EP0379403A1 - Electron gun comprising a device producing a magnetic field in the proximity of the cathode - Google Patents

Electron gun comprising a device producing a magnetic field in the proximity of the cathode Download PDF

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Publication number
EP0379403A1
EP0379403A1 EP90400089A EP90400089A EP0379403A1 EP 0379403 A1 EP0379403 A1 EP 0379403A1 EP 90400089 A EP90400089 A EP 90400089A EP 90400089 A EP90400089 A EP 90400089A EP 0379403 A1 EP0379403 A1 EP 0379403A1
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EP
European Patent Office
Prior art keywords
cathode
electron gun
solenoid
magnetic field
gun according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP90400089A
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German (de)
French (fr)
Inventor
Georges Faillon
Christophe Bastien
Christine Farvet
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales Electron Devices SA
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Thomson Tubes Electroniques
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Publication date
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Publication of EP0379403A1 publication Critical patent/EP0379403A1/en
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    • 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
    • H01J23/08—Focusing arrangements, e.g. for concentrating stream of electrons, for preventing spreading of stream
    • H01J23/087—Magnetic focusing arrangements
    • 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
    • H01J23/065—Electron or ion guns producing a solid cylindrical beam

Definitions

  • the present invention relates to electron guns producing a cylindrical electron beam. It relates more particularly to cannons operating at high voltage. These guns are used, in particular in electron tubes with longitudinal interaction, these tubes are called "O" type. In this type of tube, the electron beam is focused by a magnetic field collinear with the trajectory of the electrons. The klystrons, the traveling wave tubes are type "O" tubes. These guns can also be used in other vacuum devices, such as particle accelerators.
  • An electron gun producing a long and fine electron beam is generally built around an axis of revolution. It comprises a cathode, generally made of thermoemissive material, heated, brought to a generally negative potential. It is surrounded by a focusing electrode known as the wehnelt, brought to the same potential as the cathode.
  • the cathode emits a beam of electrons to an anode.
  • the wehnelt converges the electron beam from the cathode.
  • These two electrodes are surrounded by the anode.
  • the anode and the wehnelt are open in their center to let pass the electron beam coming from the cathode. Grids can be inserted between the cathode and the wehnelt.
  • Ceramic elements serve to support the electrodes and electrically insulate them from each other.
  • the electron beam emitted by the cathode and focused by the wehnelt and the anode, then enters a room, in the form of a tunnel which is the body of the electron tube.
  • This body is generally grounded.
  • the anode can either be brought to a potential intermediate between that of the cathode and that of the body of the tube, or be brought to the same potential as the body of the tube.
  • the beam is focused using a solenoid, a permanent magnet or a series of alternating contiguous magnets.
  • the body of the tube ends in an electron collector.
  • the induction must be low so as not to disturb the emission of electrons. It is increased as one moves away from the cathode, in order to make the electron beam converge in the barrel; Finally, the induction is given a constant value outside the barrel, that is to say in the body of the tube.
  • a pole piece is generally placed between the barrel and the body of the tube; this piece shields from the large field present in the body of the tube.
  • pole piece can give a particular geometry to the pole piece. It is generally made of mild steel. It can be more or less open, more or less thick, more or less conical. But the pole piece acts mainly on the electron beam only at the exit of the barrel. It has little action at the cathode level.
  • the electrodes are brought to very high voltages, and a large space separates them, in order to avoid breakdowns. Consequently, the barrel has a large diameter and the armor will therefore also have a large diameter. It will be relatively far from the cathode and its influence on the magnetic field at the cathode will therefore be weak, even if a small complementary solenoid has been added.
  • the present invention aims to remedy these drawbacks and proposes an electron gun fitted with a device producing a magnetic field in the vicinity of the cathode.
  • An electron gun comprising several electrodes including a cathode, and a device for producing a magnetic field, this device cooperating with an electrode other than the cathode and close to the cathode to establish a controlled magnetic field. in the immediate vicinity of the cathode.
  • an electrode will serve as a support for a solenoid; the power supply of the solenoid will be made from a generator whose potential is referenced with respect to the potential of this electrode or to a neighboring potential.
  • the electrode is the wehnelt or the anode; as these electrodes surround the front face of the cathode, they make it possible to create a well-controlled magnetic field in the immediate vicinity of the front face of the cathode.
  • an electrode other than the cathode may serve as a support for permanent magnets distributed in a ring around the cathode.
  • the electrode other than the cathode, which cooperates with the device for producing a magnetic field, can be made of magnetic material; the electrode itself then makes it possible to guide a magnetic flux (generated by magnets or a solenoid) around the front face of the cathode; as the electrode is close to the cathode, it is thus possible to control very effectively, and possibly adjust the magnetic field in the immediate vicinity of the cathode.
  • a magnetic flux generated by magnets or a solenoid
  • the magnets or the solenoid can then be carried by the electrode or simply be in contact with one end of this electrode, even if this end is far from the cathode: for example, the electrode, wehnelt or anode, is made of magnetic material and a solenoid is placed in magnetic contact with the electrode outside the barrel, where the electrode is supported by the outer wall of the barrel.
  • the barrel shown in Figure 1 is built around an axis YY ′ of revolution.
  • the barrel is integrated in a tube of type "O" of which only the body 5 has been shown.
  • the barrel comprises a cathode 1, made of thermoemissive material. It has the shape of a cup and is heated to around 1100 ° C by a filament not shown. This cathode is brought to a high potential - V0 of the order of 100 kV. It gives rise to an electron beam 4 converging thanks to the action of a focusing electrode or wehnelt 2 which surrounds the cathode 1.
  • the electron beam 4 has substantially the shape of a cylinder and is accelerated towards the body 5 of the tube.
  • the wehnelt is generally made of molybdenum, stainless steel or copper. It is brought to the same potential - V0 as the cathode 1.
  • An anode 3 surrounds the wehnelt 2. This anode 3 is brought to a potential -V A. It is generally made in whole or in part in molybdenum or copper. Grids can be inserted between the cathode 1 and the wehnelt 2. In FIG. 1, a grid has not been shown.
  • the barrel essentially comprises all the electrodes located between the cathode 1 and the anode 3.
  • the body of the tube generally made of copper, is brought to ground.
  • This focusing device is generally magnetic. Around the body of the tube, it can consist of permanent magnets, a solenoid or alternating adjoining magnets. A focusing device has not been shown.
  • the anode 3 is secured by one of its ends 11 to a first spacer 7 and a second insulating spacer 13, of cylindrical shape, which surround the barrel.
  • the spacer 7 holds the anode 3 in place and electrically isolates it from the body 5 of the tube.
  • Cathode 1 and wehnelt 2 are fixed on a circular insulating wall 8 which closes the bottom of the barrel.
  • the second insulating spacer 13 bears on one side at the periphery of the insulating wall 8 and on the other at the end 11 of the anode 3. It contributes to isolating the cathode 1 and the wehnelt 2 from the anode 3.
  • the other end 12 of the anode 3, placed near the cathode 1 converges the electron beam.
  • This end 12 of the anode 3 may be made of a material different from the rest of the anode.
  • the spacers 7 and 13 and the wall 8 are generally made of ceramic. They contribute with the body of the tube to define a sealed enclosure 14 surrounding the electrodes of the barrel. This enclosure 14 is subjected to vacuum.
  • the barrel is partially immersed in a magnetic field.
  • the induction on cathode 1 must be low and then it must increase in the interval between cathode 1 and body 5 of the tube.
