A downhole muon imaging detector and detection method

Abstract

This invention relates to the field of muon detection, providing a downhole muon imaging detector and detection method, comprising: a stainless steel shell, a signal processing circuit board, an inner vertical structural module, and an outer horizontal structural module; the stainless steel shell, the inner vertical structural module, and the outer horizontal structural module are all cylindrical, the signal processing circuit board is disposed inside the inner vertical structural module, the stainless steel shell fits and encloses the outer horizontal structural module, and the outer horizontal structural module fits and encloses the inner vertical structural module. The detector of this invention can be placed in a confined space at the bottom of a borehole and can image a large area of ​​geological structure around the borehole. The detection method of this invention can effectively acquire incident and emitted signals through event discrimination, thereby constructing an accurate two-dimensional density image, simplifying the overall computational workload of detection, and improving the detection efficiency of muons.

Description

Technical Field

[0001] This invention relates to the field of muon detection, and more particularly to a downhole muon imaging detector and detection method. Background Technology

[0002] Cosmic rays m A radioactive particle is a natural source of radiation, produced by high-energy particles in the universe colliding with particles in the Earth's atmosphere when they reach the Earth. It has the characteristics of strong penetrating power and non-destructiveness. m As particles pass through different substances, they experience different energy decay rates; therefore, by measuring... m The attenuation of a particle along the path length through a material can be used to infer the average material density; this method is also known as... m Sub-imaging detection technology. Currently... m Muon imaging technology has applications in fields such as security inspection and internal imaging of nuclear materials. Compared with conventional detection technologies, such as ground-penetrating radar and seismic exploration, it has advantages such as higher resolution, no need for manual signal source establishment, and insensitivity to electromagnetic waves and mechanical noise. Therefore, applying muon imaging technology to geophysical exploration is a very promising path in the field of geophysical exploration.

[0003] Currently used in the field of geophysical exploration m There are three types of detectors: gas detectors, nuclear emulsion detectors, and plastic scintillator detectors. Compared to other detectors, plastic scintillator detectors have advantages such as simple structure, flexible shape, low power consumption, and real-time monitoring capabilities. The mainstream plastic scintillator detector structure is a flat panel detector. A flat panel plastic scintillator detector is a two-layered plane composed of horizontally and vertically arranged plastic scintillators. Its working process is as follows: first, the scintillators absorb... m The photon's energy is converted into photons. These photons are then collected and transmitted by wavelength-shifting optical fibers embedded within the scintillator. A photomultiplier tube at the end of the fiber converts the received photons into electrical signals, which are then analyzed. m Sub-signal obtained m Two-dimensional coordinate information of the incident particle. In the field of geophysical exploration... m Sub-imaging needs to obtain m Because they capture the trajectory information of incident particles, flat-panel detectors are generally not used alone. Depending on the application scenario and requirements, two to three independent flat-panel detectors are typically assembled into a multi-layer telescope detector. In 2010, the Earthquake Research Institute of the University of Tokyo used a detector with a double-layer telescope structure to measure the density structure of magma columns. The double-layer telescope detector is simple in structure, easy to carry, and can identify... mInformation on the incident angle of the particle; In 2012, the Italian Institute of Volcanology and Geology used a three-layer telescope-type detector to study the internal imaging of volcanoes. This detector has better anti-interference capabilities and better accuracy compared to a two-layer detector. m The ability to distinguish sub-events; subsequently, research teams from the University of Naples Federico II and the University of Catania also used three-layer telescope-type detectors to conduct research in the field of geophysical exploration. Although the technology of flat-panel detectors is relatively mature, this type of detector structure has the following three problems when applied to the field of geophysical exploration: First, in actual exploration of unknown underground areas, there is often no known underground space to place the flat-panel detector; second, flat-panel detectors generally have a large planar area, and even if there is known underground space, the detector cannot be used in a small space; finally, flat-panel detectors can only perform two-dimensional imaging of the planar area, so the range of underground space that can be detected is relatively small.

