EP0052047B1 - Thermoelectronic cathode - Google Patents

Thermoelectronic cathode Download PDF

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Publication number
EP0052047B1
EP0052047B1 EP81401713A EP81401713A EP0052047B1 EP 0052047 B1 EP0052047 B1 EP 0052047B1 EP 81401713 A EP81401713 A EP 81401713A EP 81401713 A EP81401713 A EP 81401713A EP 0052047 B1 EP0052047 B1 EP 0052047B1
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EP
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Prior art keywords
porous body
impregnated
barium
cathode according
thermoelectronic
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German (de)
French (fr)
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EP0052047B2 (en
EP0052047A1 (en
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Pierre Palluel
Arvind Shroff
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Thales SA
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Thomson CSF SA
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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
    • H01J1/28—Dispenser-type cathodes, e.g. L-cathode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/02—Electrodes; Magnetic control means; Screens
    • H01J23/04—Cathodes

Definitions

  • the present invention relates to a new thermoelectronic cathode structure.
  • Such cathodes find their field of application in electronic tubes, tubes with localized constants such as triodes and tetrodes, or tubes with distributed constants such as klystrons and magnetrons used at microwave frequencies.
  • the power developed by electronic tubes at very high frequencies is limited in particular by the current density produced by the cathode.
  • Thermoelectronic cathodes with a reserve of emissive material have been known for a long time under the name of "L " cathodes;
  • Another improvement consisted in replacing the reserve of alkaline earth with a ceramic consisting of a mixture of alumina, alkaline earth oxides and tungsten powder.
  • impregnated cathodes constituted by a tungsten matrix impregnated with barium and calcium aluminates, in variable proportions.
  • impregnated cathode is described, for example, in DE-A-2 808 134.
  • the cathode described in this application is constituted by a porous accumulator body comprising at least two layers in the pores of which an emissive material is stored, the two layers which may have identical or different porosities. Since the emissive material is impregnated in the two layers, this cathode functions like an impregnated cathode constituted by a matrix in a single layer.
  • L type cathodes have always exhibited a density of emitted current, at equal temperature, greater than that of so-called impregnated cathodes, even in the best cases when the latter are covered with '' a film of a refractory metal with high output work such as osmium, ruthenium, iridium, rhenium, which tends to increase the current density.
  • thermoelectronic cathode comprising inside a cylindrical envelope, a heating filament located in the lower part of said envelope, and two superposed porous bodies inserted at the top of the envelope.
  • the porous bodies are produced by a mixture comprising by weight 90% of powdered tungsten and 10% of barium carbonate or barium peroxide and carbon, mixture covered with a layer of powdered tungsten sintered during activation. It is therefore not a porous body of the impregnated type and the technique for producing this type of cathode is very complex when it is desired to have doses of known volume and weight.
  • the Applicant proposes to produce a cathode structure whose current density is at least equal to that of “L” cathodes, but which would not present the difficulties of technological realization of the latter, or of other types. of cathodes described above.
  • thermo-electronic cathode comprising, inside a cylindrical envelope, a heating filament situated in the lower part of said envelope, and two superposed porous bodies, inserted in the upper part of the envelope, both porous body being constituted by a lower body containing an emissive material, covered with the upper body, the surface of the upper porous body forming the emissive surface of the cathode, characterized in that the lower porous body is a porous body of porosity between 16 and 50% impregnated with the emissive material and the upper porous body is a non-impregnated porous body with porosity between 16 and 21%.
