US3401297A - Thermionic cathodes for electron discharge devices with improved refractory metal heater wires - Google Patents
Thermionic cathodes for electron discharge devices with improved refractory metal heater wires Download PDFInfo
- Publication number
- US3401297A US3401297A US481818A US48181865A US3401297A US 3401297 A US3401297 A US 3401297A US 481818 A US481818 A US 481818A US 48181865 A US48181865 A US 48181865A US 3401297 A US3401297 A US 3401297A
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- US
- United States
- Prior art keywords
- refractory metal
- heater
- heater wire
- thermionic
- refractory
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- 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 - Lifetime
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- 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
- H01J1/22—Heaters
Definitions
- the present invention provides tube and cathode designers with improved refractory metal heater wires and improved thermionic cathodes by the utilization of a plurality of minute refractory metal particles on the heater wire itself either in a bare or non-insulated case or in a coated or refractory insulated type of heater wire.
- the improved heater wire operates at a reduction in heater wire operating temperature for a given input power and hence increased longevity and emissivity for the heaters.
- the roughened surface of the heater wire enhances the adherence of the refractory insulation coating on the heater wire.
- This invention relates in general to electron discharge devices, and more particularly to improved thermionic cathodes incorporating refractory metal heater wires having a plurality of refractory metal particles disposed thereon.
- thermionic emission portion thereof Of particular interest to designers of electron discharge devices such as pentodes, triodes, klystrons, traveling wave tubes, etc. is the thermionic emission portion thereof and in particular the cathode assembly which may be of any of the conventional types such as dispenser cathodes, oxide cathode, etc., generic to each of which is the incorporation therein of a refractory metal heater wire element utilized to initiate thermionic emission from the electron emission surface thereof.
- the present invention provides tube and cathode designers with improved refractory metal heater wires and improved thermionic cathodes by the utilization of a plurality of minute refractory metal particles on exterior surface on the heater wire itself either in a bare or noninsulated case or in a coated or refractory insulated type of heater wire.
- the advantages to be derived from the utilization of the teachings of the present invention with regard to providing a plurality of minute refractory metal particles on the heater wire surface in a bare or noninsulated heater type are reduction in heater wire operating temperature for a given input power and hence increased longevity and emissivity for such bare heaters.
- the present invention particularly teaches the application of minute refractory metal particles on a bare or as received heater wire as a preferred means of roughening the heater wire to achieve the aforementioned beneficial advantages in both noninsulated and insulated cases.
- a feature of the present invention is the provision of a thermionic cathode incorporating a refractory metal heater wire having a plurality of refractory metal particles deposited on the bare wire surface.
- Another feature of the present invention is the provision of a novel thermionic cathode heater assembly and method of making the same wherein the refractory metal heater wipe is coated with a plurality of refractory metal partic es.
- Another feature of the present invention is the provision of a novel thermionic cathode heater assembly and method of making the same wherein a refractory metal heater wire is coated with a plurality of refractory metal particles which in turn are provided with a refractory insulation coating.
- FIG. 1 is a fragmentary cross-sectional view partly in elevation depicting an electron discharge device of the klystron type incorporating the improved thermionic cathode of the present invention.
- FIG. 2 is a cross-sectional view partly in elevation of the thermionic cathode embodied in the device of FIG. 1 taken along the lines 2-2 in the direction of the arrows.
- FIG. 3 is a cross-sectional view of an enlarged refractory metal heater wire having a plurality of minute refractory metal particles deposited thereon according to the teaching of the present invention.
- FIG. 4 is an enlarged cross-sectional view partly in elevation of the improved refractory insulation coated refractory metal heater shown in FIG. 2 taken along the lines 44 in the direction of the arrows.
- FIG. 5 is an illustrative graphical portrayal depicting input power vs. temperature for a bare as received refractory metal heater relative to a bare refractory metal heater having a plurality of refractory metal particles deposited thereon.
- FIG. 1 there is depicted an electron discharge device 6 of the klystron type incorporating a thermionic cathode which incorporates the teachings of the present invention.
