A geophysical detection method and system based on muon momentum

Abstract

The present invention provides a geophysical detection method and system based on muon momentum, comprising: placing a detector A in an object-free area, placing an object to be detected and a detector B in an area to be detected; obtaining the muon multiple Coulomb scattering angle θ in the area to be detected recorded by the detector B; MS , obtain the muon multiple Coulomb scattering angle θ recorded by detector A in the object-free area MS0 ; through θ MS Calculate the muon momentum P in the area to be detected, and use θ MS0 Calculate the muon momentum P0 in the object-free area; calculate the muon energy value E in the area to be detected through P c , calculate the muon energy value E0 in the object-free region by P0; and calculate the muon energy value E0 in the object-free region by E c The actual energy loss value E is calculated by E0 t , through E t The material opacity δ of the object to be detected is calculated, and the material density ρ of the object to be detected is calculated from δ. The momentum detection method adopted by the present invention effectively avoids the influence of uncontrollable interference factors caused by changes in the natural environment, and improves the accuracy and stability of obtaining object density information.

Description

Technical Field

[0001] The present invention relates to the field of muon detection, and in particular to a geophysical detection method and system based on muon momentum. Background Art

[0002] Muons are highly penetrating particles. Due to this property, muon detection technology has been applied in many fields, with muon imaging being a key technology. Muon imaging technology can be divided into two categories: transmission imaging and scattering imaging. Transmission imaging determines information about the object being measured by detecting the distribution of the number of muons passing through a specified area, while scattering imaging determines information about the object being measured by calculating the distribution of deflection angles as muons pass through different materials. Muon radiographic imaging has been used in volcanology, mineral exploration, and various other industrial and security applications, so detectors used for imaging are also attracting considerable attention. Muon detectors are generally divided into plastic scintillator detectors, gas detectors, and nuclear latex detectors. Gas detectors need to maintain stable internal air pressure, and their long-term stability is relatively low. They also have complex structures and high costs, and their maintenance costs are high. Nuclear latex detectors have high resolution, and the detectors do not require readout circuits or power supply during the measurement process, so the detection system is simple. However, nuclear latex detectors cannot record time information. During the entire detection process, they only accumulate muon track information, making it impossible to perform dynamic observations. The subsequent readout system is technically complex and expensive, making it impossible to use them on a large scale in China. Plastic scintillator detectors are easy to machine, have flexible structural designs, and offer stable performance. They can adapt to different measurements and applications, and are relatively low in cost, making them suitable for large-scale use. Imaging with plastic scintillator detectors can obtain regional density (opacity) distribution maps, allowing for more direct access to object information in the area to be measured.

[0003] At present, the regional density imaging of plastic scintillator detectors is basically achieved by measuring the muon flux. Flux imaging principle: Since muons lose energy when passing through an object, only a certain number of muons can pass through a given object to be measured, and this number is related to the thickness and material of the object. The thickness is known, and the material density can be known from it. This method is simple to operate and does not require very high detector accuracy. The application of this method is relatively mature, but the muon flux imaging method has certain shortcomings. (1) The change in the detector's receiving angle for cosmic ray atmospheric showers at high altitudes causes the measured muon flux to increase significantly, affecting the measurement accuracy. Since muons are produced in atmospheric showers formed by the cascade interaction between primary cosmic rays and the atmosphere, their energy characteristics will be different at different altitudes on the earth. For example, if the observation point is moved from sea level to an altitude of 1000 meters, the observed muon flux will increase by 5 percentage points; (2) The earth's magnetic field will limit the energy threshold of muons. When low-energy primary cosmic rays propagate through the magnetosphere to the Earth's atmosphere, the primary particles allowed by the geomagnetic field reach the atmosphere and produce secondary muons and neutrinos, while the primary particles that are cut off do not produce secondary fluxes. The cutoff thresholds vary from region to region, resulting in large differences in the probability of muons of the same energy appearing in different regions. (3) In years of maximum solar activity, the muon flux reaches a minimum due to the modulation of the solar wind on charged particles, affecting the consistency of muon flux data when the measurement period is longer. Within the same solar activity cycle (about 11 years), the muon flux in the maximum activity year will be about 5% lower than in the minimum activity year. (4) Changes in the temperature of the upper atmosphere and changes in air density will cause changes in the interaction characteristics of cosmic rays, thereby causing instability in the muon flux observed on the Earth's surface. Due to these changes, different proportions of pions are captured by atomic nuclei, and therefore different numbers of pions decay into muons. Therefore, various factors, such as the measurement point's altitude, measurement time, and prevailing weather conditions, significantly influence the muon flux, leading to large errors in opacity calculations using the flux-energy model. Furthermore, when muons pass through thick regions, their energy loss is significant, significantly reducing the number of muons reaching the detector. Conventional flux methods address this issue by extending the detection period, but this approach increases the detector's dead time and can result in the omission of some muon information.

