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EP0000672A1 - Meter or decimeter waves generator formed by a resonant structure coupled to a hollow electron beam. - Google Patents

Meter or decimeter waves generator formed by a resonant structure coupled to a hollow electron beam. Download PDF

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Publication number
EP0000672A1
EP0000672A1 EP78400028A EP78400028A EP0000672A1 EP 0000672 A1 EP0000672 A1 EP 0000672A1 EP 78400028 A EP78400028 A EP 78400028A EP 78400028 A EP78400028 A EP 78400028A EP 0000672 A1 EP0000672 A1 EP 0000672A1
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Prior art keywords
resonant structure
resonant
electron beam
diameter
generator according
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German (de)
French (fr)
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EP0000672B1 (en
Inventor
René Le Gardeur
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
    • H01J25/02—Tubes with electron stream modulated in velocity or density in a modulator zone and thereafter giving up energy in an inducing zone, the zones being associated with one or more resonators
    • H01J25/025—Tubes with electron stream modulated in velocity or density in a modulator zone and thereafter giving up energy in an inducing zone, the zones being associated with one or more resonators with an electron stream following a helical path
    • 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
    • H01J23/16—Circuit elements, having distributed capacitance and inductance, structurally associated with the tube and interacting with the discharge
    • H01J23/18—Resonators
    • H01J23/20—Cavity resonators; Adjustment or tuning thereof