- the klystron 6, depicted in FIG. 1 is of a conventional reflex type incorporating a standard refiector assembly 7 disposed at the downstream end portion thereof and mounted on a main body block 8 which incorporates a thermionic cathode assembly 9 at the upstream end portion thereof.
- a conventional tuner mechanism 10 is utilized to vary the resonant frequency of re-entrant cavity 11 in a manner well known in the art.
- Electromagnetic wave energy is extracted via output waveguide 12 through an alumina or the like dielectric vacuum sealed window assembly 13.
- For the particular details of such a high frequency electron discharge device see US. Patent No. 3,097,323 by F. L. Salisbury issued July 9, 1963 and assigned to the same assignee as the present invention.
- FIG. 2 there is shown in cross-sectional view partly in elevation a thermionic cathode assembly 9 depicted in the exemplary electron discharge device 6 of FIG. 1.
- the thermionic cathode assembly 9 depicted in FIG. 2 is of the type which is generically known as the oxide cathode and is utilized as a representative example of conventional thermionic cathodes utilizing refractory metal heater wires such as the impregnated dispenser cathode.
- Thermionic cathodes such as the oxide cathode 9 incorporate an electron emission surface 16 disposed in heat transfer relationship with respect to a refractory metal heater wire such as the coated wire 17 dipsosed within any suitable tubular refractory metal mounting member 18.
- the insulated or coated refractory metal heater 17 depicted in FIG. 2 is preferably of tungsten Wire 19 and can also be made of rhenium and rhenium-tungsten alloys.
- the tungsten heater wire 19 is provided with a coating of a plurality of minute refractory metal para ticles 20 as best seen in FIGS. 3 and 4, and in the in sulated or coated type of heater an exterior refractory insulation coating of alumina (A1 is provided thereon.
- Separate mounting means may be utilized to support the refractory metal heater within the support sleeve 13.
- the coated heater wire 17 when provided with an intermediate layer composed of a plurality of refractory metal particles such as tungsten, molybdenum or rhenium as shown best in FIGS. 3 and 4 has been found to result in several mechanical and thermal advantages in comparison to prior art thermionic heaters incorporating an alumina or the like refractory insulation coating on a bare or as received heater.
- FIG. 5 an illustrative graphical portrayal of the thermal emissivity improvements and enhanced or reduced operating temperature improvements achieved by the deposition of a plurality of refractory metal particles on a refractory metal heater is depicted.
- Curve A represents a simple coiled tungsten heater without the refractory metal particles deposited thereon having a wire diameter of approximately .006 inch
- Curve B represents a similar tungsten wire provided with a plurality of tungsten particles having approximately 1 micron diameters and total thickness of approximately .0005 inch to .001 inch deposited thereon.
- Acceptable results can be obtained with thicknesses which are less than .0005 inch, such as .0003 inch although we have found the aforementioned range to produce good results.
- both heaters were positioned in a Bell jar and optical pyrometer readings were taken for various input powers.
- the significant reduction in optical pyrometer or brightness temperature for the roughened heater represented by Curve B in comparison with the unroughened or bare heater represented by Curve A are self-evident.
- heater wire life is increased correspondingly and the thermal emissivity characteristics thereof are enhanced correspondingly.
- lybdenum, or an alloy thereof, to a tungsten or rhenium or an alloy thereof refractory metal heater are the followmg:
- a simple dipping process wherein the bare refractory metal heater is dipped into a solution of tungsten powder, xylene and methacrylate may be used.
- the bare wire is dipped a sufficient number of times so as to completely cover the outer surface thereof in the same manner as taught in co-pending US. application Ser. No. 340,478, by Paul W. Camenzind filed J an. 27, 1964, and assigned to the same assignee as the present invention.
- the proportions of tungsten powder and xylene in the solution are not critical.
- the percentage by weight of methacrylate solution should be preferably between 0.1%5% preferably substantially 0.3%.
- the percentage of tungsten powder can be between 35 and 75 percent by weight, the balance of the solution being made up of xylene.
