EP0362021A1 - Fly-path correction device in an electron tube - Google Patents

Fly-path correction device in an electron tube Download PDF

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Publication number
EP0362021A1
EP0362021A1 EP89402559A EP89402559A EP0362021A1 EP 0362021 A1 EP0362021 A1 EP 0362021A1 EP 89402559 A EP89402559 A EP 89402559A EP 89402559 A EP89402559 A EP 89402559A EP 0362021 A1 EP0362021 A1 EP 0362021A1
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Prior art keywords
axis
auxiliary
disc
field
drift
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German (de)
French (fr)
Inventor
Georges Mourier
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Thales SA
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Thomson CSF SA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • 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

Definitions

  • the present invention relates to a trajectory correction device for an electronic tube. It applies in particular to multibeam tubes and in particular to microwave tubes of the klystron genus.
  • Figure 1 shows schematically a multibeam electronic tube according to the prior art.
  • the structure is of revolution around a z axis. Beams of electrons, six in number in this example, ie 10, 11, 12, 13, 14, 15, are produced by means not shown and pass through holes A, B, C, D, E, F respectively , drilled in a first disc 20 centered on the z axis and arranged in a plane (x, y) and holes A ′, B ′, C ′, D ′, E ′, F ′ drilled in a second disc 22 centered also on the z axis and located in a plane (x ′, y ′).
  • Each pair A and A ′, B and B ′, C and C ′, D and D ′, E and E ′, F and F ′ is centered on a straight line parallel to the z axis.
  • the electrons are guided by a so-called main magnetic field, which is generated by a system 24 of coils having the z axis as the axis of symmetry and traversed by direct currents.
  • the main magnetic field also admits the z axis as the axis of revolution.
  • This main magnetic field is essentially directed along the axis z between the two disks 20 and 22, but the axial component Bz of this field varies as a function of the distance from the axis. In other words, the axial component of the field has a radial gradient.
  • each beam undergoes a radial drift ⁇ R and an azimuthal drift ⁇ .
  • the electron beam 10 tends to strike the disc 22 at A ⁇ , instead of passing through A ′.
  • the situation is similar for the other beams.
  • the tubes thus designed still have a drawback which is that they have an azimuthal drift, of amplitude ⁇ .
  • the present invention aims to remedy this drawback by providing the means to eliminate this azimuthal drift.
  • the invention recommends the use of coils and / or additional ferromagnetic parts capable of creating a magnetic correction field, which is added to the main magnetic field and brings the electrons back into space A ′.
  • the present invention relates to a trajectory correction device for an electronic tube, this tube comprising a main means able to generate a main magnetic field of revolution around an axis and means for creating at least one electron beam spaced from this axis and passing successively through a first hole drilled in a first disc, then through a second hole drilled in a second disc, this device being characterized in that it comprises at least one thin auxiliary means centered on the axis of revolution and able to create an auxiliary magnetic correction field having the same axis of revolution as the main field and having a radial gradient, this auxiliary field correcting the effects of azimuthal drift of the beam between the first and second holes, due drift non-uniformity of the main magnetic field between the two holes.
  • the auxiliary correction means consists of first and second coils traversed by currents and placed in the vicinity of the planes of the first and second holes.
  • the auxiliary correction means consists of a coil traversed by a current and placed in the median plane relative to the planes of the first and second holes.
  • the auxiliary means consists of a first coil placed in the vicinity of the plane of the first hole, a second coil placed in the vicinity of the plane of the second hole and a third coil placed in the median plane, these coils being traversed by currents.
  • the auxiliary correction means consists of a ferromagnetic part placed in the median plane relative to the planes of the first and second holes, the axis of revolution being the axis of symmetry of this part.
  • This part can be a disc, a cylinder, or a torus.
  • FIG. 3 schematically represents the section of a multibeam tube provided with a correction device according to the invention.
  • An electron beam 10 comes from a means 32 (cathode or other) and has its average trajectory parallel to the axis z, axis of symmetry of the system. This trajectory is moved away from the z axis.
  • the beam passes through a first hole A drilled in a first disc 20 located in a plane (x, y) and must pass through a second hole A ′ drilled in a second disc 22 located in a plane (x ′, y ′).
  • a main magnetic field which satisfies the following conditions: - in A and A ′, the amplitude of the field is the same, - the fluxes of the field through the surfaces of the circles centered on z and passing through A and A ′ are identical.
