Device and method for characterizing a fluid flow

Abstract

The invention relates to a device and a method for characterizing a fluid flow guided in a fluid guide, wherein the fluid flow is irradiated with X-rays generated by means of an X-ray source with a target arranged within the fluid guide and an emitter wire surrounding the same, and wherein the X-rays attenuated by the fluid flow are detected by means of a detector device with one or more X-ray detectors.

Description

[0001] The invention relates to a device and a method for characterizing fluid flows using X-rays.

[0002] Characterizing fluid flows is important in many areas of industry and science, for example, to characterize fluid flows with regard to their purity and / or phase composition, or to monitor flow behavior. Methods for characterizing fluid flows using X-rays are known from the prior art. In these methods, X-rays are generated by an X-ray source located outside the flow cross-section, the flow cross-section or fluid flow is irradiated by the X-rays, and the X-rays passing through the fluid flow and being attenuated by it are detected by an X-ray detector located outside the flow cross-section. Based on the detected radiation, the composition of the fluid flow can be determined.Based on the degree of attenuation of the X-ray radiation, conclusions can be drawn about the density distribution present along the radiation path and the fluid flow can be characterized based on this.

[0003] In conventional X-ray methods for characterizing fluid flows, the X-rays must penetrate the entire fluid flow as well as the walls of the surrounding fluid channel or pipe twice. This necessitates high photon energies and / or long integration times to achieve sufficient data or measurement quality. However, higher photon energies negatively impact measurement quality and result in poorer phase contrast and reduced spatial and structural resolution, particularly due to the associated lower dynamic range and increased Compton scattering compared to photoabsorption. Furthermore, higher photon energies require correspondingly more complex radiation protection and shielding measures. Longer integration times, in turn, lead to lower temporal resolution.

[0004] In conventional X-ray methods for characterizing fluid flows, the X-ray radiation travels different path lengths between the source and detector at different measurement positions and / or encounters different material geometries of the surrounding fluid flow, and / or only a portion of the flow cross-section can be irradiated at any given time, meaning that simultaneous radiographic acquisition of the entire flow cross-section is not possible. The presence of different measurement geometries for different measurement positions or paths negatively impacts measurement quality. For example, if only a portion of the flow cross-section is captured at any given time, the resulting image quality becomes inaccurate.When scanning the flow cross-section with a single collimated measuring beam using a source-detector unit, this results in significantly reduced information acquisition or requires, for example, movement of the source-detector unit for more complete information acquisition, which in turn requires a correspondingly complex setup, is associated with lower resolution and requires time-consuming data processing.

[0005] The invention provides a device and a method for characterizing fluid flows using X-rays, which enables uncomplicated and effective characterization of fluid flows with high measurement quality.

[0006] Such a device and such a method are provided by the independent claims. Advantageous embodiments are described in the dependent claims.

[0007] According to one aspect of the invention, a device for characterizing a fluid flow is provided, wherein the device is also referred to as a measuring device or measuring arrangement. The measuring device has a fluid guide for guiding or flowing the fluid flow to be characterized. The fluid guide can also be referred to as a flow path. The fluid guide can, for example, be tubular with a circular cross-section. The measuring device includes an X-ray source with a target and an emitter wire, as well as a detector device with one or more X-ray detectors.

[0008] The fluid flow path has a flow inlet (e.g., an inlet opening) for admitting the fluid flow and a flow outlet (e.g., an outlet opening) for discharging the fluid flow. The fluid flow proceeds from the flow inlet to the flow outlet.

[0009] The target and the emitter wire are arranged within the fluid guide. The target is designed such that it has a rotationally symmetric surface with respect to an axis, which is also referred to as the target axis. The lateral surface of the target thus corresponds to the lateral surface of a (right) circular cylinder. For example, the target can be designed to be rotationally symmetric with respect to the target axis. The target can, for example, be a rod or tube with a circular cross-section. The emitter wire is arranged coaxially around the target with respect to the target axis, i.e., the emitter wire surrounds the target in such a way that it is arranged coaxially with respect to the target axis. The target is thus surrounded by the emitter wire, which runs at a distance from the target but is arranged coaxially with it. The emitter wire can, for example,The emitter wire can be configured as a circular or semi-circular wire loop or as a coil with a circular cross-section. In particular, the emitter wire can be configured as a coil with a circular cross-section, the coil having one or more turns. The emitter wire is arranged coaxially with respect to the target axis; that is, if the emitter wire is configured as a circular or semi-circular wire loop, the associated circular axis (i.e., the axis passing through the center of the associated circle and perpendicular to the plane of the circle) coincides with the target axis, and more generally, if the emitter wire is configured as a coil, the coil axis coincides with the target axis. Thus, the emitter wire is arranged concentrically with respect to the target axis.

[0010] The measuring device is designed to apply an electrical voltage to the emitter wire, causing it to heat up and emit electrons. Therefore, the electrical voltage applied for electron emission is also called the heating voltage, and the emitter wire is also called the heating wire. To apply the heating voltage, the emitter wire is connected at both ends by means of an electrical terminal, which is also referred to as the heating voltage terminal. The emitter wire is arranged equidistant from the target between its two ends, i.e., between the two heating voltage terminals; that is, equidistant from the rotationally symmetric surface of the target. The emitter wire is thus designed and arranged such that it is coaxial with the target, running equidistant from the target between the two heating voltage terminals.The emitter wire can, for example, be made of or contain metal, or it can be made of or contain a metal alloy. The emitter wire preferably consists of a material with a low work function for releasing the electrons. For example, the emitter wire can be made of tungsten lanthanum oxide.

[0011] The measuring device is also designed to apply an electrical voltage between the emitter wire and the target such that the electrons emitted by the emitter wire are accelerated towards the target and decelerated by the target, generating X-rays. The electrical voltage applied between the target and the emitter wire to accelerate the electrons is also called the accelerating voltage. It can be specifically provided that the accelerating voltage is at least 5 kV (5000 volts). The measuring device is designed to apply the accelerating voltage between the emitter wire and the target such that the target has a higher electrical potential than the emitter wire, and the electrons emitted by the emitter wire are thus accelerated towards the target.The target is a solid-state element designed for electron collisions, where the electrons are decelerated, generating X-rays. The target is preferably electrically conductive, for example, by being made of or incorporating electrically conductive material. The target can, for example, consist of a metal or have an X-ray-generating layer made of a metal, where the metal can be, for example, tungsten.

