EP0330543B1 - Directly heated cathode manufactured from thermally emissive material - Google Patents
Directly heated cathode manufactured from thermally emissive material Download PDFInfo
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- EP0330543B1 EP0330543B1 EP19890400375 EP89400375A EP0330543B1 EP 0330543 B1 EP0330543 B1 EP 0330543B1 EP 19890400375 EP19890400375 EP 19890400375 EP 89400375 A EP89400375 A EP 89400375A EP 0330543 B1 EP0330543 B1 EP 0330543B1
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- EP
- European Patent Office
- Prior art keywords
- boride
- refractory material
- cathode according
- silicide
- thermoemissive
- 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
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Classifications
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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
Definitions
- the present invention relates to a direct heating cathode for high power electronic tubes or for electron microscope filaments.
- the direct heating cathodes used in this type of tube are generally constituted by a cylindrical sleeve, formed from wires of thorium tungsten. These wires are wound in a helix and distributed in two plies inclined in opposite directions with respect to a generator of the cylinder, so as to form a trellis. The wires of the two layers are joined at each crossing by a solder point.
- the structure obtained is then carburetted by heating in the vapor phase of naphthalene or acetylene for example.
- the wires are brought to operating temperature, of the order of 1700 ° C., by circulation of electric current. Heating the tungsten wires to this temperature causes the emission of electrons.
- cathodes are obtained from a cylindrical, hollow, graphite blank, produced by pyrolysis. This blank is then machined in order to obtain an openwork structure forming a mesh. On the pyrolytic graphite blank, a layer of a material with high thermoemissive power is deposited. This thermoemissive material must be compatible with graphite pyrolytic at the operating temperature of the cathode. The advantage of these cathodes is that they practically do not deform.
- the coefficient of thermal expansion of pyrolytic graphite is low.
- the expansion of such cathodes is three times lower than that of thoriated tungsten cathodes.
- a tungsten cathode the diameter of which is 40 millimeters, expands by 180 micrometers when heated to its nominal operating temperature.
- a cathode of the same diameter in pyrolytic graphite only expands by 60 micrometers.
- the control grid is generally also made of pyrolytic graphite. This grid, in the form of a hollow cylinder, encircles the cathode. In operation, there are no longer any mechanical problems, linked to the difference in thermal behavior of the materials constituting the cathode and the control grid. It is possible to envisage a non-negligible reduction in the cathode-control grid space.
- thermoemissive material commonly used is a rare earth boride such as lanthanum hexaboride (La B6). Its thermoemissive power is high; at 1500 ° C, the thermoelectronic emission of this body is of the order of 2A / cm2. Its reaction to graphite is weak. Its coefficient of expansion is lower than that of tungsten. However, its evaporation is very important as soon as it is heated. This limits the lifespan of such cathodes to around 1000 hours and contributes to their destruction.
- La B6 rare earth boride
- the invention aims to remedy this drawback by proposing a direct heating cathode, having a high thermoelectronic emission and whose lifetime is increased.
- the present invention provides: a cathode, with direct heating, practically undeformable, at least partly in thermoemissive material, characterized in that the thermoemissive material for the emission of electrons is coated with a layer of refractory material in order to limit the loss of thermoemissive material by evaporation.
- the refractory material is chosen so that its rate of evaporation is low. It must also have a high resistance to oxidation and ion bombardment.
- the cathode will consist of a pyrolytic graphite support covered with a layer of thermoemissive material itself covered with a thin layer of refractory material. Thanks to the low coefficient of thermal expansion of pyrolytic graphite, this embodiment makes it possible to obtain a non-deformable cathode.
- the direct heating cathode according to the invention is preferably constituted by a cylindrical hollow hollow graphite produced by pyrolysis. This blank is then machined in order to obtain an openwork structure forming a mesh. The heating is done by circulation of current in the bars constituting each mesh.
- the blank is then coated with a layer of a rare earth boride, for example, lanthanum hexaboride (LaB6).
- a rare earth boride for example, lanthanum hexaboride (LaB6).
- the deposition is preferably carried out by a method of spraying lanthanum hexaboride powder into a plasma, composed, for example, of argon and hydrogen in the same amounts. This operation takes place at very high temperature, either at atmospheric pressure, or preferably in a rarefied atmosphere.
