EP2232520A1 - Radiogenic source comprising at least one electron source combined with a photoelectric control device - Google Patents

Radiogenic source comprising at least one electron source combined with a photoelectric control device

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Publication number
EP2232520A1
EP2232520A1 EP09703777A EP09703777A EP2232520A1 EP 2232520 A1 EP2232520 A1 EP 2232520A1 EP 09703777 A EP09703777 A EP 09703777A EP 09703777 A EP09703777 A EP 09703777A EP 2232520 A1 EP2232520 A1 EP 2232520A1
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EP
European Patent Office
Prior art keywords
ray source
source according
ray
target
photocathodes
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.)
Granted
Application number
EP09703777A
Other languages
German (de)
French (fr)
Other versions
EP2232520B1 (en
Inventor
Pierre Legagneux
Ludovic Hudanski
Pascal Ponard
Christophe Bourat
Jean-Philippe Schnell
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Thales SA
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Thales SA
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Publication of EP2232520A1 publication Critical patent/EP2232520A1/en
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Publication of EP2232520B1 publication Critical patent/EP2232520B1/en
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Classifications

    • 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
    • H01J35/065—Field emission, photo emission or secondary emission cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/06—Cathode assembly
    • H01J2235/062—Cold cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/06—Cathode assembly
    • H01J2235/068—Multi-cathode assembly

Definitions

  • X-ray source comprising at least one electron source associated with a photoelectric control device.
  • the field of the invention is that of the X-ray sources, generally used in industrial, scientific and medical applications in order to provide the flow of photons that makes it possible, in particular, to produce the images according to different reconstruction techniques in two or three spatial dimensions.
  • These X-ray sources are also interesting in the field of safety, including inspection of luggage and parcels by X-rays.
  • X transmission is another usable technique. It gives access to a combination of the density of the material p and its effective atomic number Z ⁇ , but not to each of these two quantities separately, and moreover, the contributions of several elements constituting the package are superimposed according to the thickness crossed. 3D imaging by transmission to a power allows a mapping of the attenuation coefficient ⁇ at any point of an object. This technique therefore makes it possible to overcome the thickness traversed.
  • the attenuation coefficient ⁇ is a function of the density of the material p, of its Z e ff and depends on the energy.
  • the multi-energy X-ray transmission in 3D finally makes it possible to determine p, and Z e tf.
  • FIG. 1a showing a filament filament facing an anode A
  • a first limitation comes from inertia thermal of this type of cathode prohibiting a fast modulation of the current therefore the dose rate RX (given energy, the dose rate is often controlled by the current delivered by the cathode, if the rising or stopping fronts are not steep, this will result in transient phases of X-ray emission that can affect the quality of the image received on the detector).
  • a second limitation is related to the need to have a complex filament supply, if it is referenced to the high voltage.
  • the various insulating passages for polarizing grid, filament and cathode are also more complex and bulky because they have to withstand the high voltages (20 to 60OkV) generally encountered in the X-ray tubes.
  • each X-ray source generally consists of at least one cathode, a filament, a current control gate (if it is modulated), brought to different high voltages through a high voltage insulator as shown in FIG. 2c. .
  • the final size of the X-ray source is strongly influenced by the size of this insulation. Given these constraints of connection and electrical isolation, it is very difficult to consider two (or more) X sources in the same vacuum envelope. Thus existing systems comprising several sources X consist of several separate X-ray tubes.
  • the gate cathode capacity limits the maximum modulation frequency
  • the current emitted by the cathode varies exponentially with the voltage applied to the gate degrading the quality of the servocontrol of the current emitted by the cathode
  • the gate is not completely transparent to the electronic flux, it intercepts from 30 to 50% of the current emitted by the cathode, favoring the dimensional variations of this grid resulting from warming and consequently generating instability of the current emitted by the cathode due to the exponential variation described above. Thermal inertia and embrittlement are aggravating factors. • The fraction of current intercepted by the grid and heating thereof resulting therefrom are also limitations for use of this type of cathode at high currents (a few tens of mA). For example, for a cathode of an X-ray tube whose voltage would be 15kV for a current of 2 mA, a gate intercepting 40% of the current should dissipate 120W.
  • 3D imaging devices are of two types. In the first type, they comprise an X-ray generator and a detector facing each other, making it possible to measure the radiation that has passed through the object or the patient. In order to multiply the angles of view, these systems require the rotation of the source and the detector or the object or the patient. These systems are generally heavy and complex and require a significant analysis time incompatible with the new needs.
  • the second type allows 3D imaging techniques without any movement of the system or the object. They require several X-ray generators and several detectors allowing the observation under different incidences and imposing a recombination of the images obtained to extract the 3D information. These so-called tomosynthesis systems are simpler than the previous ones and can greatly reduce the analysis time and the complexity of the system.
  • some X-ray tubes include, in addition to the continuous high voltage, a linear accelerator (linac, abbreviated Anglo-Saxon) to carry the electrons at very high energy in order to produce X-rays themselves of very high energy.
  • the injection of electrons into an accelerator structure of a linear accelerator is carried out in its conventional configuration using a cathode-based thermononic effect electron gun with grid or without grid.
  • the electronic emission is controlled by the heating of the cathode filament and / or the polarization of the control gate.
  • the present invention proposes in response an X-ray source comprising a cold source of electrons subjected to an electric field and operating by field emission, and a photoconductive element placed in series with the electron emitter so that the photogenerated current by illumination in the photoconductive device is equal to that of the transmitter.
  • the emitted current is controlled by illumination, directly, and not via a voltage control of an extraction electrode.
  • This arrangement guarantees a linear dependence of the emission current with the illumination and a very sensitive servocontrol of very good quality of the emitted current.
  • the subject of the invention is an X-ray source comprising at least one vacuum chamber, means for introducing an optical wave, at least one cold source capable of emitting electrons in a vacuum by the phenomenon of the emission of field when subjected to a field, at least one supply providing a high electrical voltage, at least one anode comprising a material capable of emitting X-rays under the effect of electronic bombardment and at least one window allowing the exit of X-rays, at least one source of light providing said optical wave, characterized in that the cold source comprises at least one substrate provided with at least one conductive surface, and is subjected to an electric field resulting from the application of the high voltage between at least one conductive surface and the anode; said cold source further comprising at least one photoconductive element in which the current is controlled by illumination and at least one electron emitting element, said photoconductive element being electrically connected in series between at least one emitter element and a conductive surface, so that the photogenerated current in the photoconductive device is equal to that of the emitter or group of
  • the cold source can operate without extraction grid.
  • the cold source can thus be set at the high negative voltage, and the target anode at the electrical ground, simplifying the cooling of the target anode.
  • such a system simplifies the galvanic decoupling of the current control devices, by the galvanic isolation provided by the optical control.
  • control circuits can be at low voltage.
  • the conductive surface (s), the photoconductor (s) and the emitting element (s) are integrated on the substrate in a monolithic manner and thus constitute a photocathode.
  • the source comprises at least one cold source of electrons with emitting points.
  • the source comprises an emitting tip for forming a point source for high resolution X-ray imaging.
  • a single emitting tip whose sharp image produced by an electronic optics on the target X is necessarily smaller (substantially punctual) than that of a network of emitting points.
  • An image of the object studied with such a source X will necessarily be higher resolution than an image obtained with an X source associated with an extended network of points.
  • the source comprises at least one cold source of electron emitting tip carbon nanotube or metal nanowires.
  • the target material of the electron bombardment is tungsten or composite comprising tungsten or other high Z refractory material.
  • photoconductive device device whose conduction state is controlled by illumination.
  • the photoconductive device is of the semiconductor photodiode type with a PIN structure where P denotes a P doped zone, I designates an intrinsic or unintentionally doped or slightly doped zone, and N denotes an N doped zone.
  • the photoconductive device is a MIN diode or M denotes a metal zone,
  • the photoconductive element comprises a metal layer with at least one of its contact faces.
  • the cold source comprises at least one conductive substrate comprising at least one electron emitter and a photoconductive device so as to form at least one photocathode.
  • the cold source comprises at least one conducting substrate at least one point whose apex is at a height h with respect to the conductive substrate and at least one photoconductive element disposed between the tip and the conductive substrate such that the tip is remote from its possible neighbors by a distance d substantially equal to or greater than twice the height h, and such that the lateral dimensions phi of the photoconductive elements are approximately equal to or less than the height h.
  • the emitters or groups of emitters are arranged in regular networks.
  • the substrate comprises a so-called front face supporting the emitter element, the light source illuminating said front face.
  • the substrate is transparent to said light source, said light source illuminating said substrate opposite to the front face.
  • the substrate has a thinned zone intended to be illuminated, so as to minimize the phenomena of absorption, said source of light illuminating said substrate opposite to the front face.
  • the X-ray source further comprises means for adjusting the optical power of the light source to adjust the power of X-rays generated. It can also advantageously include means for adjusting the focus of the light source on the electron source.
  • the source comprises a monotube X of cylindrical symmetry comprising an enclosure, enclosing a photocathode, a target, a mirror for illuminating the photocathode with a light beam perpendicular to the axis of the mono-tube from of the illumination source, and an optical window for collecting the emission X.
