A front-end package structure of a low-temperature portable scintillator detector

Abstract

The application discloses a front-end packaging structure of a low-temperature portable scintillator detector, which comprises a scintillation crystal, an adapter plate, a micro-channel heat sink and a metal shielding shell; the metal shielding shell is internally provided with a sensor array, a ceramic plate, a crystal fixing frame, a fixing frame, a fixing plate, a cold storage block and a semiconductor refrigeration sheet; the opening of the metal shielding shell is connected with the micro-channel heat sink to form a closed structure; the scintillation crystal is located inside a cavity formed by the crystal fixing frame, the fixing frame, the sensor array and the ceramic plate; the cold storage block is located between the cold surface of the semiconductor refrigeration sheet and the ceramic plate, and the devices are filled with heat-conducting silica gel; one end of the adapter plate is electrically connected with the sensor array through the ceramic plate, and the other end extends to outside the shell; the space among the ceramic plate, the fixing frame and the cold storage block is filled with electronic potting glue; and the gap among the crystal fixing frame, the fixing frame, the metal shielding shell and the micro-channel heat sink is filled with polyurethane foam. The application can effectively reduce the temperature of the sensor array and improve the energy resolution of the detector.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of detector device manufacturing, and relates to a front-end packaging structure of a low-temperature portable scintillator detector. BACKGROUND

[0002] An inorganic scintillator detector is a high-energy particle (ray) detector widely applied in the fields of nuclear medical imaging, high-energy physics, safety inspection, industrial nondestructive testing, etc.

[0003] The inorganic scintillator detector utilizes an inorganic scintillation crystal to emit scintillation light by interacting with high-energy neutral particles (such as neutrons and gamma rays), detects the light signal by means of a high-sensitivity photoelectric conversion device, and converts the light signal into an electric signal of a certain size and shape. An electronic system is used to realize signal amplification, filtering and processing, and analyze the energy distribution and spectral characteristics of high-energy particles. In order to quickly and efficiently detect weak light signals in the inorganic scintillation crystal, a photoelectric conversion device traditionally used in the inorganic scintillator detector is a photomultiplier tube (PMT). The device has the advantages of high sensitivity, fast response capability, high gain and large detection range, and is widely applied. However, the device has the disadvantages of large size, high cost, and the need for a high working voltage (1000 volts or more) for detecting weak light, which leads to a large size and weight and poor integration of the inorganic scintillator detector. In comparison, a silicon photomultiplier (SiPM) as a new generation of electric conversion device has the advantages of small size, light weight, compact structure, low bias voltage and insensitivity to magnetic fields. The SiPM can easily realize planar array design and be attached to the inorganic scintillation crystal, improve the photon detection efficiency, and reduce the mass and size of the inorganic scintillator detector by means of high integration. However, the thermal noise of the SiPM is extremely high, reaching 100 kHz / mm 2 at room temperature, and the energy resolution capability is far inferior to that of the PMT. Effective temperature control measures must be taken to effectively reduce the noise and improve the energy resolution capability.

[0004] Studies have shown that the thermal noise of SiPM can be reduced by an order of magnitude for every 40℃ reduction. Using a high-efficiency refrigeration system to control the temperature of the SiPM detector below-25℃ or even lower is the key to ensuring the energy resolution performance of inorganic scintillator detectors. In addition, running SiPM at low temperature will improve the anti-radiation performance of SiPM and significantly improve the service life of the detector. However, under the premise of meeting the portable requirements, it is difficult to realize the refrigeration of SiPM array. First, in order to improve the quality of the readout signal, there must be a high-density signal line between the SiPM array and the electronic system to ensure that the signal from each SiPM to the electronics is independent of each other; second, under the above premise, the SiPM array should be in a dry and sealed environment to avoid SiPM sensor frosting or even short circuit; finally, under the premise of meeting the refrigeration requirements of SiPM array, the front-end packaging structure of the detector should be small and compact to meet the portability requirements of the whole machine. SUMMARY

[0005] The low-temperature portable scintillator detector front-end packaging structure of the present application aims to control the SiPM array surface temperature below 25℃, thereby improving the energy resolution of the detector by an order of magnitude, and the front-end structure is small and compact to meet the portability requirements of the whole machine.

