Radiance detector

Abstract

The invention relates to a detector (1) for a radiometric measurement system, the scintillator (11) and photodiode (12) of which are dimensionally compact and optically coupled such that they can be optically shielded encapsulated by microelectronic build-up and bonding techniques. Accordingly, a corresponding shared package (13) can be provided for the scintillator (11) and a semiconductor assembly comprising at least one photodiode (12) according to any IC package type, such as, for example, via or surface mount. Therefore, an evaluation signal (# imgabs0 #) generated by the photodiode (12) according to the radioactive radiation intensity entering the scintillator (11) can be tapped, for example, via an output pin (131) of the package (13). Thus, the detector (1) of the present invention is advantageous by its manageability as a conventional fillable electronic component. This enables modular construction of the radioactive measurement system in order to individually adapt to specific application areas with little constructive effort.

Description

Field of the Invention

[0001] The present invention relates to a detector for a radiometric measurement system. Background Art

[0002] In automation technology, especially in process automation, measuring devices and measurement systems are usually applied to record and / or influence process variables. In such cases, the determined process variables include level, flow rate, pressure, temperature, pH value, redox potential or conductivity, etc. In such cases, depending on the process variable, mutually different measurement principles are implemented in the measuring device or measurement system. Actuators, such as valves or pumps, are used to influence the process variable, via which the flow rate of the liquid in a pipeline section or the level in a container can be changed. The Endress+Hauser Group manufactures and sells a large number of such measuring devices and measurement systems.

[0003] When other measurement principles (such as, for example, radar) are not applicable due to harsh conditions, a radiometric-based measurement system is first used for level measurement. In the case of the radiometric measurement principle, radioactive radiation is utilized. For example, this can be gamma radiation from a cesium source or a cobalt source. The gamma radiation passes from the source through a container containing a filling material. After passing through the container, the remaining radiation intensity is recorded by a corresponding detector of the measurement system. For this purpose, the detector is arranged on the side of the container opposite to the radiation source. Based on the signal intensity or power entering the detector, the fraction of the radiation originally from the radiation source can be determined. Furthermore, based on the transmission fraction, the level of the filling material in the container can be determined. In such a case, the transmission fraction of the radioactive radiation power after passing through the container cannot be directly detected. Instead, the radioactive radiation is first converted in the detector into electromagnetic radiation in a spectral range by a suitable material. Only then can the radiation power be detected in the detector using a photoelectric receiver (such as a photomultiplier or a photodiode, especially an avalanche photodiode or a silicon photomultiplier).

[0004] Materials having such conversion properties are called scintillation materials. Examples of such materials include organic scintillation materials, such as polystyrene, polyvinyltoluene, or inorganic or crystalline forms, such as thallium-doped sodium iodide and gadolinium aluminum gallium garnet ( ). In addition to level measurement, such a measurement system based on the radiometric measurement principle can also determine the density of the filling material after corresponding calibration. Radiometric level and density measurement systems are prior art. Their basic working principle is described, for example, in EP 2 208 031 B1.

[0005] Each radiometric measurement system needs to be individually adjusted according to the process to be observed, especially according to the container of the process. This first involves the detector, because whether it is for level measurement or density measurement, the vertical area to be observed on the container must be completely covered by the scintillator of the detector. Depending on the process and the container size, the area to be covered can vary greatly. Summary of the Invention

[0006] Therefore, the object of the present invention is to provide an individually adjustable measurement system.

[0007] The present invention achieves this object by means of a radiometric detector for a radiometric measurement system, which detector comprises:

[0008] - a scintillator, and

[0009] - one or more photodiodes optically connected to the scintillator for generating an electrical evaluation signal according to the intensity of the radioactive radiation entering the scintillator. For a plurality of photodiodes, they can be arranged, for example, in an array, especially on a semiconductor component. In such a case, the photodiodes can be, for example, avalanche photodiodes based on GaAs or silicon photomultipliers ("SiPM"). Thus, in the context of the present invention, "photodiode" includes silicon photomultipliers.

[0010] According to the present invention, at least one photodiode and the scintillator are dimensionally compact and coupled to each other such that they can be encapsulated by means of microelectronic construction and bonding techniques. In the corresponding design, the corresponding shared encapsulation of the detector can additionally protect the scintillator and the photodiodes from stray optical radiation. The evaluation signal of the detector can be tapped via the electrical output terminals of the encapsulation. In such a case, the encapsulation and the output terminals can be designed according to all types of IC packages, for example:

[0011] - "Through-hole"

[0012] - "Surface mount"

[0013] - "Chip carrier"

[0014] - "Pin grid array"

[0015] - "Flat package"

[0016] - "Small outline integrated circuit"

[0017] - "Chip scale package"

[0018] - "Ball grid array"

[0019] - "Multi-chip package", with a potted circuit board.