  • the X-ray source comprises several single-tubes X, a circular support supporting said radially arranged mono-tubes X, a high-voltage power supply, distribution means of said high-voltage power supply on the different single-tubes. in order to produce X-ray beams, and individual independent optical control means dedicated to each of the single-tubes.
  • said optical control beams and the X-ray beams are all parallel to each other and perpendicular to said circular support.
  • the X-ray source further comprises means for converging said X-ray beams.
  • the X-ray source comprises an enclosure, several assemblies each consisting of a pair consisting of a photocathode associated with a target and power distribution means of said photocathodes.
  • the enclosure has a concave shape so as to generate convergent X-ray beams.
  • the X-ray source comprises:
  • an extended photocathode or a set of photocathodes a so-called extended target or set of targets respectively facing said extended photocathode or the set of photocathodes;
  • the source comprises a spatial and / or temporal modulator making it possible to deflect a beam originating from the illumination source, to different areas of the extended photocathode or different photocathodes among a set of photocathodes.
  • the addressing device is a spatial light modulator illuminated by an extended beam for transferring different illumination laws to an area of the extended photocathode or a photocathode in the set of photocathodes, and obtaining the corresponding X-ray emission laws from an extended target area or target of the set of targets.
  • the source comprises a set of illumination sources and is characterized in that the addressing device is an opto-mechanical or opto-electric deflector and activates illumination sources associated in a one-to-one manner. to different areas of the extended photocathode or to different photocathodes in the set of photocathodes, said zones or photocathodes being associated one-to-one with different areas of the extended target or with different targets in the set of targets.
  • the light power distribution is carried out at least partly by guided propagation (optical fibers) instead of spatial propagation.
  • the vacuum chamber comprises passages for the optical fibers
  • the spatial modulators are of guided propagation type.
  • the spatial modulators are of guided propagation type.
  • the X-ray source comprises a vacuum chamber, and at least one compound triplet coaxially and consecutively: a photon-transparent window of a photocathode polarized at the negative high voltage of a target and the power supply means of these elements.
  • the X-ray source provides an arrangement of the triplets so that they generate spatially convergent X-beams.
  • the X-ray source provides an arrangement of the triplets so that they generate parallel X-beams organized in a matrix manner. According to a variant of the invention, the X-ray source provides an arrangement of the triplets so that they generate parallel X-beams and organized circularly.
  • the X-ray source provides an arrangement of the triplets so that they generate parallel groups of X-beams, these groups being perpendicular to each other.
  • the X-ray source further comprises at least one linear accelerator for accelerating the electrons emitted by the electron source.
  • the applied illumination allows a unit control of the current of each emitter avoiding the risks of destruction of these emitters related to differences in the height of the nanotubes and which are encountered in the case of control by an electrode or conductive plane whose voltage is varied.
  • No emitter array has to be defined structurally, as in the case of control by an electrode or conductive plane whose voltage is varied, thus allowing any possible definitions of the emitting zones engaging at least one photocathode .
  • FIGS. 1a, 1b illustrate examples of thermionic cathodes of the known art
  • FIGS. 2a, 2b and 2c illustrate examples of thermionic cathodes of the known art further comprising an intermediate gate
  • FIGS. 3a and 3b illustrate examples of cold cathodes according to the known art
  • FIG. 4 illustrates a principle of X-ray source according to the invention
  • FIG. 5 schematizes an X-ray source according to the invention relating to a monotube X of cylindrical symmetry
  • FIGS. 6a and 6b illustrate another example of an X-ray source according to the invention relating to several radially arranged monotubes X
  • FIGS. 7a, 7b, 7c and 7d illustrate another example of an X-ray source according to the invention, relating to an enclosure enclosing a plurality of sources arranged differently;
  • FIG. 8 shows an example of modulation of the electronic spot on the target only related to the zone of illumination (no grid or "emitter array” mechanically determining the emission zones);
  • FIGS. 9a and 9b illustrate the difference in current response of the transmitter (exponential in the presence of a control gate, linear in the presence of a photocathode according to the invention).
  • FIGS. 10a and 10b illustrate the ability to activate local emissive zones radiating an extended target
  • FIG. 11 a presents a schematic diagram of the invention
  • FIGS. 11b, 11c, 11d specify alternative configurations of integrated photocathodes.
  • the invention proposes the implementation in the same X-ray source, one or more cold cathodes whose remission is controlled by a photoconductive device, this type of device can typically be of type such as that described in the patent No.
  • the X-ray source of the invention comprises at least one photoconductive control device 10, an electron source 11 that irradiates a target 12 so that the latter emits an X-ray beam , 13.
  • This type of optical decoupling makes it possible to envisage multiple source configurations in the same vacuum chamber, localized or spatially distributed and producing a continuous X-ray or modulated temporally according to the illumination of the photo cathode.
  • the X-ray source is a single-beam source and comprises a vacuum enclosure 20, high-voltage supply means 21 and means electrical insulation 22, an illumination source 23 directing a light beam 24 towards an optically reflective device 25 for the wavelengths used to excite the light-sensitive layers of a cathode 26 enabling generating a stream of electrons 27, towards a target 28.
  • the bombardment of said target then generates the X-ray flux, 30 through a window 29 transparent to said X-rays which the enclosure is equipped with.
  • the enclosure may also be equipped with cooling means 31 for the target subjected to intense heating during the bombardment operations by the electron flows.
  • the X-ray source has a multiplicity of ray fluxes
  • X, 40i thanks to the presence of a series of enclosures (X-ray tubes) 41 i distributed in a circular support 42, said circular support further comprises means for distributing a high-voltage power supply 43 as illustrated in FIG. Figure 6a and 6b.
  • the X-ray source may also be multi-beam and include a single enclosure as shown in Figure 7a, 7b, 7c, 7d.
  • said enclosure 50 may advantageously be in several forms integrating electron sources arranged differently.
  • the non-exhaustive examples show a planar convergent organization (FIG. 7a), parallel organized circularly (FIG. 7b), parallel organized perpendicularly (FIG. 7c), parallel organized in a matrix manner (FIG. 7d).
  • FIG. 8 illustrates an example of means for modulating the electronic spot on the target only linked to the illumination zone (no grid or "emitter array” mechanically determining the emission zones).
  • the present invention proposes in response an X-ray source comprising an electrically-field-fed cold-field source operating by field emission, and a photoconductive element placed in series with the electron-emitter so that the photogenerated current by illumination in the photoconductive device is equal to that of the transmitter.
  • the emitted current is controlled by illumination, directly, and not via a voltage control of an extraction electrode.
  • This arrangement guarantees a linear dependence of the emission current with the illumination and a very sensitive servocontrol of very good quality of the emitted current.
  • Figures 9a and 9b illustrate the difference in current response of the transmitter.
  • this response is exponential in the presence of a control gate, and linear in the presence of a photocathode according to the invention.
  • multi-beam X-ray sources comprising a set of elementary electron sources associated with elementary targets.
  • the multi-beam X-ray source may also comprise an extended electron source, comprising electron emission zones, capable of irradiating an extended target to generate X-ray beams (as illustrated in FIGS. 10a and 10b).
  • This type of source associated with scanning means can typically be used for an imaging configuration such as fluoroscopy for example.
  • the X-ray source is a micro-focus or nano-focus source comprising optical means providing a focus such that a single nanotube is addressed to generate an electron beam.
  • the target irradiated with a single nanotube consequently also provides a very small focal spot x-ray beam.
  • the diameter of the spot of the micro or nano source X can be adjusted according to the surface of the illuminated area and thus allow to enslave the spot diameter according to the power density on the target.
  • a focusing system, magnetic or electrostatic may be used to focus on the target all the electrons emitted by the end of the nanotube in a thermal spot of size comparable to that of the emitting surface, being of the order of 10 to 100 nm in diameter.
  • This type of X-ray source can advantageously provide access to non-destructive control of integrated circuit transistor gate, for example.
  • the X-ray source may also comprise an accelerator structure called "linac". associated with the cold source, a photoelectric device for controlling the emission of electrons by the cold source, and a light source for controlling by illumination said photoelectric device.
  • linac an accelerator structure associated with the cold source
  • a photoelectric device for controlling the emission of electrons by the cold source
  • a light source for controlling by illumination said photoelectric device.
  • the combination allows a simplification of the accelerator, a reduction in its volume and an improvement in the quality of the electron beam and the X-radiation it produces.
  • the first cavities of the accelerator conventionally dedicated to the temporal shaping of the beam can be simplified;
  • the beam is easily focused at the output of the accelerator, allowing very specific sources of radiation on the conversion target;
  • Figures 11a, 11b, 11c and 11d illustrate in detail an example of an X-ray source of the invention.
  • this X-ray source comprises a vacuum chamber 50, means 56h for introducing an optical wave 56i, a cold source 52 capable of emitting electrons 52i in a vacuum by the phenomenon of field emission when it is subjected to a field, a power supply 55 providing a high electrical voltage, an anode 53 comprising a material 53j capable of emitting X-rays, 53i under the effect of electronic bombardment and at least one window 54 enabling the X-ray output, at least one light source 56 providing said optical wave.
  • the cold source also comprises at least one substrate 57 provided with at least one conductive surface 55, and is subjected to an electric field resulting from the application of the high voltage between at least one conductive surface 55 and the anode 53; said cold source further comprising at least one photoconductive element 58 in which the current is controlled substantially linearly by the illumination and at least one electron emitting element 59, said photoconductive element 58 being electrically connected in series between at least one transmitting element 59 and a conductive surface 55, so that the photogenerated current in the photoconductive device is equal to that emitted by the emitter or group of emitters with which it is associated, and so that the emitted X-ray flux is substantially linearly depending on the illumination.

