JP2019190857A - Position detector - Google Patents

Abstract

To provide a position detector which can detect radiation or excitation light in a wide range and can be increased in size.SOLUTION: A position detector 10 includes a phosphor that emits fluorescent light A by being excited by radiation 9 or excitation light 9. The position detector includes a medium 1 extending in the first direction y, spectral intensity measurement means 3 which is optically connected to the medium 1 and measures spectral intensity of fluorescent light A propagated through the medium 1, and arithmetic means 4 which determines the incident position of the radiation 9 or the excitation light 9 based on the spectral intensity. The arithmetic means 4 quantifies the spectral intensity distribution from the spectral intensity and determines the coordinate L in the first direction of the incident position from the quantified spectral intensity distribution based on the corresponding relationship between the spectral intensity distribution of the fluorescent light A and the propagation distance of the fluorescent light A.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a position detector, and more particularly to a position detector that determines the incident position of radiation or excitation light that excites a phosphor by measuring fluorescence emitted from the phosphor.

  Conventionally, a position detector for detecting the position of a point where radiation is incident has been put into practical use. For example, Non-Patent Document 1 describes the principle of position detection in a charge-division type position detector. The element described in Non-Patent Document 1 is configured by disposing a resistive electrode on the surface of a semiconductor material such as Si.

The operating principle is as follows. When visible light or radiation (for example, γ rays or charged particles) is incident on one point of the element, electron-hole pairs are generated inside the semiconductor material (photoelectric conversion), and these charges are collected by the electrodes. . This electric charge is divided into two by a resistive electrode and converted into an electric signal by an external circuit connected to the end of the electrode. The output signal of the external circuit is proportional to the amount of charge generated by photoelectric conversion. This output signal is also proportional to the ratio (R _x / R in FIG. 1 of Non-Patent Document 1) to the total resistance value from the light incident point to the end of the electrode. Therefore, the position of the light incident point can be determined from the obtained output signal.

  Patent Document 1 proposes a radiation monitor system using an optical fiber. In the radiation monitor system of Patent Document 1, a plurality of optical waveguide scintillators are connected in series or in parallel with an optical fiber, and an output signal thereof is guided to a data processing device. The radiation incident on the optical waveguide scintillator is converted into light, and pulsed light propagates simultaneously in two directions. These lights reach the data processing device through their respective paths. The data processor measures the time difference between the arrival of two light signals. Since the length of the optical fiber is known, the optical waveguide scintillator into which the radiation has entered can be determined from this time difference. FIG. 3 of Patent Document 1 is an example in which signals from a plurality of optical waveguide scintillators are plotted with the horizontal axis as time. In section [a, b] shown in FIG. 3 of Patent Document 1, since the output of one optical waveguide scintillator is separated, by calculating the area of the hatched portion in the figure, the corresponding location is obtained. Radiation dose can be determined. In the section [b, d], signals from two optical waveguide scintillators are superimposed. By obtaining the area of the hatched portion in the figure, the two are separated to determine the radiation dose at each location. can do.

JP-A-9-2111138

Satoshi Nakamoto, Katsuaki Nagata, Jun Kikuchi, Tadayoshi Michiya, “Position Sensitive Detector Using Semiconductor”, Applied Physics, Vol. 87-91 (1975)

  The problem of the position detector of Non-Patent Document 1 will be described. Since semiconductor materials are generally expensive, it is difficult in principle to lengthen the position detector (in the case of a two-dimensional position detector, increase the area) in the conventional charge division method.

  The problem of the radiation monitor system of Patent Document 1 will be described. First, the place where the radiation dose can be measured is limited to the place where the optical waveguide scintillator is placed. For example, if it is arranged at three places, only three places can be measured, and the radiation dose cannot be measured at a point in between. Therefore, in order to measure the radiation dose with high spatial resolution, it is necessary to arrange a plurality of optical waveguide scintillators at high density. However, in such a case, mutual output signals are superimposed in the optical fiber, making it difficult to identify individual output signals. Second, it is necessary to arrange the optical fibers in a loop. If this is not necessary, the degree of freedom in laying the optical fiber is increased. For example, instead of the parallel connection shown in FIG. 2 of Patent Document 1, if a plurality of optical fibers can be arranged radially and guided to the processing apparatus, a region where radiation should be measured can be freely set. it can.

