Detection unit for radioactive radiation for a radiometric level measurement system

Abstract

Detection unit (1) for detecting radioactive radiation (6) for a system (7) for radiometric level measurement, the detection unit (1) comprising: a scintillator (2) for generating radiation-induced light signals, at least one photodetector (3; 3.1 to 3.3) for generating electrical signals based on the light flashes and a measuring electronics (4) for processing the electrical signals, wherein the scintillator (2) comprises a first scintillator element (2.1), a second scintillator element (2.2) and a light guide (8; 8.1), wherein the first scintillator element (2.1) and the second scintillator element (2.2) extend in a longitudinal direction (L) of the scintillator (2), wherein the first scintillator element (2.1) is connected to the at least one photodetector (3; 3.1) in the longitudinal direction (L) of the scintillator (2) and is coupled to the photodetector (3; 3.1), wherein the light guide (8; 8.1) is coupled to the second scintillator element (2.2) and to the at least one photodetector, wherein the light guide (8; 8.1) runs in the longitudinal direction (L) of the scintillator (2) next to the first scintillator element (2.1), wherein the second scintillator element (2.2) adjoins the first scintillator element (2.1) in the longitudinal direction (L) of the scintillator (2), and wherein the detection unit (1) further comprises a conical light cone (9) which is connected on the one hand to the light guide (8) and on the other hand to the second scintillator element in the form of a second fiber bundle (2.2), wherein the conical light cone (9) is designed to guide light from the second fiber bundle (2.2) into the light guide (8), wherein the second fiber bundle (2.2) is thicker than the light guide (8); wherein the first scintillator element (2.1) and the second scintillator element (2.2) each have a measuring length of 2 m to 7 m parallel to a longitudinal axis (L) of the scintillator (2); wherein a measuring length of the entire scintillator (2) is more than 7 m without loss of sensitivity.

Description

Field of the invention

[0001] The invention relates to a detection unit for detecting radioactive radiation for a system for radiometric level measurement. A further claim is directed to a method for compensating for caking during a radiometric level measurement using the aforementioned detection unit. Background of the invention

[0002] Detection units for detecting radioactive radiation for a radiometric stand measurement system are known. These detection units can comprise a scintillator, in particular with flexible scintillation fibers, which are typically bundled in a fiber bundle. The length of the scintillator or its fiber bundle can be up to 7 m. This length is limited, among other things, by the fact that the scintillation fibers attenuate the generated light over their length and typically only have a sufficiently high sensitivity up to the aforementioned 7 m to still be able to couple light flashes of sufficiently high intensity from the end of the scintillation fibers.

[0003] DE 20 08 411 A describes a level measuring device with a radioactive emitter attached to the container for the filling material and a probe attached to the opposite side of the container with radiation-sensitive elements that emit output signals dependent on the intensity of the incident radiation and actuate a display or control device. The probe has a scintillator arrangement that extends over the entire measuring height and forms part of a scintillation counter. US 2014 / 0 264 040 A1 describes a nuclear level sensor for measuring the level of a product in a container with several scintillators arranged in series.A radiation source is positioned near the container, and the scintillators, which may be bundles of one or more scintillation fibers or scintillation crystals, are arranged in series on the side of the container opposite the emitter, so that the radiation passing through the container impinges on the bundles. Light guides guide the photons emitted by the scintillators, which indicate the radiation passing through the container, to a common PMT tube. The tube is connected to electronics that convert the photons counted by the PMT into a measure of the fill level of the radiation-absorbing product in the container. US 2014 / 0 136 127 A1 describes a method for measuring the fill level of contents in a container or vessel, as well as an apparatus suitable for carrying out the method according to the invention.In particular, the method is a method for measuring the fill level, in particular of a fluid, in a container by measuring the radiation emitted by a radiation source and detected by a radiation detector after passing through a region of the container. DE 10 2012 100 768 A1 describes a scintillation detector, in particular a scintillation detector.for a radiometric measuring device for measuring and / or monitoring a measurand, in particular a fill level or a density of a filling material in a container, with two or more scintillators arranged in a row, which convert radioactive radiation incident on them into light flashes, the light of which spreads in the respective scintillator towards its ends, optical coupling elements arranged between the scintillators, which bring about a light-transmitting connection between the two adjacent scintillators, and a photoelectric converter connected to one end of the row, which converts light incident on it via the row into an electrical signal corresponding to a radiation intensity incident on the scintillators.US 2011 / 0 192 979 A1 describes a detector comprising a first scintillation material with temperature-dependent luminous efficacy and an output at a first energy level, a second scintillation material with a similar temperature-dependent luminous efficacy as the first material and an output at a second energy level, and a detection circuit. The first and second outputs respond to radiation emitted by an ionizing radiation source.The detection circuit comprises a photomultiplier tube configured to convert the photons emitted by the first and second scintillation materials into electrical pulses, a counting circuit configured to count the electrical pulses generated in the photomultiplier tube by the first and second materials, and a gain control circuit configured to monitor the electrical pulses generated by the second material in the photomultiplier tube and adjust the gain of the detector when a deviation in the output of the second material is detected. GB 2 375 170 A describes a radiation sensor having a plurality of probes and measuring means for measuring an output signal from at least one probe.The plurality of probes are each configured to detect radiation at different locations and generate an output signal indicative of the level of detected radiation. US 5,675,151 A describes a distribution-type detector comprising scintillation fibers of identical length, an optical delay fiber with a refractive index substantially identical to that of the cores and claddings of the scintillation fibers, light-sensitive elements, preamplifiers, constant-fraction discriminators, a time-to-pulse height converter, an analog-to-digital converter, and a multi-channel pulse height analyzer. Summary of the invention

