Cosmic ray based small celestial body density detection device and detection method

Abstract

The application discloses a small celestial body density detection device and method based on cosmic rays. The small celestial body density detection device comprises a time flyer, the time flyer comprises a first time flyer and a second time flyer arranged along a first direction, and a mounting cavity is arranged between the time flyer and the second time flyer; a lead absorbing body is arranged for absorbing part of background particles; a radiation body is arranged for absorbing muons and radiating Cherenkov photons; a detection layer comprises a first detection layer and a second detection layer, and the first detection layer and the second detection layer are respectively arranged at two opposite side ends of the radiation body along the first direction; the Cherenkov photons projected on the detection layer form a Cherenkov light ring, and the detection layer is used for converting optical signals into electrical signals; and a collection and processing module is arranged for collecting the number of electrical signals and inverting the attenuation flux of muons.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of celestial body density measurement, in particular to a small celestial body density detection device based on cosmic rays and a detection method. BACKGROUND

[0002] Determining the volume, physical properties and internal structure of asteroids is crucial for understanding their origin and for developing planetary defense strategies and in-situ resource surveying, while currently the internal structure of asteroids has to be inferred from surface morphology (observed through photographic images or radar) and indirectly from other observations (measuring their self-transmission period and size). For example, radar measurements can provide information on the density structure of asteroids at a depth of about one meter in the weathering layer; the structure of the asteroid rubble pile is inferred from its appearance (the presence of boulders and blocks) and bulk density.

[0003] In the prior art, the density of the internal structure of asteroids cannot be accurately measured. SUMMARY

[0004] In view of the above defects or deficiencies in the prior art, it is desirable to provide a small celestial body density detection device based on cosmic rays.

[0005] In a first aspect, a small celestial body density detection device based on cosmic rays comprises:

[0006] A time-of-flight device, the time-of-flight device comprising a first time-of-flight device and a second time-of-flight device arranged along a first direction, the first time-of-flight device being configured to record first position information L1 and first incidence time T1 of a muon, the second time-of-flight device being configured to record second position information L2 and second incidence time information T2 of the muon; and a mounting cavity being provided between the first time-of-flight device and the second time-of-flight device;

[0007] A lead absorption body located in the mounting cavity, the lead absorption body being configured to absorb part of background particles;

[0008] A radiation body located in the mounting cavity, the radiation body being configured to absorb the muon and radiate Cerenkov photons;

[0009] A detection layer located in the mounting cavity, the detection layer comprising a first detection layer and a second detection layer, and the first detection layer and the second detection layer being located at two opposite side ends of the radiation body along the first direction respectively, the Cerenkov photons projected on the detection layer forming a Cerenkov ring, and the detection layer being configured to convert optical signals into electrical signals;

[0010] A collection and processing module electrically connected to the detection layer, configured to collect the number of electrical signals and to inverse the attenuation flux of the muon.

[0011] According to the technical scheme provided in the embodiment of the present application, each group of detection layers comprises a plurality of parallel arranged photomultiplier tubes.

[0012] According to the technical scheme provided in the embodiment of the present application, the time flyer is composed of a plurality of groups of parallel arranged silicon microstrips or plastic scintillators.

[0013] According to the technical scheme provided in the embodiment of the present application, the radiation body is composed of gas Ar / CH4 or silicon aerogel.

[0014] In a second aspect, a detection method of a cosmic-ray-based small celestial body density detection device comprises the following steps:

[0015] S1, obtaining initial muon flux of a surface of a measured celestial body;

[0016] S2, discriminating muons from background particles and screening out muons passing through the interior of the celestial body;

[0017] S3, obtaining first position information L1 of a plurality of muons collected by a first time flyer and second position information L2 of a plurality of muons collected by a second time flyer within a preset time;

[0018] S4, selecting the first position information L1 and the second position information L2 of one group of muons, judging an incident direction, and reconstructing angle information of the group of muons;

[0019] S5, counting the number of electrical signals under the angle information, and inverting the attenuation flux of the muon under the angle information;

[0020] S6, obtaining the density length of the celestial body under the angle information according to the ratio of the initial flux to the attenuation flux;

[0021] S7, repeating steps S4-S6 to inversely image the density length of the celestial body at multiple angles to obtain a density distribution map of the interior of the celestial body.