[0006] The technical scheme of the present application is:

[0007] A high-energy resolution low-temperature portable scintillator detector front-end packaging structure, which is mainly characterized by comprising a scintillation crystal 1, a SiPM sensor array 2, a ceramic plate 3, an adapter plate 4, a crystal fixing frame 5, a SiPM fixing frame 6, a sealing ring 7, a fixing plate 8, a cold storage block 9, a semiconductor refrigeration piece 10, a micro-channel heat sink 11, a metal shielding shell 12, silicon oil 13, heat-conducting silicone 14, electronic potting glue 15 and polyurethane foaming glue 16.

[0008] The scintillation crystal 1 is located inside the cavity composed of the crystal holder 5, the SiPM holder 6, the sealing ring 7, the SiPM sensor array 2 and the ceramic plate 3. The SiPM sensor array 2 is welded on the ceramic plate 3, and the SiPM sensor array 2 and the scintillation crystal 1 form a gap by fixing the ceramic plate 3 on the SiPM holder 6, which is filled with silicone oil 13, on the one hand to avoid frosting of the SiPM sensor array 2 at low temperature, leading to device damage; on the other hand, to increase the light transmittance between the SiPM sensor array and the crystal. In order to ensure the air tightness between the crystal holder 5 and the SiPM holder 6, the two are fixed and compressed by the first screw 17 to form a seal with the sealing ring 7. In order to control the distance between the SiPM sensor array 2 and the scintillation crystal 1, the scintillation crystal 1 and the SiPM holder 6 both have a stepped structure, and the scintillation crystal 1 is clamped by the second screw 18 and the threaded hole of the crystal holder 5. In order to ensure the air tightness inside the cavity and prevent water vapor from entering the cavity, the gap between the scintillation crystal 1 and the crystal holder 5 is also filled with silicone oil 13.

[0009] The cold block 9 is located between the cold side of the semiconductor cooling sheet 10 and the ceramic plate 3, and the hot side of the semiconductor cooling sheet 10 is a micro-channel heat sink 11. In order to reduce the contact thermal resistance between each device, the devices are filled with heat-conducting silicone 14. The cold block 9 is a hollow structure, which can not only ensure the heat transfer performance, but also reduce the specific heat of the cold block and improve the cooling rate of the SiPM array. When the semiconductor cooling sheet 10 is started, the heat of the SiPM sensor array 2, the ceramic substrate 3 and the cold block begins to transfer to the cold side of the semiconductor cooling sheet 10 to achieve cooling. Under the Peltier effect of the semiconductor cooling sheet 10, the heat is transferred to the micro-channel heat sink 11 through the hot side of the semiconductor cooling sheet 10, and the circulating cooling 19 medium in the micro-channel of the micro-channel heat sink 11 carries away the heat and transfers it to the external environment.

[0010] The adapter plate 4 is a rigid-flexible combined plate composed of three FR4 plates and two flexible plates 20. The first FR4 plate 21 at both ends has through holes and connectors 22 for electrical connection and mechanical fixation of the ceramic plate 3 and the rear-end electronics. The second FR4 plate 23 in the middle has threaded holes, which is fixed on the fixing plate 8 of the "L" type plastic structure by the third screw 24, and the fixing plate 8 is fixed on the crystal holder 5 by the fourth screw 25.

[0011] In order to avoid the low-temperature frost of the connector 22 between the ceramic plate 3 and the adapter plate 4, and the overflow of the silicon oil 13 between the SiPM sensor array 2 and the scintillation crystal 1, a large amount of electronic potting glue 15 is filled in the space between the ceramic plate 3, the SiPM fixing frame 6 and the cold storage block 9, and covers the connector between the ceramic plate 3 and the adapter plate 4; in order to avoid the overflow of the silicon oil 13 along the thread gap of the crystal fixing frame 5, the electronic potting glue 15 is filled on the upper side of the second screw 18 to achieve sealing.

[0012] The material of the metal shielding shell 12 is iron, which is used for electromagnetic shielding of the SiPM sensor array 2. The metal shielding shell 12 is spliced by multiple shell bodies and is fixed with the crystal fixing frame 5 and the SiPM fixing frame 6 through the fifth screw 26, and is fixed with the micro-channel heat sink 11 through the sixth screw 30. The crystal fixing frame 5 and the SiPM fixing frame 6 themselves have multiple hollow structures, and there are a large number of gap structures between the crystal fixing frame 5, the SiPM fixing frame 6, the metal shielding shell 12 and the micro-channel heat sink 11. A large amount of polyurethane foam 16 is filled in these hollow structures and gap structures, which can effectively reduce the heat loss of the SiPM sensor array 2 to the external environment, so as to control the SiPM sensor array 2 to reach the expected temperature.