  • the diameter of the spacers is large so as to leave a suitable isolation space between the different electrodes. This avoids the risks of breakdown by electric arcs between the electrodes and the body of the tube, or between electrodes brought to different potentials.
  • the geometry of this pole piece 6 makes it possible to vary the focus of the electron beam 4. It can be more or less open, more or less thick, more or less conical.
  • the pole piece 6 focuses the electron beam especially between the anode 3 and the inlet of the body of the tube. This part does not allow to adjust as it should be the magnetic field inside the barrel; it mainly serves as a screen against the fairly intense magnetic field which reigns in the body of the tube, so that this field remains sufficiently weak in the immediate vicinity of the cathode.
  • Another known structure has a magnetic shield 9, of cylindrical shape, made of mild steel for example, around the barrel, outside the spacers 7, 13.
  • This shield 9 is placed between the output of the cathode 1 and the pole piece 6.
  • the shield 9 can be fixed to the pole piece 6. It is even possible to add a solenoid 10 in this shielding 9, in order to be able to fine-tune the magnetic field settings during the tests.
  • the cylindrical shield 9 In barrels operating at high voltage, the cylindrical shield 9 has a large diameter because of the isolation spaces between electrodes. Its action on the focusing of the electron beam 4 is very weak even if the solenoid 10 has been added.
  • FIG. 2 represents, in section an electron gun, of axis YY ′, comparable to that of FIG. 1. But it is provided with a device producing a magnetic field in the vicinity of the cathode.
  • the magnetic field is adjustable since it is produced by a solenoid and we can act on the current passing through this solenoid.
  • the barrel is integrated in a tube of type "O" of which only part of the body 25 has been shown.
  • the barrel has an anode 23 brought to the same potential as the body 25. It is integral, by one of its ends 28 of the body 25 of the tube. Its other end 29 is integral with a spacer 15 comparable to the spacer 13 in Figure 1. This spacer 15 is supported on an insulating wall 16 which closes the barrel.
  • the body of the tube 25, the anode 23 as well as the spacer 15 and the wall 16 contribute to defining a sealed enclosure 17 subjected to vacuum.
  • Cathode 1 is cup-shaped. It is provided with a heating filament 20.
  • the cathode 1, heated to a high temperature of the order of 1100 ° C. produces an electron beam 4.
  • a thermal screen 21 is placed near the filament 20 in order to thermally stabilize the interior of the enclosure 17.
  • the cathode 1 is surrounded by a wehnelt 22.
  • the device producing the adjustable magnetic field is integrated into the wehnelt 22.
  • the wehnelt 22 comprises a cavity 24, at the interior of which a solenoid 27 has been placed. This solenoid 27 is located near the cathode 1 and its action is effective on the electron beam 4.
  • the solenoid 27 has the shape of a ring or a neighboring shape. It is mounted coaxially with the cathode 1.
  • the wehnelt has been thickened so as to be able to accommodate the solenoid 27.
  • the parts of the gun being generally thick, nothing prevents the introduction of the solenoid 27.
  • the cavity 24 does not communicate with the interior of the enclosure 17.
  • the cavity 24 opens to the exterior of the enclosure 17 by crossing the wall 16.
  • the cavity 24 can be closed by a tight plug 26 placed on the wall 16 so that the interior of the cavity 24 is not in contact with the atmosphere outside the enclosure 17.
  • the outside atmosphere is either air or oil, or sulfur fluoride SF6. These materials have an insulating role.
  • the wire used to make the solenoid 27 can be made of pure tungsten or of tungsten alloyed with rhenium for example.
  • the wire used to make this solenoid is insulated by ceramic pieces of suitable shape.
  • the solenoid 27 is brought overall to the potential of the wehnelt, therefore to the potential -V0 of the cathode 1.
  • the solenoid can be mounted in series with the heating filament 20 as shown in FIG. 2.
  • At least one sealed passage 18 placed in the wall 16 seals between the interior and the exterior of the enclosure 17 at the level of the wire connecting the solenoid to the heating filament.
  • the wehnelt will be made of a magnetic metallic material such as mild steel or mild iron. But it can also be made of non-magnetic material, the field then being directly that of the solenoid.
  • Figure 3 shows in section an electron gun comparable to that of Figure 1. It is provided with another variant of the device producing the adjustable magnetic field near the cathode 1.
  • This device is integrated into the anode 30 and not into the wehnelt.
  • the anode 30 which surrounds the wehnelt 2 comprises a cavity 32 inside which a solenoid 31 has been placed.
  • the anode 30 is in this case isolated from the body 5 of the tube as in FIG. 1. It is made partially or completely in a magnetic metallic material, such as soft iron or mild steel.
  • a first end 19 of the anode 30 is integral with the spacers 7 and 13.
  • the other end 33 of the anode 30, close to the cathode 1, is made of a material different from the rest of the anode.
  • This material can be molybdenum for example.
  • the part made of magnetic metallic material will be more or less long, more or less thick. It is also advisable that this part does not heat too much and does not lose permeability.
  • the material used will be manufactured under vacuum, so as to avoid any untimely degassing.
  • the solenoid 31 can be placed more or less close to the electron beam 4 according to the desired effect on the magnetic flux lines existing in the gun.
  • This solenoid 32 will be supplied by a supply 36 referenced with respect to the potential of the anode 30.
  • the current may be controlled during the tests by means of optical fibers, for example.
  • Reference 34 represents the supply of cathode 1 supplying the potential - V0.
  • the reference 35 represents the supply of the anode 30 supplying the potential -V A.
  • the supply 35 of the anode and the supply 36 of the solenoid will each be provided with an isolation transformer 37.
  • the solenoid 31 is connected to its supply 36 by means of a conductor 38 inserted in a conduit 39 which passes to the inside the anode 30 and which opens at its end 19 outside the enclosure 14 delimited by the spacers 7, 13.
  • Figure 4 shows in section a cannon comparable to that of Figure 1. It is provided with another variant of the device producing the adjustable magnetic field in the vicinity of the cathode.
  • the device producing the adjustable magnetic field consists of a solenoid 40 placed in contact with the anode 41.
  • a first end 42 of the anode 41 is integral with the spacers 7, 13. It is at this first end 42 that there is contact between the anode 41 and the solenoid 40.
  • the solenoid is placed outside the enclosure 14.
  • This device producing the adjustable magnetic field can be used in guns operating at lower voltage.
  • the diameter of the barrel is less important and it becomes more difficult to integrate a solenoid inside the anode or the whenelt.
  • the anode 41 will be made of a magnetic metallic material, either partially or completely, to guide the magnetic flux from the solenoid to a region in the immediate vicinity of the cathode. In the figure it is partially in a magnetic metallic material.
  • the second end 43, close to the cathode 1 and surrounding the electron beam, is made of another material, molybdenum for example.
  • the solenoid is supplied by a supply, not shown. This supply is referenced with respect to the potential of the anode 41 as in the previous case.
  • FIG. 5 represents in section, an electron gun comparable to that of FIG. 4. It is provided with a new variant of the device producing the magnetic field in the vicinity of the cathode.
  • the device producing the magnetic field consists of one or more magnets 50, magnetized beforehand.
  • magnets are placed in a ring outside the enclosure 14 and are in contact with the anode 51.
  • a first end 52 of the anode 51 is secured to the spacers 7, 13. It is at this first end 52 which makes contact between the anode 51 and the magnets 50.
  • the magnets 50 are arranged so that their induction lines are directed towards the inside of the anode 51.
  • the anode 51 is made wholly or partially in a magnetic metallic material.
  • Figure 5 there is shown the second end 53 of the anode 51, close to the cathode 1, in another material, molybdenum for example.
  • the magnets 50 are brought to the same potential as the anode 51.
  • the number of magnets 50 is arbitrary. It is possible to adjust the magnetic field relatively finely in the vicinity of the cathode 1 by modifying the number of magnets 50 placed in a ring around the anode 51 and their position.
  • the invention is not limited to the examples described. Many variants can occur in terms of the shape or position of the device producing a magnetic field near the cathode without departing from the scope of the invention. It suffices that one of the electrodes other than the cathode is provided with the device producing a magnetic field in the vicinity of the cathode.