  An object of the present invention is to provide a position detector that can be enlarged and can detect radiation or excitation light in a wide range.

  The present invention for achieving the above object includes the following embodiments, for example.

(Claim 1)
A first medium that includes a first phosphor that emits first fluorescence when excited by radiation or excitation light, and extends in a first direction;
Spectral intensity measuring means optically connected to the first medium and measuring the spectral intensity of the first fluorescence propagated in the first medium;
Calculating means for determining an incident position of the radiation or excitation light based on the spectral intensity,
The calculation means quantifies the spectral intensity distribution from the spectral intensity, and based on the correspondence relationship between the spectral intensity distribution of the first fluorescence and the propagation distance of the first fluorescence, from the quantified spectral intensity distribution A position detector for determining coordinates of the incident position in the first direction.

(Section 2)
Further comprising a first optical waveguide;
Item 2. The position detector according to Item 1, wherein the spectral intensity measuring means is optically connected to the first medium via the first optical waveguide.

(Section 3)
A pair of second optical waveguides optically connected to opposing regions of the first medium along a second direction intersecting the first direction;
Fluorescence intensity measuring means connected to the second optical waveguide and measuring the intensity of the first fluorescence incident on the pair of second optical waveguides, respectively.
The calculation means determines coordinates of the incident position in the second direction based on a ratio of the intensity of the first fluorescence measured by the fluorescence intensity measurement means, Item 1 or 2 The position detector as described in.

(Claim 4)
A second phosphor that emits second fluorescence when excited by radiation or excitation light, and is connected to the first medium and extends in a second direction intersecting the first direction Further comprising a medium,
The second fluorescence has higher energy than the first fluorescence,
Item 3. The position detector according to Item 1 or 2, wherein the first phosphor emits the first fluorescence when excited by the second fluorescence.

(Section 5)
Item 5. The position detector according to Item 4, wherein the first fluorescence has a wavelength longer than that of the second fluorescence.

(Claim 6)
The computing means calculates the fluorescence intensity by integrating the spectral intensity distribution, and calculates the intensity of the radiation or excitation light based on the correspondence between the fluorescence intensity and the coordinates of the incident position. The position detector according to any one of Items 1 to 5.

  According to the present invention, it is possible to provide a position detector that can be enlarged and can detect radiation or excitation light in a wide range.

It is the schematic which shows the structure of the position detector which concerns on the 1st Embodiment of this invention. It is a partial schematic diagram of a position detector for explaining the principle of position detection. It is the schematic which shows the structure used for the verification experiment of a position detection principle. It is a graph of the fluorescence spectral intensity distribution observed on the end face of the fluorescent substrate when the incident point of the laser beam is changed. It is the graph which normalized the spectral intensity distribution of FIG. 4 with the data of the wavelength which can disregard self-absorption. FIG. 5 is a graph showing the fluorescence intensity obtained by integrating the spectral intensity distribution of FIG. 4 with the wavelength and shown as a function of the position (coordinate) of the incident point. 5 is a graph of chromaticity coordinates (CIE-XYZ color system) calculated from the spectral intensity distribution of FIG. 4. It is a graph which shows the same data as FIG. 7 which shows the relationship between chromaticity coordinates and distance as a function of distance. It is a graph which shows the relationship between the index | index of the red shift calculated from chromaticity coordinates, and the position of an incident point, and is an example which calculated the function x / y as an example, and plotted as a function of distance L. It is the schematic which shows the structure of the position detector which concerns on the 2nd Embodiment of this invention. It is the schematic which shows the structure of the position detector which concerns on the 3rd Embodiment of this invention. It is the schematic which shows the structure of the monitor system which concerns on the 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and drawings, the same reference numerals indicate the same or similar components, and therefore, duplicate descriptions of the same or similar components are omitted.

  In this specification, radiation is a general term for high-energy substance particles and high-energy electromagnetic waves. High energy material particles mean, for example, particle radiation such as alpha rays, beta rays (electron rays or positron rays), neutron rays, charged particle rays, and meson rays. High-energy electromagnetic waves mean electromagnetic radiation such as gamma rays and X-rays, for example.

  In this specification, the excitation light means light that excites a fluorescent substance such as a phosphor. Exemplary excitation light includes, for example, visible light, X-rays, and ultraviolet light.