  • the azimuthal drift is compensated, according to the invention, by an auxiliary trajectory correction means 30 capable of creating a magnetic field correcting the effects of azimuthal drift of the trajectory between the first and the second space A, A ′.
  • Means 34 are provided for adjusting the current flowing through the coils of the main system 24 to maintain the value of the flux of the total magnetic field despite the auxiliary magnetic field due to the means 30.
  • the trajectory of the electrons is not in fact rectilinear between A and A ′. It winds in a helix around the magnetic field. Two cases can occur depending on the energies involved. In the first case, it is assumed that the electrons complete a large number of orbits between the two discs. In the second case, we suppose on the contrary that they do little.
  • the inventor has shown that the azimuthal drift of the electrons is due to a force passing through the z axis, a force which communicates to the electrons a tangential speed proportional to the gradient of the axial component B z of the field along the radius r.
  • the azimuth speed is proportional to ⁇ B z / ⁇ r.
  • the total azimuthal drift ⁇ is therefore proportional to the integral of this quantity between the spaces A and A ′.
  • - V b being the speed of rotation of an electron around the magnetic field
  • - V z being the speed of movement of an electron along the direction of the z axis
  • - B being the amplitude of the applied magnetic field and B z its component in the direction z
  • r the distance to the axis.
  • the electrons of a beam travel only a few orbits between A and A ′.
  • the inventor then showed that the azimuthal drift ⁇ between A and A ′ took the form: - where ⁇ is the value of the flux of the magnetic field crossing the circle of radius r, centered on the axis of symmetry z and passing through the electron, - ⁇ o is the value of ⁇ at an origin point of the drift ⁇ , and - q and m are the charge and the mass of the electron.
  • ⁇ - ⁇ o can be positive or negative depending on the nature of the magnetic fields used.
  • an auxiliary field with a strong radial gradient is voluntarily created so that the drift induced by this auxiliary gradient compensates for the drift caused by the non-uniformity of the main field.
  • auxiliary path correction means 30 The function of the auxiliary path correction means 30 is to satisfy these conditions. This means is of thin or flat shape because it is under these conditions that a field of small amplitude but of strong gradient is obtained.
  • FIG. 4 shows schematically and in section a first embodiment of a device according to the invention.
  • the auxiliary means 30 consists of two flat coils 36 and 38 each supplied with current by a generator 40, 42.
  • the coil 38 is located in the vicinity of the plane (x, y) containing the first disk traversed by the electron beam.
  • the coil 36 is located in the vicinity of the plane x ′, y ′ containing the second disc. These coils 36, 38 are parallel to these planes (x, y) and (x ′, y ′) and centered on the z axis.
  • the gradient of the axial field induced by a coil is positive in its plane, inside the coil. On the other hand, this gradient is negative in the median plane of a system with two sufficiently distant coils. We can therefore cancel the effect of the component ⁇ B z / ⁇ r along a path from A to A ′ by adjusting the dimensions and the spacing of the two coils 36 and 38.
  • the coils 36, 38 therefore induce magnetic compensation fields at the ends of the area between the disks 20 and 22. They then allow compensation for the azimuthal drift in the case where the beam electrons describe a large number of orbits on their trajectory.
  • FIG. 5 schematically shows a sectional view of another embodiment of a device according to the invention.
  • the means 30 consists of a flat coil 44 traversed by a current generated by a generator 46.
  • This coil 44 is placed in the median plane M with respect to the planes (x, y) and (x ′, y ′).
  • the distance separating two diametrically opposite spaces (such as A and D in FIG. 5) must be less than the diameter of the coil 44. But the diameter of the latter is such that the coil is very close to the path of the electrons.
  • the coil 44 can have a diameter 10% greater than the distance between A and D for example.
  • This coil 44 induces a magnetic field of compensation at the level of the median plane M. It allows the compensation of the azimuthal drift in the case where the electrons describe few orbits throughout their trajectory.
  • a similar result can be obtained by a ferromagnetic part 48 placed in the median plane M with respect to the planes (x, y) and (x ′, y ′), the axis z being a axis of symmetry for this part.
  • This part can be a disc, a cylinder or a torus for example.
  • the diameter of this piece is less than the distance between two diametrically opposite spaces (A, D in Figure 6).
  • Figure 7 a device which combines the devices of Figures 4 and 5. This device applies to all cases, that the electrons describe few or many orbits on their trajectory. It applies particularly well to intermediate cases.
  • the auxiliary correction means 30 therefore consists of two coils 36, 38 connected respectively to current generators 40, 42 and to a coil 44 of smaller diameter connected to a current generator 46.
  • two coils 36, 38 are each arranged in one of the planes (x, y) and (x ′, y ′), the coil 44 being located in the median plane M with respect to these planes.

