Ultralow background liquid scintillation counter

Abstract

The embodiment of the utility model discloses an ultra-low background liquid scintillation counter, which comprises three main photomultipliers which are radially arranged in the same horizontal plane at equal intervals, and a counting chamber for measurement is formed among the end parts of the three main photomultipliers; the number of the auxiliary photomultipliers is three, each auxiliary photomultiplier is arranged between two adjacent main photomultipliers at equal intervals, and the auxiliary photomultipliers and the main photomultipliers are arranged in a one-to-one correspondence mode and located in the same horizontal plane. Three through hole structures which are arranged at equal intervals are arranged on the side wall of the plastic scintillator at intervals and are used for adaptively arranging the three main photomultipliers, and three concave structures which are arranged at equal intervals are arranged on the side wall of the plastic scintillator at intervals and are used for adaptively arranging the end parts of the auxiliary photomultipliers; a lead shield; the photomultiplier has a shape and a structure matched with the main photomultiplier, the auxiliary photomultiplier and the plastic scintillator; a copper lining layer is adaptively arranged between the lead shielding body and the plastic scintillator; and the outer shell is adaptively arranged outside the lead shielding body.

Description

Technical Field

[0001] This invention belongs to the field of nuclear radiation detection technology, specifically relating to an ultra-low background liquid scintillation counter. Background Technology

[0002] Liquid scintillation counters are widely used in industries such as industry, agriculture, biomedicine, environmental science, archaeology, and geology. In radiation monitoring, liquid scintillation counters can be used to measure alpha and beta radionuclides, such as... 3 H, 14 C 32 P, 90 Sr, total α, total β, etc. With the development of sample processing technology and the improvement of nuclide separation methods, more and more radionuclides will be measured using liquid scintillation counters.

[0003] In liquid scintillation meters, passive shielding and active shielding are generally used to reduce the impact of background on the counting.

[0004] Passive shielding involves surrounding the detector with metallic materials to reduce the impact of environmental radiation on detector counts. High atomic number materials such as iron, lead, tungsten, lead-boron polyethylene, etc., are commonly used to construct light-shielding shields, which are tightly fitted to the internal detector. The thickness of the shield has a significant impact on background counts. Because high atomic number materials produce characteristic X-rays when exposed to gamma rays, which affect background counts, low atomic number materials are typically chosen as the inner lining of the shield to block these characteristic X-rays.

[0005] Active shielding utilizes anti-coincidence signal processing technology. An anti-coincidence detector is placed outside the main detector. For rays passing through both the anti-coincidence and main detectors, if energy is deposited in the scintillators of both detectors, both will generate signals simultaneously. The anti-coincidence method considers the main detector's input signal invalid and does not record it, thus reducing the background count. This type of liquid scintillator uses four photomultiplier tubes in its counting chamber: three receive the optical signal from the main detector, and the fourth photomultiplier tube receives the optical signal from the anti-coincidence detector and is positioned below the main detector. Passive shielding uses a low-background lead shell.

[0006] The background radiation of liquid scintillation counters mainly comes from cosmic rays above. The anti-coincidence detector design on the lower side provides poor shielding against this background radiation, severely affecting the detector's measurement accuracy. The lead shell is relatively large in size and mass, significantly occupying valuable space within the entire device and resulting in high production and transportation costs. Utility Model Content

[0007] In view of this, some embodiments disclose ultra-low background liquid scintillation counters, including:

[0008] Main photomultiplier tubes; three main photomultiplier tubes are arranged radially at equal intervals in the same horizontal plane; a counting chamber for measurement is formed between the ends of the three main photomultiplier tubes;

[0009] Auxiliary photomultiplier tubes; There are three auxiliary photomultiplier tubes. Each auxiliary photomultiplier tube is equally spaced between two adjacent main photomultiplier tubes. The auxiliary photomultiplier tubes correspond one-to-one with the main photomultiplier tubes and are located in the same horizontal plane.

[0010] Plastic scintillator; the plastic scintillator is a hollow cylindrical structure; three equally spaced through holes are provided on the side wall of the cylindrical structure, and three main photomultiplier tubes are respectively arranged in the hollow part of the plastic scintillator through one through hole to form a counting chamber; three equally spaced recesses are provided on the side wall of the cylinder to accommodate the ends of the auxiliary photomultiplier tubes.