[0004] In the field of geophysical exploration m The traditional solution to the problems faced by sub-imaging technology in practical applications is to use multi-layer planar detectors. m While it can detect and image subsurface areas, this method has significant limitations when exploring underground regions. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides a downhole muon imaging detector, comprising: a stainless steel shell, a signal processing circuit board, an inner vertical structure module, and an outer horizontal structure module;

[0006] The stainless steel outer shell, the inner vertical structure module, and the outer horizontal structure module are all cylindrical. The signal processing circuit board is located inside the inner vertical structure module. The stainless steel outer shell fits and wraps the outer horizontal structure module, and the outer horizontal structure module fits and wraps the inner vertical structure module.

[0007] The detector's detection plane is set as the area of ​​the top surface of the stainless steel cylindrical casing, and the maximum detection angle of the detector's detection area is... f max The minimum detection angle in the detection area is 80°. f min The calculation formula is:

[0008]

[0009] Where R is the radius of the bottom circle of the detector, and H is the height of the detector.

[0010] Preferably, the inner vertical structure module is composed of multiple inner vertical scintillator components arranged vertically;

[0011] The inner longitudinal scintillator assembly includes: a plastic scintillator, a wavelength-shifting fiber, and two silicon photomultiplier tubes;

[0012] The plastic scintillator has a circular groove inside for embedding wavelength-shifting optical fibers;

[0013] A silicon photomultiplier tube is connected to both ends of the wavelength-shifted optical fiber.

[0014] Preferably, the outer lateral structure module is composed of multiple outer lateral scintillator components arranged horizontally;

[0015] The outer transverse scintillator assembly includes: a plastic scintillator, a wavelength-shifting fiber, and a silicon photomultiplier tube;

[0016] The plastic scintillator has a circular groove inside for embedding wavelength-shifting optical fibers;

[0017] One end of the wavelength-shifting fiber is connected to a silicon photomultiplier tube, and the other end is covered with black tape.

[0018] Preferably, the signal processing circuit board includes: an analog signal processing module, an FPGA module, and a data storage module;

[0019] The analog signal processing module includes: signal amplification and shaping circuitry and discrimination circuitry;

[0020] The signal amplification and shaping circuit is used to amplify and shape the initial signal acquired by the silicon photomultiplier tube, and the discrimination circuit is used to filter noise signals.

[0021] The FPGA module includes: a signal recording module and a muon event discrimination module;

[0022] The signal recording section is used to record the location and time of signal generation, while the muon event discrimination module is used to determine whether the signal is generated by a muon event based on the signal's characteristic information.

[0023] The data storage module is used to store μ event data.

[0024] A downhole muon imaging detection method includes:

[0025] S1: Place the downhole muon imaging detector at the bottom of the deep well to be explored, and acquire muons through the downhole muon imaging detector;

[0026] S2: Perform event discrimination on the acquired muons to obtain the incident and outgoing signals of the muon events;

[0027] S3: By imaging the incident and outgoing signals, a two-dimensional density image of the material inside the deep well to be detected is obtained.

[0028] Preferably, step S2 specifically includes:

[0029] S21: Set a fixed threshold based on the environment of the deep well to be explored and the test results, and eliminate dark noise in muons by threshold discrimination;

[0030] S22: Set the logical discrimination and time window discrimination, and output the incident signal and output signal of the muon event that both the logical discrimination and the time window discrimination pass.

[0031] Preferably, step S22 specifically includes:

[0032] S221: The muon obtains the outer transverse cylindrical signal after passing through the outer transverse structural module. L 1. The muon obtains the inner longitudinal cylindrical signal after passing through the inner longitudinal structure module. L 2. Through L 1 and L 2. Calculate and obtain the trajectory recording signal GT The calculation formula is:

[0033]

[0034] When the trajectory recording signal is 1, the logic judgment passes, and the μ-signal data of two consecutive time periods are recorded. N 1( t 1) and N 2( t 2), of which t 1 and t 2 represents two consecutive detection times;

[0035] S222: Set window time Δ T ,like If the time window is deemed passed, then this time... m The time record of the sub-event is t =( t 1+ t 2) / 2, let the incident signal and the emitted signal of this muon event be denoted as... N 1( t )and N 2( t ).