Definitions

  • the subject of the present invention is a generator of metric or decimetric electromagnetic waves, constituted by a resonant structure coupled to a tubular beam of electrons in helical orbits.
  • This generator is based on an interaction between on the one hand a tubular electronic beam, to which a cyclotronic movement is printed using a static magnetic field, and on the other hand an electromagnetic field of azimuthal distribution established in a resonant structure. , at a frequency close to the cyclotron frequency of the electrons.
  • Such an interaction is already known per se, but only when the electron beam is coupled to the electromagnetic field of a resonant cylindrical or spherical cavity. It is described, for example, in an article by R. Le Gardeur published in the reports of the 5th International Congress on Tubes for Microwave, Paris, September 14-18, 1964, pages 522 to 526.
  • the resonant mode used in the interaction described in this article is of the TE 011 type (for electric transverse) in cylindrical geometry. It is identified by three indices m, n, p which characterize the distribution of the field respectively according to the polar angle ⁇ , the radius r, and the ordinate z counted along the axis.
  • the electric field which corresponds to it n ' has only a tangential component E ⁇ , the radial and axial components being zero and this tangential component is independent of ⁇ , it undergoes only an alternation along a radius and that an alternation along the axis .
  • This mode is called "azimuth" or in magnetic dipole.
  • the Bessel function is equivalent to so that the tangential component of the field is expressed by the approximate relation: which shows that for z fixed, the field believes as r in the vicinity of the axis.
  • these parameters satisfy the relationship: where D is the diameter of the cavity, L its length and ⁇ the wavelength.
  • Figure 1 shows the variation of D / X as a function of L / D taken as a variable. It appears that the diameter D is always of the order of several wavelengths and, in any case, greater than or 1.22 times the wavelength.
  • the cavity When the operating range of the electronic tube is in the range of centimeter waves, the cavity therefore has a diameter of the order of 5 to 10 cm, which does not pose any particular problem. But at 30 cm wavelength (i.e. 1000 MHz frequency), the diameter of the cavity is already at least 36 cm and at 3 m (150 MHz), the diameter takes a value of 360 cm which is prohibitive in most applications.
  • the length L naturally follows analogous variations. It therefore becomes excluded to use such cavities for the generation of decimetric or metric waves, so that the generators of the type described in the publication cited above are ill-suited to the production of metric or decimetric waves.
  • the object of the present invention is precisely a generator of this type, which does not have this drawback in that its dimensions are smaller than those of a generator which would use a cylindrical cavity for the same resonant frequency.
  • the structure further comprises a cylindrical outer shield.
  • each sector is preferably connected to the external shielding by supports of adjustable length.
  • the entire structure can be surrounded by a sealed envelope; but, in an advantageous variant, only the inner cylindrical part comprises such a sealed envelope. It must then have low dielectric losses at microwave frequencies.
  • Figure 1 already has. essentially been analyzed. It may be added, for comparison, that the overall diameter of a resonant structure according to the invention is of the order of the operating half-wavelength, so that, if a ratio is taken D / ⁇ of 1.22 for cylindrical cavities, '.e diameter reduction factor, when passing from cylindrical structures of the prior art to structures according to the invention, is of the order of 2.5 . This factor can be higher in certain cases for less energetic electron beams, as will be seen better later.
  • FIG. 2 The structure forming part of the generator of the invention is shown in FIG. 2. It comprises a plurality of circular cylindrical sectors 2 separated by capacitive openings 4. This structure is for example made of copper or brass.
  • the electric field lines 6 are represented in this figure for the fundamental azimuth mode. In the vicinity of the axis, the electric field is purely azimuth and includes only one component E ⁇ . In the capacitive openings, the field is normal to the walls. Between these extreme zones, the distribution is more complex. It can be calculated according to the classical method which consists in solving the Maxwell equations taking into account the angular periodicity of the structure. Such a calculation is outside the scope of this description, but we can refer to the classic works which deal with this kind of problem and in particular to the work already cited where the distribution of the field in the interaction space of a magnetron where the symmetry is of the same order.
  • the axial zone of the structure is of an inductive character and that the peripheral zone is of a capacitive character.
  • the structure radiates electromagnetic energy. If we want to completely suppress this radiation in order to obtain a maximum overvoltage, we can surround the structure with a shield 8, as illustrated in FIG. 3. In this case, the presence of this blin dage or these additional walls changes the resonant frequency of the structure.
  • FIG. 3 also illustrates a particular embodiment in which the sectors are held by supports 10 connected to the shielding and having a variable length.
  • these supports consist of a screw 12, accessible from the outside, which engages in a small column 14; but other systems may be suitable.
  • These supports 10 can be of conductive or insulating material.
  • the advantage of this arrangement is to allow the variation of the internal diameter of the resonant structure, and the modification of the width of the zone. capacitive, allowing the operator to adjust the resonant frequency of the structure.
  • the only way to vary the resonant frequency of a cylindrical cavity is practically to act on the position of a movable ceiling. But it is not possible to do so here, because the axis of the cavity must be left free to access. The possibility of varying the diameter of the resonant structure then takes on its full interest.
  • the structure of the invention constitutes the resonant circuit of an electronic tube, it is necessary that the space where the electrons and the field interact is maintained under high vacuum.
  • This space is the axial zone of the structure, where the field has a pure azimuthal distribution.
  • the structure comprises, in accordance with the representation of FIG. 4, a tube 16 made of impervious material having low dielectric losses at the frequencies of use. It may in particular be a tube made of ceramic material.
  • FIG. 5 schematically represents the essential elements of the VHF or UHF generator of the invention.
  • the generator of FIG. 5 comprises a resonant structure 20, crossed by a tubular beam of electrons 22, animated by a helical movement, an outer envelope 24 shielding, a coupling goat 26, oriented perpendicular to the high frequency magnetic field lines, and a coaxial line 28 connected to the members of use.
  • the dimensions of the resonant structure and, in particular, the internal diameter have largely determined by the diameter of the tubular electron beam.
  • the internal diameter of the structure must be, at a minimum, of the order of twice the diameter of the electron tube bundle.
  • the latter is a function of the acceleration potential of the electrons in the barrel which precedes the interaction zone. This potential is at most of the order of 40 kV, this yes gives the beam a diameter of the order of ⁇ / 8.
  • the diameter of the resonant structure is of the order of X / 4.
  • the assembly has an overall diameter of the order of ⁇ / 2. If we compare this value to that of cylindrical cavities, which is at least 1.22 ⁇ , we see that there is a ratio of at least 2.5 to the benefit of the structure of the invention, which is the result announced above.
  • the dimension ratio reaches 3.5. It can be further increased at low frequencies (VHF) when the shielding diameter is chosen to be less than twice the inside diameter of the structure.

