce a higher emission density for a given temperature than was heretofore obtained and a more stable emission at these lower temperatures. Moreover, at these lower temperatures there is a lower evaporation rate thereby resulting in a reduced loss of the activating material barium and barium oxide (Ba + BO).
- Still another advantage is that the structure is not likely to delaminate or fail during thermal cycling as a result of its unitary and single material construction.
- In addition, there is dimensional stability and lack of distortion in the emitter-dispenser surface which might otherwise result from thermal cycling.
- The process and structure has the added manufacturing advantages that it: reduces the number of manufacturing steps; reduces the hand work required; is suitable for large scale production; allows very thin wall structures to be readily fabricated; and results in an easily replicated, precision structure.
- Further purposes and advantages of this invention will become apparent from the study of the following detailed description, the attached drawings and the claims.
- A preferred embodiment of the invention will now be described by way of example, with reference to the accompanying drawings, in which:-
- FIG. 1 is a schematic perspective view of a mandrel onto which a thin layer of tungsten or other metal to be coated.
- FIG. 2 is a schematic perspective view illustrating the cross member thermal-mechanical support brazed in place in the mandrel.
- FIG. 3 is a schematic perspective view illustrating the mandrel machined to a configuration for chemical vapor deposition.
- FIG. 4 is a cross-sectional side view taken along the line 4-4 of FIG. 3 showing the mandrel having a thin layer of metal deposited thereon.
- FIG. 5 is a cross-sectional view with the mandrel end surface contoured in a spherical radius, concave configuration.
- FIG. 6 is a cross-sectional view illustrating a second thin layer of metal deposited thereon to form the emitter-dispenser surface and to thicken the side wall of the emitter-reservoir housing.
- FIG. 7 is a cross-sectional view of the hollow emitter-reservoir housing with the mandrel removed.
- FIG. 8 is a cross-sectional view representing the housing of FIG. 7 with the emitter-dispenser surface thereof drilled to form an array of apertures.
- FIG. 9 is a cross-sectional schematic illustration of a control porosity dispenser cathode including the housing filled with activating material and a heater assembly attached thereto.
- Referring now to the drawings in more detail, FIG. 1 is illustrative of a first step of fabrication in which a mandrel is formed having a configuration generally similar to the configuration of the final emitter-reservoir housing. In this particular embodiment, the
mandrel 20 is cylindrical and is made of molybdenum. It should be understood that the mandrel could be made of other materials which are capable of withstanding the temperatures at which the subsequent fabrication steps take place and which are otherwise compatible with these steps. - The
end face 22 of themandrel 20 is slotted with twointersecting slots slots - As illustrated in FIG. 2, intersecting
strips slots strips copper brazing material 32. - Thereafter, as illustrated by FIG. 3, the
mandrel 20 is machined down to remove thesurplus brazing material 32 and the edges of thestrips mandrel 20 so that the strip edges are flush with the surface of the mandrel. In addition, in this particular embodiment, ashoulder 34 is formed. - As illustrated by FIG. 4, the
mandrel 20 is subjected to chemical vapor deposition process in which a tungsten coating 36 (not drawn to scale) 0.1016 mm (0.004 of an inch) thick is formed on the mandrel surface. During this chemical vapor deposition step, the edges of thestrips tungsten coating 36. - This vapor deposition step can be accomplished in a quartz reaction chamber in which reactive gases of the tungsten metal compound will flow across the heated mandrel to form the deposited layer. Generally the heat for the mandrel can be supplied by an inductive type power supply and the flow rate of the gases can be controlled.
- Thereafter, as illustrated by FIG. 5,
end surface 22 of the mandrel is machined into a spherical- radiusconcave surface 38 such as by electrical discharge machining. The particular radius and shape of thissurface 38 is dependent upon the end application of the cathode and the type of beam focusing to be used. Thus, thissurface 38 could have been left flat or have other configurations for certain types of applications and beam focusing. - As illustrated by FIG. 6, another thin layer of
tungsten 40 is formed upon the exposed surface of thefirst tungsten coating 36 and the exposed mandrelconcave surface 38 by means of the chemical vapor deposition process. The term "thin" as used herein is about 0.0254 mm (0.001 of an inch) thick in the preferred embodiment. However, it could also be somewhat less or somewhat greater depending upon the structural integrity of the layer or upon the ease at which the electron emitting material is to migrate to the emitting surface. For example, the range could be between about 0.0127 mm (0.0005 of an inch) and 0.127 mm (0.005 of an inch) or, in some cases, more. Care must be taken to be sure that this layer is not so thin that the activating material will readily evaporate or so thick that the activating material will not readily migrate to the emitter surface through the pores to be formed. - During the vapor deposition, the two layers of
tungsten dispenser 42 atomically bonds to the exposed edges of thestrips dispenser 42 in its precise configuration and will subsequently serve to distribute heat into an activating material as well as to the emitter surface. - As illustrated by FIG. 7, the end segment of the