- the percentage of tungsten powder is preferably in the order of 60% by weight.
- the tungsten particles are preferably around one micron average diameter and preferably are less than 200 mesh for optimum results.
- the coated bare heater wire is fired in a controlled inert or reducing atmosphere such as a hydrogen furnace at around 1500 C. for approximately 1 minute after which the heater has been found ready for utilization.
- the suspension for cataphoretic coating includes around 12 grams tungsten powder made by the Wah-Chang Company (denoted as Wah-Chang grade C-3); approximately 0.4 gram of yttrium nitrate approximately 0.6 gram of H 0; approximately cc. of methanol and an additional 0.1 gram of aluminum nitrate Al(NO .9I-I O with an applied DC potential of around 50 volts in a deposition chamber.
- Wah-Chang Company denoted as Wah-Chang grade C-3
- approximately cc. of methanol approximately cc. of methanol and an additional 0.1 gram of aluminum nitrate Al(NO .9I-I O with an applied DC potential of around 50 volts in a deposition chamber.
- the above parameters have been found quite satisfactory for achieving good particle coatings in approximately 4 to 5 seconds.
- the tungsten heater is the cathode; the anode is made of aluminum. Agitation is used to keep the particles in suspension. A coating thickness ranging from .0005 inch to .001 inch is achieved.
- the coating is sin-tered such as by firing in around 1650" C. for approximately 30 minutes in a wet disassociated ammonia atmosphere. Good results have also been achieved by redipping the sintered roughened refractory metal heaters into a solution of approximately 4 grams of H WO in 25 cc. of concentrated NH OH, dried, and refired at around 1650 C. with the objective of achieving further consolidation of the coating such as to improve the resistance to flaking as well as the adherence of the particles both to each other and to the bare refractory metal heater wire.
- the refractory insulation coating is then applied for coated heaters.
- This refractory insulation coating has a thickness for cataphoretically deposited alumina of preferably between .002 and .003 inch and for CVD alumina of preferably between .001 and .002 inch.
- a suitable catap-horetic deposition method for alumina can be found in the following work, The Oxide Coated Cathode by G. Herrmann, and S. Wagener, vol. 1, Chapman and Hall, Ltd., 1951, particularly pages 43 to 53.
- a suitable method for chemically vapor depositing alumina on the roughened tungsten heater wire can be found in the following article, The Deposition of Oxide on Silicon by the Reaction of a Metal Halide With a Hydrogen-Carbon Dioxide Mixture by S. K. Tung and R. E. Caffrey, Transactions of the Metallurgical Society of AIME, pages 572577, vol. 233, March 1965.
- the coated heater wire itself is snugly fitted within a refractory metal support tube such as a nickel tube 18 shown in FIG. 2, thermal conduction as well as thermal radiation heating is employed for transferring heat from the heater wire to the nickel cathode button 15. Since radiation emissivity characteristics of the bare heater wire are extremely important the transfer of ratdiant energy from the coated heater to the back or the absorption side of the button is extremely important and it is also very important that the heater not be shorted out such as might occur if flaking and cracking of the alumina coating occurred in use. In both the cataphoretic and CVD deposited cases wherein an intermediate roughened layer was utilized as shown in FIG.
- a thermionic cathode assembly for electron discharge devices including a cathode mounting sleeve, a thermionic cathode mounted on said cathode mounting sleeve, a refractory metal heater wire disposed within said cathode mounting sleeve in a heat transfer relationship with respect to said thermionic cathode, and means to roughen the surface of said heater Wire and to improve the radiation of heat therefrom, said means comprising a plurality of minute refractory metal particles bonded to said surface, adjacent ones of said particles being in mutually contacting relationship whereby said heater wire operating temperature is lowered in use and whereby said heater wire emissivity is enhanced in use.
- the thermionic cathode assembly defined in claim 1 including a refractory insulation coating disposed about said heater wire having said plurality of minute refractory metal particles bonded thereto whereby a refractory insulation coated refractory metal heater is achieved.
