EP0003937A2 - Cathode for an electron gun - Google Patents

Cathode for an electron gun Download PDF

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Publication number
EP0003937A2
EP0003937A2 EP79400126A EP79400126A EP0003937A2 EP 0003937 A2 EP0003937 A2 EP 0003937A2 EP 79400126 A EP79400126 A EP 79400126A EP 79400126 A EP79400126 A EP 79400126A EP 0003937 A2 EP0003937 A2 EP 0003937A2
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EP
European Patent Office
Prior art keywords
pellet
cathode according
cathode
resistor
resistance
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Granted
Application number
EP79400126A
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German (de)
French (fr)
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EP0003937A3 (en
EP0003937B1 (en
Inventor
Gérard Marhic
Philippe Martin
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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Publication of EP0003937A2 publication Critical patent/EP0003937A2/en
Publication of EP0003937A3 publication Critical patent/EP0003937A3/en
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Publication of EP0003937B1 publication Critical patent/EP0003937B1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J3/00—Details of electron-optical or ion-optical arrangements or of ion traps common to two or more basic types of discharge tubes or lamps
    • H01J3/02—Electron guns
    • H01J3/027—Construction of the gun or parts thereof
    • 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
    • H01J1/16—Cathodes heated directly by an electric current characterised by the shape

Definitions

  • the present invention which results from the work carried out by Mr. sympathy MARHIC of the AUTOGENE FRENCH WELDING essentially relates to a cathode for electronic gun comprising at least one pellet made of a material capable of emitting, at high temperature, electrons, for example lanthanum hexaboride (LaE6) and at least one heating resistor made of a material with high electrical resistivity, for example pyrolitic graphite, said pellet and said resistance being traversed, in series, by an electric heating current.
  • LaE6 lanthanum hexaboride
  • the cathode constitutes the electron generator of cannons mounted on various devices using electron beams.
  • the emitted electrons are subjected to the action of the Wehnelt which regulates the power of the beam, accelerated by a voltage established between the cathode and an anode and finally focused by a magnetic lens which makes them converge on a practically point surface.
  • Cathodes of the aforementioned type are already known which are essentially constituted by a LaB6 emitting pellet having, at least in part, the shape of a rectangular parallelepiped and by two blocks of pyrolitic graphite, cubic in shape, placed on either side. other of the emitting tablet.
  • the whole is mounted on a fixed support comprising two metal arms connected to a source of electrical energy, these two arms being in direct contact with the graphite blocks and pressing them against the emitting pad which is interposed between them.
  • the invention aims to overcome these drawbacks and offers this offer a cathode whose pellet is in the form of a hollow part mounted on a support integral with the barrel, in which is engaged and against a wall of which is applied the resistance of pyrolitic graphite.
  • Heat transmission is therefore not only by ccnduction between the contacting surfaces but also by radiation since most of the radiation emitted by the resistor meets the pellet. This results in a better efficiency of the cathode.
  • the pellet and the resistor are in the form of a part of revolution, the axes of these parts being in coincidence when the resistor is engaged in the pellet.
  • the pellet is in the form of a cup provided with a flat bottom wall and a side wall flaring from said bottom wall and the resistance is in the form of a truncated cone whose small base is applied against the bottom of the cup.
  • the cathode comprises a sheath made of an electrically conductive and chemically inert material with respect to LaB6, for example in graphite and inside which said pellet is inserted.
  • This sheath is mounted directly on the aforementioned support.
  • the sheath makes it possible to maintain the pellet without it being necessary to weld it to the support, thus eliminating any chemical reaction between LaB6 and the material of said support.
  • the sheath also ensures the conduction of the heating current.
  • the resistance is applied against the bottom wall of the pellet by elastic means.
  • the cathode according to the invention is housed inside a cylindrical barrel shown schematically in 2 and fixed to a support plate integral with the latter and shown diagrammatically in 3.
