EP0349386B1 - X-ray tube with a variable focal spot adjusting itself to the charge - Google Patents

X-ray tube with a variable focal spot adjusting itself to the charge Download PDF

Info

Publication number
EP0349386B1
EP0349386B1 EP89401760A EP89401760A EP0349386B1 EP 0349386 B1 EP0349386 B1 EP 0349386B1 EP 89401760 A EP89401760 A EP 89401760A EP 89401760 A EP89401760 A EP 89401760A EP 0349386 B1 EP0349386 B1 EP 0349386B1
Authority
EP
European Patent Office
Prior art keywords
cathode
anode
plane
ray tube
emitting part
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP89401760A
Other languages
German (de)
French (fr)
Other versions
EP0349386A1 (en
Inventor
Sixte De Fraguier
Catherine Thomas
François Caire
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.)
General Electric CGR SA
Original Assignee
General Electric CGR SA
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by General Electric CGR SA filed Critical General Electric CGR SA
Publication of EP0349386A1 publication Critical patent/EP0349386A1/en
Application granted granted Critical
Publication of EP0349386B1 publication Critical patent/EP0349386B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/14—Arrangements for concentrating, focusing, or directing the cathode ray
    • H01J35/147—Spot size control
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H01J35/06—Cathodes
    • H01J35/066—Details of electron optical components, e.g. cathode cups

Definitions

  • the present invention relates to an X-ray tube in particular with a variable focus self-adapted to the load, usable in the medical field.
  • the main characteristics of these tubes relate to the resistance to drift of their emission characteristics as a function of their temperature as well as the homogeneity of the illumination X produced by all the points of their focus.
  • the invention aims to improve such tubes by avoiding their possible destruction under the effect of excessive heating of their anode.
  • X-rays are produced by electron bombardment, in a vacuum enclosure, of a target made from a material with a high atomic number.
  • the electrons necessary for the bombardment of this target are released by thermoelectronic effect, generally in a helical filament of tungsten, from a cathode placed precisely within a room of concentration.
  • the concentration piece plays a focusing role at the same time as a Wehnelt role.
  • the target is formed by the anode of the tube.
  • the initial velocities of the electrons at the level of the emitter are very dispersed. Their trajectory therefore has a disordered structure and the focusing system is responsible for correcting them.
  • the focusing system is generally not efficient enough.
  • the object of the present invention is to remedy this drawback by proposing a flat emitting device, moreover offering mechanical rigidity making it possible to overcome the problems of corrugated sheet mentioned above.
  • the solution of the problems of variation of the thermal density along the hearth, or variation of the dimension of this hearth according to the load of the tube, can then be brought by the installation of this planar cathode in a so-called focusing part to walk. It was discovered that there was in this case a self-regulation of the characteristics of this home. Thus, for a particular geometry of the walking focusing piece, it is possible to obtain a thermal density of the focal point which is always constant.
  • the advantage of this solution is that it applies over a wide range of high voltage, between the anode and the cathode, so that the same tube serve several applications.
  • the advantage of having a controlled thermal density and therefore a hearth of variable size with the load allows the user to have with the same tube a large number of hearths of different dimensions. Indeed, the photographs taken with a fine focus can be made at a lower speed, and when the user works with a larger focus, he needs more power.
  • the invention therefore makes available to the user a focus tube of continuously variable and adjustable size and with constant thermal flux on the target. This simply ensures control over the use.
  • US Pat. No. 4,344,011 describes an X-ray tube comprising a flat cathode disposed at the base of a step focusing device.
  • Patent application JP-A-53 030 292 describes an X-ray tube comprising a beam-shaped cathode, cathode disposed at the base of a walking focusing device.
  • the invention therefore relates to an X-ray tube with automatic limitation of the maximum value of the heat flux on the anode comprising in a vacuum enclosure a cathode which emits an electron beam and an anode which emits X-ray, said anode facing the cathode so as to receive said electron beam and said cathode being arranged at the base of a focusing device comprising at least one step, characterized in that said focusing device is arranged so that the point of Electron convergence is located behind the plane of the anode and in that the cathode is in the form of a hollow beam and has a plane emissive part parallel to the longitudinal axis of this hollow beam, this part facing the anode.
  • FIG. 1 shows schematically a tube radiogenic according to the invention.
  • This X-ray tube comprises, in an empty enclosure, not shown, a cathode 1 located opposite an anode 2.
  • the anode receives electronic radiation 3 on its hearth 4 and re-emits X-radiation 5 in particular in the direction of a usage window 6.
  • the usage window is part of the tube casing.
  • the cathode has the particularity of opposing a planar face 7 opposite the anode 2. It also has the particularity of being inserted into a focusing optic 8 known as on.
  • the purpose of this walking focusing optic is to create a distribution of the electric field between the anode and the cathode such that the radiation 3 of the electrons is of the convergent type.
  • convergent radiation There are two types of convergent radiation.
  • a first type represented in FIG. 1, the point of convergence of the electrons is located behind the plane of the anode: it is virtual. In this case, the radiation is said to be direct.