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  • X-Ray Techniques (AREA)

Abstract

The invention relates to a radiogenic source comprising a vacuum chamber (50), means (56h) for injecting an optical wave (56i), a cold source (52), enabling electrons (52i) to be emitted in the vacuum by field emission when it is subjected to a field, a power supply (55) delivering a high electrical voltage, an anode (53) comprising a material (53j) capable of emitting X-rays (53i) under the effect of electron bombardment, and at least one window (54) through which the X-rays exit, at least one light source (56) delivering said optical wave, characterized in that the cold source comprises at least one substrate (57) provided with at least one conducting surface (55) and is subjected to an electric field resulting from applying the high voltage between at least one conducting surface (55) and the anode (53), said cold source further including at least one photoconductive element (58) in which the current is controlled substantially linearly by the illumination and at least one electron emitter element (59), said photoconductive element (58) being electrically connected in series between at least one emitter element (59) and a conducting surface (55), so that the current photogenerated in the photoconductive device is equal to that emitted by the emitter or the group of emitters with which it is associated, and so that the emitted X-ray flux is substantially linearly dependent on the illumination.

Description

Source radiogène comprenant au moins une source d'électrons associée à un dispositif photoélectrique de commande. X-ray source comprising at least one electron source associated with a photoelectric control device.
Le domaine de l'invention est celui des sources radiogènes, généralement utilisées dans des applications industrielles, scientifiques et médicales afin de fournir le flux de photons permettant notamment la réalisation des images suivant différentes techniques de reconstruction en deux ou trois dimensions spatiales. Ces sources radiogènes sont également intéressantes dans le domaine de la sûreté, notamment l'inspection de bagages et colis par rayons X.The field of the invention is that of the X-ray sources, generally used in industrial, scientific and medical applications in order to provide the flow of photons that makes it possible, in particular, to produce the images according to different reconstruction techniques in two or three spatial dimensions. These X-ray sources are also interesting in the field of safety, including inspection of luggage and parcels by X-rays.
Depuis longtemps, des systèmes fixes basés sur l'imagerie X en transmission, sont utilisés pour la sécurité aéroportuaire. Depuis une dizaine d'années, les besoins de sécurisation de lieux publics vont croissant et requièrent des systèmes sur plateformes mobiles pour détecter des substances chimiques dangereuses ou des explosifs cachés dans des bagages ou colis. Les systèmes mobiles existants utilisent en particulier la rétrodiffusion de rayons X. Cependant, la capacité de détection et d'identification demeure limitée. Il est en particulier difficile de discriminer entre des substances de densités voisines. La transmission X est une autre technique utilisable. Elle donne accès à une combinaison de la densité du matériau p et de son numéro atomique effectif Z^, mais pas à chacune de ces deux grandeurs séparément, et de plus, les contributions de plusieurs éléments constituant le colis se superposent en fonction de l'épaisseur traversée. L'imagerie 3D par transmission à une énergie permet une cartographie du coefficient d'atténuation μ en tout point d'un objet. Cette technique permet donc de s'affranchir de l'épaisseur traversée.For a long time, fixed systems based on X-ray imaging in transmission, are used for airport security. Over the past decade, the need to secure public spaces has been growing, requiring systems on mobile platforms to detect dangerous chemicals or explosives hidden in luggage or parcels. Existing mobile systems in particular use X-ray backscatter. However, the detection and identification capability remains limited. In particular, it is difficult to discriminate between substances of similar densities. X transmission is another usable technique. It gives access to a combination of the density of the material p and its effective atomic number Z ^, but not to each of these two quantities separately, and moreover, the contributions of several elements constituting the package are superimposed according to the thickness crossed. 3D imaging by transmission to a power allows a mapping of the attenuation coefficient μ at any point of an object. This technique therefore makes it possible to overcome the thickness traversed.
Le coefficient d'atténuation μ est une fonction de la densité du matériau p, de son Zeff et dépend de l'énergie. La transmission X multi- énergies en 3D permet finalement de déterminer p, et Zetf.The attenuation coefficient μ is a function of the density of the material p, of its Z e ff and depends on the energy. The multi-energy X-ray transmission in 3D finally makes it possible to determine p, and Z e tf.
Il existe un besoin réel de systèmes d'identification fiables, et de mise en œuvre rapide et aisée. Ces systèmes nécessitent la mise en œuvre de sources radiogènes autorisant une imagerie en trois dimensions sans déplacement mécanique du système de source. Dans la plupart des cas, les sources radiogènes utilisent des cathodes thermo-ioniques comme émetteur d'électrons mais ces solutions présentent plusieurs limitations :There is a real need for reliable identification systems, and quick and easy implementation. These systems require the use of X-ray sources that allow three-dimensional imaging without mechanical displacement of the source system. In most cases, the X-ray sources use thermionic cathodes as electron emitters, but these solutions have several limitations:
Dans le cas des cathodes thermoïoniques à chauffage directIn the case of direct heating thermionic cathodes
(figure 1a) représentant un filament Fil en regard d'une anode A, ou à chauffage indirect (figure 1 b) représentant un filament Fil chauffant une cathode Cath imprégnée en regard d'une anode A, une première limitation provient de l'inertie thermique de ce type de cathode interdisant une modulation rapide du courant donc du débit de dose RX (à énergie donnée, le débit de dose est souvent commandé par le courant débité par la cathode, si les fronts de montée ou d'arrêt ne sont pas raides, cela se traduira par des phases transitoires d'émission de rayonnement X pouvant nuire à la qualité de l'image reçue sur le détecteur). Une seconde limitation est liée à la nécessité d'avoir une alimentation du filament complexe, si elle est référencée à la haute tension. Les différents passages isolants permettant de polariser grille, filament et cathode sont également plus complexes et volumineux car ils doivent supporter les tensions élevées (20 à 60OkV) généralement rencontrées dans les tubes radiogènes.(FIG. 1a) showing a filament filament facing an anode A, or indirectly heating (FIG. 1b) representing a filament filament heating a cath cathode impregnated opposite an anode A, a first limitation comes from inertia thermal of this type of cathode prohibiting a fast modulation of the current therefore the dose rate RX (given energy, the dose rate is often controlled by the current delivered by the cathode, if the rising or stopping fronts are not steep, this will result in transient phases of X-ray emission that can affect the quality of the image received on the detector). A second limitation is related to the need to have a complex filament supply, if it is referenced to the high voltage. The various insulating passages for polarizing grid, filament and cathode are also more complex and bulky because they have to withstand the high voltages (20 to 60OkV) generally encountered in the X-ray tubes.
Pour remédier au problème de dynamique de contrôle du courant évoqué ci-dessus, des dispositifs utilisent une grille G polarisée, formée par exemple par des fils ou grillage, ou plaque percée comme illustré en figure 2a et 2b. Ainsi chaque source radiogène est généralement constituée d'au minimum une cathode, un filament, une grille de contrôle du courant (si celui ci est modulé), portés à différentes hautes tensions au travers d'un isolant haute tension comme représenté sur la figure 2c. La taille finale de la source radiogène est fortement conditionnée par la dimension de cet isolant. Compte tenu de ces contraintes de connexion et d'isolement électrique, il est très difficile d'envisager deux (ou plus) sources X dans une même enveloppe à vide. Ainsi les systèmes existants comprenant plusieurs sources X sont constitués de plusieurs tubes radiogènes distincts.To overcome the problem of current control dynamics mentioned above, devices use a polarized gate G, formed for example by son or wire, or pierced plate as shown in Figure 2a and 2b. Thus each X-ray source generally consists of at least one cathode, a filament, a current control gate (if it is modulated), brought to different high voltages through a high voltage insulator as shown in FIG. 2c. . The final size of the X-ray source is strongly influenced by the size of this insulation. Given these constraints of connection and electrical isolation, it is very difficult to consider two (or more) X sources in the same vacuum envelope. Thus existing systems comprising several sources X consist of several separate X-ray tubes.
Dans le cas des cathodes froides à émission de champ à pointes, notamment à nanotubes de carbone, dans la version la plus simple le filament et son alimentation sont supprimés comme illustré en figure 3a. Cette disposition de type diode ne permet cependant pas de contrôler l'intensité du courant émis indépendamment de la tension d'anode. En effet, la tension est fixée par l'énergie des RX recherchée, et la distance mécanique entre l'anode et la cathode est fixe, de sorte que le champ électrique au niveau du sommet des nanotubes ainsi que le courant émis sont également fixés. Une disposition avantageuse comme illustrée en figure 3b, constituée éventuellement d'un élément de focalisation F (électrostatique ou magnétique) et d'une grille d'extraction polarisée G, peut permettre de contrôler le courant.In the case of cold cathodes with spike field emission, in particular with carbon nanotubes, in the simplest version the filament and its power are removed as shown in Figure 3a. This diode-type arrangement does not, however, make it possible to control the intensity of the current emitted independently of the anode voltage. Indeed, the voltage is set by the desired RX energy, and the mechanical distance between the anode and the cathode is fixed, so that the electric field at the top of the nanotubes and the emitted current are also fixed. An advantageous arrangement as illustrated in FIG. 3b, possibly consisting of a focusing element F (electrostatic or magnetic) and a polarized extraction grid G, can make it possible to control the current.
Parmi les principaux avantages d'une cathode froide notamment à nanotubes de carbone sur une cathode thermoïonique conventionnelle, il est à noterAmong the main advantages of a cold cathode including carbon nanotubes on a conventional thermionic cathode, it should be noted
• la suppression d'un délai de préchauffage d'un filament ce qui conduit à une disponibilité immédiate en opération,• the elimination of a preheating time of a filament which leads to an immediate availability in operation,
• l'absence de vieillissement par fatigue liés aux cycles thermomécaniques rencontrés lors des séquences marche/arrêt,The absence of fatigue aging due to the thermomechanical cycles encountered during on / off sequences,
• la suppression du filament porté à haute température et de l'alimentation associée conduisant à une réduction de l'énergie consommée et à une simplification de l'alimentation• the removal of the high temperature filament and the associated power supply leading to a reduction in the energy consumed and a simplification of the power supply
• et la possibilité d'une modulation de l'émission par polarisation d'une grille d'extraction située devant la cathode à nanotubes de carbone.And the possibility of modulation of the polarization emission of an extraction grid located in front of the carbon nanotube cathode.
Pour une cathode froide, notamment à nanotubes de carbone, associée à une grille on retrouve cependant plusieurs limitations liées à la présence de la grille dans le domaine d'application des tubes radiogènes. Parmi ces limitations on peut noter que :For a cold cathode, especially with carbon nanotubes, associated with a grid, however, there are several limitations related to the presence of the grid in the field of application of the X-ray tubes. Among these limitations it can be noted that:
• la capacité cathode grille limite la fréquence maximale de modulation, • le courant émis par la cathode varie exponentiellement avec la tension appliquée sur la grille dégradant la qualité de l'asservissement du courant émis par la cathode• the gate cathode capacity limits the maximum modulation frequency, • the current emitted by the cathode varies exponentially with the voltage applied to the gate degrading the quality of the servocontrol of the current emitted by the cathode
• la grille n'étant pas intégralement transparente au flux électronique, elle intercepte de 30 à 50% du courant émis par la cathode, favorisant les variations dimensionnelles de cette grille issues de réchauffement et par voie de conséquence générant une instabilité du courant émis par la cathode du fait de la variation exponentielle décrite précédemment. L'inertie thermique et la fragilisation sont des facteurs aggravants. • La fraction de courant intercepté par la grille et réchauffement de celle ci en résultant sont également des limitations pour une utilisation de ce type de cathode à des courants élevés (quelques dizaines de mA). Par exemple pour une cathode d'un tube radiogène dont la tension serait de 15OkV pour un courant de 2 mA, une grille interceptant 40% du courant devrait dissiper 120W.The gate is not completely transparent to the electronic flux, it intercepts from 30 to 50% of the current emitted by the cathode, favoring the dimensional variations of this grid resulting from warming and consequently generating instability of the current emitted by the cathode due to the exponential variation described above. Thermal inertia and embrittlement are aggravating factors. • The fraction of current intercepted by the grid and heating thereof resulting therefrom are also limitations for use of this type of cathode at high currents (a few tens of mA). For example, for a cathode of an X-ray tube whose voltage would be 15kV for a current of 2 mA, a gate intercepting 40% of the current should dissipate 120W.
• Dans le cas de cathodes constituées d'une pluralité de pointes, ici des nanotubes, une faible inhomogenéité des caractéristiques géométriques des pointes conduit à une large distribution des champs au sommet et donc des courants émis sur l'ensemble des pointes, depuis des valeurs pouvant aller d'une émission faible jusqu'à la destruction du nanotube• In the case of cathodes constituted of a plurality of points, here nanotubes, a weak inhomogeneity of the geometric characteristics of the points leads to a wide distribution of the fields at the top and thus of the currents emitted on all the points, since values can go from a weak emission until the destruction of the nanotube
• II est par ailleurs nécessaire de disposer d'une alimentation complexe permettant de contrôler la tension de grille par rapport à la haute tension.• It is also necessary to have a complex power supply to control the gate voltage with respect to the high voltage.
Les dispositifs d'imagerie 3D sont de deux types. Dans le premier type, ils comprennent un générateur de rayons X et un détecteur en regard, permettant de mesurer le rayonnement ayant traversé l'objet ou le patient. Afin de multiplier les angles de vue, ces systèmes nécessitent la rotation de la source et du détecteur ou de l'objet ou du patient. Ces systèmes sont généralement lourds et complexes et demandent un temps d'analyse important incompatible avec les besoins nouveaux.3D imaging devices are of two types. In the first type, they comprise an X-ray generator and a detector facing each other, making it possible to measure the radiation that has passed through the object or the patient. In order to multiply the angles of view, these systems require the rotation of the source and the detector or the object or the patient. These systems are generally heavy and complex and require a significant analysis time incompatible with the new needs.
Le deuxième type autorise des techniques d'imagerie 3D sans aucun déplacement du système, ni de l'objet. Ils nécessitent plusieurs générateurs de rayonnement X et plusieurs détecteurs permettant l'observation sous différentes incidences et imposant une recombinaison des images obtenues pour en extraire l'information 3D. Ces systèmes dits de tomosynthèse sont plus simples que les précédents et peuvent permettre de réduire fortement les temps d'analyse et la complexité du système. Enfin, certains tubes radiogènes comportent en plus de la haute tension continue, un accélérateur linéaire (linac, en abrégé anglo-saxon) pour porter les électrons à très haute énergie afin de produire des rayons X eux-mêmes de très haute énergie. L'injection d'électrons dans une structure accélératrice d'un accélérateur linéaire est réalisée dans sa configuration conventionnelle à l'aide d'un canon à électrons à base de cathode à effet thermoïonique avec grille ou sans grille. L'émission électronique est contrôlée par le chauffage du filament de la cathode et/ou la polarisation de la grille de contrôle.The second type allows 3D imaging techniques without any movement of the system or the object. They require several X-ray generators and several detectors allowing the observation under different incidences and imposing a recombination of the images obtained to extract the 3D information. These so-called tomosynthesis systems are simpler than the previous ones and can greatly reduce the analysis time and the complexity of the system. Finally, some X-ray tubes include, in addition to the continuous high voltage, a linear accelerator (linac, abbreviated Anglo-Saxon) to carry the electrons at very high energy in order to produce X-rays themselves of very high energy. The injection of electrons into an accelerator structure of a linear accelerator is carried out in its conventional configuration using a cathode-based thermononic effect electron gun with grid or without grid. The electronic emission is controlled by the heating of the cathode filament and / or the polarization of the control gate.
Pour répondre notamment aux besoins de l'imagerie médicale à rayons X, le contrôle du flux de dose (Gy/s) doit être maîtrisé. Il faut donc assurer une grande stabilité de la dose émise, laquelle dépend de la régularité du courant électronique généré et de la qualité du dispositif de régulation en courant de la photocathode.In particular, to meet the needs of X-ray medical imaging, control of the dose flow (Gy / s) must be controlled. It is therefore necessary to ensure a high stability of the transmitted dose, which depends on the regularity of the generated electronic current and the quality of the photocathode current control device.
La présente invention propose en réponse une source radiogène comprenant une source froide d'électrons soumise à un champ électrique et fonctionnant par émission de champ, et un élément photoconducteur placé en série avec l'émetteur d'électrons de sorte que le courant photogénéré par illumination dans le dispositif photoconducteur est égal à celui de l'émetteur.The present invention proposes in response an X-ray source comprising a cold source of electrons subjected to an electric field and operating by field emission, and a photoconductive element placed in series with the electron emitter so that the photogenerated current by illumination in the photoconductive device is equal to that of the transmitter.
Ainsi, le courant émis est contrôlé par l'illumination, directement, et non par l'intermédiaire d'une commande en tension d'une électrode d'extraction. Cette disposition garantit une dépendance linéaire du courant d'émission avec l'illumination et un asservissement très sensible et de très bonne qualité du courant émis.Thus, the emitted current is controlled by illumination, directly, and not via a voltage control of an extraction electrode. This arrangement guarantees a linear dependence of the emission current with the illumination and a very sensitive servocontrol of very good quality of the emitted current.
Plus précisément l'invention a pour objet une source radiogène comprenant au moins une enceinte à vide, des moyens d'introduction d'une onde optique, au moins une source froide pouvant émettre des électrons dans le vide par le phénomène de l'émission de champ lorsqu'elle est soumise à un champ, au moins une alimentation fournissant une haute tension électrique, au moins une anode comprenant un matériau susceptible d'émettre des rayons X sous l'effet du bombardement électronique et au moins une fenêtre permettant la sortie des rayons X, au moins une source de lumière fournissant ladite onde optique, caractérisée en ce que la source froide comprend au moins un substrat muni d'au moins une surface conductrice, et est soumise à un champ électrique résultant de l'application de la haute tension entre au moins une surface conductrice et l'anode ; ladite source froide comprenant en outre au moins un élément photoconducteur dans lequel le courant est contrôlé par l'illumination et au moins un élément émetteur d'électrons, ledit élément photoconducteur étant électriquement connecté en série entre au moins un élément émetteur et une surface conductrice, de sorte que le courant photogénéré dans le dispositif photoconducteur est égal à celui de l'émetteur ou du groupe d 'émetteurs auquel il est associé, et de sorte que le flux de rayons X émis est sensiblement linéairement dépendant de l'illumination.More specifically, the subject of the invention is an X-ray source comprising at least one vacuum chamber, means for introducing an optical wave, at least one cold source capable of emitting electrons in a vacuum by the phenomenon of the emission of field when subjected to a field, at least one supply providing a high electrical voltage, at least one anode comprising a material capable of emitting X-rays under the effect of electronic bombardment and at least one window allowing the exit of X-rays, at least one source of light providing said optical wave, characterized in that the cold source comprises at least one substrate provided with at least one conductive surface, and is subjected to an electric field resulting from the application of the high voltage between at least one conductive surface and the anode; said cold source further comprising at least one photoconductive element in which the current is controlled by illumination and at least one electron emitting element, said photoconductive element being electrically connected in series between at least one emitter element and a conductive surface, so that the photogenerated current in the photoconductive device is equal to that of the emitter or group of emitters with which it is associated, and so that the emitted X-ray flux is substantially linearly dependent on the illumination.
Avantageusement, la source froide peut fonctionner sans grille d'extraction. Avantageusement, la source froide peut être mise ainsi à la haute tension négative, et l'anode cible à la masse électrique, simplifiant le refroidissement de l'anode cible.Advantageously, the cold source can operate without extraction grid. Advantageously, the cold source can thus be set at the high negative voltage, and the target anode at the electrical ground, simplifying the cooling of the target anode.
Avantageusement, un tel système simplifie le découplage galvanique des dispositifs de commande en courant, par l'isolation galvanique apportée par la commande optique.Advantageously, such a system simplifies the galvanic decoupling of the current control devices, by the galvanic isolation provided by the optical control.
Avantageusement, les circuits de commande peuvent être à la basse tension.Advantageously, the control circuits can be at low voltage.
Selon une variante de l'invention, la ou les surfaces conductrices, le ou les photoconducteurs et le ou les éléments émetteurs sont intégrés sur le substrat de manière monolithique et constituent ainsi une photocathode.According to a variant of the invention, the conductive surface (s), the photoconductor (s) and the emitting element (s) are integrated on the substrate in a monolithic manner and thus constitute a photocathode.
Selon une variante de l'invention, la source comporte au moins une source froide d'électrons à pointes émettrices.According to a variant of the invention, the source comprises at least one cold source of electrons with emitting points.
Selon une variante de l'invention, la source comprend une pointe émettrice pour former une source ponctuelle pour l'imagerie X, haute résolution.According to a variant of the invention, the source comprises an emitting tip for forming a point source for high resolution X-ray imaging.
On entend par là une pointe émettrice unique dont l'image nette produite par une optique électronique sur la cible X est nécessairement plus petite (sensiblement ponctuelle) que celle d'un réseau de pointes émettrices. Une image de l'objet étudié avec une telle source X sera nécessairement à plus haute résolution qu'une image obtenue avec une source X associée avec un réseau étendu de pointes.By this is meant a single emitting tip whose sharp image produced by an electronic optics on the target X is necessarily smaller (substantially punctual) than that of a network of emitting points. An image of the object studied with such a source X will necessarily be higher resolution than an image obtained with an X source associated with an extended network of points.
