RADIATION DETECTOR AND METHOD FOR ITS USE

Description

[0001] The invention relates to a radiation detector with at least one radiation detection device and with at least one planar support on which the radiation detection device is mounted, wherein the planar support is flexible in at least one spatial direction and includes a shape detection device configured to detect the shape of the support. The invention further relates to a method for detecting radiation with such a radiation detector.

[0002] In practice, X-ray detectors are known to consist of a scintillator layer and a photodiode. The scintillator layer converts X-rays into visible light, which the photodiode then converts into electrical signals, allowing detection. These X-ray detectors have the disadvantage of always being flat. Curved detectors, which are advantageous for some applications, cannot be manufactured in this way.

[0003] From Büchele, P., Richter, M., Tedde, S. et al., X-ray imaging with scintillator-sensitized hybrid organic photodetectors, Nature Photon 9, 843-848 (2015), a solution to this problem is known: using ceramic particles as scintillators and embedding them in a conductive polymer. The conductive polymer converts the light emitted by the scintillator into electrical signals, which enable analog or digital evaluation and storage of the image data. Unlike silicon photodiodes, the conductive polymer material is flexible, so the radiation detectors produced in this way can also be curved. However, a disadvantage is that the shape of the radiation detector is unknown when it is freely movable. This results in image distortions on the two-dimensional detector, and the measurement data can only be evaluated and interpreted inadequately.The known radiation detector must therefore be placed on a surface with a known geometry in order to enable the unfolding or rectification of the image data.

[0004] From S. Wilbur et al.: Flexible X-ray imaging detectors using scintillating fibers. JINST 17 (2022) C10013, an X-ray image detector is known. This detector can generate high-resolution images and is flexible enough to produce an image on a curved surface. Furthermore, the known X-ray image detector is able to recognize its final shape.

[0005] US patent 2005 / 0205794 A1 discloses a device capable of directly and efficiently measuring surface contamination of objects with curved surfaces. The measuring device comprises a radioactivity detection section with a structure in which a multitude of elongated, plate-shaped detection units are arranged and detachably connected to one another by connecting pieces.

[0006] US 2014 / 357988 A1 relates to a sensor device for detecting a radiation dose received at the sensor device, wherein the sensor device comprises a flexible body and an optical shape detection device.

[0007] EP 3 667 371 A1 discloses the bending of a flexible X-ray detector for imaging a curved structure or a curved object and the correction of the image distortion produced by the bending.

[0008] Li Xu, Jia Ge, Jay H. Patel, and Mable P. Fok: Dual-layer orthogonal fiber Bragg grating mesh based soft sensor for 3-dimensional shape sensing. Optics Express Vol. 25, Issue 20 (2017) 24727-24734 disclose a soft shape sensor for the 3-dimensional measurement of object shape. The proposed sensor is based on dual-layer fiber Bragg grating arrays with an orthogonal mesh structure, enabling bidirectional shape sensing at multiple points.

[0009] Based on the prior art, the invention therefore aims to provide a radiation detector which is flexible in its application and enables simple evaluation of the image data.

[0010] The problem is solved according to the invention by a radiation detector according to claim 1 and a method according to claim 8. Advantageous embodiments of the invention are found in the dependent claims.

[0011] The radiation detector according to the invention comprises at least one radiation detection device. The radiation detection device is configured and designed to convert incident radiation into electrical signals and to make these electrical signals available for further processing. The radiation detection device is particularly planar and has spatial resolution in at least one spatial direction. In some embodiments of the invention, the radiation detection device can have two-dimensional spatial resolution and thus determine the location of incident radiation within predetermined resolution limits. In some embodiments of the invention, the radiation detection device can, in addition to location, also detect further parameters such as the energy and / or the mass and / or the intensity and / or the momentum of incident radiation, so that a two-dimensional image of the incident radiation is generated.In some embodiments of the invention, the radiation can be selected from electromagnetic radiation, for example X-rays or gamma radiation, or visible light. In other embodiments of the invention, the radiation detector can be used to detect particle radiation, for example alpha radiation, beta radiation, or muon radiation.

[0012] Furthermore, the proposed radiation detector includes at least one planar support on which the radiation detection device is mounted. In some embodiments of the invention, the planar support can increase the mechanical stability of the radiation detector and / or prevent damage to the radiation detection device. In some embodiments of the invention, the planar support can be made of metal, plastic, or rubber. In some embodiments of the invention, the planar support can contain or consist of a polymer. In some embodiments of the invention, the planar support can contain or consist of polyethylene.