  • FIG. 1 represents an example of a cathode structure “L” of the prior art.
  • a cathode is constituted by a molybdenum tube 1, divided into two cavities; the lower part contains the heating filament 2; the upper part consists of a chamber 3 containing a reserve 4 of barium and calcium carbonates for example.
  • a porous tungsten disc 5 is attached to the top of the barium reservoir, so that the upper cavity communicates outward only through the porous body.
  • the upper face of this disc may comprise a thin layer 6 of a refractory metal with high output work such as osmium, iridium, rhenium, ruthenium, or an alloy of several of these materials.
  • a refractory metal with high output work such as osmium, iridium, rhenium, ruthenium, or an alloy of several of these materials.
  • FIG. 2 represents an example of a cathode structure impregnated with the prior art.
  • a filament 2 is located inside a molybdenum cylinder 1 containing a body of porous tungsten 7 which is impregnated with barium and calcium aluminates.
  • the upper face of the body 7 can be covered with a thin layer 6 of a refractory metal with high output work from one of those mentioned above.
  • the underside of the body 7 rests on a molybdenum bottom 8 ensuring sealing.
  • FIG. 3 represents an example of a cathode structure according to the invention.
  • the cathode according to the invention consists of a cylindrical molybdenum body 1 inside which is located a filament 2 in its lower part and a set of two porous bodies superimposed in its upper part: a porous body 9 free of all impregnating, with a porosity of between 16 and 21%, made of tungsten or of a tungsten alloy and of a refractory metal with high output work such as iridium, rhenium, osmium, ruthenium, porous body of which the front face 10 is the only one through which the emissive material can escape, and a porous body 12 in contact with the rear face 11 of the porous body 9 impregnated with barium and calcium aluminates or a mixture comprising barium aluminates, of calcium and a scandium or barium scandate oxide, this porous body having a porosity of between 16 and 50%, for example.
  • the rear face of the porous body 12 is sealed by conventional means such as the deposition of molyb
  • the front face 10 of the non-impregnated porous body 9 can be covered with a layer of refractory metal with high output work.
  • the porous impregnated body can consist of tungsten impregnated with barium and calcium aluminates, an alloy of tungsten and a refractory metal with high output work impregnated with barium aluminates and calcium or tungsten impregnated with a mixture of barium aluminates and calcium and a scandium oxide.
  • a gap or gap 14 which is filled, in order to improve the thermal contact before placing the porous body 3, either of powder of a conductive metal at high melting temperature, or a grid of molybdenum or tungsten, with a very fine mesh, of pitch 20 ⁇ m for example, which serves as additional conductance for the diffusion of barium towards the porous body 9, or of a flexible foil ensuring contact between the bodies cathodes, either using a thread.
  • This gap 14 can be eliminated by making the assembly by pressing.
  • the porous body 9 generally has a curved shape obtained by machining or by pressing.
  • the operating mechanism of this type of cathode is as follows: the free barium is produced in the porous body 12 by heating the assembly using the filament 2, by chemical reaction between the impregnating agent and the tungsten.
  • This barium then migrates through the pores of the body 3 from the face 11 to the face 10 where it covers its surface, thus lowering the work of leaving it.
  • An electrode placed opposite the cathode, at a certain distance, and brought to a positive potential with respect to the cathode, collects the electrons emitted by the latter.