Abstract

This device comprises an auxiliary fly-path correction means (30) able to create a magnetic field correcting the azimuthal drift effects of the beam between a first and a second disc (20, 22), a drift which is due to the non-uniformity of the main field between the two discs. These means (30) can comprise several coils (36,38,44) traversed by currents and placed in the vicinity of the discs or between the latter. <??>Application to multi-beam klystrons. <IMAGE>

Description

La présente invention a pour objet un dispositif correcteur de trajectoires pour tube électronique. Elle s'applique notamment aux tubes multifaisceau et en particulier aux tubes hyperfréquences du genre klystron.The present invention relates to a trajectory correction device for an electronic tube. It applies in particular to multibeam tubes and in particular to microwave tubes of the klystron genus.

La figure 1 montre de manière schématique un tube électronique multifaisceau selon l'art antérieur.Figure 1 shows schematically a multibeam electronic tube according to the prior art.

La structure est de révolution autour d'un axe z. Des faisceaux d'électrons, au nombre de six dans cet exemple, soit 10, 11, 12, 13, 14, 15, sont produits par un moyen non représenté et traversent respectivement des trous A, B, C, D, E, F, percés dans un premier disque 20 centré sur l'axe z et disposé dans un plan (x, y) et des trous A′, B′, C′, D′, E′, F′ percés dans un second disque 22 centré lui aussi sur l'axe z et situé dans un plan (x′, y′).The structure is of revolution around a z axis. Beams of electrons, six in number in this example, ie 10, 11, 12, 13, 14, 15, are produced by means not shown and pass through holes A, B, C, D, E, F respectively , drilled in a first disc 20 centered on the z axis and arranged in a plane (x, y) and holes A ′, B ′, C ′, D ′, E ′, F ′ drilled in a second disc 22 centered also on the z axis and located in a plane (x ′, y ′).

Chaque couple A et A′, B et B′, C et C′, D et D′, E et E′, F et F′ est centré sur une droite parallèle à l'axe z.Each pair A and A ′, B and B ′, C and C ′, D and D ′, E and E ′, F and F ′ is centered on a straight line parallel to the z axis.

Les électrons sont guidés par un champ magnétique dit principal, qui est engendré par un système 24 de bobines ayant l'axe z pour axe de symétrie et parcourues par des courants continus. Le champ magnétique principal admet aussi l'axe z comme axe de révolution.The electrons are guided by a so-called main magnetic field, which is generated by a system 24 of coils having the z axis as the axis of symmetry and traversed by direct currents. The main magnetic field also admits the z axis as the axis of revolution.

Ce champ magnétique principal est essentiellement dirigé selon l'axe z entre les deux disques 20 et 22, mais la composante axiale Bz de ce champ varie en fonction de la distance à l'axe. En d'autres termes, la composante axiale du champ présente un gradient radial.This main magnetic field is essentially directed along the axis z between the two disks 20 and 22, but the axial component Bz of this field varies as a function of the distance from the axis. In other words, the axial component of the field has a radial gradient.

Cette non uniformité du champ magnétique ainsi que la position excentrée des faisceaux provoquent une dérive de la trajectoire des électrons.This non-uniformity of the magnetic field and the eccentric position of the beams cause a drift in the trajectory of the electrons.

De façon plus précise la trajectoire moyenne des électrons n'est pas dirigée parallèlement à l'axe z. Chaque faisceau subit une dérive radiale ΔR et une dérive azimutale Δφ.More precisely, the average trajectory of the electrons is not directed parallel to the z axis. Each beam undergoes a radial drift ΔR and an azimuthal drift Δφ.

Comme on le voit sur la figure 2, le faisceau d'électrons 10 a tendance à venir frapper le disque 22 en A˝, au lieu de passer par A′. La situation est analogue pour les autres faisceaux.As can be seen in FIG. 2, the electron beam 10 tends to strike the disc 22 at A˝, instead of passing through A ′. The situation is similar for the other beams.

Il est connu que la dérive radiale ΔR peut être annulée. Il suffit que les flux du champ à travers des cercles passant par les trous A et A′ (respectivement B et B′, C et C′, D et D′, E et E′, F et F′) soient identiques, conformément à la théorie de BUSCH.It is known that the radial drift ΔR can be canceled. It suffices that the fluxes of the field through circles passing through holes A and A ′ (respectively B and B ′, C and C ′, D and D ′, E and E ′, F and F ′) are identical, in accordance to BUSCH theory.

Pour le bon fonctionnement du tube, on impose alors au champ magnétique principal deux conditions : son amplitude doit être sensiblement la même au niveau des trous homologues A et A′, B et B′, ... et les flux à travers les cercles passant par ces espaces doivent être identiques.For the proper functioning of the tube, two main conditions are then imposed on the main magnetic field: its amplitude must be substantially the same at the level of the homologous holes A and A ′, B and B ′, ... and the fluxes passing through the circles by these spaces must be identical.

Mais les tubes ainsi conçus présentent encore un inconvénient qui est de présenter une dérive azimutale, d'amplitude Δφ.However, the tubes thus designed still have a drawback which is that they have an azimuthal drift, of amplitude Δφ.

La présente invention a pour but de remédier à cet inconvénient en donnant les moyens de supprimer cette dérive azimutale.The present invention aims to remedy this drawback by providing the means to eliminate this azimuthal drift.

Pour cela, l'invention préconise l'emploi de bobines et/ou de pièces ferromagnétiques supplémentaires aptes à créer un champ magnétique de correction, qui s'ajoute au champ magnétique principal et ramène les électrons dans l'espace A′.For this, the invention recommends the use of coils and / or additional ferromagnetic parts capable of creating a magnetic correction field, which is added to the main magnetic field and brings the electrons back into space A ′.