[0036] Preferably, step S3 specifically includes:

[0037] S31: Acquisition t Incident signal when a muon event occurs N 1( t ) and output signal N 2( t );

[0038] S32: Establish a planar coordinate system and calculate using the incident and outgoing signals. t The horizontal angle at which the muon passes through the detector at that moment i ( t );

[0039] S33: Establish a spatial coordinate system and calculate the elevation angle of the muon passing through the detector at time t. f ( t );

[0040] S34: Repeat steps S31-S33 to obtain the horizontal and vertical angles of the muon events at each time point;

[0041] S35: with it-f As coordinate axes and m The number of sub-events is used as density information, and each m Substitute the horizontal and vertical angles of the sub-events it-f The coordinate axes provide a two-dimensional density image of the material within the deep well to be probed.

[0042] Preferably, step S32 specifically includes:

[0043] S321: Establish a planar coordinate system with the center of the circle at the bottom of the detector as the origin. Draw a circle with the origin as the radius of the circle at the bottom of the detector. The incident signal... N 1( t As ON 1 vector, representing the emitted signal N 2( t As ON 2 vectors; ON 1 vector sum ON Both vectors originate from the origin and have a length equal to the radius of the circle.

[0044] S322: A 1( R , α 1( t ))and A 2( R , α 2( t )) are respectively ON 1 vector sum ON The components of the 2 vectors in the planar coordinate system, where, O The origin of the coordinate axis is... R Let be the radius of the circle at the bottom of the detector. α 1( t )for t Time vector ON 1 and x The included angle of the axis, α 2( t )for tTime vector ON 2 and x The included angle of the axis;

[0045] S323: Calculate the plane coordinates of the muon incident point ( x 1( t ), y 1( t The calculation formula is:

[0046]

[0047] The plane coordinates of the muon emission point were calculated. x 2( t ), y 2( t The calculation formula is:

[0048]

[0049] Calculate the horizontal angle i ( t The calculation formula is:

[0050] .

[0051] Preferably, step S33 specifically includes:

[0052] S331: Establish a spatial coordinate system with the center of the bottom of the detector as the origin, place the detector in the spatial coordinate system, and make the origin of the bottom surface of the detector coincide with the origin of the spatial coordinate system.

[0053] S332: The muon records the vertical coordinates of the incident point as it passes through the detector. z 1( t ) and the vertical coordinates of the launch point z 2( t ), calculate the planar distance of the muon passing through the detector. M A and vertical distance M B The calculation formula is:

[0054]

[0055] in,( x 1( t ), y 1( t ()) are the plane coordinates of the incident point of the muon, ( x 2( t ), y 2( t )) represents the planar coordinates of the muon emission point;

[0056] S333: Calculate the elevation angle f ( t The calculation formula is:

[0057] .

[0058] The present invention has the following beneficial effects:

[0059] 1. The detector of the present invention adopts a cylindrical design and integrates the signal processing circuit board, the inner longitudinal structure module and the outer transverse structure module in the cylinder. It takes advantage of the small horizontal space and large vertical space of the drilling itself, so that the detector can be placed in the narrow space at the bottom of the drilling and can image the geological structure of a large area around the drilling.

[0060] 2. The detection method of the present invention can effectively acquire incident and emitted signals through event discrimination, thereby constructing an accurate two-dimensional density image, simplifying the overall calculation of detection, and improving the detection efficiency of muons. Attached Figure Description

[0061] Figure 1 The overall structure of the downhole muon imaging detector;

[0062] Figure 2 This is a schematic diagram of the actual working environment of the detector;

[0063] Figure 3 This is a schematic diagram of the inner longitudinal scintillator assembly structure;

[0064] Figure 4 This is a schematic diagram of the outer transverse scintillator assembly structure;

[0065] Figure 5 This is a flowchart of the signal processing circuit board.

[0066] Figure 6 A schematic diagram of the horizontal coordinate system through which muons pass through the detector;

[0067] Figure 7 A schematic diagram of the spatial coordinate system for muons passing through the detector;

[0068] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0069] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0070] Reference Figure 1The present invention provides a downhole muon imaging detector, comprising: a stainless steel shell, a signal processing circuit board, an inner vertical structure module and an outer horizontal structure module;

[0071] The stainless steel outer shell, the inner vertical structure module, and the outer horizontal structure module are all cylindrical. The signal processing circuit board is located inside the inner vertical structure module. The stainless steel outer shell fits and wraps the outer horizontal structure module, and the outer horizontal structure module fits and wraps the inner vertical structure module.