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  • Solid Thermionic Cathode (AREA)
  • Microwave Tubes (AREA)

Description

La présente invention concerne une nouvelle structure de cathode thermoélectronique. De telles cathodes trouvent leur domaine d'application dans les tubes électroniques, tubes à constantes localisées comme les triodes et les tétrodes, ou tubes à constantes réparties comme les klystrons et les magnétrons utilisés en hyperfréquences.The present invention relates to a new thermoelectronic cathode structure. Such cathodes find their field of application in electronic tubes, tubes with localized constants such as triodes and tetrodes, or tubes with distributed constants such as klystrons and magnetrons used at microwave frequencies.

La puissance développée par les tubes électroniques à des hyperfréquences très élevées est limitée notamment par la densité de courant produite par la cathode.The power developed by electronic tubes at very high frequencies is limited in particular by the current density produced by the cathode.

Il existe depuis longtemps des cathodes thermo-électronique à réserve de matière émissive connues sous le nom de cathodes «L";Thermoelectronic cathodes with a reserve of emissive material have been known for a long time under the name of "L " cathodes;

Elles sont constituées par un tube en molybdène divisé en deux cavités; la partie inférieure contient l'élément chauffant; la partie supérieure comporte un mélange de carbonate de baryum et de calcium, par exemple, et fonctionne comme un réservoir de baryum un disque de tungstène poreux est fixé au sommet du réservoir de baryum, de sorte que la cavité supérieure ne communique vers l'extérieur qu'à travers le corps poreux. Le défaut de ce système est qu'il faut transformer les carbonates en oxydes, opération longue à cause des gaz de réactions qui ne peuvent s'échapper qu'à travers le tungstène poreux.They consist of a molybdenum tube divided into two cavities; the lower part contains the heating element; the upper part contains a mixture of barium carbonate and calcium, for example, and functions as a barium tank a porous tungsten disc is fixed to the top of the barium tank, so that the upper cavity does not communicate towards the outside only through the porous body. The drawback of this system is that it is necessary to transform the carbonates into oxides, a long operation because of the reaction gases which can only escape through porous tungsten.

Une amélioration du présent état de fait a été apportée par l'utilisation directe d'oxydes d'alcalino-terreux et non plus de carbonates; cependant, cette amélioration a amené une autre difficulté importante, celle de la réalisation pratique et du stockage de telles cathodes, du fait de la grande réactivité des oxydes alcalino-terreux avec l'air ambiant.An improvement in the present state of affairs has been brought about by the direct use of alkaline earth oxides and no longer carbonates; however, this improvement has brought another important difficulty, that of the practical production and storage of such cathodes, due to the high reactivity of the alkaline earth oxides with ambient air.

Une autre amélioration a consisté à remplacer la réserve d'alcalino-terreux par une céramique constituée d'un mélange d'alumine, d'oxydes alcalino-terreux et de poudre de tungstène.Another improvement consisted in replacing the reserve of alkaline earth with a ceramic consisting of a mixture of alumina, alkaline earth oxides and tungsten powder.

Les problèmes technologiques des cathodes à réserve ont conduit l'homme de l'art à utiliser dans la pratique les cathodes dites imprégnées constituées par une matrice en tungstène imprégnées d'aluminates de baryum et de calcium, dans des proportions variables. Un type de cathodes imprégnées est décrit, par exemple, dans la DE-A-2 808 134. La cathode décrite dans cette demande est constituée par un corps accumulateur poreux comportant au moins deux couches dans les pores duquel est emmagasinée une matière émissive, les deux couches pouvant avoir des porosités identiques ou différentes. La matière émissive étant imprégnée dans les deux couches, cette cathode fonctionne comme une cathode imprégnée constituée par une matrice en une seule couche.The technological problems of reserve cathodes have led those skilled in the art to use in practice so-called impregnated cathodes constituted by a tungsten matrix impregnated with barium and calcium aluminates, in variable proportions. One type of impregnated cathode is described, for example, in DE-A-2 808 134. The cathode described in this application is constituted by a porous accumulator body comprising at least two layers in the pores of which an emissive material is stored, the two layers which may have identical or different porosities. Since the emissive material is impregnated in the two layers, this cathode functions like an impregnated cathode constituted by a matrix in a single layer.

Cependant, d'après les résultats connus actuellement, les cathodes de type «L» ont toujours présenté une densité de courant émis, à température égale, supérieure à celle des cathodes dites imprégnées, même dans les meilleurs des cas quand ces dernières sont recouvertes d'un film d'un métal réfractaire à haut travail de sortie comme l'osmium, le ruthénium, l'iridium, le rhénium, ce qui tend à augmenter la densité de courant.However, according to the results currently known, “L” type cathodes have always exhibited a density of emitted current, at equal temperature, greater than that of so-called impregnated cathodes, even in the best cases when the latter are covered with '' a film of a refractory metal with high output work such as osmium, ruthenium, iridium, rhenium, which tends to increase the current density.