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Abstract

Structure résonnante d'interaction (20) pour un générateur d'ondes métriques et décimétriques à faisceau tubulaire d'électrons en orbites hélicoïdales formée d'une pluralité de secteurs cylindriques circulaires (2), séparés par des ouvertures capacitives (4).Resonant interaction structure (20) for a VHF / UHF generator with a tubular beam of electrons in helical orbits formed by a plurality of circular cylindrical sectors (2), separated by capacitive openings (4).

Description

La présenta invention a pour objet un générateur d'ondes électromagnétiques métriques ou décimétriques, constitué par une structure résonnante couplée à un faisceau tubulaire d'électrons en orbites hélicoïdales.The subject of the present invention is a generator of metric or decimetric electromagnetic waves, constituted by a resonant structure coupled to a tubular beam of electrons in helical orbits.

Ce générateur est basé sur une interaction entre d'une part un faisceau électronique tubulaire, auquel est imprimé un mouvement cyclotronique à l'aide d'un champ magnétique statique, et d'autre part un champ électromagnétique de distribution azimutale établi dans une structure résonnante, à une fréquence proche de la fréquence cyclotronique des électrons. Une telle interaction est déjà connue en soi, mais seulement lorsque le faisceau d'électrons est couplé au champ électromagnétique d'une cavité résonnante cylindrique ou sphérique. Elle est décrite, par exemple, dans un article de R. Le Gardeur publié dans les comptes rendus du Sème Congrès International sur les Tubes pour Hyperfréquences, Paris, 14-18 septembre, 1964, pages 522 à 526.This generator is based on an interaction between on the one hand a tubular electronic beam, to which a cyclotronic movement is printed using a static magnetic field, and on the other hand an electromagnetic field of azimuthal distribution established in a resonant structure. , at a frequency close to the cyclotron frequency of the electrons. Such an interaction is already known per se, but only when the electron beam is coupled to the electromagnetic field of a resonant cylindrical or spherical cavity. It is described, for example, in an article by R. Le Gardeur published in the reports of the 5th International Congress on Tubes for Microwave, Paris, September 14-18, 1964, pages 522 to 526.

Le mode résonnant utilisé dans l'interaction décrite dans cet article est du type TE011 (pour transverse électrique) en géométrie cylindrique. Il est identifié par trois indices m, n, p qui caractérisent la distribution du champ respectivement en fonction de l'angle polaire φ, du rayon r, et de l'ordonnée z comptée suivant l'axe.Le champ électrique qui lui correspond n'a qu'une composante tangentielle Eφ, les composantes radiales et axiales étant nulles et cette composante tangentielle est indépendante de φ, elle ne subit qu'une alternance le long d'un rayon et qu'une alternance le long de l'axe. Ce mode est dit "azimutal" ou encore en dipole magnétique. The resonant mode used in the interaction described in this article is of the TE 011 type (for electric transverse) in cylindrical geometry. It is identified by three indices m, n, p which characterize the distribution of the field respectively according to the polar angle φ, the radius r, and the ordinate z counted along the axis. The electric field which corresponds to it n 'has only a tangential component E φ , the radial and axial components being zero and this tangential component is independent of φ, it undergoes only an alternation along a radius and that an alternation along the axis . This mode is called "azimuth" or in magnetic dipole.

Cette composante Eφ du champ électrique est donnée quantitativement par une expression que l'on trouvera dans tous les ouvrages spécialisés portant sur la théorie des volumes résonnant aux hyperfréquences, (et notamment dans l'ouvrage "Microwave Electronics" de J.C. SLATER) :

Figure imgb0001
expression dans laquelle :

  • φ, r et z sont les coordonnées cylindriques,
  • R est le rayon de la cavité et L sa longueur,
  • A est une constante,
  • J1 est la première fonction de Bessel et x'01 sa première racine,
  • w est la pulsation de résonance du mode.
This component E φ of the electric field is given quantitatively by an expression which one will find in all the specialized works relating to the theory of volumes resonating with microwaves, (and in particular in the work "Microwave Electronics" of JC SLATER):
Figure imgb0001
 expression in which:
  • φ, r and z are the cylindrical coordinates,
  • R is the radius of the cavity and L its length,
  • A is a constant,
  • J1 is the first Bessel function and x '01 its first root,
  • w is the resonance pulse of the mode.