- the powder flow rate is of the order of one kilogram per hour, the distance between the plasma and the cathode being between 30 centimeters and 1 meter.
- the characteristics of the plasma are as follows: for a volume of gas of the order of ten cubic centimeters, the current is of the order of 400 amperes and the voltage of the order of 40 volts.
- the thickness of the lanthanum hexaboride layer will preferably be between 10 and 100 micrometers.
- Lanthanum hexaboride is chosen because of its high thermoelectronic emission. But the evaporation of lanthanum hexaboride is important when it is heated. In order to limit the loss of material by evaporation, the lanthanum hexaboride is covered with a film of refractory material.
- the refractory material is deposited so as to form a compact and homogeneous layer. This deposition is carried out, preferably by a method of spraying powder of refractory material into a plasma, similar to that used for the deposition of lanthanum hexaboride.
- the thickness of the layer of refractory material will preferably be between 10 and 100 micrometers.
- the materials used for this deposit are chosen to be refractory and have a low rate of evaporation, a high resistance to oxidation and to ion bombardment. They do not alter the thermoemissive properties of lanthanum hexaboride. They are also chosen so as to be obtained, in the molten state, without alteration of their intrinsic physicochemical properties, for example, stoichiometry. With this refractory layer, the heat dissipation of the cathode is reduced, which means that the ratio of electronic emission to heating power is significantly increased compared to lanthanum hexaboride cathodes of the prior art. Thanks to the low coefficient of expansion of pyrolytic graphite, the cathode thus produced is practically undeformable.
- the refractory material is a compound of boron and a metal of the platinum mine:
- the cathode should be formed directly from the emissive material (lanthanum hexaboride for example) covered with the refractory layer, without graphite support. It is also conceivable that the support is other than a graphite.
- the present invention is not limited to the examples given for the composition of the thermoemissive material and of the refractory material.
Landscapes
- Solid Thermionic Cathode (AREA)
Description
La présente invention concerne une cathode à chauffage direct pour tubes électroniques de forte puissance ou pour filaments de microscopes électroniques.The present invention relates to a direct heating cathode for high power electronic tubes or for electron microscope filaments.
Les cathodes à chauffage direct utilisées dans ce genre de tubes sont généralement constituées par un manchon cylindrique, formé de fils de tungstène thorié. Ces fils sont bobinés en hélice et répartis en deux nappes inclinées en sens opposé par rapport à une génératrice du cylindre, de manière à former un treillis. Les fils des deux nappes sont réunis à chaque croisement par un point de soudure.The direct heating cathodes used in this type of tube are generally constituted by a cylindrical sleeve, formed from wires of thorium tungsten. These wires are wound in a helix and distributed in two plies inclined in opposite directions with respect to a generator of the cylinder, so as to form a trellis. The wires of the two layers are joined at each crossing by a solder point.
La structure obtenue est ensuite carburée par chauffage en phase vapeur de naphtalène ou d'acétylène par exemple.The structure obtained is then carburetted by heating in the vapor phase of naphthalene or acetylene for example.
Les fils sont portés à la température de fonctionnement, de l'ordre de 1700°C, par circulation de courant électrique. Le chauffage des fils de tungstène à cette température entraine l'émission des électrons.The wires are brought to operating temperature, of the order of 1700 ° C., by circulation of electric current. Heating the tungsten wires to this temperature causes the emission of electrons.
Les allumages et les extinctions répétés sur de telles structures conduisent fréquemment à des déformations permanentes, qui altèrent les caractéristiques du tube électronique. Ces déformations sont dues à la dilatation importante du tungstène à la chaleur.Repeated ignitions and extinctions on such structures frequently lead to permanent deformations, which alter the characteristics of the electron tube. These deformations are due to the significant expansion of tungsten when heated.
Il existe aussi des cathodes à chauffage direct en graphite pyrolytique. Ce matériau est connu pour ses qualités mécaniques et thermiques.There are also direct-heating pyrolytic graphite cathodes. This material is known for its mechanical and thermal qualities.