[0013] Further, the scintillation crystal 1 is a cylindrical packaging structure composed of a stainless steel shell 27, a glass window 28 and a crystal 29, wherein the glass window 28 corresponds to the SiPM sensor array 2 on one side, and a gap of 0.1-0.2mm is formed between the SiPM sensor array 2 and the glass window 28, and the gap is filled with silicon oil 13.

[0014] Further, the SiPM sensor array 2 is a two-dimensional array detector composed of multiple SiPM sensors arranged closely, and the sensor array is an n*n array.

[0015] Further, the ceramic substrate is alumina ceramic, aluminum nitride or silicon nitride ceramic with good thermal conductivity, which is rectangular and larger than the SiPM sensor array 2 in size. The ceramic plate has no electronic devices except the connector 22, which can minimize the power consumption of the refrigeration sheet and ensure that the SiPM sensor array 2 reaches the target temperature.

[0016] Further, the crystal fixing frame 5 and the SiPM fixing frame 6 are made of heat-insulating plastic materials such as FR4 or nylon, and the hollow structures are large enough to fill polyurethane foam 16 to reduce SiPM heat loss; in addition, the threaded holes on the two structures must be embedded with internal thread to avoid slipping.

[0017] Further, the semiconductor refrigeration sheet 10 is a two-stage or three-stage semiconductor refrigeration sheet, which has a plane size close to or consistent with the SiPM sensor array 2 and the cold storage block 9, and can effectively control the thermal uniformity of the SiPM sensor array.

[0018] Further, the heat-conducting silica gel 14 is a cured heat-conducting silica gel, that is, the heat-conducting silica gel 14 is in a paste state at the beginning of implementation, but after 24 or 48 hours, the heat-conducting silica gel is cured into an elastic solid structure.

[0019] Further, the connectors between the ceramic plate 3 and the adapter plate 4 are sealed in the electronic potting glue 15, and low temperature cannot contact water vapor to cause frost, in addition, the second FR4 plate 23 in the middle of the adapter plate 4 is partially filled with electronic glue, and is fixed together with the fixed plate 8, and this structure can avoid that the electronic potting glue 15 is subjected to alternating loads during assembly, resulting in failure of the electronic potting glue 15.

[0020] Further, the entire packaging structure allows the filling of silicon oil in the small gap between the scintillation crystal 1 and the SiPM sensor array 2, which improves the SiPM photon acceptance efficiency, and realizes a small and compact packaging structure, meeting the needs of portable devices.

[0021] The effective effects of the present application are:

[0022] 1. The packaging structure can effectively reduce the temperature of the SiPM sensor array, reduce the thermal noise of the scintillator detector, and further improve the energy resolution of the detector.

[0023] 2. The SiPM sensor array and the crystal are packaged with 0.1-0.2mm read silicon oil at low temperature, which increases the photon collection efficiency and avoids low-temperature frosting of the SiPM sensor array, the ceramic plate and the solder joint therebetween, resulting in damage to the SiPM sensor.

[0024] 3. The adapter plate is a rigid-flexible combined plate composed of an FR4 plate and a flexible plate, which has poor heat conduction performance, and the electronic potting glue is used to seal the adapter plate, the ceramic plate and the silicon oil, which avoids low-temperature frosting or dewing of the connectors between the adapter plate and the ceramic plate, and avoids frosting or dewing caused by cooling of the other end of the adapter plate, resulting in short circuit;

[0025] 4. The SiPM sensor array is protected by heat-insulating plastic and polyurethane foam with excellent heat insulation performance, which reduces the heat loss of the SiPM to the outside and improves the refrigeration efficiency of the semiconductor refrigeration sheet;

[0026] 5. The front-end packaging structure of the scintillator detector is small, compact and light, meeting the needs of portable scintillator detector devices. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a front-end packaging structure diagram of a low-temperature portable scintillator detector.

[0028] Figure 2 It is an implementation structure diagram of a front-end packaging structure of a low-temperature portable scintillator detector.

[0029] Figure 3 It is a structure diagram of a scintillation crystal of a low-temperature portable scintillator detector.