The position detector according to the present invention described below is characterized in that the position of the incident point of radiation or excitation light is obtained by quantifying the red shift of the spectral intensity distribution of fluorescence. Furthermore, the position detector according to the present invention is characterized in that a wide range of position detection can be realized at low cost by using a fluorescent material, a transparent medium or the like instead of an expensive semiconductor material. In the position detector according to the present invention, a power source is not required for the configuration of the part for detecting radiation or excitation light, and an optical waveguide that does not require a power source is also required from this detecting part to the part for measuring fluorescence intensity. Connected. As a result, the configuration up to the part that measures the fluorescence intensity can be made into an all-optical configuration, and the part that detects radiation or excitation light can be placed away from the part that measures the fluorescence intensity that requires a power source. It becomes possible to install. Therefore, the position detector according to the present invention can realize installation and operation in a severe environment.
[First Embodiment]

  FIG. 1 is a schematic diagram showing a configuration of a position detector according to the first embodiment of the present invention. According to a first embodiment, a one-dimensional position detector is provided.

  The position detector 10 according to the first embodiment of the present invention includes a medium 1 including a phosphor and extending in a first direction (y-axis direction in the drawing), and a spectral intensity measuring means 3 for measuring the spectral intensity of the fluorescence. And calculating means 4 for determining the incident position of the radiation 9 (or excitation light 9) based on the spectral intensity.

  In the configuration illustrated in FIG. 1, the optical waveguide 2 is connected between the end face of the medium 1 and the spectral intensity measuring means 3, and the spectral intensity measuring means 3 is optically connected to the medium 1 via the optical waveguide 2. It is connected.

  The phosphor is uniformly dispersed in the medium 1. The phosphor emits fluorescence A when excited by radiation 9 (or excitation light 9). As the medium 1, for example, a transparent substrate containing a scintillation substance can be used, and, for example, a plastic scintillator can be used. For example, an optical fiber can be used for the optical waveguide 2.

  The spectral intensity measuring means 3 is optically connected to the medium 1 and measures the spectral intensity of the fluorescence A propagated in the medium 1. The measured spectral intensity is transmitted to the calculation means 4. As the spectral intensity measuring means 3, for example, a spectroscope can be used.

  The computing means 4 quantifies the spectral intensity distribution from the spectral intensity, and determines the coordinate L in the first direction of the incident position from the quantified spectral intensity distribution. The coordinates are determined based on the correspondence between the spectral intensity distribution of the fluorescence A and the propagation distance of the fluorescence A. The correspondence between the fluorescence spectral intensity distribution and the propagation distance L will be described later. As the calculation means 4, for example, a known calculation circuit or a personal computer can be used.

  In the following description, the medium 1 containing a phosphor is also simply referred to as a transparent substrate 1. Similarly, the optical waveguide 2 is also simply referred to as the optical fiber 2, and the spectral intensity measuring means 3 is also simply referred to as the spectroscope 3.

Outline of Position Detection Principle An outline of the position detection principle will be described with reference to FIG. When the radiation 9 is incident on the medium 1 from the outside and the phosphor contained in the medium 1 absorbs the radiation 9, the fluorescence A is emitted isotropically. Some fluorescence propagates through the medium 1 and the optical waveguide 2 to reach the spectroscope 3, and the spectroscope 3 measures the spectral intensity distribution. The spectral intensity distribution output from the spectroscope 3 changes depending on the position of the incident point of the radiation 9. This is due to a phenomenon called self-absorption. That is, while the fluorescence propagates through the medium 1, a part of the fluorescence is absorbed by the phosphor itself. The intensity of the absorbed fluorescence depends on the wavelength. Fluorescence with a short wavelength is well absorbed, and there is almost no absorption of fluorescence with a long wavelength. Such a change in spectral intensity distribution is called red shift or red shift. The amount of red shift increases as the distance that the fluorescence propagates increases. Therefore, the incident position of the radiation 9 can be determined by appropriately quantifying the red shift. For example, since the chromaticity coordinates calculated from the spectral intensity distribution correspond one-to-one with the incident position of the radiation 9, the position of the incident point of the radiation 9 can be determined from the chromaticity coordinates.