Près de l'axe, où- r est faible devant R, la fonction de Bessel

Figure imgb0002
est équivalente à
Figure imgb0003
 de sorte que la composante tangentielle du champ s'exprime par la relation approchée :
Figure imgb0004
qui montre que pour z fixé, le champ croit comme r au voisinage de l'axe.Near the axis, where- r is weak in front of R, the Bessel function
Figure imgb0002
 is equivalent to
Figure imgb0003
 so that the tangential component of the field is expressed by the approximate relation:
Figure imgb0004
 which shows that for z fixed, the field believes as r in the vicinity of the axis.

La fréquence de résonance d'une cavité ou, ce qui revient au même, la longueur de l'onde associée, dépend naturellement des dimensions de la cavité. Pour le mode TE011, ces paramètres satisfont à la relation :

Figure imgb0005
où D est le diamètre de la cavité, L sa longueur et λ la longueur d'onde.The resonant frequency of a cavity or, which amounts to the same thing, the length of the associated wave, naturally depends on the dimensions of the cavity. For TE 011 mode, these parameters satisfy the relationship:
Figure imgb0005
 where D is the diameter of the cavity, L its length and λ the wavelength.

La figure 1 représente la variation de D/X en fonction de L/D pris comme variable. Il apparaît que le diamètre D est toujours de l'ordre de plusieurs longueurs d'onde et, de toute manière, supérieur à

Figure imgb0006
soit 1,22 fois la longueur d'onde.Figure 1 shows the variation of D / X as a function of L / D taken as a variable. It appears that the diameter D is always of the order of several wavelengths and, in any case, greater than
Figure imgb0006
 or 1.22 times the wavelength.

Lorsque la plage de fonctionnement du tube électronique se situe dans le domaine des ondes centimétriques, la cavité présente donc un diamètre de l'ordre de 5 à 10 cm, ce qui ne pose pas de problème particulier. Mais à 30 cm de longueur d'onde (soit 1000 MHz de fréquence), le diamètre de la cavité est déjà d'au moins 36 cm et à 3 m (150 MHz), le diamètre prend une valeur de 360 cm qui est prohibitive dans la plupart des applications.When the operating range of the electronic tube is in the range of centimeter waves, the cavity therefore has a diameter of the order of 5 to 10 cm, which does not pose any particular problem. But at 30 cm wavelength (i.e. 1000 MHz frequency), the diameter of the cavity is already at least 36 cm and at 3 m (150 MHz), the diameter takes a value of 360 cm which is prohibitive in most applications.

La longueur L suit naturellement des variations analogues. Il devient donc exclu d'employer de telles cavités pour la génération d'ondes décimêtriques ou métriques, de sorte que sles générateurs du type décrit dans la publication précédemment citée sont mal adaptés à la production d'ondes métriques ou décimétriques.The length L naturally follows analogous variations. It therefore becomes excluded to use such cavities for the generation of decimetric or metric waves, so that the generators of the type described in the publication cited above are ill-suited to the production of metric or decimetric waves.

La présente invention a justement pour objet un générateur de ce type, qui ne présente pas cet inconvénient en ce sens que ses dimensions sont inférieures à cellesd'un générateur qui utiliserait une cavité cylindrique pour une même fréquence de résonance.The object of the present invention is precisely a generator of this type, which does not have this drawback in that its dimensions are smaller than those of a generator which would use a cylindrical cavity for the same resonant frequency.

Ce résultat est obtenu, selon l'invention, en utilisant une structure qui comprend une pluralité de secteurs cylindriques circulaires, séparés par des ouvertures capacitives.This result is obtained, according to the invention, by using a structure which comprises a plurality of circular cylindrical sectors, separated by capacitive openings.

De préférence, pour éviter le rayonnement vers l'extérieur et améliorer la surtension, la structure comprend en outre un blindage extérieur cylindrique.Preferably, to avoid radiation to the outside and improve the overvoltage, the structure further comprises a cylindrical outer shield.