[0004] An object of the present invention may therefore be to provide a detection unit for detecting radioactive radiation for a system for radiometric level measurement, wherein the scintillator still has sufficient sensitivity even at lengths exceeding 7 m.

[0005] The problem is solved by the subject matter of the independent patent claims. Advantageous embodiments are the subject matter of the dependent claims, the following description, and the figures.

[0006] A core of the invention is to extend a measuring length of the scintillator beyond the value of, in particular, 7 m with the aid of at least one optical fiber, without losing sensitivity. In particular, according to the present invention, instead of a single fiber bundle, which for the reasons mentioned above is typically limited to a measuring length of 7 m, it is proposed to provide several scintillator elements, in particular fiber bundles, which are arranged in a row in a longitudinal direction of the scintillator and which can each individually have a measuring length (ie, in particular, a distance extending in a longitudinal direction of the scintillator over which the scintillator element, in particular the fiber bundle, can be used to detect transmitted radiation) that is significantly below the maximum possible 7 m, e.g.2 m, and which, when lined up together, can result in a measuring length that easily exceeds, for example, 7 m. Instead of fiber bundles, PVT rods or NAJ crystals, for example, can also be used. In the following, the invention is described primarily in connection with fiber bundles—without being limited thereto—but corresponding embodiments also apply mutatis mutandis to PVT rods or NAJ crystals in particular.

[0007] In other words, a series of scintillator elements, in particular fiber bundles, is proposed, wherein the series can be longer than 7 m in total and wherein, for example, the individual fiber bundles can each be shorter than 7 m. A first of these fiber bundles can be connected directly to a photodetector, as is known from the prior art. Further fiber bundles, which are located further away from the photodetector in the longitudinal direction of the scintillator, can be connected to the photodetector by an optical fiber. The optical fiber thus bridges a distance between the further fiber bundle and the photodetector. Alternatively, it is also possible for the first fiber bundle to be connected to a photodetector and for the optical fiber(s) to be connected to a different photodetector, as will be described in more detail below in connection with an advantageous embodiment.

[0008] According to a first aspect of the invention, a detection unit for detecting radioactive radiation is provided for a system for radiometric level measurement. The detection unit comprises a scintillator for generating radiation-induced light signals, in particular light flashes, at least one photodetector for generating electrical signals based on the light signals, and measuring electronics for processing the electrical signals. The scintillator comprises a first scintillator element, a second scintillator element, and a light guide. The first scintillator element and the second scintillator element extend in a longitudinal direction of the scintillator. The first scintillator element adjoins the at least one photodetector in the longitudinal direction of the scintillator and is coupled to the photodetector. The light guide is coupled to the second scintillator element and to the at least one photodetector.The light guide runs in the longitudinal direction of the scintillator next to the first scintillator element. The second scintillator element adjoins the first scintillator element in the longitudinal direction of the scintillator. The detection unit further comprises a conical light cone, which is connected on the one hand to the light guide and on the other hand to the second scintillator element in the form of a second fiber bundle. The conical light cone is designed to guide light from the second fiber bundle into the light guide, and the second fiber bundle is thicker than the light guide. The first scintillator element and the second scintillator element each have a measuring length of 2 m to 7 m parallel to a longitudinal axis of the scintillator. A measuring length of the entire scintillator is more than 7 m without loss of sensitivity.

[0009] The detection unit according to the first aspect of the invention can in particular be combined with a radiation source for emitting radioactive radiation in order to carry out a radiometric fill level measurement. In particular, the height of a filling material within a container can be measured. For this purpose, the radiation source can be arranged on a first side of an outer wall of the container, whereas the detection unit is arranged on a second side of the outer wall of the container, wherein the second side is opposite the first side. In particular, the detection unit can be arranged vertically, so that the longitudinal axis of the scintillator also extends in the vertical direction. The photodetector can be arranged at the top, so that the scintillator extends in the vertical direction below the photodetector.