De façon plus précise, la présente invention concerne un dispositif correcteur de trajectoires pour tube électronique, ce tube comprenant un moyen principal apte à engendrer un champ magnétique principal de révolution autour d'un axe et des moyens pour créer au moins un faisceau d'électrons écarté de cet axe et passant successivement à travers un premier trou percé dans un premier disque, puis à travers un second trou percé dans un second disque, ce dispositif étant caractérisé par le fait qu'il comprend au moins un moyen auxiliaire mince centré sur l'axe de révolution et apte à créer un champ magnétique auxiliaire de correction ayant même axe de révolution que le champ principal et présentant un gradient radial, ce champ auxiliaire corrigeant les effets de dérive azimutale du faisceau entre le premier et le second trous, dérive due à la non uniformité du champ magnétique principal entre les deux trous.More specifically, the present invention relates to a trajectory correction device for an electronic tube, this tube comprising a main means able to generate a main magnetic field of revolution around an axis and means for creating at least one electron beam spaced from this axis and passing successively through a first hole drilled in a first disc, then through a second hole drilled in a second disc, this device being characterized in that it comprises at least one thin auxiliary means centered on the axis of revolution and able to create an auxiliary magnetic correction field having the same axis of revolution as the main field and having a radial gradient, this auxiliary field correcting the effects of azimuthal drift of the beam between the first and second holes, due drift non-uniformity of the main magnetic field between the two holes.

Dans un premier mode de réalisation, le moyen auxiliaire de correction se compose d'une première et d'une seconde bobines parcourues par des courants et placées au voisinage des plans des premier et second trous.In a first embodiment, the auxiliary correction means consists of first and second coils traversed by currents and placed in the vicinity of the planes of the first and second holes.

Dans un autre mode de réalisation, le moyen auxiliaire de correction se compose d'une bobine parcourue par un courant et placée dans le plan médian par rapport aux plans du premier et du second trous.In another embodiment, the auxiliary correction means consists of a coil traversed by a current and placed in the median plane relative to the planes of the first and second holes.

Dans une variante de réalisation, le moyen auxiliaire se compose d'une première bobine placée au voisinage du plan du premier trou, d'une seconde bobine placée au voisinage du plan du second trou et d'une troisième bobine placée dans le plan médian, ces bobines étant parcourues par des courants.In an alternative embodiment, the auxiliary means consists of a first coil placed in the vicinity of the plane of the first hole, a second coil placed in the vicinity of the plane of the second hole and a third coil placed in the median plane, these coils being traversed by currents.

Dans un autre mode de réalisation, le moyen auxiliaire de correction se compose d'une pièce ferromagnétique placée dans le plan médian par rapport aux plans du premier et du second trous, l'axe de révolution étant axe de symétrie de cette pièce. Cette pièce peut être un disque, un cylindre, ou un tore.In another embodiment, the auxiliary correction means consists of a ferromagnetic part placed in the median plane relative to the planes of the first and second holes, the axis of revolution being the axis of symmetry of this part. This part can be a disc, a cylinder, or a torus.

Les caractéristiques et avantages de l'invention apparaîtront mieux à la lumière de la description qui suit, d'exemples donnés à titre explicatif et nullement limitatif. Cette description se réfère à des dessins annexés sur lesquels :

  • - la figure 1, déjà décrite, représente schématiquement, un tube électronique multifaisceau selon l'art antérieur ;
  • - la figure 2, déjà décrite, est une vue schématique d'un disque montrant la dérive radiale et azimutale d'un faisceau d'électrons selon l'art antérieur ;
  • - la figure 3 représente schématiquement une vue en coupe d'un tube multifaisceau muni d'un dispositif conforme à l'invention ;
  • - la figure 4 représente schématiquement une vue en coupe d'un mode de réalisation d'un dispositif conforme à l'invention ;
  • - la figure 5 représente schématiquement une vue en coupe d'un autre mode de réalisation d'un dispositif conforme à l'invention ;
  • - la figure 6 représente schématiquement une vue en coupe d'une variante de réalisation d'un dispositif conforme à l'invention ;
  • - la figure 7 représente schématiquement une vue en coupe d'un autre mode de réalisation d'un dispositif conforme à l'invention ;
  • - la figure 8 représente schématiquement une vue en coupe d'une autre variante de réalisation d'un dispositif conforme à l'invention.
The characteristics and advantages of the invention will appear better in the light of the following description, of examples given by way of explanation and in no way limitative. This description refers to attached drawings in which:
  • - Figure 1, already described, schematically shows an electronic multibeam tube according to the prior art;
  • - Figure 2, already described, is a schematic view of a disc showing the radial and azimuthal drift of an electron beam according to the prior art;
  • - Figure 3 shows schematically a sectional view of a multibeam tube provided with a device according to the invention;
  • - Figure 4 shows schematically a sectional view of an embodiment of a device according to the invention;
  • - Figure 5 shows schematically a sectional view of another embodiment of a device according to the invention;
  • - Figure 6 schematically shows a sectional view of an alternative embodiment of a device according to the invention;
  • - Figure 7 schematically shows a sectional view of another embodiment of a device according to the invention;
  • - Figure 8 shows schematically a sectional view of another alternative embodiment of a device according to the invention.