[0022] According to the technical scheme provided in the embodiment of the present application, the initial flux of the muon of the surface of the measured celestial body is obtained, and the calculation formula is as follows:

[0023]

[0024] 9. According to the technical scheme provided in the embodiment of the present application, the step of discriminating muons from background particles comprises the following steps:

[0025] S2-1, absorbing part of the background particles by absorbing lead;

[0026] S2-2, discriminating muons from the remaining background particles by Cherenkov ring information.

[0027] According to the technical scheme provided in the embodiment of the application, the judging the incident direction comprises the following steps:

[0028] When the first incident time T1 is less than the second incident time T2, it is judged that the muon incident direction is that the first time flyer points to the direction of the second flyer;

[0029] When the first incident time T1 is greater than the second incident time T2, it is judged that the muon incident direction is that the second time flyer points to the direction of the first flyer.

[0030] The application has the beneficial effects that the application discloses a small celestial body density detection device and detection method based on cosmic rays, the detection device comprises a time flyer, the time flyer comprises a first time flyer and a second time flyer arranged along a first direction, the first time flyer is used for recording first position information L1 and first incident time T1 of a muon passing through, and the second time flyer is used for recording second position information L2 and second incident time information T2 of the muon passing through; and a mounting cavity is arranged between the first time flyer and the second time flyer; a lead absorbing body is located in the mounting cavity, and the lead absorbing body is used for absorbing part of background particles; a radiation body is located in the mounting cavity, and the radiation body is used for absorbing muons and radiating out Cerenkov photons; a detection layer is located in the mounting cavity, the detection layer comprises a first detection layer and a second detection layer, and the first detection layer and the second detection layer are respectively located at two opposite side ends of the radiation body along the first direction, the Cerenkov photons projected on the detection layer form a Cerenkov light ring, and the detection layer is used for converting optical signals into electrical signals; and a collection and processing module is electrically connected with the detection layer and is used for collecting the number of electrical signals and inverting the attenuation flux of the muons.

[0031] The initial flux of the muons on the surface of the measured celestial body is obtained through calculation, the background particles are preliminarily screened out by the lead absorbing body, the particles enter the first time flyer, the lead absorbing body, the first detection layer, the radiation body and the second detection layer in turn and are finally emitted from the second time flyer, the radiation body absorbs the muons and radiates out Cerenkov photons outward after the muons enter the radiation body, the Cerenkov photons form a Cerenkov radiation light ring on the detection layer, the background particles are further screened out according to the Cerenkov radiation light ring, the angle information of the group of muons is reconstructed through the first incident first position information L1, the first incident time T1, the second position information L2 and the second incident time information T2, the attenuation flux of the muons under the angle information is inverted by the collection and processing module through the collection of the number of electrical signals, and the ratio of the initial flux to the attenuation flux is the attenuation flux of the muons under the angle information, the above steps are repeated to perform multi-angle imaging, and the internal density distribution map of the celestial body is obtained.

[0032] Without extra artificial radioactive source, muons can directly penetrate into the small celestial body, and bring the internal information of the small celestial body to the detection layer, and the three-dimensional density structure of the small celestial body can be inverted according to the change of muon flux. The traditional detection method is abandoned, and the internal density structure of the small celestial body can be detected by using non-destructive, non-invasive device and remote sensing without any interference, and information such as whether there is a cavity and density anomaly can be detected, so as to provide a new detection method for in-situ resource utilization and defense of the small celestial body. It has the characteristics of high precision, high resolution and accurate determination of the position of density anomaly. BRIEF DESCRIPTION OF DRAWINGS

[0033] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the following drawings:

[0034] Figure 1 is an embodiment schematic diagram of a small celestial body density detection device based on cosmic rays of the present application;

[0035] Figure 2 is a detection layer schematic diagram of a small celestial body density detection device based on cosmic rays of the present application;

[0036] 1, muon; 2, first time flyer; 3, lead absorbing body; 4, detection layer; 4-1, first detection layer; 4-2, second detection layer; 5, radiation body; 6, second time flyer. DETAILED DESCRIPTION

[0037] The present application will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related application, and not to limit the application. In addition, it should be noted that, for the convenience of description, only the parts related to the application are shown in the drawings.

