EP0401068A1 - Imprägnierte thermiorische Kathode für Elektronenröhre - Google Patents

Imprägnierte thermiorische Kathode für Elektronenröhre Download PDF

Info

Publication number
EP0401068A1
EP0401068A1 EP90401216A EP90401216A EP0401068A1 EP 0401068 A1 EP0401068 A1 EP 0401068A1 EP 90401216 A EP90401216 A EP 90401216A EP 90401216 A EP90401216 A EP 90401216A EP 0401068 A1 EP0401068 A1 EP 0401068A1
Authority
EP
European Patent Office
Prior art keywords
layer
cathode
micrometers
thermoelectronic
emissive
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.)
Withdrawn
Application number
EP90401216A
Other languages
English (en)
French (fr)
Inventor
Arvind Shroff
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.)
Thales Electron Devices SA
Original Assignee
Thomson Tubes Electroniques
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
Application filed by Thomson Tubes Electroniques filed Critical Thomson Tubes Electroniques
Publication of EP0401068A1 publication Critical patent/EP0401068A1/de
Withdrawn legal-status Critical Current

Links

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

Definitions

  • thermo-electronic cathode impregnated for electronic tube such as a tube with localized interaction (triode or tube with more than 3 electrodes) or with distributed interaction (klystron, traveling wave tube, magnetron, gyrotron, etc. ).
  • thermoelectronic cathodes which can emit, under certain conditions of manufacture and operating temperature, current densities of up to 10 to 12 A / cm2.
  • cathodes are made from a porous Tungsten matrix whose porosity, which is low and of the order of 18% to fix ideas, is completely random. This porous body is impregnated with Barium aluminates and Calcium. A mixture is then obtained which, melting at high temperature, has the advantage of remaining solid at the operating temperature of these cathodes which is generally between 980 and 1100 degrees centigrade.
  • the diameter of the pore tends, up to a certain depth which can go up to 200 micrometers, to decrease due to the chemical reactions between Tungsten and Aluminates of Barium and Calcium, which decreases the conductance correspondingly and leads to the need for a higher pressure of Barium so that the latter can migrate towards the surface of the cathode.
  • the channel which constitutes the pore has thus narrowed to a height greater than 200 micrometers, the Barium can no longer rise, despite the use of a higher pressure, so that the cathode can no longer function.
  • thermoelectronic cathode comprising inside a cylindrical envelope, made of molybdenum for example, a heating filament located in the lower part of this envelope and, in the upper part of the latter, a chamber filled with a certain amount of a porous material which comprises two separate superimposed parts, namely a first part made of porous material impregnated with emissive material covered with a second part made of porous material not impregnated.
  • cathodes have the disadvantage of being difficult to produce technologically.
  • the presence at the front of the emissive matrix of a thick porous element can be a source of restarting problems for these cathodes due to the gases which are likely to be absorbed in this porous element.
  • the invention relates to an impregnated thermoelectronic cathode which does not have the aforementioned drawbacks of impregnated cathodes known hitherto and which moreover allows better migration of the emissive material on its surface.
  • This cathode is of the type comprising, inside a generally cylindrical envelope made of molybdenum for example, a heating filament located in the lower part of this envelope and, in the upper part of this same envelope, a chamber filled with a porous material impregnated with emissive material.
  • This porous material is covered, to form the emissive surface of the cathode, with a layer of a non-porous refractory metal and artificially pierced with a set of fine slits which are distributed in an orderly manner and so as to obtain, for this cathode, a determined surface porosity, for example a low porosity of the order of 16 to 21%, capable of allowing the migration of the emissive product (in this case Barium) over the entire emissive surface of this cathode.
  • a determined surface porosity for example a low porosity of the order of 16 to 21%
  • the minimum distance which separates two neighboring slits must be sufficient (preferably just sufficient) to allow this migration, and typically has a value of the order of one to two tens of micrometers.
  • this impregnated cathode is constituted by a tube 1 made of molybdenum, divided into two cavities by a transverse disc 2, also made of molybdenum: . a lower cavity which contains the heating filament 3; . an upper cavity which contains a body 4 of porous Tungsten impregnated with Barium aluminates and Calcium.
  • the porous body 4 is covered, to form the emissive surface of the cathode, with a layer 5 of non-porous Tungsten and pierced, by etching, of a set of fine slots 6 which, as seen more precisely in FIG. 2, are regularly distributed over the surface of this metal layer 5.
  • Layer 5 is relatively thick, its thickness being for example between 100 and 250 micrometers.
  • the slits 6, which each typically have a length of the order of 20 micrometers and a width of the order of 5 micrometers, are distributed in an orderly fashion over the surface of the layer 5, so that the distance d which separates two neighboring slits (see FIG. 3 which is an enlarged view of detail A in FIG. 2) is advantageously calculated to be substantially equal to twice the minimum migration distance of the Barium on the surface of the cathode (emissive surface), when the 'This cathode is heated by carrying the filament 3 to incandescent. This distance d is of the order of one to two tens of micrometers.
  • the porous body 4 is on the contrary chosen to be of high porosity, its porosity being for example greater than 30%.
  • this layer 5 is deposited by the conventional process of chemical decomposition in the gas phase, or CVD ("Chemical Vapor Deposition "), more precisely by reduction of Sulfur Hexafluoride by Hydrogen, at low pressure and temperature.
  • the slots 6 are obtained by reactive ion machining, or "reactive ion etching under plasma", using either an Argon-Chlorine mixture, or a mixture of Sulfur Hexafluoride, Argon, and Oxygen, or a mixture of Sulfur Hexafluoride and Oxygen, by conventional photogravure or chemical etching techniques.
  • FIGS. 4 to 9 illustrate a practical example of the thermoelectronic cathode of FIG. 1.
  • This body 4 is then covered, by chemical decomposition in the gas phase, with a layer 5 of non-porous tungsten, with a thickness of the order of 100 to 200 micrometers.
  • a thin film of aluminum is then deposited with a thickness of a few micrometers (typically of the order of 2 to 5 micrometers).
  • FIG. 7 After elimination of the photosensitive resin 8, there remains (FIG. 7) on the layer of Tungsten 5, a mask 7 of Aluminum, of shape identical to that of the filter 5 (FIG. 2) to be obtained.
  • the production of the mask 7 made of aluminum (or other metal, such as chromium, able to resist sulfur hexafluoride) is required by the fact that the known photosensitive resins do not resist not to reactive ion etching operations under plasma.
  • the machining (FIG. 8) of the layer of Tungsten 5 is then carried out by reactive ion etching under plasma, under reduced pressure of a mixture of the three gases: Argon, Oxygen and Sulfur Hexafluoride.
  • the attack speed depending on the partial pressure in the enclosure used and the applied voltage, is of the order of 1 to 10 micrometers per minute.
  • the body 4 After a chemical cleaning carried out to remove the excess of Barium aluminate over the thickness of the etched layer 5, the body 4 is placed in the molybdenum tube 1, and the heating filament 3 is also put in place.
  • the layer, non-porous and with a thickness at least equal to 100 micrometers, 5 can be made of another refractory metal than Tungsten, for example Rhenium, Iridium, and Osmium, which are all metals well suited to the thermoelectronic emission phenomenon of cathodes.
  • This same upper layer 5 with ordered porosity can also be made of an alloy refractory, for example a Tungsten-Osmium, Tungsten-Iridium, or Tungsten-Rhenium alloy.
  • layer 5 can of course also consist of an added layer and therefore ultimately independent of the porous body.