On connait aussi d'après le brevet FR-A-1 093 241, une cathode thermo-électronique comprenant à l'intérieur d'une enveloppe cylindrique, un filament chauffant situé dans la partie inférieure de ladite enveloppe, et deux corps poreux superposés insérés dans la partie supérieure de l'enveloppe. Toutefois, comme mentionné page 2, colonne de gauche du brevet FR-A-1 093 241, les corps poreux sont réalisés par un mélange comportant en poids 90% de tungstène pulvérulent et 10% de carbonate de baryum ou de peroxyde de baryum et de carbone, mélange recouvert d'une couche de tungstène pulvérulent fritté lors de l'activation. Il ne s'agit donc pas de corps poreux du type imprégné et la technique de réalisation de ce type de cathode est très complexe lorsque l'on désire avoir des doses de volume et de poids connus.Also known from patent FR-A-1 093 241, a thermoelectronic cathode comprising inside a cylindrical envelope, a heating filament located in the lower part of said envelope, and two superposed porous bodies inserted at the top of the envelope. However, as mentioned on page 2, left column of patent FR-A-1 093 241, the porous bodies are produced by a mixture comprising by weight 90% of powdered tungsten and 10% of barium carbonate or barium peroxide and carbon, mixture covered with a layer of powdered tungsten sintered during activation. It is therefore not a porous body of the impregnated type and the technique for producing this type of cathode is very complex when it is desired to have doses of known volume and weight.

Partant de ces constatations, la Demanderesse se propose de réaliser une structure de cathode dont la dénsité de courant est au moins égale à celle des cathodes «L», mais qui ne présenterait pas les difficultés de réalisation technologique de ces dernières, ni des autres types de cathodes décrits ci-dessus.On the basis of these observations, the Applicant proposes to produce a cathode structure whose current density is at least equal to that of “L” cathodes, but which would not present the difficulties of technological realization of the latter, or of other types. of cathodes described above.

La présente invention concerne une cathode thermo-électronique comprenant à l'intérieur d'une enveloppe cylindrique, un filament chauffant situé dans la partie inférieure de ladite enveloppe, et deux corps poreux superposés, insérés dans la partie supérieure de l'enveloppe, les deux corps poreux étant constitués par un corps inférieur contenant une matière émissive, recouvert du corps supérieur, la surface du corps poreux supérieur formant la surface émissive de la cathode, caractérisée en ce que le corps poreux inférieur est un corps poreux de porosité comprise entre 16 et 50% imprégné par la matière émissive et le corps poreux supérieur est un corps poreux non-imprégné de porosité comprise entre 16 et 21%.The present invention relates to a thermo-electronic cathode comprising, inside a cylindrical envelope, a heating filament situated in the lower part of said envelope, and two superposed porous bodies, inserted in the upper part of the envelope, both porous body being constituted by a lower body containing an emissive material, covered with the upper body, the surface of the upper porous body forming the emissive surface of the cathode, characterized in that the lower porous body is a porous body of porosity between 16 and 50% impregnated with the emissive material and the upper porous body is a non-impregnated porous body with porosity between 16 and 21%.

Les avantages d'une telle cathode par rapport aux cathodes connues dans l'art antérieur sont:

  • - sa réalisation technologique non complexe ne nécessitant pas d'appareillage compliqué tel que machine de transfert évitant la mise à l'air des oxydes;
  • - son stockage en atmosphère neutre, les aluminates ne nécessitant pas de précautions excessives;
  • - en fonctionnement, une évaporation non excessive au début de la durée de vie du fait que la zone où le baryum est créée est éloignée de la surface, et que le chemin à franchir par le baryum est toujours le même; cette vitesse d'évaporation se maintient dans le temps du fait de la constance de cette distance;
  • - l'émission électronique qui résulte du recouvrement en baryum est équivalent sinon supérieure à celle des cathodes imprégnées utilisant un matériau poreux analogue.
The advantages of such a cathode compared to cathodes known in the prior art are:
  • - Its non-complex technological implementation does not require complicated equipment such as a transfer machine avoiding the venting of oxides;
  • - its storage in a neutral atmosphere, the aluminates not requiring excessive precautions;
  • - in operation, non-excessive evaporation at the start of the service life because the area where the barium is created is far from the surface, and the path to be crossed by the barium is always the same; this rate of evaporation is maintained over time due to the constancy of this distance;
  • - The electronic emission which results from the barium covering is equivalent if not greater than that of impregnated cathodes using a similar porous material.