  • the barrel 2 comprises, in a manner known per se, a certain number of other elements, in particular one or more magnetic lenses, an anode and a Wehnelt, only the latter being represented in 4.
  • the barrel 2 and all of the elements which it comprises admit the axis XX 'as the axis of revolution.
  • the cathode 1 essentially consists of an emitting patch 10 made of LaB6, housed in a sheath 11 mounted on a support 12 fixed itself on the support plate 3 of the barrel 2 and of a heating resistor 14.
  • the patch and the sheath are housed in the central opening 4a of Wehnelt 4.
  • the emitting pad 10 is constituted by a hollow part of revolution and has the shape of a bowl provided with a flat bottom wall 10a and a side wall 10b flared outwards.
  • the sheath 11 in which the pellet 10 is housed is made of graphite and has the shape of a tubular cylinder of revolution. It is provided, at its upper end, with a lip or the like 11a, projecting inwards, against which the external face 10c of the patch 10 is supported and at its lower part, with a flange 11b projecting outwards which rests on the support 12.
  • the support 12 is constituted by two front and rear frustoconical capsules 12a and 12b respectively, these capsules being joined by their large bases and fixed by the latter to the support plate 3.
  • the resistor 14 made of pyrolitic graphite, has the general shape of a truncated cone whose small and large bases are designated respectively by 14a and 14b and is further provided with an axial recess 14c.
  • the resistor 14 is in abutment, by its small base 14a in the form of a crown, against the flat bottom 10a of the pellet.
  • the bottom of 10a and the small base 14a are given substantially equal diameters and the conical resistor 14 an angle at the top substantially less than that of the flared edge 10b of the patch.
  • the resistance 14 is applied against the pellet by a rod or pusher 15 provided, at its upper end, with a head 15a resting on its large base 14b.
  • the pusher 15 is secured, by means of a first metal ring 16, to a first tubular element 17 of axis XX ′ inside which it is housed, this first tubular element 17 being itself secured by through an insulating ring 18, a second tubular element 19 of axis XX 'in which it is housed.
  • the tubular element 19 is itself mounted on a support rod 20.
  • the plunger 15 and the tubular elements 17 and 19 constitute a rigid assembly which has the function of transmitting to the resistor 14 the thrust of elastic means.
  • These elastic means consist of a corrugated sheath or bellows 23 of axis XX ′ and surrounding the annular element 19.
  • the sheath 23 is fixed, at its upper part 23 a, to the capsule 12 b of the support 12 and is provided, at its lower end 23b of an annular stop 24 which bears, by means of an insulating ring 25, for example made of alumina against the end of the element 19.
  • the assembly constituted by the pusher 15 and the tubular elements 17 and 19 also has the function of creating, between the resistance heater 14 whose temperature is of the order of 1700 ° and the corrugated sheath 23, a substantial decrease in temperature so that said corrugated sheath as well as the support rod 20 reach a temperature of the order of 200 to 300 ° C. .
  • the cathode is also provided with frustoconical screens 26 and 27 located respectively inside and outside the capsule 12.
  • the elastic support provided by the corrugated sheath 23 protects the pellet and the resistance from mechanical stresses encountered with rigid systems, which makes it possible to significantly increase the service life of the cathode. .
  • the invention applies to all devices using electron beam generators, in particular to electron bombardment welding devices and electron microscopes.

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  • Solid Thermionic Cathode (AREA)
  • Electron Sources, Ion Sources (AREA)
  • Thermistors And Varistors (AREA)

Abstract

La cathode comporte une pastille en hexaborure de lanthane et une résistance chauffante en graphite pyrolitique parcourues par un courant électrique de chauffage. La pastille 10 présente la forma d'une pièce creuse de révolution dans laquelle est engagée, et contre une paroi 10a de laquelle est appliquée, la résistance 14, également de révolution. L'invention s'applique en particulier aux appareils de soudage par bombardement électronique.The cathode comprises a lanthanum hexaboride pellet and a pyrolitic graphite heating resistor through which an electric heating current flows. The pellet 10 has the form of a hollow part of revolution in which is engaged, and against a wall 10a of which is applied, the resistance 14, also of revolution. The invention applies in particular to apparatuses for welding by electronic bombardment.

