JP7269595B2 - Underground condition observation device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an underground state observation device, and more particularly to an underground state observation device that is placed underground and uses muons to observe the state of the earth.

Conventionally, as this type of technology, a well logging device that is inserted into a borehole and detects the density distribution of a stratum has been proposed (see, for example, Patent Document 1). In this well logging device, a detection unit composed of a pair of scintillators that emit light upon collision of muons and a plate-shaped deformation suppressing member arranged so as to be sandwiched by the matching scintillators is arranged in a cylindrical shape so that the longitudinal direction is the axial direction. The sensor is housed in a tubular case, and is constructed so that the detector can be rotated about its axis in the tubular case by a motor. Based on a pair of detection positions detected by the pair of scintillators and the rotation angle of the detection unit, the incoming direction of the muon is specified.

Also proposed is a muon detector used in a muography observation system that observes internal images of huge objects using muons (see, for example, Patent Document 2). This device comprises a plurality of gas detectors that detect muons by means of a plurality of wires arranged at regular intervals on a flat surface, a radiation shield made of a stainless steel case containing a lead plate, and an installation device. ing. The installation device is arranged so that the flat surfaces are parallel at a predetermined interval, and is arranged between a plurality of detector sockets to which each of the plurality of gas detectors can be attached and detached, and a radiation shield is attached and detached. The shielding socket is composed of a plurality of members that can be freely assembled and disassembled. As a result, even when access to the installation location is difficult, the disassembled installation device can be transported to the installation location and reassembled.

JP 2014-126407 A JP 2017-198482 A

However, since the above-mentioned logging apparatus uses a scintillator, when two points of the two scintillator detectors are simultaneously detected by an electromagnetic shower (mainly charged electrons e ⁻ and e ⁺ ), the two points are connected. A muon may be mistakenly detected as having passed through a straight line. In addition, since the detector is rotated by a motor, the configuration of the apparatus becomes complicated, which limits the number of muons that can be detected.

On the other hand, the above-mentioned muon detector has a large size, so although it is suitable for observing the internal image of a huge object, it is not suitable for observing the state of the ground by placing it in the ground.

An object of the present invention is to propose a compact, accurate and simple device for observing underground conditions.

The underground state observation apparatus of the present invention employs the following means in order to achieve the above-described main object.

The underground state observation device of the present invention is
An underground state observation device that is placed underground and uses muons to observe the state of the underground,
A plurality of observation units comprising a plurality of rectangular gas detectors that detect muons using a plurality of wires arranged at equal intervals on a flat surface, and a lead plate radiation shield placed between the gas detectors. have
The plurality of observation parts are arranged in a row, and a normal line from the center of the flat surface of the gas detector in at least one observation part and a normal line from the center of the flat surface of the gas detector in the other observation parts and are arranged in a twisted position,
It is characterized by

In the underground state observation apparatus of the present invention, a plurality of rectangular gas detectors that detect muons by a plurality of wires arranged at equal intervals on a flat surface, and lead plates placed between the gas detectors. a radiation shield; and a plurality of observation units. A gas detector has a spatial resolution as small as about 1/10 that of a general scintillator detector. Therefore, the thickness of lead in the radiation shield required to remove electromagnetic showers (mainly charged electrons e ⁻ and e ⁺ ) acting as noise during muon detection can be reduced to ⅕ or less. Also, gas detectors are lighter than scintillator detectors. As a result, it is possible to make the underground state observation device smaller and more accurate than the case where the underground condition observation device having the same performance is configured using the scintillator detector. In addition, a plurality of observation parts are arranged in a row, and the normal line from the center of the flat surface of the gas detector in at least one observation part and the normal line from the center of the flat surface of the gas detector in the other observation parts is positioned at the twist position. In one observation unit, the observation range is the range that can pass through the outermost gas detector. can be Since it is only necessary to arrange a plurality of observation units at twisted positions, the configuration can be simpler than that having a mechanism for rotating the observation units, and the incoming direction of muons can be determined without considering the rotation angle. can be detected. As a result, it is possible to observe underground conditions with a compact, accurate and simple configuration.