[0010] The filling material whose height is to be measured can be located inside the container. The radiation source typically comprises a gamma emitter and can emit a radioactive signal, in particular gamma radiation, towards the container and towards the detection unit. The detection unit can detect and evaluate at least a portion of the radiation emitted by the radiation source. From the radiation source, the emitted radioactive radiation can be transmitted through the outer wall of the container, through the air surrounding the filling material inside the container, and through the filling material. Depending in particular on the density of the filling material and the fill level of the filling material inside the container, usually only a portion of the emitted radioactive radiation is transmitted.The transmitted portion of the emitted radiation can impinge on the scintillator of the detection unit, whereby the scintillator can convert the received radiation into light signals, in particular into light flashes.

[0011] The at least one photodetector, e.g., a photomultiplier or a photodiode, can be connected to the scintillator, whereby the photodetector can convert the light signals produced in the scintillator into electrical pulses. The measuring electronics can be communicatively connected to the at least one photodetector and further configured to evaluate the electrical pulses (determining the pulse rate), which are a measure of the radioactive radiation detected at the scintillator. Based on the determined pulse rate, the detection unit can determine the height of the contents within the container, in particular by means of the measuring electronics.

[0012] According to one embodiment, the scintillator can in particular comprise a first scintillator element, e.g. a first fiber bundle, a second scintillator element, e.g. a second fiber bundle, and a light guide, wherein the first scintillator element and the second scintillator element extend in a longitudinal direction of the scintillator. In particular, a first fiber bundle and a second fiber bundle can run in the longitudinal direction of the scintillator. The fiber bundles can, for example, have an at least substantially straight shape or a curved shape. The first scintillator element can adjoin the at least one photodetector in the longitudinal direction of the scintillator and be coupled to the photodetector, wherein the light guide can be coupled to the second scintillator element, in particular to the second fiber bundle, and to the at least one photodetector.

[0013] The first scintillator element does not have to be directly connected to the at least one photodetector, but at least one element, e.g. a light guide, can also be located between the first scintillator element and the at least one photodetector. Alternatively or additionally, the light guide can also be coupled to the first scintillator element. Furthermore, in particular a first light guide and a second light guide can be provided, wherein the first light guide couples the first scintillator element to the photodetector, and wherein the second light guide couples the second scintillator element to the first scintillator element. The light guide can run next to the first scintillator element in the longitudinal direction of the scintillator, and the second scintillator element can be connected to the first scintillator element in the longitudinal direction of the scintillator.The feature "running alongside the first scintillator element" particularly includes the variant according to which the first scintillator element surrounds the light guide in certain areas, in particular coaxially. Thus, the light guide can also be guided, in particular, through the first scintillator element.

[0014] This embodiment, in particular, enables the scintillator to maintain sufficient sensitivity even at lengths exceeding 7 m. For example, the first fiber bundle can be 4 m or more long, and the second fiber bundle can also be 4 m or more long. This can result in a total length of the scintillator of 8 m, for example. However, because the individual fiber bundles are significantly shorter than 7 m, the scintillator also exhibits particularly high sensitivity.

[0015] According to one embodiment, a total of three scintillator elements, in particular fiber bundles, or more scintillator elements, in particular fiber bundles, can be provided. In this context, the scintillator can further comprise at least one further light guide and at least one further scintillator element extending in the longitudinal direction of the scintillator. The further light guide can be coupled to the further scintillator element and to the at least one photodetector, wherein the further light guide extends in the longitudinal direction of the scintillator next to the first scintillator element and next to the second scintillator element, and wherein the further scintillator element adjoins the second fiber bundle in the longitudinal direction of the scintillator.The feature "running alongside the first scintillator element and alongside the second scintillator element" particularly includes the variant according to which the first scintillator element and the second scintillator element partially surround the additional light guide, in particular coaxially. Thus, the additional light guide can also be routed, in particular, through the first scintillator element and the second scintillator element.

[0016] In principle, any number of additional scintillator elements, in particular fiber bundles, and additional light guides can be provided, for example to create a series of fiber bundles, where the length of the series can correspond to an intended length of the scintillator. In other words, the measuring length can be increased using light guides by connecting several scintillator elements, in particular fiber bundles of, for example, 2 m, each to a light guide. These light guides can be guided to a photodetector, which can be, for example, a photomultiplier or a photodiode. This photodetector can then measure the incoming light pulses. Depending on the diameter of the light guide and the photodetector, any number of fiber bundles can be coupled to the photodetector.

