Intelligent low background alpha and beta measuring instrument

Abstract

The invention discloses an intelligent low background alpha and beta measuring instrument, and relates to the field of low background alpha and beta measuring instruments. The device comprises a first scintillator and a second scintillator, a first sample plate and a second sample plate which are used for placing samples are arranged above the second scintillator, a first main detector and a second main detector are arranged between the first scintillator and the second scintillator, an upper anticoincidence detector group is arranged below the first scintillator, and a lower anticoincidence detector group is arranged below the second scintillator. Due to the fact that the silicon photomultiplier is adopted, the size and the space are reduced, signals of the upper anti-coincidence detector and the lower anti-coincidence detector of the main detector are automatically discriminated firstly, cosmic rays are confirmed, then the cosmic rays are discriminated from the signals of the main detector, and the cosmic rays are identified. Therefore, signals generated by cosmic rays can be completely shielded without mistakes, signals generated by a sample can only be generated in one anti-coincidence detector, and accidental coincidence is avoided.

Description

Technical Field

[0001] The present invention relates to the field of low-background α, β measuring instruments, and specifically to an intelligent low-background αβ measuring instrument. Background Art

[0002] A low-background αβ measuring instrument is a precision instrument used to detect extremely low levels of α and β radioactivity in samples. Its core technologies include scintillation detectors and anticoincidence technology. By working together with the upper and lower anticoincidence detectors and the main detector, cosmic rays and environmental radiation interference can be effectively shielded, and the anticoincidence efficiency can reach more than 99%. The instrument uses a lead chamber for shielding and improves the signal processing accuracy through electronics optimization, supports automated measurement and real-time data processing, and has both high sensitivity and operational convenience.

[0003] Traditional instruments basically use a single anti-coincidence detector placed below the main detector. The purpose is that cosmic rays penetrating the external shield from the top first generate signals in the main detector, and then penetrate the main detector and hit the anti-coincidence detector. At this time, the time when the two signals are generated is almost the same, so as to judge that it is a cosmic ray signal and remove it. There will be accidental coincidence events, such as accidental coincidence between the signals generated by the sample itself and the anti-coincidence detector, which will cause the loss of real sample signals and reduce efficiency. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide an intelligent low-background αβ measuring instrument to solve the technical problem of the relatively large accidental coincidence probability of traditional single anti-coincidence detectors.

[0005] To achieve the above object, the present invention provides the following technical solution: An intelligent low-background αβ measuring instrument includes a first scintillator and a second scintillator. Above the second scintillator, there are a first sample plate and a second sample plate for placing samples. Between the first scintillator and the second scintillator, there are a first main detector and a second main detector. Below the first scintillator, there is an upper anti-coincidence detector group, and below the second scintillator, there is a lower anti-coincidence detector group.

[0006] By adopting the above technical solution, the dual main detectors operate independently, supporting the simultaneous measurement of two samples, the first sample plate and the second sample plate, avoiding the time-consuming problem of serial measurement of traditional single-channel instruments, and is especially suitable for high-throughput scenarios of a large number of samples.

[0007] Further, the upper anti-coincidence detector group includes a first anti-coincidence detector, a second anti-coincidence detector, and a third anti-coincidence detector, and the lower anti-coincidence detector group includes a fourth anti-coincidence detector, a fifth anti-coincidence detector, and a sixth anti-coincidence detector.

[0008] By adopting the above technical solution, the accidental coincidence events of the traditional single-anti-coincidence system are completely eliminated through redundant layout and hierarchical identification logic. When the sample signal is accidentally synchronized with the noise of a single anti-coincidence detector, the true signal can be retained because the triple time matching conditions of "upper and lower anti-coincidence + main detector" cannot be met, thus avoiding the problem of data loss caused by misjudgment in traditional settings.

[0009] Furthermore, a lead chamber is arranged on the outside of the measuring instrument, the outer circumference of the lead chamber is composed of 7.5 cm lead + 1.5 cm steel shell, and the top and bottom thickness of the lead chamber is 10 cm.

[0010] By adopting the above technical solution, efficient shielding of gamma rays and environmental background radiation is achieved. For example, the total weight of the lead chamber is 480kg, and the layered lead-steel composite setting can attenuate the radiation intensity of the external environment to less than one thousandth of the original value.