  • a second type of radiation called cross, the point of convergence of the electrons is located in the intermediate position between the cathode 7 and the anode 2: it is real.
  • the focusing device 8 can also be a single step, it has been found here more advantageous to make it double step.
  • the focusing part 8 has a prismatic shape, FIG. 1 of which represents the right section plane.
  • the part 8 comprises the two steps, respectively 9 and 10 distributed symmetrically in 9 ′ and 10 ′ on either side of the cathode 1.
  • Each step has a step 91 or 101 and a riser 92 or 102. (respectively 91 ′, 92, ′ 101 ′, 102 ′).
  • the plane 7 of the cathode 1 is distant from the anode 4 by a distance of approximately 7.5 mm.
  • Tops 91 and 91 ′ of steps 9 and 9 ′ are distant from the anode by about 7mm.
  • the tops 101 and 101 ′ are spaced about 6 mm from the plane of the anode 2.
  • the width of the cathode 1, measured in the plane of cross section of the focal prismatic part 8, is 2 mm.
  • the width of a housing 11 where this cathode is placed inside the focal piece 8 is 2.2 mm.
  • the distance between risers 92 and 92 ′ is 4 mm while the distance between risers 101 and 102 ′ is 5 mm.
  • the device has a symmetrical appearance with respect to a plane passing through the axis 12 of the radiation, perpendicular to the plane of the figure.
  • the assembly can be circular, the axis 12 serving as an axis of revolution for the cathode as well as for the focusing part.
  • the anode 4 is a rotating type anode and even that it has an inclined face on the axis 12. In this case the distances indicated are rather the distances measured on this axis 12 between the plane 7 of the cathode and the trace of the axis 12 on the anode 2.
  • the thermal flux FT is then substantially constant, for a given high operating voltage, as a function of the load D of the tube.
  • the diagram of FIG. 2 presents three curves respectively 13 to 15 parameterized by high voltages respectively of 20 kV, 40 kV or 50 kV displaying, in a range of load of use located between 150 mA and 500 mA, a substantially flat appearance.
  • the heat flux is expressed in kW per mm2. In the example shown, it is always less than 50 kW per mm2, even for the highest operating high voltage.
  • the significance of the flat appearance of this heat flux as a function of the load simply means that the dimension 16 of the thermal focus evolves linearly with the load.
  • the cathode 1 has the appearance of a beam shown in perspective in FIG. 3.
  • This beam is prismatic, hollow, and has substantially the appearance of a house.
  • the house is presented here as if it were lying on one of its walls.
  • the base of the house constitutes the emissive face 7 of the cathode, the walls of the house such as wall 23 have windows such as 24.
  • the advantage of manufacturing a hollow beam lies in the reduction of the quantity of metal to be heated.
  • the beam structure gives this cathode mechanical rigidity avoiding corrugated sheet phenomena. As the quantity of metal to be heated is lower, the thermal inertia of the cathode is less, the starting of the tube can be faster. Furthermore, the consumption of the cathode heating supply can be reduced, which is an advantage when we know the insulation problems which the cathode heating circuits must face.
  • a heating filament 25 for example of the same type as a heating filament used in the state of technology as a transmitter.
  • This filament 25 is itself negatively polarized (several thousand volts) relative to the cathode 1.
  • the beam cathode is made of tungsten.
  • the ceiling 26 and the interior of the walls thereof are provided with a mattress 27 of thermally insulating fibers. This concentrates the heating on the emissive part of the cathode.
  • the fibers are ceramic fibers which allow good insulation of the lateral internal walls of the house. The electrons emitted by the heating filament only bombard the rear of the cathode 7 according to a drawing represented by the electric field curves 28. This bombardment is limited to the front wall.
  • this front wall has a concave profile.
  • this concave profile is even so concave that the wings 29 and 30 respectively of this cathode have internal faces, respectively 31 and 32, closer to the filament 25 than is the internal face of the cathode 7 to 1. 'place 33 of its middle. In this way the wings which are both thicker, and which would be harder to heat, are however more heated so that the top of the beam is brought at all points to a substantially constant temperature. In this way, the expected electron radiation is emitted at a substantially constant rate.
  • the beam according to the invention now has the advantage that its emissive face 7 no longer distorts under the effects of heating, it nevertheless undergoes expansions which should be guided without upsetting them.
  • the cathode is fixed by a single tab 34 constituting in a way the chimney of the house.
  • the method of attachment is preferably obtained by blocking this tab 34 between two screws 35 and 36 which come to grip it between them respectively.
  • This mounting at a fixing point has the advantage of leaving the cathode all the desired degrees of freedom. It is in particular preferable to a method of fixing with two points which would have the disadvantage that the reactions between these two points would inevitably have repercussions on the flatness of the emissive surface 7.
  • the walls of this cathode are held in the focal piece 8 by ceramic pins such as 37 and 38 which come to bear on either side on it. This avoids any phenomenon of bending or vibration harmful to an exact positioning of the transmitter in the focusing part.
  • the pins allow the transmitter to thermally expand along its greatest length while keeping it laterally in its reference position.
  • the electrical supply of the cathode can be obtained by passing the high voltage through the screws 35 or 36.
  • the focal piece can optionally be electrically decoupled from the cathode.

