US3823337A - Cathode for an electric discharge tube - Google Patents

Cathode for an electric discharge tube Download PDF

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Publication number
US3823337A
US3823337A US00363877A US36387773A US3823337A US 3823337 A US3823337 A US 3823337A US 00363877 A US00363877 A US 00363877A US 36387773 A US36387773 A US 36387773A US 3823337 A US3823337 A US 3823337A
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pro
pglu
trp
formula
gly
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Expired - Lifetime
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US00363877A
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English (en)
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N Mitra
Stratum A Van
P Zalm
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US Philips Corp
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US Philips Corp
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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
    • H01J1/15—Cathodes heated directly by an electric current
    • 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
    • H01J1/14—Solid thermionic cathodes characterised by the material
    • H01J1/148—Solid thermionic cathodes characterised by the material with compounds having metallic conductive properties, e.g. lanthanum boride, as an emissive material

Definitions

  • ABSTRACT [30] Foreign Appllcation Priority Data A cathode suitable for poor vacuum conditions and May 30, I972 Netherlands ..7207276 repeated exposures to air consists of a molybdenum support, compact or compressed powder, welded on a [52] US. Cl. 313/346, 313/337 tungstan Wire and having thereon a compressed [51] Int. Cl H01] 1/14, H01] 19/06 ture of rhenium with lanthanum hexaboride. Instead [58] Field Of Search 313/336, 337, 346 of rhenium, a tungsten boride Such as WzB or W285 may be chosen.
  • the known cathodes of this type consist of a rhenium wire bent in the form of a hairpin and covered cataphoretically with a layer of lanthanum hexaboride, which layer is sintered on it (Rev. Sci Inst. 8567, 1965).
  • the drawback of such a cathode as a punctiform electron source is that the curved end of the hairpin filament is not very suitable for a good concentration of the electron beam because the surface is convex and not plane or concave.
  • a very expensive rhenium filament is required because tungsten is attacked by lanthanum hexaboride without a special intermediate layer.
  • a directly heated cathode for an electric discharge tube which is activated with lanthanum hexaboride to which a material is added which releases lanthanum consists of at least one tungsten filament on which a molybdenum plate is welded having thereon a compressed mixture of lanthanum hexaboride and rhenium or a tungsten boride, the lanthanum boride being at most percent by weight of the whole.
  • the filament is a wire bent in the form of a hairpin on the top of which the molybdenum plate is welded.
  • a wire bent in a zig-zag manner or a spirally wound wire, or separate hair-pin wires may be used as a filament.
  • the molybdenum plate may be compressed simultaneously with the layer of powder compressed on it or it may consist of a compact metal.
  • Tungsten boride preferably consists of W B or W 8 No excessive formation of free lanthanum is obtained. In so far as rhenium is used, this occurs only in powder form in the compressed layer which has a smaller influence on the price than a rhenium filament.
  • the mixture according to the invention can be excellently compressed.
  • the molybdenum forms a protective layer between the lanthanum boride and the tungsten filament.
  • those according to the invention are also suitable for discharge tubes having poor vacuum conditions and for tubes in which the cathodes are exposed to air several times, for example, in electron microscopes.
  • a cathode is known from the US. Pat. No. 3,027,480 in which a mixture of tungsten, thorium tetraboride and rhenium as a mixture is sprayed on a tungsten cylinder or in an aperture in a cap.
  • the mixture may also be shaped previously to form a hollow cylinder.
  • the less agressive thorium tetraboride makes a protection between the mixture and the tungsten supporting body which in addition is indirectly'heated superfluous.
  • the mixture is not compressed which in the cathode according to the invention is necessary for a good life.
  • 1 denotes a hard glasstube bottom in which supply wires 2 and 3 of an iron-nickel-cobalt alloy are sealed.
  • a tungsten wire 4 of 0.18 mm diameter is welded to the wires 2 and 3.
  • Welded to the top ofthe hairpin wire 4 is a compressed cathode body consisting of a layer 5 of molybdenum powder with on top a layer 6 of a'mixture of rhenium powder and lanthanum hexaboride in a weight ratio of 5:2.
  • the overall thickness of the cathode body is 0.3 mm
  • the pressure of compression was 3,000 kg/cm Prior to compression, the molybdenum powder is fired in hydrogen at l,300 C for 30 minutes. The whole cathode body is heated in hydrogen at 1,750 C for 15 seconds. The cathode is degassed in a discharge tube at 1,600 C and activated at l,500 C. The saturation emission at 1,400 C may amount to 25 A/cm What is claimed is:
  • a directly heated cathode for an electric discharge tube comprising a tungsten filament, a molybdenum plate welded to said tungsten filament, and a layer con sisting of 30 percent by weight of a compressed mixture of lanthanum hexaboride and the remainder essentially rhenium or a tungsten boride on said molybdenum plate.