[0038] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and embodiments.

[0039] Embodiment 1

[0040] Please refer to Figure 1 and Figure 2The application discloses a small celestial body density detection device based on cosmic rays, which comprises a time flyer, an absorbing lead body, a radiation body and a detection layer.

[0041] The first direction is the direction of arrow A in the figure, and the time flyer is composed of a silicon microstrip or a plastic scintillator. Figure 1 The time flyer can distinguish the particles taken from the back of the detection device by the size of T1 and T2.

[0042] Working principle: the initial flux of muons 1 on the surface of the measured celestial body is obtained by calculation, the background particles are preliminarily screened out by the absorbing lead body, the particles enter the first time flyer, the absorbing lead body, the first detection layer, the radiation body and the second detection layer in sequence and are finally shot out from the second time flyer, the radiation body absorbs the muons and radiates out Cerenkov photons after the muons enter the radiation body, the Cerenkov photons form a Cerenkov radiation circle on the detection layer, the background particles are further screened out according to the Cerenkov radiation circle, the angle information of the group of muons is reconstructed by the first incident first position information L1, the first incident time T1, the second position information L2 and the second incident time information T2, the attenuation flux of the muons under the angle information is obtained by the collection and processing module by collecting the number of electric signals, the ratio of the initial flux to the attenuation flux is the attenuation flux of the muons under the angle information, the above steps are repeated to perform multi-angle imaging, and the internal density distribution diagram of the celestial body is obtained.

[0043] Without additional artificial radioactive sources, the muons 1 can directly penetrate the small celestial body, take the internal information of the small celestial body to the detection layer 4, and can be used to inverse the three-dimensional density structure of the small celestial body according to the flux change of the muons 1. The traditional detection method is abandoned, and the small celestial body can be detected by using a non-destructive, non-invasive device and remote sensing to detect the internal density structure, detect whether there is a cavity and density anomaly, and provide a new detection method for in-situ resource utilization and defense of the small celestial body. It has the characteristics of high precision, high resolution, and accurate determination of the position of the density anomaly.

[0044] Further, each group of detection layers 4 includes a plurality of parallelly arranged photomultiplier tubes SiPMs.

[0045] The photomultiplier tube SiPM is a silicon-based photoelectric conversion device, and the size is generally in the order of millimeters. Each detection layer 4 is formed by a SiPM tiled array. Each SiPM corresponds to a position code of the detection plane. When the muons 1 pass through the SiPM detection array, the position of the signal can be determined according to the SiPM code of the generated signal. The first position information L1 and the second position information L2 of the muons can be recorded by the multi-layer SiPM. The first position information L1 and the second position information L2 corresponding to the muons are connected to obtain the track of the particle.

[0046] The imaging principle of the muons 1 is that the attenuation of the muons 1 is positively correlated with the density and length of the material through which the muons 1 pass. By measuring the intensity attenuation of the muons 1 when passing through an object with unknown density length density*length, such as a small celestial body, the thickness density length can be known. In the present application, by calculating the track of the muons 1 passing through the detection device, the spatial distribution of the density length of the small celestial body can be obtained.