- a thermionic cathode assembly for utilization in electron discharge devices including a thermionic cathode mounting sleeve, a thermionic cathode mounted on said mounted sleeve, a refractory metal heater wire of tungsten disposed within said cathode mounting sleeve in heat transfer relationship with respect to said thermionic cathode, said tungsten heater Wire having a layer of minute tungsten particles disposed on the surface thereof and forming a particle coating thereon whereby said heater Wire surface is roughened, adjacent ones of said particles being in mutual-1y contacting relationship and a layer of refractory insulation material over said layer of minute tungsten particles.
- a thermionic cathode assembly for utilization in electron devices including a cathode mounting member, a thermionic cathode mounted on said cathode mounting member, a refractory insulation coated refractory metal heater wire disposed within said cathode mounting member in heat transfer relationship with respect to said thermionic cathode, said refractory insulation coated thermionic heater wire including a refractory metal core made of a metal selected from the group consisting of tungsten and rhenium and alloys thereof, and an intermediate layer of particles of material selected from the group consisting of tungsten, rhenium, molybdenum and alloys thereof, adjacent ones of said particles being in mutually contacting relationship and an exterior layer of refractory insulation material disposed on said intermediate particle coating, said refractory insulation coating being made of alumina.
- a thermionic cathode assembly for utilization in electron discharge devices including a nickel cathode button, said nickel cathode button having a thermionic emissive material disposed thereon, a nickel tubular support sleeve bonded to said nickel button, a coiled tungsten heater wire disposed within said nickel support sleeve and intimately contacting the internal surface of said nickel support sleeve, said coiled tungsten heater wire being provided with a plurality of minute tungsten particles disposed in a layer on the bare heater Wire surface, adjacent ones of said particles being in mutually contacting relationship and an alumina refractory insulation coating disposed in intimate contact and surrounding said particle coated heater Wire.
- a thermionic cathode assembly for utilization in high frequency electron discharge devices including a hollow tubular cathode mounting sleeve, a cathode electron emission surface disposed on said sleeve, a refractory metal heater wire disposed within said sleeve in heat transfer relationship With respect to said cathode electron emission surface, said refractory metal heater Wire having a roughened surface composed of a layer of minute refractory metal particles sintered on the heater wire, adjacent ones of said particles being in mutually contacting relationship said plurality of minute refractory metal particles having average diameters of less than 200 mesh, and a refractory insulation coating disposed on said particles whereby an insulation coated heater Wire is formed.
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- Solid Thermionic Cathode (AREA)
- Electrodes For Cathode-Ray Tubes (AREA)
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US481818A US3401297A (en) | 1965-08-23 | 1965-08-23 | Thermionic cathodes for electron discharge devices with improved refractory metal heater wires |
GB37325/66A GB1142728A (en) | 1965-08-23 | 1966-08-19 | Improved thermionic cathodes for electron discharge devices |
DE1589024A DE1589024B2 (de) | 1965-08-23 | 1966-08-19 | Verfahren zum Herstellen eines Heizdrahtes fur eine Glühkathode |
FR73702A FR1490147A (fr) | 1965-08-23 | 1966-08-22 | Cathode thermoionique améliorée pour systèmes à décharge électronique |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US481818A US3401297A (en) | 1965-08-23 | 1965-08-23 | Thermionic cathodes for electron discharge devices with improved refractory metal heater wires |
Publications (1)
Publication Number | Publication Date |
