CN111999758A - MPPC-based small-sized beta detector for particulate matter monitoring - Google Patents

Abstract

The invention discloses a small β-scintillation detector for particle monitoring based on MPPC. The scintillator and the MPPC are coupled together by the optical glue used for the light guide; the side surface of the scintillator and the side surface of the light guide are both made with reflective layers; the circuit board is integrated with a temperature compensation type power supply circuit and a signal processing circuit; the casing includes an end cover, a main body, and a rear cover, and the front end of the end cover and the main body have the shielding window. The invention adopts a new type of semiconductor optoelectronic device MPPC, matches β-type scintillator and a power supply and signal processing circuit suitable for MPPC, so as to realize the counting and detection of β rays; , to achieve a large effective detection area, while ensuring low background and high detection efficiency, very suitable for atmospheric dust particle monitoring, paper thickness measurement and other fields.

Description

A small beta detector for particle monitoring based on MPPC

technical field.

The invention relates to the technical field of beta ray detection, in particular to a small beta scintillation detector for particle monitoring based on MPPC.

Background technique.

As the country's requirements for environmental governance are getting higher and higher, the concentration of dust/particulate matter (PM10 and PM2.5) in the air, as an integral part of environmental pollution, has become an important monitoring object of environmental protection departments at all levels. Air particulate matter monitor is an important instrument for monitoring the concentration of particulate matter in ambient air, including atmospheric automatic monitoring stations, dust monitoring in various places, air micro-stations, smart city monitoring stations, and household or portable personal particulate matter monitoring, etc. widely used.

At present, air particulate matter monitors are divided into four types according to the principle, namely the gravimetric method, the micro-oscillating balance method, the β-ray method and the light scattering method. Each method has its own advantages and disadvantages. Among them, the particle monitor using the β-ray method uses the principle that the β-ray penetrates through the substance and is absorbed and attenuated in intensity. The ambient air is sucked into the sampling tube by a sampling pump, and then discharged through the filter membrane, and the particulate matter in the air is trapped. Dust specks are formed on the filter membrane, and then the attenuation of beta rays passing through the dust specks of the filter membrane is measured to calculate the concentration of particulate matter. The β-ray method has a wide range of applications, accurate measurement and high sensitivity. It is one of the main methods for monitoring the concentration of air particles, and plays an increasingly important role in various aspects such as atmospheric monitoring and construction site dust monitoring.

In the particle monitor using the β-ray method, the detector part used to realize the β-ray measurement is one of the core components. The currently used β-detectors are mainly Geiger counters and photomultiplier tubes (Photomultiplier Tubes, referred to as PMT). Beta scintillation detector. Geiger counters are designed according to the ionization properties of rays to gases. The working voltage is about a few hundred volts, the service life is relatively short, the dead time is long, and the detection efficiency of high-energy beta rays is not high. Nowadays, it has been basically based on PMT. replaced by the beta scintillation detector. PMT-based β-scintillation detectors use scintillators to emit light when they receive ionizing radiation for detection. They have the advantages of long life, fast response, high detection efficiency, and good temperature characteristics. However, the PMT used generally needs to provide a high working voltage of thousands of volts. , easily affected by the magnetic field, large size, high power consumption, not conducive to the application of portable equipment; and the complex manufacturing process of PMT, it is difficult to reduce the cost, which is not conducive to the application of monitoring equipment that needs to be widely deployed.

Multi-Pixel Photon Counter (MPPC for short), or Silicon photomultiplier (SiPM for short), is a new type of photoelectric conversion device with low operating voltage, small size, high sensitivity, and anti-magnetic field interference. , strong mechanical shock resistance and low cost of mass production, not only help to reduce the size of the detector, improve the stability and safety of the detector, but also help to reduce costs, in high-energy physics experiments, cosmic ray observations, nuclear It has broad application prospects in medical imaging, nuclear safety and environmental monitoring.

In recent years, MPPC has attracted more and more attention in various fields of nuclear radiation measurement, and has begun to replace PMT in some of these applications, especially in the gamma detection of nuclear medicine imaging equipment, which has been maturely used in other applications such as environmental radiation. Safety, nuclear safety inspection and other fields have gradually begun to be studied and used, but the application of particle monitoring is still blank.