[0017] As already mentioned above, the first scintillator element, the optical fiber connected to the further scintillator element, and the individual further optical fibers can each be connected to a separate photodetector or to a single common photodetector. Thus, according to a further embodiment, the first fiber bundle and each of the optical fibers are coupled to a separate photodetector. This embodiment makes it possible, in particular, to determine the length range in which the pulses are generated. In fill-level applications, the dose rate and thus the pulse rate are reduced first in the fiber bundles that are mounted lowest. Thus, by comparing the pulse rates, a simple diagnosis is possible, which determines whether a fiber bundle or the associated photodetector is defective.This embodiment further enables the detection unit to automatically compensate for buildup within a container in which the fill level of a product is to be determined. How this can be done specifically using the detection unit is described further below in connection with a corresponding method for compensating buildup in a radiometric fill level measurement according to a third aspect of the invention.

[0018] Alternatively, the first scintillator element, in particular the first fiber bundle, and each of the optical fibers can be coupled to a single common photodetector. This embodiment is particularly characterized by its simple and cost-effective design, which provides only one photodetector.

[0019] According to a further embodiment, the detection unit can further comprise at least one conical light cone, which is connected on the one hand to the at least one optical fiber and on the other hand to one of the fiber bundles, e.g., to the second fiber bundle. The conical light cone is configured to guide light from the respective fiber bundle into the respective optical fiber, wherein the fiber bundle is thicker than the optical fiber. In other words, a conical light cone can be used to couple a fiber bundle to an optical fiber, which particularly advantageously guides the light from the thicker fiber bundle to the thinner optical fiber.

[0020] The respective optical fiber can also be coupled to an entire fiber bundle, e.g., to the entire second fiber bundle. Alternatively, the respective optical fiber can also be coupled to individual fibers of a respective fiber bundle, e.g., to individual fibers of the second fiber bundle.

[0021] The light guide can further comprise a scintillating fiber. Thus, instead of a pure light guide, a scintillating fiber can also be used in the sense of a scintillating light guide.

[0022] According to a second aspect of the invention, a system for radiometric level measurement is provided. The system comprises a detection unit according to the first aspect of the invention and a radiation source for emitting radioactive radiation, as already described above in connection with the first aspect of the invention. Regarding the advantages and advantageous embodiments of the system according to the invention, reference is made to the above statements in connection with the detection unit according to the invention and to the following description to avoid repetition.

[0023] According to a third aspect of the invention, a method for compensating for caking during a radiometric fill level measurement is provided. According to the method, a radiation source for emitting radioactive radiation is arranged on a first side of an outer wall of a container, and a detection unit according to the first aspect of the invention is arranged on a second side of the outer wall of the container opposite the radiation source. In particular, the detection unit can be arranged vertically, so that the longitudinal axis of the scintillator also extends in the vertical direction. The photodetector can be arranged on top, so that the scintillator elements, in particular the fiber bundles, of the scintillator extend in the vertical direction below the photodetector.

[0024] A radioactive signal is emitted by the radiation source toward the container and the detection unit, and a first reference pulse rate of the first scintillator element, in particular the first fiber bundle, and a second reference pulse rate of the second scintillator element, in particular the second fiber bundle, are determined and stored, wherein the container is initially empty and has no caking. If the detection unit comprises additional scintillator elements, in particular fiber bundles, corresponding reference pulse rates are also determined and stored for these additional scintillator elements.

[0025] Subsequently, a first measurement pulse rate of the first scintillator element and a second measurement pulse rate of the second scintillator element are determined. If the detection unit includes additional scintillator elements, corresponding measurement pulse rates are also determined for these additional scintillator elements. During the measurement pulse rate determination, the container may already be at least partially filled with product and exhibit one or more deposits.

[0026] In a next step, it is determined or recognized which of the scintillator elements are still above the fill level. For example, it can be determined that there is already fill material within a section of the beam path between the radiation source and the furthest scintillator element, whereas there is no fill material within the beam path between the radiation source and the scintillator elements arranged further up. In this case, the scintillator element arranged furthest down can still deliver a significant pulse rate which exceeds a specified value. This significant pulse rate of the scintillator element arranged furthest down can be determined by the detection unit, whereby the detection unit can assume orone can conclude that the scintillator elements arranged further up are still above the filling level and are therefore uncovered.

[0027] The detection unit, in particular its measuring electronics, can now compare the measured pulse rates of the scintillator elements still above the fill level with the corresponding reference pulse rates. If there is a difference between the measured pulse rates and the reference pulse rates, this indicates a buildup of caking located in a beam path between the radiation source and the corresponding scintillator element on the inner wall of the container. In other words, the aforementioned difference may have been caused by the buildup. However, the difference can be compensated for, in particular, by increasing the determined measured pulse rates to the reference pulse rates. In this way, any caking within the container can be automatically compensated for by the detection unit.