[0072] Specifically, the detector is encased in a stainless steel shell, allowing it to operate normally in dark and humid underground environments. Furthermore, the stainless steel shell also shields it from the harsh natural environment. α Rays and parts β X-rays are used to prevent the energy carried by these rays from affecting the detector's results. The detector is internally divided into two parts: the detector unit and the signal processing unit. The detector unit consists of an inner vertical structure module and an outer horizontal structure module, while the signal processing unit is integrated onto a signal processing circuit board, which is fixed inside the detector. When m When a particle passes through a point on the detector unit, the detection section at that point receives a signal. This signal is then transmitted to the signal processing unit for processing, and finally, the result is obtained. m Two-dimensional incident coordinate information of the particle.

[0073] The detector's detection plane is set as the area of ​​the top surface of the stainless steel cylindrical casing, and the maximum detection angle of the detector's detection area is... f max The minimum detection angle in the detection area is 80°. f min The calculation formula is:

[0074] (1)

[0075] Where R is the radius of the bottom circle of the detector, and H is the height of the detector.

[0076] Specifically, such as Figure 2 The detector is placed at the bottom of the well to receive incoming muon rays and record the trajectory information of each muon. The detector adopts a cylindrical design, which takes advantage of the small horizontal space and large vertical space of the well itself. The detection plane of the detector is set as the side area of ​​the cylinder, so that the detector can achieve maximum detection efficiency in a confined space. Figure 2 The fan-shaped area inside the red dashed line is the detector's detection area, which has the maximum detection angle. f max and minimum detection angle f min According to the universe m According to the angular distribution statistics of the children, more than 99% m The zenith angle of the sub-satellite is less than 80°, therefore f max It can be considered to be 80°, and f min The size can be expressed by formula (1).

[0077] In this embodiment, the inner vertical structure module is composed of multiple inner vertical scintillator components arranged vertically.

[0078] The inner longitudinal scintillator assembly includes: a plastic scintillator, a wavelength-shifting fiber, and two silicon photomultiplier tubes;

[0079] The plastic scintillator has a circular groove inside for embedding wavelength-shifting optical fibers;

[0080] A silicon photomultiplier tube is connected to both ends of the wavelength-shifted optical fiber.

[0081] Specifically, such as Figure 3 The inner vertical structure module is used to detect the vertical position information of muons when they pass through the detector. When the plastic scintillator material comes into contact with the muon, it absorbs some energy and generates a large number of photons, thus realizing the function of converting the energy of the muon into photons. The wavelength-shifting fiber can absorb the photons in the plastic scintillator and transport the photons to both ends of the fiber, thus realizing the function of photon absorption and transport. The silicon photomultiplier tube can absorb photons and convert them into electrons, thus realizing the function of converting optical signals into electrical signals.

[0082] In this embodiment, the outer lateral structure module is composed of multiple outer lateral scintillator components arranged horizontally.

[0083] The outer transverse scintillator assembly includes: a plastic scintillator, a wavelength-shifting fiber, and a silicon photomultiplier tube;

[0084] The plastic scintillator has a circular groove inside for embedding wavelength-shifting optical fibers;

[0085] One end of the wavelength-shifting fiber is connected to a silicon photomultiplier tube, and the other end is covered with black tape.

[0086] Specifically, such as Figure 4The outer transverse structure module is used to detect the horizontal position of muons as they pass through the detector. The outer transverse scintillator assembly is ring-shaped and also consists of three parts: a plastic scintillator, a wavelength-shifting fiber, and a silicon photomultiplier tube. These three parts perform the same functions as the aforementioned components. The difference between the outer transverse scintillator assembly and the inner longitudinal scintillator assembly is that the silicon photomultiplier tube is only connected to one side of the wavelength-shifting fiber in the outer transverse scintillator assembly, while the other end is covered with black tape to prevent photons from escaping. This is because the outer transverse scintillator assembly is shorter, allowing photons to travel to the end of the fiber more quickly, thus reducing costs without affecting the final result.

[0087] Finally, all the aforementioned scintillator components are coated with a titanium dioxide (TiO2) film, which is used to reflect external photons and reduce the interference of external photons on the detection results.

[0088] In this embodiment, the signal processing circuit board includes: an analog signal processing module, an FPGA module, and a data storage module;

[0089] The analog signal processing module includes: signal amplification and shaping circuitry and discrimination circuitry;

[0090] The signal amplification and shaping circuit is used to amplify and shape the initial signal acquired by the silicon photomultiplier tube, and the discrimination circuit is used to filter noise signals.