  Furthermore, in addition to the incident position of the radiation 9, the intensity of the incident radiation 9 can be obtained. This can be done even when the intensity of the incident radiation 9 is unknown. For this purpose, it is preferable to carry out the calibration work described below in advance.

  First, radiation having a known intensity is incident on the medium 1 and the spectral intensity distribution of fluorescence is recorded. This is integrated by wavelength to obtain fluorescence intensity. Next, the position (coordinate) of the incident point is changed and the above operation is repeated to obtain the correspondence between the position (coordinate) of the incident point and the fluorescence intensity. Since this is generally a curve, it is called a calibration curve.

  In order to obtain the intensity of radiation, (1) the red shift of the spectral intensity distribution is quantified to obtain the position (coordinates) of the incident point, (2) the fluorescent intensity is obtained by integrating the spectral intensity distribution, ( 3) The procedure of (1) to (3) is executed in which the fluorescence intensity is converted into the radiation intensity using the calibration curve. This calibration operation need not be repeated unless the characteristics of the elements constituting the position detector 10 change.

  The detailed contents of the principle described above will be specifically described with numerical examples.

FIG. 2 is a partial schematic diagram of a position detector for explaining the principle of position detection. As a configuration of the position detector 10, a transparent substrate containing a phosphor is used as the medium 1. A partial cross section of a configuration in which an optical fiber is used for the optical waveguide 2 is shown. In the figure, the x-axis is perpendicular to the paper surface, and the x-axis direction is the direction from the paper surface toward the front.

  As shown in FIG. 2, the core of the optical fiber 2 (optical waveguide 2) is brought into close contact with the end face of the transparent substrate 1 (medium 1) in which the phosphor is uniformly dispersed, and the fluorescence emitted from the phosphor is dispersed. Consider the configuration leading to vessel 3. It is assumed that the radiation 9 is perpendicularly incident on the transparent substrate 1 and fluorescence is emitted isotropically from a point with coordinates y = L and z = 0. At this time, the fluorescence that propagates through the optical fiber 2 and reaches the spectroscope 3 is only the fluorescence that propagates at an angle smaller than the angle θ determined by the numerical aperture NA of the optical fiber.

When the refractive indexes of the core and the clad of the optical fiber 2 are n ₁ and n ₂ , respectively, the numerical aperture NA is
Given in. When the refractive index of the transparent substrate 1 is n and the maximum value of θ in FIG. 2 is θ _max , Snell's law
It becomes.

On the other hand, the angle θ _geo where the fluorescence emitted from the point of coordinates y = L and z = 0 looks into the core of the optical fiber 2 is determined by geometric conditions. When the diameter of the core of the optical fiber 2 is D, the following equation is established.

Here, the condition that light that reaches the core of the optical fiber 2 always propagates through the optical fiber 2 is θ _geo ≦ θ _max ,
Can be written. When this is rearranged, the following inequality is obtained.

For example, when NA = 0.22 and n ₁ = n = 1.5,
It becomes. Further, when D = 0.4 mm, all the light from the light emission point of L> 1.38 mm is guided to the spectrometer 3.

When the condition of Expression (3) is satisfied, the probability P _det that the light emitted isotropically from the light emitting point propagates through the optical fiber 2 and reaches the spectroscope 3 is 2θ _geo / 2π. That is,

Next, the spectral intensity distribution of fluorescence will be considered. Let S ₀ (λ) be the spectral intensity distribution of fluorescence generated at coordinates y = L and z = 0. The fluorescence emitted at the angle θ propagates the distance (L−y) / cos θ inside the transparent substrate 1 and reaches the coordinate x. Assuming that the absorption coefficient of the material constituting the transparent substrate 1 with respect to light of wavelength λ is μ (λ), the spectral intensity distribution S (y, θ, λ) at the coordinate y is expressed by the following equation according to Lambert-Beer's law. Represented in the street.

In the case of D / L << 1, the angle θ is sufficiently small and can be approximated as cos θ≈1. At this time, the probability P _det that the light radiated from the light emitting point isotropically reaches the spectroscope 3 and the spectral intensity distribution S of the detected fluorescence are expressed by the following equations from equations (4) and (5), respectively. Approximate to the street.