[0020] The advantage of the detector according to the invention lies in its manageability as a conventional refillable electronic component. This enables a modular design of the radiation measurement system, so that it can be used for specific application areas individually with less constructional effort.

[0021] The detector according to the invention can be constructed more conveniently when the encapsulation is formed by a scintillator and vice versa. For example, for an organic scintillator material, it can be encapsulated by injection molding, for example. In order to protect at least one photodiode from the light affecting the radiation measurement, in this design variant, the scintillator-based encapsulation is provided with an optically opaque coating.

[0022] Furthermore, the detector according to the invention can be designed in such a way that at least one photodiode in the encapsulation is followed by a signal processing unit, which can amplify, filter and / or digitally evaluate the signal. Since a DC power supply between 20 V and 95 V is required depending on the type of photodiode, a high-voltage converter can also be integrated in the encapsulation for supplying voltage to the photodiode. In such a case, a temperature sensor can also be integrated in the encapsulation so that the high-voltage source can be controlled accordingly depending on the temperature. In this way, the temperature dependence of the photodiode can be compensated by a control device.

[0023] In such a case, when the signal processing unit, the high-voltage source and the temperature sensor are designed as an integrated component of a semiconductor component (which also includes the photodiode), the detector according to the invention can be encapsulated particularly compactly, for example based on "chip-scale packaging".

[0024] The detector according to the invention can be applied to a radiation measurement system in, for example, a computed tomography device or industrial process measurement technology in order to determine, for example, the density, density profile and / or level of a filling material in a container. Such a measurement system is constructed in the following way:

[0025] - The radioactive radiation source is placed relative to the container such that radioactive radiation is emitted towards the container within a defined beam cone;

[0026] - At least one detector according to one of the above embodiments of the invention is mounted on the side of the container opposite the radiation source such that the scintillator of the detector is at least partially within the beam cone; and

[0027] - An evaluation unit connected to at least one detector determines the density, density profile or level of the filling material in the container based on one or more evaluation signals (depending on the design of the measurement system).

[0028] Generally speaking, in the context of the present invention, a "unit" in principle refers to any electronic circuit provided for a specific application (for example, for measuring signal processing or as an interface). Therefore, depending on the application, a specific unit may include corresponding analog circuits for generating or processing analog signals. However, the unit may also include digital circuits such as FPGAs, microcontrollers or storage media, and work in cooperation with corresponding programs. In such a case, the program is designed to execute the necessary method steps or computer operations required by the application. In this context, within the scope of the present invention, different units may also potentially use shared physical memory or operate through the same physical digital circuit. On the other hand, it doesn't matter whether different electronic circuits are arranged within one unit on a shared circuit board or on multiple interconnected circuit boards.

[0029] Particularly for level and density profile measurements, the measurement system advantageously includes a plurality of cascaded detectors, which are particularly arranged vertically one above the other at the container. In such a case, the detectors can be mounted on a shared circuit board. Alternatively, the detectors can each be arranged on separate circuit boards within separate housings, such that they each form a complete measurement system as independent modules. For computed tomography equipment, the detectors of the present invention are arranged in an array according to the functional principle of tomography. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will now be described in more detail in conjunction with the accompanying drawings, which are as follows:

[0031] Figure 1 : Cross-sectional view of the detector of the present invention;

[0032] Figure 2 : Cross-sectional view of the detector in the preferred embodiment;

[0033] Figure 3 : Circuit block diagram of an embodiment of the detector; and

[0034] Figure 4 : Radiometric measurement system based on the detector of the present invention and arranged at the container. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] Figure 1 The structural details of the detector 1 of the present invention for a radiometric measurement system are shown. The detector 1 can be applied to, for example, level measurement or computed tomography. Based on its functional principle, the detector 1 includes all necessary components to generate an electrical evaluation signal based on the incident radioactive radiation , and display the power or intensity of the incident radiation. From this, other physical variables can be determined, which correspondingly include rich information in the context of different measurement principles (such as computer tomography, etc.). Therefore, the scintillator 11 of the detector 1 is used to convert the incident radioactive radiation into optically or spectrally adjacent radiation. For this purpose, the scintillator 11 can operate based on organic scintillator materials (such as polystyrene or polyvinyltoluene). On the other hand, inorganic scintillator materials with corresponding scintillation properties can also be applied, such as thallium-doped sodium iodide or gadolinium gallium garnet. The optical radiation from the scintillator 11 is converted into an electric current by a single photodiode 12 or an array of photodiodes 12, and this current represents at least in its original form the electrical evaluation signal . In such a case, the photodiode 12 should be constructed such that its bandgap corresponds to the scintillator material and thus to the wavelength of the optical radiation.