Landscapes

  • X-Ray Techniques (AREA)
  • Secondary Cells (AREA)

Description

La présente invention a pour objet un tube à rayons X notamment à foyer variable auto-adapté à la charge, utilisable dans le domaine médical. Les principales caractéristiques de ces tubes concernent les résistances à la dérive de leurs caractéristiques d'émission en fonction de leur température ainsi que l'homogénéité de l'illumination X produite par tous les points de leur foyer. L'invention vise à perfectionner de tels tubes en évitant leur éventuelle destruction sous l'effet d'un échauffement trop important de leur anode.The present invention relates to an X-ray tube in particular with a variable focus self-adapted to the load, usable in the medical field. The main characteristics of these tubes relate to the resistance to drift of their emission characteristics as a function of their temperature as well as the homogeneity of the illumination X produced by all the points of their focus. The invention aims to improve such tubes by avoiding their possible destruction under the effect of excessive heating of their anode.

D'une façon générale des rayons X sont produits par le bombardement électronique, dans une enceinte à vide, d'une cible élaborée dans un matériau à haut numéro atomique. Les électrons nécessaires au bombardement de cette cible sont libérés par effet thermo-électronique, généralement dans un filament hélicoïdal de tungstène, d'une cathode placée avec précision au sein d'une pièce de concentration. La pièce de concentration joue un rôle focalisateur en même temps qu'un rôle de Wehnelt. La cible est constituée par l'anode du tube. Dans ce type de configuration très classique, les vitesses initiales des électrons au niveau de l'émetteur sont très dispersées. Leur trajectoire présente donc une structure désordonnée et le système de focalisation est chargé de les rectifier. Le système de focalisation n'est généralement pas suffisamment performant. En conséquence, au lieu de l'impact de ces électrons de bombardement sur la cible, on obtient un enchevêtrement assez compliqué des trajectoires. Ceci confère au foyer thermique des rayons X un profil énergétique assez peu compatible avec une bonne qualité d'image. Dans des développements récents, par exemple dans ceux décrits dans la demande de brevet européen EP-A-164 665, il est fait référence à une cathode qui n'est plus constituée par un filament mais qui est constituée par une portion d'un ruban présentant, à l'émission des électrons, une surface plane en face de l'anode. L'intérêt d'utiliser un émetteur d'électrons plan a déjà été présenté antérieurement à cette demande. Il consiste à maintenir une certaine cohésion des charges électroniques au cours de leur trajectoire vers la cible. En effet, l'expérience a montré qu'on obtient dans ce cas une répartition de potentiel électrostatique favorable à une meilleure focalisation des charges électriques. Le foyer X ainsi obtenu présente alors un profil énergétique pratiquement homogène, ce qui est bénéfique à la qualité de l'image. La littérature scientifique relate certaines expérimentations basées sur ce principe général. On y fait toujours usage d'émetteur élaboré sous la forme de ruban de tungstène.
Mais ces rubans présentent systématiquement des problèmes de tenue thermomécanique. C'est d'ailleurs pour résoudre de tels problèmes que l'invention correspondant à la demande de brevet européen ci-dessus évoquée a été faite. En particulier, malgré tous les soins portés au laminage des rubans, des phénomènes de contraintes différentielles se produisent dans ceux-ci et ils prennent du fait des échauffements et des refroidissements successifs dans le tube une allure dite en tôle ondulée. Les avantages de disposer d'un émetteur plan sont alors perdus.
En plus de ces défauts, les émetteurs plans ou même les émetteurs filaments présentent l'inconvénient que l'allure du profil énergétique du foyer varie d'une manière non maîtrisée avec la charge du tube. La charge du tube correspond au débit de rayons X. Ce débit est lié à l'importance de l'effet thermoélectronique dans la cathode. Celui-ci est lié à la température à laquelle est portée cette cathode. Or, de plus en plus d'appareils de radiologie sont munis de circuits de régulation pour réguler la charge du tube. Compte tenu du coefficient d'absorption radiologique d'un patient donné à examiner cette régulation agit pour que ce rayonnement qui traverse ce patient soit minimum. Cette régulation agit bien entendu sur le circuit de chauffage de la cathode. La technique de régulation tendant à faire agir cette régulation sur la haute tension entre anode et cathode a été abandonnée car cette technique conduit à modifier pendant l'examen la dureté du rayonnement X utilisé.In general, X-rays are produced by electron bombardment, in a vacuum enclosure, of a target made from a material with a high atomic number. The electrons necessary for the bombardment of this target are released by thermoelectronic effect, generally in a helical filament of tungsten, from a cathode placed precisely within a room of concentration. The concentration piece plays a focusing role at the same time as a Wehnelt role. The target is formed by the anode of the tube. In this very conventional type of configuration, the initial velocities of the electrons at the level of the emitter are very dispersed. Their trajectory therefore has a disordered structure and the focusing system is responsible for correcting them. The focusing system is generally not efficient enough. Consequently, instead of the impact of these bombardment electrons on the target, we obtain a rather complicated tangle of trajectories. This gives the X-ray thermal focus a relatively low energy profile compatible with good image quality. In recent developments, for example in those described in European patent application EP-A-164 665, reference is made to a cathode which is no longer constituted by a filament but which is constituted by a portion of a ribbon having, on the emission of electrons, a flat surface opposite the anode. The advantage of using a planar electron emitter has already been presented prior to this request. It consists in maintaining a certain cohesion of the electronic charges during their trajectory towards the target. In fact, experience has shown that in this case an electrostatic potential distribution is obtained which favors better focusing of the electric charges. The focal point X thus obtained then has a practically homogeneous energy profile, which is beneficial to the quality of the image. The scientific literature relates certain experiments based on this general principle. There is still use of an elaborate transmitter in the form of a tungsten ribbon.
However, these ribbons systematically present thermomechanical behavior problems. It is moreover to solve such problems that the invention corresponding to the European patent application mentioned above was made. In particular, despite all the care taken in rolling the ribbons, phenomena of differential stresses occur in them and they take on due to the successive heating and cooling in the tube a so-called corrugated sheet shape. The advantages of having a plan transmitter are then lost.
In addition to these faults, flat emitters or even filament emitters have the disadvantage that the shape of the energy profile of the fireplace varies in an uncontrolled manner with the load of the tube. The charge of the tube corresponds to the X-ray flow rate. This flow rate is linked to the importance of the thermoelectronic effect in the cathode. This is linked to the temperature to which this cathode is brought. However, more and more radiology devices are provided with regulation circuits to regulate the load of the tube. Given the coefficient of radiological absorption of a given patient to examine this regulation acts so that this radiation passing through this patient is minimum. This regulation of course acts on the heating circuit of the cathode. The regulation technique tending to make this regulation act on the high voltage between anode and cathode has been abandoned because this technique leads to modifying during the examination the hardness of the X-ray used.

Et la modification de la charge du tube n'est pas sans effets sur la distribution énergétique du foyer. Ceci a plusieurs conséquences. En particulier dans certaines situations, du fait de la modification de cette charge du tube, on peut atteindre des densités énergétiques en certains endroits de l'anode qui se situent au delà des densités thermiques acceptables pour cette anode. Dans ce cas l'anode peut être détruite. Les phénomènes de dilatation et de compression des surfaces utiles du foyer thermique sont dus à l'existence de la charge d'espace véhiculée par les électrons avant d'aller frapper la cible. Encore faut-il lier l'importance de cette charge d'espace elle-même à la haute tension nécessaire à l'arrachement des électrons de la cathode.And the modification of the load of the tube is not without effects on the energy distribution of the hearth. This has several consequences. In particular in certain situations, due to the modification of this load of the tube, it is possible to reach energy densities in certain places of the anode which are located beyond the acceptable thermal densities for this anode. In this case the anode can be destroyed. The phenomena of expansion and compression of the useful surfaces of the thermal focus are due to the existence of the space charge conveyed by the electrons before striking the target. Still it is necessary to link the importance of this space charge itself to the high voltage necessary for the pulling of the electrons from the cathode.

Il pourrait être envisageable de modifier la fonction de la pièce de focalisation en fonction de la charge d'espace de manière à limiter par exemple les effets destructeurs d'une augmentation brutale trop importante de la densité thermique du foyer. Indépendamment de la complexité d'un tel asservissement, dans l'état actuel non envisageable, il faudrait en plus que cet asservissement puisse anticiper les dérives thermiques de la densité thermique du foyer.It could be possible to modify the function of the focusing piece as a function of the space charge so as to limit, for example, the destructive effects of a sudden excessive increase in the thermal density of the hearth. Regardless of the complexity of such a control, in the current state which cannot be envisaged, it would also be necessary for this control to be able to anticipate the thermal drifts of the thermal density of the hearth.