[0013] The planar support is flexible in at least one spatial direction. This can be achieved, for example, by manufacturing the planar support from a flexible material and / or having a small thickness, so that it is bendable. In particular, the planar support can be elastically deformable and thus reversibly bendable. In other embodiments of the invention, the planar support can be realized as a link belt, i.e., individual planar elements or strips are attached to one another by means of hinges, for example, film hinges, so that relative movement about the connecting axis is possible.

[0014] According to the invention, the planar support includes a shape detection device configured to detect the shape of the support. The shape detection device includes at least one first waveguide in which at least one Bragg grating is incorporated. The first waveguide used as the shape detection device is embedded in the planar support.

[0015] The at least one waveguide can be implemented, for example, as a polymer fiber or as an optical fiber. In other embodiments not covered by the scope of the claims, the at least one waveguide can be manufactured by printing or laser material processing. The waveguide contains at least one core and a cladding surrounding the core, such that an optical signal can propagate in the core due to the difference in refractive index between the core and the cladding.

[0016] According to the invention, the waveguide further comprises at least one Bragg grating. The Bragg grating consists of a plurality of spatial regions or voxels, which have a refractive index that differs from that of their surroundings. At the interfaces of the voxels, incident radiation is partially reflected and partially transmitted, resulting in interference of the incident coherent light. This causes a specific, predefinable wavelength to be reflected and light of a different wavelength to be transmitted. The wavelength of the reflected light depends on the grating constant of the Bragg grating. Deformation of the waveguide or the longitudinal section in which the Bragg grating is embedded leads to stretching or compression and thus to a change in the grating constant. The change in the grating constant can be detected by the change in the wavelength of the reflected or transmitted light.In this way, the curvature of the flexible support at the location of the Bragg grating can be detected. Using multiple waveguides, each containing multiple Bragg gratings, the shape of the planar support of the radiation detector can be determined with high accuracy.

[0017] The radiation detector according to the invention thus allows, for the first time, the shape to be freely selectable within broad limits immediately before a measurement is carried out. This shape can then be determined together with the measurement data from the radiation detection device. The measurement data from the radiation detection device can then be corrected or rectified using the measurement data from the shape detection device. The proposed radiation detector can, in particular, also be used in complex freeform shapes, which are difficult to realize using prior art methods.

[0018] In some embodiments of the invention, the planar support can be flexible in two spatial directions, for example in the form of a thin plastic film. This allows for particularly flexible adaptation to different measurement tasks.

[0019] In some embodiments of the invention, the first waveguide can be embedded in a neutral fiber of the planar support. This prevents the first waveguide from being subjected to impermissible mechanical stresses. Changes in the measured values ​​read from the Bragg gratings can thus be clearly attributed to a change in shape and distinguished from acting mechanical forces or stresses.

[0020] In some embodiments of the invention, the first waveguide can be embedded outside a neutral fiber of the planar support. This can increase the deformation of the first waveguide, thus increasing the sensitivity of the shape detection device.

[0021] According to the invention, the first waveguide is guided in a slidable manner within a cavity of the planar support. This prevents the occurrence of unacceptably high mechanical stresses, allowing the shape of the planar support to be captured with greater accuracy.

[0022] In some embodiments of the invention, the cavity can be shaped complementarily to the outer contour of the first waveguide. This allows the first waveguide to be guided without play, so that it reliably runs in the neutral fiber of the planar support and is nevertheless guided in a sliding manner, taking on the curvature of the support.

[0023] In some embodiments of the invention, the radiation detection device can comprise a plurality of second optical waveguides, which are optionally at least partially equipped with a scintillator. The scintillator can be placed in a cavity of the second waveguide or applied to an outer surface of the second waveguide. Incoming radiation is converted by the scintillator into visible light, which is subsequently propagated in the second waveguide and detected at its end in a manner known per se, for example, by means of a photodiode. By using a plurality of waveguides arranged in parallel, spatial resolution in one spatial direction can be achieved. By using a multilayer, in particular crossed, arrangement of a plurality of second waveguides, the location of a radiation event can be spatially resolved in two spatial directions and thus detected with pinpoint accuracy.By capturing the radiation using the second waveguide, it is possible to avoid directly exposing electronic components to the radiation. This can extend the reliability and / or lifespan of electronic components.