The detection limit, upper limit and detection limit of the β-ray air particulate matter monitor are related to the area of the filter dust spot. Correspondingly, the β detector is required to have a large enough effective detection area and a sufficiently high detection efficiency. The β-ray air particulate matter monitor usually uses a low-energy 14C radioactive source with a long half-life. The activity range is generally below the exempt value, with good stability, safety and durability, but also due to its relatively weak β-ray energy. , it is very easy to be blocked and absorbed, and the luminescence after interaction with the plastic scintillator is also very weak, and the β detector is also required to have high detection efficiency. In order to ensure high detection efficiency, on the one hand, the detector window should reduce the blocking of beta rays as much as possible under the premise of avoiding light. On the other hand, the luminescence of the plastic scintillator should be collected on the photosensitive surface without loss . The volume of MPPC is significantly smaller than that of PMT, but the photosensitive area is also relatively small, and the size of its photosensitive area is related to the cost of the device. On the premise of ensuring that the detector has a large effective detection area, it is necessary to use a relatively lower cost. The MPPC device with small effective photosensitive area is very important for the effective collection of scintillation light.

The particle monitoring application of the β-ray method is to detect the weak light generated by low-energy β-rays. The circuit design and threshold parameter setting of the corresponding detector should not only effectively remove noise, ensure a low background count rate, but also be able to detect the radiation. The signal is effectively detected to further ensure a high detection efficiency. In particular, atmospheric particle monitoring requires high measurement accuracy and can adapt to a certain range of ambient temperature changes. Therefore, the detector is required to have good temperature characteristics to keep the output stable even when the ambient temperature changes. In this way Only in this way can it be avoided that the monitoring instrument itself is required to perform very precise constant temperature control, which is relatively difficult and costly. Usually, the PMT itself has good temperature characteristics. The scintillation counting detector using the PMT can also make the PMT work in the plateau area through appropriate parameter settings according to the plateau characteristics of the PMT, so that the output scintillation counting signal is not easily affected by temperature changes. . The temperature coefficient of the MPPC device itself is obviously higher than that of the PMT, and the temperature characteristics are relatively poor, and it cannot work in the plateau region like the PMT. Therefore, it is relatively difficult to implement a β-ray counting detector with excellent performance based on MPPC. , It is necessary to design an adaptation circuit according to the characteristics of MPPC, through appropriate MPPC operating voltage settings, through appropriate MPPC signal extraction, amplification and screening, while ensuring effective detection of ray signals and removal of noise signals, it is possible to obtain low Background and high detection efficiency; accurate working voltage compensation according to MPPC temperature characteristics is also necessary to ensure that the detector has good temperature stability.

Invention content.

The technical problem to be solved by the present invention is: in view of the problems of the PMT-based beta scintillation detector with large volume, high power consumption, difficulty in controlling the cost, and inconvenience for use in portable devices, the present invention adopts a small size and low price scintillation detector. The new MPPC photoelectric sensor replaces the traditional PMT. A light guide is designed between the scintillator with a larger area and the MPPC with a smaller photosensitive area for optimal collection and conduction of the scintillation light, plus a temperature compensation type that can precisely adjust the temperature coefficient. The design of the power supply circuit and the adapted MPPC signal extraction, amplification and discrimination circuit, on the basis of ensuring excellent detection performance, realizes a small, low power consumption, and can significantly reduce the cost in batches, which can be applied to portable devices. .