  FIG. 3 is a schematic diagram showing a configuration used in a verification experiment of the position detection principle. In the demonstration experiment, a fluorescent substrate made of acrylic resin (about 5 cm × 5 cm × 0.5 cm, manufactured by Nitto Resin Co., Ltd., model number F-604) is used as the transparent substrate 1, and the wavelength of 450 nm is used as excitation light for exciting the phosphor. Laser light was used. Using a laser 91 and a mirror 92, laser light was vertically incident on one point of the fluorescent substrate, and fluorescence reaching the end face of the fluorescent substrate was guided to the spectroscope 3 by the optical fiber 2.

  The spectral intensity distribution was recorded by moving the incident point of the laser light along the y-axis in the figure. An example of the results is shown in FIG. FIG. 4 is a graph of the spectral intensity distribution of fluorescence observed on the end face of the fluorescent substrate when the incident point of the laser beam is changed. The data plots the results when the incident point was changed in steps of 2 mm from y = 2 mm to 20 mm. Referring to FIG. 4, it can be confirmed that the spectral intensity decreases as the incident point moves away from the end face, and that the reduction amount is particularly remarkable on the short wavelength side (that is, red shift occurs). it can.

  FIG. 5 is a graph obtained by normalizing the spectral intensity distribution of FIG. 4 with data of a wavelength at which self-absorption can be ignored. The wavelength at which self-absorption can be ignored is 650 nm in this example. Referring to FIG. 5, the red shift can be observed more clearly. It can be seen that, as the incident point moves away from the end face and the distance increases from y = 2 mm to 20 mm, the peak wavelength position shifts to the right side (that is, the long wavelength side) in the graph.

  FIG. 6 is a graph showing the fluorescence intensity obtained by integrating the spectral intensity distribution of FIG. 4 with the wavelength, and shown as a function of the position (coordinates) of the incident point. Similar to FIG. 4, the data is plotted in 2 mm steps from y = 2 mm to 20 mm. The curve in the figure is a theoretical formula according to the formula (6), and it can be confirmed that the experimental result well reproduces the theoretical formula.

  In FIG. 6, the vertical axis is an arbitrary unit, but instead, the intensity of incident light is measured in advance with a power meter or the like, and the unit of the vertical axis is the light intensity. It can also be set to W (watt) which is a unit of. This calibration operation does not need to be repeated unless the component characteristics change.

  Next, red shift quantification will be described. If the dependence of the red shift on the fluorescence intensity is eliminated in advance, the position can be determined stably even if the intensity of the incident light changes. For example, this can be realized by the standardization process described above. For example, in the normalized spectral intensity distribution graph, the wavelength at which the normalized spectral intensity has a specific value (eg, 30 in the example shown in FIG. 5) is obtained from the graph and used as a red shift index. . Since the wavelength obtained from this graph has a one-to-one correspondence with the coordinates L of the incident point, the coordinates L of the incident point can be obtained from the detected spectral intensity distribution.

  The red shift quantification method is not limited to this. It can also be obtained by calculation rather than using a graph. For example, chromaticity coordinates can be calculated and associated with the incident point coordinates L to form a calibration curve. As an example, FIG. 7 shows the result of executing this calculation using the color matching function (2 ° field of view) of the CIE1931-XYZ color system.

  FIG. 7 is a graph of chromaticity coordinates (CIE-XYZ color system) calculated from the spectral intensity distribution of FIG. Similar to FIG. 4, the data is plotted in 2 mm steps from y = 2 mm to 20 mm. In the graph of FIG. 7, x and y shown on the horizontal and vertical axes mean chromaticity coordinates calculated from the measured spectral intensity distribution of fluorescence. Referring to FIG. 7, it can be seen that the chromaticity coordinates (x, y) move to the right side (that is, to the red region) on the chromaticity diagram as the distance L between the incident point and the end face increases. In the example shown in FIG. 7, the chromaticity coordinate x has a one-to-one correspondence with the distance L among the chromaticity coordinates x and y. FIG. 8 is a graph showing the same data as FIG. 7 as a function of distance, showing the relationship between chromaticity coordinates and distance. For example, the distance L can be determined from the chromaticity coordinates x by using the curve represented by the plot shown in the graph of FIG. 8 as the calibration curve.

