JP6587126B2 - Radiation calculation apparatus, radiation calculation method, and radiation calculation program - Google Patents

Description

  The present invention relates to a technique for calculating the behavior of radiation.

  Due to advances in computer technology, it is now possible to accurately calculate radiation behavior on a computer. For example, it is possible to accurately calculate the amount of energy loss when radiation passes through a substance based on physical quantities such as the mass and charge of the radiation and the type and mass of atoms of the substance through which the radiation passes. It is also possible to perform a simulation method called Monte Carlo simulation on a computer. In this method, a random number is generated on a computer, and the behavior of radiation is determined based on the random number. Since the behavior of radiation passing through a substance is generally a stochastic event, the behavior of radiation can be predicted probabilistically by doing so. In addition, it is possible to predict the behavior of radiation when passing through a member having a complicated structure that is difficult to calculate analytically by using Monte Carlo simulation. Using such a technique, in the field of radiation measurement, the behavior of radiation that has passed through a substance and reached a radiation detector is calculated (Patent Document 1).

Special table 2008-525968 gazette

  However, there has been a problem that the amount of calculation becomes large when trying to calculate the behavior of such radiation using a large amount of radiation from various directions such as cosmic rays. For example, in the case of cosmic rays, cosmic rays are frequently applied to even a small area (about one frequency per minute per square centimeter), so substances are applied to cosmic rays that fall into a certain area. If it is going to calculate the behavior when passing, the number of cosmic rays will become enormous, and the calculation amount will become enormous accordingly. Similarly, when trying to calculate the behavior of radiation for situations where gamma rays come from various directions or neutrons come from various directions, the amount of radiation becomes enormous and the amount of computation becomes enormous. End up. For these reasons, it has been difficult to calculate the behavior of radiation.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a technique capable of calculating the behavior of radiation coming from various directions when passing through a substance.

In order to solve at least a part of the problems described above, the radiation calculation apparatus of the present invention employs the following configuration. That is,
A radiation calculation device that calculates a physical quantity of radiation after passing through the material for radiation incident on the material from a plurality of directions,
Substance information storage means for storing the composition and geometric structure of the substance;
Physical quantity calculation position storage means for storing a physical quantity calculation position which is a position where the physical quantity of the radiation is calculated;
An incident direction determining means for determining an incident direction of the radiation to the physical quantity calculation position;
Incident direction substance information acquisition means for acquiring composition and geometric structure information of the substance along the incident direction from the physical quantity calculation position;
Behavior information acquisition means for acquiring behavior information when radiation passes through the substance having the acquired composition and geometric structure;
And a physical quantity calculation means for calculating the physical quantity of the radiation from a plurality of directions at the physical quantity calculation position based on the behavior information regarding the plurality of incident directions.

Further, the radiation calculation method of the present invention corresponding to the above-described radiation calculation apparatus is as follows.
A radiation calculation method for calculating a physical quantity of the radiation after passing through the substance with respect to radiation incident on the substance from a plurality of directions,
A substance information storing step for storing the composition and geometric structure of the substance;
A physical quantity calculation position storing step for storing a physical quantity calculation position which is a position where the physical quantity of the radiation is calculated;
An incident direction determining step for determining an incident direction of the radiation to the physical quantity calculation position;
Incident direction material information acquisition step for acquiring information of the composition and geometric structure of the material along the incident direction from the physical quantity calculation position;
A behavior information acquisition step of acquiring behavior information when radiation passes through the substance having the acquired composition and geometric structure;
And a physical quantity calculation step of calculating the physical quantity of the radiation from a plurality of directions at the physical quantity calculation position based on the behavior information regarding the plurality of incident directions.

  In the calculation apparatus and calculation method of the present invention, the composition and geometric structure of the substance through which the radiation passes are stored. Here, the composition of the substance may be anything as long as it characterizes the physical properties of the substance. For example, it may be the mass of the substance, or it may be the number of atoms, atomic number, ratio of each constituent element, mass number, radiation length, nuclear reaction cross section, etc., and various physical quantities can be used. It is. The geometric structure may be the shape of the substance, or may be a more complicated structure such as three-dimensional CAD data. Moreover, you may memorize | store combining the composition and geometric structure of a substance for each part which comprises the substance. For example, for each part of the substance, three-dimensional CAD data storing the composition information such as the type and material of the atom and the geometric structure thereof may be used.

  In the calculation apparatus and calculation method of the present invention, a physical quantity calculation position that is a position for calculating a physical quantity of radiation is stored, and a direction in which the radiation is incident on the physical quantity calculation position is determined. Various methods can be employed to determine the incident direction. For example, if you are targeting cosmic rays near the ground, cosmic rays will flow from any direction in the sky, so if you extend the line segment from the physical quantity calculation direction to each direction in the sky, It is thought that there are incident cosmic rays along the line. Therefore, the direction along such a line segment may be determined as the incident direction.

  When the incident direction is determined, the composition and geometric structure of the substance are acquired along the incident direction from the physical quantity calculation position. For example, what is necessary is just to acquire the information which arranged the kind and thickness of the element of a substance in a straight line along the line segment. Of course, the information may not be acquired in a straight line but may be acquired as two-dimensional or three-dimensional information having a spread. In the present invention, “from the physical quantity calculation position along the incident direction” is not limited to starting acquisition of the composition and geometric structure of the substance from the physical quantity calculation position, but along the incident direction. As long as they are acquired, they may be acquired in any order. For example, acquisition may be started from the opposite side of the physical quantity calculation position along the incident direction, or acquisition may be started from an arbitrary position. The composition and geometric structure can be obtained in any order.

  When the composition and the geometric structure are acquired, information on the behavior of the radiation passing through the material having the composition and the geometric structure is acquired. The information to be acquired may be any information as long as it represents the physical properties of radiation. For example, it may be the energy of radiation after passing through the substance, or it may be momentum. These may be various physical quantities, or may be a scattering angle at which radiation is scattered by a substance, a probability that radiation is scattered at a predetermined angle, a probability that radiation is blocked by a substance, and the like. Various methods can be used for the acquisition. For example, by using a Monte Carlo simulation method, various physical quantities after the radiation passes through the material having the composition and geometric structure acquired previously, What is necessary is just to calculate and acquire a probability. Alternatively, the composition, geometric structure, physical quantity, and the like may be associated in advance and acquired from there.