In order to achieve the above object, the present invention adopts the following technical solutions: a small-scale beta scintillation detector for particle monitoring based on MPPC of the present invention includes a shielding window, a scintillator, a light guide, an MPPC, a circuit board, a casing, a cable, an upper circle plate, the first long plate, the second long plate, the lower circular plate, the end cover, the main body and the back cover; the shell includes an end cover, a main body and a back cover, the main body is cylindrical, the end cover It is connected with the main body by screws, and the back cover and the main body are connected and fixed by screws; the scintillator, light guide, MPPC, and circuit board are installed in the casing; the shielding window is arranged on the inner side of the end cover and the casing The front end of the main body; one end of the scintillator is connected with the shielding window, and the other end is coupled with the end face of the light guide; the other end face of the light guide is coupled with the MPPC; the circuit board includes an upper circular plate, a lower circular plate, a first long The strip and the second long strip, the upper circular plate, the lower circular plate, the first long strip and the second long strip are connected and fixed with each other by pins, and the upper circular plate and the lower circular plate are parallel to each other, The first elongated plate and the second elongated plate are parallel to each other to form a "II" shape; the MPPC is welded on the upper circular plate; the circuit board integrates the power circuit and signal adapted by the MPPC a processing circuit; the first strip board is a power supply circuit, which provides a working voltage for the MPPC; the second strip board is a signal processing circuit, which amplifies, discriminates and shapes the output signal of the MPPC; The lower circular plate has through holes and leads out cables for inputting low-voltage power supply and outputting standard TLL signals.

Preferably, the MPPC is a non-array type device with an effective photosensitive area smaller than the scintillator surface area.

Preferably, the scintillator is a plastic scintillator sheet.

Preferably, the material of the light guide is one of optical glass or optical organic glass.

Preferably, the light guide has a truncated cone structure, the surface of the larger end has the same shape and area as the surface of the scintillator, and the diameter of the end face with the smaller light guide area is the same as the side length of the effective area of the MPPC. The luminescence of the large area scintillator is collected and conducted to the smaller area MPPC detection window.

Preferably, the height of the light guide is greater than (S1-S2)/2 and less than (S1-S2), wherein S1 is the diameter or side length of the larger end face of the light guide, and S2 is the diameter or side of the smaller end face of the light guide. Long; the method of amplitude spectrum test plus count rate test is adopted, and the height that can achieve the best light collection and light transmission is preferably determined after the actual measurement and comparison of light guides of different heights.

Preferably, the larger end face of the light guide and the plastic scintillator sheet are coupled together by optical glue.

Preferably, the smaller end face of the light guide and the photosensitive face of the MPPC are coupled and fixed together by optical glue.

Preferably, after the scintillator is coupled with the light guide, a light reflective layer with full lateral coverage and high reflectivity is fabricated as a whole to reduce light loss as much as possible.

Preferably, the material, geometry and size of the light guide, the coupling between the scintillator and the light guide, and the high-reflectivity light reflective layer fully covered on the side, together ensure the light collection efficiency to the greatest extent. Thus, the detection efficiency of weak scintillation light generated by low-energy beta rays is ensured.

Preferably, the circuit board includes an upper circular board, a lower circular board, a first long strip board and a second long strip board, and pins are used to connect and fix each sub-board to each other, and the upper circular board and the lower circular board are The circular plates are parallel to each other, and the first elongated plate and the second elongated plate are parallel to each other, forming a "II" shape, which is designed according to the slender cylindrical shell structure.

Preferably, the circuit board integrates an MPPC-adapted power supply circuit and a signal processing circuit; the MPPC is welded on the upper circular plate; the first elongated board is a power supply circuit, which provides the MPPC with a working voltage The second elongated board is a signal processing circuit, and the output signal of the MPPC is amplified, discriminated and shaped, and the signal amplification circuit and the parameter setting of the discrimination threshold are set for the characteristics of the MPPC used, taking into account the balance of the The low background count rate and high detection efficiency also ensure the anti-interference performance of the detector; the lower circular plate leads out the cable/connector for inputting the low-voltage power supply and outputting the standard TLL signal.

Preferably, the power supply circuit is a temperature compensation type circuit, designed to be able to finely adjust the temperature coefficient and the output voltage, and to provide the MPPC with a suitable working voltage according to the ambient temperature, so that the output of the MPPC can be adjusted within a certain temperature variation range. The gain is stable and the output count rate of the detector is stable.

Preferably, the shell includes an end cover, a main body and a back cover, which are made of aluminum alloy material; the main body is cylindrical, the end cover and the middle cylinder are connected by threads, and the back cover and the middle cylinder are connected by thread. Fixed by screw connection.

