X-ray containment system for high sensitivity measurements

Abstract

X-ray confinement system for high sensitivity measurements One aspect of the invention relates to an X-ray confinement system (2) comprising an X-ray source (10) with a window (11), an insulating enclosure (13) surrounding the X-ray source and comprising an orifice (13-1) facing the window (11), and a confinement element (14) positioned outside the insulating enclosure (13) and comprising a recess (14-1) opening on either side of the confinement element (14) along the elongation axis () of the recess (14-1) and corresponding to the divergence geometry of the primary beam (). Figure to be published with the abstract: Figure 3

Description

Title of the invention: X-ray confinement system for high sensitivity measurements TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of equipment for the generation of X-rays.

[0002] The present invention relates to an X-ray confinement system. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Electromagnetic radiation of the X-ray type is used in particular for the exploration of matter, in fundamental research, and for the inspection of objects, such as a mechanical part for industry or a human or animal body in the medical field. In particular, the study of X-ray diffraction by the Laue method is used to determine a state of the microstructure of matter with high resolution.

[0004] Industrial and laboratory equipment (other than synchrotron) used for generating X-rays is not, however, suitable for emitting a collimated beam of X-rays towards the object. Indeed, X-ray sources are generally multidirectional. Thus, due to this multidirectional nature and the low efficiency of the emission systems, the useful signal of a measurement is strongly disturbed by the measurement noise, with a low signal-to-noise ratio. The analysis of the useful signal is therefore strongly penalized.

[0005] An illustration of secondary beams at the origin, at least in part, of the measurement noise is provided in [Fig.l]. This type of beam is referred to as "sheath leakage". The secondary beams rb r2 and r3 are three examples of beams emanating from the focus F of an X-ray source 10. The beam ri passes through the wall of the source 10 and reaches the detector 20 after scattering on the wall of the cabin 1, in which the measurement is carried out. The beam r2 passes through the wall of the source 10 and directly reaches the detector 20, possibly passing through the object 30, without being reflected and without passing through the window 11 of the source. Finally, the beam r3 is diffracted by the edge of the window 11 and also reaches the detector 20, possibly by passing through the object 30. It is noted that the scattering by the object or by the air of the X-rays, not shown here, also generates secondary beams which induce an increase in the measurement noise..

[0006] It is known in the case of a Laue diffraction assembly (in transmission, reflection or return), as illustrated in [Fig.2], to use a collimator 12, positioned in front of the window 11 to modify the shape of the beam at the output of the source 10. The beam in direct incidence on the object, called the "primary beam", then changes from a conical geometry to a quasi-parallel geometry. This geometry allows controlled propagation of the X-rays towards the object and reduces the number of secondary beams. However, as shown in the illustration in [Fig.2], the leakage of cladding diffused by cabin 1 or by another element in cabin 1 (beam rj) is little affected by the presence of collimator 12. In addition, collimator 12 itself induces the diffusion of secondary beams (beam r4) due to its geometry.

[0007] There is therefore a need for an X-ray measurement system which improves the detection of the primary beam with respect to measurement noise. Summary of the invention

[0008] The invention provides a solution to the problems mentioned above, by allowing the isolation of the X-ray source in a closed enclosure which comprises an orifice in the continuity of which is positioned a confinement element serving to attenuate the energy of the secondary beams without altering the propagation of the primary beam.

[0009] A first aspect of the invention relates to an X-ray confinement system comprising:

[0010] An X-ray source comprising a window, the X-ray source being adapted to emit a flux of X-rays; • An insulating enclosure surrounding the X-ray source, the insulating enclosure comprising an orifice facing the window, the orifice being adapted to form a primary beam from the X-ray flux; • A confinement element positioned outside the insulating enclosure and comprising a recess extending along an elongation axis corresponding to the propagation path of the primary beam, the recess opening out on either side of the confinement element along the elongation axis, and the recess being arranged to allow propagation of the primary beam without alteration.

[0011] The term "X-ray source" or "X-ray tube" means a device capable of emitting X-rays, for example based on Coolidge tube technology or closed tube, open tube, rotating anode tube, liquid anode tube, etc. The emission of X-rays by the source is multidirectional. The dimensions of the tube depend on several parameters, in particular the size of the focus, the intensity in the tube and the potential difference between the ends of the tube. In particular, the size of the focus is between 1 μm and 5.5 mm, for energies ranging from 10 keV to 450 keV and for powers of 2 W or more, for example 4 kW or more, or even 50 kW or more.