[0004] The above content is only used to assist in understanding the technical solution of the present invention and does not constitute an admission that the above content is prior art. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a geophysical detection method based on muon momentum, comprising:

[0006] S1: Set up a no-object area and a detection area, place detector A in the no-object area, and place the object to be detected and detector B in the detection area;

[0007] S2: Obtain the muon multi-Coulomb scattering angle θ of the detection area recorded by detector B MS , obtain the muon multiple Coulomb scattering angle θ recorded by detector A in the object-free area MS0 ;

[0008] S3: Through θ MS Calculate the muon momentum P in the area to be detected, and use θ MS0 Calculate and obtain the muon momentum P0 in the object-free zone;

[0009] S4: Obtain the muon energy value E of the area to be detected through P calculation c , obtain the muon energy value E0 in the object-free zone through P0 calculation;

[0010] S5: By E c The actual energy loss value E is calculated by E0 t , through E t The material opacity δ of the object to be detected is calculated, and the material density ρ of the object to be detected is calculated based on δ.

[0011] Preferably, step S3 is specifically as follows:

[0012] The calculation formula for the muon momentum P in the area to be detected is:

[0013]

[0014] Where β is the ratio of the muon velocity to the speed of light; p is the muon momentum in the detection area, in MeV / c; L is the length of the muon passing through the iron plate in the detector; X0 is the radiation length of the detector;

[0015] The calculation formula of the muon momentum P0 in the object-free region is:

[0016]

[0017] Where P0 is the muon momentum in the object-free region, with the unit of MeV / c.

[0018] Preferably, step S4 is specifically as follows:

[0019] The muon energy value E in the area to be detected is obtained by calculating the muon momentum p in the area to be detected c , the calculation formula is:

[0020]

[0021] The muon energy value E0 in the object-free zone is obtained by calculating the muon momentum P0 in the object-free zone. The calculation formula is:

[0022]

[0023] Among them, m μ is the rest mass of the muon, and c is the speed of light.

[0024] Preferably, step S5 is specifically as follows:

[0025] Actual energy loss value E t The calculation formula is: E t =E0-E C ;

[0026] The calculation formula for the material opacity δ of the object to be detected is:

[0027]

[0028] Among them, the a function represents the energy loss caused by ionization, and the b function represents the interaction between atomic nuclei and the production of positron-electron pairs;

[0029] The calculation formula for the material density ρ of the object to be detected is:

[0030]

[0031] Where L is the trajectory of the muon through the object to be detected, and η is the coordinate measured along the trajectory L of the muon through the rock volume.

[0032] A geophysical detection system based on muon momentum, comprising:

[0033] A construction module is used to construct a no-object area and a detection area, and detector A is placed in the no-object area, and the object to be detected and detector B are placed in the detection area;

[0034] Scattering angle detection module, used to obtain the muon multiple Coulomb scattering angle θ of the detection area recorded by detector B MS , obtain the muon multiple Coulomb scattering angle θ recorded by detector A in the object-free area MS0 ;

[0035] Muon momentum calculation module, used to calculate the momentum of the MS Calculate the muon momentum P in the area to be detected, and use θ MS0 Calculate and obtain the muon momentum P0 in the object-free zone;

[0036] Muon energy value calculation module, used to calculate the muon energy value E of the area to be detected through P calculation c , obtain the muon energy value E0 in the object-free zone through P0 calculation;

[0037] Material density calculation module for E c The actual energy loss value E is calculated by E0 t , through E t The material opacity δ of the object to be detected is calculated, and the material density ρ of the object to be detected is calculated based on δ.