Preferably, the shielding window is made of double-sided aluminized polyester film, and the double-sided aluminized polyester film shielding window has two layers, which are respectively arranged on the inner side of the end cover and the front end of the main body, and a sealant is used. By bonding and fixing, under the premise of reducing the blocking of beta rays as much as possible, the front end of the detector is protected from light and sealed at the same time.

Preferably, the scintillator, the light guide, the MPPC and the circuit board are housed in the housing.

Preferably, the front end surface of the scintillator is close to the shielding window at the front end of the main body, and the shielding window also plays the role of light reflection, and the photons emitted from the front end surface of the scintillator are reflected back and passed through the The light guide is collected to the MPPC, which reduces the light loss on the front face of the scintillator and further ensures the detection efficiency of the detector.

Preferably, black glue is used for fixing between the lower circular plate and the casing, and at the same time, the rear end of the detector is protected from light and sealed.

Preferably, there is electrical conduction between the ground of the circuit board and the casing, which further ensures the excellent anti-interference performance of the detector.

Preferably, in one of the embodiments, the MPPC is a device with an effective area of 3 mm×3 mm.

Preferably, in one embodiment, the MPPC is a device with an effective area of 4 mm×4 mm.

Preferably, in one embodiment, the MPPC is a device with an effective area of 6 mm×6 mm.

Preferably, in one of the embodiments, the reflective layer is made of Teflon wrapping and overlying aluminum foil.

Preferably, in one of the embodiments, the reflective layer is a titanium dioxide reflective coating.

Preferably, in one of the embodiments, the reflective layer is a nano-reflective coating.

The beneficial effects of the present invention are as follows: 1. A new type of semiconductor optoelectronic device MPPC is adopted to replace the traditional PMT, and the plastic scintillator is matched with the power supply and signal processing circuit adapted to the MPPC designed by the inventor, so as to realize a device suitable for particle monitoring. Low-energy beta-ray scintillation counting detector; 2. The optimal light guide shape and specification design have been verified by experiments, so that the detector can achieve a large effective detection area and high detection efficiency under the condition of using MPPC with a small effective photosensitive area, Conducive to low-cost control; 3. MPPC-adapted power supply and signal amplification, setting of screening parameters, while ensuring the detector's low background, high detection efficiency and good temperature characteristics, stable output count rate, not easily affected by temperature ;4. On the basis of achieving excellent detection performance, the detector has high integration, compact structure and small appearance, and can convert the detected beta rays into standard TTL signal output, with low power consumption, high safety, convenient use, and It is suitable for portable equipment; 5. The detector also has the advantages of good light protection, good sealing, not easily affected by magnetic fields, and strong anti-electromagnetic interference ability.

Description of drawings.

FIG. 1 is a schematic diagram of the working principle of the present invention.

FIG. 2 is a schematic structural diagram of the present invention.

Above: Shielding window 1, scintillator 2, light guide 3, MPPC4, circuit board 5, housing 6, cable 7, upper circular plate 51, first long strip 52, second long strip 53, lower circular plate 54 , end cover 61 , main body 62 , rear cover 63 .

Detailed ways.

The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the examples are not intended to limit the present invention.

Referring to Figure 1, the working principle of a small beta scintillation detector for particle monitoring in this embodiment is shown. The adaptation circuit can obtain low background and high detection efficiency only by setting the appropriate MPPC working voltage, through the appropriate MPPC signal extraction, amplification and screening, and at the same time ensuring the effective detection of the ray signal and the removal of the noise signal; It is also necessary to perform accurate working voltage compensation according to the temperature characteristics of MPPC to ensure that the detector has good temperature stability. The back end is drawn from the circuit board for low-voltage power input and TTL signal output.

Referring to FIG. 1 and FIG. 2 , the small beta scintillation detector for particle monitoring in this embodiment includes: a shielding window 1 , a scintillator 2 , a light guide 3 , an MPPC 4 , a circuit board 5 , a casing 6 and a cable 7 . The MPPC4 is welded on the circuit board 5, the scintillator 2 and the MPPC4 are respectively coupled to the two end faces of the light guide 3, the scintillator 2, the light guide 3, the MPPC4 and the circuit board 5 are installed in the casing 6, and the front end of the casing 6 is fixed with a shielding window 1, The rear end is led out by a cable 7 from the circuit board, which is used for low-voltage power input and TTL signal output.