---|---|
US3401297A true US3401297A (en) | 1968-09-10 |
Family
ID=23913509
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US481818A Expired - Lifetime US3401297A (en) | 1965-08-23 | 1965-08-23 | Thermionic cathodes for electron discharge devices with improved refractory metal heater wires |
Country Status (3)
Country | Link |
---|---|
US (1) | US3401297A (de) |
DE (1) | DE1589024B2 (de) |
GB (1) | GB1142728A (de) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3553521A (en) * | 1967-02-17 | 1971-01-05 | Philips Corp | Indirectly heated cathode for an electron discharge tube with an insulated heating element |
US3808043A (en) * | 1972-05-30 | 1974-04-30 | Rca Corp | Method of fabricating a dark heater |
US3852105A (en) * | 1972-04-07 | 1974-12-03 | Rca Corp | Fabrication of dark heaters |
US3902093A (en) * | 1973-04-06 | 1975-08-26 | Int Standard Electric Corp | Cathode heater element with a dark heat radiating coating and method of producing such |
US3936532A (en) * | 1974-02-08 | 1976-02-03 | Oregon Graduate Center For Study And Research | Activation of thin wire emitters for field ionization/field desorption mass spectrometry |
US4126489A (en) * | 1973-07-17 | 1978-11-21 | Varian Associates, Inc. | Method of making cathode heaters |
US5041041A (en) * | 1986-12-22 | 1991-08-20 | Gte Products Corporation | Method of fabricating a composite lamp filament |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3029360A (en) * | 1958-04-29 | 1962-04-10 | Rca Corp | Heater wire coating process |
US3161540A (en) * | 1962-06-20 | 1964-12-15 | Sylvania Electric Prod | Process of manufacturing insulated heater wire and article |
US3195004A (en) * | 1960-08-19 | 1965-07-13 | Rca Corp | Cathode heater for electron discharge devices |
US3227911A (en) * | 1963-10-24 | 1966-01-04 | Eitel Mccullough Inc | Indirectly heated cathodes |
US3268305A (en) * | 1964-08-17 | 1966-08-23 | Sylvania Electric Prod | Composite wire |
US3328201A (en) * | 1964-04-27 | 1967-06-27 | Rca Corp | Heater for electron tubes |
-
1965
- 1965-08-23 US US481818A patent/US3401297A/en not_active Expired - Lifetime
-
1966
- 1966-08-19 GB GB37325/66A patent/GB1142728A/en not_active Expired
- 1966-08-19 DE DE1589024A patent/DE1589024B2/de not_active Ceased
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3029360A (en) * | 1958-04-29 | 1962-04-10 | Rca Corp | Heater wire coating process |
US3195004A (en) * | 1960-08-19 | 1965-07-13 | Rca Corp | Cathode heater for electron discharge devices |
US3161540A (en) * | 1962-06-20 | 1964-12-15 | Sylvania Electric Prod | Process of manufacturing insulated heater wire and article |
US3227911A (en) * | 1963-10-24 | 1966-01-04 | Eitel Mccullough Inc | Indirectly heated cathodes |
US3328201A (en) * | 1964-04-27 | 1967-06-27 | Rca Corp | Heater for electron tubes |
US3268305A (en) * | 1964-08-17 | 1966-08-23 | Sylvania Electric Prod | Composite wire |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3553521A (en) * | 1967-02-17 | 1971-01-05 | Philips Corp | Indirectly heated cathode for an electron discharge tube with an insulated heating element |
US3852105A (en) * | 1972-04-07 | 1974-12-03 | Rca Corp | Fabrication of dark heaters |
US3808043A (en) * | 1972-05-30 | 1974-04-30 | Rca Corp | Method of fabricating a dark heater |
US3902093A (en) * | 1973-04-06 | 1975-08-26 | Int Standard Electric Corp | Cathode heater element with a dark heat radiating coating and method of producing such |
US4126489A (en) * | 1973-07-17 | 1978-11-21 | Varian Associates, Inc. | Method of making cathode heaters |
US3936532A (en) * | 1974-02-08 | 1976-02-03 | Oregon Graduate Center For Study And Research | Activation of thin wire emitters for field ionization/field desorption mass spectrometry |
US5041041A (en) * | 1986-12-22 | 1991-08-20 | Gte Products Corporation | Method of fabricating a composite lamp filament |
Also Published As
Publication number | Publication date |
---|---|
DE1589024B2 (de) | 1975-04-30 |
GB1142728A (en) | 1969-02-12 |
DE1589024A1 (de) | 1970-03-19 |
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