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Abstract

The present invention relates to electron guns comprising several electrodes (1, 2, 30), among them a cathode (1). The gun comprises a device (31) producing a, possibly adjustable, magnetic field in the proximity of the cathode (1). <??>This device interacts with one of the electrodes (30) other than the cathode (1); it interacts in particular with the anode or the Wehnelt. This device is either a solenoid (31) or one or more permanent magnets. <??>This device is placed either inside or outside the gun. <??>Application to high-power "O" type electron tubes. <IMAGE>

Description

La présente invention se rapporte aux canons à électrons produisant un faisceau d'électrons cylindrique. Elle se rapporte plus particulièrement aux canons fonctionnant à haute tension. Ces canons sont utilisés, notamment dans des tubes électroniques à interaction longitudinale, ces tubes sont dits de type "O". Dans ce genre de tube, le faisceau d'électrons est focalisé par un champ magnétique colinéaire à la trajectoire des électrons. Les klystrons, les tubes à ondes progressives sont des tubes de type "O". On peut également utiliser ces canons dans d'autres dispositifs sous vide, tels que les accélérateurs de particules.The present invention relates to electron guns producing a cylindrical electron beam. It relates more particularly to cannons operating at high voltage. These guns are used, in particular in electron tubes with longitudinal interaction, these tubes are called "O" type. In this type of tube, the electron beam is focused by a magnetic field collinear with the trajectory of the electrons. The klystrons, the traveling wave tubes are type "O" tubes. These guns can also be used in other vacuum devices, such as particle accelerators.

Un canon à électrons produisant un faisceau d'électrons long et fin, est généralement construit autour d'un axe de révolution. Il comporte une cathode, généralement en matériau thermoémissif, chauffée, portée à un potentiel généralement négatif. Elle est entourée d'une électrode de focalisation connue sous le nom de wehnelt, portée au même potentiel que la cathode. La cathode émet un faisceau d'électrons vers une anode. Le wehnelt fait converger le faisceau d'électrons issu de la cathode. Ces deux électrodes sont entourées par l'anode. L'anode et le wehnelt sont ouverts en leur centre pour laisser passer le faisceau d'électrons issu de la cathode. Des grilles peuvent être insérées entre la cathode et le wehnelt. Des éléments en céramique, par exemple de forme cylindrique, servent de support aux électrodes et les isolent électriquement les unes des autres. Le faisceau d'électrons, émis par la cathode et focalisé par le wehnelt et l'anode, pénètre ensuite dans une pièce, en forme de tunnel qui est le corps du tube électronique. Ce corps est généralement porté à la masse. L'anode peut être soit portée à un potentiel intermédiaire entre celui de la cathode et celui du corps du tube, soit portée au même potentiel que le corps du tube. A l'intérieur du corps du tube, le faisceau est focalisé grâce à un solénoïde, un aimant permanent ou une suite d'aimants jointifs alternés. Le corps du tube se termine par un collecteur d'électrons.An electron gun producing a long and fine electron beam, is generally built around an axis of revolution. It comprises a cathode, generally made of thermoemissive material, heated, brought to a generally negative potential. It is surrounded by a focusing electrode known as the wehnelt, brought to the same potential as the cathode. The cathode emits a beam of electrons to an anode. The wehnelt converges the electron beam from the cathode. These two electrodes are surrounded by the anode. The anode and the wehnelt are open in their center to let pass the electron beam coming from the cathode. Grids can be inserted between the cathode and the wehnelt. Ceramic elements, for example of cylindrical shape, serve to support the electrodes and electrically insulate them from each other. The electron beam, emitted by the cathode and focused by the wehnelt and the anode, then enters a room, in the form of a tunnel which is the body of the electron tube. This body is generally grounded. The anode can either be brought to a potential intermediate between that of the cathode and that of the body of the tube, or be brought to the same potential as the body of the tube. Inside the tube body, the beam is focused using a solenoid, a permanent magnet or a series of alternating contiguous magnets. The body of the tube ends in an electron collector.

Afin d'obtenir un faisceau d'électrons homogène, ayant un diamètre voulu et ondulant peu, il faut régler le flux du champ magnétique s'appliquant tout le long du faisceau d'électrons, dans le canon et dans le corps du tube. L'ondulation du faisceau d'électrons est due aux effets de répulsion mutuelle des électrons. Au niveau de la cathode, l'induction doit être faible pour ne pas perturber l'émission d'électrons. On l'augmente à mesure qu'on s'éloigne de la cathode, afin de faire converger le faisceau d'électrons dans le canon; on donne enfin à l'induction une valeur constante hors du canon, c'est-à-dire dans le corps du tube.In order to obtain a homogeneous electron beam, having a desired diameter and undulating little, it is necessary to regulate the flux of the magnetic field applying all along the electron beam, in the barrel and in the body of the tube. The ripple of the electron beam is due to the mutual repulsion effects of the electrons. At the cathode, the induction must be low so as not to disturb the emission of electrons. It is increased as one moves away from the cathode, in order to make the electron beam converge in the barrel; Finally, the induction is given a constant value outside the barrel, that is to say in the body of the tube.

Pour éviter qu'un champ magnétique trop intense ne règne à proximité immédiate de la cathode, on place en général une pièce polaire entre le canon et le corps du tube; cette pièce fait écran par rapport au champ important présent dans le corps du tube. Pour obtenir un faisceau ayant un diamètre voulu et ondulant peu à la sortie du canon, il faut établir un bon compromis entre l'induction sur la cathode, l'induction dans le corps du tube, le rayon du faisceau et son ondulation. Ces configurations du champ magnétique sont critiques et certaines solutions ont été apportées :To prevent an excessively strong magnetic field from prevailing in the immediate vicinity of the cathode, a pole piece is generally placed between the barrel and the body of the tube; this piece shields from the large field present in the body of the tube. To obtain a beam having a desired diameter and undulating little at the exit of the barrel, it is necessary to establish a good compromise between the induction on the cathode, the induction in the body of the tube, the radius of the beam and its undulation. These magnetic field configurations are critical and certain solutions have been provided:

On peut donner une géométrie particulière à la pièce polaire. Elle est généralement en acier doux. Elle peut être plus ou moins ouverte, plus ou moins épaisse, plus ou moins conique. Mais la pièce polaire n'agit principalement sur le faisceau d'électrons qu'à la sortie du canon. Elle a peu d'action au niveau de la cathode.We can give a particular geometry to the pole piece. It is generally made of mild steel. It can be more or less open, more or less thick, more or less conical. But the pole piece acts mainly on the electron beam only at the exit of the barrel. It has little action at the cathode level.