La figure 3 représente schématiquement la coupe d'un tube multifaisceau muni d'un dispositif de correction conforme à l'invention.FIG. 3 schematically represents the section of a multibeam tube provided with a correction device according to the invention.

Un faisceau d'électrons 10 est issu d'un moyen 32 (cathode ou autre) et a sa trajectoire moyenne parallèle à l'axe z, axe de symétrie du système. Cette trajectoire est écartée de l'axe z.An electron beam 10 comes from a means 32 (cathode or other) and has its average trajectory parallel to the axis z, axis of symmetry of the system. This trajectory is moved away from the z axis.

Le faisceau traverse un premier trou A percé dans un premier disque 20 situé dans un plan (x, y) et doit passer par un second trou A′ percé dans un second disque 22 situé dans un plan (x′, y′). Pour cela, il est guidé par un champ magnétique principal qui satisfait aux conditions suivantes :
- en A et A′, l'amplitude du champ est la même,
- les flux du champ à travers les surfaces des cercles centrés sur z et passant par A et A′ sont identiques.The beam passes through a first hole A drilled in a first disc 20 located in a plane (x, y) and must pass through a second hole A ′ drilled in a second disc 22 located in a plane (x ′, y ′). For this, it is guided by a main magnetic field which satisfies the following conditions:
- in A and A ′, the amplitude of the field is the same,
- the fluxes of the field through the surfaces of the circles centered on z and passing through A and A ′ are identical.

On annule ainsi la dérive radiale du faisceau d'électrons (respect des conditions imposées par le théorème de BUSCH).One thus cancels the radial drift of the electron beam (respect of the conditions imposed by the theorem of BUSCH).

La dérive azimutale est compensée, selon l'invention, par un moyen auxiliaire de correction de trajectoire 30 apte à créer un champ magnétique corrigeant les effets de dérive azimutale de la trajectoire entre le premier et le second espace A, A′.The azimuthal drift is compensated, according to the invention, by an auxiliary trajectory correction means 30 capable of creating a magnetic field correcting the effects of azimuthal drift of the trajectory between the first and the second space A, A ′.

Des moyens 34 sont prévus pour ajuster le courant qui parcourt les bobines du système principal 24 pour conserver la valeur du flux du champ magnétique total malgré le champ magnétique auxiliaire dû au moyen 30.Means 34 are provided for adjusting the current flowing through the coils of the main system 24 to maintain the value of the flux of the total magnetic field despite the auxiliary magnetic field due to the means 30.

La trajectoire des électrons n'est pas en fait rectiligne entre A et A′. Elle s'enroule en hélice autour du champ magnétique. Deux cas peuvent se produire selon les énergies mises en jeu. Dans le premier cas, on suppose que les électrons accomplisssent un grand nombre d'orbites entre les deux disques. Dans le second cas, on suppose au contraire qu'ils en accomplissent peu.The trajectory of the electrons is not in fact rectilinear between A and A ′. It winds in a helix around the magnetic field. Two cases can occur depending on the energies involved. In the first case, it is assumed that the electrons complete a large number of orbits between the two discs. In the second case, we suppose on the contrary that they do little.

Dans le premier cas, l'inventeur a montré que la dérive azimutale des électrons était due à une force passant par l'axe z, force qui communique aux électrons une vitesse tangentielle proportionnelle au gradient de la composante axiale Bz du champ le long du rayon r. En d'autres termes, la vitesse azimutale est proportionnelle à δBz/ δr.In the first case, the inventor has shown that the azimuthal drift of the electrons is due to a force passing through the z axis, a force which communicates to the electrons a tangential speed proportional to the gradient of the axial component B z of the field along the radius r. In other words, the azimuth speed is proportional to δB z / δr.

La dérive azimutale totale Δφ est donc proportionnelle à l'intégrale de cette grandeur entre les espaces A et A′.The total azimuthal drift Δφ is therefore proportional to the integral of this quantity between the spaces A and A ′.

De façon plus précise, on a :

Figure imgb0001
- Vb étant la vitesse de rotation d'un électron autour du champ magnétique,
- Vz étant la vitesse de déplacement d'un électron selon la direction de l'axe z,
- B étant l'amplitude du champ magnétique appliqué et Bz sa composante dans la direction z, et r la distance à l'axe.More precisely, we have:
Figure imgb0001
 - V b being the speed of rotation of an electron around the magnetic field,
- V z being the speed of movement of an electron along the direction of the z axis,
- B being the amplitude of the applied magnetic field and B z its component in the direction z, and r the distance to the axis.

