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) opposite 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 containment 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 serves to determine the state of the microstructure of matter with high resolution.

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

[0005] An illustration of secondary beams that are at least partly responsible for measurement noise is shown in [Fig. 1]. This type of beam is referred to as "cladding leakage." Secondary beams r1, r2, and r3 are three examples of beams emanating from the focal point F of an X-ray source 10. Beam r1 passes through the wall of the source 10 and reaches the detector 20 after scattering off the wall of the booth 1, in which the measurement is performed. Beam r2 passes through the wall of the source 10 and reaches the detector 20 directly, possibly passing through the object 30, without being reflected and without passing through the window 11 of the source. Finally, the r3 beam is diffracted by the edge of the window 11 and also reaches the detector 20, possibly 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 measurement noise..

[0006] It is known in the case of a Laue diffraction setup (transmission, reflection, or backscatter), as illustrated in [Fig. 2], to use a collimator 12, positioned in front of the window 11, to modify the shape of the beam exiting the source 10. The beam directly impacting the object, called the "primary beam," then changes from a conical geometry to a quasi-parallel geometry. This geometry allows for controlled propagation of X-rays towards the object and reduces the number of secondary beams. However, as shown in [Fig. 2], duct leakage scattering from cabin 1 or from another element within cabin 1 (beam rj) is only slightly affected by the presence of collimator 12. Furthermore, collimator 12 itself induces the scattering of secondary beams (beam r4) due to its geometry.

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

[0008] The invention offers a solution to the problems mentioned above, by allowing the isolation of the X-ray source in a closed enclosure which includes an orifice in the continuity of which is positioned a confinement element used 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 an X-ray flux; • An insulating enclosure surrounding the X-ray source, the insulating enclosure including an orifice opposite the window, the orifice being adapted to form a primary beam from the X-ray flux; • A containment 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 both sides of the containment element along the elongation axis, and the recess being arranged to allow the propagation of the primary beam without alteration.

[0011] The term "X-ray source" or "X-ray tube" refers to 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 X-ray emission from the source is multidirectional. The dimensions of the tube depend on several parameters, including the focal spot size, the current in the tube, and the potential difference between the ends of the tube. In particular, the focal spot size 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 tube envelope 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" refers to a casing that completely surrounds the X-ray tube, except at the enclosure's orifice. The enclosure is insulating in that it is impermeable to X-rays, typically through the use of a dense material with a significant thickness. The dimensions of the enclosure therefore depend on the dimensions, energy properties, and focal spot size of the tube.

[0014] The term "opposite" 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 out of the insulating enclosure.

[0015] The term "primary beam" refers to a set of X-rays originating from the X-ray flux emitted 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 from the primary beam are diffracted by the object and then detected by a detector placed after the object, and correspond to the signal to be analyzed. Conversely, the term "secondary beam" refers to any beam generated by the tube that is a potential source of noise for the measurement.

[0016] Thanks to the invention, the detection of photons from the primary beam diffracted by the inspected object is improved compared to known prior art techniques. Thus, the measurement accuracy for quantifying the object's properties is also improved, even though the signal-to-noise ratio of the measurement is on the order of 2 dB. The energy of the secondary beams, the source of this noise, is indeed significantly attenuated by the presence of the insulating enclosure around the tube, including towards the rear of the source. Moreover, the use of the confinement element serves to filter the secondary beams generated by the geometry of the insulating enclosure's orifice, thereby significantly reducing their energy.

[0017] Furthermore, the insulating enclosure is of reasonable dimensions, since it is only necessary to insulate the tube, which is less than one meter long. Similarly, the containment element is small because its hollowness depends in particular on the size of the orifice and the divergence of the primary beam. Moreover, a large thickness of material is not required for this containment element because its attenuation of secondary beams depends on a ratio between its thickness and its length, and not solely on its thickness.

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

[0019] In one embodiment, the insulating enclosure and / or the containment 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 compounds 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 the 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 per pixel 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 through 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 secondary beam of the X-ray flux propagating to the furthest position from the elongation axis on the detector, in a direction orthogonal to the elongation axis.

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

[0026] Furthermore, 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 the noise sources, i.e., the secondary beams, which contribute to the 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 per pixel from the secondary beams.

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

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

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

[0030] A "numerical model" is understood to be a numerical tool whose implementation allows the calculation by simulation of the divergence geometry of the primary beam.

[0031] "Divergent geometry" is understood to be the shape and dimensions of the primary beam during its propagation from the orifice of the enclosure. In other words, the divergence geometry corresponds to the variation of the cross-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 illustrative purposes only and are in no way limiting of the invention. • Fig. 1 is a schematic representation of an X-ray inspection system. • Fig. 2 is a schematic representation of an X-ray inspection system following 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 manufacturing process for a containment element, according to one embodiment. DETAILED DESCRIPTION

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

[0035] A first aspect of the invention relates to a containment system for 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 containment system 2 includes a source 10, which includes a focus F from which X-rays are emitted.