On peut aussi blinder le canon, en plaçant un blindage cylindrique en acier doux, à l'extérieur du canon. Ce blindage est placé autour des éléments en céramique, au niveau de la cathode mais à l'extérieur du canon. Il est également possible d'ajouter un petit solénoïde à l'intérieur du blindage ; cela permet d'affiner les réglages au cours des essais. Dans le cas d'un canon utilisé dans des tubes à forte puissance et/ou fréquence basse, les électrodes sont portées à de très fortes tensions, et un grand espace les sépare, afin d'éviter des claquages. En conséquence, le canon a un diamètre important et le blindage aura donc aussi un diamètre important. Il sera relativement éloigné de la cathode et son influence sur le champ magnétique au niveau de la cathode sera donc faible, même si l'on a rajouté un petit solénoïde complémentaire.One can also shield the barrel, by placing a cylindrical shielding out of mild steel, outside the barrel. This shielding is placed around the ceramic elements, at the cathode but outside the barrel. It is also possible to add a small solenoid inside the shield; this makes it possible to refine the settings during the tests. In the case of a gun used in high power and / or low frequency tubes, the electrodes are brought to very high voltages, and a large space separates them, in order to avoid breakdowns. Consequently, the barrel has a large diameter and the armor will therefore also have a large diameter. It will be relatively far from the cathode and its influence on the magnetic field at the cathode will therefore be weak, even if a small complementary solenoid has been added.

La présente invention vise à remédier à ces inconvénients et propose un canon à électrons muni d'un dispositif produisant un champ magnétique au voisinage de la cathode.The present invention aims to remedy these drawbacks and proposes an electron gun fitted with a device producing a magnetic field in the vicinity of the cathode.

On propose selon l'invention un canon à électrons comportant plusieurs électrodes parmi lesquelles une cathode, et un dispositif de production d'un champ magnétique, ce dispositif coopérant avec une électrode autre que la cathode et proche de la cathode pour établir un champ magnétique contrôlé au voisinage immédiat de la cathode.An electron gun is proposed according to the invention comprising several electrodes including a cathode, and a device for producing a magnetic field, this device cooperating with an electrode other than the cathode and close to the cathode to establish a controlled magnetic field. in the immediate vicinity of the cathode.

Dans certaines réalisations, une électrode servira de support à un solénoïde; l'alimentation électrique du solénoïde se fera à partir d'un générateur dont le potentiel est référencé par rapport au potentiel de cette électrode ou à un potentiel voisin. Par exemple, l'électrode est le wehnelt ou l'anode; comme ces électrodes entourent la face avant de la cathode, ils permettent de créer un champ magnétique bien contrôlé à proximité immédiate de la face avant de la cathode.In certain embodiments, an electrode will serve as a support for a solenoid; the power supply of the solenoid will be made from a generator whose potential is referenced with respect to the potential of this electrode or to a neighboring potential. For example, the electrode is the wehnelt or the anode; as these electrodes surround the front face of the cathode, they make it possible to create a well-controlled magnetic field in the immediate vicinity of the front face of the cathode.

Dans d'autres réalisations, une électrode autre que la cathode pourra servir de support à des aimants permanents répartis en couronne autour de la cathode.In other embodiments, an electrode other than the cathode may serve as a support for permanent magnets distributed in a ring around the cathode.

On prévoit selon une autre caractéristique de l'invention que l' électrode, autre que la cathode, qui coopère avec le dispositif de production d'un champ magnétique, peut être réalisée en matériau magnétique; l'électrode elle-même permet alors de guider un flux magnétique (engendré par des aimants ou un solénoïde) autour de la face avant de la cathode; comme l'électrode est proche de la cathode, on peut ainsi contrôler très efficacement, et éventuellement règler le champ magnétique au voisinage immédiat de la cathode. Les aimants ou le solénoïde peuvent alors être portés par l'électrode ou simplement être en contact avec une extrémité de cette électrode, même si cette extrémité est éloignée de la cathode: par exemple, l'électrode, wehnelt ou anode, est en matériau magnétique et un solénoïde est placé en contact magnétique avec l'électrode à l'extérieur du canon, à l'endroit où l'électrode est supportée par la paroi extérieure du canon.It is provided according to another characteristic of the invention that the electrode, other than the cathode, which cooperates with the device for producing a magnetic field, can be made of magnetic material; the electrode itself then makes it possible to guide a magnetic flux (generated by magnets or a solenoid) around the front face of the cathode; as the electrode is close to the cathode, it is thus possible to control very effectively, and possibly adjust the magnetic field in the immediate vicinity of the cathode. The magnets or the solenoid can then be carried by the electrode or simply be in contact with one end of this electrode, even if this end is far from the cathode: for example, the electrode, wehnelt or anode, is made of magnetic material and a solenoid is placed in magnetic contact with the electrode outside the barrel, where the electrode is supported by the outer wall of the barrel.

D'autres caractéristiques et avantages de l'invention apparaîtront à la lecture de la description suivante, illustrée par les figures annexées qui représentent :

  • - la figure 1 : une coupe d'un canon à électrons de type "O", produisant un faisceau d'électrons cylindrique intégré dans un tube selon l'art antérieur;
  • - la figure 2 : une coupe d'un canon à électrons avec une anode non isolée et un solénoïde produisant un champ magnétique réglable intégré au wehnelt;
  • - la figure 3 : une coupe d'un canon à électrons comportant une anode équipée d'un solénoïde destiné à régler le champ magnétique à proximité de la cathode ;
  • - la figure 4 : une coupe d'un canon à électrons comportant une anode équipée d'un solénoïde externe destiné à régler le champ magnétique à proximité de la cathode;
  • - la figure 5 : une coupe d'un canon à électrons comportant une anode équipée d'une pluralité d'aimants externes destinés à régler le champ magnétique à proximité de la cathode.
Other characteristics and advantages of the invention will appear on reading the following description, illustrated by the appended figures which represent:
  • - Figure 1: a section of an electron gun type "O", producing a cylindrical electron beam integrated in a tube according to the prior art;
  • - Figure 2: a section of an electron gun with a non-isolated anode and a solenoid producing an adjustable magnetic field integrated in the wehnelt;
  • - Figure 3: a section of an electron gun having an anode equipped with a solenoid for adjusting the magnetic field near the cathode;
  • - Figure 4: a section of an electron gun having an anode equipped with an external solenoid for adjusting the magnetic field near the cathode;
  • - Figure 5: a section of an electron gun comprising an anode equipped with a plurality of external magnets intended to adjust the magnetic field near the cathode.

Sur ces figures les mêmes repères représentent les mêmes éléments.In these figures the same references represent the same elements.

Le canon représenté sur la figure 1 est construit autour d'un axe YY′ de révolution. Le canon est intégré dans un tube de type "O" dont on n'a représenté que le corps 5. Le canon comprend une cathode 1, en matériau thermoémissif. Elle a la forme d'une coupelle et est chauffée à environ 1100°C par un filament non représenté. Cette cathode est portée à un potentiel élevé - V₀ de l'ordre de 100 kV. Elle donne naissance à un faisceau d'électrons 4 convergeant grâce à l'action d'une électrode de focalisation ou wehnelt 2 qui entoure la cathode 1. Le faisceau d'électrons 4 a sensiblement la forme d'un cylindre et est accéléré vers le corps 5 du tube. Le wehnelt est généralement réalisé en molybdène en acier inoxydable ou en cuivre. Il est porté au même potentiel - V₀ que la cathode 1. Une anode 3 entoure le wehnelt 2. Cette anode 3 est portée à un potentiel -VA. Elle est généralement réalisée en totalité ou en partie en molybdène ou en cuivre. Des grilles peuvent être intercalées entre la cathode 1 et le wehnelt 2. Sur la figure 1 on n'a pas représenté de grille. Le canon comprend essentiellement toutes les électrodes situées entre la cathode 1 et l'anode 3. Le corps du tube, généralement en cuivre est porté à une masse.The barrel shown in Figure 1 is built around an axis YY ′ of revolution. The barrel is integrated in a tube of type "O" of which only the body 5 has been shown. The barrel comprises a cathode 1, made of thermoemissive material. It has the shape of a cup and is heated to around 1100 ° C by a filament not shown. This cathode is brought to a high potential - V₀ of the order of 100 kV. It gives rise to an electron beam 4 converging thanks to the action of a focusing electrode or wehnelt 2 which surrounds the cathode 1. The electron beam 4 has substantially the shape of a cylinder and is accelerated towards the body 5 of the tube. The wehnelt is generally made of molybdenum, stainless steel or copper. It is brought to the same potential - V₀ as the cathode 1. An anode 3 surrounds the wehnelt 2. This anode 3 is brought to a potential -V A. It is generally made in whole or in part in molybdenum or copper. Grids can be inserted between the cathode 1 and the wehnelt 2. In FIG. 1, a grid has not been shown. The barrel essentially comprises all the electrodes located between the cathode 1 and the anode 3. The body of the tube, generally made of copper, is brought to ground.