Dans le second cas, les électrons d'un faisceau ne parcourent que peu d'orbites entre A et A′. L'inventeur a montré alors que la dérive azimutale Δφ entre A et A′ prenait la forme :

Figure imgb0002
- où ⌀ est la valeur du flux du champ magnétique traversant le cercle de rayon r, centré sur l'axe de symétrie z et passant par l'électron,
- ⌀o est la valeur de ⌀ en un point origine de la dérive Δφ, et
- q et m sont la charge et la masse de l'électron.In the second case, the electrons of a beam travel only a few orbits between A and A ′. The inventor then showed that the azimuthal drift Δφ between A and A ′ took the form:
Figure imgb0002
 - where ⌀ is the value of the flux of the magnetic field crossing the circle of radius r, centered on the axis of symmetry z and passing through the electron,
- ⌀ o is the value of ⌀ at an origin point of the drift Δφ, and
- q and m are the charge and the mass of the electron.

Les termes m et Vz sont sensiblement constants en pratique. ⌀ - ⌀o peut être positif ou négatif suivant la nature des champs magnétiques mis en oeuvre.The terms m and V z are substantially constant in practice. ⌀ - ⌀ o can be positive or negative depending on the nature of the magnetic fields used.

L'intégrale de ⌀ - ⌀o sur un parcours allant de A à A′ doit être rendue nulle.The integral of ⌀ - ⌀ o on a path from A to A ′ must be made null.

En particulier, si l'on se place dans l'approximation dite des "lentilles minces", on montre que :

Figure imgb0003
In particular, if we place ourselves in the so-called "thin lens" approximation, we show that:
Figure imgb0003

L'annulation de la dérive azimutale (Δφ = O) implique que la valeur moyenne du flux ⌀ soit égale à ⌀o même si, localement, sa valeur est différente de ⌀o.The cancellation of the azimuthal drift (Δφ = O) implies that the mean value of the flux ⌀ is equal to ⌀ o even if, locally, its value is different from ⌀ o .

On constate ainsi que la compensation de la dérive azimutale aboutit, dans le premier cas, à des conditions aux extrémités sur les trajectoires, et, dans le second cas, à des conditions de moyenne sur les trajectoires. Ces conditions sont par ailleurs compatibles.It can thus be seen that the compensation for the azimuthal drift results, in the first case, in conditions at the ends on the trajectories, and, in the second case, in conditions of average on the trajectories. These conditions are also compatible.

En d'autres termes, selon l'invention, on crée volontairement un champ auxiliaire à fort gradient radial pour que la dérive induite par ce gradient auxiliaire compense la dérive occasionnée par la non uniformité du champ principal.In other words, according to the invention, an auxiliary field with a strong radial gradient is voluntarily created so that the drift induced by this auxiliary gradient compensates for the drift caused by the non-uniformity of the main field.

La fonction du moyen 30 auxiliaire de correction de trajectoire est de satisfaire à ces conditions. Ce moyen est de forme mince ou plate car c'est dans ces conditions qu'on obtient un champ de faible amplitude mais de fort gradient.The function of the auxiliary path correction means 30 is to satisfy these conditions. This means is of thin or flat shape because it is under these conditions that a field of small amplitude but of strong gradient is obtained.

La figure 4 représente schématiquement et en coupe un premier mode de réalisation d'un dispositif conforme à l'invention. Le moyen auxiliaire 30 consiste en deux bobines plates 36 et 38 alimentées en courant chacune par un générateur 40, 42. La bobine 38 est située au voisinage du plan (x, y) contenant le premier disque traversé par le faisceau d'électrons. La bobine 36 est située au voisinage du plan x′, y′ contenant le second disque. Ces bobines 36, 38 sont parallèles à ces plans (x, y) et (x′, y′) et centrées sur l'axe z.Figure 4 shows schematically and in section a first embodiment of a device according to the invention. The auxiliary means 30 consists of two flat coils 36 and 38 each supplied with current by a generator 40, 42. The coil 38 is located in the vicinity of the plane (x, y) containing the first disk traversed by the electron beam. The coil 36 is located in the vicinity of the plane x ′, y ′ containing the second disc. These coils 36, 38 are parallel to these planes (x, y) and (x ′, y ′) and centered on the z axis.

Le gradient du champ axial induit par une bobine est positif dans son plan, à l'intérieur de la bobine. Par contre, ce gradient est négatif dans le plan médian d'un système à deux bobines suffisamment éloignées. On peut donc annuler l'effet de la composante δBz/ δr le long d'un trajet de A vers A′ en ajustant les dimensions et l'écartement des deux bobines 36 et 38.The gradient of the axial field induced by a coil is positive in its plane, inside the coil. On the other hand, this gradient is negative in the median plane of a system with two sufficiently distant coils. We can therefore cancel the effect of the component δB z / δr along a path from A to A ′ by adjusting the dimensions and the spacing of the two coils 36 and 38.

Les bobines 36, 38 induisent donc des champs magnétiques de compensation aux extrémités de la zone située entre les disques 20 et 22. Elles permettent alors la compensation de la dérive azimutale dans le cas où les électrons des faisceaux décrivent un grand nombre d'orbites sur leur trajectoire.The coils 36, 38 therefore induce magnetic compensation fields at the ends of the area between the disks 20 and 22. They then allow compensation for the azimuthal drift in the case where the beam electrons describe a large number of orbits on their trajectory.