  When the physical quantity for one incident direction is acquired in this way, the physical quantity of radiation from a plurality of directions at the physical quantity calculation position is calculated based on the acquisition result for the plurality of incident directions. When calculating the physical quantities of radiation from a plurality of directions, any method may be used as long as the acquisition results for the individual incident directions are used. For example, simply by collecting the acquisition results for each incident direction, the physical quantities of radiation from a plurality of directions are acquired.

  In general, when examining the behavior of radiation by Monte Carlo simulation or the like, it is often desirable to examine the behavior of radiation at the position of the radiation detector. Therefore, in the calculation apparatus and calculation method of the present invention, the incident direction of radiation is limited by determining the incident direction using the physical quantity calculation position as a binding point. At the same time, radiation behavior information is acquired for radiation incident on the incident direction and position. In this way, even when examining the behavior of radiation incident from various directions over a wide range, the incident direction of the radiation can be limited and the incident position can be limited as the incident direction is limited. The number of target radiation can be reduced. This makes it possible to calculate the behavior when passing through a substance, avoiding a situation in which the amount of calculation becomes enormous for radiation coming from various directions.

  In general, for radiation incident from one direction, it is possible to accurately determine the behavior when passing through a substance by using a Monte Carlo simulation method or by calculating using a theoretical formula. is there. That is, in the present invention, it is possible to accurately acquire the behavior of radiation from one incident direction. For example, the distribution of energy loss when radiation from the incident direction passes through the substance can be calculated with high accuracy. By using such an accurate distribution, it is possible to accurately calculate what energy distribution the cosmic ray from the incident direction has at the physical quantity calculation position. In the present invention, it is possible to obtain physical quantities of radiation from a plurality of incident directions based on such accurate behavior information for each incident direction. As described above, it is possible to accurately calculate the physical quantity of radiation at the physical quantity calculation position while making it possible to suppress the calculation quantity.

  In general, when trying to calculate by limiting the radiation, the calculation accuracy may be greatly deteriorated or unexpected bias may occur in the calculation result due to the limitation of the radiation to be calculated. . In this regard, in the present invention, since a simple method of determining the incident direction is used, it is possible to avoid occurrence of an unexpected bias or a significant deterioration in calculation accuracy. In addition, even if radiation that has passed through a substance with a complicated structure is targeted, it is only necessary to determine the direction of incidence, so calculation can be performed quickly while suppressing significant deterioration in calculation accuracy and occurrence of bias. Is feasible.

  The physical quantity to be calculated may be any physical quantity as long as it represents the physical properties of radiation. For example, it may be radiation energy, radiation momentum, or radiation wavelength, frequency or speed. Furthermore, it may be a simple physical quantity related to the position of radiation such as coordinate values.

  In the radiation calculation apparatus and the radiation calculation method of the present invention, the second physical quantity calculation position may be stored, and the direction connecting the physical quantity calculation position and the second physical quantity calculation position may be set as the incident direction. And while acquiring the behavior information (2nd behavior information) of the radiation which injects into a 2nd physical quantity calculation position from an incident direction, it is good also as what calculates the difference between 2nd behavior information and behavior information.

  When investigating the behavior of radiation passing through a substance, it may be desirable to calculate the difference in radiation behavior before and after passing through the substance. Therefore, the direction connecting the two physical quantity calculation positions is determined as the incident direction, and the composition and geometric structure of the substance are acquired for the incident direction. In addition, the behavior of radiation with respect to the composition and geometric structure is acquired, and the behavior of radiation incident on the second physical quantity calculation position from the incident direction is acquired. Then, the difference between the radiation behavior at the second physical quantity calculation position and the radiation behavior at the physical quantity calculation position is calculated. By doing so, it is possible to calculate the difference and fluctuation in the behavior of radiation before and after passing through the substance. In such a case, even when radiation is incident from a plurality of directions, calculation can be performed while avoiding a situation in which the calculation amount becomes enormous.

  Note that “calculating the difference” does not only mean performing subtraction, but may be anything that calculates the difference. For example, a difference expressed by means other than a numerical value, such as a difference in physical quantity distribution, may be calculated. Of course, a simple difference between the physical quantity at the second physical quantity calculation position and the physical quantity at the physical quantity calculation position may be calculated.

  Moreover, in the radiation calculation apparatus and the radiation calculation method of the present invention, the frequency of radiation flying to the physical quantity calculation position may be calculated.

  When the radiation passes through the substance, the radiation may not reach the target position because the radiation is shielded or scattered by the substance. For this reason, there is a case where it is desired to calculate the frequency of radiation arrival at the target position. Therefore, if the flying frequency is calculated, it is possible to avoid the situation where the calculation amount becomes enormous even when a large number of radiations fly, and to calculate the radiation flying frequency, Is preferred.

  Further, in the radiation calculation apparatus and the radiation calculation method of the present invention, information on a deviation between the radiation traveling direction and the incident direction is acquired, and the incident angle of the radiation at the physical quantity calculation position is determined based on the information on the deviation. It may be calculated.

  When radiation passes through a substance, the direction of travel may change, and there are cases where it is desired to calculate how the change in the direction of travel occurs at the physical quantity calculation position. Therefore, if information on the deviation in the traveling direction is acquired for each incident direction in this way, it is preferable that the incident angle of radiation at the physical quantity calculation position can be calculated based on the information.

Furthermore, the present invention can be realized using a computer by causing a computer to read a program for realizing the radiation calculation method described above and executing a predetermined function. Therefore, the present invention includes the following program or a mode as a recording medium on which the program is recorded. That is, the program of the present invention corresponding to the radiation calculation apparatus described above is
A program for realizing, using a computer, a radiation calculation method for calculating a physical quantity of radiation after passing through the material for radiation incident on the material from a plurality of directions,
A function (A) for storing the composition and geometric structure of the substance;
A function (B) for storing a physical quantity calculation position which is a position where the physical quantity of the radiation is calculated;
A function (C) for determining an incident direction of the radiation to the physical quantity calculation position;
A function (D) for acquiring information on the composition and geometric structure of the substance along the incident direction from the physical quantity calculation position;
A function (E) for obtaining behavior information when radiation passes through the substance having the obtained composition and geometric structure;
The gist is to realize, by a computer, a function (F) for calculating the physical quantity of the radiation from a plurality of directions at the physical quantity calculation position based on the behavior information regarding the plurality of incident directions.