Ces cathodes sont obtenues à partir d'une ébauche cylindrique, creuse, en graphite, réalisée par pyrolyse. Cette ébauche est ensuite usinée afin d'obtenir une structure ajourée formant un maillage. Sur l'ébauche en graphite pyrolytique on dépose une couche d'un matériau à pouvoir thermoémissif élevé. Ce matériau thermoémissif doit être compatible avec le graphite pyrolytique à la température de fonctionnement de la cathode. L'avantage de ces cathodes est qu'elles ne se déforment pratiquement pas.These cathodes are obtained from a cylindrical, hollow, graphite blank, produced by pyrolysis. This blank is then machined in order to obtain an openwork structure forming a mesh. On the pyrolytic graphite blank, a layer of a material with high thermoemissive power is deposited. This thermoemissive material must be compatible with graphite pyrolytic at the operating temperature of the cathode. The advantage of these cathodes is that they practically do not deform.
En effet, le coefficient de dilatation thermique du graphite pyrolytique est bas. La dilatation de telles cathodes est trois fois plus faible que celle des cathodes en tungstène thorié. Par exemple, une cathode en tungstène, dont le diamètre est de 40 millimètres, se dilate de 180 micromètres lorsqu'elle est chauffée à sa température nominale de fonctionnement. Une cathode de même diamètre en graphite pyrolytique ne se dilate que de 60 micromètres. Dans les tubes électroniques de puissance, la grille de commande est généralement également en graphite pyrolytique. Cette grille, en forme de cylindre creux encercle la cathode. En fonctionnement, il n'y a plus de problèmes mécaniques, liés à la différence de comportement thermique des matériaux constituant la cathode et la grille de commande. Il est possible d'envisager une diminution non négligeable de l'espace cathode-grille de commande.In fact, the coefficient of thermal expansion of pyrolytic graphite is low. The expansion of such cathodes is three times lower than that of thoriated tungsten cathodes. For example, a tungsten cathode, the diameter of which is 40 millimeters, expands by 180 micrometers when heated to its nominal operating temperature. A cathode of the same diameter in pyrolytic graphite only expands by 60 micrometers. In power electronic tubes, the control grid is generally also made of pyrolytic graphite. This grid, in the form of a hollow cylinder, encircles the cathode. In operation, there are no longer any mechanical problems, linked to the difference in thermal behavior of the materials constituting the cathode and the control grid. It is possible to envisage a non-negligible reduction in the cathode-control grid space.
Un matériau thermoémissif couramment employé est un borure de terres rares tel que l'hexaborure de lanthane (La B₆). Son pouvoir thermoémissif est élevé; à 1500°C, l'émission thermoélectronique de ce corps est de l'ordre de 2A/cm². Sa réaction vis à vis du graphite est faible. Son coefficient de dilatation est plus faible que celui du tungstène. En revanche, son évaporation est très importante dès qu'il est chauffé. Cela limite la durée de vie de telles cathodes à environ 1000 heures et contribue à leur destruction.A thermoemissive material commonly used is a rare earth boride such as lanthanum hexaboride (La B₆). Its thermoemissive power is high; at 1500 ° C, the thermoelectronic emission of this body is of the order of 2A / cm². Its reaction to graphite is weak. Its coefficient of expansion is lower than that of tungsten. However, its evaporation is very important as soon as it is heated. This limits the lifespan of such cathodes to around 1000 hours and contributes to their destruction.
L'invention vise à remédier à cet inconvénient en proposant une cathode à chauffage direct, ayant une émission thermoélectronique élevée et dont la durée de vie est augmentée.The invention aims to remedy this drawback by proposing a direct heating cathode, having a high thermoelectronic emission and whose lifetime is increased.
La présente invention propose:
une cathode, à chauffage direct, pratiquement indéformable, au moins en partie en matériau thermoémissif, caractérisée en ce que le matériau thermoémissif pour l'émission d'électrons est revêtu d'une couche de matériau réfractaire afin de limiter la perte de matériau thermoémissif par évaporation.The present invention provides:
a cathode, with direct heating, practically undeformable, at least partly in thermoemissive material, characterized in that the thermoemissive material for the emission of electrons is coated with a layer of refractory material in order to limit the loss of thermoemissive material by evaporation.