[0024] In some embodiments of the invention, the radiation detector further includes an evaluation unit to which signals from the radiation detection device and the shape detection device can be fed and which is configured to correct the signal errors caused by the curvature of the planar support. This simplifies the application of the radiation detector according to the invention because the user is always presented with a rectified image that is indistinguishable from the image of a flat detector. Since the detection of the actual shape of the radiation detector is automated in the background, the user does not need to concern themselves with the exact positioning or precise shaping of the radiation detector.

[0025] In some embodiments of the invention, the shape of the planar support can be determined by a neural network or by geometric interpolation. To generate training data for a neural network, the planar support can be shaped into a multitude of different forms, which are detected independently of the shape detection device, for example, by camera-based methods. The shape thus detected can be correlated with the optical measurements of the shape detection device, so that, after sufficient training, the shape detection device can reliably determine even previously unknown shapes of the planar support.

[0026] In some embodiments of the invention, the radiation detector can also be used for measurements in hard-to-reach locations by transporting it rolled or folded through an opening to the actual measurement location and unfolding or unrolling it there. It is irrelevant whether the radiation detector actually lies completely flat at the measurement location, since the measured values ​​obtained can be rectified or corrected using the simultaneously recorded shape of the radiation detector.

[0027] In some embodiments of the invention, the radiation detector can be adapted to the shape of a test object. For example, the radiation detector can be placed against or inserted into a test object. For example, in non-destructive material testing, this allows the shape and wall properties of a test object to be simultaneously recorded, or the wall property measurements can be correlated with a location on the surface of the test object.

[0028] In some embodiments of the invention, the radiation detector or the planar support can have a length or width of between approximately 10 cm and approximately 100 cm or between approximately 50 cm and approximately 200 cm. This makes the radiation detector according to the invention equally suitable for applications in medical imaging, quality assurance of manufacturing processes, the investigation of technical equipment after damage, or in archaeology.

[0029] The invention will now be explained in more detail with reference to figures, without limiting the general concept of the invention. This will show Figure 1 shows the radiation detector according to the invention in perspective. Figure 2 shows the radiation detector according to the invention in section. Figure 3 illustrates the cross-section of the radiation detector according to the invention. Figure 4 shows the flexibility of the radiation detector according to the invention. Figure 5 shows the use of the radiation detector according to the invention in a first embodiment. Figure 6 shows the application of the radiation detector according to the invention in a second embodiment.

[0030] Identical components of the invention are provided with the same reference numerals, so that not all details in connection with each figure are described again in full.

[0031] Based on the Figures 1 and 2The proposed radiation detector 1 and its use are explained in more detail. As from Figure 1 and Figure 2 As can be seen, a material sample 55 is examined with the radiation detector 1 according to the invention. The material sample 55 can, for example, be a human or animal body. In other embodiments of the invention, the material sample 55 can contain a technical object, for example, an industrial product, a building structure, a semi-finished product, or any other material known per se, which is to be examined non-destructively with radiation 51 from a radiation source 5.

[0032] The radiation source 5 can be a radioactive source known per se, which emits α-, β-, or γ-radiation. In other embodiments of the invention, the radiation source 5 can be an X-ray tube or a synchrotron radiation source, which emits X-rays. In yet other embodiments of the invention, the radiation source 5 can also emit visible light. In the illustrated embodiment of the method, the material sample 55 is at least partially transparent to the radiation 51.

[0033] The radiation detector 1 is located in the beam path behind the material sample 55, so that transmitted radiation 51 strikes the radiation detector 1. In other embodiments of the invention, the radiation detector 1 can also be arranged on the same side as the radiation source 5, so that the radiation detector 1 detects backscattered radiation.

[0034] The radiation detector 1 includes a radiation detection device 2, which in the illustrated embodiment has two-dimensional spatial resolution. It is therefore a detector designed and intended to detect the location of incident radiation and optionally other parameters, such as intensity or energy.

[0035] In the illustrated embodiment, the radiation detection device comprises a plurality of parallel second waveguides 20, each optionally equipped with a scintillator. The scintillator is designed and configured to convert the incoming radiation 51 into visible light. This visible light propagates in the second waveguides 20 to a corresponding photodetector 25. The photodetector 25 converts the optical signal into an electrical signal, which is subsequently fed to an evaluation unit 13.