[0091] The FPGA module includes: a signal recording module and a muon event discrimination module;

[0092] The signal recording section is used to record the location and time of signal generation, while the muon event discrimination module is used to determine whether the signal is generated by a muon event based on the signal's characteristic information.

[0093] The data storage module is used to store μ event data.

[0094] Specifically, the signal processing circuit board consists of three parts: an analog signal processing module, a digital programmable gate array (FPGA) module, and a data storage module, such as... Figure 5 As shown. The analog signal processing module includes a signal amplification and shaping circuit and a discrimination circuit. The signal amplification and shaping circuit amplifies and shapes the initial signal, while the discrimination circuit filters out noise signals caused by other reasons and converts the filtered analog signal into a digital pulse signal; the FPGA module includes a signal recording module and m The sub-event discrimination module, in which the signal recording module records the location and time of signal generation, and m The function of the sub-event discrimination module is to determine whether a signal is a [signal type] based on its characteristic information. m Signals generated by sub-events. Finally, all of them... m Sub-event data is recorded in the storage card of the data storage module. The data recorded on the storage card is transferred after the detection is complete. m Sub-event information is uploaded to the PC for image inversion.

[0095] This invention provides a downhole muon imaging detection method, comprising:

[0096] S1: Place the downhole muon imaging detector at the bottom of the deep well to be explored, and acquire muons through the downhole muon imaging detector;

[0097] S2: Perform event discrimination on the acquired muons to obtain the incident and outgoing signals of the muon events;

[0098] S3: By imaging the incident and outgoing signals, a two-dimensional density image of the material inside the deep well to be detected is obtained.

[0099] In this embodiment, the detector will face various noises when working downhole, such as dark noise, α ray, β ray, c Interference such as radiation can cause the scintillator to excite photons, thus affecting the detector's detection results. Although the stainless steel casing on the detector surface can eliminate these interferences... α Rays and parts β While rays can be shielded, a significant portion of them will still not be completely blocked, thus requiring the use of appropriate methods to... m The sub-events are judged, and the principle is as shown in step S2.

[0100] Step S2 is as follows:

[0101] S21: Set a fixed threshold based on the environment of the deep well to be probed and the test results, and eliminate dark noise in muons by threshold discrimination; low threshold level is mainly caused by dark noise, so a fixed threshold needs to be set according to the actual working environment and test results to eliminate the influence of dark noise.

[0102] S22: Set the logical discrimination and time window discrimination, and output the incident signal and output signal of the muon event that both the logical discrimination and the time window discrimination pass.

[0103] In this embodiment, step S22 specifically includes:

[0104] S221: m Sub-rays, some with higher energy β Rays and c Rays and other radiation can pass through the stainless steel casing and cause it to flicker and emit photons, thereby generating corresponding electrical signals. However, the vast majority of non-rays... m Sub-rays carry energy much smaller than mThe energy carried by the sub-rays often cannot pass through multiple scintillators simultaneously, therefore the method of identification is as follows:

[0105] The muon obtains the outer horizontal cylindrical signal after passing through the outer horizontal structural module. L 1. The muon obtains the inner longitudinal cylindrical signal after passing through the inner longitudinal structure module. L 2. Through L 1 and L 2. Calculate and obtain the trajectory recording signal GT The calculation formula is:

[0106] (2)

[0107] When the trajectory recording signal is 1, the logic judgment passes, and the μ-signal data of two consecutive time periods are recorded. N 1( t 1) and N 2( t 2), of which t 1 and t 2 represents two consecutive detection times;

[0108] S222: While the logical discrimination method can largely eliminate interference from other rays, individual rays can still penetrate multiple layers of scintillators, and multiple rays can cause coincidental triggering. Therefore, the time window discrimination method can further eliminate non-muon events, as follows:

[0109] Set window time Δ T If the following conditions are met:

[0110] (3)

[0111] If the time window is deemed passed, then this time... m The time record of the sub-event is t =( t 1+ t 2) / 2, let the incident signal and the emitted signal of this muon event be denoted as... N 1( t )and N 2( t ).

[0112] For drilling detectors of different sizes, the maximum time for a muon to pass through the entire detector is different, so the value of ΔT is determined based on the actual size of the detector.

