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EP0824758B1 - Grid electron gun - Google Patents

Grid electron gun Download PDF

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Publication number
EP0824758B1
EP0824758B1 EP96914252A EP96914252A EP0824758B1 EP 0824758 B1 EP0824758 B1 EP 0824758B1 EP 96914252 A EP96914252 A EP 96914252A EP 96914252 A EP96914252 A EP 96914252A EP 0824758 B1 EP0824758 B1 EP 0824758B1
Authority
EP
European Patent Office
Prior art keywords
grid
electron gun
cathode
gun according
sphere
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
Application number
EP96914252A
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German (de)
French (fr)
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EP0824758A1 (en
Inventor
Guy Thomson-CSF SCPI CLERC
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Thales Electron Devices SA
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Thales Electron Devices SA
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Publication of EP0824758A1 publication Critical patent/EP0824758A1/en
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
    • H01J25/02—Tubes with electron stream modulated in velocity or density in a modulator zone and thereafter giving up energy in an inducing zone, the zones being associated with one or more resonators
    • H01J25/04—Tubes having one or more resonators, without reflection of the electron stream, and in which the modulation produced in the modulator zone is mainly density modulation, e.g. Heaff tube
    • 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
    • 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
    • H01J23/06—Electron or ion guns
    • H01J23/07—Electron or ion guns producing a hollow cylindrical beam
    • 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