Selon une variante de l'invention, la source comprend au moins une source froide d'électrons à pointe émettrice en nanotube de carbone ou en nanofils métalliques.According to a variant of the invention, the source comprises at least one cold source of electron emitting tip carbon nanotube or metal nanowires.
Selon une variante de l'invention, le matériau cible du bombardement électronique est en tungstène ou en composite comportant du tungstène ou tout autre matériau réfractaire à Z élevé.According to a variant of the invention, the target material of the electron bombardment is tungsten or composite comprising tungsten or other high Z refractory material.
Par dispositif photoconducteur, on entend dispositif dont l'état de conduction est contrôlé par l'illumination.By photoconductive device is meant device whose conduction state is controlled by illumination.
Selon une variante de l'invention, le dispositif photoconducteur est de type photodiode en semiconducteur à structure PIN ou P désigne une zone dopée P, I désigne une zone intrinsèque ou non intentionnellement dopée ou peu dopée, et N une zone dopée N. Selon une variante de l'invention, le dispositif photoconducteur est une diode MIN ou M désigne une zone métallique,According to one variant of the invention, the photoconductive device is of the semiconductor photodiode type with a PIN structure where P denotes a P doped zone, I designates an intrinsic or unintentionally doped or slightly doped zone, and N denotes an N doped zone. variant of the invention, the photoconductive device is a MIN diode or M denotes a metal zone,
Selon une variante de l'invention, l'élément photoconducteur comprend une couche métallique à au moins une de ses faces de contact.According to a variant of the invention, the photoconductive element comprises a metal layer with at least one of its contact faces.
Selon une variante de l'invention, la source froide comprend au moins un substrat conducteur comportant au moins un émetteur d'électrons et un dispositif photoconducteur de manière à former au moins une photocathode.According to a variant of the invention, the cold source comprises at least one conductive substrate comprising at least one electron emitter and a photoconductive device so as to form at least one photocathode.
Selon une variante de l'invention, la source froide comprend au moins un substrat conducteur au moins une pointe dont le sommet est à une hauteur h par rapport au substrat conducteur et au moins un élément photoconducteur disposé entre la pointe et le substrat conducteur telle que la pointe soit éloignée de ses éventuelles voisines d'une distance d sensiblement égale ou supérieure deux fois la hauteur h, et telle que les dimensions latérales phi des éléments photoconducteurs soient environ égales ou inférieure la hauteur h.According to a variant of the invention, the cold source comprises at least one conducting substrate at least one point whose apex is at a height h with respect to the conductive substrate and at least one photoconductive element disposed between the tip and the conductive substrate such that the tip is remote from its possible neighbors by a distance d substantially equal to or greater than twice the height h, and such that the lateral dimensions phi of the photoconductive elements are approximately equal to or less than the height h.
Selon une variante, les émetteurs ou groupes d'émetteurs sont disposés en réseaux réguliers. Selon une variante de l'invention, le substrat comprend une face dite avant supportant l'élément émetteur, la source de lumière éclairant ladite face avant. Selon une variante de l'invention, le substrat est transparent à ladite source de lumière, ladite source de lumière éclairant ledit substrat en face opposée à la face avant.According to one variant, the emitters or groups of emitters are arranged in regular networks. According to a variant of the invention, the substrate comprises a so-called front face supporting the emitter element, the light source illuminating said front face. According to a variant of the invention, the substrate is transparent to said light source, said light source illuminating said substrate opposite to the front face.
Selon une variante de l'invention, le substrat présente une zone amincie destinée à être illuminée, de manière à minimiser les phénomènes d'absorption ladite source de lumière éclairant ledit substrat en face opposée à la face avant.According to a variant of the invention, the substrate has a thinned zone intended to be illuminated, so as to minimize the phenomena of absorption, said source of light illuminating said substrate opposite to the front face.
Avantageusement, la source radiogène comporte en outre des moyens de réglage de la puissance optique de la source de lumière pour régler la puissance de rayons X générés. Elle peut aussi avantageusement comprendre des moyens pour régler la focalisation de la source de lumière sur la source d'électrons.Advantageously, the X-ray source further comprises means for adjusting the optical power of the light source to adjust the power of X-rays generated. It can also advantageously include means for adjusting the focus of the light source on the electron source.
Selon une variante de l'invention, la source comprend un monotube X de symétrie cylindrique comportant une enceinte, renfermant une photocathode, une cible, un miroir permettant d'illuminer la photocathode avec un faisceau lumineux perpendiculaire à l'axe du mono-tube issu de la source d'illumination, et une fenêtre optique permettant de recueillir l'émission X.According to a variant of the invention, the source comprises a monotube X of cylindrical symmetry comprising an enclosure, enclosing a photocathode, a target, a mirror for illuminating the photocathode with a light beam perpendicular to the axis of the mono-tube from of the illumination source, and an optical window for collecting the emission X.
Selon une variante de l'invention, la source radiogène comprend plusieurs mono-tubes X, un support circulaire supportant lesdits mono-tubes X disposés radialement, une alimentation haute tension, des moyens de distribution de ladite alimentation haute tension sur les différents mono-tubes de manière à produire des faisceaux de rayons X, et des moyens individuels de contrôles optiques indépendants dédiés à chacun des mono-tubes.According to a variant of the invention, the X-ray source comprises several single-tubes X, a circular support supporting said radially arranged mono-tubes X, a high-voltage power supply, distribution means of said high-voltage power supply on the different single-tubes. in order to produce X-ray beams, and individual independent optical control means dedicated to each of the single-tubes.
Selon une variante de l'invention, lesdits faisceaux de contrôle optique et les faisceaux de rayons X sont tous parallèles entre eux et perpendiculaires audit support circulaire.According to a variant of the invention, said optical control beams and the X-ray beams are all parallel to each other and perpendicular to said circular support.
Selon une autre variante de l'invention, la source radiogène comprend en outre des moyens pour faire converger lesdits faisceaux de rayons X. Selon une variante de l'invention, la source radiogène comprend une enceinte, plusieurs ensembles constitués chacun d'un couple constitué d'une photocathode associée à une cible et des moyens de distribution d'alimentation desdites photocathodes. Selon une variante, l'enceinte présente une forme concave de manière à générer des faisceaux de rayons X convergents.According to another variant of the invention, the X-ray source further comprises means for converging said X-ray beams. According to a variant of the invention, the X-ray source comprises an enclosure, several assemblies each consisting of a pair consisting of a photocathode associated with a target and power distribution means of said photocathodes. According to one variant, the enclosure has a concave shape so as to generate convergent X-ray beams.
Selon une variante de l'invention, la source radiogène comporte :According to a variant of the invention, the X-ray source comprises:
- une photocathode dite étendue ou un ensemble de photocathodes ; - une cible dite étendue ou un ensemble de cibles, en regard respectivement de ladite photocathode étendue ou de l'ensemble de photocathodes;an extended photocathode or a set of photocathodes; a so-called extended target or set of targets respectively facing said extended photocathode or the set of photocathodes;
- un dispositif d'adressage de l'illumination d'une photocathode étendue ou d'un ensemble de photocathodes, de manière à sélectionner différentes zones au cours du temps sur la photocathode étendue ou à sélectionner différentes photocathodes dans l'ensemble de photocathodes et corrélativement rendre les zones de la cible étendue ou d'une cible parmi l'ensemble de cible, émettrice de rayons X. Selon une variante de l'invention, la source comprend un modulateur spatial et/ou temporel permettant de défléchir un faisceau issu de la source d'illumination, vers différentes zones de la photocathode étendue ou différentes photocathodes parmi un ensemble de photocathodes.a device for addressing the illumination of an extended photocathode or of a set of photocathodes, so as to select different zones over time on the extended photocathode or to select different photocathodes in the set of photocathodes and correlatively rendering the areas of the extended target or of a target among the X-ray transmitting target assembly. According to a variant of the invention, the source comprises a spatial and / or temporal modulator making it possible to deflect a beam originating from the illumination source, to different areas of the extended photocathode or different photocathodes among a set of photocathodes.
Selon une variante de l'invention, le dispositif d'adressage est un modulateur spatial de lumière éclairé par un faisceau étendu permettant de transférer différentes lois d'éclairement sur une zone de la photocathode étendue ou sur une photocathode dans l'ensemble de photocathodes, et d'obtenir les lois correspondantes d'émission de rayons X depuis une zone de cible étendue ou sur une cible de l'ensemble de cibles. Selon une variante de l'invention, la source comprend un ensemble de sources d'illumination et est caractérisée en ce que le dispositif d'adressage est un déflecteur opto-mécanique ou opto-électrique et active des sources d'illumination associées de manière biunivoque à différentes zones de la photocathode étendue ou à différentes photocathodes de l'ensemble de photocathodes, lesdites zones ou photocathodes étant associées de manière biunivoque à différentes zones de la cible étendue ou à différentes cibles parmi l'ensemble de cibles.According to a variant of the invention, the addressing device is a spatial light modulator illuminated by an extended beam for transferring different illumination laws to an area of the extended photocathode or a photocathode in the set of photocathodes, and obtaining the corresponding X-ray emission laws from an extended target area or target of the set of targets. According to a variant of the invention, the source comprises a set of illumination sources and is characterized in that the addressing device is an opto-mechanical or opto-electric deflector and activates illumination sources associated in a one-to-one manner. to different areas of the extended photocathode or to different photocathodes in the set of photocathodes, said zones or photocathodes being associated one-to-one with different areas of the extended target or with different targets in the set of targets.
Selon une variante de l'invention, la distribution de puissance lumineuse est réalisée au moins pour partie par propagation guidée (fibres optiques) au lieu de propagation spatiale.According to a variant of the invention, the light power distribution is carried out at least partly by guided propagation (optical fibers) instead of spatial propagation.
Selon une variante de l'invention, l'enceinte à vide comporte des passages pour les fibres optiquesAccording to a variant of the invention, the vacuum chamber comprises passages for the optical fibers
Selon une variante de l'invention, les modulateurs spatiaux sont de type à propagation guidée. Une ou plusieurs des variantes ci-dessus peuvent être complétées et formulées comme ci-dessous :According to a variant of the invention, the spatial modulators are of guided propagation type. One or more of the above variants can be completed and formulated as below:
Selon une variante de l'invention, la source radiogène comprend une enceinte à vide, et au moins un triplet composé coaxialement et consécutivement : - d'une fenêtre transparente aux photons d'une photocathode polarisée à la haute tension négative d'une cible et les moyens d'alimentation électrique de ces éléments. Selon une variante de l'invention, la source radiogène prévoit une disposition des triplets de telle sorte qu'ils génèrent des faisceaux X spatialement convergents.According to a variant of the invention, the X-ray source comprises a vacuum chamber, and at least one compound triplet coaxially and consecutively: a photon-transparent window of a photocathode polarized at the negative high voltage of a target and the power supply means of these elements. According to a variant of the invention, the X-ray source provides an arrangement of the triplets so that they generate spatially convergent X-beams.
Selon une variante de l'invention, la source radiogène prévoit une disposition des triplets de telle sorte qu'ils génèrent des faisceaux X parallèles et organisés matriciellement. Selon une variante de l'invention, la source radiogène prévoit une disposition des triplets de telle sorte qu'ils génèrent des faisceaux X parallèles et organisés circulairement.According to a variant of the invention, the X-ray source provides an arrangement of the triplets so that they generate parallel X-beams organized in a matrix manner. According to a variant of the invention, the X-ray source provides an arrangement of the triplets so that they generate parallel X-beams and organized circularly.
Selon une variante de l'invention, la source radiogène prévoit une disposition des triplets de telle sorte qu'ils génèrent des groupes parallèles de faisceaux X, ces groupes étant perpendiculaires les uns aux autres.According to a variant of the invention, the X-ray source provides an arrangement of the triplets so that they generate parallel groups of X-beams, these groups being perpendicular to each other.
Selon une variante de l'invention, la source radiogène comporte en outre au moins un accélérateur linéaire pour accélérer les électrons émis par la source d'électrons. Parmi les différents avantages de l'invention, on peut citer les suivants : l'éclairement appliqué permet un asservissement unitaire du courant de chaque émetteur évitant ainsi les risques de destruction de ces émetteurs liés aux différences de hauteur des nanotubes et qu'on rencontre dans le cas d'un pilotage par une électrode ou plan conducteur dont on fait varier la tension.According to a variant of the invention, the X-ray source further comprises at least one linear accelerator for accelerating the electrons emitted by the electron source. Among the various advantages of the invention, the following may be mentioned: the applied illumination allows a unit control of the current of each emitter avoiding the risks of destruction of these emitters related to differences in the height of the nanotubes and which are encountered in the case of control by an electrode or conductive plane whose voltage is varied.
Aucun groupe émissif (emitter array) n'a lieu d'être défini structurellement comme dans le cas d'un pilotage par une électrode ou plan conducteur dont on fait varier la tension, autorisant ainsi toutes définitions possibles des zones émissives engageant au moins une photocathode.No emitter array has to be defined structurally, as in the case of control by an electrode or conductive plane whose voltage is varied, thus allowing any possible definitions of the emitting zones engaging at least one photocathode .
L'invention sera mieux comprise et d'autres avantages apparaîtront à la lecture de la description qui va suivre donnée à titre non limitatif et grâce aux figures annexées parmi lesquelles :The invention will be better understood and other advantages will become apparent on reading the description which follows given by way of non-limiting example and by virtue of the appended figures among which:
- les figures 1 a, 1 b illustrent des exemples de cathodes thermoioniques de l'art connu ;FIGS. 1a, 1b illustrate examples of thermionic cathodes of the known art;
- les figures 2a, 2b, 2c illustrent des exemples de cathodes thermoioniques de l'art connu comportant en outre une grille intermédiaire ;FIGS. 2a, 2b and 2c illustrate examples of thermionic cathodes of the known art further comprising an intermediate gate;
- les figures 3a et 3b illustrent des exemples de cathodes froides selon l'art connu ;FIGS. 3a and 3b illustrate examples of cold cathodes according to the known art;
- la figure 4 illustre un principe de source radiogène selon l'invention ; - la figure 5 schématise une source radiogène selon l'invention relative à un monotube X de symétrie cylindrique ;FIG. 4 illustrates a principle of X-ray source according to the invention; FIG. 5 schematizes an X-ray source according to the invention relating to a monotube X of cylindrical symmetry;
- les figures 6a et 6b illustrent un autre exemple de source radiogène selon l'invention relatif à plusieurs monotubes X disposés radialement ; - les figures 7a, 7b, 7c et 7d illustrent un autre exemple de source radiogène selon l'invention, relatif à une enceinte renfermant plusieurs sources disposées diversement ;FIGS. 6a and 6b illustrate another example of an X-ray source according to the invention relating to several radially arranged monotubes X; FIGS. 7a, 7b, 7c and 7d illustrate another example of an X-ray source according to the invention, relating to an enclosure enclosing a plurality of sources arranged differently;
- la figure 8 présente un exemple de modulation du spot électronique sur la cible uniquement lié à la zone d'éclairement (pas de grille ni « emitter array » déterminant mécaniquement les zones d'émission);FIG. 8 shows an example of modulation of the electronic spot on the target only related to the zone of illumination (no grid or "emitter array" mechanically determining the emission zones);
- les figures 9a et 9b illustrent la différence de réponse en courant de l'émetteur (exponentielle en présence d'une grille de commande, linéaire en présence d'une photocathode selon l'invention) ;FIGS. 9a and 9b illustrate the difference in current response of the transmitter (exponential in the presence of a control gate, linear in the presence of a photocathode according to the invention);
- les figures 10a et 10b illustrent la capacité d'activer des zones émissives locales irradiant une cible étendue ;FIGS. 10a and 10b illustrate the ability to activate local emissive zones radiating an extended target;
- la figure 11 a présente un schéma de principe de l'invention, les figures 11 b, 11 c, 11d, précisent des variantes de configurations de photocathodes intégrées.FIG. 11 a presents a schematic diagram of the invention, FIGS. 11b, 11c, 11d, specify alternative configurations of integrated photocathodes.
De manière générale, l'invention propose la mise en œuvre dans une même source radiogène, d'une ou plusieurs cathodes froides dont rémission est contrôlée par un dispositif photoconducteur, ce type de dispositif peut typiquement être de type tel que celui décrit dans le brevet N°In general, the invention proposes the implementation in the same X-ray source, one or more cold cathodes whose remission is controlled by a photoconductive device, this type of device can typically be of type such as that described in the patent No.
04 13340.04 13340.
Ainsi de manière schématique illustrée en figure 4, la source radiogène de l'invention comporte au moins un dispositif photoconducteur de commande 10, une source d'électrons 11 venant irradier une cible 12 de façon à ce que cette dernière émette un faisceau de rayons X, 13.Thus schematically illustrated in FIG. 4, the X-ray source of the invention comprises at least one photoconductive control device 10, an electron source 11 that irradiates a target 12 so that the latter emits an X-ray beam , 13.
Ce type de découplage optique permet d'envisager des configurations de sources multiples dans une même enceinte à vide, localisées ou spatialement réparties et produisant un rayonnement X continue ou modulé temporellement suivant l'éclairement de la photo cathode.This type of optical decoupling makes it possible to envisage multiple source configurations in the same vacuum chamber, localized or spatially distributed and producing a continuous X-ray or modulated temporally according to the illumination of the photo cathode.
Nous allons décrire ci-après des exemples de réalisation de sources radiogènes selon l'invention.We will describe below examples of embodiments of X-ray sources according to the invention.
Premier exemple de réalisation :First example of realization:
Selon une première variante de l'invention, illustrée en figure 5, la source radiogène est une source mono-faisceau et comporte une enceinte sous-vide 20, des moyens d'alimentation haute tension 21 et des moyens d'isolation électrique 22, une source d'illumination 23 dirigeant un faisceau lumineux 24 en direction d'un dispositif optiquement réfléchissant 25 pour les longueurs d'onde utilisée s afin d'exciter les couches photo-sensibles d'une cathode 26 permettant de générer un flux d'électrons 27, en direction d'une cible 28. Le bombardement de ladite cible génère alors le flux de rayons X, 30 au travers d'une fenêtre 29 transparente auxdits rayons X dont est équipée l'enceinte. Avantageusement l'enceinte peut également être équipée de moyens de refroidissement 31 de la cible soumise à des échauffements intenses lors des opérations de bombardement par les flux d'électrons.According to a first variant of the invention, illustrated in FIG. 5, the X-ray source is a single-beam source and comprises a vacuum enclosure 20, high-voltage supply means 21 and means electrical insulation 22, an illumination source 23 directing a light beam 24 towards an optically reflective device 25 for the wavelengths used to excite the light-sensitive layers of a cathode 26 enabling generating a stream of electrons 27, towards a target 28. The bombardment of said target then generates the X-ray flux, 30 through a window 29 transparent to said X-rays which the enclosure is equipped with. Advantageously, the enclosure may also be equipped with cooling means 31 for the target subjected to intense heating during the bombardment operations by the electron flows.
Deuxième exemple de réalisation :Second example of realization:
La source radiogène comporte une multiplicité de flux de rayonsThe X-ray source has a multiplicity of ray fluxes
X, 4Oi, grâce à la présence d'une série d'enceintes (tubes à rayons X) 41 i distribuées dans un support circulaire 42, ledit support circulaire comporte en outre des moyens de distribution d'une alimentation haute tension 43 comme illustré en figure 6a et 6b.X, 40i, thanks to the presence of a series of enclosures (X-ray tubes) 41 i distributed in a circular support 42, said circular support further comprises means for distributing a high-voltage power supply 43 as illustrated in FIG. Figure 6a and 6b.
Troisième exemple de réalisation :Third embodiment:
La source radiogène peut également être multi-faisceaux et comprendre une enceinte unique comme illustré en figure 7a, 7b, 7c, 7d. Selon l'exemple représenté, ladite enceinte 50 peut avantageusement se présenter sous plusieurs formes intégrant des sources d'électrons disposés diversement. Les exemples non exhaustifs montrent une organisation convergente planaire (figure 7a), parallèle organisée circulairement (figure 7b), parallèle organisée perpendiculairement (figure 7c), parallèle organisée matriciellement (figure 7d).The X-ray source may also be multi-beam and include a single enclosure as shown in Figure 7a, 7b, 7c, 7d. According to the example shown, said enclosure 50 may advantageously be in several forms integrating electron sources arranged differently. The non-exhaustive examples show a planar convergent organization (FIG. 7a), parallel organized circularly (FIG. 7b), parallel organized perpendicularly (FIG. 7c), parallel organized in a matrix manner (FIG. 7d).
La figure 8 illustre présente un exemple de moyens de modulation du spot électronique sur la cible uniquement lié à la zone d'éclairement (pas de grille ni « emitter array » déterminant mécaniquement les zones d'émission). De manière générale, la présente invention propose en réponse une source radiogène comprenant une source froide d'électrons soumise à un champ électrique et fonctionnant par émission de champ, et un élément photoconducteur placé en série avec l'émetteur d'électrons de sorte que le courant photogénéré par illumination dans le dispositif photoconducteur est égal à celui de l'émetteur.FIG. 8 illustrates an example of means for modulating the electronic spot on the target only linked to the illumination zone (no grid or "emitter array" mechanically determining the emission zones). In general, the present invention proposes in response an X-ray source comprising an electrically-field-fed cold-field source operating by field emission, and a photoconductive element placed in series with the electron-emitter so that the photogenerated current by illumination in the photoconductive device is equal to that of the transmitter.