[0012] The term "window" means a portion of the source, typically a portion of the envelope of the tube in which the X-rays are generated, which is permeable to X-ray and vacuum-tight, such as a window made of beryllium.

[0013] The term "enclosure" means an envelope completely surrounding the X-ray tube, except at the orifice of the enclosure. The enclosure is insulating in that it is non-permeable to X-rays, typically by the use of a dense material with a significant thickness. The dimensions of the enclosure therefore depend on the dimensions, energy properties and focus size of the tube.

[0014] “Facing” means that the orifice is located opposite the window of the tube so as to allow the propagation of the primary beam of the tube outside the insulating enclosure.

[0015] The term "primary beam" means a set of X-rays originating from the X-ray flux radiated by the tube through the window and collimated by the collimator. The primary beam is the beam used to illuminate an object to be inspected. The photons originating from the primary beam are diffracted by the object and then detected by a detector placed after the object, and correspond to the useful signal to be analyzed. On the contrary, the term "secondary beam" means any beam generated by the tube and which is a potential source of noise for the measurement.

[0016] Thanks to the invention, the detection of the photons of the primary beam diffracted by the inspected object is improved compared to the known techniques of the state of the art. Thus, the precision of the measurement for quantifying the properties of the object is also improved, even if the signal-to-noise ratio of the measurement is of the order of 2 dB. The energy of the secondary beams, the source of this noise, is in fact significantly attenuated by the presence of the insulating enclosure around the tube, including towards the rear of the source. In addition, the use of the confinement element serves to filter the secondary beams generated by the geometry of the orifice of the insulating enclosure, thus significantly reducing their energy.

[0017] Furthermore, the insulating enclosure is of reasonable dimensions, since it is only necessary to insulate the tube, which has dimensions of less than one meter. Similarly, the confinement element is of small dimensions since its recess depends in particular on the size of the orifice and the divergence of the primary beam. Furthermore, there is no need for a large thickness of material for this confinement element because its attenuation of the secondary beams depends on a ratio between its thickness and its length, and not only on its thickness.

[0018] In addition to the characteristics which have just been mentioned, the system according to the first aspect of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations.

[0019] In one embodiment, the insulating enclosure and / or the confinement element are composed of a material having a density greater than or equal to 5 g / cm3

[0020] In one embodiment, the insulating enclosure and / or the containment element are composed of lead, copper, tin and / or tungsten.

[0021] In one embodiment, the insulating enclosure has a thickness greater than or equal to 1 mm.

[0022] The use of high-density material makes it possible to limit the thickness of the enclosure to achieve the desired level of insulation, and therefore to limit the size of the enclosure. Preferably, the material and thickness of the enclosure are such that a detector detects as few photons as possible, in particular so that it detects less than one photon per second and per pixel coming from the secondary beams.

[0023] In one embodiment, the containment element has a wall thickness greater than or equal to 2 mm and a length along the elongation axis greater than or equal to 10 mm.

[0024] In one embodiment, at least one secondary beam is diffused by the orifice, the primary and secondary beams propagate to a detector, and the confinement element has a length along the elongation axis and a wall thickness dependent on the angle formed, with respect to the elongation axis, by the at least one secondary beam of the X-ray flux propagating to the position furthest from the elongation axis on the detector, in a direction orthogonal to the elongation axis.

[0025] The secondary beams which are generated by diffraction by the geometry of the collimator, and which propagate towards a detector, are emitted with a quasi-grazing but non-zero angle of incidence, that is to say they diverge slightly from the propagation axis of the primary beam. Thus, due to the geometric characteristics of the recess, these secondary beams must pass through the thickness of the confinement element over almost its entire length. Consequently, it is not useful to have a large wall thickness for the confinement element. On the contrary, it is preferable for its length to be greater than its thickness to ensure significant attenuation of the energy of the photons.

[0026] In addition, adapting the wall thickness and length of the confinement element to the secondary beam having the largest angle of incidence on the detector ensures that noise sources, i.e., secondary beams, affecting measurement noise have attenuated energy during measurement. Preferably, the material and wall thickness of the confinement element are such that a detector detects fewer photons per second and per pixel from the secondary beams.