[0038] The present invention has the following beneficial effects:

[0039] The present invention utilizes a momentum detection method and avoids interference from the natural environment by using two detectors for on-site measurement. Compared with the traditional flux method, the momentum detection method adopted effectively avoids the influence of uncontrollable interference factors caused by changes in the natural environment, improves the accuracy and stability of obtaining object density information, and optimizes detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a flow chart of a method according to an embodiment of the present invention;

[0041] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0042] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0043] The present invention addresses the problem of how to use muons to detect the density of an object. Based on the muon multiple Coulomb scattering formula, the muon momentum is synchronously measured using two plastic scintillator detectors with an iron plate in between, one on the surface and one underground. It is worth noting that the detectors need to be packaged in advance before the experiment; because the plastic scintillator records muons passively, the scintillator part of the detector needs to be encapsulated in a black box before arriving at the measurement site to prevent the detector from recording muons in advance.

[0044] Reference Figure 1 The present invention provides a geophysical detection method based on muon momentum, comprising:

[0045] S1: Set up a no-object area and a detection area, place detector A in the no-object area, and place the object to be detected and detector B in the detection area;

[0046] S2: Obtain the muon multi-Coulomb scattering angle θ of the detection area recorded by detector B MS , obtain the muon multiple Coulomb scattering angle θ recorded by detector A in the object-free area MS0 ;

[0047] S3: Through θ MS Calculate the muon momentum P in the area to be detected, and use θMS0 Calculate and obtain the muon momentum P0 in the object-free zone;

[0048] S4: Obtain the muon energy value E of the area to be detected through P calculation c , obtain the muon energy value E0 in the object-free zone through P0 calculation;

[0049] S5: By E c The actual energy loss value E is calculated by E0 t , through E t The material opacity δ of the object to be detected is calculated, and the material density ρ of the object to be detected is calculated based on δ.

[0050] In this embodiment, step S3 is specifically as follows:

[0051] When muons pass through the material to be tested, they collide with the atomic nuclei of the material and are scattered and deflected at small angles multiple times. When these muons pass through the material to be tested, some angles will be deflected, and the deflection angle is θ. At the same time, the position of the emission will shift by a certain distance. The deflection angle is related to the distance, density and momentum of the muon passing through the object. The multiple Coulomb scattering angle distribution of the muon is approximately Gaussian. The cumulative scattering angle θ is calculated from the muon emission and incident information recorded by the detector. The cumulative scattering angle θ approximately obeys a Gaussian distribution with a mean of zero, as shown in formula (1):

[0052]

[0053]

[0054] In formula (1), N is the number of particles; in formula (2), y d is its horizontal displacement relative to the initial trajectory, g1 and g2 are independent, and are unit Gaussian random numbers, θ MS is the muon multi-Coulomb scattering angle of the detection area (from formula 1); by setting the multi-scattering angle g2θ MS To determine the value of parameter g1, the muon multi-Coulomb scattering angle θ in the detection area is MS The muon momentum of the area to be detected can be obtained by using formula (1) and (2). Similarly, the muon momentum of the area without objects can be obtained by using formula (3-2).

[0055] The calculation formula for the muon momentum P in the area to be detected is:

[0056]

[0057] Where β is the ratio of the muon velocity to the speed of light; p is the muon momentum in the detection area, in MeV / c; L is the length of the muon passing through the iron plate in the detector; X0 is the radiation length of the detector;

[0058] The calculation formula of the muon momentum P0 in the object-free region is:

[0059]

[0060] Where P0 is the muon momentum in the object-free region, with the unit of MeV / c.

[0061] Specifically, X0 can be calculated by formula (4):

[0062]

[0063] Where Z is the number of protons in each nucleus, and A is the number of nucleons in each nucleus. For example, for an iron plate with L = 10 cm, X0 = 1.76 cm;

[0064] Since the multi-Coulomb scattering angle is affected by p, if one wants to effectively determine the type of material causing the scattering by determining X0, then it is necessary to measure not only the scattering angle and L, but also p. However, the present invention now replaces the position material portion in the detector with a known iron plate, so X0 is known, and L can be calculated from the recorded incident and exit points. Therefore, by recording the muon incident and exit points, an approximate θ can be obtained, and then the angular distribution width can be calculated, thereby obtaining the momentum of the muons passing through the detector.