Landscapes

  • Solid Thermionic Cathode (AREA)
EP90401216A 1989-05-30 1990-05-07 Imprägnierte thermiorische Kathode für Elektronenröhre Withdrawn EP0401068A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8907084A FR2647952A1 (fr) 1989-05-30 1989-05-30 Cathode thermoelectronique impregnee pour tube electronique
FR8907084 1989-05-30

Publications (1)

Publication Number Publication Date
EP0401068A1 true EP0401068A1 (de) 1990-12-05

Family

ID=9382156

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90401216A Withdrawn EP0401068A1 (de) 1989-05-30 1990-05-07 Imprägnierte thermiorische Kathode für Elektronenröhre

Country Status (3)

Country Link
EP (1) EP0401068A1 (de)
JP (1) JPH0317929A (de)
FR (1) FR2647952A1 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0492763A1 (de) * 1990-12-21 1992-07-01 Hughes Aircraft Company Aufgedampfte Scandatbeschichtung für Vorratskathoden und Verfahren zu deren Herstellung
EP0549034A1 (de) * 1991-12-21 1993-06-30 Philips Patentverwaltung GmbH Kathode und Verfahren zu ihrer Herstellung
CN103311066A (zh) * 2013-06-03 2013-09-18 哈尔滨工业大学 具有内芯的用于航天器自持空心阴极的发射体

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2864028A (en) * 1955-08-15 1958-12-09 Philips Corp Thermionic dispenser cathode
EP0052047A1 (de) * 1980-11-07 1982-05-19 Thomson-Csf Thermoelektronische Kathode
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