[0011] Lead shield; the lead shield has a shape and structure adapted to the main photomultiplier tube, the auxiliary photomultiplier tube and the plastic scintillator; a copper inner liner is adapted between the lead shield and the plastic scintillator;

[0012] The outer casing is fitted to the outside of the lead shield.

[0013] Furthermore, in some embodiments of the ultra-low volume liquid scintillation counter, the photomultiplier tubes and auxiliary photomultiplier tubes are arranged in a one-to-one correspondence and are located on the same straight line, with the test ends corresponding to each other.

[0014] In some embodiments of the ultra-low volume liquid scintillation counter, a lead shield adapted to the main photomultiplier tube extends radially outward to form a first lead ear; and a lead shield adapted to the auxiliary photomultiplier tube extends radially outward to form a second lead ear.

[0015] Some embodiments disclose an ultra-low volume liquid scintillation counter in which the housing has a shape and structure adapted to a first lead lug, and a support frame for supporting the first lead lug is provided on the outer wall of the housing.

[0016] Some embodiments disclose an ultra-low volume liquid scintillation counter in which the size of the main photomultiplier tube is larger than that of the auxiliary photomultiplier tube, and the performance parameters of the main photomultiplier tube are the same as those of the auxiliary photomultiplier tube.

[0017] Some embodiments of the ultra-low volume liquid scintillation counter disclosed also include a lead chamber door, adapted to be disposed above the lead shield, for sealing the counting chamber.

[0018] Some embodiments disclose an ultra-low volume liquid scintillation counter in which the lead shield is composed of an upper lead shield and a lower lead shield.

[0019] Some embodiments of the ultra-low volume liquid scintillation counter disclose a Z-shaped connection between the upper lead shield and the lower lead shield.

[0020] Some embodiments disclose ultra-low bulk liquid scintillation counters with a lead shield thickness of not less than 10 cm.

[0021] Some embodiments of the ultra-low volume liquid scintillation counter disclose a support for placing the sample to be tested in a counting chamber formed between the main photomultiplier tubes.

[0022] The ultra-low background liquid scintillation counter disclosed in this embodiment of the invention arranges three main photomultiplier tubes and three auxiliary photomultiplier tubes at equal intervals on the same horizontal plane, with each auxiliary photomultiplier tube corresponding to one main photomultiplier tube, forming a symmetrical structure. The three main photomultiplier tubes serve as the main detectors, and the three auxiliary photomultiplier tubes combined with a plastic scintillator serve as the anti-coincidence detectors. The three main detectors and the anti-coincidence detectors are located in the same plane, which can effectively eliminate the background count and improve the detection accuracy of the main detectors. At the same time, the use of three main photomultiplier tubes as the main detectors improves the detection efficiency. Moreover, the instrument has a small overall size, stable structure, and greatly reduces the weight of the entire device. Attached Figure Description

[0023] Figure 1 Schematic diagram of the ultra-low background liquid scintillation counter structure disclosed in some embodiments Figure 1 ;

[0024] Figure 2 Schematic diagram of the ultra-low background liquid scintillation counter structure disclosed in some embodiments Figure 2 .

[0025] Figure Labels

[0026] 1. Main photomultiplier tube; 2. Substitute photomultiplier tube

[0027] 3 Plastic scintillator 4 Copper liner

[0028] 5. Lead shielding body; 6. Outer shell.

[0029] 7 Second lead ear 8 Second lead ear

[0030] 9. Lead chamber sliding door; 10. Support frame

[0031] 100 Counting Room Detailed Implementation

[0032] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in these embodiments of the present invention, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used herein is merely for describing particular implementations and is not intended to limit the scope of the disclosure of these embodiments.

[0033] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; other test methods and technical means not specifically noted in this invention refer to test methods and technical means commonly used by one of ordinary skill in the art.

[0034] The terms “basic” and “approximately” used in this document are to describe small fluctuations. For example, they can mean less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Numerical data presented or expressed in range format in this document are used for convenience and brevity only, and should therefore be flexibly interpreted to include not only the explicitly listed values ​​that define the range, but also all independent values ​​or subranges contained within that range. For example, a numerical range of “1–5%” should be interpreted to include not only the explicitly listed values ​​from 1% to 5%, but also the independent values ​​and subranges within the indicated range. Thus, this numerical range includes independent values ​​such as 2%, 3.5%, and 4%, and subranges such as 1%–3%, 2%–4%, and 3%–5%, etc. This principle also applies to ranges that list only one value. Furthermore, this interpretation applies regardless of the width of the range or the characteristics described.