[0012] When the measuring device is operated with a heating voltage applied to the emitter wire and an accelerating voltage applied between the emitter wire and the target, electrons are emitted from the emitter wire, which runs coaxially around the target, and accelerated towards the target. The electrons strike the rotationally symmetrical surface of the target perpendicularly in a radial direction (relative to the target axis). At the point of impact, X-rays emanating from the target surface are emitted in the form of a cone of radiation with its axis running along the respective radial direction, or in the form of a lobe of radiation with its axis running along the respective radial direction. Originating from the target, which is located within the fluid guide, the X-rays pass through the portion of the fluid guide located in the respective beam path and are detected by the detector device.The X-ray detectors of the detector device are designed to detect the X-rays emitted by the target. Based on the detected X-rays, the fluid flow can be characterized.

[0013] For example, the measuring device may include an evaluation device connected to the detector device, designed to characterize the fluid flow based on the X-rays detected by the detector device's X-ray detectors. The evaluation device may thus be specifically designed to read the X-ray detectors and characterize the fluid flow based on the read values.

[0014] By generating the X-rays inside the fluid guide and transmitting them outwards through the guide and the fluid flow within it, the X-rays only need to penetrate a portion of the fluid flow and (if the X-ray detectors are located outside the fluid guide) the boundary wall of the fluid guide only once before detection. This allows for high measurement quality even with relatively low photon energies and relatively short integration times. Lower photon energies of the X-rays used have a positive impact on measurement quality and enable better phase contrast and improved spatial and structural resolution, particularly due to the associated extended dynamic range and the reduction of Compton scattering compared to photoabsorption.Lower photon energies also simplify radiation protection and shielding measures, which promises greater acceptance in application. Shorter integration times, in turn, enable better temporal resolution.

[0015] By arranging the heating wire coaxially around the target and its axis, thus directing electrons radially onto the target surface from different directions, the target within the fluid guide emits X-rays along various radial directions. This allows the surrounding fluid guide and the fluid flow within it to be irradiated simultaneously from multiple directions. Depending on the emitter wire's design, an angular coverage of up to 360° is possible, meaning the entire cross-section of the fluid guide and the fluid flow within it can be irradiated simultaneously.By simultaneously acquiring measurements of the integral attenuation of X-rays for different transmission directions with different azimuth angles relative to the target axis, rapid and straightforward data analysis and flow characterization are possible without additional a priori information. This allows, for example, a direct inference about the flow regime of the fluid flow being characterized from the acquired measurement data. This enables, for example, an in-situ representation of the flow regime, particularly in conjunction with the high measurement rate made possible by the shorter integration times.

[0016] It can be provided, in particular, that the emitter wire has at least one turn extending completely around the target. In this case, the electrons emitted by the emitter wire strike the target or its rotationally symmetric surface from all sides within a closed ring region, causing X-rays to be emitted radially from this ring region, relative to the target axis, covering a 360° azimuth angle range. This enables simultaneous all-around illumination of the fluid guide and the fluid flow within it.

[0017] According to one embodiment, the two heating voltage connections (i.e., the two connections for applying the heating voltage to the emitter wire) extend away from the emitter wire parallel to the target axis. Accordingly, it can be provided that at least the end sections of the two heating voltage connections that contact the emitter wire are arranged parallel to the target axis. Such an arrangement minimizes the influence of the heating voltage connections on the X-ray radiation or its symmetry.

[0018] The fluid guide may be designed to have a central axis, also referred to as the fluid guide's central axis. This central axis runs centrally within the fluid guide. The central axis can be, for example, an axis of symmetry or an approximate axis of symmetry, such as an axis of rotation or an approximate axis of rotation, of the fluid guide or its interior. For instance, the fluid guide may be designed as a hollow cylinder or tube with a circular cross-section; in this case, the central axis is defined by the cylinder or tube axis.

[0019] According to one embodiment, the target is arranged within the fluid guide such that its axis coincides with the central axis of the fluid guide. Accordingly, the target is positioned centrally within the fluid guide with its axis running parallel to the central axis of the fluid guide, and, for example, the longitudinal direction of the target may run parallel to the longitudinal direction of the fluid guide. It may also be arranged, for example, that the target is coaxial with the fluid guide within the fluid guide, so that the target, the emitter wire, and the fluid guide are arranged coaxially with each other.

[0020] By positioning the target centrally to the fluid guide, the variation in measurement geometry and transmission distances for different transmission directions can be reduced, thus enabling higher measurement quality. In the case of a rotationally symmetrical fluid guide (e.g., in the form of a pipe) with the target centrally and coaxially positioned within it, the X-rays emitted radially outwards from the target exhibit the same measurement geometry with respect to the fluid guide and the same distance to reach or penetrate the boundary wall of the fluid guide in all radial directions. This allows for symmetrical transmission across the entire fluid guide cross-section, resulting in a significant increase in measurement quality.

[0021] According to another embodiment, the target is arranged in the fluid guide such that the target axis does not coincide with the central axis of the fluid guide, but rather intersects the central axis of the fluid guide at an angle (where the angle is not zero). The target and the emitter wire are preferably arranged such that the emitter wire is positioned centrally along the direction defined by the target axis with respect to the point of intersection of the target axis and the central axis (i.e., the emitter wire is preferably arranged such that it is intersected by the plane perpendicular to the target axis and passing through the point of intersection of the two axes).

[0022] This design enables at least improved measurement symmetry insofar as the same material geometry of the enclosing fluid guide is present for each opposite direction of transmission, while also allowing greater freedom in the arrangement of the target and the X-ray detectors and enabling simpler fluid-tight enclosure of the target with the emitter wire.

[0023] The X-ray detectors of the detector device are preferably arranged outside the fluid guide, e.g., on the outside of the fluid guide (i.e., on the side or outer surface of the fluid guide facing away from the fluid flow). However, it is also possible for the X-ray detectors to be integrated into the fluid guide (e.g., integrated into the boundary wall of the fluid guide) or arranged inside the fluid guide (e.g., on the side or inner surface of the fluid guide facing the fluid flow).

[0024] According to one embodiment, the detector device comprises one or more X-ray detectors arranged centrally with respect to the emitter wire along the direction defined by the target axis. Accordingly, the detector device may be provided with one or more X-ray detectors, each arranged such that it is intersected by a plane perpendicular to the target axis and passing through the emitter wire. For example, it may be provided that all X-ray detectors of the detector device are arranged centrally with respect to the emitter wire along the direction defined by the target axis.

[0025] This design can contribute to an increase in the symmetry of the measurement geometries or transmission geometries available for different transmission directions and thus to an increased measurement quality.