En plus de l'avantage exposé plus haut, relatif à la réduction des dimensions, l'invention offre celui de permettre un réglage de la fréquence de résonance de la structure par action sur le diamètre, ce qui n'était pas le cas dans l'art antérieur. Pour cela, chaque secteur est de préférence relié au blindage extérieur par des supports de longueur réglable.In addition to the advantage explained above, relating to the reduction in dimensions, the invention offers that of allowing adjustment of the resonant frequency of the structure by action on the diameter, which was not the case in prior art. For this, each sector is preferably connected to the external shielding by supports of adjustable length.

Pour pouvoir maintenir un vide poussé dans l'espace d'interaction, l'ensemble de la structure peut être entouré d'une enveloppe étanche ; mais, dans une variante avantageuse, seule la partie cylindrique intérieure comprend une telle enveloppe étanche. Celle-ci doit alors présenter de faibles pertes diélectriques aux hyperfréquences.To maintain a high vacuum in the interaction space, the entire structure can be surrounded by a sealed envelope; but, in an advantageous variant, only the inner cylindrical part comprises such a sealed envelope. It must then have low dielectric losses at microwave frequencies.

De toute façon, les caractéristiques et avantages de l'invention apparaîtront mieux après la description qui suit, d'exemples de réalisation donnés à titre explicatif et nullement limitatif, en référence aux dessins annexés sur lesquels :

  • - la figure 1 représente la courbe illustrant les variations de dimensions d'une cavité cylindrique en fonction de la longueur d'onde de résonance ;
  • - la figure 2 représente une section droite de la structure résonnante utilisée dans le générateur de l'invention ;
  • - la figure 3 représente un mode particulier de réali- sation d'une structure à fréquence de résonance réglable ;
  • - la.figure 4 représente un mode particulier de réa- lisation d'une structure résonnante étanche ;
  • - la figure 5 représente schématiquement l'ensemble du générateur de l'invention.
In any case, the characteristics and advantages of the invention will appear better after the description which follows, of exemplary embodiments given by way of explanation and in no way limiting, with reference to the appended drawings in which:
  • - Figure 1 shows the curve illustrating the variations in dimensions of a cylindrical cavity as a function of the resonance wavelength;
  • - Figure 2 shows a cross section of the resonant structure used in the generator of the invention;
  • - Figure 3 shows a particular embodiment of a structure with adjustable resonant frequency;
  • - la.figure 4 represents a particular embodiment of a sealed resonant structure;
  • - Figure 5 shows schematically the entire generator of the invention.

La figure 1 a déjà. été analysée pour l'essentiel. Il peut être ajouté, à titre comparatif, que le diamètre hors tout d'une structure résonnante selon l'invention est de l'ordre de la demi-longueur d'onde de fonctionnement, de sorte que, si l'on prend un rapport D/λ de 1,22 pour les cavités cylindriques, '.e facteur de réduction de diamètre, lorsqu'on passe des structures cylindriques de l'art antérieur aux structures conformes à l'invention, est de l'ordre de 2,5. Ce facteur peut être plus élevé dans certains cas pour des faisceaux électroniques moins énergétiques, comme on le verra mieux par la suite.Figure 1 already has. essentially been analyzed. It may be added, for comparison, that the overall diameter of a resonant structure according to the invention is of the order of the operating half-wavelength, so that, if a ratio is taken D / λ of 1.22 for cylindrical cavities, '.e diameter reduction factor, when passing from cylindrical structures of the prior art to structures according to the invention, is of the order of 2.5 . This factor can be higher in certain cases for less energetic electron beams, as will be seen better later.