  Furthermore, a function that increases or decreases monotonously with the distance L can be used as an index of red shift. FIG. 9 is a graph showing the relationship between the index of the red shift calculated from the chromaticity coordinates and the position of the incident point. As an example, the function x / y is calculated and plotted as a function of the distance L. Here, x and y of the function x / y mean chromaticity coordinates. In the example shown in FIG. 9, the calibration curve can be well approximated by a linear expression. If the calibration curve can be expressed by a linear expression, the coordinates L of the incident point can be obtained from the spectral intensity distribution by, for example, data processing by the computing means 4 provided with a CPU.

  As described above, according to the position detector 10 according to the first embodiment of the present invention, it is possible to improve the spatial resolution and increase the length. By using a fluorescent material or a transparent medium instead of an expensive semiconductor material, a wide range of position detection can be realized at low cost.

  Further, the medium 1 for detecting the radiation 9 (or excitation light 9) does not require a power source, and the medium 1 to the spectroscope 3 are also connected by the optical waveguide 2 that does not require a power source. Thereby, the spectroscope 3 and the calculation means 4 that require a power source can be arranged at a location away from the installation location of the medium 1. Thereby, the position detector 10 can implement | achieve installation and operation | movement in a severe environment.

[Second Embodiment]
FIG. 10 is a schematic diagram showing a configuration of a position detector according to the second embodiment of the present invention. According to a second embodiment, a two-dimensional position detector is provided.

  According to the position detector 10 according to the first embodiment shown in FIG. 1, the y coordinate of the position where the radiation 9 is incident can be detected, but the x coordinate cannot be detected. According to the position detector 20 according to the second embodiment shown in FIG. 10, it is possible to detect the x coordinate and the y coordinate of the position where the radiation 9 is incident. In the second embodiment, detection of the y coordinate is performed based on the correspondence relationship between the spectral intensity distribution of fluorescence and the propagation distance of fluorescence, as in the first embodiment, and detection of the x coordinate is described below. This is done according to the principle of light quantity division.

  As shown in FIG. 10, the position detector 20 according to the second embodiment of the present invention includes a pair of optical waveguides 5 (5A, 5B) in addition to the position detector 10 according to the first embodiment. Fluorescence intensity measuring means 6 (6A, 6B) is further provided.

  The pair of optical waveguides 5A and 5B are optically disposed in a region facing the medium 1 along a second direction (x-axis direction in the drawing) that intersects the first direction (y-axis direction in the drawing). Connected. For example, an optical fiber can be used for the optical waveguides 5A and 5B.

  The fluorescence intensity measuring means 6A and 6B are connected to the optical waveguides 5A and 5B, and measure the intensity of the fluorescence A incident on the pair of optical waveguides 5A and 5B, respectively. The measured fluorescence intensity is transmitted to the calculation means 4. For the fluorescence intensity measuring means 6A, 6B, for example, a photodetector such as a photodiode can be used. Signal processing circuits such as amplifiers and analog / digital converters can be appropriately connected to the fluorescence intensity measuring means 6A and 6B.

  The computing means 4 determines the coordinates of the incident position in the second direction based on the ratio of the intensity of the fluorescence A measured by the fluorescence intensity measuring means 6A, 6B.

As the distance between the light emitting point and the end face of the medium 1 is smaller, the probability that the fluorescence A propagates into the optical waveguides 5A and 5B increases. Accordingly, if the respective outputs of the fluorescence intensity measuring means 6A and 6B are I ₁ and I ₂ , the ratio of the fluorescence intensity
Or
Is proportional to the x coordinate of the incident point of the radiation 9. The y-coordinate can be determined by guiding the fluorescence A to the spectroscope 3 by the optical waveguide 2 in the same manner as in the configuration of FIG. 1, so that the two-dimensional coordinate can be detected. Note that such an x-coordinate position detection technique is based on the ratio of the amount of light reaching the pair of optical waveguides 5A and 5B, and thus the principle can be referred to as “light amount division”.

  As described above, according to the position detector 20 according to the second embodiment of the present invention, it is possible to improve the spatial resolution and increase the area.

[Third Embodiment]
FIG. 11 is a schematic diagram showing a configuration of a position detector according to the third embodiment of the present invention. According to the third embodiment, a highly sensitive position detector is provided.