[0028] In this sense, it can be provided, in particular, that the stored first reference pulse rate is then compared with the determined first measurement pulse rate, and an adjustment is made, in particular an increase of the first measurement pulse rate to the first reference pulse rate, if the comparison shows that the first measurement pulse rate deviates from the first reference pulse rate and if the determined second measurement pulse rate exceeds a specified value. If the detection unit comprises additional fiber bundles, corresponding comparisons and compensations are also performed for these additional fiber bundles.

[0029] According to one embodiment, it is advantageously provided that the adjustment, in particular the increase of the first measurement pulse rate to the first reference pulse rate, is carried out by multiplying the first measurement pulse rate by a factor. In other words, the compensation for caking within the container can be achieved by factors with which the pulse rates of each scintillator element are changed so that the original reference pulse rates are restored.

[0030] The pulse rate of the scintillator element located furthest down can be calculated using an estimated factor. Short description of the characters

[0031] In the following, exemplary embodiments of the invention are explained in more detail with reference to the schematic drawing, wherein identical or similar elements in the individual figures are provided with the same reference numerals. Herein: Fig. 1 a longitudinal section of a known detection unit for detecting radioactive radiation for a system for radiometric level measurement, Fig. 2 a longitudinal sectional view of a first embodiment of a detection unit according to the invention for detecting radioactive radiation for a system for radiometric level measurement, Fig. 3 a longitudinal sectional view of a second embodiment of a detection unit according to the invention for detecting radioactive radiation for a system for radiometric level measurement and Fig. 4 a longitudinal sectional view of an embodiment of a system according to the invention for radiometric level measurement with a radiation source, the detection unit according to Fig. 3 and with a container with filling material and caking. Detailed description of implementation examples

[0032] Fig. Figure 1 shows a known detection unit 1 for detecting radioactive radiation for a system for radiometric level measurement. The detection unit 1 comprises a scintillator in the form of a single fiber bundle 2 for generating radiation-induced light signals, in particular light flashes, a photodetector 3 for generating electrical signals based on the light signals, and measurement electronics 4 for processing the electrical signals. The scintillator 2 can comprise flexible scintillation fibers and, in the illustrated embodiment, is surrounded by a protective tube 5. The scintillation fibers can have a measuring length of up to 7 m.This measuring length is limited, among other things, by the fact that the fibers attenuate the generated light over their length and usually only have a sufficiently high sensitivity up to the aforementioned 7 m to be able to couple out light flashes of sufficiently high intensity from the end of the scintillation fibers to measure a pulse rate.

[0033] Fig. 2 shows a first detection unit 1 according to the invention for detecting radioactive radiation 6 for a system 7 for radiometric level measurement (cf. Fig. 4). The detection unit 1 comprises a scintillator 2 with a first fiber bundle 2.1 and a second fiber bundle 2.2 for generating radiation-induced light signals, in particular light flashes, wherein the first fiber bundle 2.1 and the second fiber bundle 2.2 are arranged in a Fig. 1 to 4 vertically extending longitudinal direction L of the scintillator or parallel thereto. The first fiber bundle 2.1 adjoins a photodetector 3 in the longitudinal direction L of the scintillator 2 and is coupled to the photodetector 3. The photodetector 3, e.g., a photomultiplier or a photodiode, is configured to generate electrical signals based on the light signals. Furthermore, the detection unit 1 comprises measuring electronics 4 for processing the electrical signals. The scintillator 2 can comprise flexible scintillation fibers and, in the illustrated embodiment, is surrounded by a protective tube 5.

[0034] The scintillator 2 further comprises a light guide 8. The light guide 8 is coupled at one end via a conical light cone 9 to the second fiber bundle 2.2, which is thicker than the light guide 8. At its other end, the light guide 8 is coupled to the photodetector 3. The light guide 8 continues to run from the photodetector 3 in the longitudinal direction L of the scintillator 2 next to the first fiber bundle 2.1. The second fiber bundle 2.2 adjoins the first fiber bundle 2.1 in the longitudinal direction L of the scintillator 2. In the Fig. In the embodiment shown in Fig. 2, the first fiber bundle 2.1 and the second fiber bundle 2.2 are arranged offset from one another in a horizontal direction x of the scintillator 2, so that the light guide 8 can run straight over its entire length.

[0035] Both the first fiber bundle 2.1 and the second fiber bundle 2.2 can each have a measuring length of, for example, up to 7 m parallel to the scintillator's longitudinal axis L. Thus, the measuring length of the entire scintillator 2 can be significantly more than 7 m without any loss of sensitivity.