L'homme de l'art sait établir, par le calcul numérique, les relations entre les dimensions des bobines et les champs et adapter le dispositif à chaque cas particulier. La variation de Hz autour de l'axe change de signe lorsque la distance entre les bobines est égale à leur rayon (cas de Helmholz). Le calcul exact dans chaque cas se fait par ordinateur.Those skilled in the art can establish, by numerical calculation, the relationships between the dimensions of the coils and the fields and adapt the device to each particular case. Hz variation around of the axis changes sign when the distance between the coils is equal to their radius (case of Helmholz). The exact calculation in each case is done by computer.

La figure 5 représente schématiquement une vue en coupe d'un autre mode de réalisation d'un dispositif conforme à l'invention. Le moyen 30 consiste en une bobine plate 44 parcourue par un courant engendré par un générateur 46. Cette bobine 44 est placée dans le plan médian M par rapport aux plans (x, y) et (x′, y′). La distance séparant deux espaces diamétralement opposés (tels que A et D sur la figure 5) doit être inférieure au diamètre de la bobine 44. Mais le diamètre de celle-ci est tel que la bobine soit très proche de la trajectoire des électrons. La bobine 44 peut avoir un diamètre supérieur de 10 % à la distance entre A et D par exemple.Figure 5 schematically shows a sectional view of another embodiment of a device according to the invention. The means 30 consists of a flat coil 44 traversed by a current generated by a generator 46. This coil 44 is placed in the median plane M with respect to the planes (x, y) and (x ′, y ′). The distance separating two diametrically opposite spaces (such as A and D in FIG. 5) must be less than the diameter of the coil 44. But the diameter of the latter is such that the coil is very close to the path of the electrons. The coil 44 can have a diameter 10% greater than the distance between A and D for example.

Cette bobine 44 induit un champ magnétique de compensation au niveau du plan médian M. Elle permet la compensation de la dérive azimutale dans le cas où les électrons décrivent peu d'orbites tout au long de leur trajectoire.This coil 44 induces a magnetic field of compensation at the level of the median plane M. It allows the compensation of the azimuthal drift in the case where the electrons describe few orbits throughout their trajectory.

Selon la variante illustrée sur la figure 6, un résultat analogue peut être obtenu par une pièce ferromagnétique 48 placée dans le plan médian M par rapport aux plans (x, y) et (x′, y′), l'axe z étant un axe de symétrie pour cette pièce.According to the variant illustrated in FIG. 6, a similar result can be obtained by a ferromagnetic part 48 placed in the median plane M with respect to the planes (x, y) and (x ′, y ′), the axis z being a axis of symmetry for this part.

Cette pièce peut être un disque, un cylindre ou un tore par exemple. Le diamètre de cette pièce est inférieur à la distance entre deux espaces diamétralement opposés (A, D sur la figure 6).This part can be a disc, a cylinder or a torus for example. The diameter of this piece is less than the distance between two diametrically opposite spaces (A, D in Figure 6).

Bien entendu, on peut combiner les différents dispositifs décrits ci-dessus pour obtenir une compensation plus efficace de la dérive azimutale.Of course, the various devices described above can be combined to obtain more effective compensation for the azimuthal drift.

Ainsi, est représenté sur la figure 7, un dispositif qui combine les dispositifs des figures 4 et 5. Ce dispositif s'applique à tous les cas, que les électrons décrivent peu ou beaucoup d'orbites sur leur trajectoire. Il s'applique particulièrement bien aux cas intermédiaires.Thus, is shown in Figure 7, a device which combines the devices of Figures 4 and 5. This device applies to all cases, that the electrons describe few or many orbits on their trajectory. It applies particularly well to intermediate cases.

Dans la configuration de la figure 7, le moyen auxiliaire de correction 30 consiste donc en deux bobines 36, 38 reliées respectivement à des générateurs de courant 40, 42 et en une bobine 44 de plus faible diamètre relieé à un générateur de courant 46. Les deux bobines 36, 38 sont disposées chacune dans l'un des plans (x, y) et (x′, y′), la bobine 44 étant située dans le plan médian M par rapport à ces plans.In the configuration of FIG. 7, the auxiliary correction means 30 therefore consists of two coils 36, 38 connected respectively to current generators 40, 42 and to a coil 44 of smaller diameter connected to a current generator 46. two coils 36, 38 are each arranged in one of the planes (x, y) and (x ′, y ′), the coil 44 being located in the median plane M with respect to these planes.

Bien entendu, et comme il résulte déjà de ce qui précède, il va de soi que l'invention ne se limite nullement aux exemples de réalisation décrits ci-dessus. Elle en embrasse au contraire toutes les variantes. Comme on l'a représenté figure 8, on peut, par exemple, combiner les dispositifs décrits sur les figures 5 et 6, ou encore les dispositifs représentés sur les figures 4 et 6.Of course, and as already follows from the above, it goes without saying that the invention is in no way limited to the exemplary embodiments described above. On the contrary, it embraces all variants. As shown in FIG. 8, it is possible, for example, to combine the devices described in FIGS. 5 and 6, or else the devices represented in FIGS. 4 and 6.