Description

La présente invention qui résulte des travaux effectués par Monsieur Gérard MARHIC de la SOUDURE AUTOGENE FRANCAISE concerne essentiellement une cathode pour canon électronique comportant au moins une pastille faite en un matériau susceptible d'émettre, à haute température, des électrons, par exemple de l'hexaborure de lanthane (LaE6) et au moins une résistance chauffante faite en un matériau à haute résistivité électrique, par exemple du graphite pyrolitique, ladite pastille et ladite résistance étant parcourues, en série, par un courant électrique de chauffage.The present invention which results from the work carried out by Mr. Gérard MARHIC of the AUTOGENE FRENCH WELDING essentially relates to a cathode for electronic gun comprising at least one pellet made of a material capable of emitting, at high temperature, electrons, for example lanthanum hexaboride (LaE6) and at least one heating resistor made of a material with high electrical resistivity, for example pyrolitic graphite, said pellet and said resistance being traversed, in series, by an electric heating current.

On sait que la cathode constitue le générateur d'électrons des canons montés sur divers appareils utilisant des faisceaux électroniques. Les électrons émis sont soumis à l'action du Wehnelt qui règle la puissance du faisceau, accélérés par une tension établie entre la cathode et une anode et enfin focalisés par une lentille magnétique qui les fait converger sur une surface pratiquement ponctuelle.It is known that the cathode constitutes the electron generator of cannons mounted on various devices using electron beams. The emitted electrons are subjected to the action of the Wehnelt which regulates the power of the beam, accelerated by a voltage established between the cathode and an anode and finally focused by a magnetic lens which makes them converge on a practically point surface.

On connaît déjà des cathodes du type susmentionné qui sont constituées essentiellement par une pastille émettrice en LaB6 ayant, en partie au moins, la forme d'un parallélépipède rectangle et par deux blocs en graphite pyrolitique, de forme cubique, placés de part et d'autre de la pastille émettrice. Le tout est monté sur un support fixe comportant deux bras métalliques reliés à une source d'énergie électrique, ces deux bras étant en contact direct avec les blocs de graphite et les pressant contre la pastille émettrice qui est intercalée entre eux.Cathodes of the aforementioned type are already known which are essentially constituted by a LaB6 emitting pellet having, at least in part, the shape of a rectangular parallelepiped and by two blocks of pyrolitic graphite, cubic in shape, placed on either side. other of the emitting tablet. The whole is mounted on a fixed support comprising two metal arms connected to a source of electrical energy, these two arms being in direct contact with the graphite blocks and pressing them against the emitting pad which is interposed between them.

Ces cathodes connues présentent certains inconvénients :

  • - la transmission de la chaleur engendrée par effet Joule dans le graphite pyrolitique vers la pastille en LaB6, ne peut se faire pratiquement que par les surfaces en contact, puisque, en raison de la géométrie de l'ensemble; la plus grande partie du rayonnement émis par les blocs en graphite ne peut atteindre la pastille. Il en résulte que ces cathodes ont un rendement thermique défectueux.
  • - le montage de la pastille et des blocs entre deux bras rigides peut entraîner, en raison des dilatations thermiques, des contraintes mécaniques excessives ; il est difficile, avec une telle configuration non de révolution de la cathode, d'obtenir un bon positionnement de la pastille émettrice, ceci en raison des variations thermiques et des dilatations.
These known cathodes have certain drawbacks:
  • - the transmission of the heat generated by the Joule effect in pyrolitic graphite to the LaB6 pellet can only be practically done by the surfaces in contact, since, due to the geometry of the assembly; most of the radiation emitted by the graphite blocks cannot reach the pellet. As a result, these cathodes have a defective thermal efficiency.
  • - the mounting of the pad and the blocks between two rigid arms can cause, due to thermal expansion, excessive mechanical stresses; it is difficult, with such a non-revolution configuration of the cathode, to obtain a good positioning of the emitting pellet, this because of thermal variations and expansions.

L'invention a pour but de pallier ces inconvénients et propose à cet offet une cathode dont la pastille se présente sous forme d'une pièce creuse montée sur un support solidaire du canon, dans laquelle est engagée et contre une paroi de laquelle est appliquée la résistance de graphite pyrolitique.The invention aims to overcome these drawbacks and offers this offer a cathode whose pellet is in the form of a hollow part mounted on a support integral with the barrel, in which is engaged and against a wall of which is applied the resistance of pyrolitic graphite.