La structure faisant partie du générateur de l'invention est représentée sur la figure 2. Elle comprend une pluralité de secteurs cylindriques circulaires 2 séparés par des ouvertures capacitives 4. Cette structure est par exemple en cuivre ou en laiton. Les lignes de champ électrique 6.sont représentées sur cette figure pour le mode azimutal fondamental. Au voisinage de l'axe, le champ électrique est purement azimutal et ne comprend qu'une composante Eφ. Dans les ouvertures capacitives, le champ est normal aux parois. Entre ces zones extrêmes, la distribution est plus complexe. Elle peut être calculée selon la méthode classique qui consiste à résoudre les équations de Maxwell en tenant compte de la périodicité angulaire de la structure. Un tel calcul sort du cadre de la présente description, mais on pourrs se reporter aux ouvrages classiques qui traitent ce genre de problème et notamment à l'ouvrage déjà cité où est étudiée la répartition du champ dans l'espace d'interaction d'un magnétron où la symétrie est du même ordre.The structure forming part of the generator of the invention is shown in FIG. 2. It comprises a plurality of circular cylindrical sectors 2 separated by capacitive openings 4. This structure is for example made of copper or brass. The electric field lines 6 are represented in this figure for the fundamental azimuth mode. In the vicinity of the axis, the electric field is purely azimuth and includes only one component E φ . In the capacitive openings, the field is normal to the walls. Between these extreme zones, the distribution is more complex. It can be calculated according to the classical method which consists in solving the Maxwell equations taking into account the angular periodicity of the structure. Such a calculation is outside the scope of this description, but we can refer to the classic works which deal with this kind of problem and in particular to the work already cited where the distribution of the field in the interaction space of a magnetron where the symmetry is of the same order.

On peut dire ici, pour simplifier, que la zone axiale de la structure est de caractère inductif et que la zone périphérique est de caractère capacitif. L'adjonction de cette dernière, par rapport aux cavités purement cylindriques, entraîne une diminution de la fréquence de résonance à dimensions égales ; réciproquement, le diamètre intérieur de la structure de la figure 2 est inférieur au diamètre d'une cavité cylindrique de même fréquence de résonance pour le même mode.We can say here, for simplicity, that the axial zone of the structure is of an inductive character and that the peripheral zone is of a capacitive character. The addition of the latter, relative to the purely cylindrical cavities, results in a reduction in the resonance frequency with equal dimensions; conversely, the internal diameter of the structure of FIG. 2 is less than the diameter of a cylindrical cavity with the same resonant frequency for the same mode.

Telle qu'elle est représentée sur la figure 2, la structure rayonne de l'énergie électromagnétique. Si l'on veut sup- primer totalement ce rayonnement afin d'obtenir une surtension maximale, on peut entourer la structure d'un blindage 8, comme 'illustré sur la figure 3. Dans ce cas, la présence de ce blindage ou de ces parois supplémentaires modifie la fréquence de résonance de la structure.As shown in Figure 2, the structure radiates electromagnetic energy. If we want to completely suppress this radiation in order to obtain a maximum overvoltage, we can surround the structure with a shield 8, as illustrated in FIG. 3. In this case, the presence of this blin dage or these additional walls changes the resonant frequency of the structure.

La figure 3 illustre en outre un mode de réalisation particulier dans lequel les secteurs sont tenus par des supports 10 reliés au blindage et présentant une longueur variable. Sur la figure et à titre explicatif, ces supports consistent en une vis 12, accessible de l'extérieur, qui s'engage dans une colonnette 14 ; mais d'autres systèmes pourraient convenir. Ces supports 10 peuvent être en matériau conducteur ou isolant.FIG. 3 also illustrates a particular embodiment in which the sectors are held by supports 10 connected to the shielding and having a variable length. In the figure and by way of explanation, these supports consist of a screw 12, accessible from the outside, which engages in a small column 14; but other systems may be suitable. These supports 10 can be of conductive or insulating material.

L'intérêt de cette disposition est de permettre la variation du diamètre intérieur de la structure résonnante, et la modification de la largeur de la zone. capacitive, ce qui permet à l'opérateur de régler la fréquence de résonance de la structure. La seule manière de faire varier la fréquence de résonnan- ce d'une cavité cylindrique consiste pratiquement à agir sur la position d'un plafond mobile. Mais il n'est pas possible de procéder de la sorte ici, car l'axe de la cavité doit être laissé libre d'accès. La possibilité de faire varier le diamètre de la structure résonnante prend alors tout son intérêt.The advantage of this arrangement is to allow the variation of the internal diameter of the resonant structure, and the modification of the width of the zone. capacitive, allowing the operator to adjust the resonant frequency of the structure. The only way to vary the resonant frequency of a cylindrical cavity is practically to act on the position of a movable ceiling. But it is not possible to do so here, because the axis of the cavity must be left free to access. The possibility of varying the diameter of the resonant structure then takes on its full interest.