Ainsi, le courant émis est contrôlé par l'illumination, directement, et non par l'intermédiaire d'une commande en tension d'une électrode d'extraction. Cette disposition garantit une dépendance linéaire du courant d'émission avec l'illumination et un asservissement très sensible et de très bonne qualité du courant émis.Thus, the emitted current is controlled by illumination, directly, and not via a voltage control of an extraction electrode. This arrangement guarantees a linear dependence of the emission current with the illumination and a very sensitive servocontrol of very good quality of the emitted current.
Les figures 9a et 9b illustrent la différence de réponse en courant de l'émetteur. Ainsi cette réponse est exponentielle en présence d'une grille de commande, et linéaire en présence d'une photocathode selon l'invention.Figures 9a and 9b illustrate the difference in current response of the transmitter. Thus this response is exponential in the presence of a control gate, and linear in the presence of a photocathode according to the invention.
Quatrième exemple de réalisation :Fourth example of realization:
Les exemples précédemment décrits sont relatifs à des sources radiogènes multi-faisceaux comportant un ensemble de sources d'électrons élémentaires associées à des cibles élémentaires.The previously described examples relate to multi-beam X-ray sources comprising a set of elementary electron sources associated with elementary targets.
Selon l'invention, la source radiogène multi-faisceaux peut également comprendre une source d'électrons étendue, comportant des zones d'émission d'électrons, capables d'irradier une cible étendue pour générer des faisceaux de rayons X (comme illustré en figures 10a et 10b). Ce type de source associée à des moyens de balayage peut typiquement être utilisée pour une configuration d'imagerie telle que la fluoroscopie par exemple.According to the invention, the multi-beam X-ray source may also comprise an extended electron source, comprising electron emission zones, capable of irradiating an extended target to generate X-ray beams (as illustrated in FIGS. 10a and 10b). This type of source associated with scanning means can typically be used for an imaging configuration such as fluoroscopy for example.
Afin d'éviter les rayons diffusés, on peut être amené à privilégier un balayage rapide réalisé soit par un diaphragme mobile, soit suivant un dispositif de balayage par déviateurs électrostatiques ou magnétiques comme décrit dans le Brevet N° 00 08320 De P. De Groot « Générateur de rayons X à balayage pour système d'imagerie susceptible de fonctionner à grande vitesse » du 29 06 1999. Cinquième exemple de réalisation :In order to avoid scattered rays, it may be necessary to favor a fast sweep performed either by a movable diaphragm, or following a scanning device by electrostatic or magnetic deflectors as described in Patent No. 00 08320 De P. De Groot " Scanning X-ray Generator for High Speed Imaging System "of 29.06.1999. Fifth example of realization:
La source radiogène est une source micro-foyer ou nano-foyer comportant des moyens optiques assurant une focalisation telle qu'un seul nanotube soit adressé pour générer un faisceau d'électrons. La cible irradiée par un seul nanotube fournit par voie de conséquence également un faisceau de rayons X de tache focale très petite. Le diamètre du spot de la micro ou nano source X peut être ajusté suivant la surface de la zone éclairée et ainsi permettre d'asservir le diamètre du spot en fonction de la densité de puissance admissible sur la cible. Eventuellement, un système de focalisation, magnétique ou électrostatique peut être utilisé pour concentrer sur la cible tous les électrons émis par l'extrémité du nanotube dans une tache thermique de taille comparable à celle de la surface émissive, soit de l'ordre de 10 à 100 nm de diamètre. Ce type de source radiogène peut notamment avantageusement assurer l'accès à du contrôle non destructif de grille de transistor de circuit intégré, par exemple.The X-ray source is a micro-focus or nano-focus source comprising optical means providing a focus such that a single nanotube is addressed to generate an electron beam. The target irradiated with a single nanotube consequently also provides a very small focal spot x-ray beam. The diameter of the spot of the micro or nano source X can be adjusted according to the surface of the illuminated area and thus allow to enslave the spot diameter according to the power density on the target. Optionally, a focusing system, magnetic or electrostatic may be used to focus on the target all the electrons emitted by the end of the nanotube in a thermal spot of size comparable to that of the emitting surface, being of the order of 10 to 100 nm in diameter. This type of X-ray source can advantageously provide access to non-destructive control of integrated circuit transistor gate, for example.
Sixième exemple de réalisation :Sixth example:
Les exemples précédemment décrits sont relatifs à des sources radiogènes comportant une haute tension comme moyen d'accélération des électrons. Selon l'invention, la source radiogène peut également comporter une structure accélératrice dite « linac ». associée à la source froide, un dispositif photoélectrique permettant le contrôle de l'émission d'électrons par la source froide, et une source de lumière pour commander par illumination ledit dispositif photoélectrique. Dans ce cas, l'association permet une simplification de l'accélérateur, une réduction de son volume et une amélioration de la qualité du faisceau d'électrons et du rayonnement X qu'il produit.The previously described examples relate to X-ray sources comprising a high voltage as electron acceleration means. According to the invention, the X-ray source may also comprise an accelerator structure called "linac". associated with the cold source, a photoelectric device for controlling the emission of electrons by the cold source, and a light source for controlling by illumination said photoelectric device. In this case, the combination allows a simplification of the accelerator, a reduction in its volume and an improvement in the quality of the electron beam and the X-radiation it produces.
Les avantages spécifiques produits sont les suivants : - une modulation temporelle initiale du faisceau à la fréquence de l'accélérateur, avec une extension en phase permettant un rendement en courant proche de 100%. La totalité du courant ainsi émis en impulsions courtes, permet une acceptance en phase maximale par l'onde hyperfréquence, sans pertes longitudinales ;The specific advantages produced are as follows: an initial temporal modulation of the beam at the frequency of the accelerator, with an extension in phase allowing a current efficiency close to 100%. The totality of the current thus emitted in pulses short, allows maximum phase acceptance by the microwave, without longitudinal losses;
- une réduction des pertes électroniques et donc thermiques dans le linac ; - les paquets d'électrons étant déjà produits à l'émission, la totalité des cellules de l'accélérateur est consacrée à l'accélération proprement dite du faisceau et non à une phase préliminaire de prégroupement, amenant à une simplification de la géométrie du linac, et à une réduction de sa longueur. Ainsi, les premières cavités de l'accélérateur, conventiellement dédiées à la mise en forme temporelle du faisceau peuvent être simplifiées ;- a reduction of electronic and therefore thermal losses in the linac; since the electron packets are already produced on transmission, all the cells of the accelerator are devoted to the actual acceleration of the beam and not to a preliminary pre-assembly phase, leading to a simplification of the geometry of the linac. , and a reduction in its length. Thus, the first cavities of the accelerator, conventionally dedicated to the temporal shaping of the beam can be simplified;
- la miniaturisation du canon, ainsi que la possibilité d'une commande du courant à haute fréquence permet son adaptation à des linacs à très haute fréquence (par exemple bande X) ;- The miniaturization of the barrel, as well as the possibility of a control of the high frequency current allows its adaptation to very high frequency linacs (for example X band);
- la courte extension en phase des paquets d'électrons produits permet de réduire la dispersion en énergie finale du faisceau ;the short phase extension of the electron packets produced makes it possible to reduce the dispersion in final energy of the beam;
- avec une faible dispersion en énergie, le faisceau est aisément focalisé en sortie de l'accélérateur, permettant des sources très ponctuelles de rayonnement sur la cible de conversion ;with a low energy dispersion, the beam is easily focused at the output of the accelerator, allowing very specific sources of radiation on the conversion target;
- l'absence d'un système de cavités de prégroupement et groupement, permet d'envisager des linacs de basse énergie (en dessous de- the absence of a system of pre-grouping and grouping cavities, makes it possible to envisage low-energy linacs (below
4 MeV) avec une bonne qualité du faisceau ;4 MeV) with good beam quality;
- le contrôle du courant initial puise à puise, permet d'envisager des linacs à courant variable dans des applications multi-énergies puise à puise où une puissance faisceau constante serait nécessaire pour la qualité du rayonnement X et de l'imagerie associée.- the control of the initial current draws from draws, makes it possible to envisage linacs with variable current in applications multi-energies draws with draw where a constant beam power would be necessary for the quality of the X-ray radiation and the associated imagery.
Les figures 11 a, 11 b, 11 c et 11 d illustrent de manière détaillée un exemple de source radiogène de l'invention.Figures 11a, 11b, 11c and 11d illustrate in detail an example of an X-ray source of the invention.
Plus précisément cette source radiogène comprend une enceinte à vide 50, des moyens 56h d'introduction d'une onde optique 56i, une source froide 52 pouvant émettre des électrons 52i dans le vide par le phénomène de l'émission de champ lorsqu'elle est soumise à un champ, une alimentation 55 fournissant une haute tension électrique, une anode 53 comprenant un matériau 53j susceptible d'émettre des rayons X, 53i sous l'effet du bombardement électronique et au moins une fenêtre 54 permettant la sortie de rayons X, au moins une source de lumière 56 fournissant ladite onde optique.More precisely, this X-ray source comprises a vacuum chamber 50, means 56h for introducing an optical wave 56i, a cold source 52 capable of emitting electrons 52i in a vacuum by the phenomenon of field emission when it is subjected to a field, a power supply 55 providing a high electrical voltage, an anode 53 comprising a material 53j capable of emitting X-rays, 53i under the effect of electronic bombardment and at least one window 54 enabling the X-ray output, at least one light source 56 providing said optical wave.
La source froide comprend également au moins un substrat 57 muni d'au moins une surface conductrice 55, et est soumise à un champ électrique résultant de l'application de la haute tension entre au moins une surface conductrice 55 et l'anode 53; ladite source froide comprenant en outre au moins un élément photoconducteur 58 dans lequel le courant est contrôlé sensiblement linéairement par l'illumination et au moins un élément émetteur d'électrons 59, ledit élément photoconducteur 58 étant électriquement connecté en série entre au moins un élément émetteur 59 et une surface conductrice 55, de sorte que le courant photogénéré dans le dispositif photoconducteur est égal à celui émis par l'émetteur ou le groupe d 'émetteurs auquel il est associé, et de sorte que le flux de rayons X émis est sensiblement linéairement dépendant de l'illumination. The cold source also comprises at least one substrate 57 provided with at least one conductive surface 55, and is subjected to an electric field resulting from the application of the high voltage between at least one conductive surface 55 and the anode 53; said cold source further comprising at least one photoconductive element 58 in which the current is controlled substantially linearly by the illumination and at least one electron emitting element 59, said photoconductive element 58 being electrically connected in series between at least one transmitting element 59 and a conductive surface 55, so that the photogenerated current in the photoconductive device is equal to that emitted by the emitter or group of emitters with which it is associated, and so that the emitted X-ray flux is substantially linearly depending on the illumination.

