US2864028A - Thermionic dispenser cathode - Google Patents

Thermionic dispenser cathode Download PDF

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Publication number
US2864028A
US2864028A US528296A US52829655A US2864028A US 2864028 A US2864028 A US 2864028A US 528296 A US528296 A US 528296A US 52829655 A US52829655 A US 52829655A US 2864028 A US2864028 A US 2864028A
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US
United States
Prior art keywords
strips
molybdenum
cathode
barium
pores
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 - Lifetime
Application number
US528296A
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English (en)
Inventor
Patrick P Coppola
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
US Philips Corp
North American Philips Co Inc
Original Assignee
US Philips Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority to BE550302D priority Critical patent/BE550302A/xx
Application filed by US Philips Corp filed Critical US Philips Corp
Priority to US528296A priority patent/US2864028A/en
Priority to GB24558/56A priority patent/GB800219A/en
Priority to DEN12600A priority patent/DE1047321B/de
Priority to CH344139D priority patent/CH344139A/de
Priority to FR1173168D priority patent/FR1173168A/fr
Application granted granted Critical
Publication of US2864028A publication Critical patent/US2864028A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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

Definitions

  • My invention relates to a thermionic dispenser cathode.
  • my invention relates to an improvement n a thermionic dispenser cathode of the type disclosed in U. S. Patent No. 2,700,118 to R. C. Hughes et al.
  • the cathode comprises a pressed and sintered mixture of a refractory metal such as tungsten, molybdenum, tantalum, hafnium or alloys of those metals and an alkaline earth material which reacts with the refractory metal upon heating to furnish alkaline earth metal to an emissive surface of the cathode.
  • alkaline earth materials fused mixtures of an alkalineearth oxide and an acid forming oxide are disclosed which react with the refractory metal to furnish alkaline earth metal, e. g. barium, to the emissive surface of the cathode.
  • alkaline earth metal e. g. barium
  • alkaline earth material is distributed throughout a porous body of refractory metal during operation of the cathode some alkaline earth metal or oxides, or both, are volatilized because of their low vapor pressure in vacuum.
  • the evaporation of alkaline earth metal or oxides, or both, is of course, generally undesirable because those products may be deposited on other electrodes of an electron-discharge tube where they give rise to secondary emission.
  • a further object of my invention is to provide a dispenser cathode having a high emissivity and a low rate of evaporation of alkaline earth metal oxides, or both.
  • a non-porous member of refractory metal such as molybdenum
  • the spacing between apertures in the non-porous covering member preferably should not exceed the migration distance of the alkaline earth metal over the refractory metal surface in order that maximum surface cov- 2,864,028 Patented Dec. 9,1958
  • This migration distance will depend upon :a .number of factors including the particular alkaline earth metal being supplied to the surface, the operating temperature of the cathode, and the refractory metal. For example,
  • the migration length of Ba or BaO, or both, on molybdenum is about 0.3 mmpwhile at 900 C brightness the distance increases to 0.6 mm.
  • a source of barium is provided in the pores of the cathode and molybdenum strips or wires are embedded in the emissive surface. These strips or wires are spaced sufficiently far apart, e. g. at least 0.5 mm., to assure substantially full surface coverage of barium during operation of the cathode.
  • Fig. 1 is an elevational view in section of a cathode according to the invention
  • Fig. 2 is a top view of the cathode showing the emissive surface
  • Fig. 3 is a top view of another embodiment of another cathode showing the emissive surface.
  • the cathode shown in Fig. 1 comprises an emissive wafer I mounted at one end of a molybdenum sleeve 2 which houses a heater 3. Embedded in the emissive surface of the wafer are strips 4 which form a grid-like structure shown in Fig. 2.
  • the emissive wafer comprises a pressed and sintered body of about 90% by weight of a 25% tungsten to molybdenum alloy and the balance, distributed throughout the pores of the body, a fused mixture of about 5 moles of barium oxide and 2 moles of aluminum oxide.
  • strips or wires of molybdenum Prior to the pressing operation, strips or wires of molybdenum having a diameter of about .3 mm. are placed on top of the powder about .5 mm. apart.
  • the mixture is pressed and sintered at 1370 C. brightness for about 20 minutes and then rapidly raised to the melting point of the fused oxides (about 1650 C. to 1750 C.).
  • the molybdenum strips are, therefore, integrally united with the sintered body and provide zones in which the surface pores are completely closed. Thus, those zones contribute no barium metal to the surface but barium metal which is supplied to the surface by the pores in the exposed areas migrates over the molybdenum strips and thereby contributes to the emission from the surface
  • I may use a molybdenum plate 5, having a number of suitably spaced apertures 6 covering a substantial portion of the emissive wafer 1.
  • the molybdenum plate may be sintered to the emissive water 1 or may be welded to the molybdenum sleeve 2 at the tips of the cusps 7.
  • the covered portions of the wafer are supplied with barium through the apertures in the plate.
  • the apertures are suitably spaced so that substantially full surface coverage can be maintained at all times by the migration of barium over the surface.
  • a dispenser cathode comprising a porous sintered tungsten body, a supply of a fused mixture of barium oxide and aluminum oxide containing a molar excess of barium oxide within the pores of said body, and a plurality of spaced apart molybdenum strips embedded in a 3 surface of the body constituting the emissive surface of that body, said strips being integrally united with the sintered body to provide zones in which surface pores are completely closed, said strips having a width not substantially exceeding the migration distance of barium over molybdenum.
  • a dispenser cathode comprising a porous sintered body of an alloy of molybdenum and tungsten, a supply of a fused mixture of barium oxide and aluminum oxide containing a molar excess of barium oxide within the pores of said body, and a plurality of spaced apart molybdenum strips embedded in a surface of that body constituting the emissive surface of the body, said strips being integrally united with the sintered body to provide zones in which surface pores are completely closed, said strips having a width not substantially exceeding the migration distance of barium over molybdenum.
  • a dispenser cathode comprising a poroussintered body of an alloy of about 75% of molybdenum and about 25% tungsten, a supply of a fused mixture of about 5 moles of barium oxide and 2 moles of aluminum oxide Within the pores of said body, a plurality of spaced apart molybdenum strips embedded in a surface of the body constituting the emissive surface of the body, said strips being integrally united with the sintered body to provide zones in which surface pores are completely closed, said strips having a width not substantially exceeding the migration distance of barium over molybdenum.