Puisque la structure de l'invention constitue le circuit résonnant d'un tube électronique, il est nécessaire que l'espace où interagissent les électrons et le champ soit maintenu sous vide poussé. Cet espace est la zone axiale de la structure, là où le champ présente une distribution azimutale pure. A cette fin, la structure comprend, conformément à la représentation de la figure 4, un tube 16 en matériau étanche présentant de faibles pertes diélectriques aux fréquences d'utilisation. Il peut s'agir notamment d'un tube en matériau céramique.Since the structure of the invention constitutes the resonant circuit of an electronic tube, it is necessary that the space where the electrons and the field interact is maintained under high vacuum. This space is the axial zone of the structure, where the field has a pure azimuthal distribution. To this end, the structure comprises, in accordance with the representation of FIG. 4, a tube 16 made of impervious material having low dielectric losses at the frequencies of use. It may in particular be a tube made of ceramic material.

Dans certains cas, si l'on veut encore abaisser la fréquence de résonance de la structure sans augmenter ses dimensions hors tout, il est possible d'adjoindre aux ouvertures des éléments capacitifs localisés, comme représenté sur la figure 4 où ces éléments portent la référence 18.In some cases, if we still want to lower the resonant frequency of the structure without increasing its overall dimensions, it is possible to add to the openings localized capacitive elements, as shown in Figure 4 where these elements are marked 1 8.

La figure 5 représente schématiquement les éléments essentiels du générateur d'ondes métriques ou décimétriques de l'invention.FIG. 5 schematically represents the essential elements of the VHF or UHF generator of the invention.

Le générateur de la figure 5 comprend une structure résonnante 20, traversée par un faisceau tubulaire d'électrons 22, animés d'un mouvement hélicoidal, une enveloppe extérieure 24 de blindage, une bouc le de couplage 26, orientée perpendiculairement aux lignes de champ magnétique haute fréquence, et une ligne coaxiale 28 reliée aux organes d'utilisation.The generator of FIG. 5 comprises a resonant structure 20, crossed by a tubular beam of electrons 22, animated by a helical movement, an outer envelope 24 shielding, a coupling goat 26, oriented perpendicular to the high frequency magnetic field lines, and a coaxial line 28 connected to the members of use.

Dans un générateur de ce genre, les dimensions de la structure résonnante et, en particulier, le diamètre intérieur, ont déterminées en grande partie par le diamètre du faisceau électronique tubulaire. En effet, pour permettre au faisceau des mouvement radiaux lors de son interaction avec le champ électromagnétique, le diamètre intérieur de la structure doit être, au minimum, de l'ordre de deux fois le diamètre du faisceau tubulaire électronique. Or, ce dernier est fonction du potentiel d'accélération des électrons dans le canon qui précède la zone d'interaction. Ce potentiel est au maximum de l'ordre de 40 kV, ce oui donne au faisceau un diamètre de l'ordre de λ/8. Dans ce cas, le diamètre de la structure résonnante est de l'ordre de X/4. Comme le blindage présente un diamètre de l'ordre du double de celui de la structure résonnante proprement dite, l'ensemble présente un diamètre hors tout de l'ordre de λ/2. Si l'on compare cette valeur à celle des cavités cylindriques, qui est au minimum de 1,22 λ, on constate qu'il existe un rapport d'au moins 2,5 au bénéfice de la structure de l'invention, ce qui est le résultat annoncé plus haut.In a generator of this kind, the dimensions of the resonant structure and, in particular, the internal diameter, have largely determined by the diameter of the tubular electron beam. In fact, to allow the beam to move radially during its interaction with the electromagnetic field, the internal diameter of the structure must be, at a minimum, of the order of twice the diameter of the electron tube bundle. However, the latter is a function of the acceleration potential of the electrons in the barrel which precedes the interaction zone. This potential is at most of the order of 40 kV, this yes gives the beam a diameter of the order of λ / 8. In this case, the diameter of the resonant structure is of the order of X / 4. As the shielding has a diameter of the order of twice that of the resonant structure proper, the assembly has an overall diameter of the order of λ / 2. If we compare this value to that of cylindrical cavities, which is at least 1.22 λ, we see that there is a ratio of at least 2.5 to the benefit of the structure of the invention, which is the result announced above.