[0065] In this embodiment, step S4 is specifically as follows:

[0066] The current energy value of the muon, E, can be calculated using the momentum-energy formula of the meson. c , the momentum-energy formula is derived as shown in equations (5) and (6):

[0067] T=EE μ (5)

[0068] E 2 =(pc) 2 +(mc 2 ) 2 (6)

[0069] Where T is the muon kinetic energy, E is the muon kinetic energy, and E μ for the muon static energy;

[0070] From formulas (5) and (6), we can derive formula (7-1) to obtain the muon momentum of the area to be detected, and formula (7-2) to obtain the muon momentum of the area without objects;

[0071] The muon energy value E in the area to be detected is obtained by calculating the muon momentum p in the area to be detected c , the calculation formula is:

[0072]

[0073] The muon energy value E0 in the object-free zone is obtained by calculating the muon momentum P0 in the object-free zone. The calculation formula is:

[0074]

[0075] Among them, m μ is the rest mass of the muon, which is equal to 0.10566 GeV·c -2 , c is the speed of light.

[0076] In this embodiment, step S5 is specifically as follows:

[0077] Identical muon detectors are placed in the object-free area and the area to be measured. It is important to note that the detectors used to measure geological materials and the detectors used to measure air muon momentum must be at the same angle. Because momentum measurement requires calculation of muon multi-Coulomb scattering angles, it is necessary to ensure that the muons detected by the two detectors are incident at the same angle before calculating energy loss. The momentum p0 and energy E0 of the muons in the air are measured using the same method, ultimately obtaining the actual energy loss value incident on the measured area.

[0078] Actual energy loss value E t The calculation formula is: E t =E0-E C ;

[0079] The calculation formula for the material opacity δ of the object to be detected is:

[0080]

[0081] Among them, the a function represents the energy loss caused by ionization, and the b function represents the interaction between atomic nuclei and the generation of positron-electron pairs. a and b are functions that depend on the properties of the material through which the meson propagates. Analysis shows that the mapping relationship between functions a and b and energy is only necessary when close to the horizontal direction and can be ignored when close to the vertical direction. Therefore, a = 2.0 MeV cm can be used in numerical calculations. 2 / g, b=3.5×10 -6 cm 2 / g;

[0082] The calculation formula for the material density ρ of the object to be detected is:

[0083]

[0084] The unit of opacity δ is g·cm -2 , that is, the density integral along the muon trajectory, L is the trajectory of the muon through the object to be detected, and η is the coordinate measured along the trajectory L of the muon through the rock volume.

[0085] Specifically, during the implementation process, two detectors record the muon's incident and exit angles. This information is used to calculate the muon momentum and energy loss. Finally, the energy loss is used to calculate the density of the target area and create a two-dimensional average density distribution map of the target area, thus achieving muon imaging based on muon momentum. Similarly, to obtain a three-dimensional average density distribution map, multiple detectors are placed in the target area to record muon information. Once the average density distribution map is obtained, further analysis of the density of the target area can be performed.

[0086] Method comparison:

[0087] Compared with the traditional detection method based on muon flux, the advantages of the method proposed in this patent are analyzed as follows. The traditional flux-energy formula is as follows:

[0088]

[0089] Where p is the muon momentum, θ is the zenith angle, H is the correlation function, C is a constant, and y = lg(p*cosθ).

[0090] Comparing equation (10) with the momentum-energy equations (7-1) and (7-2) proposed in this invention, it can be seen that the traditional flux equation not only still requires the momentum parameter, but also the zenith angle is substituted into the equation, adding another parameter. In addition to the high complexity of the flux model, the natural factors that interfere with the muon flux are also relatively complex, such as the relationship between the muon flux and altitude ( h0 is the empirical characteristic length, h0 = 4900 + 750p, h is the altitude of the observation point, and p represents the muon momentum. Moreover, h0 is expressed by different formulas in different models. It can be seen that when using the flux model for calculation, not only the interference factors must be considered, but also the parameter representation method must be taken into account. Moreover, environmental factors are uncontrollable, so the complexity of error analysis is relatively high. However, the present invention utilizes a momentum-based detection method to avoid interference from the natural environment because two detectors are used for on-site measurement. The interference factors mainly depend on the recognition efficiency of the detector and the error degree of the approximate calculation of the scattering angle. It can be seen that the biggest advantage of the momentum method over the flux method is that it avoids the influence of uncontrollable interference factors caused by changes in the natural environment, improves the accuracy and stability of the data, and optimizes the detection efficiency.