Definitions

  • the field of the invention is that of electronic tubes and especially those with longitudinal electron beams with a grid such as IOT (abbreviation of the English terms Inductive Output Tube).
  • An IOT has an electron gun that emits a beam of electrons, a resonant cavity which is crossed by the beam and a collector which collects the beam electrons as they exit the cavity.
  • the electron gun has a cathode generally concave and shaped like a portion of a sphere, a control grid and a anode.
  • the concave side of the cathode emits electrons when it is brought to high temperature. Electrons pass through the control grid and are attracted to the anode and then enter the resonant cavity in forming a longitudinal beam, see EP-A-0 578 525.
  • the control grid is used to modulate the emission of electrons from so as to group them into packages before entering the cavity resonant.
  • the cathode is generally made by a porous body impregnated with an emissive material.
  • the porous body can be made of tungsten and the emissive material of barium, calcium and strontium aluminates. She begins to emit electrons around 900 ° to 1100 ° C.
  • the control grid is very close to the cathode.
  • the interval between the grid and the cathode is of the order of a few tenths of millimeters.
  • Emissive material tends to evaporate and migrate especially on the control grid and on the anode.
  • the grid heats up, partly because of the proximity of the cathode, and partly because of the electrons hitting it.
  • the emissive material which migrated on the grid causes a parasitic emission of electrons which disturbs the functioning of the tube.
  • the anode being relatively far from the cathode, it remains relatively cold and the emissive material covering it is not too embarrassing.
  • Another way to avoid this emission of electrons parasite consists in reducing the temperature of the grid as much as possible during the operation of the tube.
  • a known solution is to use a cathode working at lower temperatures than cathodes conventional to thereby lower the temperature of the control grid. This solution also does not give good results. The phenomenon spurious emission is only delayed but not eliminated.
  • the present invention aims to remedy these drawbacks by offering an electron gun whose cathode contributes to better grid cooling and effectively prevents emission parasite.
  • This cathode has an emissive part which delimits a substantially central recess which crosses it right through.
  • the cathode is advantageously heated by a device heater which has a heating element opposite its part emissive, this heating element delimiting a recess facing the recess of the cathode.
  • the grid has a solid part radiating thermally, intended to be placed facing the recess of the cathode. Dissipation thermal radiation grid is improved by this part full, radiating thermally, because it can radiate towards the recess of the cathode and towards the anode zone which is a cold zone. The grid being better cooled the stray electron emission is eliminated.
  • the present invention also relates to an electronic tube comprising such a cannon.
  • FIG. 1a shows in longitudinal section an electron gun known.
  • the cathode has the reference 1. It is full and in the shape of portion of a sphere, its active face is concave.
  • a heater 2 is in contact with the cathode 1 opposite its active face.
  • Electrons emitted by the active face of cathode 1 pass through a control grid 3 and are attracted by an anode 4. They form a longitudinal axis beam XX '.
  • Anode 4 has a central opening 5 to leave the beam of electrons entering a resonant cavity (not shown).
  • Anode 4 is brought to a more positive potential than cathode 1.
  • Grid 3 is generally brought to a potential intermediate between that of cathode 1 and that of anode 4.
  • the grid 3 is mounted on a peripheral support 6 produced in a good thermal conductive material such as copper. She is also in shape of a portion of a sphere with first bars 7 arranged on parallels of the sphere and of the second bars 8 arranged on meridians of the sphere. The two portions of sphere i.e. that of the cathode 1 and that of grid 3 have their center on the axis XX '.
  • Figure 1b shows the front view of the grid.
  • cathode 1 heats emissive material evaporates and it will notably cover the grid 3. By heating the grid starts to emit parasitic electrons.
  • the grid 3 is cooled in one leaves by conduction to the peripheral support 6 via the first and second bars 7, 8, and on the other hand by radiation towards the anode 4 essentially.
  • the hottest part of the grid 3 is its central part. Any increasing the size of cathode 1 leads to increasing the size of the grid 3 and therefore the temperature of its central part. To avoid increasing the parasitic emission from the grid 3, we are forced to limit the size of the cathode 1 and therefore the electronic current which it supplies.
  • FIGS 2a and 2b show from the front and in longitudinal section an example of a cathode 10 of a cannon according to the invention.
  • the cathode is a portion of a sphere. It has a part emissive 12 which defines a substantially central recess 11.
  • the emissive part 12 is concave and substantially shaped like a segment of a sphere and the recess 11 is substantially circular.
  • the emissive surface of a cathode such as that of Figure 1a varies at first order as the square of its diameter.
  • the diameter of the recess 11 represents approximately 30 to 40% of the diameter of the cathode 10
  • the surface of the recess 11 is relatively small and has no practically no influence on the electronic emission.
  • the low loss of emissive surface can be offset by a small increase in cathode diameter 10.
  • a conventional solid cathode in 38 mm diameter spherical cap shape has the same surface that a cathode according to the invention whose emissive part is in segment spherical 40 millimeters in diameter and whose recess has a diameter 15 millimeters.
  • FIG. 3 represents the drawing of a grid of a cannon according to the invention.
  • This grid is intended to be associated with a cathode of the type from that shown in Figures 2a and 2b.
  • the grid has a part 24 full, thermally radiating, intended to be placed facing the cathode recess.
  • the grid When the grid is mounted in a barrel electrons with such an electron-emitting cathode, it can radiate on the one hand towards the anode and on the other hand towards the recess of the cathode.
  • This grid is effectively cooled and stray electron emission is eliminated.
  • the diameter of the cathode is dissociated from the grid temperature and we can consider design more powerful electronic tubes with this type of gun.
  • the part 24 full of the grid 23 is made of a material having a capacity of thermal radiation close to that of the black body.
  • Graphite and more particularly pyrolitic graphite is a particularly good material suitable for making this solid part 24 radiating thermally.
  • the grid shown in Figure 3 has around the part 24 full an openwork part 26 which is intended to be crossed by the electrons emitted from the cathode.
  • the openwork part 26 may also be made of pyrolitic graphite because of its thermal properties, advantageous electrical and mechanical.
  • the grid 23 is intended to be used with a cathode substantially in the shape of a portion of a sphere, it is preferable that it be also substantially in the form of a portion of a sphere.
  • the full part 24 can be in the form of a spherical cap and the perforated part 26 may include first bars 28 arranged along meridians of the sphere and second bars 29 along parallels of the sphere.
  • the grid 23 can be produced from a graphite blank pyrolitic, for example in the form of a portion of a sphere, in which sizes the bars 28, 29 and the solid part 24. This size can be achieved conventionally, for example by laser machining or by sandblasting.
  • the openwork part 26 of the grid has substantially rectangular or hexagonal openings.
  • FIG. 4 shows in longitudinal section, an example of a cannon with electrons according to the invention mounted in an electronic tube also according to the invention.
  • the barrel comprises a cathode 21 according to the invention and a control grid 23 both substantially in the form of portion of sphere.
  • the cathode 21 has an emissive part 27 in the form of a segment of a sphere which delimits a recess 22 substantially central.
  • An anode 25 and a heater 40 of the cathode have also been shown in this figure.
  • the electronic tube is partially shown. It features the electron gun and the electrons emitted are finally recovered from the race in a collector 43.
  • the grid 23 associated with the cathode according to the invention comprises a solid part 24. It is comparable to that of the figure 3. Its heat dissipation is better than in the barrel of the Figure 1a.
  • the bars 28, 29 of the grid are cooled by conduction, both to the support peripheral 30 and towards the solid part 24 radiating thermally.
  • the solid part 24 is cooled by radiation towards the anode 25 and towards the recess 22 of the cathode 21.
  • the length of the first bars 28 is considerably reduced compared to that of the bars of Figure 1b. For example, their length can go from around 41 millimeters to around 14.5 millimeters in the example cited above.
  • the solid part 24 of the grid 23 will have substantially the same size as the recess 22 of the cathode 21.
  • the cathode according to the invention is associated with a grid without a solid part, i.e. a traditional grid like the one in Figure 1b, for example. If this grid is carried out in a material having a radiation capacity close to that of the black body, the part of the grid facing the cathode recess can radiate towards this obviously.
  • the cooling of the central part of the grid is improved compared to that of a grid as shown in Figure 1a and associated with a full cathode but it is not as good as in the case of the figure 4. However in some cases, this cooling is completely sufficient.
  • a device 40 for indirect heating of the cathode has been shown in the figure 4. It is seen from the front in figure 5. It is intended to heat the part emissive 27 of the cathode 21. It is disposed near the convex face of cathode 21. It includes a heating element 42 defining a recess 41 facing the recess 22 of the cathode 21. It may be shaped of perforated plate defining a network of conductors 45 in which can circulate an electric current. This tray will be produced, preferably in an electrically conductive material, having a radiation capacity thermal close to that of the black body. Pyrolitic graphite is particularly suitable for producing the heating element 42. In the example in Figure 5, the plate has a series of slots 44 in an arc concentric, the slots 44 placed on two successive circles being offset from each other. The space between the slots 44 forms the network of electrical conductors 42.
  • the barrel according to the invention is not limited to a cathode in portion of sphere, nor to a grid in portion of sphere.