[0026] It can be provided, in particular, that the target is arranged in the fluid guide such that the target axis coincides with the central axis of the fluid guide, and that the detector device comprises several X-ray detectors arranged at different positions along a circle arranged concentrically and coaxially with respect to the target axis and the emitter wire, wherein the multiple X-ray detectors are arranged centrally with respect to the emitter wire along the direction defined by the target axis. Accordingly, it can be provided that the detector device comprises several X-ray detectors arranged in a circular detector ring such that the detector ring is arranged concentrically or coaxially with respect to the target axis, wherein the detector ring, and thus each X-ray detector of the detector ring, is arranged in a plane perpendicular to the target axis and through the emitter wire.is cut off from this plane.

[0027] Furthermore, it can be provided, for example, that the target is arranged in the fluid guide such that the target axis intersects the central axis of the fluid guide at an angle, and that the detector device has several X-ray detectors arranged at different positions along an ellipse concentrically and coaxially with respect to the target axis and the emitter wire, wherein the several X-ray detectors are arranged centrally with respect to the emitter wire along the direction defined by the target axis. Accordingly, it can be provided that the detector device has several X-ray detectors arranged in an elliptical detector ring such that the detector ring is arranged concentrically or coaxially with respect to the target axis, wherein the detector ring, and thus each X-ray detector of the detector ring, is arranged in a plane perpendicular to the target axis and through the emitter wire.is cut off from this plane.

[0028] Alternatively or additionally, the detector device may include one or more X-ray detectors that are not arranged centrally with respect to the emitter wire along the direction defined by the target axis, but rather offset from the emitter wire. Accordingly, the detector device may include one or more X-ray detectors, each arranged such that it is not intersected by a plane perpendicular to the target axis and through the emitter wire. For example, all X-ray detectors of the detector device may be arranged offset from the emitter wire along the direction defined by the target axis.

[0029] This design can in particular enable an arrangement such that the emitter wire lies outside the beam path of the X-ray radiation, which is detected by means of the X-ray detectors arranged with an offset relative to the emitter wire, which can contribute to increased measurement quality.

[0030] It can be provided, in particular, that the target is arranged in the fluid guide such that the target axis coincides with the central axis, and that the detector device comprises several X-ray detectors arranged at different positions along a circle that is coaxial to the target axis with an offset relative to the emitter wire along the direction defined by the target axis. Accordingly, it can be provided that the detector device comprises several X-ray detectors arranged to form a circular detector ring such that the detector ring is coaxial to the target axis, wherein the detector ring, and thus each X-ray detector of the detector ring, is arranged in or intersected by a plane perpendicular to the target axis and not passing through the emitter wire.

[0031] Furthermore, it can be provided, for example, that the target is arranged in the fluid guide such that the target axis intersects the fluid guide's central axis at an angle, and that the detector device comprises several X-ray detectors arranged at different positions along a circle that is coaxial with the fluid guide's central axis, wherein at least one or at least some of these X-ray detectors are arranged along the direction defined by the target axis with an offset relative to the emitter wire. The circle preferably lies in a plane that is perpendicular to the fluid guide's central axis and passes through the intersection of the central axis with the target axis.Accordingly, if the target axis is arranged at an angle to the fluid guide central axis, the detector device may have several X-ray detectors arranged in a circular detector ring such that the detector ring is coaxial to the central axis, wherein the detector ring, and thus each X-ray detector of the detector ring, is arranged in or intersected by a plane perpendicular to the central axis and through the intersection of the central axis with the target axis.

[0032] Due to the cone-shaped or club-shaped emission of X-rays from the target surface, X-rays can also be detected and fluid flow characterized using X-ray detectors arranged along the direction defined by the target axis with an offset relative to the emitter wire.

[0033] The X-ray detectors of each circular or elliptical detector ring can be arranged outside the fluid guide or integrated into it. In particular, the X-ray detectors of each circular or elliptical detector ring can be arranged outside the fluid guide, for example, on the outer surface of the fluid guide's boundary wall. It is preferably the case that the X-ray detectors of each circular or elliptical detector ring are arranged equidistantly, i.e., the distance between two adjacent X-ray detectors of each detector ring is the same for each pair of adjacent X-ray detectors.It can further be provided that the X-ray detectors of a respective detector ring form a closed or nearly closed detector ring, such that the detector ring is covered with X-ray detectors along its entire or nearly entire circumference, thereby enabling simultaneous detection of the integral radiation attenuation over an azimuth angle range of 360° and supporting straightforward flow characterization with high spatial resolution. Furthermore, it can be provided that the detector device comprises multiple X-ray detectors arranged in a common plane, for example, in the form of the circular and elliptical detector rings described above. It can also be provided, for example, that all X-ray detectors of the detector device are arranged in a common plane.

[0034] The target and emitter wire are arranged within the fluid path or in the cross-section of the fluid path and the fluid flow within it. In particular, the target and emitter wire may be enclosed within the fluid path by a housing, also referred to as the radiation source housing. It may also be provided that, in addition to the target and emitter wire, further elements of the X-ray source are arranged within the housing, e.g., electrical conductors and connections for applying voltage. The target and emitter wire are enclosed by the radiation source housing in a fluid-tight manner and shielded from the fluid flow, so that there is no direct physical contact between the elements of the X-ray source arranged within the housing (especially the target and the emitter wire) and the fluid flow.Accordingly, the measuring device may be provided with a housing arranged within the fluid path, with the target and the emitter wire arranged within this housing. In particular, it may be provided that the target and the emitter wire are arranged within an evacuable or evacuated section of the housing, in which a vacuum (e.g., a high vacuum with a maximum pressure of 10 bar) is maintained. -8 mbar or an ultra-high vacuum with a maximum pressure of 10 -11 mbar) prevails or can be generated.

[0035] According to one embodiment, the target and the emitter wire are arranged in a section of the radiation source housing that is rotationally symmetrical with respect to the target axis. This allows for a rotationally symmetrical transmission geometry for the X-rays emitted by the target with respect to the housing, whereby, for example, the X-rays emitted radially outwards from the target strike the housing wall at the same angle in all radial directions on their way to the X-ray detectors. Such a rotationally symmetrical transmission geometry with respect to the housing can also contribute to high measurement quality.Accordingly, it can be provided in particular that the target and the emitter wire are arranged in a rotationally symmetric section of the radiation source housing with respect to the target axis, wherein the rotationally symmetric section and the target are designed and arranged such that the angle at which the X-ray radiation traveling from the target to a respective X-ray detector hits and intersects the rotationally symmetric housing section or its wall is the same for all X-ray detectors of the detector device.