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  • Solid Thermionic Cathode (AREA)
US528296A 1955-08-15 1955-08-15 Thermionic dispenser cathode Expired - Lifetime US2864028A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
BE550302D BE550302A (enrdf_load_stackoverflow) 1955-08-15
US528296A US2864028A (en) 1955-08-15 1955-08-15 Thermionic dispenser cathode
GB24558/56A GB800219A (en) 1955-08-15 1956-08-10 Improvements in or relating to cathodes of the dispenser type
DEN12600A DE1047321B (de) 1955-08-15 1956-08-11 Vorratskathode mit einem poroesen Koerper, in dem oder hinter dem Erdalkalimetallverbindungen angebracht sind
CH344139D CH344139A (de) 1955-08-15 1956-08-13 Vorratskathode für elektrische Entladungsröhren
FR1173168D FR1173168A (fr) 1955-08-15 1956-08-14 Cathode à réserve et tube à décharge muni d'une telle cathode

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US528296A US2864028A (en) 1955-08-15 1955-08-15 Thermionic dispenser cathode

Publications (1)

Publication Number Publication Date
US2864028A true US2864028A (en) 1958-12-09

Family

ID=24105076

Family Applications (1)

Application Number Title Priority Date Filing Date
US528296A Expired - Lifetime US2864028A (en) 1955-08-15 1955-08-15 Thermionic dispenser cathode

Country Status (6)

Country Link
US (1) US2864028A (enrdf_load_stackoverflow)
BE (1) BE550302A (enrdf_load_stackoverflow)
CH (1) CH344139A (enrdf_load_stackoverflow)
DE (1) DE1047321B (enrdf_load_stackoverflow)
FR (1) FR1173168A (enrdf_load_stackoverflow)
GB (1) GB800219A (enrdf_load_stackoverflow)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3102329A (en) * 1958-12-12 1963-09-03 Varta Ag Sinter electrode
US3113236A (en) * 1959-06-23 1963-12-03 Philips Corp Oxide dispenser type cathode
US3176180A (en) * 1961-09-01 1965-03-30 Gen Electric Dispenser cathode
US3594885A (en) * 1969-06-16 1971-07-27 Varian Associates Method for fabricating a dimpled concave dispenser cathode incorporating a grid
US4101800A (en) * 1977-07-06 1978-07-18 The United States Of America As Represented By The Secretary Of The Navy Controlled-porosity dispenser cathode
US4147954A (en) * 1976-07-10 1979-04-03 E M I-Varian Limited Thermionic electron emitter
US4393328A (en) * 1979-11-09 1983-07-12 Thomson-Csf Hot cathode, its production process and electron tube incorporating such a cathode
WO1984001664A1 (en) * 1982-10-12 1984-04-26 Hughes Aircraft Co Controlled porosity dispenser cathode
DE3913338A1 (de) * 1989-04-22 1990-10-25 Licentia Gmbh Einbettmasse, insbesondere fuer kathoden von elektronenroehren
EP0401068A1 (fr) * 1989-05-30 1990-12-05 Thomson Tubes Electroniques Cathode thermo-électronique imprégnée pour tube électronique
EP0915492A1 (en) * 1997-11-04 1999-05-12 Sony Corporation Impregnated cathode and method of manufacturing the same, electron gun and electron tube