  If such a program is read into a computer and each of the above functions is realized, the behavior can be calculated even for radiation coming from a plurality of directions.

It is explanatory drawing which showed the structure of the simulation system 10 of a present Example. It is the schematic diagram which illustrated the structure of the object which simulates using the simulation system 10 of a present Example. It is explanatory drawing which showed the flow of the simulation process in the simulation system 10 of a present Example. It is the schematic diagram which showed notionally the mode of determining the incident direction of a cosmic ray. It is explanatory drawing which showed notably the mode that the structure information of a substance was acquired about an incident direction. It is explanatory drawing which showed a mode that an energy loss was calculated using the method of a Monte Carlo simulation. It is explanatory drawing which illustrated distribution of the energy loss amount of the cosmic ray of energy 10GeV. It is explanatory drawing which showed a mode that the direction distribution of the flying frequency was acquired based on the flying frequency of the cosmic ray from each incident direction. It is explanatory drawing which illustrated energy distribution of the cosmic ray which pours on the ground surface. It is explanatory drawing which illustrated a mode that the distribution of the angle shift | offset | difference of the cosmic ray was acquired about each incident direction. It is explanatory drawing which illustrated a mode that the direction distribution of angle deviation was acquired. It is explanatory drawing which illustrated a mode that the energy distribution of the cosmic ray was acquired about each incident direction. It is explanatory drawing which illustrated a mode that the direction distribution of the energy of the cosmic ray was acquired. It is explanatory drawing which illustrated a mode that the distribution of the momentum of the cosmic ray was acquired about each incident direction. It is explanatory drawing which illustrated a mode that the direction distribution of the average momentum of a cosmic ray was acquired. It is explanatory drawing which illustrated a mode that the radiation detector was arrange | positioned also in the position before passing underground.

Hereinafter, in order to clarify the contents of the present invention described above, examples will be described in the following order.
A. Overall system configuration:
B. Simulation processing:
C. Variation:
C-1. First modification:
C-2. Second modification:
C-3. Third modification:
C-4. Fourth modification:
C-5. Fifth modification:

A. Overall system configuration:
FIG. 1 is an explanatory diagram showing a configuration of a simulation system 10 according to the present embodiment. As shown in the figure, the simulation system 10 according to the present embodiment includes a server device 100 including a CPU, a ROM, a RAM, and the like, and a disk device 104 connected to the server device 100.

  As shown in the figure, the server device 100 is connected to a network line via a network interface circuit (NIC), and can be connected to an external computer terminal device 200 via the network line. It is also possible to connect to a mobile communication device such as a mobile phone 300 or a tablet terminal via a wireless base station such as a mobile phone base station or a public wireless LAN base station connected to a network line.

  As described above, the computer terminal device 200 can be connected to the server device 100 via the network line, and can acquire various data and programs from the server device 100. The user of the simulation system 10 of the present embodiment connects to the server device 100 using the computer terminal device 200 and executes a program on the server device 100 to execute a simulation of the behavior of radiation. Can be confirmed on the screen of the computer terminal device 200.

  FIG. 2 is a schematic view illustrating a target structure to be simulated using the simulation system 10 of this embodiment. As shown in the figure, a tunnel is formed in the ground, and a radiation detector is attached to the ceiling of the tunnel. Moreover, in the ground above the tunnel, a cavity having a diameter of about 1 m exists.

  Cosmic rays are pouring down from all directions on the ground, but cosmic rays have high penetrating power, so cosmic rays that pour into the ground penetrate the ground and reach the radiation detectors installed on the tunnel ceiling. The cosmic rays that have penetrated the ground in this way can be detected by the radiation detector. In addition, if a detector capable of measuring the incident angle of cosmic rays, such as a nuclear dry plate or a detector having a scintillator stacked thereon, is used, it is possible to measure the direction of the cosmic rays.

  Here, by measuring these cosmic rays, it is possible to explore the interior of the material that has passed through. For example, although cosmic rays have strong penetration, they lose energy when they pass through the ground, so there are cosmic rays that lose energy and stop in the ground and do not reach the radiation detector. . In general, the amount of energy lost when a cosmic ray passes through a substance is roughly proportional to the mass of the passing substance. Then, in the structure of FIG. 2, cosmic rays do not lose much energy at the position of the cavity, so that more cosmic rays reach from the direction passing through the cavity than in other directions. Thus, by measuring the arrival number of cosmic rays from each direction with a ray detector and comparing the arrival numbers for each direction, it is possible to detect the presence of a cavity in the ground and the position of the cavity.

  When such a measurement is performed, it is predicted in advance how much cosmic rays will come from which direction to the radiation detector. For the prediction, it is conceivable to perform so-called Monte Carlo simulation using a computer. However, a large amount of calculation is required to simulate the behavior of cosmic rays falling from all sides into such a large area. For example, if we consider cosmic rays that fall within a 10-meter x 10-month period, about 40 billion cosmic rays will fall. Calculations must be performed for such a large amount of cosmic rays, and the amount of calculation becomes enormous. Therefore, in the simulation system 10 of the present embodiment, the following method is used to avoid the enormous amount of calculation even when dealing with cosmic rays falling from all directions, and the direction and flight of cosmic rays. The number can be calculated.

B. Simulation processing:
FIG. 3 is an explanatory diagram showing a flow of simulation processing in the simulation system 10 of the present embodiment. Such a process is a process in which an instruction reaches the server apparatus 100 via a network line when the user operates the computer terminal apparatus 200, and execution is started on the server apparatus 100 in response to the instruction. In this embodiment, a case where a simulation is performed on the structure shown in FIG. 2 will be described as an example.

  As shown in the figure, first, a process of reading the structure of a structure to be simulated is performed (step S200). In the present embodiment, processing for reading three-dimensional CAD data representing the structure shown in FIG. 2 is performed. Thereby, the simulation system 10 of a present Example can grasp | ascertain the geometric structure of the structure used as a simulation object, and the material composition of a structure based on the read three-dimensional CAD data.