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  • Microwave Tubes (AREA)
  • Electron Sources, Ion Sources (AREA)

Description

Le domaine de l'invention est celui des tubes électroniques et notamment ceux à faisceaux d'électrons longitudinaux à grille tels que les IOT (abréviation des termes anglais Inductive Output Tube).The field of the invention is that of electronic tubes and especially those with longitudinal electron beams with a grid such as IOT (abbreviation of the English terms Inductive Output Tube).

Un IOT comporte un canon à électrons qui émet un faisceau d'électrons, une cavité résonante qui est traversée par le faisceau et un collecteur qui recueille les électrons du faisceau à leur sortie de la cavité.An IOT has an electron gun that emits a beam of electrons, a resonant cavity which is crossed by the beam and a collector which collects the beam electrons as they exit the cavity.

Le canon à électrons comporte une cathode généralement concave et en forme de portion de sphère, une grille de commande et une anode. La face concave de la cathode émet des électrons lorsqu'elle est portée à haute température. Les électrons traversent la grille de commande et sont attirés par l'anode puis pénètrent dans la cavité résonante en formant un faisceau longitudinal, voir EP-A-0 578 525.The electron gun has a cathode generally concave and shaped like a portion of a sphere, a control grid and a anode. The concave side of the cathode emits electrons when it is brought to high temperature. Electrons pass through the control grid and are attracted to the anode and then enter the resonant cavity in forming a longitudinal beam, see EP-A-0 578 525.

La grille de commande sert à moduler l'émission d'électrons de manière à les regrouper en paquets avant leur entrée dans la cavité résonante.The control grid is used to modulate the emission of electrons from so as to group them into packages before entering the cavity resonant.

La cathode est généralement réalisée par un corps poreux imprégné d'un matériau émissif. Le corps poreux peut être en tungstène et le matériau émissif des aluminates de baryum, de calcium et de strontium. Elle commence à émettre des électrons aux alentours de 900° à 1100° C.The cathode is generally made by a porous body impregnated with an emissive material. The porous body can be made of tungsten and the emissive material of barium, calcium and strontium aluminates. She begins to emit electrons around 900 ° to 1100 ° C.

La grille de commande est très proche de la cathode. L'intervalle entre la grille et la cathode est de l'ordre de quelques dixièmes de millimètres. Le matériau émissif à tendance à s'évaporer et à migrer notamment sur la grille de commande et sur l'anode. La grille chauffe, d'une part à cause de la proximité de la cathode, et d'autre part à cause des électrons qui la percutent. Le matériau émissif qui a migré sur la grille provoque une émission d'électrons parasite qui perturbe le fonctionnement du tube. L'anode étant relativement éloignée de la cathode, elle reste relativement froide et le matériau émissif qui la recouvre n'est pas trop gênant.The control grid is very close to the cathode. The interval between the grid and the cathode is of the order of a few tenths of millimeters. Emissive material tends to evaporate and migrate especially on the control grid and on the anode. The grid heats up, partly because of the proximity of the cathode, and partly because of the electrons hitting it. The emissive material which migrated on the grid causes a parasitic emission of electrons which disturbs the functioning of the tube. The anode being relatively far from the cathode, it remains relatively cold and the emissive material covering it is not too embarrassing.

Des solutions ont été proposées pour éliminer cette émission d'électrons parasite. L'une d'elle préconise de bombarder la grille avec des électrons pour la chauffer et pour faire évaporer le matériau émissif qui la recouvre. La fréquence de ce chauffage peut être journalière, avant chaque mise en route par exemple. Le nettoyage de la grille par chauffage est une contrainte sévère sur un émetteur de télévision qui peut fonctionner sur un site isolé avec un pilotage à distance. Ce chauffage peut aussi provoquer à la longue une dégradation du fonctionnement du canon à électrons.Solutions have been proposed to eliminate this emission of parasitic electrons. One of them recommends bombing the grid with electrons to heat it and to evaporate the emissive material which covers. The frequency of this heating can be daily, before each getting started for example. Cleaning the grid by heating is a severe constraint on a television transmitter which can operate on a isolated site with remote control. This heating can also cause the long-term degradation of the operation of the electron gun.