Cette solution n'est pas possible. En conséquence, dans l'état actuel de la technique, la régulation apportée sur la charge du tube retentit automatiquement en une variation de l'illumination X, et donc sur la qualité des images résultantes. En définitive, le caractère hétéroclite des effets combinés de la charge d'espace et de la haute tension (de la charge du tube), ne permet pas de disposer de tubes dont au moins certaines caractéristiques d'émission, seraient maîtrisées quelle que soit la charge.This solution is not possible. Consequently, in the current state of the art, the regulation brought about on the load of the tube automatically sounds in a variation of the illumination X, and therefore on the quality of the resulting images. Ultimately, the heterogeneous nature of the combined effects of space charge and high voltage (of tube charge) does not make it possible to have tubes of which at least certain emission characteristics would be controlled whatever the charge.

La présente invention a pour objet de remédier à cet inconvénient en proposant un dispositif émetteur plan, offrant par ailleurs une rigidité mécanique permettant de s'affranchir des problémes de tôle ondulée évoqués ci-dessus. La solution des problèmes de variation de la densité thermique le long du foyer, ou de variation de la dimension de ce foyer en fonction de la charge du tube, peut alors être apportée par l'installation de cette cathode plane dans une pièce de focalisation dite à marche. On a découvert en effet qu'il y avait dans ce cas une autorégulation des caractéristiques de ce foyer. Ainsi, pour une géométrie particulière de la pièce de focalisation à marche on peut obtenir une densité thermique du foyer toujours constante. L'intérêt de cette solution est qu'elle s'applique sur une large gamme de haute tension, entre l'anode et la cathode, de telle façon qu'un même tube servir à plusieurs applications.The object of the present invention is to remedy this drawback by proposing a flat emitting device, moreover offering mechanical rigidity making it possible to overcome the problems of corrugated sheet mentioned above. The solution of the problems of variation of the thermal density along the hearth, or variation of the dimension of this hearth according to the load of the tube, can then be brought by the installation of this planar cathode in a so-called focusing part to walk. It was discovered that there was in this case a self-regulation of the characteristics of this home. Thus, for a particular geometry of the walking focusing piece, it is possible to obtain a thermal density of the focal point which is always constant. The advantage of this solution is that it applies over a wide range of high voltage, between the anode and the cathode, so that the same tube serve several applications.

L'intérêt de disposer d'une densité thermique maîtrisée et donc d'un foyer de dimension variable avec la charge permet à l'utilisateur de disposer avec le même tube d'un grand nombre de foyers de dimensions différentes. En effet, les clichés réalisés avec un foyer fin peuvent être faits à débit plus faible, et lorsque l'utilisateur travaille avec un foyer plus gros, il lui faut davantage de puissance. L'invention met donc à la disposition de l'utilisateur un tube à foyer de dimension continuement variable et réglable et à flux thermique constant sur la cible. On assure ainsi simplement la maîtrise de l'utilisation.The advantage of having a controlled thermal density and therefore a hearth of variable size with the load allows the user to have with the same tube a large number of hearths of different dimensions. Indeed, the photographs taken with a fine focus can be made at a lower speed, and when the user works with a larger focus, he needs more power. The invention therefore makes available to the user a focus tube of continuously variable and adjustable size and with constant thermal flux on the target. This simply ensures control over the use.

Le brevet US-A- 4 344 011 décrit un tube à rayons X comportant une cathode plane disposée à la base d'un dispositif de focalisation à marches.US Pat. No. 4,344,011 describes an X-ray tube comprising a flat cathode disposed at the base of a step focusing device.

La demande de brevet JP-A- 53 030 292 décrit un tube à rayons X comportant une cathode en forme de poutre, cathode disposée à la base d'un dispositif de focalisation à marche.Patent application JP-A-53 030 292 describes an X-ray tube comprising a beam-shaped cathode, cathode disposed at the base of a walking focusing device.

L'invention concerne donc un tube à rayons X avec limitation automatique de la valeur maximum du flux thermique sur l'anode comportant dans une enceinte sous vide une cathode qui émet un faisceau d'électrons et une anode qui émet un rayonnement X, ladite anode faisant face à la cathode de manière à recevoir ledit faisceau d'électrons et ladite cathode étant disposée à la base d'un dispositif de focalisation comportant au moins une marche, caractérisé en ce que ledit dispositif de focalisation est agencé de manière que le point de convergence des électrons soit situé derrière le plan de l'anode et en ce que la cathode est en forme de poutre creuse et comporte une partie émissive plane parallèle à l'axe longitudinal de cette poutre creuse, cette partie faisant face à l'anode.The invention therefore relates to an X-ray tube with automatic limitation of the maximum value of the heat flux on the anode comprising in a vacuum enclosure a cathode which emits an electron beam and an anode which emits X-ray, said anode facing the cathode so as to receive said electron beam and said cathode being arranged at the base of a focusing device comprising at least one step, characterized in that said focusing device is arranged so that the point of Electron convergence is located behind the plane of the anode and in that the cathode is in the form of a hollow beam and has a plane emissive part parallel to the longitudinal axis of this hollow beam, this part facing the anode.

L'invention sera mieux comprise à la lecture de la description qui suit et à l'examen des figures qui l'accompagnent. Celles-ci ne sont données qu'à titre indicatif et nullement limitatif de l'invention. Les figures montrent :

  • figure 1 : une coupe schématique d'un tube radiogène selon l'invention;
  • figure 2 : un diagramme énergétique pour le tube de la figure 1 ;
  • figure 3 : Une vue en perspective d'un exemple d'une cathode plane selon l'invention;
  • figure 4 : une vue en coupe de la cathode de la figure 3.
The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These are given for information only and in no way limit the invention. The figures show:
  • Figure 1: a schematic section of an X-ray tube according to the invention;
  • Figure 2: an energy diagram for the tube of Figure 1;
  • Figure 3: A perspective view of an example of a planar cathode according to the invention;
  • FIG. 4: a sectional view of the cathode of FIG. 3.