  In the position detector 10 according to the first embodiment shown in FIG. 1, the radiation 9 enters the medium 1 and the fluorescence A propagates through the optical waveguide 2. The medium 1 and the optical waveguide 2 are optically connected. However, when the area of the connection surface of the optical waveguide 2 is smaller than the area of the connection surface of the medium 1 as shown in FIG. The amount of fluorescence A to be reduced decreases, and the sensitivity of the position detector 10 decreases. On the other hand, if the area of the connection surface of the medium 1 is equal to the area of the connection surface of the optical waveguide 2, the area of the medium 1 on which the radiation 9 is incident is reduced. In this case, the sensitivity of the position detector 10 is also reduced. descend. According to the position detector 30 according to the third embodiment shown in FIG. 11, the sensitive area of the position detector is enlarged using the second medium containing the second phosphor.

  As shown in FIG. 11, the position detector 30 according to the third embodiment of the present invention includes a second phosphor in addition to the position detector 10 according to the first embodiment, and is optically applied to the medium 1. And a second medium 7 that is connected to each other and extends in a second direction (x-axis direction in the drawing) that intersects the first direction (y-axis direction in the drawing).

  The second phosphor is uniformly dispersed in the second medium 7. The second phosphor emits fluorescence B by being excited by the radiation 9 (or excitation light 9). As the second medium 7, for example, a transparent substrate containing a scintillation substance can be used, and, for example, a plastic scintillator can be used.

  When the radiation 9 enters the medium 7 having a large area including the second phosphor, the fluorescence B emitted from the second phosphor propagates inside the second medium 7 and enters the medium 1. A phosphor is present inside the medium 1, which absorbs the fluorescence B and emits the fluorescence A having lower energy than the fluorescence B. The fluorescence A propagates inside the medium 1 and reaches the spectroscope 3 through the optical waveguide 2. With this configuration, the sensitive area of the position detector 30 is increased, and high sensitivity of the position detector is realized.

  When the radiation 9 is high-energy electromagnetic waves, that is, X-rays or γ-rays, in order to increase the absorption probability of the radiation 9, for example, a phosphor containing an element with a large atomic number such as CsI or NaI ( A scintillator) is preferably used as the second medium 7. On the other hand, the wavelength of the fluorescence emitted by these materials is not necessarily a wavelength with small absorption by the optical fiber. Therefore, when the optical fiber 2 is used as the optical waveguide 2 and long-distance light transmission is performed, the fluorescence B radiated from the second medium 7 functioning as a scintillator is converted into the phosphor contained in the medium 1. Therefore, it is desirable to convert to fluorescence A having a longer wavelength.

  As described above, according to the position detector 30 according to the third embodiment of the present invention, the sensitive region of the position detector can be increased, and high sensitivity of the position detector can be realized.

[Fourth Embodiment]
FIG. 12 is a schematic diagram showing a configuration of a monitor system according to the fourth embodiment of the present invention. According to a fourth embodiment, a radiation monitor system is provided.

  The position detector monitoring system 40 according to the fourth embodiment of the present invention is characterized in that the position detector 10 according to the first embodiment shown in FIG. 1 includes the optical waveguide 2 (optical fiber 2). . In the monitor system 40 according to the fourth embodiment, the position detector includes a plurality of media 1A, 1B, 1C and a plurality of optical waveguides 2A, 2B, 2C. An optical switch (not shown) is disposed between the plurality of optical waveguides 2A, 2B, and 2C and the spectroscope 3, and the plurality of optical waveguides 2A, 2B, and 2C are single via the optical switch. Optically connected to the spectroscope 3.

  In the monitor system 40 according to the fourth embodiment, the coordinates in the first direction of the incident position of each radiation 9 (or excitation light 9) incident on each of the mediums 1A, 1B, and 1C including the phosphor are detected. The operation is the same as that of the position detector 10 according to the first embodiment. The optical switch switches the fluorescence A propagating from the respective media 1A, 1B, and 1C in a time division manner and sends the fluorescence A to the spectroscope 3. As in the case of the position detector 10 according to the first embodiment, the calculation means 4 is configured to receive each radiation incident on each medium 1A, 1B, 1C based on the measured value of the spectral intensity from the spectrometer 3. 9 incident positions are output.

  As described above, according to the monitor system 40 using the position detector according to the fourth embodiment of the present invention, it is possible to measure and monitor the radiation dose with high spatial resolution in a wide area.