[0036] The detector 1 of the present invention is characterized in that it is encapsulated using construction and bonding techniques known in semiconductor technology. In this way, the detector 1 can be filled on a circuit board and can be constructed as a separate module, so that the corresponding radiometric measurement system can be designed compactly and modularly. In such a case, in principle, any IC package type is applicable, such as THP ("through-hole package") or SMD ("surface mount device").

[0037] As Figure 1 shown in the illustrated embodiment, for an IC-standard-compliant package, on the one hand, the size of the scintillator 11 is comparable to the size of the selected semiconductor component including the photodiode 12 or the array of photodiodes 12. This means that for the defined contact area of the semiconductor component, for example, the relevant side length of the square scintillator 11 corresponds to the side length of the semiconductor component to the greatest extent, such as Figure 1 schematically shown. In this embodiment, the key is that the scintillator 12 covers the semiconductor surface area formed by one or more photodiodes 12. In such a case, the scintillator 11 can be either an organic material or an inorganic material. For example, it is fixed to one or more photodiodes 12 by an optically transparent adhesive to optically couple them to each other.

[0038] On the other hand, in Figure 1In an embodiment, the height dimension of the scintillator 11 from the photodiode 12 is not greater than the longest side length of the semiconductor chip. In this way, the detector 1 can be packaged by conventional construction and bonding techniques. Therefore, the package 14 of the detector 1 of the present invention can be designed as any type of IC package. In such a case, the key is that the packaging material must have an optical shielding effect and completely surround the scintillator 11 and the semiconductor components to protect the photodiode 12 from stray light. In principle, for example, any potting compound known in the prior art can be applied here, and black plastic is particularly beneficial for preventing stray light. However, as another option, a ceramic or metal housing ("metal can package") can also be used to construct the package 13.

[0039] In Figure 1 and Figure 2 the embodiment shown, the detector 1 is packaged in a THP type ("through-hole package"). Therefore, the semiconductor components including the photodiode 12 are arranged on the lead frame 133 and are correspondingly connected by bonding wires. In such a case, one of the pins 131 of the THP package is used as the electrical output of the evaluation signal of.

[0040] Figure 2 shows another embodiment of the detector 1 of the present invention, which corresponds to the embodiment shown in Figure 1 except for the package 13 and the scintillator 11. In Figure 2 this, the package 13 is composed of the scintillator 11, and vice versa. For this purpose, one or more photodiodes 12 are potted with a scintillator material, for example, by injection molding or a similar production method. In such a case, a corresponding plastic is applied as the scintillator material, such as polystyrene or polyvinyltoluene. The advantage in such a case is that, on the one hand, there is no need to separately fill the scintillator 12. On the other hand, casting the scintillator material around the semiconductor components will automatically form an optical coupling between the scintillation packages 11, 13 and the semiconductor components, and one or more photodiodes 12 are arranged on the semiconductor components. However, in order to protect the photodiode 12 from stray light, in this embodiment, the scintillator 11 and the package 13 must include an optically opaque coating 132, for example, in the form of a corresponding coating.

[0041] Figure 3 shows a possible circuit block diagram of a semiconductor component that monolithically includes one or more photodiodes 12. On the one hand, within the semiconductor component, one or more photodiodes 12 are connected to an analog low-pass filter 121 so as to filter out high-frequency interference components in the evaluation signal before it is led to the signal output terminal 131. In this regard, it is also possible to directly perform the evaluation signal inside the semiconductor component be amplified and / or digitized. On the other hand, a high-voltage source 123 is also monolithically integrated in the semiconductor component, and its circuit block diagram is as shown in Figure 4 to supply the necessary 20 - 95 V DC voltage to the photodiode 12. For this purpose, the high-voltage source 123 can operate based on, for example, the "switching capacitor" principle.

[0042] Figure 3 The embodiment of the semiconductor component shown in further includes a chip-integrated temperature sensor 122. In such a case, the temperature value measured by the temperature sensor 122 can be tapped via a separate electrical output 136 of the semiconductor chip (i.e., the corresponding connection of the detector 1) to supply the temperature value to the evaluation unit 6. In this way, under the corresponding design, the evaluation unit 6 can control the high-voltage source 123 to compensate for the temperature dependence of the output signal of the photodiode 12. For this purpose, the detector 1 includes, for example, an electrical input 135 for controlling the high-voltage source 123 at a corresponding pin, and this electrical input is, for example, further controlled by the evaluation unit 6.