[0011] Furthermore, the first main detector and the second main detector are main detectors coupled with silicon photomultiplier tubes, and the upper anti-coincidence detector group and the lower anti-coincidence detector group are anti-coincidence detectors coupled with silicon photomultiplier tubes.

[0012] By adopting the above technical solution, the silicon photomultiplier tube coupling can reduce its volume by more than 90% compared with traditional photomultiplier tubes, and its power consumption is reduced to less than 12 watts, providing a hardware foundation for compact multi-channel design.

[0013] Furthermore, the first scintillator and the second scintillator are S parallel plate plastic scintillators with a diameter of 200 mm and a thickness of 30 mm.

[0014] By adopting the above technical solution, its large-size active area can maximize the contact area between the sample and the detector and reduce the geometric efficiency loss.

[0015] Furthermore, the first sample plate and the second sample plate are made of 0.5 mm stainless steel material, and the surface is a disc-shaped setting with a depth of 2 mm and a diameter of Φ45 mm.

[0016] By adopting the above technical solutions, the geometry of the sample plate is optimized to ensure uniform spreading of the sample and reduce counting losses caused by edge effects. The dish-shaped structure can prevent powder or liquid samples from overflowing and is suitable for a variety of sample types such as solids, liquids, and aerosols, meeting the detection needs of drinking water radioactivity indicators.

[0017] In summary, the present invention mainly has the following beneficial effects:

[0018] 1. The present invention adopts silicon photomultiplier tube, which reduces the volume and space. The signals of the two anti-coincidence detectors above and below the main detector are first identified by themselves and confirmed as cosmic rays, and then identified with the signals of the main detector, so that the signals generated by cosmic rays are 100% accurately shielded. The signal generated by the sample can only produce a signal in one of the anti-coincidence detectors, so there is no accidental coincidence.

[0019] 2. The present invention replaces the traditional photomultiplier tube with a silicon photomultiplier tube. Compared with the traditional photomultiplier tube, the silicon photomultiplier tube has the advantages of small size and low cost. The original measurement system has a height of 100 cm and a weight of 600 kg. After being replaced with the silicon photomultiplier tube, the height and overall weight are reduced by half. In addition, the silicon photomultiplier tube does not require a high-voltage power supply, which invisibly reduces a lot of costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the internal structure of the present invention;

[0021] Figure 2 It is a schematic diagram of the operation flow structure of the present invention.

[0022] In the figure: 1. first main detector; 2. second main detector; 3. first scintillator; 4. second scintillator; 5. first anti-coincidence detector; 6. second anti-coincidence detector; 7. third anti-coincidence detector; 8. fourth anti-coincidence detector; 9. fifth anti-coincidence detector; 10. sixth anti-coincidence detector; 11. first sample plate; 12. second sample plate; 13. lead chamber. DETAILED DESCRIPTION

[0023] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0024] In this embodiment:

[0025] An intelligent low-background αβ measuring instrument, such as Figure 1-2As shown, it includes a first scintillator 3 and a second scintillator 4. A first sample plate 11 and a second sample plate 12 for placing samples are placed above the second scintillator 4. A first main detector 1 and a second main detector 2 are arranged between the first scintillator 3 and the second scintillator 4. An upper anti-coincidence detector group is arranged below the first scintillator 3, and a lower anti-coincidence detector group is arranged below the second scintillator 4. The dual main detectors operate independently and support simultaneous measurement of the first sample plate 11 and the second sample plate 12 of two samples, avoiding the time-consuming serial measurement problem of traditional single-channel instruments, and is particularly suitable for high-throughput scenarios of large batches of samples. At the same time, the full-space coverage setting of the upper anti-coincidence detector group and the lower anti-coincidence detector group effectively solves the problem of cosmic ray leakage shielding caused by blind spots in traditional single-reverse coincidence systems.