Une autre voie suivie pour éviter cette émission d'électrons parasite consiste à diminuer autant que possible la température de la grille pendant le fonctionnement du tube. Une solution connue est d'utiliser une cathode travaillant à des températures plus basses que celles des cathodes classiques pour abaisser de ce fait la température de la grille de commande. Cette solution ne donne pas non plus de bons résultats. Le phénomène d'émission parasite est seulement retardé mais pas éliminé.Another way to avoid this emission of electrons parasite consists in reducing the temperature of the grid as much as possible during the operation of the tube. A known solution is to use a cathode working at lower temperatures than cathodes conventional to thereby lower the temperature of the control grid. This solution also does not give good results. The phenomenon spurious emission is only delayed but not eliminated.

Un autre inconvénient rencontré est que l'émission parasite de la grille de commande limite la taille de la cathode et par conséquent le courant électronique produit.Another drawback encountered is that the parasitic emission of the control grid limits the size of the cathode and therefore the electronic current produced.

La présente invention vise à remédier à ces inconvénients en proposant un canon à électrons dont la cathode contribue à un meilleur refroidissement de la grille et permet d'éviter efficacement l'émission parasite.The present invention aims to remedy these drawbacks by offering an electron gun whose cathode contributes to better grid cooling and effectively prevents emission parasite.

Cette cathode comporte une partie émissive qui délimite un évidement sensiblement central qui la traverse de part en part.This cathode has an emissive part which delimits a substantially central recess which crosses it right through.

La cathode est de manière avantageuse chauffée par un dispositif de chauffage qui comporte un élément chauffant à l'opposé de sa partie émissive, cet élément chauffant délimitant un évidement face à l'évidement de la cathode.The cathode is advantageously heated by a device heater which has a heating element opposite its part emissive, this heating element delimiting a recess facing the recess of the cathode.

La grille comporte une partie pleine rayonnant thermiquement, destinée à être disposée face à l'évidement de la cathode. La dissipation thermique de la grille par rayonnement est améliorée grâce à cette partie pleine, rayonnant thermiquement, car elle peut rayonner vers l'évidement de la cathode et vers la zone anodique qui est une zone froide. La grille étant mieux refroidie l'émission d'électrons parasite est éliminée.The grid has a solid part radiating thermally, intended to be placed facing the recess of the cathode. Dissipation thermal radiation grid is improved by this part full, radiating thermally, because it can radiate towards the recess of the cathode and towards the anode zone which is a cold zone. The grid being better cooled the stray electron emission is eliminated.

Il est préférable de réaliser la partie pleine dans un matériau ayant une capacité de rayonnement thermique proche de celle du corps noir. Le graphite pyrolitique est particulièrement avantageux.It is better to make the solid part in a material having a thermal radiation capacity close to that of the black body. Pyrolitic graphite is particularly advantageous.

La présente invention concerne aussi un tube électronique comportant un tel canon. The present invention also relates to an electronic tube comprising such a cannon.

D'autres caractéristiques et avantages de l'invention apparaítront à la lecture de la description ci-dessous illustrée par les figures annexées qui représentent:

  • les figures 1a,1b respectivement une coupe longitudinale d'un canon à électrons de l'art antérieur et une vue de face de sa grille;
  • les figures 2a, 2b respectivement une vue de face et une coupe transversale d'un exemple d'une cathode d'un canon conforme à l'invention;
  • la figure 3 une vue de face d'un exemple d'une grille d'un canon conforme à l'invention;
  • la figure 4 une coupe schématique longitudinale d'un exemple d'un canon à électrons conforme à l'invention monté dans un tube électronique également conforme à l'invention;
  • la figure 5 une vue de face d'un dispositif pour chauffer la cathode du canon selon l'invention.
Other characteristics and advantages of the invention will appear on reading the description below illustrated by the appended figures which represent:
  • Figures 1a, 1b respectively a longitudinal section of an electron gun of the prior art and a front view of its grid;
  • Figures 2a, 2b respectively a front view and a cross section of an example of a cathode of a gun according to the invention;
  • Figure 3 a front view of an example of a grid of a cannon according to the invention;
  • Figure 4 a schematic longitudinal section of an example of an electron gun according to the invention mounted in an electronic tube also according to the invention;
  • Figure 5 a front view of a device for heating the cathode of the barrel according to the invention.

Sur ces figures, les mêmes références désignent les mêmes éléments. Pour des raisons de clarté les côtes des différents éléments ne sont pas respectées.In these figures, the same references designate the same elements. For reasons of clarity, the dimensions of the various elements do not are not respected.

La figure 1a montre en coupe longitudinale un canon à électrons connu. La cathode porte la référence 1. Elle est pleine et en forme de portion de sphère, sa face active est concave. Un dispositif de chauffage 2 est en contact avec la cathode 1 à l'opposé de sa face active. Les électrons émis par la face active de la cathode 1 traversent une grille 3 de commande et sont attirés par une anode 4. Ils forment un faisceau longitudinal d'axe XX'. L'anode 4 comporte une ouverture centrale 5 pour laisser le faisceau d'électrons pénétrer dans une cavité résonante (non représentée). L'anode 4 est portée à un potentiel plus positif que la cathode 1. La grille 3 est généralement portée à un potentiel intermédiaire entre celui de la cathode 1 et celui de l'anode 4.Figure 1a shows in longitudinal section an electron gun known. The cathode has the reference 1. It is full and in the shape of portion of a sphere, its active face is concave. A heater 2 is in contact with the cathode 1 opposite its active face. Electrons emitted by the active face of cathode 1 pass through a control grid 3 and are attracted by an anode 4. They form a longitudinal axis beam XX '. Anode 4 has a central opening 5 to leave the beam of electrons entering a resonant cavity (not shown). Anode 4 is brought to a more positive potential than cathode 1. Grid 3 is generally brought to a potential intermediate between that of cathode 1 and that of anode 4.