La transmission de chaleur se fait donc non seulement par ccnduction entre les surfaces en contact mais également par rayonnement puisque la plus grande partie du rayonnement émis par la résistance rencontre la pastille. Il en résulte un meilleur rendement de la cathode.Heat transmission is therefore not only by ccnduction between the contacting surfaces but also by radiation since most of the radiation emitted by the resistor meets the pellet. This results in a better efficiency of the cathode.

Selon une autre caractéristique de l'invention, la pastille et la résistance se présentent sous forme d'une pièce de révolution, les axes de ces pièces étant en coïncidence lorsque la résistance est engagée dans la pastille.According to another characteristic of the invention, the pellet and the resistor are in the form of a part of revolution, the axes of these parts being in coincidence when the resistor is engaged in the pellet.

La symétrie de révolution permet d'obtenir une répartition plus homogène de la chaleur rayonnée par la résistance donc une température homogène de la pastille, elle simplifie en outre la fatrication.The symmetry of revolution makes it possible to obtain a more homogeneous distribution of the heat radiated by the resistance therefore a homogeneous temperature of the pellet, it also simplifies the fatufacturing.

La pastille se présente sous forme d'une coupelle munie d'une paroi de fond plane et d'une paroi latérale s'évasant à partir de ladite paroi de fond et la résistance se présente sous la forme d'un tronc de cône dont la petite base est appliquée contre le fond de la coupelle.The pellet is in the form of a cup provided with a flat bottom wall and a side wall flaring from said bottom wall and the resistance is in the form of a truncated cone whose small base is applied against the bottom of the cup.

Cette forme donnée à la pastille et à la résistance facilite leur montage ainsi que leur centrage relatif.This shape given to the pad and to the resistance facilitates their mounting as well as their relative centering.

Belon encore une autre caractéristique de l'invention, la cathode comporte un fourreau fait en un matériau électriquement conducteur et chimiquement inerte vis à vis du LaB6, par exemple en graphite et à l'intérieur duquel est insérée ladite pastille. Ce fourreau est monté directement sur le support précité.According to yet another characteristic of the invention, the cathode comprises a sheath made of an electrically conductive and chemically inert material with respect to LaB6, for example in graphite and inside which said pellet is inserted. This sheath is mounted directly on the aforementioned support.

Le fourreau permet de maintenir la pastille sans qu'il soit nécessaire de la souder au support, supprimant ainsi toute réaction chimique entre le LaB6 et le matériau dudit support. Le fourreau assure en outre la conduction du courant de chauffage.The sheath makes it possible to maintain the pellet without it being necessary to weld it to the support, thus eliminating any chemical reaction between LaB6 and the material of said support. The sheath also ensures the conduction of the heating current.

Toujours selon l'invention, la résistance est appliquée contre la paroi de fond de la pastille par des moyens élastiques.Still according to the invention, the resistance is applied against the bottom wall of the pellet by elastic means.

L'utilisation de moyens élastiques pour maintenir en place la résistance et la pastille permet d'éviter la formation de contraintes mécaniques sous l'effet des dilatations thermiques.The use of elastic means to hold the resistance and the pad in place makes it possible to avoid the formation of mechanical stresses under the effect of thermal expansions.

D'autres caractéristiques et avantages de l'invention apparaîtront au cours de la description qui va suivre.Other characteristics and advantages of the invention will emerge during the description which follows.

Le dessin annexé, donné uniquement à titre d'exemple ncn lini- tatif, représente schématiquement et en coupe une cathode selon un mode de réalisation de l'invention.The appended drawing, given solely by way of an illustrative example, shows schematically and in section a cathode according to an embodiment of the invention.