[0035] In this document, including in the claims, conjunctions such as "comprising," "including," "with," "having," "containing," "involving," and "accommodating" are understood to be open-ended, meaning "including but not limited to." Only the conjunctions "consisting of" and "composed of" are closed conjunctions.

[0036] To better illustrate the content of this utility model, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this utility model can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and equipment well known to those skilled in the art are not described in detail, in order to highlight the main points of this utility model.

[0037] Without conflict, the technical features disclosed in the embodiments of this utility model can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this utility model.

[0038] In some implementations, such as Figure 1 , Figure 2 As shown, Figure 1 This is a top-view cross-sectional diagram of a liquid scintillation meter. Figure 2 for Figure 1 A cross-sectional view at the location indicated by the dashed arrow; the ultra-low background liquid scintillation counter includes:

[0039] The main photomultiplier tube 1; three main photomultiplier tubes 1 are arranged radially at equal intervals in the same horizontal plane; the included angle between the three main photomultiplier tubes is 120°, and the ends of the three main photomultiplier tubes 1 are combined with each other to form a counting chamber 100 for measurement between the ends; a sample holder for placing the sample to be tested is provided in the counting chamber 100; the three main photomultiplier tubes 1 serve as the main detectors of the liquid scintillation instrument for the absolute measurement of nuclides;

[0040] Auxiliary photomultiplier tubes 2; There are three auxiliary photomultiplier tubes 2, each of which is equally spaced between two adjacent main photomultiplier tubes 1. The auxiliary photomultiplier tubes 2 and the main photomultiplier tubes 1 are arranged in a one-to-one correspondence and are located in the same horizontal plane; the included angle between the three auxiliary photomultiplier tubes 2 is 120°; the detector head of the corresponding auxiliary photomultiplier tube 2 is set facing the detector head of the main photomultiplier tube 1, corresponding to each other, and the two are located on the same straight line;

[0041] The plastic scintillator 3 is a hollow cylindrical structure with a hollow cavity and an annular sidewall forming the hollow cavity. Three equally spaced through-hole structures are arranged on the annular sidewall, corresponding to three main photomultiplier tubes (PMTUs). The end probes of the three main PMTUs 1 are arranged correspondingly within the hollow cavity of the plastic scintillator 3 through the three through-hole structures, forming a counting chamber 100. Three equally spaced recessed structures are also arranged on the annular sidewall, corresponding to the positions of the three auxiliary PMTUs. The ends of the auxiliary PMTUs are fitted into these recessed structures, meaning the annular sidewall of the plastic scintillator 3 completely encloses the ends of the auxiliary PMTUs. The three auxiliary PMTUs 2 and the plastic scintillator 3 together form the anti-coincidence detector of the liquid scintillation counter, providing active shielding against nuclides.

[0042] Since the background count mainly comes from cosmic rays above, the probability of the detector probes on the same plane being affected by the background energy is the same. The anti-coincidence detector set on the same horizontal plane can effectively subtract the background count of the main detector.

[0043] The lead shield 5 has a shape and structure adapted to the main photomultiplier tube 1, the auxiliary photomultiplier tube 2, and the plastic scintillator 3; a copper inner liner 4 is adapted between the lead shield 5 and the plastic scintillator 3; wherein, the lead shield 5 adapted to the main photomultiplier tube 1 extends radially outward to form a first lead lug 7; the lead shield 5 adapted to the auxiliary photomultiplier tube 2 extends radially outward to form a second lead lug 8; the size of the main photomultiplier tube is larger than that of the auxiliary photomultiplier tube, and the performance parameters of the main photomultiplier tube are the same as those of the auxiliary photomultiplier tube, and correspondingly, the size of the first lead lug 7 is larger than that of the second lead lug 8; the thickness of the lead shield 5 is not less than 10 cm; the first and second lead lugs can prevent light leakage at the tail end wiring opening of the photomultiplier tube.

[0044] The outer shell 6 is adapted to be disposed outside the lead shield 5 to strengthen the lead shield 5 and ensure its structural stability; the outer shell 6 has a shape and structure adapted to the first lead lug 7, and a support frame 10 for supporting the first lead lug 7 is provided on the outer wall of the outer shell; the lead chamber push door 9 is adapted to be disposed above the lead shield 5 to close the counting chamber 100.