La grille 3 est montée sur un support périphérique 6 réalisé dans un matériau bon conducteur thermique tel que le cuivre. Elle est aussi en forme de portion de sphère avec des premiers barreaux 7 disposés sur des parallèles de la sphère et des seconds barreaux 8 disposés sur des méridiens de la sphère. Les deux portions de sphère c'est à dire celle de la cathode 1 et celle de la grille 3 ont leur centre sur l'axe XX'. La figure 1b montre de face le dessin de la grille. The grid 3 is mounted on a peripheral support 6 produced in a good thermal conductive material such as copper. She is also in shape of a portion of a sphere with first bars 7 arranged on parallels of the sphere and of the second bars 8 arranged on meridians of the sphere. The two portions of sphere i.e. that of the cathode 1 and that of grid 3 have their center on the axis XX '. Figure 1b shows the front view of the grid.

Lorsque la cathode 1 chauffe du matériau émissif s'évapore et il va recouvrir notamment la grille 3. En chauffant la grille se met à émettre des électrons parasites. Le refroidissement de la grille 3 s'effectue d'une part par conduction vers le support périphérique 6 par l'intermédiaire des premiers et des seconds barreaux 7, 8, et d'autre part par rayonnement vers l'anode 4 essentiellement.When cathode 1 heats emissive material evaporates and it will notably cover the grid 3. By heating the grid starts to emit parasitic electrons. The grid 3 is cooled in one leaves by conduction to the peripheral support 6 via the first and second bars 7, 8, and on the other hand by radiation towards the anode 4 essentially.

La partie la plus chaude de la grille 3 est sa partie centrale. Toute augmentation de la taille de la cathode 1 conduit à augmenter la taille de la grille 3 et donc la température de sa partie centrale. Pour éviter d'augmenter l'émission parasite de la grille 3, on est contraint de limiter la taille de la cathode 1 et par conséquent le courant électronique qu'elle fournit.The hottest part of the grid 3 is its central part. Any increasing the size of cathode 1 leads to increasing the size of the grid 3 and therefore the temperature of its central part. To avoid increasing the parasitic emission from the grid 3, we are forced to limit the size of the cathode 1 and therefore the electronic current which it supplies.

Les figures 2a et 2b montrent de face et en coupe longitudinale un exemple d'une cathode 10 d'un canon conforme à l'invention. Sur cette figure, la cathode est une portion de sphère. Elle comporte une partie émissive 12 qui délimite un évidement 11 sensiblement central.Figures 2a and 2b show from the front and in longitudinal section an example of a cathode 10 of a cannon according to the invention. On this figure, the cathode is a portion of a sphere. It has a part emissive 12 which defines a substantially central recess 11.

De préférence, dans un but de simplification la partie émissive 12 est concave et sensiblement en forme de segment de sphère et l'évidement 11 est sensiblement circulaire. La surface émissive d'une cathode telle que celle de la figure 1a varie au premier ordre comme le carré de son diamètre. Dans le cas d'une cathode selon l'invention avec un évidement, si le diamètre de l'évidement 11 représente environ 30 à 40 % du diamètre de la cathode 10, la surface de l'évidement 11 est relativement petite et n'a pratiquement pas d'influence sur l'émission électronique. La faible perte de surface émissive peut être compensée par une faible augmentation du diamètre de la cathode 10. Par exemple, une cathode classique pleine en forme de calotte sphérique de 38 millimètres de diamètre a la même surface qu'une cathode selon l'invention dont la partie émissive est en segment sphérique de 40 millimètres de diamètre et dont l'évidement a un diamètre de 15 millimètres .Preferably, in order to simplify the emissive part 12 is concave and substantially shaped like a segment of a sphere and the recess 11 is substantially circular. The emissive surface of a cathode such as that of Figure 1a varies at first order as the square of its diameter. In the case of a cathode according to the invention with a recess, if the diameter of the recess 11 represents approximately 30 to 40% of the diameter of the cathode 10, the surface of the recess 11 is relatively small and has no practically no influence on the electronic emission. The low loss of emissive surface can be offset by a small increase in cathode diameter 10. For example, a conventional solid cathode in 38 mm diameter spherical cap shape has the same surface that a cathode according to the invention whose emissive part is in segment spherical 40 millimeters in diameter and whose recess has a diameter 15 millimeters.