  Subsequently, the process which reads the information of the installation position of a radiation detector is performed (step S202). Information on the installation position of the radiation detector may be included in advance in the structure information read in step S200, or when the simulation process is executed, the user operates the computer terminal device 200 to determine the setting position. It is good also as what to do. The installation position information of the radiation detector may be any information as long as the installation position of the radiation detector can be specified. For example, the coordinate value of the installation position may be specified using the coordinates in the three-dimensional CAD data read in the previous step S200. After the position information of the radiation detector is read, a process for determining the incident direction of the cosmic rays is performed (step S204).

  FIG. 4 is a schematic diagram conceptually showing how the incident direction of cosmic rays is determined. As described above, the cosmic rays fall from all directions on the ground, so that the cosmic rays also fly from all directions to the position of the radiation detector. For example, as shown in FIG. 4, when a line segment is extended upward from the position of the radiation detector (see the line segment indicated as “A” in the figure), the direction along the line segment is It is thought that there are incident cosmic rays. Therefore, the direction of this line segment may be determined as the incident direction of cosmic rays. Similarly, for the line segment indicated as “B” in the figure, it is considered that there is still a cosmic ray incident from the direction along the line segment. What is necessary is just to determine as an incident direction.

  In the above description, the incident direction indicated by “A” and the incident direction indicated by “B” in the figure have been described. However, the number of incident directions is not limited to two. Any number. For example, in the example of FIG. 4, in the range of the solid angle 2π in the sky direction, the incident direction may be determined by setting a line segment for each constant elevation angle and azimuth angle.

  In the example of FIG. 4, the horizontal direction (left-right direction in the figure) and the direction from the basement to the ground (direction from the bottom to the top of the figure) are not set as the incident direction, but the frequency is low, but from these directions However, since cosmic rays arrive, such a direction may be used as the incident direction. In the present embodiment, for a predetermined elevation angle range in the sky direction (a range between a line segment indicated by “A” and a line segment indicated by “D” in FIG. 4), the incident direction at every fixed angle. Will be described as determining the above.

  If the incident direction of the radiation is determined (step S204 in FIG. 3), a process of acquiring the substance configuration information is then performed for the determined radiation incident direction (step S206).

  FIG. 5 is an explanatory diagram conceptually showing the state of acquiring the substance configuration information in the incident direction. Here, a case will be described as an example where the configuration information of the substance is acquired along a line segment indicated by “A” in FIG. When going from the position indicated as “A” in FIG. 5A toward the radiation detector along the line segment “A”, the position indicated as “A ′” from the position indicated as “A”. Until there is air. And the soil exists from the position indicated as “A ′” to the position of the radiation detector. FIG. 5B shows a state in which these are arranged in the horizontal direction along the line segment “A”. FIG. 5B shows the positions of the above-mentioned “A”, “A ′”, and “radiation detector” along the horizontal axis (axis indicated as “X” in the drawing). Materials between A, “A ′” and “Radiation detector” are shown.

  When acquiring such information, the structure information read in step S200 in FIG. 3 may be used. For example, three-dimensional CAD data is used as the structure information, and the configuration information of the substance is set in association with each coordinate value of the position coordinates of the three-dimensional CAD data. And what is necessary is just to acquire the structure information of a substance about each position along a line segment.

  Note that various pieces of information can be used as the material configuration information. For example, it may be information about the atoms that make up the substance, such as the atomic number and atomic weight of the atoms that make up the substance, the number of charges, the composition ratio of each atom, or a physical quantity that is more macro than the information about the constituent atoms For example, information such as density (mass per unit volume) may be used.

  In the above description, the material configuration toward the radiation detector is obtained starting from the position indicated as “A” in FIG. 5A. However, the material configuration along the incident direction is As long as it can be acquired, any direction may be used. For example, it is good also as what is acquired toward the position shown as "A" in Drawing 5 (a) from the position of a radiation detector as the starting point.

  When the material configuration information is acquired (step S206 in FIG. 3), a process of calculating energy loss when cosmic rays are incident on the acquired material is performed (step S208). Various methods can be used for calculating the energy loss, but in the present embodiment, description will be made assuming that the energy loss is calculated using a Monte Carlo simulation method.

  FIG. 6 is an explanatory diagram showing how energy loss is calculated using a Monte Carlo simulation technique. FIG. 6 illustrates a substance structure corresponding to the configuration information acquired in FIG. 5 described above. An example in which a cosmic ray having an energy of 10 GeV is incident on the material having this structure from the left side of FIG. 6 will be described. First, the amount of energy loss of cosmic rays is calculated at a position where the cosmic rays have entered the air and advanced a little (the position indicated by the horizontal axis direction “a” in FIG. 6). The energy loss amount of cosmic rays depends on the composition of the passing substance, the passing distance, and the energy of cosmic rays, but the energy loss amount is not constant and is a probability event that becomes a different amount each time. Therefore, a random number is generated on the computer, and the amount of energy loss of cosmic rays is determined based on the random number. For example, a probability density function of the energy loss amount is prepared in advance, and the energy loss amount may be determined using the probability density function and a random number.

  When the amount of energy loss is determined, the amount of energy loss is subtracted from the energy of cosmic rays (10 GeV in this example) to determine the energy of cosmic rays at the position “a” in the figure. Next, the amount of energy loss is calculated by the same method at a position further advanced along the horizontal axis (a position indicated by “b” in the figure). This method is repeated, and the amount of energy loss is calculated while moving cosmic rays from the air to the soil. And it repeats until it passes through the soil and reaches the radiation detector.

  FIG. 7 is an explanatory diagram illustrating the distribution of the energy loss amount of cosmic rays having an energy of 10 GeV. As described above, since the energy loss amount can be calculated for one cosmic ray by the Monte Carlo simulation method, it is possible to obtain such a distribution by performing such calculation many times. As described above, since the energy loss of cosmic rays is a stochastic event, the amount of energy loss is not a constant value, but has a spread distribution as shown in FIG. It is possible to calculate the energy loss distribution for cosmic rays with energy other than 10 GeV by the same method.