[0047] Specifically, according to the position information of the muons 1 detected by the detection layer 4, that is, the position coordinate information, the position information of a group of muons 1 on the first detection layer 4-1 is x1, y1, z1, and the position information on the second detection layer 4-2 is x2, y2, z2. The position coordinate information of each group is fitted by the least square method to obtain the straight line equation of the muon 1 track. The zenith angle of the muons 1 is calculated from the straight line equation of the muon 1 track. By calculating the density length under each fixed zenith angle, the density tomography of the small celestial body is inversed and cross analyzed by multi-angle observation to realize the detection of the internal density structure of the small celestial body.

[0048] Embodiment 2

[0049] A small celestial body density detection method based on cosmic rays, comprising the following steps:

[0050] S1, obtaining the initial flux of the muons on the surface of the measured celestial body;

[0051] Wherein, the muons 1 are mainly generated by the interaction of high-energy cosmic ray protons and the weathering layer of small celestial bodies such as asteroids and comets, and the number of muons 1 generated depends largely on the density of the surface layer, i.e. the weathering layer, and the shape of the asteroid. The initial muon 1 flux on the surface of the asteroid is analyzed in combination with the density and shape of the weathering layer measured by radar.

[0052] The muon 1 distribution generated according to the density relationship can be derived using a semi-empirical method. The cascade model extended by Gaisser in 1990, in which the generation of muons 1 is modeled as a balance between meson collision loss and decay. The contribution to the vertical differential flux of each meson m = π, K, D…, the muon 1 at sea level has the following formula:

[0053]

[0054] The muons 1 generated on the surface of a solid such as an asteroid can be obtained by the relationship with the atmospheric density. The atmospheric density on Earth generating muons 1 is about 3×10-4g / cm3. The vertical muon 1 flux of a small celestial body with a typical planetary weathering layer density of 1.6g / cm3, the effective depth corresponding to the density of 1000g / cm2 at sea level on Earth, the muon 1 flux is about three orders of magnitude smaller than the muon 1 flux at sea level.

[0055] S2, discriminating muons from background particles, and screening out muons passing through the interior of the celestial body;

[0056] Specifically, part of the background particles are absorbed by the lead body; the muons are discriminated from the remaining background particles by the Cherenkov ring information.

[0057] Wherein, screening out the muons 1 passing through the interior of the celestial body includes four parts, the first part is judged according to the time of the particles passing through the time flyer, the second part is discriminated by the flight speed of the particles passing through the detection layer 4, the third part is shielded by the lead absorber in the device to shield low-momentum particles, and finally whether the track of the particles passing through the detection layer 4 is a straight line to judge. Avoid the interference of the remaining background particles on the detection result.

[0058] S3, acquiring a plurality of sets of first position information L1 of muons collected by the first time flyer and a plurality of sets of second position information L2 of muons collected by the second time flyer within a preset time.

[0059] Wherein, the position coordinates of the muons 1 in the SiPM detection array are determined.

[0060] S4, selecting the first position information L1 and the second position information L2 of one set of muons, judging the incident direction, and reconstructing the angle information of the set of muons.

[0061] The judgment of the incident direction comprises: when the first incident time T1 is less than the second incident time T2, judging that the incident direction of the muon 1 is that the first time aircraft 2 points to the direction of the second aircraft; when the first incident time T1 is greater than the second incident time T2, judging that the incident direction of the muon 1 is that the second time aircraft 6 points to the direction of the first aircraft.

[0062] S5, counting the number of electric signals under the angle information, and inverting the attenuation flux of the muon 1 under the angle information;

[0063] S6, obtaining the density length of the celestial body under the angle information according to the ratio of the initial flux and the attenuation flux;

[0064] S7, repeating steps S4-S6, and obtaining the density distribution map of the celestial body by multi-angle density length inversion imaging.

[0065] Wherein, the position coordinate information of each group is fitted by the least square method to obtain a muon 1 track straight line equation; the zenith angle of the muon 1 is calculated by the muon 1 track straight line equation, the density length under each fixed zenith angle is calculated, the density tomography inversion of the small celestial body is realized, and the multi-angle observation cross analysis is realized, so that the density structure inside the small celestial body is detected.