[0113] In this embodiment, m There are two reasons for the density change of the particles as they travel from the atmosphere to the ground: (1) mThe particles undergo decay, a decay that is unavoidable in the natural environment. (2) m Energy is lost when particles collide with atoms of matter, but when m Sub-energy E μ At >10Gev, its energy loss is negligible. m A particle experiences different energy losses when passing through different substances, and the formula for energy loss is as follows:

[0114] (4)

[0115] in E for m The energy of the particle x yes m The position of the child along the path, r ( x () is the density passing through matter. a ( x , E )and b ( x , E These represent ionization and radiation energy losses, respectively. As can be seen from the formula, m The energy loss of a particle in matter depends on the density and path length of the matter, and is independent of the chemical composition of the matter. Therefore, once we know... m The subpath length and the average density along the path can be calculated using formula (4). m Minimum energy required for a particle to pass through the detector E c .

[0116] Finally, by observing the sky m Sub-energy distribution function from E c By integrating over an infinitely large range, we can obtain the detectable area. m Number of sub-events:

[0117] (5)

[0118] in I ( E , i It is related to the zenith angle. m Sub-energy distribution function. As can be seen from equations (4) and (5), m The number of sub-events on the same plane and m The magnitude of the average density of particles passing through the matter is negatively correlated, therefore we need to record the density of particles passing through the detector in each direction. mThe number of sub-events is used to obtain information on the density distribution of matter in the detection area.

[0119] In the m When recording the number of sub-events, it is inevitable that calculations are required. m The spatial angle information of the sub-subject passing through the detector, i.e., the horizontal angle. i and elevation angle f To address this, we designed an imaging method that is applicable to downhole drilling. m Sub-detectors, and can obtain each m in subevent m The spatial angle at which the particle passes through the detector is as shown in step S3.

[0120] Step S3 is as follows:

[0121] S31: Acquisition t Incident signal when a muon event occurs N 1( t ) and output signal N 2( t );

[0122] S32: Establish a planar coordinate system and calculate using the incident and outgoing signals. t The horizontal angle at which the muon passes through the detector at that moment i ( t );

[0123] S33: Establish a spatial coordinate system and calculate the elevation angle of the muon passing through the detector at time t. f ( t );

[0124] S34: Repeat steps S31-S33 to obtain the horizontal and vertical angles of the muon events at each time point;

[0125] S35: with it-f As coordinate axes and m The number of sub-events is used as density information, and each m Substitute the horizontal and vertical angles of the sub-events it-f The coordinate axes provide a two-dimensional density image of the material within the deep well to be probed.

[0126] In this embodiment, step S32 specifically includes:

[0127] S321: As Figure 6 As shown, a planar coordinate system is established with the center of the circle at the bottom of the detector as the origin. A circle is drawn with the origin, and the radius of the circle is the radius of the circle at the bottom of the detector. The incident signal is... N 1( t As ON 1 vector, representing the emitted signal N2( t As ON 2 vectors; ON 1 vector sum ON Both vectors originate from the origin and have a length equal to the radius of the circle. M A Let be the geometric length in the horizontal direction from the point of incidence to the point of exit. i ( t )for t time m The horizontal angle of incidence of the sub-subject;

[0128] S322: A 1( R , α 1( t ))and A 2( R , α 2( t )) are respectively ON 1 vector sum ON The components of the 2 vectors in the planar coordinate system, where, O The origin of the coordinate axis is... R Let be the radius of the circle at the bottom of the detector. α 1( t )for t Time vector ON 1 and x The included angle of the axis, α 2( t )for t Time vector ON 2 and x The included angle of the axis;

[0129] S323: Calculate the plane coordinates of the muon incident point ( x 1( t ), y 1( t The calculation formula is:

[0130] (6-1)

[0131] The plane coordinates of the muon emission point were calculated. x 2( t ), y 2( t The calculation formula is:

[0132] (6-2)

[0133] Calculate the horizontal angle i ( t The calculation formula is:

[0134] (7)

[0135] In this embodiment, step S33 specifically includes:

[0136] S331: As Figure 7 A spatial coordinate system is established with the center of the bottom of the detector as the origin. The detector is placed in the spatial coordinate system, and the origin of the bottom surface of the detector coincides with the origin of the spatial coordinate system.