[0036] According to this embodiment, it is also preferable that the fluid guide is rotationally symmetrical with respect to a central axis, and that the target is arranged in the fluid guide such that the target axis coincides with the central axis. The resulting increase in measurement symmetry enables a further improvement in measurement quality.

[0037] According to one embodiment, the measuring device for applying the heating voltage to the emitter wire and the accelerating voltage between the target and the emitter wire is configured such that the heating voltage and the accelerating voltage are relative to a common electrical reference potential, which can be, for example, the ground potential (also referred to as earth potential). This allows for a straightforward and effective application of the heating voltage and the accelerating voltage, and in particular, the power supply for providing the heating voltage can be kept separate from the high-voltage potential for providing the accelerating voltage, thus enabling a simpler technical implementation and smaller insulation distances.

[0038] For example, the measuring device for applying the heating voltage to the emitter wire may be configured such that one of the two heating voltage terminals is supplied with the common reference potential, and the other heating voltage terminal is supplied with an electrical potential that is lower or higher than the reference potential (also referred to as the heating potential). Furthermore, the measuring device for applying the accelerating voltage between the target and the emitter wire may be configured such that the target is supplied with an electrical potential that is higher than the reference potential (also referred to as the accelerating potential).Accordingly, the heating voltage corresponds to the potential difference between the reference potential and the heating potential, and the accelerating voltage corresponds to the potential difference between the reference potential and the accelerating potential. The magnitude of the accelerating voltage is greater than the magnitude of the heating voltage; in particular, the heating voltage is typically a few volts (e.g., a maximum of 12 volts), whereas the accelerating voltage is, for example, at least 5000 volts.

[0039] According to one embodiment, the measuring device is designed to apply the common reference potential to the fluid guide. By applying the reference potential (in particular, the ground potential) to the fluid guide, contact protection and personal safety can be easily ensured. According to this embodiment, it is preferably provided that the fluid guide is electrically conductive, e.g., made of an electrically conductive material. Furthermore, it can be provided that the radiation source housing is electrically conductive, e.g., made of an electrically conductive material.

[0040] Accordingly, it can be provided, in particular, that the measuring device for applying the heating voltage to the emitter wire and for applying the accelerating voltage between the target and the emitter wire is configured such that one of the two heating voltage connections is supplied with the common reference potential, the other of the two heating voltage connections is supplied with an electrical heating potential that is smaller or larger than the reference potential, the fluid guide is supplied with the common reference potential, and the target is supplied with an electrical accelerating potential that is larger than the reference potential. This can, for example,This can be realized by having a voltage source with a first terminal, a second terminal, and a third terminal, wherein the reference potential is provided at the first terminal, the heating potential is provided at the second terminal, and the acceleration potential is provided at the third terminal. In this realization, one of the two heating voltage terminals and the fluid guide are electrically connected to the first terminal, the other of the two heating voltage terminals is electrically connected to the second terminal, and the target is electrically connected to the third terminal. The magnitude of the potential difference between the reference potential and the heating potential is, as explained, smaller than the magnitude of the potential difference between the reference potential and the acceleration potential.

[0041] The measuring device may be provided with a heat exchanger, wherein a first section of the heat exchanger is in thermal contact with the target, and wherein a second section of the heat exchanger is connected to a cooling device. Accordingly, the heat generated at the target can be transferred to the cooling device via the heat exchanger and dissipated by the cooling device. The cooling device is preferably arranged outside the fluid path. For example, the heat exchanger may be routed out of the fluid path via the radiation source housing. The heat exchanger may, for example, be a heat pipe.

[0042] According to one embodiment, the heat exchanger is electrically conductive (e.g., by having or being made of electrically conductive material), and the first section of the heat exchanger is arranged in thermal and electrical contact with the target. The target can be arranged in thermal and electrical contact with the first section of the heat exchanger, for example, by means of a contact element made of an electrically and thermally conductive material or by means of direct physical contact with the heat exchanger.

[0043] According to this embodiment, the measuring device for applying the acceleration voltage between the target and the emitter wire can be configured by subjecting the (electrically conductive and electrically contacted) heat exchanger to an electrical potential positive relative to the common electrical reference potential. Similarly, the target can be subjected to the acceleration potential by subjecting the heat exchanger to the acceleration potential. Furthermore, this embodiment allows, in particular, for the fluid guide to be subjected to the common reference potential. This enables, in particular, a straightforward design of the measuring device and a simple application of the acceleration voltage while simultaneously ensuring safety from contact and / or personal protection.

[0044] According to one embodiment, the target is arranged in an electrically insulated manner relative to the fluid guide and is therefore not electrically conductive to it. In particular, the target can be arranged in an electrically insulated manner relative to the radiation source housing. This can be achieved, for example, by mounting the target and, if applicable, the heat exchanger within the fluid guide or within the radiation source housing, respectively, using retaining elements made of electrically insulating material. This enables the effective acceleration of the electrons emitted by the emitter wire onto the target.

[0045] The measuring device may also include a collimation device with one or more collimator elements for collimating the X-rays emitted by the target. The collimator elements serve to spatially confine the X-rays.

[0046] It is particularly possible for the collimator elements to be arranged within the fluid guide. This allows for effective limitation of the X-ray radiation even before it exits the fluid guide. It is preferred that the collimator elements be arranged within the radiation source housing. This enables collimation of the X-ray radiation without additional influence on the flow by the collimator elements.

[0047] Each collimator element can, for example, be designed as a collimator ring. It can be provided, for example, that the detector device has several X-ray detectors arranged in or intersected by a common plane, and that the collimator device has a circular collimator ring on each side of the common plane, its circular surface parallel to the plane and positioned at a distance from the plane. If the common plane is perpendicular to the target axis, i.e., the corresponding detector ring lies within a plane perpendicular to the target axis, the collimator rings are preferably arranged concentrically or coaxially to the target axis. If the common plane is perpendicular to the central axis of the fluid guide, i.e.,Since the corresponding detector ring lies within a plane perpendicular to the central axis of the fluid guide, the collimator rings are preferably arranged concentrically or coaxially to the central axis of the fluid guide. The configurations described enable effective limitation of the X-ray radiation to the detection-active areas and minimize parasitic scatter radiation.

[0048] According to a further aspect of the invention, a method for characterizing a fluid flow is provided, wherein the method is also referred to as a measuring method. The features described above with reference to the measuring device apply analogously to the measuring method, so that in the following only the corresponding embodiments of the measuring method will be briefly discussed, and reference is made to the corresponding explanations regarding the measuring device.