L'invention sera mieux comprise en se reportant à la description suivante illustrée par les figures jointes qui représentent:

  • - figure 1: un exemple de cathode «L" de l'art antérieur;
  • - figure 2: un exemple de cathode imprégnée de l'art antérieur;
  • - figure 3: un exemple de cathode selon l'invention.
The invention will be better understood by referring to the following description illustrated by the attached figures which represent:
  • - Figure 1: an example of cathode "L " of the prior art;
  • - Figure 2: an example of cathode impregnated with the prior art;
  • - Figure 3: an example of a cathode according to the invention.

La figure 1 représente un exemple de structure de cathode «L» de l'art antérieur. Une telle cathode est constituée par un tube en molybdène 1, divisé en deux cavités; la partie inférieure contient le filament chauffant 2; la partie supérieure est constituée d'une chambre 3 contenant une réserve 4 de carbonates de baryum et de calcium par exemple.FIG. 1 represents an example of a cathode structure “L” of the prior art. Such a cathode is constituted by a molybdenum tube 1, divided into two cavities; the lower part contains the heating filament 2; the upper part consists of a chamber 3 containing a reserve 4 of barium and calcium carbonates for example.

Un disque de tungstène poreux 5 est fixé au sommet du réservoir de baryum, de sorte que la cavité supérieure ne communique vers l'extérieur qu'à travers le corps poreux.A porous tungsten disc 5 is attached to the top of the barium reservoir, so that the upper cavity communicates outward only through the porous body.

La face supérieure de ce disque peut comporter une mince couche 6 d'un métal réfractaire à haut travail de sortie tel l'osmium, l'iridium, le rhénium, le ruthénium, ou un alliage de plusieurs de ces matériaux.The upper face of this disc may comprise a thin layer 6 of a refractory metal with high output work such as osmium, iridium, rhenium, ruthenium, or an alloy of several of these materials.

Le défaut de ce système est qu'il faut transformer les carbonates en oxydes, opération longue à cause de gaz de réactions qui ne peuvent s'échapper qu'à travers le tungstène poreux.The drawback of this system is that it is necessary to transform the carbonates into oxides, a long operation because of reaction gases which can only escape through porous tungsten.

La figure 2 représente un exemple de structure de cathode imprégnée de l'art antérieur. Sur la figure 2, un filament 2 se trouve à l'intérieur d'un cylindre en molybdène 1 contenant un corps en tungstène poreux 7 qui est imprégné d'aluminates de baryum et de calcium. La face supérieure du corps 7 peut être recouverte d'une mince couche 6 d'un métal réfractaire à haut travail de sortie parmi l'un de ceux cités précédemment. La face inférieure du corps 7 repose sur un fond en molybdène 8 assurant l'étanchéité.FIG. 2 represents an example of a cathode structure impregnated with the prior art. In FIG. 2, a filament 2 is located inside a molybdenum cylinder 1 containing a body of porous tungsten 7 which is impregnated with barium and calcium aluminates. The upper face of the body 7 can be covered with a thin layer 6 of a refractory metal with high output work from one of those mentioned above. The underside of the body 7 rests on a molybdenum bottom 8 ensuring sealing.

La figure 3 représente un exemple de structure de cathode selon l'invention.FIG. 3 represents an example of a cathode structure according to the invention.