La figure 1 montre schématiquement un tube radiogène selon l'invention. Ce tube radiogène comporte, dans une enceinte vide non représentée, une cathode 1 située en vis à vis d'une anode 2. L'anode reçoit un rayonnement électronique 3 sur son foyer 4 et réémet un rayonnement X 5 notamment en direction d'une fenêtre d'utilisation 6. La fenêtre d'utilisation fait partie de l'enveloppe du tube. Selon l'invention la cathode présente la particularité d'opposer une face plane 7 en vis à vis de l'anode 2. Elle présente en outre la particularité d'être insérée dans une optique de focalisation 8 dite à marche. Cette optique de focalisation à marche a pour objet de créer une répartition du champ électrique entre l'anode et la cathode telle que le rayonnement 3 des électrons soit du type convergent. On distingue deux types de rayonnement convergent. Dans un premier type, représenté sur la figure 1, le point de convergence des électrons est situé derrière le plan de l'anode : il est virtuel. Dans ce cas, le rayonnement est dit direct. Dans un deuxième type de rayonnement, dit croisé, le point de convergence des électrons se situe en position intermédiaire entre la cathode 7 et l'anode 2 : il est réel.Figure 1 shows schematically a tube radiogenic according to the invention. This X-ray tube comprises, in an empty enclosure, not shown, a cathode 1 located opposite an anode 2. The anode receives electronic radiation 3 on its hearth 4 and re-emits X-radiation 5 in particular in the direction of a usage window 6. The usage window is part of the tube casing. According to the invention, the cathode has the particularity of opposing a planar face 7 opposite the anode 2. It also has the particularity of being inserted into a focusing optic 8 known as on. The purpose of this walking focusing optic is to create a distribution of the electric field between the anode and the cathode such that the radiation 3 of the electrons is of the convergent type. There are two types of convergent radiation. In a first type, represented in FIG. 1, the point of convergence of the electrons is located behind the plane of the anode: it is virtual. In this case, the radiation is said to be direct. In a second type of radiation, called cross, the point of convergence of the electrons is located in the intermediate position between the cathode 7 and the anode 2: it is real.

Bien que le dispositif de focalisation 8 puisse être également à simple marche, on a trouvé ici plus avantageux de le réaliser à double marche. La pièce de focalisation 8 a une forme prismatique dont la figure 1 représente le plan de section droit. La pièce 8 comporte les deux marches, respectivement 9 et 10 réparties symétriquement en 9′ et 10′ de part et d'autre de la cathode 1. Chaque marche comporte un dessus de marche 91 ou 101 et une contremarche 92 ou 102. (respectivement 91′, 92,′ 101′, 102′). Dans un exemple préféré de réalisation le plan 7 de la cathode 1 est distant de l'anode 4 d'une distance d'environ 7.5 mm. Les dessus 91 et 91′ des marches 9 et 9′ sont distants de l'anode d'environ 7mm. Les dessus 101 et 101′ sont distants, eux, d'environ 6 mm du plan de l'anode 2. La largeur de la cathode 1, mesurée dans le plan de section droite de la pièce prismatique focale 8, vaut 2 mm. La largeur d'un logement 11 où est placée cette cathode à l'intérieur de la pièce focale 8 vaut 2.2 mm. La distance qui sépare les contremarches 92 et 92′ est de 4 mm tandis que la distance qui sépare les contremarches 101 et 102′ est de 5 mm. On peut considérer que les contremarches sont ainsi accolées à des cylindres parallèlépidiques (pris au sens théorique du terme) de largeurs respectives 4 mm et 5 mm. De préférence le dispositif a une allure symétrique par rapport à un plan passant par l'axe 12 du rayonnement, perpendiculairement au plan de la figure. En variante cependant, plutôt que d'être prismatique, l'ensemble peut être circulaire, l'axe 12 servant d'axe de révolution à la cathode ainsi qu'à la pièce de focalisation. Il est possible que l'anode 4 soit une anode de type tournant et même qu'elle présente une face inclinée sur l'axe 12. Dans ce cas les distances indiquées sont plutôt les distances mesurées sur cet axe 12 entre le plan 7 de la cathode et la trace de l'axe 12 sur l'anode 2.Although the focusing device 8 can also be a single step, it has been found here more advantageous to make it double step. The focusing part 8 has a prismatic shape, FIG. 1 of which represents the right section plane. The part 8 comprises the two steps, respectively 9 and 10 distributed symmetrically in 9 ′ and 10 ′ on either side of the cathode 1. Each step has a step 91 or 101 and a riser 92 or 102. (respectively 91 ′, 92, ′ 101 ′, 102 ′). In a preferred embodiment, the plane 7 of the cathode 1 is distant from the anode 4 by a distance of approximately 7.5 mm. Tops 91 and 91 ′ of steps 9 and 9 ′ are distant from the anode by about 7mm. The tops 101 and 101 ′ are spaced about 6 mm from the plane of the anode 2. The width of the cathode 1, measured in the plane of cross section of the focal prismatic part 8, is 2 mm. The width of a housing 11 where this cathode is placed inside the focal piece 8 is 2.2 mm. The distance between risers 92 and 92 ′ is 4 mm while the distance between risers 101 and 102 ′ is 5 mm. We can consider that the risers are thus joined to parallelepidic cylinders (taken in the theoretical sense of the term) of respective widths 4 mm and 5 mm. Preferably, the device has a symmetrical appearance with respect to a plane passing through the axis 12 of the radiation, perpendicular to the plane of the figure. In a variant, however, rather than being prismatic, the assembly can be circular, the axis 12 serving as an axis of revolution for the cathode as well as for the focusing part. It is possible that the anode 4 is a rotating type anode and even that it has an inclined face on the axis 12. In this case the distances indicated are rather the distances measured on this axis 12 between the plane 7 of the cathode and the trace of the axis 12 on the anode 2.

Les dimensions données ci-dessus présentent l'avantage que le flux thermique FT est alors sensiblement constant, pour une haute tension d'utilisation donnée, en fonction de la charge D du tube. En effet, le diagramme de la figure 2 présente trois courbes respectivement 13 à 15 paramétrées par des hautes tensions respectivement de 20 kV, 40 kV ou 50 kV affichant, dans une plage de charge d'utilisation située entre 150 mA et 500 mA, une allure sensiblement plate. Le flux thermique est exprimé en kW par mm². Dans l'exemple indiqué il est toujours inférieur à 50 kW par mm², même pour la haute tension d'utilisation la plus forte. La signification de l'aspect plat de ce flux thermique en fonction de la charge signifie tout simplement que la dimension 16 du foyer thermique évolue linéairement avec la charge. En effet, si la charge augmente, par exemple double, la dimension 16 augmente, et la puissance de rayon X émise augmente également, double. Cecine provoque pas de contraintes thermiques locales anormales sur l'anode puisque le flux thermique reste le même. Cette augmentation de la charge se traduit par l'écartement, selon les flèches 17 et 18, des directions latérales du faisceau d'électrons 3. Celui-ci devient de plus en plus direct.The dimensions given above have the advantage that the thermal flux FT is then substantially constant, for a given high operating voltage, as a function of the load D of the tube. Indeed, the diagram of FIG. 2 presents three curves respectively 13 to 15 parameterized by high voltages respectively of 20 kV, 40 kV or 50 kV displaying, in a range of load of use located between 150 mA and 500 mA, a substantially flat appearance. The heat flux is expressed in kW per mm². In the example shown, it is always less than 50 kW per mm², even for the highest operating high voltage. The significance of the flat appearance of this heat flux as a function of the load simply means that the dimension 16 of the thermal focus evolves linearly with the load. Indeed, if the charge increases, for example double, the dimension 16 increases, and the X-ray power emitted also increases, double. Cecine does not cause abnormal local thermal stresses on the anode since the heat flux remains the same. This increase in charge results in the spacing, according to arrows 17 and 18, of the lateral directions of the electron beam 3. The latter becomes more and more direct.