Les effets de répulsion mutuelle des électrons s'opposent au maintien d'un faisceau d'électrons long et fin et un dispositif de focalisation est nécessaire tout au long du canon et surtout au niveau du corps du tube. Ce dispositif de focalisation est généralement magnétique. Autour du corps du tube, il peut être constitué d'aimants permanents, d'un solénoïde ou d'aimants jointifs alternés. On n'a pas représenté de dispositif de focalisation.The effects of mutual repulsion of the electrons oppose the maintenance of a long and fine electron beam and a focusing device is necessary throughout the barrel and especially at the level of the body of the tube. This focusing device is generally magnetic. Around the body of the tube, it can consist of permanent magnets, a solenoid or alternating adjoining magnets. A focusing device has not been shown.

L'anode 3 est solidaire par une de ses extrémités 11 d'une première entretoise 7 et d'une seconde entretoise 13 isolantes, de forme cylindrique, qui entourent le canon. L'entretoise 7 maintient en place l'anode 3 et l'isole électriquement du corps 5 du tube. La cathode 1 et le wehnelt 2 sont fixés sur une paroi isolante 8 circulaire qui ferme le fond du canon. La deuxième entretoise 13 isolante prend appui d'un côté à la périphérie de la paroi 8 isolante et de l'autre à l'extrémité 11 de l'anode 3. Elle contribue à isoler la cathode 1 et le wehnelt 2 de l'anode 3. L'autre extrémité 12 de l'anode 3, placée à proximité de la cathode 1 fait converger le faisceau d'électrons. Cette extrémité 12 de l'anode 3 peut être dans un matériau différent du reste de l'anode. Les entretoises 7 et 13 et la paroi 8 sont généralement réalisées en céramique. Elles contribuent avec le corps du tube à définir une enceinte étanche 14 entourant les électrodes du canon. Cette enceinte 14 est soumise au vide.The anode 3 is secured by one of its ends 11 to a first spacer 7 and a second insulating spacer 13, of cylindrical shape, which surround the barrel. The spacer 7 holds the anode 3 in place and electrically isolates it from the body 5 of the tube. Cathode 1 and wehnelt 2 are fixed on a circular insulating wall 8 which closes the bottom of the barrel. The second insulating spacer 13 bears on one side at the periphery of the insulating wall 8 and on the other at the end 11 of the anode 3. It contributes to isolating the cathode 1 and the wehnelt 2 from the anode 3. The other end 12 of the anode 3, placed near the cathode 1 converges the electron beam. This end 12 of the anode 3 may be made of a material different from the rest of the anode. The spacers 7 and 13 and the wall 8 are generally made of ceramic. They contribute with the body of the tube to define a sealed enclosure 14 surrounding the electrodes of the barrel. This enclosure 14 is subjected to vacuum.

Le canon est partiellement immergé dans un champ magnétique. L'induction sur la cathode 1 doit être faible puis elle doit augmenter dans l'intervalle situé entre la cathode 1 et le corps 5 du tube.The barrel is partially immersed in a magnetic field. The induction on cathode 1 must be low and then it must increase in the interval between cathode 1 and body 5 of the tube.

Dans le cas d'un canon fonctionnant à tension élevée, le diamètre des entretoises est important de manière à laisser un espace d'isolement convenable entre les différentes électrodes. Cela évite les risques de claquage par arcs électriques entre les électrodes et le corps du tube, ou entre électrodes portées à des potentiels différents.In the case of a gun operating at high voltage, the diameter of the spacers is large so as to leave a suitable isolation space between the different electrodes. This avoids the risks of breakdown by electric arcs between the electrodes and the body of the tube, or between electrodes brought to different potentials.

Une pièce polaire 6, généralement en acier doux, sépare le canon, du corps 5 du tube. La géométrie de cette pièce polaire 6 permet de faire varier la focalisation du faisceau d'électrons 4. Elle peut être plus ou moins ouverte, plus ou moins épaisse, plus ou moins conique. La pièce polaire 6 focalise le faisceau d'électrons surtout entre l'anode 3 et l'entrée du corps du tube. Cette pièce ne permet pas de régler comme il le faudrait le champ magnétique à l'intérieur du canon; elle sert surtout d'écran contre le champ magnétique assez intense qui règne dans le corps du tube, pour que ce champ reste suffisamment faible à proximité immédiate de la cathode.A pole piece 6, generally made of mild steel, separates the barrel from the body 5 of the tube. The geometry of this pole piece 6 makes it possible to vary the focus of the electron beam 4. It can be more or less open, more or less thick, more or less conical. The pole piece 6 focuses the electron beam especially between the anode 3 and the inlet of the body of the tube. This part does not allow to adjust as it should be the magnetic field inside the barrel; it mainly serves as a screen against the fairly intense magnetic field which reigns in the body of the tube, so that this field remains sufficiently weak in the immediate vicinity of the cathode.

Une autre structure connue possède un blindage 9 magnétique, de forme cylindrique, en acier doux par exemple, autour du canon, à l'extérieur des entretoises 7, 13. Ce blindage 9 se place entre la sortie de la cathode 1 et la pièce polaire 6. Le blindage 9 peut être fixé à la pièce polaire 6. Il est même possible d'ajouter un solénoïde 10 dans ce blindage 9, afin de pouvoir affiner les réglages du champ magnétique au cours des essais.Another known structure has a magnetic shield 9, of cylindrical shape, made of mild steel for example, around the barrel, outside the spacers 7, 13. This shield 9 is placed between the output of the cathode 1 and the pole piece 6. The shield 9 can be fixed to the pole piece 6. It is even possible to add a solenoid 10 in this shielding 9, in order to be able to fine-tune the magnetic field settings during the tests.

Dans les canons fonctionnant à tension élevée, le blindage 9 cylindrique a un diamètre important à cause des espaces d'isolement entre électrodes. Son action sur la focalisation du faisceau 4 d'électrons est très faible même si l'on a ajouté le solénoïde 10.In barrels operating at high voltage, the cylindrical shield 9 has a large diameter because of the isolation spaces between electrodes. Its action on the focusing of the electron beam 4 is very weak even if the solenoid 10 has been added.

La figure 2 représente, en coupe un canon à électrons, d'axe YY′, comparable à celui de la figure 1. Mais il est muni d'un dispositif produisant un champ magnétique au voisinage de la cathode. Dans cet exemple, le champ magnétique est réglable puisqu'il est produit par un solénoïde et que l'on peut agir sur le courant traversant ce solénoïde.FIG. 2 represents, in section an electron gun, of axis YY ′, comparable to that of FIG. 1. But it is provided with a device producing a magnetic field in the vicinity of the cathode. In this example, the magnetic field is adjustable since it is produced by a solenoid and we can act on the current passing through this solenoid.