[0066] The above description is only the preferred embodiment of the application and the explanation of the applied technical principles. It should be understood by those skilled in the art that the scope of the application involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features disclosed in the present application (but not limited to) having similar functions to form technical solutions.

Claims

1. A device for detecting the density of small celestial bodies based on cosmic rays, characterized in that, The application relates to a time-of-flight device for measuring the density distribution of a celestial body, comprising: a time-of-flight device, which comprises a first time-of-flight device (2) and a second time-of-flight device (6) arranged along a first direction, the first time-of-flight device (2) is used for recording first position information L1 and first incidence time T1 of a muon (1) passing through, the second time-of-flight device (6) is used for recording second position information L2 and second incidence time information T2 of the muon (1) passing through; and a mounting cavity is arranged between the first time-of-flight device and the second time-of-flight device (6); an absorbing lead body (3) is arranged in the mounting cavity, and the absorbing lead body (3) is used for absorbing part of background particles; a radiation body (5) is arranged in the mounting cavity, and the radiation body (5) is used for absorbing the muon (1) and radiating out Cerenkov photons; a detection layer (4) is arranged in the mounting cavity, the detection layer (4) comprises a first detection layer (4-1) and a second detection layer (4-2), and the first detection layer (4-1) and the second detection layer (4-2) are respectively arranged at two opposite side ends of the radiation body (5) along the first direction; the Cerenkov photons projected on the detection layer (4) form a Cerenkov light ring, and the detection layer (4) is used for converting optical signals into electrical signals; a collection and processing module is electrically connected with the detection layer (4) and is used for collecting the number of electrical signals and inversely calculating the attenuation flux of the muon (1). The detection layer (4) comprises a plurality of parallel arranged photomultiplier tubes. The time-of-flight device is composed of a plurality of groups of parallel arranged silicon microstrips or plastic scintillators. The radiation body (5) is composed of gas Ar / CH4 or silicon dioxide aerogel. The application further discloses a method for measuring the density distribution of a celestial body, comprising the following steps: S1, obtaining the initial flux of muons (1) on the surface of a measured celestial body; 2. The apparatus according to claim 1, wherein S2, distinguishing the muons (1) from background particles and screening out the muons (1) passing through the interior of the celestial body; 3. The apparatus according to claim 1, wherein S3, obtaining the first position information L1 of a plurality of groups of muons collected by the first time-of-flight device and the second position information L2 of a plurality of groups of muons (1) collected by the second time-of-flight device within a preset time; 4. The apparatus according to claim 1, wherein S4, selecting the first position information L1 and the second position information L2 of one group of muons (1), judging the incidence direction, and reconstructing the angle information of the group of muons (1); 5. A detection method based on the cosmic ray-based small celestial body density detection apparatus according to any one of claims 1 to 4, characterized by, S5, counting the number of electrical signals under the angle information, and inversely calculating the attenuation flux of the muon (1) under the angle information; S6, obtaining the density length of the celestial body under the angle information according to the ratio of the initial flux to the attenuation flux; S7, repeating steps S4-S6, inversely imaging the density length of the celestial body at multiple angles, and obtaining the density distribution diagram of the interior of the celestial body. The initial flux of the muons (1) on the surface of the measured celestial body is obtained according to the following formula: The distinguishing of the muons (1) from background particles comprises the following steps: S2-1, absorbing part of the background particles through the absorbing lead body (3); S2-2, distinguishing the muons from the remaining background particles through Cerenkov light ring information. The judging of the incidence direction comprises the following steps:

6. The detection method according to claim 5, characterized in that, when the first incidence time T1 is less than the second incidence time T2, the incidence direction of the muon (1) is judged to be the direction in which the first time-of-flight device (2) points to the second time-of-flight device. 。 7. The method of claim 6, wherein: ​ ​ ​ 8. The detection method of claim 7, wherein: ​ ​ When the first incident time T1 is greater than the second incident time T2, it is determined that the incident direction of the muon (1) is the direction of the second time spacecraft (6) pointing to the first spacecraft.

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