Le matériau réfractaire est choisi de manière à ce que sa vitesse d'évaporation soit faible. Il doit aussi avoir une grande résistance à l'oxydation et au bombardement ionique.The refractory material is chosen so that its rate of evaporation is low. It must also have a high resistance to oxidation and ion bombardment.
Il est déposé en couche suffisamment mince pour ne pas perturber exagérément l'émission d'électrons.It is deposited in a sufficiently thin layer so as not to excessively disturb the emission of electrons.
De préférence, la cathode sera constituée d'un support en graphite pyrolytique recouvert d'une couche de matériau thermoémissif lui-même recouvert d'une fine couche de matériau réfractaire. Grâce au faible coefficient de dilatation thermique du graphite pyrolytique, cette réalisation permet d'obtenir, une cathode indéformable.Preferably, the cathode will consist of a pyrolytic graphite support covered with a layer of thermoemissive material itself covered with a thin layer of refractory material. Thanks to the low coefficient of thermal expansion of pyrolytic graphite, this embodiment makes it possible to obtain a non-deformable cathode.
D'autres caractéristiques et avantages de l'invention ressortiront à la lecture de la description suivante.Other characteristics and advantages of the invention will emerge on reading the following description.
La cathode à chauffage direct, selon l'invention, est de préférence constituée par une ébauche cylindrique, creuse en graphite réalisée par pyrolyse. Cette ébauche est ensuite usinée afin d'obtenir une structure ajourée formant un maillage. Le chauffage se fait par circulation de courant dans les barreaux constituant chaque maille.The direct heating cathode according to the invention is preferably constituted by a cylindrical hollow hollow graphite produced by pyrolysis. This blank is then machined in order to obtain an openwork structure forming a mesh. The heating is done by circulation of current in the bars constituting each mesh.
L'ébauche est ensuite revêtue d'une couche d'un borure de terres rares, par exemple, de l'hexaborure de lanthane (LaB₆). Le dépôt est réalisé de préférence par un procédé de projection de poudre d'hexaborure de lanthane dans un plasma, composé, par exemple, d'argon et d'hydrogène en mêmes quantités. Cette opération a lieu à très haute température, soit à la pression atmosphérique, soit de préférence dans une atmosphère raréfiée.The blank is then coated with a layer of a rare earth boride, for example, lanthanum hexaboride (LaB₆). The deposition is preferably carried out by a method of spraying lanthanum hexaboride powder into a plasma, composed, for example, of argon and hydrogen in the same amounts. This operation takes place at very high temperature, either at atmospheric pressure, or preferably in a rarefied atmosphere.
Le débit de poudre est de l'ordre d'un kilogramme par heure, la distance entre le plasma et la cathode étant comprise entre 30 centimètres et 1 mètre. Les caractéristiques du plasma sont les suivantes: pour un volume de gaz de l'ordre d'une dizaine de centimètres cube, le courant est de l'ordre de 400 ampères et la tension de l'ordre de 40 volts.The powder flow rate is of the order of one kilogram per hour, the distance between the plasma and the cathode being between 30 centimeters and 1 meter. The characteristics of the plasma are as follows: for a volume of gas of the order of ten cubic centimeters, the current is of the order of 400 amperes and the voltage of the order of 40 volts.
L'épaisseur de la couche d'hexaborure de lanthane sera, de préférence, comprise entre 10 et 100 micromètres. L'hexaborure de lanthane est choisi à cause de son émission thermoélectronique élevée. Mais l'évaporation de l'hexaborure de lanthane est importante quand on le chauffe. Afin de limiter la perte de matière par évaporation, on recouvre l'hexaborure de lanthane, d'un film de matériau réfractaire.The thickness of the lanthanum hexaboride layer will preferably be between 10 and 100 micrometers. Lanthanum hexaboride is chosen because of its high thermoelectronic emission. But the evaporation of lanthanum hexaboride is important when it is heated. In order to limit the loss of material by evaporation, the lanthanum hexaboride is covered with a film of refractory material.