[0027] In one embodiment, the containment element is in contact with the insulating enclosure.

[0028] The interest is thus to limit the diffraction of the secondary beams by the geometry of the collimator.

[0029] A second aspect of the invention relates to a method of manufacturing an element containment intended to be included in a containment system according to one of the preceding claims, comprising: • Obtain the divergence geometry of the primary beam from: • A digital model; or • A measurement of the primary beam cross-section at a plurality of distances from the X-ray source; • Manufacture the confinement element from the obtained divergence geometry, the confinement element comprising a recess extending along an elongation axis corresponding to the propagation path of the primary beam, the recess opening out on either side of the confinement element along the elongation axis, and the recess being arranged to allow the propagation of the primary beam without alteration.

[0030] The term “numerical model” means a numerical tool whose implementation allows the calculation by simulation of the divergence geometry of the primary beam.

[0031] The term “divergence geometry” means the shape and dimensions of the primary beam during its propagation from the orifice of the enclosure. In other words, the geometry of the divergence corresponds to the variation of the section of the primary beam as a function of the distance from the orifice of the enclosure.

[0032] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0033] The figures are presented for information purposes only and in no way limit the invention. • [Fig.l] is a schematic representation of an X-ray inspection system. • [Fig.2] is a schematic representation of an X-ray inspection system using a Laue diffraction setup. • [Fig.3] is a schematic representation of an embodiment of a containment system according to the invention. • [Fig.4] is a schematic representation of an embodiment of a containment element of the system according to [Fig.3]. • [Fig.5] is a schematic representation of an embodiment of a containment system according to the invention. • [Fig.6] is a schematic representation of an embodiment of a containment system according to the invention. • [Fig.7] is a diagram illustrating the sequence of steps in a method of manufacturing a containment element, according to one embodiment. DETAILED DESCRIPTION

[0034] Unless otherwise specified, the same element appearing in different figures presents a unique reference.

[0035] A first aspect of the invention relates to a system for confining an X-ray source aimed at significantly reducing the energy of secondary sources which are a source of measurement noise.

[0036] As illustrated in [Fig. 3], the confinement system 2 comprises a source 10, which comprises a focus F from which the X-rays are emitted.

[0037] The tube 10, also called tube 10, comprises a window 11 permeable to X-rays and vacuum-tight, in a known manner, such as a window comprising beryllium.

[0038] The confinement system 2 comprises an insulating enclosure 13, which encircles the entire volume of the tube 10. The insulating enclosure 13 is positioned around the source 10, that is to say around the electronic device which generates the X-rays. Such an arrangement is therefore compatible with any source of X-rays. The insulating enclosure is, hereinafter, called “enclosure”.

[0039] Alternatively, the enclosure 13 is positioned in the electronic device, around the vacuum chamber where the focus F is located. The enclosure is then, for example, inserted into the electronic device for generating X-rays at the time of its manufacture.

[0040] The enclosure has a thickness greater than or equal to 1 mm, or even greater than or equal to 2 mm. The thickness of the enclosure may be constant or variable.

[0041] The enclosure material has a density greater than or equal to 5 g / cm3. For example, the enclosure material is lead, tin and / or tungsten.

[0042] The enclosure 13 comprises an orifice 13-1 located opposite the window 11. The orifice is an opening made in the enclosure 13, through its thickness, and serves as a collimator. The orifice 13-1 is, for example, made by drilling into the thickness of the enclosure 13.

[0043] The orifice 13-1 is adapted to form, for example by collimation, a primary beam from the flux of X-rays. The presence of the orifice 13-1 causes the formation of at least one secondary beam by diffusion, in particular by diffusion on one of its walls.

[0044] The orifice 13-1 is of constant section and preferably cylindrical or quasi-cylindrical in shape, the circular section of which faces the window 11.

[0045] The orifice 13-1 has a cross-section whose diameter is greater than or equal to 0.5 mm. This diameter may be less than or equal to 10 mm. The cross-section of the orifice 13-1 may alternatively be square or rectangular in shape, the length of one of its sides being greater than or equal to 0.5 mm and may also be less than or equal to 10 mm.

[0046] The containment system 2 also comprises a containment element 14. As illustrated in [Fig.4], where the containment element 14 is seen in perspective ( [Fig.4] a) and seen from the side ([Fig.4] b), the containment element 14 comprises a recess 14-1.