In this embodiment, the scintillator 2 is a plastic scintillator sheet with a specification of φ14mm×0.5mm, which can achieve an effective detection area of φ12mm, and the thickness of 0.5mm can sufficiently block the lower energy beta rays of the detected 14C radiation source function to ensure the detection efficiency.

In this embodiment, MPPC4 is a non-array type product developed by Hamamatsu Photonics Co., Ltd. of Japan, and the effective photosensitive area is 3mm*3mm.

In this embodiment, the light guide 3 is made of optical plexiglass material and has a circular truncated structure; the diameter of the end face of the light guide 3 with a larger area is the same as the diameter of the surface of the scintillator 2, and optical silica gel is used to couple with the scintillator 2; The diameter of the end face is the same as the side length of the effective area of MPPC4. Optical silica gel is used to couple with the photosensitive surface of MPPC4. Light reflection; the height of the light guide 3 is between 5.5mm and 11mm, and the height of the optimal light collection and light transmission can be achieved through experimental comparison; such a geometric structure makes most of the light reaching the side can be reflected by Faster is collected on the photosensitive surface of MPPC4, reducing light loss as much as possible. In this way, a larger detection area and high detection efficiency can be achieved under the condition of using the MPPC4 with relatively low cost and small effective photosensitive area.

In this embodiment, the light reflective layer adopts a nano-reflective coating with a certain thickness and a reflectivity of 95% and above, so as to reduce the loss of light transmission on the sides of the scintillator 2 and the light guide 3 .

In this embodiment, the coupling between the light guide 3 and the MPPC 4 is reinforced with a fixing glue to prevent decoupling due to force.

In this embodiment, the circuit board 5 includes an upper circular plate 51, a first elongated plate 52, a second elongated plate 53 and a lower circular plate 54. The sub-boards are connected and fixed with each other by pins, wherein the upper circular plate is It is parallel to the lower circular plate, the first long strip and the second long strip are parallel to each other, forming a "II" shape, which is suitable for being installed in a slender cylindrical shell structure and fixed, and also suitable for circuit division according to different functions. . MPPC4 is welded on the upper circular plate 51; the first long plate 52 is provided with a power supply circuit with temperature compensation function, and its temperature coefficient and output voltage are designed to be finely adjusted, so that the real-time temperature sensor near MPPC4 can The feedback temperature and the temperature coefficient of MPPC4 provide a suitable working voltage for MPPC4, which ensures that the output gain of MPPC4 remains stable within the temperature range of -10°C to +45°C, thereby keeping the output count rate of the detector stable; The second strip 53 is a signal processing circuit, which draws out a pulse signal according to the characteristics of the MPPC used, and then amplifies, discriminates, and shapes it into a standard TTL level signal. The parameter settings of the amplification and discrimination circuit are preferably set by actual measurement. , so that the detector has a balance between low background count rate and high detector efficiency; the lower circular plate 54 is an input and output circuit board, and the cable 7 is drawn out of the casing 6 to provide low-voltage power input for the circuit board 5 And output TTL signal.

In this embodiment, the housing 6 is composed of an end cover 61 , a main body 62 and a rear cover 63 , the whole is cylindrical, and the materials are all aluminum alloys. The front ends of the end cover 61 and the main body 62 are respectively fixed with a layer of shielding window 1 with sealant; the shielding window 1 is a double-sided aluminized polyester film. Affect the passage of low-energy beta rays; the end cover 61 and the main body 62 are fixed by screw connection and have good electrical conduction, and the rear cover 63 and the main body 62 are fixed by screw connection and have good electrical conduction; there are through holes on the back cover 63 for Cable 7 goes out.