Selon le mode de réalisation représenté, la cathode selon l'invention, désignée d'une façon générale par la référence 1, est logée à l'intérieur d'un canon cylindrique représenté schématiquement en 2 et fixée à une platine porteuse solidaire de ce dernier et représentée schématiquement en 3. Outre la cathode 1, le canon 2 comporte, de façon connue en soi, un certain nombre d'autres éléments, en particulier une ou plusieurs lentilles magnétiques, une anode et un Wehnelt, seul ce dernier étant représenté en 4. Le canon 2 ainsi que l'ensemble des éléments qu'il comporte admettent l'axe XX' comme axe de révolution.According to the embodiment shown, the cathode according to the invention, generally designated by the reference 1, is housed inside a cylindrical barrel shown schematically in 2 and fixed to a support plate integral with the latter and shown diagrammatically in 3. In addition to the cathode 1, the barrel 2 comprises, in a manner known per se, a certain number of other elements, in particular one or more magnetic lenses, an anode and a Wehnelt, only the latter being represented in 4. The barrel 2 and all of the elements which it comprises admit the axis XX 'as the axis of revolution.

La cathode 1 se compose essentiellement d'une pastille émettrice 10 en LaB6, logée dans un fourreau 11 monté sur un support 12 fixé lui-même sur la platine porteuse 3 du canon 2 et d'une résistance chauffante 14. La pastille et le fourreau sont logés dans l'orifice central 4a du Wehnelt 4.The cathode 1 essentially consists of an emitting patch 10 made of LaB6, housed in a sheath 11 mounted on a support 12 fixed itself on the support plate 3 of the barrel 2 and of a heating resistor 14. The patch and the sheath are housed in the central opening 4a of Wehnelt 4.

La pastille émettrice 10 est constituée par une pièce creuse de révolution et présente la forme d'une cuvette munie d'une paroi de fond 10a plane et d'une paroi latérale 10b évasée vers l'extérieur.The emitting pad 10 is constituted by a hollow part of revolution and has the shape of a bowl provided with a flat bottom wall 10a and a side wall 10b flared outwards.

Le fourreau 11 dans lequel est logée la pastille 10, est en graphite et présente la forme d'un cylindre tubulaire de révolution. Il est muni, à son extrémité supérieure, d'une lèvre ou analogue 11a, en saillie vers l'intérieur, contre lequel prend appui la face extérieure 10c de la pastille 10 et à sa partie inférieure, d'un rebord 11b en saillie vers l'extérieur qui prend appui sur le support 12.The sheath 11 in which the pellet 10 is housed is made of graphite and has the shape of a tubular cylinder of revolution. It is provided, at its upper end, with a lip or the like 11a, projecting inwards, against which the external face 10c of the patch 10 is supported and at its lower part, with a flange 11b projecting outwards which rests on the support 12.

Le support 12 est constitué par deux capsules tronconiques avant et arrière 12a et 12b respectivement, ces capsules étant réunies par leurs grandes bases et fixées par ces dernières à la platine porteuse 3.The support 12 is constituted by two front and rear frustoconical capsules 12a and 12b respectively, these capsules being joined by their large bases and fixed by the latter to the support plate 3.

La résistance 14, en graphite pyrolitique, présente la forme générale d'un tronc de cône dont la petite et la grande base sont désignées respectivement par 14a et 14b et est munie en outre d'un évidement axial 14c. La résistance 14 est en appui, par sa petite base 14a en forme de couronne, contre le fond plat 10a de la pastille. Afin de faciliter la mise en place et le centrage de la résistance 14 dans la pastille 10, on donne au fond de 10a et à la petite base 14a des diamètres sensiblement égaux et à la résistance conique 14 un angle au sommet sensiblement inférieur à celui du bord évasé 10b de la pastille.The resistor 14, made of pyrolitic graphite, has the general shape of a truncated cone whose small and large bases are designated respectively by 14a and 14b and is further provided with an axial recess 14c. The resistor 14 is in abutment, by its small base 14a in the form of a crown, against the flat bottom 10a of the pellet. In order to facilitate the positioning and centering of the resistor 14 in the patch 10, the bottom of 10a and the small base 14a are given substantially equal diameters and the conical resistor 14 an angle at the top substantially less than that of the flared edge 10b of the patch.