  Focusing on the energy loss of cosmic rays here, when the energy loss of cosmic rays reaches the energy that cosmic rays originally had (more precisely, kinetic energy), the cosmic rays stop, Does not reach the radiation detector. Therefore, the cosmic ray whose energy loss is smaller than the initial energy is the cosmic ray that reaches the radiation detection. In the example of FIG. 7, the cosmic ray corresponding to the portion on the left side of the position indicated by “E” in the drawing (the hatched portion in the drawing) corresponds to the cosmic ray reaching the radiation detector. The ratio between the amount of cosmic rays in the hatched portion and the amount of the entire distribution corresponds to the frequency of cosmic rays reaching the radiation detector. Thus, the frequency of cosmic rays reaching the radiation detector can be acquired based on the distribution of the energy loss amount.

  The behavior of cosmic rays incident on the radiation detector can be grasped in the same manner for other incident directions. That is, in the example of FIG. 7A, since the flying frequency of 10 GeV cosmic rays can be obtained for the incident direction indicated as “A” in FIG. 4, by using the same method for the other incident directions, It is possible to acquire the flying frequency of 10 GeV cosmic rays. FIG. 7B illustrates an energy loss amount distribution in the incident direction indicated by “C” in FIG. As described above, since there is a cavity in the direction indicated by “C” in FIG. 4, the amount of energy loss is smaller than that in the direction indicated by “A”. Therefore, the distribution of FIG. 7B is a distribution shifted in a direction where the amount of energy loss is smaller than that of the distribution of FIG. Correspondingly, the amount of cosmic rays reaching the radiation detector (corresponding to the area of the hatched portion in FIG. 7B) is increased, and the cosmic rays from this incident direction The flying frequency is higher than the direction indicated by “A”.

  When the arrival frequency of the cosmic rays is thus obtained for each incident direction, the direction distribution of the arrival frequency of the cosmic rays at the radiation detector is obtained by superimposing the arrival frequencies of the incident directions (step S212 in FIG. 3). ).

  FIG. 8 is an explanatory view showing a state in which the direction distribution of the flying frequency is acquired based on the flying frequency of the cosmic rays from each incident direction. The horizontal axis of the graph in the figure is the elevation angle in the direction of flight of cosmic rays. In the drawing, elevation angles corresponding to the respective incident directions indicated by “A” to “D” in FIG. 4 are indicated by “A” to “D”, respectively. As described above, since the flying frequency of cosmic rays can be calculated for each incident direction, it is possible to obtain such a distribution by plotting the flying frequencies calculated for each incident direction.

  By generating the flying frequency distribution in this way, when a radiation detector is installed in the structure shown in FIG. 4, it is possible to predict how much cosmic rays will fly from which direction to the radiation detector. Become. That is, as shown in FIG. 8, since the relationship between the direction and the flying frequency can be acquired, the amount of cosmic rays flying from each direction can be calculated. For example, the amount of cosmic rays coming from each direction at the position of the radiation detector can be calculated based on the amount of cosmic rays falling on the ground surface per unit time and the distribution of FIG. More specifically, for example, based on the amount of cosmic rays (amount per unit time) falling on the ground surface from the direction indicated by “A” in the figure and the frequency from the direction “A” in FIG. It is possible to calculate the amount of cosmic rays (amount per unit time) arriving at the position of the radiation detector from the direction “A”.

  In this way, by calculating the amount of cosmic rays coming from each direction at the position of the radiation detector, it is possible to estimate what measurement results can be obtained when the radiation detector is actually installed. It becomes possible. For example, in the structure of FIG. 4 described in the present embodiment, it can be estimated that the amount of cosmic rays increases from the vicinity of the incident direction “C” as shown in FIG. It is also possible to estimate how many percent increase). In addition, depending on the degree of increase, it is possible to know how much cosmic rays need to be detected in order to detect the degree of increase. It is also possible to estimate the period required for detection and the size (area) of the radiation detector. By quickly estimating this, it is possible to set the radiation detector installation location, installation area, and installation angle more appropriately and perform more suitable measurement.

  As described above, in the simulation process of the present embodiment, the configuration information of the substance is acquired for each incident direction, and the flying frequency of cosmic rays is calculated for the incident direction. Then, the flying frequency of each incident direction is integrated to obtain the relationship between the incident direction and the flying frequency. In this way, even when examining a large-scale structure, it is only necessary to perform the Monte Carlo simulation only in the incident direction, so that it is possible to avoid a situation in which the amount of calculation becomes enormous. That is, in the simulation process of the present embodiment, the simulation is performed in the direction extending from the radiation detector, and this corresponds to the simulation of the cosmic rays passing through the radiation detector. For this reason, it is possible to omit the simulation of the cosmic rays that do not pass through the radiation detector. Thereby, even when a large amount of cosmic rays fall on a large-scale structure, it is possible to suppress the increase in the amount of calculation and calculate quickly.

  Moreover, in order to enable such an efficient simulation, it is not necessary to calculate the condition of cosmic rays passing through the radiation detector by complicated calculation, and it is only necessary to determine the incident direction, so it can be calculated quickly. is there. In addition, even when an object having a complicated structure is handled, the process for determining the incident direction does not become significantly complicated due to the complicated structure. For this reason, even when handling an object having a complicated structure, it is possible to perform a simulation quickly.

  In general, when calculating the behavior of radiation, if only specific radiation is selected and calculated, the calculation result may be biased or the error will increase. There is. In this respect, in this embodiment, since a simple method of determining the incident direction is used, it is possible to suppress the influence on the calculation result caused by selecting the cosmic ray passing through the radiation detector. It is. Thereby, it is possible to obtain a calculation result with high reliability.

  In addition, in the simulation method of the present embodiment, it is possible to accurately estimate the behavior of cosmic rays for each incident direction by using a Monte Carlo simulation method. For this reason, it is possible to calculate the behavior of the cosmic rays with high accuracy while suppressing the increase in calculation amount and enabling quick calculation.

  In the above-described embodiment, the distribution of the energy loss amount is obtained by the Monte Carlo simulation method. However, such a distribution may be prepared for each substance in advance. For example, the distribution of energy loss per unit thickness is prepared for various substances such as iron, water, soil, and concrete. And according to the structure of the substance used as object, it is good also as what acquires distribution of energy loss quantity by combining those distribution. In this way, it becomes possible to more quickly estimate the direction distribution of the frequency of arrival of cosmic rays while further reducing the amount of calculation.

C. Modified example:
C-1. First modification:
In the above-described embodiment, a 10 GeV cosmic ray has been described as an example. However, there are times when you want to study cosmic rays of various energies, not cosmic rays of a specific energy. In such a case, the behavior of the entire cosmic ray may be calculated by calculating the behavior of the cosmic ray for each energy of the cosmic ray and combining the calculation results.