La cathode selon l'invention est constituée d'un corps cylindrique en molybdène 1 à l'intérieur duquel est situé un filament 2 dans sa partie inférieure et un ensemble de deux corps poreux superposés dans sa partie supérieure: un corps poreux 9 libre de tout imprégnant, de porosité comprise entre 16 et 21%, en tungstène ou en alliage de tungstène et d'un métal réfractaire à haut travail de sortie tels l'iridium, le rhénium, l'osmium, le ruthénium, corps poreux dont la face avant 10 est la seule par laquelle la matière émissive peut s'évacuer, et un corps poreux 12 en contact avec la face arrière 11 du corps poreux 9 imprégné d'aluminates de baryum et de calcium ou d'un mélange comprenant des aluminates de baryum, de calcium et un oxyde de scandium ou de scandate de baryum, ce corps poreux ayant une porosité comprise entre 16 et 50%, par exemple. La face arrière du corps poreux 12 est rendue étanche par les moyens classiques tels que le dépôt de brasure Molybdène-Ruthénium, ou en reposant sur un fond en molybdène 13.The cathode according to the invention consists of a cylindrical molybdenum body 1 inside which is located a filament 2 in its lower part and a set of two porous bodies superimposed in its upper part: a porous body 9 free of all impregnating, with a porosity of between 16 and 21%, made of tungsten or of a tungsten alloy and of a refractory metal with high output work such as iridium, rhenium, osmium, ruthenium, porous body of which the front face 10 is the only one through which the emissive material can escape, and a porous body 12 in contact with the rear face 11 of the porous body 9 impregnated with barium and calcium aluminates or a mixture comprising barium aluminates, of calcium and a scandium or barium scandate oxide, this porous body having a porosity of between 16 and 50%, for example. The rear face of the porous body 12 is sealed by conventional means such as the deposition of molybdenum-Ruthenium solder, or by resting on a molybdenum bottom 13.

De plus, il est possible de recouvrir la face avant 10 d'une couche 15 obtenue en déposant par phase vapeur du tungstène orienté par exemple, laissant apparaître un reliéf d'îlots successifs sur lesquels on dépose un revêtement anti-émissif 16 d'un matériau à haut travail de sortie.In addition, it is possible to cover the front face 10 with a layer 15 obtained by depositing oriented tungsten by vapor phase, for example, revealing a connection of successive islands on which an anti-emissive coating 16 is deposited with a high output work material.

Selon un autre mode de réalisation, la face avant 10 du corps poreux non imprégné 9 peut être recouvert d'une couche d'un métal réfractaire à haut travail de sortie.According to another embodiment, the front face 10 of the non-impregnated porous body 9 can be covered with a layer of refractory metal with high output work.

A titre d'exemples, le corps poreux imprégné peut être constitué par du tungstène imprégné d'aluminates de baryum et de calcium, un alliage de tungstène et d'un métal réfractaire à haut travail de sortie imprégné d'aluminates de baryum et de calcium ou du tungstène imprégné d'un mélange d'aluminates de baryum et de calcium et d'un oxyde de scandium.By way of examples, the porous impregnated body can consist of tungsten impregnated with barium and calcium aluminates, an alloy of tungsten and a refractory metal with high output work impregnated with barium aluminates and calcium or tungsten impregnated with a mixture of barium aluminates and calcium and a scandium oxide.

Il existe entre les corps poreux 9 et 12 un intervalle ou gap 14, qui est rempli, afin d'améliorer le contact thermique avant mise en place du corps poreux 3, soit de poudre d'un métal conducteur à température de fusion élevée, soit d'une grille en molybdène ou en tungstène, à maille très fine, de pas 20 µm par exemple, qui sert de conductance supplémentaire à la diffusion du baryum vers le corps poreux 9, soit d'un clinquant souple assurant un contact entre les corps de cathodes, soit à l'aide d'un filtage. Ce gap 14 peut être supprimé en réalisant l'ensemble par pressage.There exists between the porous bodies 9 and 12 a gap or gap 14, which is filled, in order to improve the thermal contact before placing the porous body 3, either of powder of a conductive metal at high melting temperature, or a grid of molybdenum or tungsten, with a very fine mesh, of pitch 20 μm for example, which serves as additional conductance for the diffusion of barium towards the porous body 9, or of a flexible foil ensuring contact between the bodies cathodes, either using a thread. This gap 14 can be eliminated by making the assembly by pressing.

Le corps poreux 9 a généralement une forme galbée obtenue par usinage ou par pressage.The porous body 9 generally has a curved shape obtained by machining or by pressing.