La résistance 14 est appliquée contre la pastille par une tige ou poussoir 15 muni, à son extrémité supérieure, d'une tête 15a en appui sur sa grande base 14b. Le poussoir 15 est solidaire, par l'intermédiaire d'une première bague métallique 16, d'un premier élément tubulaire 17 d'axe XX' à l'intérieur duquel il est logé, ce premier élément tubulaire 17 étant solidaire lui-même par l'intermédiaire d'une bague isolante 18, d'un second élément tubulaire 19 d'axe XX' dans lequel il est logé. L'élément tubulaire 19 est monté lui-même sur une tige de supportage 20.The resistance 14 is applied against the pellet by a rod or pusher 15 provided, at its upper end, with a head 15a resting on its large base 14b. The pusher 15 is secured, by means of a first metal ring 16, to a first tubular element 17 of axis XX ′ inside which it is housed, this first tubular element 17 being itself secured by through an insulating ring 18, a second tubular element 19 of axis XX 'in which it is housed. The tubular element 19 is itself mounted on a support rod 20.

Le poussoir 15 et les éléments tubulaires 17 et 19 constituent un ensemble rigide qui a pour fonction de transmettre à la résistance 14 la poussée de moyens élastiques. Ces moyens élastiques sont constitués par une gaine annelée ou soufflet 23 d'axe XX' et entourant l'élément annulaire 19. La gaine 23 est fixée, à sa partie supérieure 23 a, à la capsule 12 b du support 12 et est munie, à son extrémité inférieure 23b d'une butée annulaire 24 qui prend appui, par l'intermédiaire d'une bague isolante 25, par exemple en alumine contre l'extrémité de l'élément 19.The plunger 15 and the tubular elements 17 and 19 constitute a rigid assembly which has the function of transmitting to the resistor 14 the thrust of elastic means. These elastic means consist of a corrugated sheath or bellows 23 of axis XX ′ and surrounding the annular element 19. The sheath 23 is fixed, at its upper part 23 a, to the capsule 12 b of the support 12 and is provided, at its lower end 23b of an annular stop 24 which bears, by means of an insulating ring 25, for example made of alumina against the end of the element 19.

L'ensemble constitué par le poussoir 15 et les éléments tubulaires 17 et 19 a également pour fonction de créer, entre la résistance chauffante 14 dont la température est de l'ordre de 1700° et la gaine annelée 23, une diminution sensible de température de façon que ladite gaine annelée ainsi que la tige de supportage 20 atteignent une température de l'ordre de 200 à 300°C.The assembly constituted by the pusher 15 and the tubular elements 17 and 19 also has the function of creating, between the resistance heater 14 whose temperature is of the order of 1700 ° and the corrugated sheath 23, a substantial decrease in temperature so that said corrugated sheath as well as the support rod 20 reach a temperature of the order of 200 to 300 ° C. .

Pour limiter la transmission de chaleur par rayonnement de la résistance 14 vers le canon, la cathode est munie en outre d'écrans 26 et 27 tronconiques situés respectivement à l'intérieur et à l'extérieur de la capsule 12.To limit the transmission of heat by radiation from the resistor 14 to the barrel, the cathode is also provided with frustoconical screens 26 and 27 located respectively inside and outside the capsule 12.

On voit que, grâce au positionnement relatif de la pastille 10 et de la résistance 14 et grâce à la forme de révolution donnée à ces deux pièces, pratiquement toute l'énergie rayonnée par la résistance, en particulier par sa face conique, est absorbée par la pastille 10, en particulier par sa paroi évasée 10b, réduisant ainsi au maximum les pertes d'énergie thermique.We see that, thanks to the relative positioning of the patch 10 and of the resistor 14 and thanks to the shape of revolution given to these two parts, practically all the energy radiated by the resistor, in particular by its conical face, is absorbed by the patch 10, in particular by its flared wall 10b, thus reducing to the maximum the losses of thermal energy.