L'avantage de la présente solution, bien que la dimension du foyer change quand la charge change, est lié au fait qu'on peut ainsi d'une manière simple disposer d'un foyer de dimension choisie. En effet, les courbes 13 à 15 sont des courbes régulières, et sans ondulation. En conséquence, en particulier en métrologie lorsque le problème du débit de dose est un point crucial, ou même en médecine lorsque les limites d'irradiation ne sont pas franchies, on peut choisir en fonction d'une netteté d'image à produire une dimension voulue du foyer. On vient ainsi de présenter un moyen simple de régler à une valeur convenable la dimension de ce foyer.The advantage of the present solution, although the size of the hearth changes when the load changes, is linked to the fact that it is thus possible in a simple manner to have a hearth of chosen dimension. Indeed, the curves 13 to 15 are regular curves, and without undulation. Consequently, in particular in metrology when the problem of the dose rate is a crucial point, or even in medicine when the limits of irradiation are not crossed, one can choose according to a sharpness of image to produce a dimension wanted from home. We have just presented a simple means of adjusting the size of this hearth to a suitable value.

Dans un exemple préféré, la cathode 1 a l'allure d'une poutre représentée en perspective sur la figure 3. Cette poutre est prismatique , creuse, et a sensiblement l'allure d'une maison. La maison est ici présentée comme si elle était couchée sur un de ses murs. La base de la maison constitue la face 7 émissive de la cathode, les murs de la maison tels que le mur 23 possèdent des fenêtres telles que 24. L'intérêt de fabriquer une poutre creuse se situe dans la réduction de la quantité de métal à chauffer. Par ailleurs, la structure de poutre confère à cette cathode une rigidité mécanique évitant les phénomènes de tôle ondulée. Comme la quantité de métal à chauffer est plus faible, l'inertie thermique de la cathode est moins grande, le démarrage du tube peut être plus rapide. Par ailleurs la consommation de l'alimentation de chauffage de la cathode peut être réduite ce qui est un avantage quand on sait les problèmes d'isolement auxquels doivent être confrontés les circuits de chauffage des cathodes.In a preferred example, the cathode 1 has the appearance of a beam shown in perspective in FIG. 3. This beam is prismatic, hollow, and has substantially the appearance of a house. The house is presented here as if it were lying on one of its walls. The base of the house constitutes the emissive face 7 of the cathode, the walls of the house such as wall 23 have windows such as 24. The advantage of manufacturing a hollow beam lies in the reduction of the quantity of metal to be heated. Furthermore, the beam structure gives this cathode mechanical rigidity avoiding corrugated sheet phenomena. As the quantity of metal to be heated is lower, the thermal inertia of the cathode is less, the starting of the tube can be faster. Furthermore, the consumption of the cathode heating supply can be reduced, which is an advantage when we know the insulation problems which the cathode heating circuits must face.

Bien qu'on puisse envisager un chauffage direct de cette cathode en faisant passer un courant électrique directement au travers de celle-ci, on préfère utiliser un filament de chauffage 25 par exemple du même type qu'un filament de chauffage utilisé dans l'état de la technique comme émetteur. Ce filament 25 est lui-même polarisé négativement (plusieurs milliers de volts) par rapport à la cathode 1. Dans un exemple préféré la cathode en poutre est réalisée en tungstène. Afin de limiter également la quantité d'énergie thermique à fournir pour chauffer la cathode on munit le plafond 26 et l'intérieur des murs de celle-ci d'un matelas 27 de fibres isolant thermiquement. Ceci concentre le chauffage sur la partie émissive de la cathode. Dans un exemple les fibres sont des fibres de céramique qui permettent un bon isolement des parois internes latérales de la maison. Les électrons émis par le filament chauffant ne bombardent alors que l'arrière de la cathode 7 selon un dessin représenté par les courbes de champ électrique 28. Ce bombardement est limité à la paroi avant.Although it is possible to envisage direct heating of this cathode by passing an electric current directly through it, it is preferred to use a heating filament 25 for example of the same type as a heating filament used in the state of technology as a transmitter. This filament 25 is itself negatively polarized (several thousand volts) relative to the cathode 1. In a preferred example the beam cathode is made of tungsten. In order also to limit the quantity of thermal energy to be supplied to heat the cathode, the ceiling 26 and the interior of the walls thereof are provided with a mattress 27 of thermally insulating fibers. This concentrates the heating on the emissive part of the cathode. In one example, the fibers are ceramic fibers which allow good insulation of the lateral internal walls of the house. The electrons emitted by the heating filament only bombard the rear of the cathode 7 according to a drawing represented by the electric field curves 28. This bombardment is limited to the front wall.

Par ailleurs cette paroi avant présente un profil concave. Dans un exemple préféré ce profil concave est même tellement concave que des ailes respectivement 29 et 30 de cette cathode présentent des faces intérieures, respectivement 31 et 32, plus proches du filament 25 que ne l'est la face intérieure de la cathode 7 à l'endroit 33 de son milieu. De cette manière les ailes qui sont à la fois plus épaisses, et qui seraient plus dures à chauffer, sont cependant plus chauffées de manière à ce que le sommet de la poutre soit porté en tous points à une température sensiblement constante. De cette manière on émet avec un débit sensiblement constant le rayonnement d'électrons attendu.Furthermore, this front wall has a concave profile. In a preferred example, this concave profile is even so concave that the wings 29 and 30 respectively of this cathode have internal faces, respectively 31 and 32, closer to the filament 25 than is the internal face of the cathode 7 to 1. 'place 33 of its middle. In this way the wings which are both thicker, and which would be harder to heat, are however more heated so that the top of the beam is brought at all points to a substantially constant temperature. In this way, the expected electron radiation is emitted at a substantially constant rate.