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2043991B (en) * 1978-11-30 1983-05-11 Varian Associates Method of fabricating a dispenser cathode

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2121589A (en) * 1934-06-28 1938-06-21 Westinghouse Electric & Mfg Co Emissive incandescent cathode
US2173208A (en) * 1935-05-07 1939-09-19 Ets Claude Paz & Silva Electrode
US2452075A (en) * 1941-12-18 1948-10-26 Raytheon Mfg Co Velocity modulation electron discharge tube
US2459841A (en) * 1943-06-08 1949-01-25 Glenn F Rouse Cathode
US2647216A (en) * 1950-04-01 1953-07-28 Rca Corp Dispenser cathode

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE879872C (de) * 1942-08-19 1953-06-15 Siemens Ag Kathode zur Erzeugung eines Elektronenstrahles
DE895479C (de) * 1951-11-20 1953-11-02 Siemens Ag Kathode fuer elektrische Entladungsgefaesse
NL83577C (enrdf_load_stackoverflow) * 1952-07-23

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2121589A (en) * 1934-06-28 1938-06-21 Westinghouse Electric & Mfg Co Emissive incandescent cathode
US2173208A (en) * 1935-05-07 1939-09-19 Ets Claude Paz & Silva Electrode
US2452075A (en) * 1941-12-18 1948-10-26 Raytheon Mfg Co Velocity modulation electron discharge tube
US2459841A (en) * 1943-06-08 1949-01-25 Glenn F Rouse Cathode
US2647216A (en) * 1950-04-01 1953-07-28 Rca Corp Dispenser cathode

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3102329A (en) * 1958-12-12 1963-09-03 Varta Ag Sinter electrode
US3113236A (en) * 1959-06-23 1963-12-03 Philips Corp Oxide dispenser type cathode
US3176180A (en) * 1961-09-01 1965-03-30 Gen Electric Dispenser cathode
US3594885A (en) * 1969-06-16 1971-07-27 Varian Associates Method for fabricating a dimpled concave dispenser cathode incorporating a grid
US4147954A (en) * 1976-07-10 1979-04-03 E M I-Varian Limited Thermionic electron emitter
US4101800A (en) * 1977-07-06 1978-07-18 The United States Of America As Represented By The Secretary Of The Navy Controlled-porosity dispenser cathode
US4393328A (en) * 1979-11-09 1983-07-12 Thomson-Csf Hot cathode, its production process and electron tube incorporating such a cathode
WO1984001664A1 (en) * 1982-10-12 1984-04-26 Hughes Aircraft Co Controlled porosity dispenser cathode
DE3913338A1 (de) * 1989-04-22 1990-10-25 Licentia Gmbh Einbettmasse, insbesondere fuer kathoden von elektronenroehren
DE3913338C2 (de) * 1989-04-22 1999-12-02 Aeg Elektronische Roehren Gmbh Einbettmasse, insbesondere für Kathoden von Elektronenröhren, Verfahren zur Herstellung einer solchen Einbettmasse und Verwendung einer solchen Einbettmasse
EP0401068A1 (fr) * 1989-05-30 1990-12-05 Thomson Tubes Electroniques Cathode thermo-électronique imprégnée pour tube électronique
FR2647952A1 (fr) * 1989-05-30 1990-12-07 Thomson Tubes Electroniques Cathode thermoelectronique impregnee pour tube electronique
EP0915492A1 (en) * 1997-11-04 1999-05-12 Sony Corporation Impregnated cathode and method of manufacturing the same, electron gun and electron tube

Also Published As

Publication number Publication date
DE1047321B (de) 1958-12-24
FR1173168A (fr) 1959-02-20
CH344139A (de) 1960-01-31
GB800219A (en) 1958-08-20
BE550302A (enrdf_load_stackoverflow)

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