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2864028A (en) * 1955-08-15 1958-12-09 Philips Corp Thermionic dispenser cathode
EP0052047A1 (de) * 1980-11-07 1982-05-19 Thomson-Csf Thermoelektronische Kathode
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

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
INTERNATIONAL ELECTRON DEVICES MEETING, INSTITUTE OF ELECTRICAL & ELECTRONICS ENGINEERS, IEDM'83, Washington, 5-7 décembre 1983, pages 448-451, IEEE, New York, US; L.R. FALCE: "Dispenser cathodes: the current state of the technology" *
INTERNATIONAL ELECTRON DEVICES MEETING, INSTITUTE OF ELECTRICAL & ELECTRONICS ENGINEERS, Washington, 4-6 décembre 1978, pages 156-159; L.R. FALCE et al.: "Controlled porosity dispenser cathode: iridium-barium oxide" *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0492763A1 (de) * 1990-12-21 1992-07-01 Hughes Aircraft Company Aufgedampfte Scandatbeschichtung für Vorratskathoden und Verfahren zu deren Herstellung
EP0549034A1 (de) * 1991-12-21 1993-06-30 Philips Patentverwaltung GmbH Kathode und Verfahren zu ihrer Herstellung
CN103311066A (zh) * 2013-06-03 2013-09-18 哈尔滨工业大学 具有内芯的用于航天器自持空心阴极的发射体
CN103311066B (zh) * 2013-06-03 2015-08-19 哈尔滨工业大学 具有内芯的用于航天器自持空心阴极的发射体

Also Published As

Publication number Publication date
JPH0317929A (ja) 1991-01-25
FR2647952A1 (fr) 1990-12-07

Similar Documents

Publication Publication Date Title
JPH09221309A (ja) カーボンナノチューブを表面に有する炭素質物及びその製造方法
FR2734401A1 (fr) Cathode froide a emission de champ ayant une caracteristique d'isolement amelioree et procede pour la fabriquer
FR2744564A1 (fr) Corps de cathode, canon a electrons, et tube a rayons cathodiques, utilisant un emetteur ferroelectrique
FR2713394A1 (fr) Source d'électron de type à émission de champ.
KR100497645B1 (ko) 고압방전램프용전극구조및그제조방법
EP1365991B1 (de) Verfahren zur bildung einer kohlenstoffnanoröhren enthaltenden beschichtung auf einem substrat
EP0052047B2 (de) Thermoelektronische Kathode
FR2891662A1 (fr) Emetteurs de champ a nanotiges declenches
EP0401068A1 (de) Imprägnierte thermiorische Kathode für Elektronenröhre
FR2723255A1 (fr) Dispositif d'affichage a emission de champ et procede pour fabriquer de tels dispositifs
FR2664094A1 (fr) Tube a vide microminiature sur un substrat semiconducteur et procede de fabrication.
FR2493036A1 (fr) Photocathode bialcaline a reponse spectrale elargie et procede de fabrication
FR2473785A1 (fr) Dispositif de cathode pour tubes fluorescents
EP0441698B1 (de) Herstellungsverfahren einer Impregnierungskathode und mittels eines solchen Verfahrens gewonnene Kathode
US2967962A (en) Television and like camera tubes
FR2756969A1 (fr) Ecran d'affichage comprenant une source d'electrons a micropointes, observable a travers le support des micropointes, et procede de fabrication de cette source
EP0708473A1 (de) Verfahren zur Herstellung einer Mikrospitzen-Elektronenquelle
EP0856868B1 (de) Feldemissionselektronenquelle und Bildschirm mit solcher Feldemissionselektronenquelle
EP0038742B1 (de) Herstellungsverfahren einer imprägnierten Kathode mit integriertem Gitter, nach diesem Verfahren hergestellte Kathode und mit einer solchen Kathode versehene Elektronenröhre
US5800233A (en) Process of fabricating field-emission type electron source, electron source fabricated thereby and element structure of electron source
EP1200973B1 (de) Oxidkathode und zugehöriges herstellungsverfahren
JP3188952B2 (ja) カーボンナノチューブの回収方法
FR2683090A1 (fr) Cathode a reserve et procede de fabrication d'une telle cathode.
FR2719155A1 (fr) Procédé de réalisation de sources d'électrons à micropointes et source d'électrons à micropointes obtenue par ce procédé.
FR2757999A1 (fr) Procede d'auto-alignement utilisable en micro-electronique et application a la realisation d'une grille de focalisation pour ecran plat a micropointes

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE FR GB IT NL

17P Request for examination filed

Effective date: 19901217

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 19921201