[0030] In the figure: 1-scintillation crystal, 2-SiPM sensor array, 3-ceramic plate, 4-adapter plate, 5-crystal fixing frame, 6-SiPM fixing frame, 7-sealing ring, 8-fixing plate, 9-cold storage block, 10-semiconductor refrigeration piece, 11-micro-channel heat sink, 12-metal shielding shell, 13-silicone oil, 14-heat-conducting silicone, 15-electronic potting glue, 16-polyurethane foam glue, 17-first screw, 18-second screw, 19-circulating cooling medium, 20-flexible plate, 21-first FR4 plate, 22-connector, 23-second FR4 plate, 24-third screw, 25-fourth screw, 26-fifth screw, 27-stainless steel shell, 28-glass window, 29-crystal, 30-sixth screw. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0032] Figure 1 and Figure 2The front-end packaging structure diagram and the implementation structure diagram of the low-temperature portable scintillator detector are respectively shown, and the scintillation crystal 1 is located inside a cavity composed of a crystal fixing frame 5, a SiPM fixing frame 6, a sealing ring 7, a SiPM sensor array 2 and a ceramic plate 3. The SiPM sensor array 2 is welded on the ceramic plate 3, and the SiPM sensor array 2 and the scintillation crystal 1 form a gap by fixing the ceramic plate 3 on the SiPM fixing frame 6, and the gap is filled with silicone oil 13, which can prevent the SiPM sensor array 2 from frosting at low temperature and causing device damage, and increase the light transmittance between the SiPM sensor array and the crystal. In order to ensure the air tightness between the crystal fixing frame 5 and the SiPM fixing frame 6, the two are fixed and compressed by the first screw 17 to form a seal with the sealing ring 7. In order to control the distance between the SiPM sensor array 2 and the scintillation crystal 1, the scintillation crystal 1 and the SiPM fixing frame 6 both have a stepped structure, and the scintillation crystal 1 is clamped by the second screw 18 and the threaded hole of the crystal fixing frame 5. In order to ensure the air tightness inside the cavity and prevent water vapor from entering the cavity, the gap between the scintillation crystal 1 and the crystal fixing frame 5 is also filled with silicone oil 13.

[0033] The cold storage block 9 is located between the cold face of the semiconductor refrigeration sheet 10 and the ceramic plate 3, and the hot face of the semiconductor refrigeration sheet 10 is a micro-channel radiator 11. In order to reduce the contact thermal resistance between each device, the devices are filled with heat-conducting silicone 14. The cold storage block 9 is a hollow structure, and the hollow part can not only ensure the heat transfer performance, but also reduce the specific heat of the cold storage block and improve the cooling rate of the SiPM array. When the semiconductor refrigeration sheet 10 is started, the heat of the SiPM sensor array 2, the ceramic substrate 3 and the cold storage block begins to transfer to the cold face of the semiconductor refrigeration sheet 10 to achieve cooling. Under the Peltier effect of the semiconductor refrigeration sheet 10, the heat is transferred to the micro-channel radiator 11 through the hot face of the semiconductor refrigeration sheet 10, and the circulating cooling medium 19 in the micro-channel of the micro-channel radiator 11 carries away the heat and transfers it to the external environment.

[0034] The adapter plate 4 is a rigid-flexible combined plate composed of three FR4 plates and two flexible plates 20. The first FR4 plate 21 at both ends has a through hole and a connector 22 for electrically connecting and mechanically fixing the ceramic plate 3 and the rear-end electronics. The second FR4 plate 23 in the middle has a threaded hole, which is fixed to the fixing plate 8 of the "L" type plastic structure by the third screw 24, and the fixing plate 8 is fixed to the crystal fixing frame 5 by the fourth screw 25.

[0035] In order to avoid the low-temperature frost of the connector 22 between the ceramic plate 3 and the adapter plate 4, and the overflow of the silicon oil 13 between the SiPM sensor array 2 and the scintillation crystal 1, a large amount of electronic potting glue 15 is filled in the space between the ceramic plate 3, the SiPM fixing frame 6 and the cold storage block 9, and covers the connector between the ceramic plate 3 and the adapter plate 4; in order to avoid the overflow of the silicon oil 13 along the thread gap of the crystal fixing frame 5, the electronic potting glue 15 is filled on the upper side of the second screw 18 to achieve sealing.