Par ailleurs, l'appui élastique assuré par la gaine annelée 23 met la pastille et la résistance à l'abri des contraintes mécaniques que l'on rencontre avec les systèmes rigides, ce qui permet d'augmenter sensiblement la durée de vie de la cathode.Furthermore, the elastic support provided by the corrugated sheath 23 protects the pellet and the resistance from mechanical stresses encountered with rigid systems, which makes it possible to significantly increase the service life of the cathode. .

L'invention s'applique à tous les appareils utilisant des générateurs de faisceaux électroniques en particulier aux appareils de soudage par bombardement d'électrons et aux microscopes électroniques.The invention applies to all devices using electron beam generators, in particular to electron bombardment welding devices and electron microscopes.

De nombreuses variantes pourraient être apportées au mode de réalisation décrit et représenté, sans pour autant sortir du cadre de l'invention.Many variants could be made to the embodiment described and shown, without going beyond the ambit of the invention.

Claims (10)

1.-Cathode pour canon électronique comportant au moins une pastille faite en un matériau susceptible d'émettre, à haute température, des électrons, par exemple de l'hexabcrure de lanthane et au moins une résistance chauffante faite en un matériau à haute résistivité électrique, par exemple du graphite pyrolitique, ladite pastille et ladite résistance étant parcourues, en série, par un courant électrique de chauffage, caractérisée en ce que la pastille précitée (10) se présente sous forme d'une pièce creuse montée sur un support (12) solidaire du canon (2) dans laquelle est engagée et contre une paroi (10a) de laquelle est appliquée la résistance précitée (14).1.-Cathode for electronic gun comprising at least one pellet made of a material capable of emitting, at high temperature, electrons, for example lanthanum hexabcrure and at least one heating resistor made of a material with high electrical resistivity , for example pyrolitic graphite, said pellet and said resistor being traversed, in series, by an electric heating current, characterized in that the aforementioned pellet (10) is in the form of a hollow part mounted on a support (12 ) integral with the barrel (2) in which is engaged and against a wall (10a) of which the above-mentioned resistance (14) is applied. 2.-Cathode selon la revendication 1, caractérisée en ce que la pastille (10) et la résistance (14) précitées présentent chacune sous forme d'une pièce de révolution, les axes de ces pièces étant en coïncidence lorsque la résistance est engagée dans la pastille.2. Cathode according to claim 1, characterized in that the aforementioned pellet (10) and the resistance (14) each have the form of a part of revolution, the axes of these parts being in coincidence when the resistance is engaged in the tablet. 3.-Cathode selon la revendication 2, caractérisée en ce que la pastille (10) se présente scus forme d'une coupelle munie d'une paroi de fond (10a) plane et d'une paroi latérale (10b) s'évasant à partir de ladite paroi de fond et en ce que la résistance (14) se présente sous forme d'un tronc de cône dont la plus petite base (14a) est appliquée contre la paroi de fond (10a) de ladite coupelle.3. Cathode according to claim 2, characterized in that the pellet (10) is presented in the form of a cup provided with a flat bottom wall (10a) and a side wall (10b) which widens out. from said bottom wall and in that the resistance (14) is in the form of a truncated cone, the smallest base (14a) of which is applied against the bottom wall (10a) of said cup. 4.-Cathode selon la revendication 3, caractérisée en ce que la résistance (14) précitée en forme de tronc de cône est traversée par un évidement axial (14c), sa petite base (14a), appliquée sur le fond (10a) de la pastille présentant la forme d'une couronne.4. Cathode according to claim 3, characterized in that the aforesaid resistor (14) in the form of a truncated cone is crossed by an axial recess (14c), its small base (14a), applied to the bottom (10a) of the pastille having the shape of a crown. 5.-Cathode selon la revendication 1, caractérisée en ce qu'elle comporte un fourreau (11) fait en un matériau électriquement conducteur tel que le graphite et à l'intérieur duquel est insérée ladite pastille (10), ce fourreau étant monté directement sur le support précité (12).5. Cathode according to claim 1, characterized in that it comprises a sheath (11) made of an electrically conductive material such as graphite and inside which is inserted said pellet (10), this sheath being mounted directly on the aforementioned support (12). 6.-Cathode selon les revendications 3 et 5, caractérisée en ce que le fourreau (11) précité se présente sous la forme d'un cylindre tubulaire de révolution monté sur le support (12) précité et muni, à l'une de ses extréulités, d'une lèvre ou analogue interne (11a), sur laquelle prend appui ladite pastille (10).6. Cathode according to claims 3 and 5, characterized in that the sheath (11) mentioned above is in the form of a tubular cylinder of revolution mounted on the support (12) above and provided, at one of its ends, an internal lip or the like (11a), on which said pellet (10) bears. 7.-Cathode selon la revendication 1, caractérisée en ce que la résistance (14) précitée est appliquée contre la paroi de fond de la pastille (10) par des moyens élastiques.7.-Cathode according to claim 1, characterized in that the resistance (14) above is applied against the bottom wall of the patch (10) by elastic means. 8.-Cathode selon la revendication 7, caractérisée en ce que les noyens élastiques précités sont constitués par un élément tubulairs annelé (23) dont les extrémités sont solidaires respectivement du support (12) de la cathode et d'une tige (15) en contact avec la résistance (14).8. Cathode according to claim 7, characterized in that the aforesaid elastic cores consist of a ringed tubular element (23) whose ends are respectively secured to the support (12) of the cathode and a rod (15) in contact with the resistor (14). 9.-Cathode selon la revendication 8, caractérisée en ce que les extrémités de l'élément tubulaire annelé (23) et de la tige (15) sont rendues solidaires l'une de l'autre par l'intemédiaire d'éléments tubulaires rigides coaxiaux (17,19) dans lesquels est logée ladite tige (15) et logés eux-mêmes dans ledit élément annelé (23).9. Cathode according to claim 8, characterized in that the ends of the ringed tubular element (23) and of the rod (15) are made integral with one another by means of rigid tubular elements coaxial (17,19) in which is housed said rod (15) and housed themselves in said corrugated element (23). 10.-Cathode selon les revendications 8 et 9, caractérisée en ce qu'elle est munie d'écrans (26, 27) prévus pour intercepter le rayonnement thermique, lesdits écrans étant montés sur ledit support (12) et sur lesdits éléments tubulaires rigides (17) au voisinage de la résistance (14).10.-Cathode according to Claims 8 and 9, characterized in that it is provided with screens (26, 27) provided for intercepting thermal radiation, said screens being mounted on said support (12) and on said rigid tubular elements (17) in the vicinity of the resistor (14).
EP79400126A 1978-03-01 1979-02-28 Cathode for an electron gun Expired EP0003937B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR7805813A FR2418964A1 (en) 1978-03-01 1978-03-01 CATHODE FOR ELECTRONIC CANNON
FR7805813 1978-03-01