[0043] The voltage supply of the high-voltage source 123, the temperature sensor 122, and the low-pass filter 121 is realized inside the chip via a shared power connection to the semiconductor chip, thus connected to the detector 1. In addition to monolithically integrating the high-voltage source 123, the temperature sensor 121, the low-pass filter 121, and the photodiode 12 in one semiconductor component, Figure 4 the circuit block diagram shown in can also be implemented by hybrid components on a shared circuit board. In such a case, the entire circuit board for implementing the concept of the present invention will be encapsulated according to the "system-in-package" principle, that is, the circuit board and the components 12, 121, 122, 133 thereon are all potted.

[0044] Figure 4 shows a possible application of the detector 1 of the present invention, that is, a radiometric measurement system for industrial level measurement. Accordingly, Figure 4 shows a container 3 of an industrial process equipment. In such a case, the container 3 can contain a filling material 2, such as crude oil undergoing a fractionation process. To control this process, it is necessary to determine the level L of the filling material 2. Due to the harsh process conditions, radiometric level measurement is used. For this purpose, the arrangement and direction of the radiation source 5 of the measurement system should be such that the radioactive radiation is emitted towards the container 3 within a defined beam cone a. In such a case, in Figure 4In an embodiment, the radiation source 5 is arranged in the upper end region of the container 3 and is inclined downward by approximately 45°. In this way, it is ensured that the beam cone a irradiates the height range necessary for measuring the material level and / or density profile inside the container. Depending on the height of the container 3 and, in a given case, depending on the process being run, this height range may vary, so the measurement system in principle needs to have individual adaptability.

[0045] On the side of the container 3 opposite to the radiation source 5, eleven detectors 11 are arranged. The scintillator 11 of each detector 11 faces the container 3, such that the detectors 1 are vertically distributed and equally spaced within the beam cone a of the radiation source 5 and are located within the height range relevant to the material level measurement. In Figure 4 the illustrated embodiment, the detectors 1 are surrounded by a shared housing 14, which protects against environmental influences such as stray optical radiation. In such a case, the detectors 1 can be arranged, for example, on a shared circuit board within the housing 14 and electrically contacted.

[0046] Regarding the measurement system, the detectors 1 of the present invention enable the measurement system to be adapted to different container sizes in a simple structural manner, because the number of detectors 1 can be modularly expanded. The vertical spacing between the detectors 1 relative to each other along the container 3 creates an additional degree of freedom. Since the detectors 1 are arranged linearly vertically within the beam cone a of the radiation source 5, each detector 1 receives radioactive radiation after passing through the filling material 2 or through the gas phase above the filling material inside the container. In this way, the intensity of the received radiation - relative to the output intensity of the radiation source 5 - mainly depends on the material level L of the filling material 1 and its density: when the filling material 2 is in the beam path between the radiation source 5 and the detector 1 (depending on the material level L), the intensity of the incident radiation is correspondingly significantly attenuated. In such a case, the radiation intensity is represented by the evaluation signal of its detector 1. The reason is that the incident radioactive radiation is converted into visible light or optical radiation in the adjacent ultraviolet / infrared light region by the scintillator 11 within each detector 1, and the radiation converted into the optical range by the scintillator 11 is converted into an electrical evaluation signal by the photodiode 12.

[0047] In this way, based on the evaluation signal of the detector 1, it is possible to determine, for example, in a virtual digital manner (in such a case, one number for each detector 1c), which detector 1 has a significantly increased incident radiation intensity at which container height, in order to determine the material level L therefrom. Alternatively, the material level L can also be calculated, for example, in the form of an analog value or a relative value, i.e., by adding the evaluation signals where the added value can be assigned to an absolute or relative material level value L, for example, based on calibration.

[0048] Furthermore, based on the evaluation signal , it is also possible to utilize Figure 4 the arrangement of the detector 1 shown in to determine the height-dependent density profile of the filling material 2. In such a case, each evaluation signal represents (e.g., based on calibration) the density value of the filling material 2. In such a case, the evaluation signal of each detector 1 Figure 4 can be associated with the corresponding height on the container 3 (or at least several of the height-dependent sequences 1–11), so as to obtain a height-dependent density profile. When only a single density value needs to be determined, compared with the

[0049] shown embodiment, the measurement system only requires a single detector 1.