  FIG. 9 is an explanatory diagram illustrating the energy distribution of cosmic rays falling on the ground surface. As shown in the figure, the cosmic rays falling on the surface of the earth have various energies. When calculating such cosmic rays as a whole, first, the behavior of cosmic rays is calculated for each energy of the distribution in the same manner as in the above-described embodiment. For example, in the example of FIG. 9, the distribution in the flying direction can be acquired for the energy indicated by “F” in the drawing in the same manner as in the above-described embodiment (see FIG. 8). Similarly, the distribution in the flying direction is acquired for the energy indicated as “G” and “H”. Then, by superimposing these distributions at a ratio (weight) reflecting the energy distribution of cosmic rays, a distribution corresponding to the entire energy of cosmic rays may be acquired. In this way, it is possible to make a more accurate estimation that reflects the energy distribution of cosmic rays.

  Alternatively, instead of obtaining the distribution of the flying frequency for each energy, the distribution may be obtained for each incident direction. In other words, the flying frequency in the incident direction may be calculated based on the energy distribution of the cosmic rays and the structure information of the material in the incident direction. For example, the energy of cosmic rays is determined based on the energy distribution of cosmic rays. Then, it is determined whether or not the substance corresponding to the configuration information acquired along the incident direction reaches the radiation detector when cosmic rays of that energy are incident. The determination may be made by the Monte Carlo simulation method described above. Alternatively, more simply, the energy required for cosmic rays to pass through the material may be calculated by numerical calculation or theoretical formula based on the material configuration information. When it is determined whether or not the cosmic ray of that energy reaches the radiation, the energy of the cosmic ray is again determined based on the energy distribution of the cosmic ray, and similarly it is determined whether or not it reaches the radiation detector. . By repeating such processing, it is possible to calculate the flying frequency of cosmic rays in the incident direction. In addition, different cosmic ray energy distributions can be used for each flight direction, so that the behavior of cosmic rays can be calculated more accurately.

  If such flying frequency calculation is performed for each of a plurality of incident directions, it is possible to acquire the direction distribution of the flying frequencies by synthesizing the flying frequencies of the respective incident directions as in the above-described embodiment. In such a case as well, it is only necessary to perform a simulation or the like only in the incident direction as in the above-described embodiment, so that it is possible to quickly estimate the behavior of cosmic rays while avoiding an increase in the amount of calculation. It is.

  In the above description, a simulation or the like is performed for each cosmic ray energy to determine whether or not it reaches the radiation detector. However, the amount of cosmic ray energy loss depends on the cosmic ray energy. Since there is no difference, it is possible to calculate the representative energy and estimate other energy from the calculation result of the representative energy. For example, a distribution of energy loss is calculated for a cosmic ray of 10 GeV as a representative value (see FIG. 7A). Further, the energy loss amount is determined based on the distribution of the energy loss amount. When the energy of the cosmic ray is determined based on the energy distribution of the cosmic ray, it is determined whether the cosmic ray reaches the radiation detector by comparing the energy loss amount with the energy of the cosmic ray.

  By doing so, it is not necessary to calculate for each energy of the cosmic ray, so that the calculation amount can be further suppressed and the behavior of the cosmic ray can be calculated more quickly.

C-2. Second modification:
In the above-described embodiments and modifications, it has been described that the flying frequency of cosmic rays is calculated, but other physical quantities representing the behavior of cosmic rays can also be calculated. For example, when a cosmic ray passes through a substance, the cosmic ray passes while being scattered by the substance, so that the traveling direction of the cosmic ray may deviate from the initial direction. Such a shift in the traveling direction (angle shift or position shift) may be calculated.

  FIG. 10 is an explanatory view exemplifying a state in which the distribution of angular deviation of cosmic rays is acquired for each incident direction. FIG. 10A illustrates the distribution of angular deviations with respect to the incident direction indicated as “A” in FIG. 4, and FIG. 10B illustrates the incident direction indicated as “C” in FIG. 4. An example of the distribution of angular deviations for is shown. In order to acquire such distribution, as in the above-described embodiment, first, the incident direction is determined, and the configuration information of the substance is acquired along the incident direction. Then, the behavior when the cosmic rays pass through the substance corresponding to the acquired configuration information is calculated using the Monte Carlo simulation method described above. In this case, each time the cosmic ray travels through the material, the scattering angle of the cosmic ray may be calculated by a probabilistic method. Then, the calculation may be repeated while changing the traveling direction of the cosmic rays by the amount of the scattering angle obtained by the calculation. By repeating such calculation for a plurality of cosmic rays, the distribution illustrated in FIG. 10 can be acquired.

  In general, the degree of scattering of cosmic rays (degree of angular deviation, degree of positional deviation) increases as the mass of the substance passing through and the number of protons in the atom increase. Therefore, the degree of scattering may be stored in association with each substance in advance, and the degree of scattering may be acquired therefrom. Further, since the degree of scattering varies depending on the energy and momentum of cosmic rays, the degree of scattering may be stored in association with energy and momentum.

  Once the cosmic ray angle deviation is calculated for each incident direction, it is possible to obtain the cosmic ray angle deviation direction distribution by combining them for a plurality of incident directions, as in the previous embodiment. is there.

  FIG. 11 is an explanatory diagram illustrating a state in which the direction distribution of angular deviation is acquired. As shown in the figure, the elevation angle viewed from the radiation detector is plotted on the horizontal axis. Further, the respective incident directions illustrated in FIG. 4 (see the line segments indicated by “A” to “D” in FIG. 4) are illustrated. On the vertical axis, the average value of the angle deviation is plotted for each incident direction. As described above, since there is a cavity in the direction indicated by “C” in FIG. 4, the degree of cosmic ray angle deviation is smaller than in other incident directions (FIG. 10A and FIG. 10). (See (b)). Corresponding to this, in the distribution of FIG. 11, a decrease in the amount of angular deviation is observed in the vicinity of the position indicated by “C” in the drawing, and the width of the reduced portion corresponds to the size of the cavity. is doing. As described above, it is possible to detect the existence of the cavity, estimate the position of the cavity, and estimate the size of the cavity by examining the degree of the angle deviation of the cosmic rays. Even in such a case, in this embodiment and the modification, it is possible to avoid the situation where the amount of calculation becomes large and to quickly calculate the behavior of the cosmic rays.