D'autres formes de réalisation sont possibles comme l'utilisation dans un magnétron ou un gy- rotron.Other embodiments are possible such as use in a magnetron or a gyrotron.

Le mécanisme de fonctionnement de ce type de cathode est le suivant: le baryum libre est produit dans le corps poreux 12 par chauffage de l'ensemble à l'aide du filament 2, par réaction chimique entre l'imprégnant et le tungstène.The operating mechanism of this type of cathode is as follows: the free barium is produced in the porous body 12 by heating the assembly using the filament 2, by chemical reaction between the impregnating agent and the tungsten.

Ce baryum migre ensuite à travers les pores du corps 3 depuis la face 11 jusqu'à la face 10 où il vient recouvrir sa surface, abaissant ainsi le travail de sortie de celle-ci.This barium then migrates through the pores of the body 3 from the face 11 to the face 10 where it covers its surface, thus lowering the work of leaving it.

Une électrode, non représentée sur la figure 3, placée vis à vis de la cathode, à une certaine distance, et portée à un potentiel positif par rapport à la cathode, recueille les électrons émis par cette dernière.An electrode, not shown in FIG. 3, placed opposite the cathode, at a certain distance, and brought to a positive potential with respect to the cathode, collects the electrons emitted by the latter.

Claims (8)

1. A thermoelectronic cathode comprising a heating filament (2) located in the lower part of a cylindrical casing (1), and two superposed porous bodies inserted in the lower part of the casing, the two porous bodies being composed of a lower body (12) containing an emissive material and of an upper body (9), the surface of the upper porous body constituting the emissive surface of the cathode, characterized in that the lower porous body is a porous body of a porosity included between 16 and 50%, this body being impregnated by the emissive material, and that the upper porous body is a non impregnated porous body, the porosity of which is included between 16 and 21 %.
2. A thermoelectronic cathode according to claim 1, characterized in that a powder of a conducting metal having a high melting temperature is provided between the impregnated porous body (12) and the non-impregnated porous body (9).
3. A thermoelectronic cathode according to claim 1, characterized in that a fine-meshed grid of molybden or of tungsten is provided between the impregnated porous body (12) and the non-impregnated porous body (9).
4. A thermoelectronic cathode according to claim 1, characterized in that a resilient tinsel is provided between the impregnated porous body (12) and the non-impregnated porous body (9).
5. A thermoelectronic cathode according to any one of claims 1 to 4, characterized in that the impregnated porous body is impregnated with a mixture of barium and calcium aluminates and scandium oxide.
6. A thermoelectronic cathode according to any one of claims 1 to 4, characterized in that the impregnated porous body is impregnated with a mixture of barium and calcium aluminates and of barium scandate.
7. A thermoelectronic cathode according to any one of claims 1 to 6, characterized in that the non-impregnated porous body (9) is covered by a layer of tungsten (15) having depressed and embossed areas.
8. A thermoelectronic cathode according to claim 7, characterized in that the embossed areas are covered with a refractory material (16) having a high extraction energy.
EP81401713A 1980-11-07 1981-10-27 Thermoelectronic cathode Expired - Lifetime EP0052047B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8023884 1980-11-07
FR8023884A FR2494035A1 (en) 1980-11-07 1980-11-07 THERMO-ELECTRONIC CATHODE FOR MICROFREQUENCY TUBE AND TUBE INCORPORATING SUCH A CATHODE

Publications (3)

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EP0052047A1 EP0052047A1 (en) 1982-05-19
EP0052047B1 true EP0052047B1 (en) 1986-01-08
EP0052047B2 EP0052047B2 (en) 1990-05-02

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US (1) US4494035A (en)
EP (1) EP0052047B2 (en)
JP (1) JPS57107534A (en)
DE (1) DE3173470D1 (en)
FR (1) FR2494035A1 (en)