[0049] To determine the density, density profile or level L based on the evaluation signal , Figure 4 the measurement system shown includes an evaluation unit 6 designed accordingly, which is mechanically connected to the lowest detector 1 in an independent housing part located in the corresponding end region of the housing 14. In such a case, the detector 1 can be coupled to the evaluation unit 6, for example, in series or via a bus system, in order to transmit each evaluation signal , or in order to supply power to each detector 1. For this purpose, on the one hand, the evaluation unit 6 can be functionally designed to record the number of the briefly connected detectors 1 or their sequence (along the container 3). On the other hand, in such a case, it is advantageous that the evaluation unit 6 can automatically set or adjust the height range for creating the density profile or the measured level L according to the number of the briefly connected detectors 1.

[0050] Generally speaking, the radiation source 5 and the detector 1 or the housing 14 can be directly mounted on the container 3, or can be indirectly mounted via an independent bracket. As Figure 1 shown, the evaluation unit 6 of the measurement system can be connected to a superior unit 4 (such as, for example, a local process control system or a decentralized server system) via a separate interface unit (such as, for example, "4 - 20 mA", "Process Field Bus (PROFIBUS)", "HART" or "Ethernet") for process control. In this way, the measured density or level value L can be transmitted, for example, in order to control a heating element or a possible supply line leading to the container 3. However, other information about the overall operating state of the measurement system can also be transmitted.

[0051] List of reference numerals

[0052] 1 Detector

[0053] 2 Filling material

[0054] 3 Container

[0055] 4 Superior unit

[0056] 5 Radioactive radiation source

[0057] 6 Evaluation unit

[0058] 11 Scintillator

[0059] 12 Photodiode

[0060] 13 Encapsulation

[0061] 14 Housing

[0062] 121 Analog low-pass filter

[0063] 122 Temperature sensor

[0064] 123 High-voltage source

[0065] 131 Electrical output terminal for evaluating the signal

[0066] 132 Optically opaque coating

[0067] 133 Lead frame

[0068] 134 Power connection

[0069] 135 Electrical input terminal for controlling the high-voltage source

[0070] 136 Electrical output terminal for the value of the temperature sensor

[0071] a Beam cone

[0072] L Material level

[0073] Evaluation signal

Claims

1. A radiance detector (1) for a radiance measurement system, comprising: - A scintillator (11); - at least one photodiode (12), which is optically connected to the scintillator (11) so as to generate an electrical evaluation signal in accordance with the intensity of the radioactive radiation entering the scintillator (11) ( ); and - An optical shielding package (13) for shielding the scintillator (11) and the photodiode (12) and having o at least one electrical output (131) for the evaluation signal ( ).

2. The detector according to claim 1, wherein The package (14) and the output terminal (131) are designed as an IC package.

3. The detector according to claim 1 or 2, comprising: - A plurality of photodiodes (12), in particular arranged as an array.

4. The detector according to one of the preceding claims, wherein, The package (13) is formed by the scintillator (11), and wherein the package (13) has an optically opaque coating (132).

5. The detector according to one of the preceding claims, wherein, The photodiode (12) is designed as an avalanche photodiode or as a silicon photomultiplier.

6. The detector according to one of the preceding claims, wherein, The at least one photodiode (12) within the encapsulation (13) is followed by a signal processing unit (121), which is designed to amplify, filter, and / or digitize the evaluation signal ( ).

7. The detector according to one of the preceding claims, wherein, A high-voltage converter (123) is arranged within the package (13) for supplying voltage to the photodiode (12).

8. The detector according to one of the preceding claims, wherein, A temperature sensor (122) is arranged within the package (13), in particular for controlling the high-voltage source (123).

9. The detector according to claim 6, 7 or 8, wherein: - The signal processing unit (121), - The high-voltage source (123), and / or - The temperature sensor (122), is an integrated component of the semiconductor chip (12).

10. A radiance measurement system for determining the density and / or the level (L) of a filling material (2) in a container (3), comprising: - A radioactive radiation source (5) that can be placed relative to the container (3) such that radioactive radiation is emitted towards the container (3) within a defined beam cone (a); - At least one detector (1) according to one of the preceding claims, and the at least one detector can be placed on the side of the container (3) opposite the radiation source (5) such that the scintillator (11) is at least partially within the beam cone (a); And - An evaluation unit (6), which is connected to the at least one detector (1) and is designed to determine the density, density profile or level (L) of the filling material (2) based on the evaluation signal ( ).

11. The measurement system according to claim 10, comprising: - A plurality of detectors (1) according to one of claims 1 to 8, and the plurality of detectors are in particular arranged vertically one above the other at the container (3).

12. A computed tomography device, comprising: - An array of detectors (1) according to one of claims 1 to 9.

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