In the underground condition observation apparatus of the present invention, the plurality of observation units may be two observation units arranged such that flat surfaces of the gas detector are different by 90 degrees. In this way, the apparatus can be made more compact since only two observation units are required.

The underground state observing apparatus of the present invention may also include a storage case formed in a cylindrical shape for storing the plurality of observation units. This makes it suitable for inserting into a borehole and observing the state of the ground. In this case, the plurality of observation units may be accommodated in the storage case such that the flat surface of the gas detector is parallel to the axis of the storage case.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows the outline of a structure of the underground state observation apparatus 20 of embodiment. 3 is a schematic cross-sectional view schematically showing a cross section passing through the central axis of the cylindrical shape of the muon detection device 22. FIG. FIG. 3 is a schematic cross-sectional view schematically showing an AA cross section of the muon detection device 22 in FIG. 2; 3 is a schematic external view schematically showing the external appearance of an observation unit 30. FIG. 4 is a configuration diagram schematically showing a configuration of part of the gas detector 40. FIG. FIG. 6 is a cross-sectional view of the BB plane of FIG. 5; 3 is an exploded perspective view showing the outline of the configuration of the radiation shield 50. FIG. FIG. 3 is an explanatory diagram showing the relationship between an observation unit 30 and an observation area;

Next, the form for implementing this invention is demonstrated. FIG. 1 is an explanatory diagram showing the outline of the configuration of an underground state observation device 20 of the embodiment. The underground state observation device 20 of the embodiment includes a muon detection device 22 that detects the passage of muons placed in the ground, and an analysis device 60 that performs image analysis of the underground state using the detection results of the muon detection device 22. And prepare. The muon detector 22 is connected to the analyzer 60 via a wired or wireless data transfer link. As shown in FIG. 1, the analysis device 60 is constructed by installing an underground condition analysis program 62 as application software in a general-purpose computer. The computer includes a CPU, ROM, RAM, graphic processor (GPU), graphic memory (VRAM), system bus, hard disk drive (HDD), etc. (not shown), and the hard disk drive stores an underground state analysis program 62 and the like. . The underground state analysis program 62 is composed of an input module 64 for inputting data, an analysis module 66 for analyzing the state of the underground using the input data, and an output module 68 for outputting analysis results. there is A display 70 as a display device, and a keyboard 72 and a mouse 74 as input devices are connected to the computer. In addition, the underground state analysis by the underground state analysis program 62 is basically the same as the well-known technology (for example, the technology described in Japanese Patent Application Laid-Open No. 2013-156099), and does not form the core of the present invention. , the detailed description of which is omitted.

The muon detection device 22 is configured in a cylindrical shape so as to be inserted into the borehole 10 . FIG. 2 is a schematic cross-sectional view schematically showing a cross section passing through the central axis of the cylindrical shape of the muon detection device 22, and FIG. 3 is a schematic cross section of the muon detection device 22 in FIG. It is a sectional view. As illustrated, the muon detector 22 includes a cylindrical housing case 24 and two observation units 30 housed in the housing case 24 in two stages. FIG. 4 is a schematic external view schematically showing the external appearance of the observation unit 30. As shown in FIG. The observation unit 30 includes four gas detectors 40 formed in a flat, substantially square shape, and three radiation shields 50 formed in a flat, substantially square shape and arranged between the gas detectors 40. It is configured to have a substantially regular hexahedral shape as a whole. In the two observation units 30, the normals at the centers of the flat surfaces of the gas detectors 40 of the two observation units 30 are twisted, and the flat surfaces of the gas detectors 40 of the two observation units 30 are different by 90 degrees. Furthermore, the flat surfaces of the gas detectors 40 of the two observation units 30 are housed in the storage case 24 so as to be parallel to the central axis of the storage case 24 .