La figure 3 représente le dessin d'une grille d'un canon selon l'invention. Cette grille est destinée à être associée à une cathode de type de celle représentée sur les figures 2a et 2b. La grille comporte une partie 24 pleine, rayonnant thermiquement, destinée à être disposée face à l'évidement de la cathode. Lorsque la grille est montée dans un canon à électrons avec une telle cathode émettant des électrons, elle peut rayonner d'une part vers l'anode et d'autre part vers l'évidement de la cathode. Cette grille est refroidie efficacement et l'émission d'électrons parasite est éliminée. Avec un meilleur refroidissement de la grille, le diamètre de la cathode est dissocié de la température de la grille et on peut envisager de concevoir des tubes électroniques plus puissants avec ce type de canon.FIG. 3 represents the drawing of a grid of a cannon according to the invention. This grid is intended to be associated with a cathode of the type from that shown in Figures 2a and 2b. The grid has a part 24 full, thermally radiating, intended to be placed facing the cathode recess. When the grid is mounted in a barrel electrons with such an electron-emitting cathode, it can radiate on the one hand towards the anode and on the other hand towards the recess of the cathode. This grid is effectively cooled and stray electron emission is eliminated. With better cooling of the grid, the diameter of the cathode is dissociated from the grid temperature and we can consider design more powerful electronic tubes with this type of gun.

Dans un mode de réalisation préféré de la grille, la partie 24 pleine de la grille 23 est réalisée dans un matériau ayant une capacité de rayonnement thermique proche de celle du corps noir. Le graphite et plus particulièrement le graphite pyrolitique est un matériau particulièrement bien adapté pour réaliser cette partie pleine 24 rayonnant thermiquement.In a preferred embodiment of the grid, the part 24 full of the grid 23 is made of a material having a capacity of thermal radiation close to that of the black body. Graphite and more particularly pyrolitic graphite is a particularly good material suitable for making this solid part 24 radiating thermally.

La grille représentée sur la figure 3 comporte autour de la partie 24 pleine une partie ajourée 26 qui est destinée à être traversée par les électrons émis par la cathode. La partie ajourée 26 pourra aussi être réalisée en graphite pyrolitique à cause de ses propriétés thermiques, électriques et mécaniques avantageuses.The grid shown in Figure 3 has around the part 24 full an openwork part 26 which is intended to be crossed by the electrons emitted from the cathode. The openwork part 26 may also be made of pyrolitic graphite because of its thermal properties, advantageous electrical and mechanical.

Si la grille 23 est destinée à être utilisée avec une cathode sensiblement en forme de portion de sphère, il est préférable qu'elle soit aussi sensiblement en forme de portion de sphère. La partie 24 pleine peut être en forme de calotte sphérique et la partie ajourée 26 peut comporter des premiers barreaux 28 disposés selon des méridiens de la sphère et des seconds barreaux 29 selon des parallèles de la sphère.If the grid 23 is intended to be used with a cathode substantially in the shape of a portion of a sphere, it is preferable that it be also substantially in the form of a portion of a sphere. The full part 24 can be in the form of a spherical cap and the perforated part 26 may include first bars 28 arranged along meridians of the sphere and second bars 29 along parallels of the sphere.

La grille 23 peut être réalisée à partir d'une ébauche en graphite pyrolitique, par exemple en forme de portion de sphère, dans laquelle on taille les barreaux 28, 29 et la partie pleine 24. Cette taille peut être réalisée de manière classique, par exemple par usinage laser ou par sablage au jet.The grid 23 can be produced from a graphite blank pyrolitic, for example in the form of a portion of a sphere, in which sizes the bars 28, 29 and the solid part 24. This size can be achieved conventionally, for example by laser machining or by sandblasting.

On pourrait aussi envisager que la partie ajourée 26 de la grille comporte des ouvertures sensiblement rectangulaires ou hexagonales.We could also consider that the openwork part 26 of the grid has substantially rectangular or hexagonal openings.

La figure 4 montre en coupe longitudinale, un exemple d'un canon à électrons selon l'invention monté dans un tube électronique également conforme à l'invention. Le canon comporte une cathode 21 selon l'invention et une grille de commande 23 toutes les deux sensiblement en forme de portion de sphère. Sur la figure, la cathode 21 comporte une partie émissive 27 en forme de segment de sphère qui délimite un évidement 22 sensiblement central. Une anode 25 et un dispositif de chauffage 40 de la cathode ont aussi été représentés sur cette figure. Le tube électronique est représenté partiellement. Il comporte le canon à électrons et les électrons émis sont récupérés enfin de course dans un collecteur 43.Figure 4 shows in longitudinal section, an example of a cannon with electrons according to the invention mounted in an electronic tube also according to the invention. The barrel comprises a cathode 21 according to the invention and a control grid 23 both substantially in the form of portion of sphere. In the figure, the cathode 21 has an emissive part 27 in the form of a segment of a sphere which delimits a recess 22 substantially central. An anode 25 and a heater 40 of the cathode have also been shown in this figure. The electronic tube is partially shown. It features the electron gun and the electrons emitted are finally recovered from the race in a collector 43.