[0036] Fig. 3 shows an alternative second detection unit 1 according to the invention for detecting radioactive radiation 6 for the system 7 for radiometric level measurement according to Fig. 4. The detection unit 1 comprises a scintillator 2 with a first fiber bundle 2.1, with a second fiber bundle 2.2 and with a third fiber bundle 2.3 for generating radiation-induced light signals, in particular light flashes, wherein the three fiber bundles 2.1 to 2.3 are arranged in the Fig. 1 to 4 extend vertically along the longitudinal direction L of the scintillator or parallel thereto. The first fiber bundle 2.1 adjoins a first photodetector 3.1 in the longitudinal direction L of the scintillator 2 and is coupled to the first photodetector 3.1. The first photodetector 3.1, as well as two further photodetectors 3.2 and 3.3, e.g., a photomultiplier or a photodiode, are configured to generate electrical signals based on the light signals. Furthermore, the detection unit 1 comprises measuring electronics 4 for processing the electrical signals. The scintillator 2 can comprise flexible scintillation fibers and, in the illustrated embodiment, is surrounded by a protective tube 5.

[0037] The scintillator 2 further comprises a first light guide 8.1 and a second light guide 8.2. The first light guide 8.1 is coupled at one end via a conical first light cone 9.1 to the second fiber bundle 2.2, which is thicker than the first light guide 8.1. At its other end, the first light guide 8.1 is coupled to a second photodetector 3.2. The first light guide 8.1 continues to run from the second photodetector 3.2 in the longitudinal direction L of the scintillator 2 next to the first fiber bundle 2.1. The second fiber bundle 2.2 adjoins the first fiber bundle 2.1 in the longitudinal direction L of the scintillator 2. In the Fig. 3, the first fiber bundle 2.1 and the second fiber bundle 2.2 are arranged in the horizontal direction x of the scintillator 2 without offset from one another, for which purpose the first light guide 8.1 is designed to be bent accordingly at the level of a lower end region of the first fiber bundle 2.1.

[0038] The second light guide 8.2 is coupled in a similar manner at one end via a conical second light cone 9.2 to the third fiber bundle 3, which is thicker than the second light guide 8.2. At its other end, the second light guide 8.2 is coupled to a third photodetector 3.3. The second light guide 8.2 continues to run from the third photodetector 3.3 in the longitudinal direction L of the scintillator 2 next to the first fiber bundle 2.1 and next to the second fiber bundle 2.2. The third fiber bundle 2.3 adjoins the second fiber bundle 2.2 in the longitudinal direction L of the scintillator 2. In the Fig. 3, the second fiber bundle 2.2 and the third fiber bundle 2.3 are also arranged in the horizontal direction x of the scintillator 2 without offset from one another, for which purpose the second light guide 8.2 is designed to be correspondingly bent at the level of a lower end region of the second fiber bundle 2.2.

[0039] The first fiber bundle 2.1, the second fiber bundle 2.2, and the third fiber bundle 2.3 can each have a measuring length of up to 7 m parallel to the scintillator's longitudinal axis L. Thus, the measuring length of the entire scintillator 2 can be significantly more than 7 m without any loss of sensitivity.

[0040] For the registration units 1 according to Fig. 2 and Fig. 3, the optical fibers 8, 8.1 and 8.2 can each be coupled to an entire fiber bundle 2.1, 2.2 or 2.3 or to individual fibers thereof. Furthermore, the optical fibers 8, 8.1 and 8.2 can be coupled according to Fig. 2 and Fig. 3 each comprise a scintillating fiber.

[0041] Fig. 4 shows a system 7 for radiometric level measurement with the detection unit 1 according to Fig. 3 and with a radiation source 15 for emitting radioactive radiation 6. The system 7 can be used to measure the height h of a filling material 9 within a container 10. For this purpose, the radiation source 15 can be arranged on a first side of a lateral outer wall 11 of the container 10 next to the container 10, whereas the detection unit 1 can be arranged on a second side of the lateral outer wall 11 of the container 10 next to the container 11, with the second side being opposite the first side. In particular, the detection unit 1 can be arranged vertically, so that the longitudinal axis L of the scintillator also extends in the vertical direction. The photodetectors 3.1 to 3.3 can be arranged at the top, so that the scintillator 2 extends in the vertical direction L below the photodetectors 3.1 to 3.3.

[0042] The filling material 9, whose height h is to be measured, can be located within the container 10. The radiation source 15 can, for example, comprise a gamma emitter and can emit a radioactive signal, in particular gamma radiation 6, toward the container 10 and toward the detection unit 1. The detection unit 1 can detect and evaluate at least a portion of the radiation 6 emitted by the radiation source 15.