[0091] The present invention provides a geophysical detection system based on muon momentum, comprising:

[0092] A construction module is used to construct a no-object area and a detection area, and detector A is placed in the no-object area, and the object to be detected and detector B are placed in the detection area;

[0093] Scattering angle detection module, used to obtain the muon multiple Coulomb scattering angle θ of the detection area recorded by detector B MS , obtain the muon multiple Coulomb scattering angle θ recorded by detector A in the object-free area MS0 ;

[0094] Muon momentum calculation module, used to calculate the momentum of the MS Calculate the muon momentum P in the area to be detected, and use θ MS0 Calculate and obtain the muon momentum P0 in the object-free zone;

[0095] Muon energy value calculation module, used to calculate the muon energy value E of the area to be detected through P calculation c , obtain the muon energy value E0 in the object-free zone through P0 calculation;

[0096] Material density calculation module for E c The actual energy loss value E is calculated by E0 t , through E t The material opacity δ of the object to be detected is calculated, and the material density ρ of the object to be detected is calculated based on δ.

[0097] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or system. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or system comprising the element.

[0098] The serial numbers of the embodiments of the present invention are for descriptive purposes only and do not represent superiority or inferiority of the embodiments. In a unit claim that lists several means, several of these means may be embodied by the same item of hardware. The use of the terms first, second, and third, etc., does not denote any order and should be construed as identifiers.

[0099] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A geophysical detection method based on muon momentum, characterized in that: include: S1: Set up a no-object area and a detection area, place detector A in the no-object area, and place the object to be detected and detector B in the detection area; S2: Obtain the muon multi-Coulomb scattering angle θ of the detection area recorded by detector B MS , obtain the muon multiple Coulomb scattering angle θ recorded by detector A in the object-free area MS0 ; S3: Through θ MS Calculate the muon momentum P in the area to be detected, and use θ MS0 Calculate and obtain the muon momentum P0 in the object-free zone; S4: Obtain the muon energy value E of the area to be detected through P calculation c , obtain the muon energy value E0 in the object-free zone through P0 calculation; S5: By E c The actual energy loss value E is calculated by E0 t , through E t The material opacity δ of the object to be detected is calculated, and the material density ρ of the object to be detected is calculated based on δ.

2. The geophysical detection method based on muon momentum according to claim 1, characterized in that: Step S3 is specifically as follows: The calculation formula for the muon momentum P in the area to be detected is: Where β is the ratio of the muon velocity to the speed of light; p is the muon momentum in the detection area, in MeV / c; L is the length of the muon passing through the iron plate in the detector; X0 is the radiation length of the detector; The calculation formula of the muon momentum P0 in the object-free region is: Where P0 is the muon momentum in the object-free region, with the unit of MeV / c.

3. The geophysical detection method based on muon momentum according to claim 1, characterized in that: Step S4 is specifically as follows: The muon energy value E in the area to be detected is obtained by calculating the muon momentum p in the area to be detected c , the calculation formula is: The muon energy value E0 in the object-free zone is obtained by calculating the muon momentum P0 in the object-free zone. The calculation formula is: Among them, m μ is the rest mass of the muon, and c is the speed of light.

4. The geophysical detection method based on muon momentum according to claim 1, characterized in that: Step S5 is specifically as follows: Actual energy loss value E t The calculation formula is: E t =E0-E C ; The calculation formula for the material opacity δ of the object to be detected is: Among them, the a function represents the energy loss caused by ionization, and the b function represents the interaction between atomic nuclei and the production of positron-electron pairs; The calculation formula for the material density ρ of the object to be detected is: Where L is the trajectory of the muon through the object to be detected, and η is the coordinate measured along the trajectory L of the muon through the rock volume.

5. A geophysical detection system based on muon momentum, characterized in that: include: A construction module is used to construct a no-object area and a detection area, and detector A is placed in the no-object area, and the object to be detected and detector B are placed in the detection area; Scattering angle detection module, used to obtain the muon multiple Coulomb scattering angle θ of the detection area recorded by detector B MS , obtain the muon multiple Coulomb scattering angle θ recorded by detector A in the object-free area MS0 ; Muon momentum calculation module, used to calculate the momentum of the MS Calculate the muon momentum P in the area to be detected, and use θ MS0 Calculate and obtain the muon momentum P0 in the object-free zone; Muon energy value calculation module, used to calculate the muon energy value E of the area to be detected through P calculation c , obtain the muon energy value E0 in the object-free zone through P0 calculation; Material density calculation module for E c The actual energy loss value E is calculated by E0 t , through E t The material opacity δ of the object to be detected is calculated, and the material density ρ of the object to be detected is calculated based on δ.

Images