Le canon est intégré dans un tube de type "O" dont on n'a représenté qu une partie du corps 25. De plus le canon comporte une anode 23 portée au même potentiel que le corps 25. Elle est solidaire, par l'une de ses extrémités 28 du corps 25 du tube. Son autre extrémité 29 est solidaire d'une entretoise 15 comparable à l'entretoise 13 de la figure 1. Cette entretoise 15 s'appuie sur une paroi 16 isolante qui ferme le canon. Le corps du tube 25, l'anode 23 ainsi que l'entretoise 15 et la paroi 16 contribuent à définir une enceinte 17 étanche soumise au vide.The barrel is integrated in a tube of type "O" of which only part of the body 25 has been shown. In addition, the barrel has an anode 23 brought to the same potential as the body 25. It is integral, by one of its ends 28 of the body 25 of the tube. Its other end 29 is integral with a spacer 15 comparable to the spacer 13 in Figure 1. This spacer 15 is supported on an insulating wall 16 which closes the barrel. The body of the tube 25, the anode 23 as well as the spacer 15 and the wall 16 contribute to defining a sealed enclosure 17 subjected to vacuum.

La cathode 1 est en forme de coupelle. Elle est munie d'un filament 20 de chauffage. La cathode 1, chauffée à une température élevée de l'ordre de 1100°C produit un faisceau d'électrons 4. Un écran thermique 21 est placé à proximité du filament 20 afin de stabiliser thermiquement l'intérieur de l'enceinte 17. La cathode 1 est entourée d'un wehnelt 22. Le dispositif produisant le champ magnétique réglable est intégré au wehnelt 22. Le wehnelt 22 comprend une cavité 24, à l'intérieur de laquelle on a disposé un solénoïde 27. Ce solénoïde 27 est situé à proximité de la cathode 1 et son action est efficace sur le faisceau 4 d'électrons. Le solénoïde 27 a la forme d'un anneau ou une forme voisine. Il est monté coaxialement avec la cathode 1. On remarque que le wehnelt a été épaissi de manière à pouvoir loger le solénoïde 27. Dans les canons à tension élevée, les pièces du canon étant généralement épaisses, rien ne s'oppose à l'introduction du solénoïde 27. La cavité 24 ne communique pas avec l'intérieur de l'enceinte 17. La cavité 24 débouche à l'extérieur de l'enceinte 17 en traversant la paroi 16. La cavité 24 peut être obturée par un bouchon 26 étanche placé sur la paroi 16 de manière à ce que l'intérieur de la cavité 24 ne soit pas en contact avec l'ambiance extérieure à l'enceinte 17. L'ambiance extérieure est soit de l'air, soit de l'huile, soit du fluorure de soufre SF₆. Ces matériaux ont un rôle d'isolant.Cathode 1 is cup-shaped. It is provided with a heating filament 20. The cathode 1, heated to a high temperature of the order of 1100 ° C. produces an electron beam 4. A thermal screen 21 is placed near the filament 20 in order to thermally stabilize the interior of the enclosure 17. The cathode 1 is surrounded by a wehnelt 22. The device producing the adjustable magnetic field is integrated into the wehnelt 22. The wehnelt 22 comprises a cavity 24, at the interior of which a solenoid 27 has been placed. This solenoid 27 is located near the cathode 1 and its action is effective on the electron beam 4. The solenoid 27 has the shape of a ring or a neighboring shape. It is mounted coaxially with the cathode 1. It is noted that the wehnelt has been thickened so as to be able to accommodate the solenoid 27. In the high voltage guns, the parts of the gun being generally thick, nothing prevents the introduction of the solenoid 27. The cavity 24 does not communicate with the interior of the enclosure 17. The cavity 24 opens to the exterior of the enclosure 17 by crossing the wall 16. The cavity 24 can be closed by a tight plug 26 placed on the wall 16 so that the interior of the cavity 24 is not in contact with the atmosphere outside the enclosure 17. The outside atmosphere is either air or oil, or sulfur fluoride SF₆. These materials have an insulating role.

Il est également possible que le solénoïde 27 soit en contact avec l'ambiance extérieure à l'enceinte 17. Dans ce cas, le bouchon 26 obturant la cavité 24 n'est plus utile.It is also possible that the solenoid 27 is in contact with the atmosphere outside the enclosure 17. In this case, the plug 26 closing the cavity 24 is no longer useful.

Le fil utilisé pour la réalisation du solénoïde 27 peut être en tungstène pur ou en tungstène allié avec du rhénium par exemple. Le fil qui sert à réaliser ce solénoïde est isolé par des pièces en céramique de forme adéquate. Le solénoïde 27 est porté globalement au potentiel du wehnelt donc au potentiel -V₀ de la cathode 1. Le solénoïde peut être monté en série avec le filament 20 de chauffage comme représenté sur la figure 2. Au moins un passage étanche 18 placé dans la paroi 16 assure l'étanchéité entre l'intérieur et l'extérieur de l'enceinte 17 au niveau du fil reliant le solénoïde au filament de chauffage. Le wehnelt sera réalisé dans un matériau métallique magnétique tel que de l'acier doux ou du fer doux. Mais il peut être aussi en matériau amagnétique, le champ étant alors directement celui du solénoïde.The wire used to make the solenoid 27 can be made of pure tungsten or of tungsten alloyed with rhenium for example. The wire used to make this solenoid is insulated by ceramic pieces of suitable shape. The solenoid 27 is brought overall to the potential of the wehnelt, therefore to the potential -V₀ of the cathode 1. The solenoid can be mounted in series with the heating filament 20 as shown in FIG. 2. At least one sealed passage 18 placed in the wall 16 seals between the interior and the exterior of the enclosure 17 at the level of the wire connecting the solenoid to the heating filament. The wehnelt will be made of a magnetic metallic material such as mild steel or mild iron. But it can also be made of non-magnetic material, the field then being directly that of the solenoid.

La figure 3 représente en coupe un canon à électrons comparable à celui de la figure 1. Il est muni d'une autre variante du dispositif produisant le champ magnétique réglable à proximité de la cathode 1. Ce dispositif est intégré à l'anode 30 et non au wehnelt. Sur cette figure l'anode 30 qui entoure le wehnelt 2 comporte une cavité 32 à l'intérieur de laquelle on a placé un solénoïde 31. L'anode 30 est dans ce cas isolée du corps 5 du tube comme sur la figure 1. Elle est réalisée partiellement ou totalement dans un matériau métallique magnétique, tel que le fer doux ou l'acier doux. Une première extrémité 19 de l'anode 30 est solidaire des entretoises 7 et 13. L'autre extrémité 33 de l'anode 30, proche de la cathode 1, est réalisée dans un matériau différent du reste de l'anode. Ce matériau peut être du molybdène par exemple. La partie en matériau métallique magnétique sera plus ou moins longue, plus ou moins épaisse. Il convient aussi que cette partie ne chauffe pas trop et ne perde pas de perméabilité. De préférence, le matériau utilisé sera fabriqué sous vide, de manière à éviter tout dégazage intempestif.Figure 3 shows in section an electron gun comparable to that of Figure 1. It is provided with another variant of the device producing the adjustable magnetic field near the cathode 1. This device is integrated into the anode 30 and not into the wehnelt. In this figure the anode 30 which surrounds the wehnelt 2 comprises a cavity 32 inside which a solenoid 31 has been placed. The anode 30 is in this case isolated from the body 5 of the tube as in FIG. 1. It is made partially or completely in a magnetic metallic material, such as soft iron or mild steel. A first end 19 of the anode 30 is integral with the spacers 7 and 13. The other end 33 of the anode 30, close to the cathode 1, is made of a material different from the rest of the anode. This material can be molybdenum for example. The part made of magnetic metallic material will be more or less long, more or less thick. It is also advisable that this part does not heat too much and does not lose permeability. Preferably, the material used will be manufactured under vacuum, so as to avoid any untimely degassing.