[0137] S332: The muon records the vertical coordinates of the incident point as it passes through the detector. z 1( t ) and the vertical coordinates of the launch point z 2( t ), calculate the planar distance of the muon passing through the detector. M A and vertical distance M B The calculation formula is:

[0138] (8)

[0139] in,( x 1( t ), y 1( t ()) are the plane coordinates of the incident point of the muon, ( x 2( t ), y 2( t )) represents the planar coordinates of the muon emission point;

[0140] S333: Calculate the elevation angle f ( t The calculation formula is:

[0141] (9)

[0142] Through the derivation of the above formula, we can obtain each m The horizontal angle of the particle passing through the detector i ( t ) and elevation angle f ( t Finally, with it-f As coordinate axes and m The number of sub-events is used as density information, and each m By substituting the angular information of the sub-events, a two-dimensional density image is drawn, thereby reflecting the average density information of matter at each angle within the annular space of the detector's working area.

[0143] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0144] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments. Among the listed units of several devices, several of these devices may be specifically embodied by the same hardware item. The use of terms such as "first," "second," and "third," etc., does not indicate any order and can be interpreted as identifiers.

[0145] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A downhole muon imaging detector, characterized in that, include: Stainless steel casing, signal processing circuit board, inner vertical structure module and outer horizontal structure module; The stainless steel outer shell, the inner vertical structure module, and the outer horizontal structure module are all cylindrical. The signal processing circuit board is located inside the inner vertical structure module. The stainless steel outer shell fits and wraps the outer horizontal structure module, and the outer horizontal structure module fits and wraps the inner vertical structure module. The detector's detection plane is set as the area of ​​the top surface of the stainless steel cylindrical casing, and the maximum detection angle of the detector's detection area is... φ max The minimum detection angle in the detection area is 80°. φ min The calculation formula is: Where R is the radius of the bottom circle of the detector, and H is the height of the detector; The signal processing circuit board includes: an analog signal processing module, an FPGA module, and a data storage module; The FPGA module includes: a signal recording module and a muon event discrimination module; The muon event discrimination module is used to determine whether a signal is generated by a muon event based on its characteristic information; specifically: A fixed threshold is set based on the environment of the deep well to be explored and the test results, and dark noise in muons is eliminated by threshold discrimination; Set up logical discrimination and time window discrimination, and output the incident signal and output signal of the muon event that both logical discrimination and time window discrimination pass; After passing through the outer transverse structure module, the muon obtains the outer transverse cylindrical signal L1. After passing through the inner longitudinal structure module, the muon obtains the inner longitudinal cylindrical signal L2. The trajectory recording signal GT is calculated using L1 and L2, and the calculation formula is as follows: When the trajectory recording signal is 1, the judgment logic passes and records the μ signal data N1(t1) and N2(t2) for two consecutive time periods, where t1 and t2 are two consecutive detection time periods; Set the window time ΔT, if If the time window is deemed to have passed the test, the time of this muon event is recorded as t=(t1+t2) / 2, and the incident signal and the emitted signal of this muon event are recorded as N1(t) and N2(t) respectively.

2. The downhole muon imaging detector according to claim 1, characterized in that, The inner vertical structure module is composed of multiple inner vertical scintillator components arranged vertically. The inner longitudinal scintillator assembly includes: a plastic scintillator, a wavelength-shifting fiber, and two silicon photomultiplier tubes; The plastic scintillator has a circular groove inside for embedding wavelength-shifting optical fibers; A silicon photomultiplier tube is connected to both ends of the wavelength-shifted optical fiber.

3. The downhole muon imaging detector according to claim 1, characterized in that, The outer lateral structure module is composed of multiple outer lateral scintillator components arranged horizontally; The outer transverse scintillator assembly includes: a plastic scintillator, a wavelength-shifting fiber, and a silicon photomultiplier tube; The plastic scintillator has a circular groove inside for embedding wavelength-shifting optical fibers; One end of the wavelength-shifting fiber is connected to a silicon photomultiplier tube, and the other end is covered with black tape.

4. The downhole muon imaging detector according to claim 1, characterized in that, The analog signal processing module includes: signal amplification and shaping circuitry and discrimination circuitry; The signal amplification and shaping circuit is used to amplify and shape the initial signal acquired by the silicon photomultiplier tube, and the discrimination circuit is used to filter noise signals. The signal recording section is used to record the location and time of signal generation; The data storage module is used to store μ event data.