In this embodiment, the scintillator 2, the light guide 3, the MPPC 4 and the circuit board 5 are installed in the casing 6; the front end surface of the scintillator 2 is close to the aluminum foil film shielding window 1 at the front end of the main body, and this structure makes the shielding window 1 meet the requirements of avoiding light At the same time, it also plays the role of light reflection, reducing the loss of scintillation light from the front end of the scintillator 2, thereby providing a further guarantee for the detector to obtain high detection efficiency; black glue is used between the lower circular plate 54 and the main body 62. It is fixed, and at the same time, the rear end of the detector is protected from light and sealed, so that when the detector is used in the particle monitor equipment, it is not necessary to put too high requirements on the light protection of the equipment, and it is also possible to avoid the leakage of air in the gas path as much as possible. resulting in measurement accuracy problems.

In this embodiment, the ground of the circuit board 5 is connected to the rear cover 63 through the ground wire drawn from the lower circular plate 54 to achieve electrical connection, form a good shield, and further ensure the excellent anti-interference ability of the detector.

To sum up, the small beta scintillation detector in this scheme adopts a new type of semiconductor photoelectric sensor MPPC4, a circular truncated light guide 3, a matching sheet-shaped plastic scintillator 2, and the power supply and signal processing circuit design and circuit suitable for MPPC. Parameter setting, reasonable and compact structure and housing design, in the case of using MPPC4 with a small effective photosensitive area and relatively low cost, a large effective detection area and high detection efficiency are realized, and the detected β rays are converted into Standard TTL signal, with compact shape (φ20mm*75mm), low power consumption (0.2W), very easy to use and suitable for portable equipment, also has good temperature characteristics, good light protection, good sealing, not easy to use Affected by magnetic fields, it has the characteristics of strong anti-electromagnetic interference ability, which is very suitable for the monitoring of atmospheric dust particles, dust monitoring in various occasions, paper thickness measurement and other fields.

The above description is only a preferred embodiment for fully illustrating the present invention, and the features in the description are still satisfied or partially satisfied in other embodiments; any partial modification or equivalent replacement made under the spirit and principle of the present invention , all will be regarded as being within the protection scope of the present invention.

Claims (22)

1. A small beta scintillation detector for monitoring particulate matters based on MPPC (maximum power point tracking), comprises a shielding window, a scintillator, a light guide, MPPC (maximum power point tracking), a circuit board, a shell, a cable, an upper circular plate, a first long strip plate, a second long strip plate, a lower circular plate, an end cover, a main body and a rear cover; the shell is characterized by comprising an end cover, a main body and a rear cover, wherein the main body is cylindrical, the end cover and the main body are connected through threads, and the rear cover and the main body are fixedly connected through screws; the scintillator, the light guide, the MPPC and the circuit board are arranged in the shell; the shielding window is arranged on the inner side of the end cover and the front end of the shell main body; one end of the scintillator is connected with the shielding window, and the other end of the scintillator is coupled with the end face of the light guide; the other end face of the light guide is coupled with the MPPC; the circuit board comprises an upper circular plate, a lower circular plate, a first long strip plate and a second long strip plate, wherein the upper circular plate, the lower circular plate, the first long strip plate and the second long strip plate are mutually connected and fixed by pins, the upper circular plate and the lower circular plate are mutually parallel, and the first long strip plate and the second long strip plate are mutually parallel to form a 'II' shape; the MPPC is welded on the upper circular plate; the circuit board integrates a power supply circuit and a signal processing circuit which are adaptive to MPPC; the first strip plate is a power circuit and provides working voltage for the MPPC; the second strip plate is a signal processing circuit and is used for amplifying, screening and shaping the output signal of the MPPC; the lower circular plate is provided with a through hole, a cable is led out, and the lower circular plate is used for inputting a low-voltage power supply and outputting a standard TLL signal.

2. The MPPC-based compact beta scintillation detector of claim 1, wherein said MPPC is a non-array type device having an effective photosensitive area that is small compared to a scintillator surface area.

3. The MPPC-based compact beta scintillation detector of claim 1, wherein said scintillator is a thin sheet of plastic scintillator.

4. The MPPC-based compact beta scintillation detector of claim 1, wherein the material of said light guide is one of optical glass or optical plexiglass.