Le solénoïde 31 pourra être placé plus ou moins près du faisceau 4 d'électrons suivant l'effet désiré sur les lignes de flux magnétique existant dans le canon. Ce solénoïde 32 sera alimenté grâce à une alimentation 36 référencée par rapport au potentiel de l'anode 30. Le courant pourra être commandé lors des essais grâce à des fibres optiques, par exemple. La référence 34 représente l'alimentation de la cathode 1 fournissant le potentiel - V₀. La référence 35 représente l'alimentation de l'anode 30 fournissant le potentiel -VA. L'alimentation 35 de l'anode et l'alimentation 36 du solénoïde seront munies chacune d'un transformateur d'isolement 37. Le solénoïde 31 est relié à son alimentation 36 grâce à un conducteur 38 inséré dans un conduit 39 qui passe à l'intérieur de l'anode 30 et qui débouche au niveau de son extrémité 19 à l'extérieur de l'enceinte 14 délimitée par les entretoises 7, 13.The solenoid 31 can be placed more or less close to the electron beam 4 according to the desired effect on the magnetic flux lines existing in the gun. This solenoid 32 will be supplied by a supply 36 referenced with respect to the potential of the anode 30. The current may be controlled during the tests by means of optical fibers, for example. Reference 34 represents the supply of cathode 1 supplying the potential - V₀. The reference 35 represents the supply of the anode 30 supplying the potential -V A. The supply 35 of the anode and the supply 36 of the solenoid will each be provided with an isolation transformer 37. The solenoid 31 is connected to its supply 36 by means of a conductor 38 inserted in a conduit 39 which passes to the inside the anode 30 and which opens at its end 19 outside the enclosure 14 delimited by the spacers 7, 13.

La figure 4 représente en coupe un canon comparable à celui de la figure 1. Il est muni d'une autre variante du dispositif produisant le champ magnétique réglable au voisinage de la cathode.Figure 4 shows in section a cannon comparable to that of Figure 1. It is provided with another variant of the device producing the adjustable magnetic field in the vicinity of the cathode.

Le dispositif produisant le champ magnétique réglable est constitué d'un solénoïde 40 placé en contact avec l'anode 41. Une première extrémité 42 de l'anode 41 est solidaire des entretoises 7, 13. C'est au niveau de cette première extrémité 42 que se fait le contact entre l'anode 41 et le solénoïde 40. Le solénoïde est placé à l'extérieur de l'enceinte 14.The device producing the adjustable magnetic field consists of a solenoid 40 placed in contact with the anode 41. A first end 42 of the anode 41 is integral with the spacers 7, 13. It is at this first end 42 that there is contact between the anode 41 and the solenoid 40. The solenoid is placed outside the enclosure 14.

Ce dispositif produisant le champ magnétique réglable peut être utilisé dans des canons fonctionnant à tension plus faible. Dans ce cas, le diamètre du canon est moins important et il devient plus difficile d'intégrer un solénoïde à l'intérieur de l'anode ou du whenelt.This device producing the adjustable magnetic field can be used in guns operating at lower voltage. In this case, the diameter of the barrel is less important and it becomes more difficult to integrate a solenoid inside the anode or the whenelt.

L'anode 41 sera dans un matériau métallique magnétique, soit partiellement, soit totalement, pour guider le flux magnétique du solénoïde vers une région à proximité immédiate de la cathode. Sur la figure elle est partiellement dans un matériau métallique magnétique. La deuxième extrémité 43, proche de la cathode 1 et entourant le faisceau électronique, est dans un autre matériau, du molybdène par exemple.The anode 41 will be made of a magnetic metallic material, either partially or completely, to guide the magnetic flux from the solenoid to a region in the immediate vicinity of the cathode. In the figure it is partially in a magnetic metallic material. The second end 43, close to the cathode 1 and surrounding the electron beam, is made of another material, molybdenum for example.

Le solénoïde est alimenté par une alimentation non représentée. Cette alimentation est référencée par rapport au potentiel de l'anode 41 comme dans le cas précédent.The solenoid is supplied by a supply, not shown. This supply is referenced with respect to the potential of the anode 41 as in the previous case.

La figure 5 représente en coupe, un canon à électrons comparable à celui de la figure 4. Il est muni d'une nouvelle variante du dispositif produisant le champ magnétique au voisinage de la cathode.FIG. 5 represents in section, an electron gun comparable to that of FIG. 4. It is provided with a new variant of the device producing the magnetic field in the vicinity of the cathode.

Sur cette figure, le dispositif produisant le champ magnétique est constitué d'un ou plusieurs aimants 50, aimantés au préalable.In this figure, the device producing the magnetic field consists of one or more magnets 50, magnetized beforehand.

Ces aimants sont placés en couronne à l'extérieur de l'enceinte 14 et sont en contact avec l'anode 51. Une première extrémité 52 de l'anode 51 est solidaire des entretoises 7, 13. C'est au niveau de cette première extrémité 52 que se fait le contact entre l'anode 51 et les aimants 50. Les aimants 50 sont disposés de manière à ce que leurs lignes d'induction soient dirigées vers l'intérieur de l'anode 51. Dans ce cas, l'anode 51 est réalisée totalement ou partiellement dans un matériau métallique magnétique. Sur la figure 5, on a représenté la deuxième extrémité 53 de l'anode 51, proche de la cathode 1, dans un autre matériau, du molybdène par exemple. Les aimants 50 sont portés au même potentiel que l'anode 51. Le nombre d'aimants 50 est quelconque. Il est possible de régler relativement finement le champ magnétique au voisinage de la cathode 1 en modifiant le nombre d'aimants 50 placés en couronne autour de l'anode 51 et leur position.These magnets are placed in a ring outside the enclosure 14 and are in contact with the anode 51. A first end 52 of the anode 51 is secured to the spacers 7, 13. It is at this first end 52 which makes contact between the anode 51 and the magnets 50. The magnets 50 are arranged so that their induction lines are directed towards the inside of the anode 51. In this case, the anode 51 is made wholly or partially in a magnetic metallic material. In Figure 5, there is shown the second end 53 of the anode 51, close to the cathode 1, in another material, molybdenum for example. The magnets 50 are brought to the same potential as the anode 51. The number of magnets 50 is arbitrary. It is possible to adjust the magnetic field relatively finely in the vicinity of the cathode 1 by modifying the number of magnets 50 placed in a ring around the anode 51 and their position.

Grace à l'invention, il sera même possible de supprimer le blindage extérieur au canon lorsque l'on place un solénoïde ou une pluralité d'aimants autour du canon.Thanks to the invention, it will even be possible to remove the shielding outside the barrel when a solenoid or a plurality of magnets are placed around the barrel.

L'invention n'est pas limitée aux exemples décrits. De nombreuses variantes peuvent intervenir au niveau de la forme ou de la position du dispositif produisant un champ magnétique à proximité de la cathode sans sortir du cadre de l'invention. Il suffit que l'une des électrodes autre que la cathode, soit munie du dispositif produisant un champ magnétique au voisinage de la cathode.The invention is not limited to the examples described. Many variants can occur in terms of the shape or position of the device producing a magnetic field near the cathode without departing from the scope of the invention. It suffices that one of the electrodes other than the cathode is provided with the device producing a magnetic field in the vicinity of the cathode.