Sur cette figure, la grille 23 associée à la cathode selon l'invention comporte une partie pleine 24. Elle est comparable à celle de la figure 3. Sa dissipation thermique est meilleure que dans le canon de la figure 1a.In this figure, the grid 23 associated with the cathode according to the invention comprises a solid part 24. It is comparable to that of the figure 3. Its heat dissipation is better than in the barrel of the Figure 1a.

Si on entoure la grille 23 d'un support périphérique 30 réalisé dans un matériau bon conducteur thermique, tel que du cuivre, la dissipation thermique est encore meilleure. Dans cette configuration, les barreaux 28, 29 de la grille sont refroidis par conduction, à la fois vers le support périphérique 30 et vers la partie pleine 24 rayonnant thermiquement. La partie pleine 24 est refroidie par rayonnement vers l'anode 25 et vers l'évidement 22 de la cathode 21. La longueur des premiers barreaux 28 est considérablement réduite par rapport à celle des barreaux de la figure 1b. Par exemple, leur longueur peut passer d'environ 41 millimètres à environ 14, 5 millimètres dans l'exemple cité précédemment .If the grid 23 is surrounded by a peripheral support 30 produced in a good thermal conductive material, such as copper, dissipation thermal is even better. In this configuration, the bars 28, 29 of the grid are cooled by conduction, both to the support peripheral 30 and towards the solid part 24 radiating thermally. The solid part 24 is cooled by radiation towards the anode 25 and towards the recess 22 of the cathode 21. The length of the first bars 28 is considerably reduced compared to that of the bars of Figure 1b. For example, their length can go from around 41 millimeters to around 14.5 millimeters in the example cited above.

De préférence, pour une meilleure efficacité du refroidissement et une perturbation minimale du faisceau d'électrons émis, la partie pleine 24 de la grille 23 aura sensiblement la même taille que l'évidement 22 de la cathode 21.Preferably, for better cooling efficiency and minimal disturbance of the electron beam emitted, the solid part 24 of the grid 23 will have substantially the same size as the recess 22 of the cathode 21.

On aurait pu envisager que la cathode selon l'invention soit associée à une grille sans partie pleine, c'est à dire une grille traditionnelle comme celle de la figure 1b, par exemple. Si cette grille est réalisée dans un matériau ayant une capacité de rayonnement proche de celle du corps noir, la partie de la grille face à l'évidement de la cathode peut rayonner vers cet évidement. Le refroidissement de la partie centrale de la grille est amélioré par rapport à celui d'une grille telle que représentée sur la figure 1a et associée à une cathode pleine mais il est moins bon que dans le cas de la figure 4. Toutefois dans certains cas, ce refroidissement est tout à fait suffisant.One could have envisaged that the cathode according to the invention is associated with a grid without a solid part, i.e. a traditional grid like the one in Figure 1b, for example. If this grid is carried out in a material having a radiation capacity close to that of the black body, the part of the grid facing the cathode recess can radiate towards this obviously. The cooling of the central part of the grid is improved compared to that of a grid as shown in Figure 1a and associated with a full cathode but it is not as good as in the case of the figure 4. However in some cases, this cooling is completely sufficient.

La cathode doit être chauffée pour pouvoir émettre des électrons. Un dispositif de chauffage 40 indirect de la cathode a été représenté sur la figure 4. Il est vu de face sur la figure 5. Il est prévu pour chauffer la partie émissive 27 de la cathode 21. Il est disposé à proximité de la face convexe de la cathode 21. Il comporte un élément chauffant 42 délimitant un évidement 41 face à l'évidement 22 de la cathode 21. Il peut être en forme de plateau ajouré définissant un réseau de conducteurs 45 dans lequel peut circuler un courant électrique. Ce plateau sera réalisé, de préférence dans un matériau conducteur électrique, ayant une capacité de rayonnement thermique proche de celle du corps noir. Le graphite pyrolitique est particulièrement adapté pour réaliser l'élément chauffant 42. Sur l'exemple de la figure 5, le plateau comporte une série de fentes 44 en arc de cercle concentriques, les fentes 44 placées sur deux cercles successifs étant décalées les unes par rapport aux autres. L'espace entre les fentes 44 forme le réseau de conducteurs 42 électriques.The cathode must be heated to be able to emit electrons. A device 40 for indirect heating of the cathode has been shown in the figure 4. It is seen from the front in figure 5. It is intended to heat the part emissive 27 of the cathode 21. It is disposed near the convex face of cathode 21. It includes a heating element 42 defining a recess 41 facing the recess 22 of the cathode 21. It may be shaped of perforated plate defining a network of conductors 45 in which can circulate an electric current. This tray will be produced, preferably in an electrically conductive material, having a radiation capacity thermal close to that of the black body. Pyrolitic graphite is particularly suitable for producing the heating element 42. In the example in Figure 5, the plate has a series of slots 44 in an arc concentric, the slots 44 placed on two successive circles being offset from each other. The space between the slots 44 forms the network of electrical conductors 42.