[0049] According to the measurement method, the fluid flow to be characterized is guided through a fluid guide. X-rays are generated by means of an X-ray source with a target and an emitter wire, and the fluid flow is irradiated with this X-ray radiation, the target and the emitter wire being arranged within the fluid guide. The target has a surface rotationally symmetric with respect to a target axis, and the emitter wire is arranged coaxially around the target axis. The X-rays are generated by applying an electrical heating voltage to the emitter wire such that electrons are emitted from the emitter wire, and by applying an electrical accelerating voltage between the emitter wire and the target such that the emitted electrons are accelerated onto the target and decelerated by the target, thereby generating the X-rays.The X-ray radiation, weakened by the fluid flow through which it is irradiated, is detected by means of a detector device with one or more X-ray detectors.

[0050] Embodiments of this method - in particular with regard to the design and arrangement of the target, the emitter wire and the X-ray detectors as well as with regard to the voltage application to the target and the emitter wire - are described in the corresponding description of the measuring device.

[0051] The invention is explained below with reference to exemplary embodiments and the accompanying schematic figures. The figures show, among other things, specific embodiments for realizing the invention. In addition to the embodiments shown and described in the figures, further embodiments exist. Structural and / or logical modifications to the embodiments shown and explained in the figures are possible without deviating from the claimed subject matter. In particular, features of the embodiments shown and explained in the figures can be combined with one another, unless otherwise indicated by the context. Directional terms such as "front," "back," "bottom," "top," etc., are used with reference to the orientation of the described figures. The elements and structures shown in the figures are not necessarily drawn to scale with respect to one another.Identical reference symbols refer to identical or corresponding elements, structures, and features. Fig. Figure 1 shows a measuring device according to one embodiment. Fig. Figure 2 shows a measuring device according to a further embodiment. Fig. Figure 3 shows a measuring device according to a further embodiment. Fig. Figure 4 shows a measuring device according to a further embodiment.

[0052] Fig. Figure 1 shows a measuring device 1 according to an embodiment when performing a measuring procedure according to an embodiment. Fig. Figure 1 shows the measuring device 1 when characterizing a fluid flow 3, wherein the fluid flow and its flow direction are shown in Fig. Figure 1 is illustrated by arrow 3. The measuring device 1 has a fluid guide 5, which is tubular with a circular cross-section and thus functions as a pipe with a circular cross-section. The fluid guide has a flow inlet 7 and a flow outlet 9, wherein the fluid flow 3 enters the fluid guide 5 through the flow inlet 7, flows through the fluid guide 5 to the flow outlet 9, and exits the fluid guide 5 through the flow outlet. The tubular fluid guide 5 has a central axis 11, which is also referred to as the fluid guide central axis 11. In this case, the fluid guide central axis 11 is defined by the axis of symmetry or tube axis of the tubular fluid guide 5. The fluid guide 5 is made of an electrically conductive material (e.g., a metallic material) and is therefore electrically conductive.

[0053] The measuring device 1 comprises an X-ray source 13 with a target 15 and an emitter wire 17. The target 15 and the emitter wire 17 are arranged within the fluid guide 5.

[0054] The target 15 has a rotationally symmetric surface with respect to a target axis 19, wherein in the embodiment according to Fig. 1. The target axis 19 coincides with or is identical to the fluid guide central axis 11. The target 15 is, for example, designed as a rod with a circular cross-section that is rotationally symmetrical with respect to the target axis 19. The target 15 consists of a metallic material, in this example tungsten.

[0055] When executed according to Fig. In one case, the emitter wire 17 is configured as a circular wire loop arranged coaxially to the target axis 19, such that the emitter wire 17 runs around or surrounds the target 15. Alternatively, the emitter wire 17 can be configured as a coil with a circular cross-section, the coil being arranged coaxially to the target axis 19 and running around or surrounding the target 15. The emitter wire 17 is made of a metallic material, in this example tungsten lanthanum oxide.

[0056] The target 15 and the emitter wire 17 are surrounded within the fluid guide 5 by a housing 21, which is also referred to as the radiation source housing 21. The radiation source housing 21 is evacuated, so that a vacuum exists inside it (e.g., an ultra-high vacuum with a maximum pressure of 10 -11 mbar). The radiation source housing 21 of the design according to Fig. 1 is rotationally symmetric with respect to the target axis 19. The radiation source housing 21 is made of an electrically conductive material and is therefore electrically conductive.

[0057] The target 15 is electrically isolated from the radiation source housing 21 and from the fluid guide 5. This can be achieved, for example, by mounting the target 15 inside the radiation source housing 21 and thus inside the fluid guide 5 using retaining elements (not shown) made of electrically insulating material.

[0058] The measuring device 1 is designed to apply an electrical heating voltage to the emitter wire 17. For this purpose, the measuring device 1 has two heating voltage connections 23, 25, wherein the first heating voltage connection 23 contacts one end of the emitter wire 17 or the circular wire loop 17, and wherein the second heating voltage connection 25 contacts the other end of the emitter wire 17 or the circular wire loop 17. Each of the two heating voltage connections 23, 25 extends from the emitter wire 17 parallel to the target axis 19, with the end section of each heating voltage connection 23, 25 that contacts the emitter wire 17 also being parallel to the target axis 19. The measuring device 1 is also designed to apply an electrical accelerating voltage between the target 15 and the emitter wire 17.For this purpose, the measuring device 1 has an acceleration voltage connection 27 which contacts the target 15.

[0059] The measuring device 1 is configured to supply the emitter wire 17 with the heating voltage and to apply the accelerating voltage between the target 15 and the emitter wire 17 such that the heating voltage and the accelerating voltage are present relative to a common electrical reference potential, the reference potential being, for example, the ground potential (also referred to as earth potential). For this purpose, the first heating voltage terminal 23 is connected to the reference potential. In the embodiment according to Fig. 1. The first heating voltage connection 23 is connected to the reference potential by electrically connecting the first heating voltage connection 23 to the radiation source housing 21 and applying the reference potential (ground potential) to the radiation source housing 21 (in Fig. 1. The radiation source housing 21 is marked by means of the symbol for mass or earth connected to it. For example, it may be provided that the radiation source housing 21 is exposed to the reference potential (ground potential) by electrically connecting the radiation source housing 21 to the fluid guide 5 and applying the reference potential to the fluid guide 5 (in Fig. 1 (marked by means of the symbol for mass or earth connected to the fluid guide 5). The second heating voltage connection 25 is connected to a heating potential U H connected, whereby the heating potential U HThis can be an electrical potential that is smaller or larger than the reference potential. Furthermore, the accelerating voltage connection 27 is connected to an accelerating potential U. B connected, whereby the acceleration potential U B is greater than the reference potential. For this purpose, the measuring device can, for example, have an electrical voltage source whose outputs are connected electrically to the respective voltage terminals or to the radiation source housing 21 or the fluid guide 5.