Bien que la poutre selon l'invention présente maintenant l'intérêt que sa face émissive 7 ne se distorde plus sous les effets des échauffements, elle subit cependant des dilatations qu'il convient de guider sans les contrarier. Dans ce but la cathode est fixée par une patte unique 34 constituant en quelque sorte la cheminée de la maison. Le mode de fixation est de préférence obtenu par blocage de cette patte 34 entre deux vis 35 et 36 qui viennent l'enserrer entre elles respectivement. Ce montage à un point de fixation présente l'avantage de laisser à la cathode tous les degrés de liberté voulus. Il est en particulier préférable à un mode de fixation avec deux points qui présenterait l'inconvénient que les réactions entre ces deux points se répercuteraient immanquablement sur la planéïté de la surface émissive 7. Pour guider les déplacements de la cathode avec la température, les murs de cette cathode sont maintenus dans la pièce focale 8 par des pions de céramique tels que 37 et 38 qui viennent s'appuyer de part et d'autre sur elle. Ceci permet d'éviter tout phénomène de flexion ou de vibration néfaste à un exact positionnement de l'émetteur dans la pièce de focalisation. Les pions permettent à l'émetteur de se dilater thermiquement suivant sa plus grande longueur tout en le maintenant latéralement dans sa position de référence. En pratique, l'alimentation électrique de la cathode peut être obtenue en faisant passer la haute tension par les vis 35 ou 36. Le pièce focale peut éventuellement être découplée électriquement de la cathode.Although the beam according to the invention now has the advantage that its emissive face 7 no longer distorts under the effects of heating, it nevertheless undergoes expansions which should be guided without upsetting them. For this purpose the cathode is fixed by a single tab 34 constituting in a way the chimney of the house. The method of attachment is preferably obtained by blocking this tab 34 between two screws 35 and 36 which come to grip it between them respectively. This mounting at a fixing point has the advantage of leaving the cathode all the desired degrees of freedom. It is in particular preferable to a method of fixing with two points which would have the disadvantage that the reactions between these two points would inevitably have repercussions on the flatness of the emissive surface 7. To guide the displacements of the cathode with the temperature, the walls of this cathode are held in the focal piece 8 by ceramic pins such as 37 and 38 which come to bear on either side on it. This avoids any phenomenon of bending or vibration harmful to an exact positioning of the transmitter in the focusing part. The pins allow the transmitter to thermally expand along its greatest length while keeping it laterally in its reference position. In practice, the electrical supply of the cathode can be obtained by passing the high voltage through the screws 35 or 36. The focal piece can optionally be electrically decoupled from the cathode.

Claims (8)

1. A x-ray tube with an automatic limitation of the maximum value of the thermal flux onto the anode comprising, a vacuum enclosure, a cathode (1) which emits a beam of electrons and an anode (2) which emits x-rays (5), the said anode (2) facing the cathode (1) in such a manner as to receive the said beam of electrons and the said cathode (1) being positioned at the base of a focussing device (8) comprising at least one step, characterized in that the said focussing device is adapted in such a manner that the point of convergence of the electrons is positioned to the rear of the plane of the anode and in that the cathode is in the form of a hollow beam comprising a plane emitting part (7) which is parallel to the longitudinal axis of this hollow beam, said part facing the anode (2).
2. The x-ray tube as claimed in claim 1, characterized in that the plane emitting part (7) is heated by a device (25) for indirect heating.
3. The x-ray tube as claimed in claim 2, characterized in that the indirect heating device comprises a heating filament (25) and a mattress (27) of fibers in order to concentrate the heating effect on the plane emitting part (7).
4. The x-ray tube as claimed in claim 2 or in claim 3, characterized in that an internal face of the cathode, corresponding to the plane emitting part (7), has a concave configuration (29 and 30) with wings which are nearer to the heating device than an internal central part (33) of the concave configuration.
5. The x-ray tube as claimed in any one of the preceding claims 2 through 4, characterized in that at least one of the walls of the beam comprises a recess (24).
6. The x-ray tube as claimed in any one of the preceding claims 1 through 5, characterized in that this beam is fixed to the tube by a single foot (34) which is arrested in position by two screws (35 and 36) which act to grip it in such a manner as to provide the cathode with all the required degrees of freedom.
7. The x-ray tube as claimed in any one of the preceding claims 1 through 6,, characterized in that the beam is guided by lugs (37 and 38) of ceramic material fixed on both sides thereof on the focussing device (8).
8. The x-ray tube as claimed in any one of the preceding claims 1 through 7, characterized in that:
- the plane of the emitting part (7) of the cathode is at a distance of approximately 7.5 mm from the anode (2),
- the focussing device (8) comprises:
- a deep plane in common with the plane of the plane emitting part (7) of the cathode which is delimited by backward steps (92 and 92′) separated by approximately 4 mm,
- an intermediate plane (91 and 91′) positioned at approximately 7 mm from the anode and delimited by backward steps (102 and 102′) separated by approximately 5 mm, and
- an upper plane (101 and 101′) positioned at approximately 6 mm from the anode.
EP89401760A 1988-07-01 1989-06-22 X-ray tube with a variable focal spot adjusting itself to the charge Expired - Lifetime EP0349386B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8808958 1988-07-01
FR8808958A FR2633774B1 (en) 1988-07-01 1988-07-01 SELF-ADAPTED VARIABLE FIREPLACE X-RAY TUBE

Publications (2)

Publication Number Publication Date
EP0349386A1 EP0349386A1 (en) 1990-01-03
EP0349386B1 true EP0349386B1 (en) 1992-05-27

Family

ID=9367995

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89401760A Expired - Lifetime EP0349386B1 (en) 1988-07-01 1989-06-22 X-ray tube with a variable focal spot adjusting itself to the charge

Country Status (6)

Country Link
US (1) US5060254A (en)
EP (1) EP0349386B1 (en)
JP (1) JP2840614B2 (en)
DE (1) DE68901636D1 (en)
ES (1) ES2032128T3 (en)
FR (1) FR2633774B1 (en)