5. A downhole muon imaging detection method, characterized in that, include: S1: Place the downhole muon imaging detector at the bottom of the deep well to be explored, and acquire muons through the downhole muon imaging detector; S2: Perform event discrimination on the acquired muons to obtain the incident and outgoing signals of the muon events; S3: By imaging the incident and outgoing signals, a two-dimensional density image of the material inside the deep well to be detected is obtained; Step S2 is as follows: S21: Set a fixed threshold based on the environment of the deep well to be explored and the test results, and eliminate dark noise in muons by threshold discrimination; S22: Set the logic discrimination and time window discrimination, and output the incident signal and output signal of the μ event that both the logic discrimination and the time window discrimination pass; S221: After passing through the outer transverse structure module, the muon obtains the outer transverse cylindrical signal L1. After passing through the inner longitudinal structure module, the muon obtains the inner longitudinal cylindrical signal L2. The trajectory recording signal GT is calculated using L1 and L2. The calculation formula is as follows: When the trajectory recording signal is 1, the judgment logic passes and records the μ signal data N1(t1) and N2(t2) for two consecutive time periods, where t1 and t2 are two consecutive detection time periods; S222: Set the window time ΔT, if If the time window is deemed to have passed the test, the time of this muon event is recorded as t=(t1+t2) / 2, and the incident signal and the emitted signal of this muon event are recorded as N1(t) and N2(t) respectively.

6. The downhole muon imaging detection method according to claim 5, characterized in that, Step S3 is as follows: S31: Acquisition t Incident signal when a muon event occurs N 1( t ) and output signal N 2( t ); S32: Establish a planar coordinate system and calculate using the incident and outgoing signals. t The horizontal angle at which the muon passes through the detector at that moment θ ( t ); S33: Establish a spatial coordinate system and calculate the elevation angle of the muon passing through the detector at time t. φ ( t ); S34: Repeat steps S31-S33 to obtain the horizontal and vertical angles of the muon events at each time point; S35: with θ-φ As coordinate axes and μ The number of sub-events is used as density information, and each μ Substitute the horizontal and vertical angles of the sub-events θ-φ The coordinate axes provide a two-dimensional density image of the material within the deep well to be probed.

7. The downhole muon imaging detection method according to claim 6, characterized in that, Step S32 is as follows: S321: Establish a planar coordinate system with the center of the circle at the bottom of the detector as the origin. Draw a circle with the origin as the radius of the circle at the bottom of the detector. The incident signal... N 1( t As ON 1 vector, representing the emitted signal N 2( t As ON 2 vectors; ON 1 vector sum ON Both vectors originate from the origin and have a length equal to the radius of the circle. S322: A 1( R , α 1( t ))and A 2( R , α 2( t )) are respectively ON 1 vector sum ON The components of the 2 vectors in the planar coordinate system, where, O The origin of the coordinate axis is... R Let be the radius of the circle at the bottom of the detector. α 1( t )for t Time vector ON 1 and x The included angle of the axis, α 2( t )for t Time vector ON 2 and x The included angle of the axis; S323: Calculate the plane coordinates of the muon incident point ( x 1( t ), y 1( t The calculation formula is: The plane coordinates of the muon emission point were calculated. x 2( t ), y 2( t The calculation formula is: Calculate the horizontal angle θ ( t The calculation formula is: 。 8. The downhole muon imaging detection method according to claim 6, characterized in that, Step S33 is as follows: S331: Establish a spatial coordinate system with the center of the bottom of the detector as the origin, place the detector in the spatial coordinate system, and make the origin of the bottom surface of the detector coincide with the origin of the spatial coordinate system. S332: The muon records the vertical coordinates of the incident point as it passes through the detector. z 1( t ) and the vertical coordinates of the launch point z 2( t ), calculate the planar distance of the muon passing through the detector. M A and vertical distance M B The calculation formula is: in,( x 1( t ), y 1( t ()) are the plane coordinates of the incident point of the muon, ( x 2( t ), y 2( t )) represents the planar coordinates of the muon emission point; S333: Calculate the elevation angle φ ( t The calculation formula is: 。

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