Claims (5)

1. Dispositif correcteur de trajectoires pour tube électronique, ce tube comprenant un moyen principal (24) apte à engendrer un champ magnétique principal de révolution autour d'un axe (z) et des moyens pour créer au moins un faisceau d'électrons (10, 11, 12, 13, 14, 15) écarté de cet axe (z) et passant successivement à travers un premier trou (A, B, C, D, E, F) percé dans un premier disque (20), puis à travers un second trou (A′, B′, C′, D′, E′, F′) percé dans un second disque (22), ce dispositif étant caractérisé par le fait qu'il comprend au moins un moyen auxiliaire mince centré sur l'axe de révolution (z) et apte à créer un champ magnétique de correction ayant même axe de révolution que le champ principal, et présentant un gradient radial, ce champ auxiliaire corrigeant les effets de dérive azimutale du faisceau (10, 11, 12, 13, 14, 15) entre le premier (A, B, C, D, E, F) et le second trous (A′, B′, C′, D′, E′, F′), dérive due à la non uniformité du champ principal entre les deux trous.1. Trajectory correcting device for an electronic tube, this tube comprising a main means (24) capable of generating a main magnetic field of revolution about an axis (z) and means for creating at least one electron beam (10 , 11, 12, 13, 14, 15) spaced from this axis (z) and passing successively through a first hole (A, B, C, D, E, F) drilled in a first disc (20), then at through a second hole (A ′, B ′, C ′, D ′, E ′, F ′) drilled in a second disc (22), this device being characterized in that it comprises at least one thin auxiliary means centered on the axis of revolution (z) and able to create a magnetic correction field having the same axis of revolution as the main field, and having a radial gradient, this auxiliary field correcting the effects of azimuthal drift of the beam (10, 11, 12, 13, 14, 15) between the first (A, B, C, D, E, F) and the second hole (A ′, B ′, C ′, D ′, E ′, F ′), drift due to the non-uniformity of the main field between the two holes. 2. Dispositif selon la revendication 1, caractérisé par le fait que le moyen (30) auxiliaire de correction se compose d'une première et d'une seconde bobines plates (20, 22) parcourues par des courants et placées au voisinage des plans (x, y, x′, y′) des premier et second disques (20, 22).2. Device according to claim 1, characterized in that the auxiliary correction means (30) consists of first and second flat coils (20, 22) traversed by currents and placed in the vicinity of the planes ( x, y, x ′, y ′) of the first and second discs (20, 22). 3. Dispositif selon la revendication 1, caractérisé par le fait que le moyen auxiliaire de correction (30) se compose d'une seule bobine plate (46) parcourue par un courant et placée dans le plan médian (M) par rapport aux plans (x, y, x′, y′) des premier et second disques (20, 22).3. Device according to claim 1, characterized in that the auxiliary correction means (30) consists of a single flat coil (46) traversed by a current and placed in the median plane (M) relative to the planes ( x, y, x ′, y ′) of the first and second discs (20, 22). 4. Dispositif selon les revendications 2 et 3, caractérisé par le fait que le moyen auxiliaire de correction (30) se compose d'une première bobine plate (38) placée au voisinage du plan (x, y) du premier disque (20), d'une seconde bobine plate (36) placée au voisinage du plan (x′, y′) du second disque (22) et d'une troisième bobine (44) placée dans le plan médian (M), ces bobines (36, 38, 44) étant parcourues par des courants.4. Device according to claims 2 and 3, characterized in that the auxiliary correction means (30) consists of a first flat coil (38) placed in the vicinity of the plane (x, y) of the first disc (20) , a second flat coil (36) placed in the vicinity of the plane (x ′, y ′) of the second disc (22) and a third coil (44) placed in the median plane (M), these coils (36 , 38, 44) being traversed by currents. 5. Dispositif selon la revendication 1, caractérisé par le fait que le moyen auxiliaire de correction (30) se compose d'une pièce ferromagnétique (38) placée dans le plan médian (M) par rapport aux plans (x, y), (x′, y′) du premier et du second disques (20, 22), l'axe de révolution (z) étant axe de symétrie de cette pièce (48).5. Device according to claim 1, characterized in that the auxiliary correction means (30) consists of a ferromagnetic part (38) placed in the median plane (M) relative to the planes (x, y), ( x ′, y ′) of the first and second discs (20, 22), the axis of revolution (z) being the axis of symmetry of this part (48).
EP89402559A 1988-09-23 1989-09-19 Fly-path correction device in an electron tube Withdrawn EP0362021A1 (en)

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FR8812467A FR2637122A1 (en) 1988-09-23 1988-09-23 PATH CORRECTING DEVICE FOR ELECTRONIC TUBE
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