[0036] As from Figure 1 As can be seen, the second waveguides 20 are arranged in two layers, with the second waveguides 20 of each layer running parallel to each other and the waveguides of two different layers running orthogonally to each other. In this way, the position can be determined one-dimensionally in each layer. The interaction of both layers results in a pinpoint determination of the location 52 of the interaction.

[0037] The radiation detection device 2 is arranged on a planar support 3, which is flexible in at least one spatial direction. In some embodiments of the invention, the planar support 2 can be flexible in two spatial directions. In this way, the planar support 3, and thus the radiation detection device 2, can be curved, for example, to adapt the radiation detector to an outer or inner contour of the material sample 55. The planar support can consist of a flexible polymer layer to allow sufficient flexibility. The second waveguides 20 of the radiation detection device 2 can be attached to the planar support by means of an embedding material or a potting compound. In some embodiments of the invention, an ethylene-vinyl acetate copolymer or a silicone can be used as the embedding material.

[0038] The curvature of the radiation detector 1 causes a distortion in the image produced by the radiation detection device 2. Therefore, knowledge of the shape of the planar support 3, and thus of the radiation detection device 2, is advantageous for correcting the image captured by the radiation detection device 2. For this purpose, the planar support 3 includes a shape detection device 4. According to the invention, the shape detection device 4 includes a plurality of first waveguides 40, which are embedded in the planar support 3. The waveguides 40 each contain at least one Bragg grating. The grating constant of the Bragg grating changes due to the curvature of the waveguide and thus due to the curvature of the planar support 3. The grating constant of the Bragg grating can, in turn, be determined by measuring the light reflected or transmitted by the Bragg grating.By means of a large number of first waveguides, each containing a plurality of Bragg gratings, the shape of the planar support 3 can be detected with great accuracy and in several spatial directions.

[0039] The data representing the shape of the planar support 3 are also fed to the evaluation unit 13, so that the image distortions caused by the curvature can be corrected there.

[0040] Based on the Figure 3 The structure of the planar support 3 will be explained in more detail. Figure 3 This shows a cross-section through radiation detector 1.

[0041] As from Figure 3As can be seen, the planar support 3 contains a cavity 33 which, when the planar support 3 is curved, extends within the neutral axis of the planar support 3. The first waveguides 40 are slidably mounted in the cavity 33, which can be shaped complementarily to the outer contour of the first waveguides 40, so that they slide within the cavity 33 with minimal stress when the planar support 3 moves. This allows the Bragg grating to detect only the deformation of the planar support 3, without the signals being distorted by unwanted mechanical stresses or temperature changes of the first waveguide 40.

[0042] How Figure 3 This also shows that there is no adhesive layer between the flat carrier 3 and the shape detection device 4, so that the sensitivity of the shape detection device 4 is not negatively affected.

[0043] Out of Figure 4It is again evident that the radiation detector 1 can be bent so that the radiation detection device 2 and the planar support 3 adapt to the shape of an outer surface. At least one transmission channel, for example the optical fibers 20 and 40, serves to transmit the signals from the radiation detection device and the shape detection device to the evaluation unit. The neutral fiber of the planar support remains unchanged.

[0044] Based on the Figure 5 An application example of the radiation detector 1 according to the invention is explained. In the illustrated embodiment, a pipe or pipeline 8 is examined. These pipelines are made of steel or plastic and have an inner diameter between approximately 100 mm and approximately 1300 mm. The pipe 8 can be buried as an underground conduit at a depth of approximately 0.9 m to approximately 1.8 m.

[0045] According to the current state of the art, a planar radiation detector is used to inspect the pipe wall of pipe 8. Often, several planar detectors are combined to form a hexagonal cross-section. However, this approach has the disadvantage that the detector is blind at some detection angles or at least has a reduced resolution.

[0046] The radiation detector according to the invention can be inserted into the interior of a pipe 8 and adapts to the cross-section of the pipe 8. The radiation detection device 2 can then receive radiation, the properties of which change depending on the material properties of the pipe wall. For this purpose, gamma radiation, X-rays, or muon radiation, which naturally occurs in the atmosphere, can be used, for example. For easier signal evaluation, the connecting line 40 or 20 can be routed outside the pipe 8.