Le matériau réfractaire est déposé de façon à former une couche compacte et homogène. Ce dépôt est réalisé, de préférence par un procédé de projection de poudre de matériau réfractaire dans un plasma, analogue à celui utilisé pour le dépôt d'hexaborure de lanthane. L'épaisseur de la couche de matériau réfractaire sera de préférence comprise entre 10 et 100 micromètres.The refractory material is deposited so as to form a compact and homogeneous layer. This deposition is carried out, preferably by a method of spraying powder of refractory material into a plasma, similar to that used for the deposition of lanthanum hexaboride. The thickness of the layer of refractory material will preferably be between 10 and 100 micrometers.
Les matériaux utilisés pour ce dépôt sont choisis réfractaires et ont une faible vitesse d'évaporation, une grande résistance à l'oxydation et au bombardement ionique. Ils n'altèrent pas les propriétés thermoémissives de l'hexaborure de lanthane. Ils sont également choisis de manière à être obtenus, à l'état fondu, sans altération de leurs propriétés physico-chimiques intrinsèques, par exemple, la stoechiométrie. Avec cette couche réfractaire, la dissipation thermique de la cathode est diminuée, ce qui signifie que le rapport émission électronique sur puissance de chauffage est sensiblement augmenté par rapport aux cathodes à l'hexaborure de lanthane de l'art antérieur. Grâce au faible coefficient de dilatation du graphite pyrolytique, la cathode ainsi réalisée est pratiquement indéformable.The materials used for this deposit are chosen to be refractory and have a low rate of evaporation, a high resistance to oxidation and to ion bombardment. They do not alter the thermoemissive properties of lanthanum hexaboride. They are also chosen so as to be obtained, in the molten state, without alteration of their intrinsic physicochemical properties, for example, stoichiometry. With this refractory layer, the heat dissipation of the cathode is reduced, which means that the ratio of electronic emission to heating power is significantly increased compared to lanthanum hexaboride cathodes of the prior art. Thanks to the low coefficient of expansion of pyrolytic graphite, the cathode thus produced is practically undeformable.
Les matériaux réfractaires pouvant convenir à ce type d'application sont nombreux. Dans un premier mode de réalisation, le matériau réfractaire est choisi parmi les borures d'un métal de transition. Ces métaux sont dans les colonnes IVA, VA, VIA, VIIA de la classification périodique des éléments telles que présentée dans l'ouvrage "Inorganic chemistry" de RB HESLOP et K. JONES édité par ELSEVIER SCIENTIFIC PUBLISHING COMP. Par exemple, on peut utiliser l'un de ces corps:
- ― le borure de titane
- TiB₂
- ― le borure de zirconium
- ZrB₂
- ― le borure d'hafnium
- HfB₂
- ― le borure de niobium
- NbB₂
- ― les borures de vanadium
- VB₂ ou V₃B₂
- ― le borure de molybdène
- MoB₂
- ― le borure de rhénium
- ReB₃
There are many refractory materials that may be suitable for this type of application. In a first embodiment, the refractory material is chosen from among the borides of a transition metal. These metals are in columns IVA, VA, VIA, VIIA of the periodic classification of the elements as presented in the work "Inorganic chemistry" by RB HESLOP and K. JONES edited by ELSEVIER SCIENTIFIC PUBLISHING COMP. For example, we can use one of these bodies:
- - titanium boride
- TiB₂
- - zirconium boride
- ZrB₂
- - hafnium boride
- HfB₂
- - niobium boride
- NbB₂
- - vanadium borides
- VB₂ or V₃B₂
- - molybdenum boride
- MoB₂
- - rhenium boride
- ReB₃
Dans un second mode de réalisation, le matériau réfractaire est un composé de bore et d'un métal de la mine du platine:In a second embodiment, the refractory material is a compound of boron and a metal of the platinum mine:
Par exemple, on peut utiliser l'un de ces corps:
- ― les borures de ruthénium
- RuB ou Ru₂B₃
- ― les borures de rhodium
- Rh₇B₃ ou RhB
For example, we can use one of these bodies:
- - ruthenium borides
- RuB or Ru₂B₃
- - rhodium borides
- Rh₇B₃ or RhB
Dans un troisième mode de réalisation, le matériau réfractaire est un composé de silicium et de certains métaux, tels que:
- ― les siliciures de molybdène
- MoSi₂ ou Mo₅Si₃
- ― les siliciures de niobium
- NbSi₂ ou Nb₅Si₃
- ― les siliciures de vanadium
- V₃Si, V₅Si₃ ou VSi₂
- ― le siliciure de tungstène
- WSi₂
- ― les siliciures de rhénium
- ReSi₂ ou Re₅Si₃
- ― les siliciures de rhodium
- Rh₂Si ou RhSi
- ― le siliciure de zirconium
- Zr₅Si₄
- ― les siliciures d'iridium
- Ir₃Si₂ ou IrSi
- ― les siliciures de ruthénium
- Ru₂Si₃ ou RuSi
In a third embodiment, the refractory material is a compound of silicon and certain metals, such as:
- - molybdenum silicides
- MoSi₂ or Mo₅Si₃
- - niobium silicides
- NbSi₂ or Nb₅Si₃
- - vanadium silicides
- V₃Si, V₅Si₃ or VSi₂
- - tungsten silicide
- WSi₂
- - rhenium silicides
- ReSi₂ or Re₅Si₃
- - rhodium silicides
- Rh₂Si or RhSi
- - zirconium silicide
- Zr₅Si₄
- - iridium silicides
- Ir₃Si₂ or IrSi
- - ruthenium silicides
- Ru₂Si₃ or RuSi
Dans un quatrième mode de réalisation, le matériau réfractaire est un composé de carbone et de certains métaux, tels que:
- ― le carbure de bérylium
- Be₂C
- ― le carbure de titane
- TiC
- ― le carbure de vanadium
- V₂C
- ― le carbure de zirconium
- ZrC
In a fourth embodiment, the refractory material is a compound of carbon and certain metals, such as:
- - berylium carbide
- Be₂C
- - titanium carbide
- Tic
- - vanadium carbide
- V₂C
- - zirconium carbide
- ZrC
On pourrait envisager que la cathode soit constituée directement à partir du matériau émissif (hexaborure de lanthane par exemple) recouvert de la couche réfractaire, sans support de graphite. On peut envisager aussi que le support soit autre qu'un graphite.It could be envisaged that the cathode should be formed directly from the emissive material (lanthanum hexaboride for example) covered with the refractory layer, without graphite support. It is also conceivable that the support is other than a graphite.
La présente invention n'est pas limitée aux exemples donnés pour la composition du matériau thermoémissif et du matériau réfractaire.The present invention is not limited to the examples given for the composition of the thermoemissive material and of the refractory material.
Claims (13)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR8802364A FR2627897B1 (en) | 1988-02-26 | 1988-02-26 | DIRECT HEATING CATHODE IN THERMOEMISSIF MATERIAL |
FR8802364 | 1988-02-26 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0330543A1 EP0330543A1 (en) | 1989-08-30 |
EP0330543B1 true EP0330543B1 (en) | 1992-01-22 |
Family
ID=9363662
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19890400375 Expired - Lifetime EP0330543B1 (en) | 1988-02-26 | 1989-02-09 | Directly heated cathode manufactured from thermally emissive material |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0330543B1 (en) |
JP (1) | JPH01292726A (en) |
DE (1) | DE68900732D1 (en) |
FR (1) | FR2627897B1 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2299137B (en) * | 1995-03-20 | 1999-04-28 | Matra Marconi Space Uk Ltd | Ion thruster |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
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GB1045396A (en) * | 1965-07-23 | 1966-10-12 | Standard Telephones Cables Ltd | Thermionic cathodes |
JPS5514646A (en) * | 1978-07-17 | 1980-02-01 | Toshiba Corp | Electron gun |
-
1988
- 1988-02-26 FR FR8802364A patent/FR2627897B1/en not_active Expired - Lifetime
-
1989
- 1989-02-09 DE DE8989400375T patent/DE68900732D1/en not_active Expired - Fee Related
- 1989-02-09 EP EP19890400375 patent/EP0330543B1/en not_active Expired - Lifetime
- 1989-02-22 JP JP1040421A patent/JPH01292726A/en active Pending
Also Published As
Publication number | Publication date |
---|---|
DE68900732D1 (en) | 1992-03-05 |
FR2627897A1 (en) | 1989-09-01 |
FR2627897B1 (en) | 1990-06-22 |
JPH01292726A (en) | 1989-11-27 |
EP0330543A1 (en) | 1989-08-30 |
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