[0036] The material of the metal shielding shell 12 is iron, which is used for electromagnetic shielding of the SiPM sensor array 2. The metal shielding shell 12 is spliced by multiple shell bodies and is fixed with the crystal fixing frame 5 and the SiPM fixing frame 6 through the fifth screw 26, and is fixed with the micro-channel heat sink 11 through the sixth screw 30. The crystal fixing frame 5 and the SiPM fixing frame 6 themselves have multiple hollow structures, and there are a large number of gap structures between the crystal fixing frame 5, the SiPM fixing frame 6, the metal shielding shell 12 and the micro-channel heat sink 11. A large amount of polyurethane foam 16 is filled in these hollow structures and gap structures, which can effectively reduce the heat loss of the SiPM sensor array 2 to the external environment, so as to control the SiPM sensor array 2 to reach the expected temperature.

[0037] Figure 3 The structure diagram of the scintillation crystal is shown. The scintillation crystal 1 is a cylindrical packaging structure composed of a stainless steel shell 27, a glass window 28 and a crystal 29. One side of the glass window 28 corresponds to the SiPM sensor array 2, and a gap of 0.1mm-0.2mm is formed between the SiPM sensor array 2 and the glass window 28, and the gap is filled with silicon oil 13.

[0038] Further, the SiPM sensor array 2 is a two-dimensional array detector composed of multiple SiPM sensors arranged closely. The sensor array is an n*n array.

[0039] Further, the ceramic substrate is alumina ceramic, aluminum nitride or silicon nitride ceramic with good thermal conductivity. The substrate is rectangular and its size is larger than that of the SiPM sensor array 2. There is no electronic device outside the initial connector of the ceramic plate, which can minimize the power consumption of the refrigeration sheet and ensure that the SiPM sensor array 2 reaches the target temperature.

[0040] Further, the crystal fixing frame 5 and the SiPM fixing frame 6 are made of heat-insulating plastic materials such as FR4 or nylon. The hollow structure is large enough to fill polyurethane foam 16 to reduce heat loss of SiPM. In addition, the threaded holes on the two structures must be embedded with internal thread to avoid slipping.

[0041] Further, the semiconductor refrigeration sheet 10 is a two-stage or three-stage semiconductor refrigeration sheet, which has a planar size close to or consistent with the SiPM sensor array 2 and the cold storage block 9, and can effectively control the thermal uniformity of the SiPM sensor array;

[0042] Further, the heat-conducting silica gel 14 is a solidified heat-conducting silica gel, which is in a paste state at the beginning of implementation, but is solidified into an elastic solid state structure after 24 or 48 hours;

[0043] Further, the connector between the ceramic plate 3 and the adapter plate 4 is sealed in the electronic potting glue 15, and low temperature cannot contact water vapor to cause frost. In addition, the second FR4 plate 23 in the adapter plate 4 is partially filled with electronic glue, and is fixed with the fixed plate 8. This structure can avoid the electronic potting glue 15 from being subjected to alternating loads during assembly, thereby causing the electronic potting glue 15 to fail.

[0044] Further, the entire packaging structure allows the small gap between the scintillation crystal 1 and the SiPM sensor array 2 to be filled with silicone oil, which improves the SiPM photon acceptance efficiency, and makes the packaging structure small and compact, thereby meeting the requirements of portable devices.

[0045] Currently, a plurality of tests have been carried out on the packaging structure. When the power of the semiconductor refrigeration sheet is 40W, the average temperature of the surface of the SiPM sensor array with an area of 50mm*50mm in the packaging structure is-24 degrees, and the surface temperature difference is less than 1℃, thereby effectively improving the energy resolution of the detector.

[0046] Although specific embodiments of the present application are disclosed for illustrative purposes, the purpose is to help understand the content of the present application and to implement it. Those skilled in the art can understand that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present application and the appended claims. Therefore, the present application should not be limited to the disclosed content of the best mode, and the scope of the present application is defined by the scope of the claims.