Claims (14)

1 - Canon à électrons comportant plusieurs électrodes(1,2,30) parmi lesquelles une cathode (1), caractérisé en ce qu'il comporte en outre un dispositif (31) de production d'un champ magnétique, ce dispositif (31) coopérant avec une électrode (2,30) autre que la cathode (1) et proche de la cathode pour établir un champ magnétique contrôlé au voisinage immédiat de la cathode.1 - electron gun comprising several electrodes (1,2,30) including a cathode (1), characterized in that it further comprises a device (31) for producing a magnetic field, this device (31) cooperating with an electrode (2.30) other than the cathode (1) and close to the cathode to establish a controlled magnetic field in the immediate vicinity of the cathode. 2 - Canon à électrons selon la revendication 1, caractérisé en ce que le champ magnétique produit par le dispositif (31) est réglable.2 - electron gun according to claim 1, characterized in that the magnetic field produced by the device (31) is adjustable. 3 - Canon à électrons selon l'une des revendications 1 ou 2, caractérisé en ce que le dispositif est un solénoïde (31) placé à l'intérieur du canon et en ce que ladite électrode (30) sert de support à ce solénoïde (31).3 - electron gun according to one of claims 1 or 2, characterized in that the device is a solenoid (31) placed inside the barrel and in that said electrode (30) serves as a support for this solenoid ( 31). 4 - Canon à électrons selon la revendication 3, caractérisé en ce que le solénoïde (31) est placé dans une cavité (32) aménagée à l'intérieur de l'électrode (30) qui lui sert de support, cette cavité (32) étant sans contact avec l'intérieur du canon mais pouvant communiquer avec l'extérieur.4 - electron gun according to claim 3, characterized in that the solenoid (31) is placed in a cavity (32) arranged inside the electrode (30) which serves as a support, this cavity (32) being without contact with the inside of the barrel but being able to communicate with the outside. 5 - Canon à électrons selon l'une des revendications 3 ou 4, caractérisé en ce que le solénoïde (31) est relié à une alimentation électrique (36) dont le potentiel est réferencé par rapport à celui de l'électrode (30) qui sert à le supporter.5 - electron gun according to one of claims 3 or 4, characterized in that the solenoid (31) is connected to a power supply (36) whose potential is referenced relative to that of the electrode (30) which serves to support it. 6 - Canon à électrons selon l'une des revendlcations 1 ou 2, caractérisé en ce que le dispositif est constitué par un ou plusieurs aimants (50) permanents.6 - Electron gun according to one of claims 1 or 2, characterized in that the device consists of one or more permanent magnets (50). 7 - Canon à électrons selon l'une des revendications 1 à 6, caractérisé en ce que l'électrode (30) qui coopère avec le dispositif de production d'un champ magnétique est en matériau totalement ou partiellement magnétique permettant de guider un flux magnétique à proximité de la face émissive de la cathode (1).7 - electron gun according to one of claims 1 to 6, characterized in that the electrode (30) which cooperates with the device for producing a magnetic field is made of totally or partially magnetic material making it possible to guide a magnetic flux near the emissive face of the cathode (1). 8 - Canon à électrons selon la revendication 7, caractérisé en ce que le matériau est du fer doux ou de l'acier doux.8 - electron gun according to claim 7, characterized in that the material is soft iron or mild steel. 9 - Canon à électrons selon l'une des revendications 7 sou 8, caractérisé en ce que le dispositif (50) de production d'un champ magnétlque est placé à l'extérieur du canon, en contact magnétique avec une extrémité (52) de l'électrode (51).9 - electron gun according to one of claims 7 or 8, characterized in that the device (50) for producing a magnetic field is placed outside the gun, in magnetic contact with one end (52) of the electrode (51). 10 - Canon à électrons selon l'une des revendications 1 à 9, caractérisé en ce que l'électrode coopérant avec le dispositif (31,40,50) est l'anode (30,41,51) du canon.10 - electron gun according to one of claims 1 to 9, characterized in that the electrode cooperating with the device (31,40,50) is the anode (30,41,51) of the gun. 11 - Canon à électrons selon l'une des revendications 1 à 9, caractérisé en ce que l'électrode coopérant avec le dispositif (27) est le wehnelt (22) du canon.11 - electron gun according to one of claims 1 to 9, characterized in that the electrode cooperating with the device (27) is the wehnelt (22) of the gun. 12 - Canon à électrons selon la revendication 11, caractérisé en ce que le dispositif (27) est monté en série avec un filament (20) destiné à chauffer la cathode (1), lorsque ledit dispositif (27) est un solénoïde.12 - electron gun according to claim 11, characterized in that the device (27) is mounted in series with a filament (20) intended to heat the cathode (1), when said device (27) is a solenoid. 13 - Tube électronique à interaction longitudinale, caractérisé en ce qu'il comporte un canon à électrons selon l'une des revendications 1 à 12.13 - Electronic tube with longitudinal interaction, characterized in that it comprises an electron gun according to one of claims 1 to 12. 14 - Accélerateur de particules, caractérisé en ce qu'il comporte un canon à électrons selon l'une des revendications 1 à 12.14 - Particle accelerator, characterized in that it comprises an electron gun according to one of claims 1 to 12.
EP90400089A 1989-01-17 1990-01-12 Electron gun comprising a device producing a magnetic field in the proximity of the cathode Withdrawn EP0379403A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8900484A FR2641899A1 (en) 1989-01-17 1989-01-17 ELECTRON GUN WITH AN ACTIVE DEVICE PRODUCING A MAGNETIC FIELD IN THE VICINITY OF THE CATHODE
FR8900484 1989-01-17

Publications (1)

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EP0379403A1 true EP0379403A1 (en) 1990-07-25

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EP90400089A Withdrawn EP0379403A1 (en) 1989-01-17 1990-01-12 Electron gun comprising a device producing a magnetic field in the proximity of the cathode

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US (1) US5109179A (en)
EP (1) EP0379403A1 (en)
JP (1) JPH02227950A (en)
FR (1) FR2641899A1 (en)

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EP0589606A2 (en) * 1992-09-24 1994-03-30 Eev Limited Electron gun arrangements

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JP3325982B2 (en) * 1993-12-27 2002-09-17 株式会社東芝 Magnetic field immersion type electron gun
FR2737340B1 (en) * 1995-07-28 1997-08-22 Thomson Tubes Electroniques MULTI-BEAM ELECTRONIC TUBE WITH IMPROVED CAVITY / BEAM COUPLING
FR2756970B1 (en) * 1996-12-10 2003-03-07 Thomson Tubes Electroniques LONGITUDINAL INTERACTION MICROWAVE TUBE WITH OUTPUT BEYOND THE COLLECTOR
FR2764730B1 (en) * 1997-06-13 1999-09-17 Thomson Tubes Electroniques ELECTRONIC CANON FOR MULTI-BEAM ELECTRONIC TUBE AND MULTI-BEAM ELECTRONIC TUBE EQUIPPED WITH THIS CANON
FR2780809B1 (en) 1998-07-03 2003-11-07 Thomson Tubes Electroniques MULTI-BEAM ELECTRONIC TUBE WITH MAGNETIC FIELD OF CORRECTION OF BEAM TRAJECTORY
US6392333B1 (en) * 1999-03-05 2002-05-21 Applied Materials, Inc. Electron gun having magnetic collimator
FR2803454B1 (en) * 1999-12-30 2003-05-16 Thomson Tubes Electroniques MICROWAVE PULSE GENERATOR WITH INTEGRATED PULSE COMPRESSOR
JP3996442B2 (en) * 2002-05-27 2007-10-24 Ｎｅｃマイクロ波管株式会社 Electron gun
JP5835822B1 (en) * 2014-06-30 2015-12-24 Ｎｅｃネットワーク・センサ株式会社 High frequency circuit system

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Also Published As

Publication number Publication date
FR2641899A1 (en) 1990-07-20
US5109179A (en) 1992-04-28
JPH02227950A (en) 1990-09-11

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