mandrel 20 holding the configured tungsten coating is cut off at about a plane coextensive with the lower edges ofstrips molybdenum mandrel 20 is removed such as by a differential solvent thereby forming a hollow housing with areservoir 44 formed therein. One differential solvent which has been found to be effective is nitric acid which etches the molybdenum and any remainingcopper brazing material 32 but does not significantly affect the tungsten. - Of course, if, as previously stated, other materials are used for the
mandrel 20, or thehousing 48, it may be necessary to use another differential solvent. In addition, it would be possible to configure themandrel 20 such that it can be readily withdrawn from the assembled housing. One way that this could be accomplished would be by tapering the side wall of the mandrel and coating it with graphite thereby enabling the mandrel to be easily withdrawn. Moreover, there are other possible approaches that can be used. - As illustrated by FIG. 8, an array of
apertures 46 is formed through the emitter-dispenser 42 in open communication with thereservoir 44. It is preferable that these apertures be of small diameter, closely spaced and in a precise pattern. Accordingly, one way that these apertures have been formed is by laser drilling in which apertures 5.0 microns in diameter on centers spaced 15.0 microns apart have been formed. This results in a controlled porosity emitter-dispenser 42. - Thereafter, as further illustrated in FIG. 9 the
reservoir 44 of the hollow emitter-dispenser housing 48 is filled with an activatingmaterial 50 through the open end thereof. One activatingmaterial 50 which has been found to be particularly useful is a mixture of 80% by weight of barium calcium aluminate having a 5:3:2 mole ratio and 20% by weight of tungsten powder. Of course, other barium bearing compounds that will decompose when heated to supply activating material to the emitter surface of the emitter-dispenser 42 can be used. - As further illustrated in FIG. 9, a controlled ' porosity dispenser cathode is formed by attaching the filled emitter-
dispenser housing 48 to aheater assembly 54. - The
heater assembly 54 includes ahollow support member 56 made of a high temperature resistant material such as tungsten which encloses aheater coil 58 potted in a thermallyconductive material 60 such as aluminum oxide AI203. The emitter-reservoir housing 48 is affixed to the end thereof such as by brazing. Thereafter, heat from theheater coil 58 is conducted to the activatingmaterial 50 thereby causing barium and barium oxide to migrate both along the interspace between the emitter-dispenser 42 and the activatingmaterial 50 and directly through theapertures 46 to the emitter surface of the emitter-dispenser 42 thereby continuously replenishing the activating material on the surface as it is used up during electron emission. As previously stated, thestrips material 50 and to the emitter surface thereby providing for efficient operation of the overall device.
Claims (9)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US43358682A | 1982-10-12 | 1982-10-12 | |
US433586 | 1982-10-12 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0121564A1 EP0121564A1 (en) | 1984-10-17 |
EP0121564B1 true EP0121564B1 (en) | 1987-11-25 |
Family
ID=23720698
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP83903655A Expired EP0121564B1 (en) | 1982-10-12 | 1983-10-06 | Method for fabricating a dispenser-reservoir housing for a dispenser cathode |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP0121564B1 (en) |
JP (1) | JPS59501887A (en) |
DE (1) | DE3374738D1 (en) |
IL (1) | IL69936A (en) |
IT (1) | IT1172332B (en) |
WO (1) | WO1984001664A1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
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KR920004900B1 (en) * | 1990-03-13 | 1992-06-22 | 삼성전관 주식회사 | Impregnated type cathode body and manufacturing the same |
US7215070B2 (en) * | 2003-02-14 | 2007-05-08 | Mapper Lithography Ip B.V. | System, method and apparatus for multi-beam lithography including a dispenser cathode for homogeneous electron emission |
US9056432B2 (en) * | 2012-04-25 | 2015-06-16 | Johnson & Johnson Vision Care, Inc. | High-density mask for three-dimensional substrates and methods for making the same |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1078606A (en) * | 1953-04-02 | 1954-11-19 | Csf | Improvements to emissive cathodes |
US2931934A (en) * | 1955-02-05 | 1960-04-05 | Egyesuelt Izzolampa | Indirectly heated supply cathode |
BE550302A (en) * | 1955-08-15 | |||
JPS50150357A (en) * | 1974-05-21 | 1975-12-02 | ||
US4310603A (en) * | 1978-11-30 | 1982-01-12 | Varian Associates, Inc. | Dispenser cathode |
GB2100502B (en) * | 1978-11-30 | 1983-08-03 | Varian Associates | Dispenser cathodes |
US4379979A (en) * | 1981-02-06 | 1983-04-12 | The United States Of America As Represented By The Secretary Of The Navy | Controlled porosity sheet for thermionic dispenser cathode and method of manufacture |
-
1983
- 1983-10-06 WO PCT/US1983/001572 patent/WO1984001664A1/en active IP Right Grant
- 1983-10-06 DE DE8383903655T patent/DE3374738D1/en not_active Expired
- 1983-10-06 JP JP58503485A patent/JPS59501887A/en active Pending
- 1983-10-06 EP EP83903655A patent/EP0121564B1/en not_active Expired
- 1983-10-09 IL IL69936A patent/IL69936A/en not_active IP Right Cessation
- 1983-10-10 IT IT49128/83A patent/IT1172332B/en active
Also Published As
Publication number | Publication date |
---|---|
JPS59501887A (en) | 1984-11-08 |
EP0121564A1 (en) | 1984-10-17 |
IT8349128A0 (en) | 1983-10-10 |
IL69936A (en) | 1988-02-29 |
DE3374738D1 (en) | 1988-01-07 |
IT1172332B (en) | 1987-06-18 |
WO1984001664A1 (en) | 1984-04-26 |
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