[The invention's effect]
According to the configuration and the principle of position detection of the present invention described above, it is possible to improve the spatial resolution of the position detector and increase the length or area. Furthermore, according to the radiation monitoring system using the principle of position detection and the optical waveguide of the present invention, it is possible to measure and monitor the radiation dose with high spatial resolution in a wide area.

  According to the position detector according to the present invention, since a relatively inexpensive material such as a transparent medium containing a phosphor is used instead of an expensive semiconductor material, a large position detector can be manufactured at low cost. . The configuration of the portion for detecting radiation or excitation light does not require a power source, and the portion from this detection portion to the portion for measuring fluorescence intensity is also connected by an optical waveguide that does not require a power source. Thereby, the position detector according to the present invention can realize installation and operation in a severe environment such as underwater or in the vicinity of a nuclear reactor.

  In addition, according to the monitor system of the present invention, since the coordinates of the position where the radiation is incident can be detected, radiation detection at a line or surface is possible instead of radiation detection at a conventional point. Further, since the operation is performed with the fluorescence output from one side of the medium (transparent substrate) functioning as the detection unit, it is not necessary to connect the detectors in a loop shape as in the prior art. Since the detectors can be connected in series, a large area can be monitored.

  A position detector using a semiconductor material is used for automation of work at a manufacturing site such as a factory (Factory Automation) and control of various machines. The position detector according to the present invention can replace the conventional position detector using such a semiconductor material.

  The monitor system according to the present invention can monitor an environmental radiation dose in a wide range including, for example, a building wall and the seabed at low cost, because it corresponds to a large area, has high detection accuracy, and has high environmental resistance. Therefore, for example, a large-scale radiation monitor that has never been used for a large facility such as a chemical plant can be realized, which can contribute to the realization of a safe environment.

1 (1A, 1B, 1C) Medium (transparent substrate)
2 (2A, 2B, 2C) Optical waveguide (optical fiber)
3 Spectral intensity measurement means (spectrometer)
4 Calculation means 5 (5A, 5B) Optical waveguide 6 (6A, 6B) Fluorescence intensity measurement means 7 Second medium (transparent substrate)
9 Radiation (excitation light)
10, 20, 30, Position detector 40 Monitor system 91 Laser 92 Mirror A Fluorescence (first fluorescence)
B fluorescence (second fluorescence)

Claims (6)

A first medium that includes a first phosphor that emits first fluorescence when excited by radiation or excitation light, and extends in a first direction;
Spectral intensity measuring means optically connected to the first medium and measuring the spectral intensity of the first fluorescence propagated in the first medium;
Calculating means for determining an incident position of the radiation or excitation light based on the spectral intensity,
The calculation means quantifies the spectral intensity distribution from the spectral intensity, and based on the correspondence relationship between the spectral intensity distribution of the first fluorescence and the propagation distance of the first fluorescence, from the quantified spectral intensity distribution A position detector for determining coordinates of the incident position in the first direction. Further comprising a first optical waveguide;
The position detector according to claim 1, wherein the spectral intensity measurement unit is optically connected to the first medium via the first optical waveguide. A pair of second optical waveguides optically connected to opposing regions of the first medium along a second direction intersecting the first direction;
Fluorescence intensity measuring means connected to the second optical waveguide and measuring the intensity of the first fluorescence incident on the pair of second optical waveguides, respectively.
The calculation means determines coordinates of the incident position in the second direction based on a ratio of the intensity of the first fluorescence measured by the fluorescence intensity measurement means. 2. The position detector according to 2. A second phosphor that emits second fluorescence when excited by radiation or excitation light, and is connected to the first medium and extends in a second direction intersecting the first direction Further comprising a medium,
The second fluorescence has higher energy than the first fluorescence,
The position detector according to claim 1, wherein the first phosphor emits the first fluorescence when excited by the second fluorescence.   The position detector according to claim 4, wherein the first fluorescence has a longer wavelength than the second fluorescence.   The computing means calculates the fluorescence intensity by integrating the spectral intensity distribution, and calculates the intensity of the radiation or excitation light based on the correspondence between the fluorescence intensity and the coordinates of the incident position. The position detector according to any one of claims 1 to 5.