FIG. 5 is a configuration diagram schematically showing a configuration of part of the gas detector 40, and FIG. 6 is a cross-sectional view taken along line BB of FIG. 5 is a cross-sectional view taken along line CC of FIG. The gas detector 40 is configured as a well-known gas wire chamber (MWPC: Multi Wire Proportional Chamber) with two cathode planes 42a, 42b and two cathode planes 42a . A plurality of anode wires 44(1), 44(2), . 44(n), and a plurality of field forming wires 45(1), 45(2), . A plurality of signal collection wires 46(1), 46(2), . , 46(m) and a plurality of field forming wires 45(1), 45(2), . and a plurality of signal readout units 47 connected to (n). The internal space of the gas detector 40 is filled with a nonflammable and nontoxic mixed gas of argon (Ar) and carbon dioxide (CO ₂ ). This gas detector 40 can perform detection in two directions (x direction and y direction) with a single signal. In this embodiment, the gas detector 40 uses 20 μm diameter wires as the plurality of anode wires 44(1), 44(2), . 45(2), . A 100 μm wire was used.

FIG. 7 is an exploded perspective view showing an outline of the configuration of the radiation shield 50. As shown in FIG. As shown in the figure, the radiation shield 50 includes a lower frame 52 made of stainless steel, a lid 54 made of stainless steel, and a lead plate 56 housed in a flat, substantially square housing portion 53 formed in the lower frame 52. It is configured.

FIG. 8 is an explanatory diagram showing the relationship between the observation section 30 and the observation area. The muon detection device 22 in the underground state observation device 20 of the embodiment detects the muons coming from the area A side and the area C side in the figure, and the flat surface of the gas detector 40 is parallel to the horizontal direction in the figure. (one of the two observation units 30), and the muons coming from the area B side and the area D side in the figure are observed when the flat plane of the gas detector 40 is parallel to the vertical direction in the figure. It can be detected by the unit 30 (the other of the two observation units 30). Therefore, the two observation units 30 can detect muons coming from substantially the entire circumference of the muon detector 22 in the radial direction.

In the underground state observation device 20 of the embodiment, the muon detection device 22 is configured by arranging the four gas detectors 40 at equal intervals so that their flat surfaces are parallel to each other. When reaction points not aligned above are observed, the reaction points are determined to be noise, and when reaction points are observed to be aligned on a straight line at the same time in each gas detector 40, the reaction points are determined to be caused by muons. discriminate. As a result, erroneous detection due to noise such as electromagnetic shower can be suppressed.

In the underground condition observing apparatus 20 of the embodiment described above, the four gas detectors 40 arranged at equal intervals on a flat surface, and the three radiation shields 50 made of lead plates placed between the gas detectors 40. Two observation units 30 are provided. Since the gas detector 30 has a spatial resolution as small as about 1/10 that of a scintillator detector, in order to remove electromagnetic showers (mainly charged electrons e ⁻ and e ⁺ ) that act as noise during muon detection, The lead thickness in the required radiation shield can be reduced. Also, the gas detector 40 is lighter than a scintillator detector. As a result, it is possible to make the underground state observation device smaller and more accurate than the case where the underground condition observation device having the same performance is configured using the scintillator detector. Further, in the underground state observation device 20 of the embodiment, the two observation units 30 are arranged such that the normal to the center of the flat surface of the gas detector 40 of the two observation units 30 is twisted and the two observation units 30 The storage case 24 is arranged so that the flat surfaces of the gas detectors 40 of the two observation units 30 are different from each other by 90 degrees, and that the flat surfaces of the gas detectors 40 of the two observation units 30 are parallel to the central axis of the storage case 24. Store in This makes it possible to detect muons coming from substantially the entire circumference of the muon detector 22 in the radial direction. Therefore, the configuration can be simpler than that having a mechanism for rotating the observation section, and the incoming direction of the muon can be detected without considering the rotation angle. As a result, it is possible to observe underground conditions with a compact, accurate and simple configuration.