[0060] It may be provided, for example, that the measuring device 1 is used to provide the reference potential, the heating potential U H and the acceleration potential U B a bipolar DC voltage source (in Fig. (1 not shown). A bipolar DC voltage source is an electrical voltage source that provides both a positive and a negative voltage, relative to a common reference or ground potential. The bipolar DC voltage source has a first terminal to provide the electrical reference potential, also known as ground potential. The bipolar DC voltage source has a second terminal to provide an electrical potential higher relative to the reference potential, also known as the positive terminal, and the acceleration potential U. B This corresponds to the bipolar DC voltage source. It also has a third terminal for providing an electrical potential that is smaller relative to the reference potential, also known as the negative terminal, and corresponds to the heating potential U. HThis corresponds to the accelerating voltage, which corresponds to the potential difference between the first and second terminals of the bipolar DC voltage source, and the heating voltage corresponds to the potential difference between the first and third terminals of the bipolar DC voltage source.

[0061] The magnitude of the acceleration potential U B is significantly greater than the amount of the heating potential U H : |U B | >> |U H |, so that the accelerating voltage is significantly higher than the heating voltage. For example, it can be specified that the accelerating voltage is at least 5000 V, and that the heating voltage is a maximum of 12 V.

[0062] With a heating voltage applied to the emitter wire 17 and an accelerating voltage applied between the emitter wire 17 and the target 15, electrons are emitted from the emitter wire 17, which runs coaxially around the target 15, and accelerated towards the target 15. The electrons strike the target 15 in a radial direction with respect to the target axis 19, emitting X-rays 29 from the target surface at the point of impact in the form of a cone or lobe of radiation with a cone or lobe axis extending along the respective radial direction (in Fig. 1 illustrated by the two arrows 29 running along two exemplary radial directions. The X-ray radiation 29 emanating from the target 15 passes through the part of the fluid guide 5 and the fluid flow 3 located in the respective beam path.

[0063] The measuring device 1 has a detector device with several X-ray detectors 31. The X-ray detectors 31 are arranged outside the fluid guide 5, with each of the X-ray detectors 31 being arranged on the outside of the fluid guide 5 (i.e., on the side or outer surface of the wall of the fluid guide 5 facing away from the fluid flow 3). In the embodiment according to Fig. 1 The detector device has several X-ray detectors 31, all of which are arranged centrally with respect to the emitter wire 17 along the direction defined by the target axis 19. In the embodiment according to Fig. 1. Thus, all X-ray detectors 31 are arranged such that they are intersected by a plane perpendicular to the target axis 19 and through the emitter wire 17, this plane also being perpendicular to the fluid guide central axis 11. The X-ray detectors 31 are arranged at different positions along a circle concentrically and coaxially to the target axis 19 and the emitter wire 17, forming a circular detector ring.

[0064] Starting from the target 17 located within the fluid guide 5, the X-ray radiation 29 passes through the respective part of the fluid flow 3 and the fluid guide 5 located in the respective beam path and is attenuated depending on the material through which it passes. The attenuated X-ray radiation is detected by the X-ray detectors 31. The measuring device 1 is designed (e.g., by means of an evaluation device not shown) to characterize the fluid flow 3 based on the values ​​detected by the X-ray detectors 31.

[0065] The measuring device 1 has a collimation device with two collimator elements 32a, 32b for collimating the X-ray radiation 29 emitted by the target 15. Each of the two collimator elements 32a, 32b is designed as a circular collimator ring. Each of the two collimator elements 32a, 32b is arranged within the radiation source housing 21. The two collimator rings 32a, 32b are arranged coaxially to the target axis 19 on both sides of the emitter wire 17.

[0066] Fig. Figure 2 shows a measuring device 1a according to a further embodiment for characterizing a fluid flow 3. In contrast to the measuring device 1 according to Fig. 1 are in the measuring device 1a according to Fig. 2. All X-ray detectors 31 of the detector device are not arranged centrally with respect to the emitter wire 17 along the direction defined by the target axis 19, but rather with an offset with respect to the emitter wire 17. In the embodiment according to Fig. 2. Thus, all X-ray detectors 31 are arranged such that they are not intersected by a plane 33 extending perpendicular to the target axis 19 and through the emitter wire 17. The X-ray detectors 31 are arranged at different positions along a circle forming a circular detector ring. This circle is coaxial to the target axis 19 with an offset relative to the emitter wire 17, in the direction defined by the target axis 19. In the embodiment according to Fig. 2 the x-ray detectors 31 are thus arranged in a plane 34 perpendicular to the target axis 19 (and perpendicular to the fluid guide central axis 11), which is arranged along the direction specified by the target axis 19 with an offset with respect to the emitter wire 17 and thus does not pass through the emitter wire 17.

[0067] In contrast to measuring device 1 according to Fig. 1, in which essentially the portion of the X-ray radiation emanating perpendicularly from the surface of the target 15 is used to characterize the fluid flow, is carried out in the measuring device 1a according to Fig. 2. A portion of the X-ray radiation propagating at an angle to the surface normal of the lateral surface is used to characterize the fluid flow. Furthermore, the measuring device 1a is designed according to Fig. 2 without a collimation device (although a collimation device for collimating the X-rays can alternatively be provided here as well). Otherwise, the design and operation of the measuring device 1a correspond to Fig. 2 and the corresponding measuring method according to the measuring device 1 Fig. 1, so that in this regard reference is made to the explanations relating to the Fig. 1 is referred to.

[0068] Fig. Figure 3 shows a measuring device 1b according to a further embodiment for characterizing a fluid flow 3.

[0069] In contrast to the measuring devices 1 and 1' according to the Fig. 1 or 2 is in the measuring device 1b according to Fig. 3. The target 15 is arranged within the fluid guide 5 such that the target axis 19 intersects the fluid guide's central axis 11 at an angle (and does not coincide with the fluid guide's central axis 11). The target 15 and the emitter wire 17 are arranged such that the emitter wire 17 is positioned centrally along the direction defined by the target axis 19 with respect to the intersection of the target axis 19 and the fluid guide's central axis 11. The emitter wire 11 is thus arranged such that it is intersected by the plane 35, which runs perpendicular to the target axis 19 and through the intersection of the two axes 11 and 19.