C-3. Third modification:
Alternatively, the energy of radiation may be calculated. For example, in the case of cosmic rays, energy is lost when passing through a substance, so that the energy is lower than the original at the position of the radiation detector. The energy of such cosmic rays may be calculated.

  FIG. 12 is an explanatory diagram illustrating the state in which the energy distribution of cosmic rays is acquired for each incident direction. FIG. 12A illustrates the energy distribution of cosmic rays in the incident direction indicated as “A” in FIG. 4, and FIG. 12B illustrates the incidence indicated as “C” in FIG. 4. The energy distribution of cosmic rays with respect to direction is illustrated. In order to acquire such distribution, as in the above-described embodiment, first, the incident direction is determined, and the configuration information of the substance is acquired along the incident direction. Then, the behavior when the cosmic rays pass through the substance corresponding to the acquired configuration information is calculated using the Monte Carlo simulation method described above. That is, each time a cosmic ray travels through a substance, the amount of energy loss of the cosmic ray is calculated by a probabilistic method, and the energy of the cosmic ray is reduced by the amount of energy loss obtained by the calculation. By repeating such calculation for a plurality of cosmic rays, the distribution illustrated in FIG. 12 can be acquired.

  When the state of cosmic ray energy is calculated for each incident direction, the direction distribution of cosmic ray energy can be obtained by combining them for a plurality of incident directions, as in the above-described embodiment.

  FIG. 13 is an explanatory diagram illustrating a state in which the directional distribution of energy of cosmic rays is acquired. As shown in the figure, the horizontal axis plots the elevation angle viewed from the radiation detector, and each position on the horizontal axis has each incident direction illustrated in FIG. 4 (“A” to “D” in FIG. 4). (See the line segment indicated). On the vertical axis, the average energy of cosmic rays is plotted for each incident direction. As described above, since there is a cavity in the direction indicated by “C” in FIG. 4, the energy loss of cosmic rays is small compared to other incident directions (FIGS. 12A and 12B). See). Corresponding to this, in the distribution of FIG. 13, an increase in the average energy of the cosmic rays is observed in the vicinity of the position indicated by “C” in the drawing, and the width of the rising portion is the size of the cavity. It corresponds to. Thus, by examining the energy of cosmic rays, it is possible to detect the presence of a cavity, estimate the location of the cavity, and estimate the size of the cavity. Even in such a case, in this embodiment and the modification, it is possible to avoid the situation where the amount of calculation becomes large and to quickly calculate the behavior of the cosmic rays.

C-4. Fourth modification:
Alternatively, the momentum of radiation may be calculated. For example, in the case of cosmic rays, energy is lost when passing through a substance, so the momentum decreases accordingly. As a result, at the position of the radiation detector, the cosmic rays have a lower momentum than originally. Such momentum may be calculated.

  FIG. 14 is an explanatory view exemplifying a situation in which the distribution of momentum of cosmic rays is acquired for each incident direction. FIG. 14 (a) illustrates the distribution of momentum of cosmic rays in the incident direction indicated as “A” in FIG. 4, and FIG. 14 (b) indicates “C” in FIG. The distribution of the momentum of cosmic rays with respect to the incident direction is illustrated. In order to acquire such a distribution, the incident direction is first determined as in the above-described embodiment, and then the substance configuration information is acquired along the incident direction. Then, the behavior when the cosmic rays pass through the substance corresponding to the acquired configuration information is calculated using the Monte Carlo simulation method described above. That is, every time the cosmic ray travels through the material, the reduction of the cosmic ray momentum is calculated by a probabilistic method, and the cosmic ray momentum is reduced accordingly. By repeating these calculations for a plurality of cosmic rays, the distribution illustrated in FIG. 14 can be acquired.

  Once the behavior of the cosmic ray momentum is calculated for each incident direction, it is possible to obtain the cosmic ray momentum direction distribution by synthesizing them for a plurality of incident directions, as in the above-described embodiment.

  FIG. 15 is an explanatory view exemplifying a state where the direction distribution of the average momentum of cosmic rays is acquired. As shown in the figure, the horizontal axis plots the elevation angle viewed from the radiation detector, and each position on the horizontal axis has each incident direction illustrated in FIG. 4 (“A” to “D” in FIG. 4). (See the line segment indicated). On the vertical axis, the average momentum of cosmic rays is plotted for each incident direction. As described above, since there is a cavity in the direction indicated by “C” in FIG. 4, the decrease in the momentum of the cosmic rays is small compared to other incident directions, and as a result, at the position of the radiation detector. The amount of exercise is high (see FIG. 14 (a) and FIG. 14 (b)). Corresponding to this, in the distribution of FIG. 15, an increase in the average momentum of the cosmic rays is observed in the vicinity of the position indicated by “C” in the drawing, and the width of the rising portion is the size of the cavity. It corresponds to. Thus, by examining the momentum of cosmic rays, it is possible to detect the existence of a cavity, estimate the position of the cavity, and estimate the size of the cavity. Even in such a case, in this embodiment and the modification, it is possible to avoid the situation where the amount of calculation becomes large and to quickly calculate the behavior of the cosmic rays.

C-5. Fifth modification:
In the above-described embodiments and modifications, the radiation detector is described as being arranged at a position after passing the substance (see FIG. 4). However, it may be installed at a position before passing through the substance. And when calculating the behavior of radiation, it is good also as what is calculated also in the position before passing a substance.

  FIG. 16 is an explanatory view exemplifying a state in which the radiation detector is arranged at a position before passing through the ground. As shown in the figure, in addition to the radiation detector (radiation detector indicated as radiation detector “X” in the figure) arranged on the ceiling of the tunnel, the radiation detector on the ground (radiation detector in the figure). A radiation detector indicated as “Y” is arranged.

  In this modification, the physical quantity of cosmic rays incident on the radiation detector “Y” is also acquired. Here, a case where the number of cosmic rays flying from each direction is obtained will be described as an example, but other physical quantities may be used. The number of incoming cosmic rays may be acquired by any method, for example, a table in which the number of incoming flights is set in advance may be acquired. Alternatively, a probability density function may be prepared and acquired from there.