[0026] See also Figure 1 , Figure 2 The upper anti-coincidence detector group includes a first anti-coincidence detector 5, a second anti-coincidence detector 6, and a third anti-coincidence detector 7; the lower anti-coincidence detector group includes a fourth anti-coincidence detector 8, a fifth anti-coincidence detector 9, and a sixth anti-coincidence detector 10. Through redundant layout and hierarchical discrimination logic, the accidental coincidence events of the traditional single anti-coincidence system are completely eliminated. When the sample signal is accidentally synchronized with the noise of a single anti-coincidence detector, the true signal is retained because the triple time matching conditions of "upper and lower anti-coincidence + main detector" cannot be met, thereby avoiding the problem of data loss caused by misjudgment in traditional settings. At the same time, the multi-anti-coincidence detector adopts silicon photomultiplier tube coupling technology, and its compact size allows high-density integration, which not only solves the space limitation but also improves the anti-electromagnetic interference capability.

[0027] See also Figure 1 , Figure 2 A lead chamber 13 is arranged on the outside of the measuring instrument. The outer circumference of the lead chamber 13 is composed of 7.5 cm lead + 1.5 cm steel shell. The top and bottom thickness of the lead chamber are 10 cm, which realizes efficient shielding of gamma rays and environmental background radiation. For example, the total weight of the lead chamber is 480 kg. Through the layered lead-steel composite setting, the external environmental radiation intensity can be attenuated to less than one thousandth of the original value. Combined with the active shielding of cosmic rays by the anti-coincidence detector, it meets the requirements of the national standard GB / T 11682-2008 for instruments. At the same time, the modular setting of the lead chamber greatly simplifies the maintenance process.

[0028] See also Figure 1 , Figure 2The first main detector 1 and the second main detector 2 are both main detectors coupled with silicon photomultiplier tubes. The upper anti-coincidence detector group and the lower anti-coincidence detector group are both anti-coincidence detectors coupled with silicon photomultiplier tubes. Compared with traditional photomultiplier tubes, the volume of silicon photomultiplier tubes is reduced by more than 90%, and the power consumption is reduced to less than 12 watts, which provides a hardware foundation for compact multi-channel design. For example, the high photon detection efficiency and single-photon sensitivity of silicon photomultiplier tubes can significantly improve the response capability to weak α signals. Combined with programmable high-voltage technology, dynamic optimization of α / β thresholds can be achieved to ensure measurement stability.

[0029] See also Figure 1 , Figure 2 The first scintillator 3 and the second scintillator 4 are S parallel plate plastic scintillators with a diameter of 200 mm and a thickness of 30 mm. The large active area can maximize the contact area between the sample and the detector and reduce the geometric efficiency loss. At the same time, the pollution resistance and low hygroscopicity of the plastic scintillator make it suitable for direct measurement of liquid samples, avoiding the performance degradation problem of traditional ZnS (Ag) scintillators caused by moisture absorption.

[0030] See also Figure 1 , Figure 2 The first sample plate 11 and the second sample plate 12 are made of 0.5mm stainless steel material, with a surface in a dish shape with a depth of 2mm and a diameter of Φ45mm. The sample plate geometry is optimized to ensure uniform spreading of the sample and reduce counting losses caused by edge effects. The dish structure can prevent powder or liquid sample overflow and is suitable for a variety of sample types such as solids, liquids, and aerosols to meet the detection needs of drinking water radioactivity indicators. At the same time, the anti-corrosion properties and easy cleaning of stainless steel significantly reduce the risk of cross contamination.

[0031] The implementation principle of this embodiment is:

[0032] Main detector: low-background αβ scintillator is used. The scintillator is made of α scintillator and β scintillator sprayed on a plexiglass plate with a thickness of 5-6mm and a diameter of Ф50mm. It is made by a special process. The α scintillator is on the outer layer and the β scintillator is on the inner layer. Due to the short range of α particles, when α particles enter the α scintillator, all energy is lost in the ZnS (Ag) material, causing scintillation and generating α signals. Due to the strong penetrating ability, β particles pass through the ZnS (Ag) material and enter the β scintillator, generating β signals, which are then converted into electrons through the photocathode of the silicon photomultiplier tube, and then converted into detectable current signals through various levels of amplification of the dynamometer stage and enter the back-end electronics;