[0070] In the case of measuring device 1b according to Fig. 3. The radiation source housing 21 is designed as a hollow cylindrical or finger-like, inwardly formed bulge of the fluid guide 5 or the wall of the fluid guide 5. In particular, it can be provided that the radiation source housing 21 is integrally formed with the fluid guide 5, i.e., that the radiation source housing 21 and the fluid guide 5 are integrally formed together as a single component. The target 15 and the emitter wire 17 are arranged in a section of the radiation source housing 21 that is rotationally symmetrical with respect to the target axis 19. The radiation source housing 21 is evacuated, so that a vacuum exists within it (e.g., an ultra-high vacuum with a maximum pressure of 10). -11 mbar). For this purpose, the radiation source housing 21 can be vacuum-tightly sealed or closed, for example, by means of a closure 37.

[0071] The detector device of the measuring device 1b according to Fig. 3 has several first X-ray detectors 31a and several second X-ray detectors 31b.

[0072] The first X-ray detectors 31a are arranged in, or intersected by, a plane 35 perpendicular to the target axis 19 and through the emitter wire 17. The plane 35 runs at an angle to the central axis 11 of the fluid guide and through the intersection point between the central axis 11 of the fluid guide and the target axis 19. The first X-ray detectors 31a are thus arranged centrally with respect to the emitter wire 17 along the direction defined by the target axis 19. The X-ray detectors 31a are arranged on the outside of the fluid guide 5, forming an elliptical detector ring, at different positions along an ellipse that is concentric and coaxial with the target axis 19 and the emitter wire 17.

[0073] The second X-ray detectors 31b are arranged in or intersected by a plane 39 perpendicular to the central axis 11 of the fluid guide, the plane 39 passing at an angle to the target axis 19 through the intersection of the two axes 11 and 19. The second X-ray detectors 31b are arranged on the outside of the fluid guide 5 in a circular detector ring at different positions along a circle coaxial with the central axis 11 of the fluid guide, with some or all of the second X-ray detectors 31b being offset from the emitter wire 17 along the direction defined by the target axis 19.

[0074] In the case of measuring device 1b according to Fig. 3 The radiation source housing 21 is integrally formed with the fluid guide 5, wherein the radiation source housing 21 and the fluid guide 5 are made of an electrically conductive material. In the embodiment according to Fig. 3. To apply the heating voltage and the accelerating voltage, the fluid guide 5 is subjected to the reference potential (ground potential), so that the radiation source housing 21 is also subjected to the reference potential.

[0075] For the sake of clarity, in Fig. 3. The representation of the X-ray radiation emitted by target 15 is omitted. The measuring device 1b according to Fig. Figure 3 is shown as an example without a collimation device (although an alternative collimation device for collimating the X-ray radiation can also be provided here).

[0076] Furthermore, the design and operation of the measuring device 1b correspond to Fig. 3 and the corresponding measuring method, those of the measuring devices 1 and 1a according to the Fig. 1 or 2, so that in this regard reference is made to the explanations with reference to the Fig. 1 and Fig. 2 is referred to.

[0077] Fig. Figure 4 shows a measuring device 1c according to a further embodiment for characterizing a fluid flow 3.

[0078] In the case of measuring device 1c according to Fig. 4 The emitter wire 17 is designed as a coil with a circular cross-section, the coil having several turns. The coil is arranged coaxially with respect to the target axis 19 to the target 15, such that the coil axis coincides with the target axis 19. The target 15 is arranged within the fluid guide 5 such that the target axis 19 coincides with the central axis 11 of the fluid guide.

[0079] In the embodiment according to Fig. 4 The radiation source housing 21 is integrally formed with the fluid guide 5, wherein the target 15 and the emitter wire 17 are arranged in a section of the radiation source housing 21 that is rotationally symmetrical with respect to the target axis 19. All X-ray detectors 31 of the detector device are arranged centrally with respect to the emitter wire 17 along the direction defined by the target axis 19. In the embodiment according to Fig. 4. Thus, all X-ray detectors 31 are arranged such that they are intersected by a plane perpendicular to the target axis 19 and centrally through the coil or emitter wire 17, this plane also being perpendicular to the fluid guide's central axis 11. The X-ray detectors 31 are arranged on the outside of the fluid guide 5 in a circular detector ring at different positions along a circle that is concentric and coaxial with the target axis 19 and with the coil acting as the emitter wire 17.

[0080] The measuring device 1c according to Fig. The device 4 has a heat exchanger 41, which is designed, for example, as a so-called heat pipe. The heat exchanger 41 consists of an electrically conductive material (e.g., a metallic material) and is therefore electrically conductive.

[0081] The heat exchanger 41 is arranged in thermal and electrical contact with the target 15 by means of a contact element 43 made of an electrically and thermally conductive material (e.g., a metallic material), such that the first end section of the heat exchanger 41, located inside the radiation source housing 21, and the target 15 are in physical contact with the contact element 43. The heat exchanger 41 extends through the radiation source housing 21 and out of the fluid guide 5, with the second end section of the heat exchanger 41, located outside the radiation source housing 21 and outside the fluid guide 5, being connected to a cooling device 45.

[0082] The target 15 is electrically isolated from the radiation source housing 21 and from the fluid guide 5 by means of retaining elements 47 made of electrically insulating material within the radiation source housing 21 and thus within the fluid guide 5.

[0083] The measuring device 1c according to Fig. 4 features a bipolar DC voltage source 49 for providing the heating voltage and the accelerating voltage.

[0084] The bipolar DC voltage source 49 has a first terminal 51 at which an electrical ground potential is provided as a reference potential, and which is also referred to as ground terminal 51 (and in Fig. 4 (marked with the symbol for ground or earth for illustration). The voltage source 49 has a second terminal 53, at which a higher or positive electrical potential relative to the ground potential is provided, and which is also referred to as the positive terminal 53 (and in Fig. (1 is marked with the plus symbol for illustration). The electrical potential provided at the positive terminal 53 corresponds to the acceleration potential U. B The voltage source 49 also has a third terminal 55, at which a smaller or negative electrical potential relative to the ground potential is provided, and which is also referred to as the negative terminal 55 (and in Fig. (1 is marked with the minus symbol for illustration). The electrical potential provided at the negative terminal 55 corresponds to the heating potential U. H .

[0085] The ground terminal 51 is electrically connected to the first heating voltage terminal 23 and the fluid guide 5, so that the first heating voltage terminal 23 and the fluid guide 5 are supplied with the electrical ground potential as a reference potential. The positive terminal 53 is electrically connected to the heat exchanger 41, so that the heat exchanger 41, the contact element 43, and the target 15 are supplied with the acceleration potential U (positive relative to the ground potential). B The negative terminal 55 is electrically connected to the second heating voltage terminal 25, so that the second heating voltage terminal is connected to the heating voltage potential U, which is negative relative to ground potential. H is charged.