Le canon selon l'invention n'est pas limité à une cathode en portion de sphère, ni à une grille en portion de sphère.The barrel according to the invention is not limited to a cathode in portion of sphere, nor to a grid in portion of sphere.

Claims (16)

  1. Electron gun with grid, incorporating a cathode with an emissive portion (27), characterised in that the emissive portion (27) delimits an aperture (22) which passes right through it and which is more or less centrally positioned in a manner that assists the cooling of the grid.
  2. Electron gun according to claim 1, characterised in that the emissive portion (27) of the cathode is more or less a segment of a sphere.
  3. Electron gun according to either of claims 1 and 2, characterised in that the hole (22) in the cathode is more or less circular.
  4. Electron gun according to either of claims 2 and 3, characterised in that the diameter of the hole (22) in the cathode represents approximately 30 to 40 % of the diameter of the emissive portion (27).
  5. Electron gun according to any of claims 1 to 4, characterised in that it incorporates a heater (40) for heating the cathode with a heating element (42) which delimits a hole (41) situated opposite the hole (22) in the cathode.
  6. Electron gun according to claim 5, characterised in that the heating element (42) is a perforated plate which defines an array of electrical conductors (45).
  7. Electron gun according to either of claims 5 and 6, characterised in that the heating element (42) is made of pyrolytic graphite.
  8. Electron gun according to any of claims 1 to 7, characterised in that the grid possesses a thermally radiative solid portion (24) intended to lie opposite the hole (22) in the cathode (21).
  9. Electron gun according to claim 8, characterised in that the thermally radiative solid portion (24) of the grid has more or less the same dimensions as the hole (22) in the cathode (21).
  10. Electron gun according to either of claims 8 and 9, characterised in that the thermally radiative solid portion (24) of the grid is made from a material having a thermal radiation capacity close to that of a black body.
  11. Electron gun according to claim 10, characterised in that the thermally radiative solid portion (24) of the grid is made of pyrolytic graphite.
  12. Electron gun according to any of claims 8 to 11, characterised in that the grid has a perforated part (26) around the solid portion (24), said perforated part (26) being intended to be penetrated by the electrons emitted by the cathode (21).
  13. Electron gun according to claim 12, characterised in that the grid more or less in the form of a portion of a sphere has a perforated part with first bars (28) lying along meridians of the sphere and second bars (29) lying along lines of latitude of the sphere.
  14. Electron gun according to any of claims 8 to 13, characterised in that the thermally radiative solid part (24) of the grid is more or less in the form of a spherical cap.
  15. Electron gun according to any of claims 1 to 14, characterised in that the grid is surrounded by a peripheral support (30) made from a material that is a good thermal conductor.
  16. Electron tube characterised in that it incorporates a grid electron gun according to any one of claims 1 to 15.
EP96914252A 1995-05-05 1996-04-26 Grid electron gun Expired - Lifetime EP0824758B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9505408 1995-05-05
FR9505408A FR2733856B1 (en) 1995-05-05 1995-05-05 CATHODE FOR GRID ELECTRON CANON, GRID TO BE ASSOCIATED WITH SUCH A CATHODE AND ELECTRON CANON INCLUDING SUCH CATHODE
PCT/FR1996/000644 WO1996035219A1 (en) 1995-05-05 1996-04-26 Grid electron gun

Publications (2)

Publication Number Publication Date
EP0824758A1 EP0824758A1 (en) 1998-02-25
EP0824758B1 true EP0824758B1 (en) 2001-08-16

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EP96914252A Expired - Lifetime EP0824758B1 (en) 1995-05-05 1996-04-26 Grid electron gun

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US (1) US5936335A (en)
EP (1) EP0824758B1 (en)
JP (1) JP4019431B2 (en)
CN (1) CN1099689C (en)
DE (1) DE69614520T2 (en)
FR (1) FR2733856B1 (en)
WO (1) WO1996035219A1 (en)

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GB9915925D0 (en) * 1999-07-08 1999-09-08 Univ Loughborough Flow field plates
US7345290B2 (en) * 1999-10-07 2008-03-18 Agere Systems Inc Lens array for electron beam lithography tool
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FR2853450B1 (en) * 2003-04-04 2006-09-08 Thales Sa CONTROL GRID OF AN ELECTRONIC TUBE
JP4113032B2 (en) * 2003-04-21 2008-07-02 キヤノン株式会社 Electron gun and electron beam exposure apparatus
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Also Published As

Publication number Publication date
FR2733856B1 (en) 1997-08-29
FR2733856A1 (en) 1996-11-08
CN1183852A (en) 1998-06-03
JP4019431B2 (en) 2007-12-12
CN1099689C (en) 2003-01-22
EP0824758A1 (en) 1998-02-25
US5936335A (en) 1999-08-10
DE69614520D1 (en) 2001-09-20
JPH11505059A (en) 1999-05-11
WO1996035219A1 (en) 1996-11-07
DE69614520T2 (en) 2002-05-08

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