In the underground state observation device 20 of the embodiment, the two observation units 30 are arranged such that the normal to the center of the flat surface of the gas detector 40 of the two observation units 30 is at a twisted position and the gas of the two observation units 30 The detectors 40 are housed in the storage case 24 so that the flat surfaces of the gas detectors 40 differ by 90 degrees, and furthermore, the flat surfaces of the gas detectors 40 of the two observation units 30 are parallel to the central axis of the storage case 24. and However, three or more observation units 30 may be housed in the housing case. When three observation units 30 are housed, the gas detectors 40 of the three observation units 30 may be arranged in three stages so that the flat surfaces of the gas detectors 40 of the three observation units 30 differ by 60 degrees. In this case, the gas detectors 40 of the four observation units 30 may be arranged in four stages so that the flat surfaces of the gas detectors 40 differ by 45 degrees.

In the underground state observation device 20 of the embodiment, the muon detector 22 is inserted into the borehole, but the muon detector 22 may be installed in the ground instead of being inserted into the borehole. In this case, the shape of the storage case 24 is not limited to a cylindrical shape, and may be rectangular.

In the muon detection device 22 in the underground state observation device 20 of the embodiment, the four gas detectors 40 are arranged at equal intervals so that their flat planes are parallel. Since it is enough, it does not matter if they are arranged at non-equidistant intervals. Also, the number of gas detectors 40 is not limited to four, and may be three or less or five or more.

In the muon detection device 22 in the underground state observation device 20 of the embodiment, the lead plate 56 is housed by the lower frame 52 and lid 54 made of stainless steel, but the lower frame 52 and lid 54 are made of stainless steel. It is not limited to being made of metal, but may be made of other metal material, or may be made of hardened plastic or the like.

Although the embodiments for carrying out the present invention have been described above, the present invention is by no means limited to such embodiments, and can be implemented in various forms without departing from the gist of the present invention. Of course.

INDUSTRIAL APPLICABILITY The present invention is applicable to the manufacturing industry of underground state observation devices.

20 underground state observation device, 22 muon detection device, 24 storage case, 30 observation unit, 40 gas detector, 42a, 42b cathode plane, 44 (1), 44 (2), ..., 44 (n) anode wire, 45(1), 45(2), ..., 45(n) field wire, 47 signal readout section, 48 signal readout section, 50 radiation shield, 52 lower frame, 53 storage section, 54 lid, 56 lead plate, 60 analysis Apparatus, 62 Underground Condition Analysis Program, 64 Input Module, 66 Analysis Module, 68 Output Module, 70 Display, 72 Keyboard, 74 Mouse.

Claims (4)

An underground state observation device that is placed underground and uses muons to observe the state of the underground,
A plurality of observation units comprising a plurality of rectangular gas detectors that detect muons using a plurality of wires arranged at equal intervals on a flat surface, and a lead plate radiation shield placed between the gas detectors. have
The plurality of observation parts are arranged adjacent to each other in a line, and a normal line from the center of the flat surface of the gas detector in at least one observation part and the flatness of the gas detector in other observation parts It is arranged so that the normal from the center of the surface is at a twisted position, and is further stored in the same storage case,
Underground condition observation equipment. The underground state observation device according to claim 1,
The plurality of observation units are two observation units arranged such that flat surfaces of the gas detector are different by 90 degrees,
Underground condition observation equipment. The underground state observation device according to claim 1 or 2,
The storage case is formed in a cylindrical shape,
Underground condition observation equipment. The underground state observation device according to claim 3,
The plurality of observation units are housed in the storage case such that the flat surface of the gas detector is parallel to the axis of the storage case.
Underground condition observation equipment.

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