[0086] Furthermore, the design and operation of the measuring device 1c correspond to Fig. 4 and the corresponding measuring method, those of the measuring device 1 according to Fig. 1, so that in this regard reference is made to the explanations with reference to Fig. 1 is referred to.

[0087] Regarding the Fig. 1, Fig. 2, Fig. 3 to Fig. In the detector rings described in section 4, it can be provided in particular that the X-ray detectors 31 of each circular or elliptical detector ring are arranged equidistantly, i.e., the distance between two adjacent X-ray detectors 31 of each detector ring is the same for each pair of adjacent X-ray detectors. It can further be provided that the X-ray detectors 31 of each detector ring form a closed or nearly closed detector ring, such that the detector ring is occupied by X-ray detectors along its entire or nearly entire circumference.

[0088] The Fig. 1, Fig. 2, Fig. 3 to Fig.Figure 4 shows the measuring device 1, 1a, 1b and 1c in a section parallel to the fluid guide central axis 11, but for the sake of clarity the target 15 and the emitter wire 17 are shown spatially. List of reference symbols used 1, 1a, 1b, 1c Measuring device 3 Fluid flow / Flow direction 5 Fluid guidance 7 Flow Inlet 9 Flow outlet 11 Central axis of the fluid guidance 13 X-ray source 15 Target 17 Emitter wire 19 Target axis 21 Housings / Radiation source housings 23 first heating voltage connection 25 second heating voltage connection 27 Acceleration voltage connection 29 X-rays 31 X-ray detector 33 Plane that runs perpendicular to the central axis and perpendicular to the target axis through the emitter wire 34 Plane that runs perpendicular to the central axis and perpendicular to the target axis and is arranged with an offset with respect to the emitter wire 35 Plane that runs perpendicular to the target axis through the intersection of the target axis with the central axis 37 Closure 39 Plane that runs perpendicular to the central axis through the intersection of the target axis with the central axis 41 Heat exchanger / heat pipe 43 Contact element 45 Cooling device 47 Holding element 49 bipolar voltage source 51 First connection of bipolar voltage source / ground connection 53 Second connection of bipolar voltage source / positive pole 55 Third connection of bipolar voltage source / negative terminal

Claims

[1] Device (1, 1a, 1b, 1c) for characterizing a fluid flow (3), comprising: - a fluid guide (5) for guiding the fluid flow (3), - an X-ray source (13) with a target (15) and an emitter wire (17), and - a detector device with one or more X-ray detectors (31), - wherein the target (15) and the emitter wire (17) are arranged within the fluid guide (5), wherein the target (15) has a rotationally symmetrical surface with respect to a target axis (19), and wherein the emitter wire (17) is arranged coaxially surrounding the target (15) to the target axis (19), - wherein the device (1, 1a, 1b, 1c) is configured to apply an electrical heating voltage to the emitter wire (17) such that electrons are emitted from the emitter wire (17), and to apply an electrical accelerating voltage between the emitter wire (17) and the target (15) such that the emitted electrons are accelerated towards the target (15) and decelerated by the target, generating X-ray radiation (29), and - wherein the X-ray detectors (31) of the detector device are designed to detect the generated X-ray radiation (29). [2] Device according to claim 1, wherein the fluid guide (5) has a central axis (11) and the target (15) is arranged within the fluid guide (5) such that the target axis (19) coincides with the central axis (11). [3] Device according to claim 1, wherein the fluid guide (5) has a central axis (11) and the target (15) is arranged within the fluid guide (5) such that the target axis (19) intersects the central axis (11) at an angle. [4] Device according to one of the preceding claims, wherein the detector device has one or more X-ray detectors (31) arranged centrally with respect to the emitter wire (17) along the direction specified by the target axis (19). [5] Device according to one of the preceding claims, wherein the detector device has one or more X-ray detectors (31) arranged along the direction specified by the target axis (19) with an offset with respect to the emitter wire (17). [6] Device according to one of the preceding claims, wherein the device for applying the heating voltage to the emitter wire (17) and for applying the accelerating voltage between the target (15) and the emitter wire (17) is arranged such that the heating voltage and the accelerating voltage are relative to a common electrical reference potential. [7] Device according to the preceding claim, wherein the device comprises an electrically conductive heat exchanger (41), wherein a first section of the heat exchanger (41) is arranged in thermal and electrical contact with the target (15), wherein a second section of the heat exchanger (41) is connected to a cooling device (45), and wherein the device is configured to apply the accelerating voltage between the target (15) and the emitter wire (17) by subjecting the heat exchanger (41) to an electrical potential positive relative to the common electrical reference potential. [8] Device according to claim 6 or 7, wherein the device is designed to apply the common electrical reference potential to the fluid guide (5). [9] Device according to one of the preceding claims, wherein the target (15) is arranged in an electrically insulated manner relative to the fluid guide (5). [10] Device according to one of the preceding claims, wherein the device has two terminals (23, 25) for applying the heating voltage to the emitter wire, wherein each of the two terminals contacts one end of the emitter wire (17), and wherein the terminals (23, 25) extend away from the emitter wire (17) parallel to the target axis (19). [11] Device according to one of the preceding claims, wherein the device has a housing (21) such that the target (15) and the emitter wire (17) are surrounded by the housing (17) within the fluid guide (5). [12] Device according to the previous claim, wherein the target (15) and the emitter wire (17) are arranged in a rotationally symmetric section of the housing (21) with respect to the target axis (19). [13] Method for characterizing a fluid flow (3) wherein: - the fluid flow (3) is guided through a fluid guide (5), - the fluid flow (3) is irradiated with X-rays (29) which are generated by means of an X-ray source (13) with a target (15) and an emitter wire (17), - wherein the target (15) and the emitter wire (17) are arranged within the fluid guide (5), the target (15) has a rotationally symmetrical surface with respect to a target axis (19), and the emitter wire (17) is arranged coaxially surrounding the target (15) to the target axis (19), - wherein the X-ray radiation (29) is generated by applying an electrical heating voltage to the emitter wire (17) such that electrons are emitted from the emitter wire (17), and by applying an electrical accelerating voltage between the emitter wire (17) and the target (15) such that the emitted electrons are accelerated towards the target (15) and decelerated by the target (15) generating the X-ray radiation (29), and - wherein the X-ray radiation (29) attenuated by the fluid flow (3) is detected by means of a detector device with one or more X-ray detectors (31).

Images