Claims

1. A front-end package structure for a low-temperature portable scintillator detector, characterized by, It includes a scintillation crystal (1), an adapter plate (4), a microchannel heat sink (11), and a partially enclosed metal shielding shell (12); the metal shielding shell (12) contains a SiPM sensor array (2), a ceramic plate (3), a crystal holder (5), a SiPM holder (6), a sealing ring (7), a fixing plate (8), a cold storage block (9), and a semiconductor cooling chip (10); the open end of the metal shielding shell (12) is connected to the microchannel heat sink (11) to form a closed structure; The scintillation crystal (1) is located inside a cavity composed of a crystal holder (5), a SiPM holder (6), a sealing ring (7), a SiPM sensor array (2), and a ceramic plate (3). Both the crystal holder (5) and the SiPM holder (6) are concave structures used to accommodate the scintillation crystal (1). The crystal holder (5) is fixed to the bottom of a metal shielding shell (12), and the SiPM holder (6) is fixed to the area near the opening of the metal shielding shell (12). The rear end of the SiPM sensor array (2) is fixed to the SiPM holder (6) via the ceramic plate (3). A gap exists between the front end of the SiPM sensor array (2) and the rear end of the scintillation crystal (1), and this gap is filled with silicone oil (13). The front end of the scintillation crystal (1) is fixed to the crystal holder (5). The opening end of the crystal holder (5) is sealed to the opening end of the SiPM holder (6). The gap between the scintillation crystal (1) and the crystal holder (5) is filled with silicone oil (13). The cold storage block (9) is located between the cold side of the semiconductor cooling chip (10) and the ceramic plate (3). The hot side of the semiconductor cooling chip (10) is a microchannel heat sink (11). Thermally conductive silicone (14) is filled between the cold storage block (9) and the ceramic plate (3), between the cold storage block (9) and the semiconductor cooling chip (10), and between the semiconductor cooling chip (10) and the microchannel heat sink (11). One end of the adapter plate (4) is electrically connected to the SiPM sensor array (2) via the ceramic plate (3), and the other end extends to the outside of the metal shielding shell (12); the space between the ceramic plate (3), the SiPM mounting bracket (6) and the cold storage block (9) is filled with electronic potting compound (15); The gaps between the crystal holder (5), the SiPM holder (6), the metal shielding shell (12), and the microchannel heat sink (11) are filled with polyurethane foam (16).

2. The front-end package structure of claim 1, wherein, The adapter plate (4) is a rigid-flexible combined plate composed of three FR4 plates and two flexible plates (20); wherein, the first FR4 plates (21) at both ends are connected to the second FR4 plate (23) in the middle through a flexible plate (20) respectively. The first FR4 plates (21) at both ends have through holes and connectors (22) for electrical connection, mechanical fixation of ceramic plate (3) and back-end electronics respectively. The second FR4 plate (23) in the middle is fixed to the fixing plate (8) by a third screw (24). The fixing plate (8) is fixed to the SiPM fixing bracket (6) by a fourth screw (25).

3. The front-end package structure of claim 1, wherein, The scintillation crystal (1) is a cylindrical encapsulation structure composed of a stainless steel shell (27), a glass window (28) and a crystal (29), wherein the crystal (29) is located in the stainless steel shell (27), and the opening of the stainless steel shell (27) is sealingly connected with the glass window (28); the glass window (28) is opposite to the SiPM sensor array (2).

4. The front-end package structure of claim 1 or 2 or 3, wherein, The material of the ceramic plate is alumina ceramic, aluminum nitride or silicon nitride ceramic.

5. The front-end package structure of claim 1 or 2 or 3, wherein, A sealing ring (7) is arranged between the open end of the crystal holder (5) and the open end of the SiPM holder (6), and the open end of the crystal holder (5) and the open end of the SiPM holder (6) are connected and fixed by the first screw (17) and compress the sealing ring (7) to form a seal.

6. The front-end package structure of claim 1 or 2 or 3, wherein, The rear end of the scintillation crystal (1) and the SiPM holder (6) both have a stepped structure for controlling the spacing between the SiPM sensor array (2) and the scintillation crystal (1).

7. The front-end package structure of claim 1 or 2 or 3, wherein, The scintillation crystal (1) is connected and fixed at the bottom end of the crystal holder (5) by the second screw (18) and the threaded hole of the crystal holder (5); the electronic potting adhesive (15) is filled between the second screw (18) and the threaded hole, which is used to prevent the silicon oil (13) from overflowing along the threaded gap of the crystal holder (5).

8. The front-end package structure of claim 1 or 2 or 3, wherein, The cold storage block (9) is a hollow structure, which is used to reduce the specific heat of the cold storage block while ensuring the heat transfer performance, and improve the cooling rate of the SiPM sensor array (2).

9. The front-end package structure of claim 1 or 2 or 3, wherein, The metal shielding shell (12) is made of iron, and is composed of multiple shell pieces; the metal shielding shell (12) is connected and fixed with the crystal holder (5) and the SiPM holder (6) by the fifth screw (26); and the metal shielding shell (12) is fixed with the micro-channel radiator (11) by the sixth screw (30).

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