[0043] Emerging from the radiation source 15, the emitted radioactive radiation 6 can be transmitted through the outer wall 11 of the container, through the air 12 surrounding the filling material 9 within the container 10, and through the filling material 9. Depending in particular on the density of the filling material 9 and the fill level h of the filling material 9 within the container 10, usually only a portion of the emitted radioactive radiation 6 is transmitted. The transmitted portion of the emitted radiation 6 can impinge on the scintillator 2 of the detection unit 1, wherein the scintillator 2 can convert the received radiation 6 into light signals, in particular into light flashes.

[0044] As already explained above, the photodetectors 3.1 to 3.3 are connected to the scintillator 2, whereby the photodetectors 3.1 to 3.3 can convert the light signals produced in the scintillator 2 into electrical pulses. The measuring electronics 4 can be communicatively connected to the photodetectors 3.1 to 3.3 and further configured to evaluate the electrical pulses (determination of pulse rates), which are a measure of the radioactive radiation detected at the scintillator 2. Based on the determined pulse rate, the detection unit 1 can determine the height h of the filling material 9 within the container 10, in particular by means of the measuring electronics 4.

[0045] In the Fig. In the embodiment shown in Figure 4, there are deposits 13 on the inner surface 14 of the outer wall 11 of the container 10. These deposits 13 can influence the measurement result and are therefore undesirable. The detection unit 1 can automatically compensate for the influences on the determined pulse rates.

[0046] For this purpose, a radioactive signal 6 is first emitted by means of the radiation source 15 in the direction of the container 10 and the detection unit 1, whereby the container 10 - deviating from the illustration according to Fig. 4 - is initially unfilled and has no caking 13. This is followed by determining and storing a first reference pulse rate of the first fiber bundle 2.1, a second reference pulse rate of the second fiber bundle 2.2, and a third reference pulse rate of the third fiber bundle 2.3.

[0047] Subsequently, the container 10 can be filled with the filling material 9 and a first measuring pulse rate of the first fiber bundle 2.1, a second measuring pulse rate of the second fiber bundle 2.2 and a third measuring pulse rate of the third fiber bundle 2.3 can be determined.

[0048] In a next step, it can be determined or recognized which of the fiber bundles 2.1 to 2.3 are still above the fill level h. For example, it can be determined that fill material 9 is already located within a region of the beam path between the radiation source 15 and the third fiber bundle 2.3, whereas there is no fill material 9 within the beam path between the radiation source 15 and the fiber bundles 2.1 and 2.2 arranged further up. In this case, the third fiber bundle 2.3 can still deliver a significant pulse rate which exceeds a specified value. This significant pulse rate of the third fiber bundle 2.3 can be determined by means of the measuring electronics 4, whereby the measuring electronics 4 can assume or conclude that the fiber bundles 2.1 and 2.2 arranged further up are still above the fill level h and are therefore uncovered.

[0049] The measuring electronics 4 can now compare the measured pulse rates of the fiber bundles 2.1 and 2.2, which are still above the fill level, with the corresponding reference pulse rates. If there is a difference between the measured pulse rates and the reference pulse rates, this indicates the presence of deposits 13 located in a beam path between the radiation source 15 and the fiber bundles 2.1 and 2.2 on the inner surface 14 of the outer wall 11 of the container 10. In other words, the aforementioned difference may have been caused by the deposits 13. However, the difference can be compensated for, in particular, by increasing the determined measured pulse rates to the reference pulse rates. In this way, the deposits 13 within the container 10 can be automatically compensated for by the detection unit 1.In particular, the automatic compensation of buildup 13 within the container 10 can be achieved by applying factors that adjust the measurement pulse rates of fiber bundles 2.1 and 2.2 so that the original reference pulse rates are restored. The measurement pulse rate of the third fiber bundle 2.3 can be offset by an estimated factor.