Families Citing this family (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5566220A (en) * 1992-12-04 1996-10-15 Kabushiki Kaisha Toshiba X-ray computerized tomography apparatus
USH1627H (en) * 1994-01-31 1997-01-07 The United States Of America As Represented By The Secretary Of The Army Method of and apparatus for image processing using a variable focal spot size
US5896486A (en) * 1997-05-01 1999-04-20 Lucent Technologies Inc. Mass splice tray for optical fibers
US5907595A (en) * 1997-08-18 1999-05-25 General Electric Company Emitter-cup cathode for high-emission x-ray tube
US6302243B1 (en) * 1999-10-29 2001-10-16 Stoptech Technologies Llc Stiffening bracket for brake calipers
DE10025807A1 (en) * 2000-05-24 2001-11-29 Philips Corp Intellectual Pty X-ray tube with flat cathode
US7180981B2 (en) 2002-04-08 2007-02-20 Nanodynamics-88, Inc. High quantum energy efficiency X-ray tube and targets
US6785359B2 (en) * 2002-07-30 2004-08-31 Ge Medical Systems Global Technology Company, Llc Cathode for high emission x-ray tube
US7653178B2 (en) * 2004-08-20 2010-01-26 Satoshi Ohsawa X-ray generating method, and X-ray generating apparatus
JP4273059B2 (en) * 2004-08-20 2009-06-03 志村 尚美 X-ray generation method and X-ray generation apparatus
EP2419909B1 (en) * 2009-04-14 2013-01-23 Siemens AG Beam head
JP5614854B2 (en) * 2012-03-27 2014-10-29 株式会社リガク Electron gun, X-ray generator and X-ray measuring device
CN105869975B (en) * 2016-05-30 2018-03-06 黄石上方检测设备有限公司 A kind of high reliability safety check ceramics X-ray tube

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0164665A1 (en) * 1984-05-31 1985-12-18 Kabushiki Kaisha Toshiba X-ray tube apparatus

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE416533C (en) * 1921-06-14 1925-07-17 Siemens & Halske Akt Ges Incandescent cathode for high vacuum discharge tubes with a heating element that is heated by an electric current and is arranged within a housing-like part that is closed on all sides
US1923876A (en) * 1931-02-25 1933-08-22 Wappler Electric Company Inc Means and method of producing an X-ray focus varying with the x-ray tube load
JPS5178696A (en) * 1974-12-28 1976-07-08 Tokyo Shibaura Electric Co x senkan
US4126805A (en) * 1975-10-18 1978-11-21 Emi Limited X-ray tubes
JPS5330292A (en) * 1976-09-01 1978-03-22 Toshiba Corp X-ray tube
FR2411487A1 (en) * 1977-12-09 1979-07-06 Radiologie Cie Gle High diffusion and fine focussing cathode for X=ray tube - has emitter with curvilinear shape focussing unit concentrating beam at anode impingement point
JPS5568056A (en) * 1978-11-17 1980-05-22 Hitachi Ltd X-ray tube
JPS55108158A (en) * 1979-02-13 1980-08-19 Hitachi Ltd Cathode for x-ray tube
JPS60254538A (en) * 1984-05-31 1985-12-16 Toshiba Corp X-ray tube device

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0164665A1 (en) * 1984-05-31 1985-12-18 Kabushiki Kaisha Toshiba X-ray tube apparatus

Also Published As

Publication number Publication date
FR2633774B1 (en) 1991-02-08
JP2840614B2 (en) 1998-12-24
JPH0254847A (en) 1990-02-23
FR2633774A1 (en) 1990-01-05
EP0349386A1 (en) 1990-01-03
US5060254A (en) 1991-10-22
ES2032128T3 (en) 1993-01-01
DE68901636D1 (en) 1992-07-02

Similar Documents

Publication Publication Date Title
EP0349386B1 (en) X-ray tube with a variable focal spot adjusting itself to the charge
EP0163321B1 (en) X-ray tube apparatus
JP4169219B2 (en) X-ray generator
US7382862B2 (en) X-ray tube cathode with reduced unintended electrical field emission
US5703924A (en) X-ray tube with a low-temperature emitter
JP2011222456A (en) X-ray source and x-ray photographing device
CN101042975B (en) X-ray generating method and X-ray generating apparatus
JPS60157147A (en) Optical control x-ray scanner
JP2011505668A (en) Laser heating discharge plasma EUV light source
US7436931B2 (en) X-ray source for generating monochromatic x-rays
JP7117452B2 (en) High brightness reflection type X-ray source
FR2548447A1 (en) X-ray tube with high-intensity focus
EP0349388B1 (en) X-ray tube with self-limitation of the electron flux by saturation
US20130129045A1 (en) Transmission type radiation generating source and radiography apparatus including same
CN101523545A (en) X-ray tube, X-ray system, and method for generating X-rays
JPH05283021A (en) X-ray tube
EP0349387B1 (en) Indirectly heated x-ray tube with a flat cathode
CA1278017C (en) X-ray source
FR2900305A1 (en) Focal spot size stabilizing method for x-ray tube, involves applying bias voltage between filament and concentration part terminals, measuring spot size and contrast modulation function, and adjusting spot size and function using voltage
JPS61218100A (en) X-ray tube and x-ray photographing device utilizing same
RU2161843C2 (en) Point high-intensity source of x-ray radiation
US1923876A (en) Means and method of producing an X-ray focus varying with the x-ray tube load
JPH04212248A (en) X-ray tube having exit window
US6359968B1 (en) X-ray tube capable of generating and focusing beam on a target
FR2819141A1 (en) 2D/3D diagnostic X ray radiology having vacuum chamber with central double rotating target end producing two distinct/same/electron beams and output windows ceramic outer held.

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE ES GB IT NL

17P Request for examination filed

Effective date: 19900122

17Q First examination report despatched

Effective date: 19900518

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19920526

Year of fee payment: 4

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE ES GB IT NL

ITF It: translation for a ep patent filed

Owner name: JACOBACCI & PERANI S.P.A.

REF Corresponds to:

Ref document number: 68901636

Country of ref document: DE

Date of ref document: 19920702

GBT Gb: translation of ep patent filed (gb section 77(6)(a)/1977)
REG Reference to a national code

Ref country code: ES

Ref legal event code: FG2A

Ref document number: 2032128

Country of ref document: ES

Kind code of ref document: T3

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19930520

Year of fee payment: 5

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: ES

Payment date: 19930615

Year of fee payment: 5

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19930625

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19930630

Year of fee payment: 5

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19940101

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19940622

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: ES

Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION

Effective date: 19940623

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19940622

REG Reference to a national code

Ref country code: ES

Ref legal event code: FD2A

Effective date: 19990601

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.

Effective date: 20050622