Families Citing this family (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0719530B2 (en) * 1984-06-29 1995-03-06 株式会社日立製作所 Cathode ray tube
JPH0416344Y2 (en) * 1985-07-02 1992-04-13
FR2596198A1 (en) * 1986-03-19 1987-09-25 Thomson Csf Cathodes for multibeam klystron, klystron containing such cathodes and method of manufacturing such cathodes
JPS63236239A (en) * 1987-03-10 1988-10-03 シーメンス、アクチエンゲゼルシヤフト Dispenser cathode for discharge tube and making thereof
US4810926A (en) * 1987-07-13 1989-03-07 Syracuse University Impregnated thermionic cathode
US5266414A (en) * 1988-03-18 1993-11-30 Varian Associates, Inc. Solid solution matrix cathode
FR2647952A1 (en) * 1989-05-30 1990-12-07 Thomson Tubes Electroniques IMPREGNATED THERMOELECTRONIC CATHODE FOR ELECTRONIC TUBE
CH678671A5 (en) * 1989-08-22 1991-10-15 Asea Brown Boveri
DE19527723A1 (en) * 1995-07-31 1997-02-06 Philips Patentverwaltung Electric discharge tube or discharge lamp and Scandat supply cathode
JP3696720B2 (en) 1997-07-09 2005-09-21 松下電器産業株式会社 Impregnated cathode and manufacturing method thereof
JPH11102636A (en) 1997-09-26 1999-04-13 Matsushita Electron Corp Cathode, manufacture of cathode and image receiving tube
US6495949B1 (en) * 1999-11-03 2002-12-17 Orion Electric Co., Ltd. Electron tube cathode
FR2833406A1 (en) * 2001-12-10 2003-06-13 Thomson Licensing Sa VACUUM TUBE CATHODE WITH IMPROVED LIFETIME
CN103311066B (en) * 2013-06-03 2015-08-19 哈尔滨工业大学 There is the emitter of the hollow cathode of controlling oneself for spacecraft of inner core

Family Cites Families (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE526506A (en) * 1953-02-16
NL198428A (en) * 1954-06-29
NL94233C (en) * 1954-12-06
US3076915A (en) * 1954-12-24 1963-02-05 Egyesuelt Izzolampa Cathode assembly and method of making same
NL272981A (en) * 1961-01-02
US3373307A (en) * 1963-11-21 1968-03-12 Philips Corp Dispenser cathode
US3558966A (en) * 1967-03-01 1971-01-26 Semicon Associates Inc Directly heated dispenser cathode
BE759174A (en) * 1969-11-21 1971-05-19 Philips Nv RESERVE CATHODE AND ITS REALIZATION PROCESS
US3842309A (en) * 1970-11-12 1974-10-15 Philips Corp Method of manufacturing a storage cathode and cathode manufactured by said method
US3719856A (en) * 1971-05-19 1973-03-06 O Koppius Impregnants for dispenser cathodes
DE2245717A1 (en) * 1972-09-18 1974-03-28 Patra Patent Treuhand ELECTRODE WITH A POROUS SINTER BODY
US4165473A (en) * 1976-06-21 1979-08-21 Varian Associates, Inc. Electron tube with dispenser cathode
FR2390825A1 (en) * 1977-05-13 1978-12-08 Thomson Csf THERMO-IONIC CATHODE WITH INCORPORATED GRID, ITS MANUFACTURING PROCESS AND ELECTRONIC TUBE INCLUDING SUCH A CATHODE
DE2808134A1 (en) * 1978-02-25 1979-08-30 Licentia Gmbh Long-life cathode with porous two layer emitter - has emitting layer thinner and of lower porosity than supporting layer
US4310603A (en) * 1978-11-30 1982-01-12 Varian Associates, Inc. Dispenser cathode
JPS5652835A (en) * 1979-10-01 1981-05-12 Hitachi Ltd Impregnated cathode

Also Published As

Publication number Publication date
FR2494035B1 (en) 1983-05-13
EP0052047B2 (en) 1990-05-02
JPS57107534A (en) 1982-07-05
US4494035A (en) 1985-01-15
EP0052047A1 (en) 1982-05-19
DE3173470D1 (en) 1986-02-20
FR2494035A1 (en) 1982-05-14

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