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

[0038] The containment system 2 comprises an insulating enclosure 13, which surrounds the entire volume of the tube 10. The insulating enclosure 13 is positioned around the source 10, i.e., around the electronic device that generates the X-rays. Such an arrangement is therefore compatible with any X-ray source. The insulating enclosure is hereafter referred to as the "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 X-ray generation device 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 includes 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 through the thickness of the enclosure 13.

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

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

[0045] The orifice 13-1 has a cross-section with a diameter 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, with the length of one of its sides 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 includes 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 includes 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 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, it is understood 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 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 side length) of the recess may be at least 1 mm, or even at least 5 mm, greater than the diameter (or side length) of the divergence geometry. The diameter (or side length) of the recess may be less than or equal to 1 cm.

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

[0052] The containment element 14 is located at 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 containment element 14 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. The wall thickness C of the containment element 14 may be constant or variable.

[0055] The combined use of the enclosure 13 and the containment 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 can be included in an X-ray booth 1, in which an object 30 is inspected using the containment system 2. The containment system 2 is positioned so that the containment element 13 is at a distance deo from the object 30. The booth 1 includes the detector 20.

[0058] The detector 20 behind the object is used to detect the diffracted beams Q' resulting 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 part. The detector 20 is also suitable for detecting secondary beams from various secondary sources.

[0059] The distance deo between the containment 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 are generated, related to the diffraction of the primary beam fl by the environment, in particular, the air in the cabin 1. Thus, the shorter this distance, the lower the measurement noise energy.

[0060] In one embodiment, shown in Figure 5, the containment 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 containment element 14 is in contact or in near contact with the object 30. That is to say, the distance between the containment 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 containment element 14 depend on the angle with respect 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 scattering through the orifice 13-1, along a direction orthogonal to the elongation axis X. The length le and the wall thickness of the containment element 14 also depend on the distance dce between the containment element 14 and the wall of the enclosure 13.

[0062] In other words, the length le and the wall thickness of the containment element 14 are determined as a function of the distance dce between the containment element 14 and the wall of the enclosure 13, and of the secondary beam emitted at the exit 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 per pixel is detected for any secondary beam propagating to detector 20, for example by scattering from orifice 13-1, with an angle less than or equal to the angle amax, with respect to the elongation axis X. Such an embodiment makes it possible to limit the amount of material required to manufacture the confinement element 14 while reducing measurement noise.

[0064] To manufacture the containment element 14, in particular to create the recess 14-1 according to the characteristics described above, the divergence geometry to which the recess 14-1 corresponds can be obtained by: • Use of a digital model, typically a simulation tool which allows 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 tube 10, of the primary beam section Q. Typically, a detection by detector 20 of the X-ray flux is performed for each of the distances from tube 10 in order to determine the diameter (or side length) of the primary beam section û via this detection.

[0065] The containment element 14 can be manufactured by any known manufacturing technique allowing the hollowing to be made according to the characteristics described above.

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

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

[0068] The process 100 then includes a manufacturing step 120, depending on the divergence geometry obtained, of the containment element 14, which includes the recess 14-1 according to the characteristics and possible variants previously described.

Claims

Demands

1. X-ray containment system (2) comprising: - An X-ray source (10) including a window (11), the X-ray source (10) being adapted to emit an X-ray flux; - An insulating enclosure (13) surrounding the X-ray source (10), the insulating enclosure (13) including an orifice (13-1) opposite the window (11), the orifice (13-1) being adapted to form a primary beam (1) from the X-ray flux; - A containment 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) being open on both sides of the containment 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, wherein the insulating enclosure (13) and / or the containment element (14) are composed of a material having a density greater than or equal to 5 g / cm3.

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

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

5. System (2) according to any one of the preceding claims, wherein the containment 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 any one of the preceding claims, wherein at least one secondary beam (w) is diffused by the orifice (13-1), the primary (u) 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 wall thickness (t?<3) dependent of the angle (amax) formed, with respect to the elongation axis (X), by at least one secondary beam (a!) of the X-ray flux propagating to the furthest position from the elongation axis (X) on the detector (20), following a direction orthogonal to the elongation axis (X)•

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

8. A method for manufacturing a containment element (14) intended to be included in a containment system (2) according to any one of the preceding claims, comprising: - Obtain the divergence geometry of the primary beam (O) from: • A digital model; or • A measurement of the cross-section of the primary beam (O) at a plurality of distances from the X-ray source (10); - Manufacture the confinement element (14) from the divergence geometry obtained, 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) being open on both sides 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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