[0033] Anti-coincidence detector: The anti-coincidence detector is mainly used to reduce the background (β background) of muons in cosmic rays, and can also partially reduce the background generated by environmental radiation. The anti-coincidence detector is composed of a 200mm Ф, 30mm thick S parallel plate plastic scintillator and a silicon photomultiplier tube. The photomultiplier tube is provided with positive high voltage by an external high-voltage source, and the signal it generates is used as the anti-coincidence signal. Except for the coupling surface with the photomultiplier tube, the rest of the plastic scintillator is coated with a reflective layer of about 0.5mm titanium dioxide to improve the anti-coincidence efficiency. Similarly, the signal generated by the crystal is converted into electrons through the photocathode of the photomultiplier tube, and is converted into a detectable current signal through various levels of amplification of the dynamometer stage, and enters the back-end anti-coincidence electronic system;

[0034] Electronic circuit: The electronic circuit consists of amplification, discrimination, shaping, coincidence and anti-coincidence, high and low voltage power supply, data acquisition, computer interface and printer, etc. The signals of the main detector and anti-coincidence detector must be amplified, and the α and β signals must be discriminated by amplitude, and then these signals are shaped respectively. If the discrimination time of the β signal is consistent with the signal time of the anti-coincidence detector, it means that it is a signal generated by external cosmic rays and will be removed, thereby reducing the β background;

[0035] The upper / lower groups of anti-coincidence detectors and the first main detector 1 and the second main detector 2 continuously measure signals, which enter their respective discriminators after passing through their own amplification circuits. The discriminators determine the arrival time of the signals according to the time when the amplitude crosses the threshold. When the signal times of the upper / lower groups of anti-coincidence detectors are determined to be consistent in the coincidence circuit, a signal is output to the anti-coincidence circuit for comparison with the signals of the first and second main detectors. Once the first and second main detectors also have signals at the same time, it means that the signals are generated by cosmic rays in the main detectors and the upper / lower groups of anti-coincidence detectors. The signals are judged as interference signals and removed, thereby reducing the background. The circuit system truly reflects the actual measurement and reduces accidental errors.

[0036] Although an embodiment of the present invention has been shown and described, this specific embodiment is only an explanation of the present invention and is not a limitation of the invention. The specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. After reading this specification, those skilled in the art may make modifications, substitutions and variations to the embodiments without creative contribution as needed without departing from the principles and purpose of the present invention. However, as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. An intelligent low-background αβ measuring instrument, characterized in that: The invention comprises a first scintillator (3) and a second scintillator (4); a first sample plate (11) and a second sample plate (12) for placing samples are placed above the second scintillator (4); a first main detector (1) and a second main detector (2) are arranged between the first scintillator (3) and the second scintillator (4); an upper anti-coincidence detector group is arranged below the first scintillator (3); and a lower anti-coincidence detector group is arranged below the second scintillator (4).

2. The intelligent low-background αβ measuring instrument according to claim 1, characterized in that: The upper anti-coincidence detector group includes a first anti-coincidence detector (5), a second anti-coincidence detector (6), and a third anti-coincidence detector (7), and the lower anti-coincidence detector group includes a fourth anti-coincidence detector (8), a fifth anti-coincidence detector (9), and a sixth anti-coincidence detector (10).

3. The intelligent low-background αβ measuring instrument according to claim 1, characterized in that: It also includes a lead chamber (13), which covers the outside of the measuring instrument. The outer circumference of the lead chamber (13) is composed of 7.5 cm lead + 1.5 cm steel shell, and the top and bottom thickness of the lead chamber are 10 cm.

4. The intelligent low-background αβ measuring instrument according to claim 1, characterized in that: The first main detector (1) and the second main detector (2) are both main detectors coupled with silicon photomultiplier tubes, and the upper anti-coincidence detector group and the lower anti-coincidence detector group are both anti-coincidence detectors coupled with silicon photomultiplier tubes.

5. The intelligent low-background αβ measuring instrument according to claim 1 is characterized in that: The first scintillator (3) and the second scintillator (4) are S parallel plate plastic scintillators with a diameter of 200 mm and a thickness of 30 mm.

6. The intelligent low-background αβ measuring instrument according to claim 1, characterized in that: The first sample plate (11) and the second sample plate (12) are made of 0.5 mm stainless steel material, and the surface is a disc-shaped setting with a depth of 2 mm and a diameter of Φ45 mm.

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