  Further, when the incident direction is determined in this modification, the direction in which the radiation is incident may be determined by various methods as in the above-described embodiment. For example, in the case of a cosmic ray, since it pours from all directions, cosmic rays pour from any direction indicated by “A” to “D” in FIG. 16, so any direction may be determined as the incident direction. . In this modification, the description will be made assuming that the direction connecting two radiation detectors is determined as the incident direction.

  When the radiation detectors are arranged before and after the substance in this way, the change before and after passing can be estimated, so that the structure can be examined with higher accuracy. For example, by comparing the number of cosmic rays coming from the radiation detector “Y” with the number of cosmic rays coming from the radiation detector “X”, the radiation detector “X” and the radiation detector “Y” are compared. It is possible to more accurately grasp the number of cosmic rays that have stopped between the two and, in turn, grasp the structure between the radiation detector “X” and the radiation detector “Y” in more detail. Is possible.

  In such a case, it may be necessary to calculate in advance what the measurement result of the radiation detector “X” and the measurement result of the radiation detector “Y” will be. Therefore, in this modification, the direction connecting the radiation detector and the radiation detector is set as the incident direction, and the configuration information of the substance is acquired along that direction. As in the previous embodiment, the behavior when the cosmic rays pass through the substance corresponding to the configuration information is acquired, and the distribution for the incident direction is acquired by synthesizing the acquisition results for each incident direction. To do. By doing so, it is possible to avoid a situation in which the amount of calculation becomes large as in the above-described embodiment. In addition, the behavior of cosmic rays when passing through the substance between the radiation detectors can be accurately calculated by a method such as Monte Carlo simulation. As a result, even when the behavior of cosmic rays is calculated before and after passing through such a substance, it is possible to calculate quickly and accurately.

  As mentioned above, although the simulation system of a present Example and the modification was demonstrated, this invention is not restricted to the Example and the modification mentioned above, In the range which does not deviate from the meaning, it is possible to implement in various aspects. . For example, in the above-described embodiments and modifications, cosmic rays have been described as an example of radiation. However, any radiation (elementary particle) may be used as long as it is radiation that is not limited to cosmic rays but is emitted from a plurality of directions. Even so, the present invention is applicable. For example, the above-described contents can be applied to a situation where gamma rays come from all sides. Similarly, it can be applied to the situation where neutrons fly.

DESCRIPTION OF SYMBOLS 10 ... Simulation system 100 ... Server apparatus 104 ... Disk apparatus 200 ... Computer terminal apparatus 300 ... Mobile phone

Claims (6)

A radiation calculation device that calculates a physical quantity of radiation after passing through the material for radiation incident on the material from a plurality of directions,
Substance information storage means for storing the composition and geometric structure of the substance;
Physical quantity calculation position storage means for storing a physical quantity calculation position which is a position where the physical quantity of the radiation is calculated;
An incident direction determining means for determining an incident direction of the radiation to the physical quantity calculation position;
Incident direction substance information acquisition means for acquiring composition and geometric structure information of the substance along the incident direction from the physical quantity calculation position;
Behavior information acquisition means for acquiring behavior information when radiation passes through the substance having the acquired composition and geometric structure;
A physical quantity calculation unit comprising: physical quantity calculation means for calculating the physical quantity of the radiation from a plurality of directions at the physical quantity calculation position based on the behavior information for a plurality of the incident directions. The radiation calculation apparatus according to claim 1,
Second physical quantity calculation position storage means for storing a second physical quantity calculation position which is a position different from the physical quantity calculation position;
The substance information storage means is means for storing the composition and geometric structure of the substance between the physical quantity calculation position and the second physical quantity calculation position,
The incident direction determining means is means for determining a direction connecting the second physical quantity calculation position and the physical quantity calculation position;
The behavior information acquisition means is means for acquiring second behavior information as behavior information of radiation incident on the second physical quantity calculation position from the incident direction, and the behavior information.
The physical quantity calculation means is a radiation calculation apparatus which is a means for calculating a difference between the second behavior information and the behavior information. The radiation calculation apparatus according to claim 1 or 2,
The behavior information acquisition means is means for acquiring information regarding the frequency of radiation passing through the substance having the acquired composition and geometric structure,
The physical quantity calculation means is a radiation calculation apparatus which is a means for calculating the frequency of arrival of the radiation in the incident direction at the physical quantity calculation position based on the information on the frequency. The radiation calculation apparatus according to claim 1, wherein
The behavior information acquisition means is means for acquiring information regarding a deviation between the incident direction and the traveling direction of the radiation after passing through the substance having the acquired composition and geometric structure,
The physical quantity calculation means is a radiation calculation apparatus which is a means for calculating an incident angle of the radiation at the physical quantity calculation position based on the information regarding the deviation. A radiation calculation method for calculating a physical quantity of the radiation after passing through the substance with respect to radiation incident on the substance from a plurality of directions,
A substance information storing step for storing the composition and geometric structure of the substance;
A physical quantity calculation position storing step for storing a physical quantity calculation position which is a position where the physical quantity of the radiation is calculated;
An incident direction determining step for determining an incident direction of the radiation to the physical quantity calculation position;
Incident direction material information acquisition step for acquiring information of the composition and geometric structure of the material along the incident direction from the physical quantity calculation position;
A behavior information acquisition step of acquiring behavior information when radiation passes through the substance having the acquired composition and geometric structure;
A physical quantity calculation step comprising: calculating a physical quantity of the radiation from a plurality of directions at the physical quantity calculation position based on the behavior information for a plurality of incident directions. A program for realizing, using a computer, a radiation calculation method for calculating a physical quantity of radiation after passing through the material for radiation incident on the material from a plurality of directions,
A function (A) for storing the composition and geometric structure of the substance;
A function (B) for storing a physical quantity calculation position which is a position where the physical quantity of the radiation is calculated;
A function (C) for determining an incident direction of the radiation to the physical quantity calculation position;
A function (D) for acquiring information on the composition and geometric structure of the substance along the incident direction from the physical quantity calculation position;
A function (E) for obtaining behavior information when radiation passes through the substance having the obtained composition and geometric structure;
A function for realizing, by a computer, a function (F) for calculating the physical quantity of the radiation from a plurality of directions at the physical quantity calculation position based on the behavior information for a plurality of incident directions.

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