Claims

REVENDICATIONS
1 . Source radiogène comprenant une enceinte à vide (50), des moyens (56h) d'introduction d'une onde optique (56i), une source froide (52) pouvant émettre des électrons (52i) dans le vide par le phénomène de l'émission de champ lorsqu'elle est soumise à un champ, une alimentation (55) fournissant une haute tension électrique, une anode (53) comprenant un matériau (53j) susceptible d'émettre des rayons X (53i) sous l'effet du bombardement électronique et au moins une fenêtre (54) permettant la sortie de rayons X, au moins une source de lumière (56) fournissant ladite onde optique, caractérisée en ce que la source froide comprend au moins un substrat (57) muni d'au moins une surface conductrice (55), et est soumise à un champ électrique résultant de l'application de la haute tension entre au moins une surface conductrice (55) et l'anode (53); ladite source froide comprenant en outre au moins un élément photoconducteur (58) dans lequel le courant est contrôlé sensiblement linéairement par l'illumination et au moins un élément émetteur d'électrons (59), ledit élément photoconducteur (58) étant électriquement connecté en série entre au moins un élément émetteur (59) et une surface conductrice (55), de sorte que le courant photogénéré dans le dispositif photoconducteur est égal à celui émis par l'émetteur ou le groupe d 'émetteurs auquel il est associé, et de sorte que le flux de rayons X émis est sensiblement linéairement dépendant de l'illumination.1. X-ray source comprising a vacuum chamber (50), means (56h) for introducing an optical wave (56i), a cold source (52) capable of emitting electrons (52i) in the vacuum by the phenomenon of the field emission when subjected to a field, a power supply (55) providing a high electrical voltage, an anode (53) comprising a material (53j) capable of emitting X-rays (53i) under the effect of the bombardment and at least one window (54) providing X-ray output, at least one light source (56) providing said optical wave, characterized in that the cold source comprises at least one substrate (57) provided with at least one a conductive surface (55), and is subjected to an electric field resulting from the application of the high voltage between at least one conductive surface (55) and the anode (53); said cold source further comprising at least one photoconductive element (58) in which the current is controlled substantially linearly by the illumination and at least one electron emitting element (59), said photoconductive element (58) being electrically connected in series between at least one emitting element (59) and a conductive surface (55), so that the photogenerating current in the photoconductive device is equal to that emitted by the emitter or emitter group with which it is associated, and so that the X-ray flux emitted is substantially linearly dependent on the illumination.
2. Source radiogène selon la revendication 1 , caractérisée en ce que l'anode portant la cible est à la masse électrique, et la source froide est à la haute tension négative.2. X-ray source according to claim 1, characterized in that the anode carrying the target is at the electrical ground, and the cold source is at the high negative voltage.
3. Source radiogène selon l'une des revendications 1 ou 2, caractérisée en ce que la ou les surfaces conductrices, le ou les photoconducteurs et le ou les éléments émetteurs sont intégrés sur le substrat de manière monolithique. 3. X-ray source according to one of claims 1 or 2, characterized in that the conductive surface (s), the photoconductor (s) and the emitting element (s) are integrated on the substrate in a monolithic manner.
4. Source radiogène selon l'une des revendications 1 à 3, caractérisée en ce qu'au moins une source froide d'électrons est à pointes émettrices.4. X-ray source according to one of claims 1 to 3, characterized in that at least one cold source of electrons is emitting points.
5. Source radiogène selon la revendication 4, caractérisée en ce qu'elle comprend une pointe émettrice pour former une source à rayons X ponctuelle pour l'imagerie X, haute résolution.5. X-ray source according to claim 4, characterized in that it comprises an emitting tip to form a point X-ray source for X-ray imaging, high resolution.
6. Source radiogène selon l'une des revendications 1 à 4, caractérisée en ce que la source froide comprend au moins un substrat conducteur au moins une pointe dont le sommet est à une hauteur h par rapport au substrat conducteur et au moins un élément photoconducteur disposé entre la pointe et le substrat conducteur telle que la pointe soit éloignée de ses éventuelles voisines d'une distance d sensiblement égale ou supérieure deux fois la hauteur h, et telle que les dimensions latérales phi des éléments photoconducteurs soient environ égales ou inférieure la hauteur h.6. X-ray source according to one of claims 1 to 4, characterized in that the cold source comprises at least one conductive substrate at least one tip whose apex is at a height h relative to the conductive substrate and at least one photoconductive element disposed between the tip and the conductive substrate such that the tip is spaced from its possible neighbors by a distance d substantially equal to or greater than twice the height h, and such that the lateral dimensions phi of the photoconductive elements are approximately equal to or less than the height; h.
7. Source radiogène selon l'une des revendications 4 ou 6, caractérisée en ce que, les émetteurs ou groupes d'émetteurs sont disposés en réseaux réguliers.7. X-ray source according to one of claims 4 or 6, characterized in that the emitters or groups of emitters are arranged in regular networks.
8. Source radiogène selon l'une des revendications 1 à 7, caractérisée en ce qu'au moins une source froide d'électrons est à pointe émettrice en nanotube de carbone ou en nanofils métalliques.8. X-ray source according to one of claims 1 to 7, characterized in that at least one cold source of electrons is emitting tip carbon nanotube or metal nanowires.
9. Source radiogène selon l'une des revendications 1 à 8, caractérisée en ce que la cible est un matériau comportant du tungstène, ou tout autre matériau réfractaire à Z élevé.9. X-ray source according to one of claims 1 to 8, characterized in that the target is a material comprising tungsten, or any other high Z refractory material.
10. Source radiogène selon l'une des revendications 1 à 9, caractérisée en ce que la cible et la fenêtre permettant la sortie des rayons X sont confondues. 10. X-ray source according to one of claims 1 to 9, characterized in that the target and the window for the output of X-rays are combined.
11. Source radiogène selon l'une des revendications 1 à 10, caractérisée en ce qu'au moins un dispositif photoélectrique photoconducteur est de type photodiode en semiconducteur à structure PIN où I désigne une zone intrinsèque ou non intentionnellement dopée ou faiblement dopée de type N" ou P" 11. X-ray source according to one of Claims 1 to 10, characterized in that at least one photoconductive photoelectric device is of the PIN-structured semiconductor photodiode type, where I denotes an intrinsic or non-intentionally doped or slightly doped N-type zone. " or P "
12. Source radiogène selon l'une des revendications 1 à 10, caractérisée en ce que le dispositif photoconducteur est une diode MIN ou M désigne une zone métallique,12. X-ray source according to one of claims 1 to 10, characterized in that the photoconductive device is a MIN diode or M denotes a metal zone,
13. Source radiogène selon l'une des revendications 1 à 12, caractérisée en ce que l'élément photoconducteur comprend une couche métallique à au moins une de ses faces de contact.13. X-ray source according to one of claims 1 to 12, characterized in that the photoconductive element comprises a metal layer to at least one of its contact faces.
14. Source radiogène selon l'une des revendications 1 à 13, caractérisée en ce que le substrat comprend une face dite avant supportant l'élément émetteur, la source de lumière éclairant ladite face avant.14. X-ray source according to one of claims 1 to 13, characterized in that the substrate comprises a so-called front face supporting the emitter element, the light source illuminating said front face.
15. Source radiogène selon l'une des revendications 1 à 13, caractérisée en ce que le substrat est transparent à ladite source de lumière, ladite source de lumière éclairant ledit substrat en face opposée à la face avant.15. X-ray source according to one of claims 1 to 13, characterized in that the substrate is transparent to said light source, said light source illuminating said substrate opposite to the front face.
16. Source radiogène selon l'une des revendications 13 ou 15, caractérisée en ce que le substrat présente une zone amincie destinée à être illuminée, de manière à minimiser les phénomènes d'absorption dans le substrat, ladite source de lumière éclairant ledit substrat en face opposée à la face avant.16. X-ray source according to one of claims 13 or 15, characterized in that the substrate has a thinned area intended to be illuminated, so as to minimize the absorption phenomena in the substrate, said light source illuminating said substrate by face opposite to the front face.
17. Source radiogène selon l'une des revendications 1 à 16, caractérisée en ce qu'elle comprend des moyens de réglage de la puissance optique de la source de lumière pour régler la puissance de rayons X générés. 17. X-ray source according to one of claims 1 to 16, characterized in that it comprises means for adjusting the optical power of the light source to adjust the power of generated X-rays.
18. Source radiogène selon l'une des revendications selon l'une des revendications 1 à 17, caractérisée en ce qu'elle comprend des moyens pour régler la focalisation de la source de lumière sur la source d'électrons.18. X-ray source according to one of claims according to one of claims 1 to 17, characterized in that it comprises means for adjusting the focus of the light source on the electron source.
19. Source radiogène selon l'une des revendications 1 à 18, caractérisée en ce qu'elle comprend un mono-tube X de symétrie cylindrique comportant une enceinte, renfermant une photocathode, une cible, un miroir, permettant d'illuminer la photocathode avec un faisceau lumineux pénétrant dans le mono-tube par sa paroi cylindrique .19. X-ray source according to one of claims 1 to 18, characterized in that it comprises a mono-tube X of cylindrical symmetry comprising an enclosure, enclosing a photocathode, a target, a mirror, for illuminating the photocathode with a light beam entering the mono-tube through its cylindrical wall.
20. Source radiogène selon l'une des revendications 1 à 19, caractérisée en ce qu'elle comprend plusieurs mono-tubes X, un support circulaire supportant lesdits mono-tubes X disposés radialement, une alimentation haute tension, des moyens de distribution de ladite alimentation haute tension sur les différents mono-tubes de manière à produire des faisceaux de rayons X, et des moyens individuels de contrôles optiques indépendants dédiés à chacun des mono-tubes.20. X-ray source according to one of claims 1 to 19, characterized in that it comprises several mono-tubes X, a circular support supporting said mono-tubes X arranged radially, a high voltage supply, distribution means of said high-voltage power supply on the different mono-tubes so as to produce X-ray beams, and individual means of independent optical controls dedicated to each of the single-tubes.
21. Source radiogène selon la revendication 20, caractérisée en ce que lesdits faisceaux de contrôle optique et les faisceaux de rayons X sont tous parallèles entre eux et perpendiculaires audit support circulaire.21. X-ray source according to claim 20, characterized in that said optical control beams and the X-ray beams are all parallel to each other and perpendicular to said circular support.
22. Source radiogène selon la revendication 20, caractérisée en ce qu'elle comprend des moyens pour faire converger lesdits faisceaux de rayons X.22. X-ray source according to claim 20, characterized in that it comprises means for converging said X-ray beams.
23. Source radiogène selon l'une des revendications 1 à 18, caractérisée en ce qu'elle comprend une enceinte, plusieurs ensembles constitués chacun d'un couple de photocathode associée à une cible et des moyens de distribution d'alimentation desdites photocathodes.23. X-ray source according to one of claims 1 to 18, characterized in that it comprises an enclosure, several sets each consisting of a pair of photocathode associated with a target and supply distribution means of said photocathodes.
24. Source radiogène selon la revendication 23, caractérisée en ce que l'enceinte présente une forme concave de manière à générer des faisceaux de rayons X convergents. 24. X-ray source according to claim 23, characterized in that the enclosure has a concave shape so as to generate convergent X-ray beams.
25. Source radiogène selon l'une des revendications 1 à 24, caractérisée en ce qu'elle comporte :25. X-ray source according to one of claims 1 to 24, characterized in that it comprises:
- une photocathode dite étendue ou un ensemble de photocathodes ; - une cible dite étendue ou un ensemble de cibles, en regard respectivement de ladite photocathode étendue ou de l'ensemble de photocathodes;an extended photocathode or a set of photocathodes; a so-called extended target or set of targets respectively facing said extended photocathode or the set of photocathodes;
- un dispositif d'adressage de l'illumination d'une photocathode étendue ou d'un ensemble de photocathodes, de manière à sélectionner différentes zones au cours du temps sur la photocathode étendue ou à sélectionner différentes photocathodes dans l'ensemble de photocathodes et corrélativement rendre les zones de la cible étendue ou d'une cible parmi l'ensemble de cibles, émettrices de rayons X.a device for addressing the illumination of an extended photocathode or of a set of photocathodes, so as to select different zones over time on the extended photocathode or to select different photocathodes in the set of photocathodes and correlatively make the extended target or target areas among the X-ray target set.
26. Source radiogène selon la revendication 25, caractérisée en ce qu'elle comprend un modulateur spatial et/ou temporel permettant de défléchir un faisceau issu de la source d'illumination, vers différentes zones de la photocathode étendue ou différentes photocathodes parmi un ensemble de photocathodes.26. X-ray source according to claim 25, characterized in that it comprises a spatial and / or temporal modulator for deflecting a beam from the illumination source, to different areas of the extended photocathode or different photocathodes among a set of photocathodes.
27. Source radiogène selon l'une des revendications 1 à 25, caractérisée en ce que le dispositif d'adressage est un modulateur spatial de lumière éclairé par un faisceau étendu permettant de transférer différentes lois d'éclairement sur une zone de la photocathode étendue ou sur une photocathode dans l'ensemble de photocathodes, et d'obtenir les lois correspondantes d'émission de rayons X depuis une zone de cible étendue ou sur une cible de l'ensemble de cibles.27. X-ray source according to one of claims 1 to 25, characterized in that the addressing device is a spatial light modulator illuminated by an extended beam for transferring different illumination laws to a zone of the extended photocathode or on a photocathode in the set of photocathodes, and to obtain the corresponding X-ray emission laws from an extended target area or target of the set of targets.
28. Source radiogène selon la revendication 25, caractérisée en ce qu'elle comprend un ensemble de sources d'illumination et en ce que le dispositif d'adressage est un déflecteur opto-mécanique ou opto-électrique et active des sources d'illumination associées de manière biunivoque à différentes zones de la photocathode étendue ou à différentes photocathodes de l'ensemble de photocathodes, lesdites zones ou photocathodes étant associées de manière biunivoque à différentes zones de la cible étendue ou à différentes cibles parmi l'ensemble de cibles.28. X-ray source according to claim 25, characterized in that it comprises a set of illumination sources and in that the addressing device is an opto-mechanical or opto-electric deflector and activates associated illumination sources. in a single-handed manner to different areas of the extended photocathode or to different photocathodes of the set of photocathodes, said zones or photocathodes being associated one-to-one with different areas of the extended target or with different targets among the set of targets.
29. Source radiogène selon l'une des revendications 1 à 28, caractérisée en ce qu'elle comporte en outre au moins un accélérateur linéaire pour accélérer les électrons émis par la source d'électrons.29. X-ray source according to one of claims 1 to 28, characterized in that it further comprises at least one linear accelerator for accelerating the electrons emitted by the electron source.
30. Source radiogène selon la revendication 1 à 29, caractérisée en ce que la distribution de puissance lumineuse est réalisée au moins pour partie par propagation guidée (fibres optiques) au lieu de propagation spatiale.30. X-ray source according to claim 1 to 29, characterized in that the light power distribution is carried out at least partly by guided propagation (optical fibers) instead of spatial propagation.
31. Source radiogène selon la revendication 1 à 30, caractérisée en ce que les modulateurs spatiaux sont de type à propagation guidéeRadiogenic source according to claim 1 to 30, characterized in that the spatial modulators are of guided propagation type
32. Source radiogène selon 1 à 31 , caractérisée en ce que l'enceinte à vide comporte des passages pour les fibres optiques 32. X-ray source according to 1 to 31, characterized in that the vacuum chamber comprises passages for the optical fibers
EP09703777.4A 2008-01-25 2009-01-23 Radiogenic source comprising at least one electron source combined with a photoelectric control device Active EP2232520B1 (en)

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FR0800397A FR2926924B1 (en) 2008-01-25 2008-01-25 RADIOGENIC SOURCE COMPRISING AT LEAST ONE ELECTRON SOURCE ASSOCIATED WITH A PHOTOELECTRIC CONTROL DEVICE
PCT/EP2009/050809 WO2009092813A1 (en) 2008-01-25 2009-01-23 Radiogenic source comprising at least one electron source combined with a photoelectric control device

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JP2016033922A (en) 2016-03-10
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CA2713060A1 (en) 2009-07-30
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CA2713060C (en) 2017-08-29

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