[0045] The lead shield 5 is composed of two parts: an upper lead shield 51 and a lower lead shield 52. The connection between the upper lead shield 51 and the lower lead shield 52 is Z-shaped to prevent light leakage at the connection.

[0046] The ultra-low background liquid scintillation counter disclosed in this embodiment of the invention arranges three main photomultiplier tubes and three auxiliary photomultiplier tubes at equal intervals on the same horizontal plane, with each auxiliary photomultiplier tube corresponding to one main photomultiplier tube, forming a symmetrical structure. The three main photomultiplier tubes serve as the main detectors, and the three auxiliary photomultiplier tubes combined with a plastic scintillator serve as the anti-coincidence detectors. The three main detectors and the anti-coincidence detectors are located in the same plane, which can effectively eliminate the background count and improve the detection accuracy of the main detectors. At the same time, the use of three main photomultiplier tubes as the main detectors improves the detection efficiency. Moreover, the instrument has a small overall size, stable structure, and greatly reduces the weight of the entire device.

[0047] The technical solutions and technical details disclosed in the embodiments of this utility model are merely illustrative of the inventive concept of this utility model and do not constitute a limitation on the technical solutions of the embodiments of this utility model. Any conventional changes, substitutions or combinations made to the technical details disclosed in the embodiments of this utility model have the same inventive concept as this utility model and are within the protection scope of the claims of this utility model.

Claims

1. An ultra-low background liquid scintillation counter, characterized in that, The liquid scintillation counter comprises: a plurality of main photomultiplier tubes, three of which are arranged in a same horizontal plane at equal intervals in a radial manner; a plurality of auxiliary photomultiplier tubes, three of which are arranged in a same horizontal plane at equal intervals between two adjacent main photomultiplier tubes in a one-to-one correspondence with the main photomultiplier tubes; a plastic scintillator in a hollow cylindrical structure, wherein a plurality of through holes are arranged at equal intervals on a side wall of the cylindrical structure, and the three main photomultiplier tubes are arranged in a one-to-one correspondence in the hollow part of the plastic scintillator through the through holes to form a counting chamber; and a plurality of recesses are arranged at equal intervals on the side wall of the cylindrical structure to accommodate the end portions of the auxiliary photomultiplier tubes; a lead shielding body having a shape and structure matched with the main photomultiplier tubes, the auxiliary photomultiplier tubes and the plastic scintillator, and a copper lining layer arranged between the lead shielding body and the plastic scintillator; an outer shell arranged outside the lead shielding body.

2. The ultra-low background liquid scintillation counter of claim 1, wherein, The main photomultiplier tubes and the auxiliary photomultiplier tubes are arranged in a one-to-one correspondence on a same straight line, and the test ends are arranged in a one-to-one correspondence.

3. The ultra-low background liquid scintillation counter of claim 1, wherein, The lead shielding body matched with the main photomultiplier tubes extends radially outward to form a first lead ear. The lead shielding body matched with the auxiliary photomultiplier tubes extends radially outward to form a second lead ear.

4. The ultra-low background liquid scintillation counter of claim 3, wherein, The outer shell has a shape and structure matched with the first lead ear, and a support frame is arranged on an outer wall of the outer shell to support the first lead ear.

5. The ultra-low background liquid scintillation counter of claim 1, wherein, The main photomultiplier tubes have a size larger than that of the auxiliary photomultiplier tubes, and the main photomultiplier tubes have the same performance parameters as the auxiliary photomultiplier tubes.

6. The ultra-low background liquid scintillation counter of claim 1, wherein, Further comprising: a lead chamber push door arranged above the lead shielding body to close the counting chamber.

7. The ultra-low background liquid scintillation counter of claim 1, wherein, The lead shielding body is composed of an upper lead shielding body and a lower lead shielding body.

8. The ultra-low background liquid scintillation counter of claim 7, wherein, The connection part between the upper lead shielding body and the lower lead shielding body is in a Z shape.

9. The ultra-low background liquid scintillation counter of claim 1, wherein, The thickness of the lead shielding body is not less than 10 cm.

10. The ultra-low background liquid scintillation counter of claim 1, wherein, A support for placing a sample to be tested is arranged in the counting chamber formed between the main photomultiplier tubes.

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