[0047] Based on the Figure 6 A second application example will be explained in more detail. Figure 6 Figure 8 also shows a pipeline 8 running in an installation shaft 85. The space between the outer wall of the pipeline 8 and the wall 85 of the installation shaft is limited. Therefore, an investigation with known, flat radiation detectors 2 would not be possible or only with considerable effort.

[0048] The radiation detector 1 according to the invention can adapt to the outer contour of the pipe 8 and thus reliably detect the condition of the pipe wall 8. In this case, too, X-rays, gamma rays, or muon radiation can be used to examine the pipe 8. These radiations change depending on the properties of the pipe wall and are detected by the radiation detector 1. Simultaneously, the shape detection device of the planar support 3 detects the shape of the outer wall of the pipe 8.

[0049] Naturally, the invention is not limited to the embodiments shown. The foregoing description is therefore not to be considered limiting, but rather explanatory. The following claims are to be understood as meaning that a named feature is present in at least one embodiment of the invention. This does not preclude the presence of further features. Where the claims and the foregoing description define "first" and "second" embodiments, this designation serves to distinguish between two similar embodiments without establishing any hierarchy.

[0050] The project that led to this intellectual property right was funded by the European Union’s Horizon 2020 research and innovation program under grant agreement No. 899634.

Claims

1. Radiation detector (1) comprising at least one radiation detection device (2) and at least one flat carrier (3) on which the radiation detection device (2) is mounted, the flat carrier (3) being flexible in at least one spatial direction and containing a shape detection device (4) which is designed to detect the shape of the flat carrier (3), the shape detection device (4) containing at least one first waveguide (40) in which at least one Bragg grating is incorporated, the first waveguide (40) being embedded in the flat carrier (3), characterized in that the first waveguide (40) is guided in a sliding manner in a cavity (33) of the flat carrier (3).

2. Radiation detector according to claim 1, characterized in that the flat carrier (3) is flexible in two spatial directions.

3. Radiation detector according to claim 1 or 2, characterized in that the first waveguide (40) runs outside a neutral fiber of the flat carrier (3).

4. Radiation detector according to any one of claims 1 to 3, characterized in that the cavity (33) is shaped so as to be complementary to the outer contour of the first waveguide (40).

5. Radiation detector according to any one of claims 1 to 4, characterized in that the radiation detection device (2) contains a plurality of second optical waveguides (20) which are at least partially provided with a scintillator.

6. Radiation detector according to any one of claims 1 to 5, further comprising an evaluation device (13) to which signals from the radiation detection device (2) and the shape detection device (4) can be supplied and which is designed to correct the signal errors caused by the curvature of the flat carrier (3).

7. Radiation detector according to any one of claims 1 to 6, characterized in that the radiation detection device (2) is designed to have multiple layers.

8. Method for detecting radiation using a radiation detector (1) with at least one radiation detection device (2) and with at least one flat carrier (3) on which the radiation detection device (2) is mounted, the flat carrier (3) being flexible in at least one spatial direction and containing a shape detection device (4) which is designed to detect the shape of the flat carrier (3), and the shape detection device (4) containing at least one first waveguide (40) in which at least one Bragg grating is incorporated, the first waveguide (40) being embedded in the flat carrier (3), characterized in that the first waveguide (40) is guided in a sliding manner in a cavity (33) of the flat carrier (3).

9. Method according to claim 8, characterized in that the signals of the shape detection device (4) are used to correct the signal errors of the radiation detection device (2) that are caused by the curvature of the flat carrier (3).

10. Method according to any one of claims 8 or 9, characterized in that the shape of the flat carrier is determined by a neural network or by geometric interpolation.

11. Method according to any one of claims 8 to 10, characterized in that the radiation detector (1) is transported in rolled or folded fashion through an opening to the measuring location and unfolded or unrolled at the measuring location.

12. Method according to any one of claims 8 to 10, characterized in that the radiation detector (1) is adapted to the shape of a measurement object (6).

13. Method according to any one of claims 8 to 12, characterized in that the radiation is detected by the radiation detection device (2) in one or two spatial dimensions in a spatially resolved manner.

14. Method according to any one of claims 8 to 13, characterized in that the radiation is selected from gamma radiation and / or X-ray radiation and / or muon radiation.