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  • Solid Thermionic Cathode (AREA)
US00363877A 1972-05-30 1973-05-25 Cathode for an electric discharge tube Expired - Lifetime US3823337A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL7207276A NL7207276A (enrdf_load_stackoverflow) 1972-05-30 1972-05-30

Publications (1)

Publication Number Publication Date
US3823337A true US3823337A (en) 1974-07-09

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ID=19816154

Family Applications (1)

Application Number Title Priority Date Filing Date
US00363877A Expired - Lifetime US3823337A (en) 1972-05-30 1973-05-25 Cathode for an electric discharge tube

Country Status (9)

Country Link
US (1) US3823337A (enrdf_load_stackoverflow)
JP (1) JPS555660B2 (enrdf_load_stackoverflow)
CA (1) CA990777A (enrdf_load_stackoverflow)
CH (1) CH554071A (enrdf_load_stackoverflow)
DE (1) DE2325274C3 (enrdf_load_stackoverflow)
FR (1) FR2186722B1 (enrdf_load_stackoverflow)
GB (1) GB1378138A (enrdf_load_stackoverflow)
NL (1) NL7207276A (enrdf_load_stackoverflow)
SE (1) SE382885B (enrdf_load_stackoverflow)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4009409A (en) * 1975-09-02 1977-02-22 Gte Sylvania Incorporated Fast warmup cathode and method of making same
US4019081A (en) * 1974-10-25 1977-04-19 Bbc Brown Boveri & Company Limited Reaction cathode
US4054946A (en) * 1976-09-28 1977-10-18 Bell Telephone Laboratories, Incorporated Electron source of a single crystal of lanthanum hexaboride emitting surface of (110) crystal plane
US4055780A (en) * 1975-04-10 1977-10-25 National Institute For Researches In Inorganic Materials Thermionic emission cathode having a tip of a single crystal of lanthanum hexaboride
US4137476A (en) * 1977-05-18 1979-01-30 Denki Kagaku Kogyo Kabushiki Kaisha Thermionic cathode
US4168565A (en) * 1977-05-18 1979-09-25 Denki Kagaku Kogyo Kabushiki Kaisha Method for manufacturing thermionic cathode
US4258283A (en) * 1978-08-31 1981-03-24 Balzers Aktiengesellschaft Fur Hochvakuumtechnik Und Dunne Schichten Cathode for electron emission
US4482839A (en) * 1981-05-29 1984-11-13 Denki Kagaku Kogyo Kabushiki Kaisha Thermionic emission cathode and preparation thereof
EP0637046A1 (en) * 1993-07-29 1995-02-01 Nec Corporation Thermoionic emissive cathode method of fabricating the same thermoionic emissive cathode and electron beam apparatus
US20100134313A1 (en) * 2008-12-02 2010-06-03 Canon Kabushiki Kaisha Electron-emitting device and display panel including the same

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS607335B2 (ja) * 1974-11-29 1985-02-23 カナデイアン、パテンツ、アンド、デイベラツプメント、リミテツド 熱電子放射陰極
FR2445605A1 (fr) * 1978-12-27 1980-07-25 Thomson Csf Cathode a chauffage direct et tube electronique haute frequence comportant une telle cathode

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4019081A (en) * 1974-10-25 1977-04-19 Bbc Brown Boveri & Company Limited Reaction cathode
US4055780A (en) * 1975-04-10 1977-10-25 National Institute For Researches In Inorganic Materials Thermionic emission cathode having a tip of a single crystal of lanthanum hexaboride
US4009409A (en) * 1975-09-02 1977-02-22 Gte Sylvania Incorporated Fast warmup cathode and method of making same
US4054946A (en) * 1976-09-28 1977-10-18 Bell Telephone Laboratories, Incorporated Electron source of a single crystal of lanthanum hexaboride emitting surface of (110) crystal plane
US4137476A (en) * 1977-05-18 1979-01-30 Denki Kagaku Kogyo Kabushiki Kaisha Thermionic cathode
US4168565A (en) * 1977-05-18 1979-09-25 Denki Kagaku Kogyo Kabushiki Kaisha Method for manufacturing thermionic cathode
US4258283A (en) * 1978-08-31 1981-03-24 Balzers Aktiengesellschaft Fur Hochvakuumtechnik Und Dunne Schichten Cathode for electron emission
US4482839A (en) * 1981-05-29 1984-11-13 Denki Kagaku Kogyo Kabushiki Kaisha Thermionic emission cathode and preparation thereof
EP0637046A1 (en) * 1993-07-29 1995-02-01 Nec Corporation Thermoionic emissive cathode method of fabricating the same thermoionic emissive cathode and electron beam apparatus
US20100134313A1 (en) * 2008-12-02 2010-06-03 Canon Kabushiki Kaisha Electron-emitting device and display panel including the same
US8344607B2 (en) * 2008-12-02 2013-01-01 Canon Kabushiki Kaisha Electron-emitting device and display panel including the same

Also Published As

Publication number Publication date
NL7207276A (enrdf_load_stackoverflow) 1973-12-04
DE2325274B2 (de) 1980-10-23
FR2186722A1 (enrdf_load_stackoverflow) 1974-01-11
DE2325274A1 (de) 1973-12-13
JPS555660B2 (enrdf_load_stackoverflow) 1980-02-08
GB1378138A (en) 1974-12-18
CH554071A (de) 1974-09-13
DE2325274C3 (de) 1981-07-09
JPS4944662A (enrdf_load_stackoverflow) 1974-04-26
CA990777A (en) 1976-06-08
SE382885B (sv) 1976-02-16
FR2186722B1 (enrdf_load_stackoverflow) 1976-09-17

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