Lorsque le potentiel d'accélération tombe de 40 à 25 kV, le rapport des dimensions atteint 3,5. Il peut encore être augmenté aux fréquences basses (ondes métriques) lorsque le diamètre du blindage est choisi inférieur au double du diamètre intérieur de la structure.When the acceleration potential drops from 40 to 25 kV, the dimension ratio reaches 3.5. It can be further increased at low frequencies (VHF) when the shielding diameter is chosen to be less than twice the inside diameter of the structure.

Il résulte de ces considérations que l'encombrement d'un générateur du type décrit est réduit pour une même longueur d'onde d'émission, si l'on utilise la structure de l'invention ou, inversement, que la longueur d'onde d'émission peut être abaissée pour un même encombrement de la structure.It follows from these considerations that the size of a generator of the type described is reduced for the same emission wavelength, if the structure of the invention is used or, conversely, that the wavelength emission can be lowered for the same size of the structure.

Claims (5)

1. Générateur d'ondes métriques ou décimétriques basé sur une interaction de type cyclotronique entre un faisceau tubulaire d'électrons et un champ azimutal établi dans une structure résonnante, caractérise en ce que ladite structure résonnante comprend une pluralité de secteurs cylindriques circulaires, séparés par des ouvertures capacitives.1. Metric or decimetric wave generator based on a cyclotronic type interaction between a tubular electron beam and an azimuth field established in a resonant structure, characterized in that said resonant structure comprises a plurality of circular cylindrical sectors, separated by capacitive openings. 2. Générateur selon la revendication 1, caractérisé en ce que la structure résonnante comprend en outre un blindage extérieur cylindrique.2. Generator according to claim 1, characterized in that the resonant structure further comprises a cylindrical outer shield. 3. Générateur selon la revendication 2, caractérisé en ce que chaque secteur de la structure résonnante est relié au blindage extérieur par des supports de longueur réglable.3. Generator according to claim 2, characterized in that each sector of the resonant structure is connected to the external shielding by supports of adjustable length. 4. Générateur selon l'une quelconque des revendications 1 à 3, caractérisé en ce qu'un cylindre étanche en matériau diélectrique aux hyperfréquences est disposé à l'intérieur des secteurs de la structure résonnante.4. Generator according to any one of claims 1 to 3, characterized in that a sealed cylinder of microwave dielectric material is arranged inside the sectors of the resonant structure. 5. Générateur selon l'une quelconque des revendications 2 à 4, caractérisé en ce que la structure résonnante comprend une boucle de couplage dont l'une des extrémités est reliée à la paroi du blindage.5. Generator according to any one of claims 2 to 4, characterized in that the resonant structure comprises a coupling loop, one of the ends of which is connected to the wall of the shield.
EP78400028A 1977-06-27 1978-06-21 Meter or decimeter waves generator formed by a resonant structure coupled to a hollow electron beam. Expired EP0000672B1 (en)

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Application Number Priority Date Filing Date Title
FR7719619 1977-06-27
FR7719619A FR2396407A1 (en) 1977-06-27 1977-06-27 METRIC AND DECIMETRIC WAVE GENERATOR

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EP0000672A1 true EP0000672A1 (en) 1979-02-07
EP0000672B1 EP0000672B1 (en) 1981-09-09

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EP0372975A3 (en) * 1988-12-09 1991-04-24 Varian Associates, Inc. Couplers for extracting rf power from a gyrotron cavity directly into fundamental mode waveguide

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Also Published As

Publication number Publication date
DE2861052D1 (en) 1981-11-26
FR2396407B1 (en) 1980-07-25
US4225806A (en) 1980-09-30
FR2396407A1 (en) 1979-01-26
EP0000672B1 (en) 1981-09-09

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