Claims

[1] Detection unit (1) for detecting radioactive radiation (6) for a system (7) for radiometric level measurement, the detection unit (1) comprising: a scintillator (2) for generating radiation-induced light signals, at least one photodetector (3; 3.1 to 3.3) for generating electrical signals based on the light flashes and a measuring electronics (4) for processing the electrical signals, wherein the scintillator (2) comprises a first scintillator element (2.1), a second scintillator element (2.2) and a light guide (8; 8.1), wherein the first scintillator element (2.1) and the second scintillator element (2.2) extend in a longitudinal direction (L) of the scintillator (2), wherein the first scintillator element (2.1) is connected to the at least one photodetector (3; 3.1) in the longitudinal direction (L) of the scintillator (2) and is coupled to the photodetector (3; 3.1), wherein the light guide (8; 8.1) is coupled to the second scintillator element (2.2) and to the at least one photodetector, wherein the light guide (8; 8.1) runs in the longitudinal direction (L) of the scintillator (2) next to the first scintillator element (2.1), wherein the second scintillator element (2.2) adjoins the first scintillator element (2.1) in the longitudinal direction (L) of the scintillator (2), and wherein the detection unit (1) further comprises a conical light cone (9) which is connected on the one hand to the light guide (8) and on the other hand to the second scintillator element in the form of a second fiber bundle (2.2), wherein the conical light cone (9) is designed to guide light from the second fiber bundle (2.2) into the light guide (8), wherein the second fiber bundle (2.2) is thicker than the light guide (8); wherein the first scintillator element (2.1) and the second scintillator element (2.2) each have a measuring length of 2 m to 7 m parallel to a longitudinal axis (L) of the scintillator (2); wherein a measuring length of the entire scintillator (2) is more than 7 m without loss of sensitivity. [2] Detection unit (1) according to claim 1, the scintillator (2) further comprising at least one further light guide (8.2) and at least one further scintillator element (2.3) extending in the longitudinal direction (L) of the scintillator (2), wherein the further light guide (8.2) is coupled to the further scintillator element (2.3) and to the at least one photodetector (3.3), wherein the further light guide (8.2) runs in the longitudinal direction (L) of the scintillator (2) next to the first scintillator element (2.1) and next to the second scintillator element (2.2), and wherein the further scintillator element (2.3) adjoins the second scintillator element (2.2) in the longitudinal direction (L) of the scintillator (2). [3] Detection unit (1) according to claim 1 or 2, wherein the first scintillator element (2.1) and each of the light guides (8; 8.1, 8.2) is coupled to a separate photodetector (3.1 to 3.3). [4] Detection unit (1) according to claim 1, wherein the first scintillator element (2.1) and each of the light guides (8) are coupled to a single common photodetector (3). [5] Detection unit (1) according to one of the preceding claims, wherein the optical fiber (8) is coupled to the entire second fiber bundle (2.2). [6] Detection unit (1) for detecting radioactive radiation (6) for a system (7) for radiometric level measurement, the detection unit (1) comprising: a scintillator (2) for generating radiation-induced light signals, at least one photodetector (3; 3.1 to 3.3) for generating electrical signals based on the light flashes and a measuring electronics (4) for processing the electrical signals, wherein the scintillator (2) comprises a first scintillator element (2.1), a second scintillator element (2.2) and a light guide (8; 8.1), wherein the first scintillator element (2.1) and the second scintillator element (2.2) extend in a longitudinal direction (L) of the scintillator (2), wherein the first scintillator element (2.1) is connected to the at least one photodetector (3; 3.1) in the longitudinal direction (L) of the scintillator (2) and is coupled to the photodetector (3; 3.1), wherein the light guide (8; 8.1) is coupled to the second scintillator element (2.2) and to the at least one photodetector, wherein the light guide (8; 8.1) runs in the longitudinal direction (L) of the scintillator (2) next to the first scintillator element (2.1), wherein the second scintillator element (2.2) adjoins the first scintillator element (2.1) in the longitudinal direction (L) of the scintillator (2), and wherein the detection unit (1) further comprises a conical light cone (9) which is connected on the one hand to the light guide (8) and on the other hand to the second scintillator element in the form of a second fiber bundle (2.2), wherein the conical light cone (9) is designed to guide light from the second fiber bundle (2.2) into the light guide (8), wherein the second fiber bundle (2.2) is thicker than the light guide (8); wherein the light guide (8) is coupled to individual fibers of the second scintillator element (2.2). [7] Detection unit (1) according to one of the preceding claims, wherein the light guide (8) comprises a scintillating fiber. [8] System (7) for radiometric level measurement comprising a detection unit (1) according to one of the preceding claims and a radiation source (15) for emitting radioactive radiation. [9] Method for compensating for caking (13) in a radiometric level measurement, the method comprising the steps: Arranging a radiation source (15) for emitting radioactive radiation (6) on a first side of an outer wall (11) of a container (10), Arranging a detection unit (1) according to one of claims 1 to 7 on a second side of the outer wall (11) of the container (10) opposite the radiation source (15), Emitting a radioactive signal (6) by means of the radiation source (15) in the direction of the container (10) and in the direction of the detection unit (1), Determining and storing a first reference pulse rate of the first scintillator element (2.1) and a second reference pulse rate of the second scintillator element (2.2), wherein the container (10) is initially unfilled and has no caking (13), Determining a first measuring pulse rate of the first scintillator element (2.1) and a second measuring pulse rate of the second scintillator element (2.2), Comparing the first reference pulse rate with the first measurement pulse rate, and increasing the first measurement pulse rate to the first reference pulse rate if the comparison shows that the first measurement pulse rate deviates from the first reference pulse rate and if the determined second measurement pulse rate exceeds a specified value. [10] Method according to claim 9, wherein the raising of the first measuring pulse rate to the first reference pulse rate is carried out by multiplying the first measuring pulse rate by a factor.

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