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EP0003937A2 true EP0003937A2 (en) 1979-09-05
EP0003937A3 EP0003937A3 (en) 1979-09-19
EP0003937B1 EP0003937B1 (en) 1980-10-15

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EP (1) EP0003937B1 (en)
JP (1) JPS54125959A (en)
DE (1) DE2960025D1 (en)
FR (1) FR2418964A1 (en)

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FR2520553A1 (en) * 1982-01-22 1983-07-29 Cameca ELECTRONIC OPTICAL APPARATUS COMPRISING PYROLYTIC GRAPHITE ELEMENTS
US4673842A (en) * 1985-09-03 1987-06-16 General Electric Company Graphite cathode cup for gridded x-ray tubes
US5015908A (en) * 1989-01-23 1991-05-14 Varian Associates, Inc. Fast warm-up cathode for high power vacuum tubes
US5480527A (en) * 1994-04-25 1996-01-02 Vapor Technologies, Inc. Rectangular vacuum-arc plasma source
CN103094019A (en) * 2013-01-21 2013-05-08 江苏达胜加速器制造有限公司 Filament used for microcurrent electronic gun

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DE2960025D1 (en) 1981-01-22
JPS54125959A (en) 1979-09-29
FR2418964A1 (en) 1979-09-28
FR2418964B1 (en) 1980-09-05
EP0003937A3 (en) 1979-09-19
EP0003937B1 (en) 1980-10-15
US4220889A (en) 1980-09-02

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