5. The MPPC-based small-sized beta scintillation detector for particulate matter monitoring as claimed in claim 1, wherein the light guide is of a frustum structure, the surface of the larger end has the same shape and area as the surface of the scintillator, and the diameter of the end surface of the light guide with the smaller area has the same side length as the effective area of the MPPC, and is used for collecting and transmitting the luminescence of the scintillator with the larger area to the MPPC detection window with the smaller area.

6. The MPPC-based compact beta scintillation detector of claim 1, wherein the light guide has a height between greater than (S1-S2)/2 and less than (S1-S2), where S1 is the diameter or side length of the larger end face of the light guide, and S2 is the diameter or side length of the smaller end face of the light guide; the method of amplitude spectrum test and count rate test is adopted, and the optimal light collection and light transmission height can be preferably determined after actual measurement and comparison are carried out on the light guides with different heights.

7. The MPPC-based compact beta scintillation detector of claim 1, wherein a larger end face of said light guide is optically coupled to said plastic scintillator sheet.

8. The MPPC-based compact beta scintillation detector of claim 1, wherein the smaller end surface of said light guide is optically coupled to and secured to the photosensitive surface of said MPPC.

9. The MPPC-based compact beta scintillation detector of claim 1, wherein said scintillator is coupled to said light guide and is integrally formed with a laterally fully covered light reflective layer having a high reflectivity to minimize light loss.

10. The MPPC-based compact beta scintillation detector of claim 1, wherein the light guide is made of a material, has a geometry, and has a size, and the coupling and side-fully-coated high-reflectivity light reflecting layer of the scintillator and the light guide jointly maximize the light collection efficiency, thereby ensuring the detection efficiency of weak scintillation light generated by low-energy beta rays.

11. The MPPC-based compact beta scintillation detector of claim 1, wherein said power supply circuit is a temperature compensation type circuit designed to fine tune temperature coefficient and output voltage, and to provide suitable operating voltage for said MPPC based on ambient temperature, and to stabilize MPPC output gain and detector output count rate within a certain temperature variation range.

12. The MPPC-based compact beta scintillation detector of claim 1, wherein said shell is made of an aluminum alloy material.

13. The MPPC-based small-sized beta scintillation detector for particulate matter monitoring as claimed in claim 1, wherein the shielding window is a double-sided aluminum plated polyester film, the double-sided aluminum plated polyester film shielding window has two layers, the two layers are respectively arranged at the inner side of the end cover and the front end of the main body, and are bonded and fixed by a sealant, so that the front end of the detector is protected from light and sealed on the premise of reducing the blocking of beta rays as much as possible.

14. The MPPC-based compact beta scintillation detector of claim 1, wherein the front surface of said scintillator is proximate to said shielding window of said front body, said shielding window simultaneously functioning as a light reflector to reflect photons exiting from said front surface of said scintillator back to said MPPC via said light guide, thereby reducing light loss from said front surface of said scintillator and further ensuring the detection efficiency of the detector.

15. The MPPC-based small-sized beta scintillation detector for particulate matter monitoring as claimed in claim 1, wherein the lower circular plate and the shell are fixed by black glue, and light shielding and sealing at the rear end of the detector are realized at the same time.

16. The MPPC-based small-sized beta scintillation detector for particulate matter monitoring as claimed in claim 1, wherein the ground of the circuit board is electrically connected with the shell, further ensuring excellent anti-interference performance of the detector.

17. The MPPC-based compact beta scintillation detector of claim 1, wherein in one embodiment said MPPC is a 3mm x 3mm active area device.

18. The MPPC-based compact beta scintillation detector of claim 1, wherein in one embodiment said MPPC is a 4mm x 4mm active area device.

19. The MPPC-based compact beta scintillation detector of claim 1, wherein in one embodiment said MPPC is a 6mm x 6mm active area device.

20. The MPPC-based compact beta scintillation detector of claim 1, wherein in one embodiment said reflective layer is teflon wrapped with aluminum foil.

21. The MPPC-based compact beta scintillation detector of claim 1, wherein in one embodiment said reflective layer is a titanium dioxide reflective coating.

22. The MPPC-based compact beta scintillation detector of claim 1, wherein in one embodiment said reflective layer is a nano-reflective coating.

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