[0047] The recess 14-1 extends along an elongation axis X. This elongation axis X corresponds to the propagation path of a primary beam of the X-ray flux radiated by the tube 10 through the orifice 13-1. The recess 14-1 opens out on each side of the confinement element 14, along the elongation axis X.

[0048] The recess 14-1 is such that its geometry corresponds to the divergence geometry of the primary beam Q

[0049] By "corresponding" to the divergence geometry is meant that the shape of the recess 14-1 allows the propagation of the primary beam O without altering it. The shape of the recess is therefore at least of the same shape and diameter (or side length in the case of a square or rectangular orifice 13-1) equal to or greater than the diameter (or side length) of the divergence geometry of the primary beam.

[0050] In other words, the recess is such that the rays of the primary beam O do not pass through the material of the confinement element 14, and that the secondary beams cannot pass through the confinement element 14 without passing through its wall. For example, the diameter (or the length of the side) of the recess may be greater by at least 1 mm, or even by at least 5 mm, compared to the diameter (or the length of the side) of the divergence geometry. The diameter (or the length of the side) of the recess may be less than or equal to 1 cm.

[0051] The confinement element 14 is positioned so that the recess 14-1 is opposite the orifice 13-1. That is to say, the confinement element 14 is positioned so that the primary beam Q at the outlet of the orifice propagates entirely in the recess without the rays of the primary beam Q passing through the material of the confinement element 14.

[0052] The confinement element 14 is spaced a distance dce from the wall of the enclosure 13. This distance dce is between 0 and 10 mm.

[0053] The material of the containment element has a density greater than or equal to 5 g / cm3. For example, the material of the containment element is lead, tin and / or tungsten.

[0054] The confinement element 14 has a wall thickness greater than or equal to 2 mm and a length 1c along the elongation axis greater than or equal to 10 mm. The wall thickness C? of the confinement element 14 may be constant or variable.

[0055] The joint use of the enclosure 13 and the confinement element 14 makes it possible to significantly reduce the energy of the secondary beams, a source of measurement noise.

[0056] Preferably, the thickness of the enclosure 13 and the density of the material(s) it comprises, as well as the wall thickness and the length of the element of confinement 14 are such that less than one photon per second per pixel for any secondary beam propagating to a detector 20 during a measurement.

[0057] The containment system 2 may be comprised in an X-ray cabin 1, in which an object 30 is inspected using the containment system 2. The containment system 2 is positioned such that the containment element 13 is a distance deo from the object 30. The cabin 1 comprises the detector 20.

[0058] The detector 20 behind the object is used to detect the diffracted beams Q' originating from the diffraction of the primary beam û by the object 30. The detector can also be used to detect the primary beam fl passing through the room. The detector 20 is also adapted to detect the secondary beams originating from the various secondary sources.

[0059] The distance deo between the confinement element 14 and the object 30 is between 0 and 50 cm, or even between 0 and 10 cm, or even between 0 and 10 mm. It is noted that the shorter this distance, the fewer secondary sources of diffraction, linked to the diffraction of the primary beam fl by the environment, in particular the air in the cabin 1, which are generated. Thus, the shorter this distance, the more the energy of the measurement noise decreases.

[0060] In one embodiment, shown in Figure 5, the confinement element 14 is in contact with the wall of the enclosure 13, and is positioned so that its recess 14-1 is in continuity with the orifice 13-1, without altering the propagation of the primary beam fl. At its other end, the confinement element 14 is in contact or in quasi-contact with the object 30. That is to say that the distance between the confinement element 14 and the object 30 is as small as possible, taking into account the shape of the object 30.

[0061] In one embodiment, as shown in Figure 6, the length le and the wall thickness of the confinement element 14 depend on the angle relative to the elongation axis X, formed by one of the secondary beams propagating to the edge at the position furthest from the elongation axis on the detector 20, for example after diffusion by the orifice 13-1, in a direction orthogonal to the elongation axis X. The length le and the wall thickness of the confinement element 14 also depend on the distance dce between the confinement element 14 and the wall of the enclosure 13.

[0062] In other words, the length le and the wall thickness of the confinement element 14 are determined as a function of the distance dce between the confinement element 14 and the wall of the enclosure 13, and of the secondary beam emitted at the outlet of the orifice 13-1, which has the highest angle of incidence on the detector 20. It is therefore the secondary beam w furthest from the elongation axis X which is detected by the detector 20.

[0063] In particular, the length L and the wall thickness of the containment element 14 are determined so that less than one photon per second and per pixel is detected for any secondary beam propagating to the detector 20, for example by diffusion from the orifice 13-1, with an angle less than or equal to the angle amax, relative to the elongation axis X. Such an embodiment makes it possible to limit the quantity of material necessary for the manufacture of the confinement element 14 while reducing the measurement noise.

[0064] To manufacture the confinement element 14, in particular to produce the recess 14-1 according to the characteristics previously described, the divergence geometry to which the recess 14-1 corresponds can be obtained by: • Use of a digital model, typically a simulation tool which makes it possible to simulate via a computer the propagation of the X-ray flux through the orifice 13-1, from the focus F of the tube 10; • Measurement along a plurality of distances from the tube 10, of the section of the primary beam Q. Typically, a detection by the detector 20 of the X-ray flux is carried out for each of the distances from the tube 10 in order to determine the diameter (or the length of the side) of the section of the primary beam û via this detection.

[0065] The containment element 14 can be manufactured by any known manufacturing technique allowing the production of the recess according to the characteristics previously described.

[0066] A second aspect of the invention therefore relates to a method 100 for manufacturing the confinement element 14, as illustrated in [Fig.7].

[0067] The method 100 comprises a step 110 of obtaining the divergence geometry, which can be obtained, for example, according to the methods previously described.

[0068] The method 100 then comprises a step 120 of manufacturing, as a function of the divergence geometry obtained, the confinement element 14, which comprises the recess 14-1 according to the characteristics and possible variants previously described.

Claims

Claims

1. X-ray confinement system (2) comprising: - An X-ray source (10) comprising a window (11), the X-ray source (10) being adapted to emit a flux of X-rays; - An insulating enclosure (13) surrounding the X-ray source (10), the insulating enclosure (13) comprising an orifice (13-1) facing the window (11), the orifice (13-1) being adapted to form a primary beam (£1) from the flux of X-rays; - A confinement element (14) positioned outside the insulating enclosure (13) and comprising a recess (14-1) extending along an elongation axis (X) corresponding to the propagation path of the primary beam (£2), the recess (14-1) opening out on either side of the confinement element (14) along the elongation axis (X), and the recess (14-1) being arranged to allow the propagation of the primary beam (£2) without alteration.

2. System (2) according to the preceding claim, in which the insulating enclosure (13) and / or the confinement element (14) are composed of a material having a density greater than or equal to 5 g / cm3.

3. System (2) according to one of the preceding claims, in which the insulating enclosure (13) and / or the containment element (14) are composed of lead, copper, tin and / or tungsten.

4. System (2) according to one of the preceding claims, in which the insulating enclosure (13) has a thickness greater than or equal to 1 mm.

5. System (2) according to one of the preceding claims, in which the confinement element (14) has a wall thickness (^) greater than or equal to 2 mm and a length (4) along the elongation axis (X) greater than or equal to 10 mm.

6. System (2) according to one of the preceding claims, in which at least one secondary beam (w) is diffused by the orifice (13-1), the primary (û) and secondary (60) beams propagate to a detector (20), and the confinement element (14) has a length (4) along the elongation axis (X) and a thickness (t?<3) of dependent wall of the angle (amax) formed, with respect to the elongation axis (X), by the at least one secondary beam (a!) of the X-ray flux propagating to the position furthest from the elongation axis (X) on the detector (20), in a direction orthogonal to the elongation axis (X)•

7. System (2) according to one of the preceding claims, in which the confinement element (14) is in contact with the insulating enclosure (13).

8. A method of manufacturing a containment element (14) intended to be included in a containment system (2) according to one of the preceding claims, comprising: - Obtain the divergence geometry of the primary beam (O) from: • A digital model; or • A measurement of the section of the primary beam (O) at a plurality of distances from the X-ray source (10); - Manufacture the confinement element (14) from the obtained divergence geometry, the confinement element (14) comprising a recess (14-1) extending along an elongation axis (X) corresponding to the propagation path of the primary beam (O), the recess (14-1) opening out on either side of the confinement element (14) along the elongation axis (X), and the recess (14-1) being arranged to allow the propagation of the primary beam (fi) without alteration.

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