JP2000258540A - Radiation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a radiation detector that allows two systems of photodetectors to minimize mutual influence and maximize detection efficiency in a wavelength-identification-type double-layer photodetector for discriminating particles. SOLUTION: A radiation detector is equipped with a first photodetector 4 that has a first color filter 3 for selectively extracting light from a first scintillator 1, and a second photodetector 6 that has a second color filter 5 for selectively extracting light from a second scintillator 2, and arrangement is made at a position where a direction for connecting the center of the first color filter 3 to that of the second one 5 is perpendicular to (b) or is slanted for (c) the longitudinal direction of the first and second scintillators 1 and 2 (b), and at the same time approach can be made.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength discrimination type or optical fiber transmission type radiation detector utilizing the scintillation principle and optical means.

[0002]

2. Description of the Related Art In recent years, various optical radiation sensor systems combining the scintillation principle and optical means have been developed. In such a sensor system, unlike a conventional scintillation probe, light propagation at a connection portion with a photodetector such as a photomultiplier tube (hereinafter, referred to as PMT), obstruction of light condensing action, and reflection of light are problematic. In many cases, there is a problem that an optimal system cannot be configured only by conventional common sense means in the arrangement and connection method of the PMT.

Next, a conventional example will be described with reference to FIGS. 8A and 8B are diagrams for explaining a conventional optical wavelength discrimination type radiation detector, in which FIG. 8A is a first conventional example, FIG. 8B is a second conventional example, and FIG. () Is a top view of (a) or (b).

That is, in FIG. 1A, a first scintillator 1 and a second scintillator 2 are vertically arranged in a two-layer structure. On the lower layer side of the second scintillator 2, the first scintillator 2
A first photodetector 4 having a color filter 3 and a second photodetector 6 having a second color filter 5 are arranged in close contact with each other.

[0005] The first color filter 3 has a function of transmitting light of the first scintillator 1 and absorbing light of the second scintillator 2. In addition, the second color filter 5
Has the function of transmitting the light of the second scintillator 2 and absorbing the light of the first scintillator 1.

In the second arrangement shown in FIG. 1B, the basic principle is the same as in the first arrangement, but the first scintillator 1
The first color filter 3 and the second color filter 5 do not directly adhere to the second scintillator 2 provided on the lower side of the light guide, but a light guide 9 is brought into close contact with the second scintillator 2 to collect light via the light guide 9. It is supposed to do.

In each of the first and second examples shown in FIGS. 1A and 1B, as a matter of course, outside light is shielded on the upper side of the first scintillator 1 and the target radiation is not emitted. It is equipped with a transmissive incident film and other necessary cases and electronic circuits, but they are not shown here.

For the first scintillator 1, it is necessary to consider capturing light radiated from the surface. The second scintillator 2 is based on the fact that the scintillator to be used is transparent to its own emission wavelength and the periphery thereof is uniformly optically polished and, when there is no close contact, has a higher refractive index than the surrounding air layer. The internal capture of light by reflection occurs. A general plate-shaped plastic scintillator is an example of this.

At this time, the light in the second scintillator 2 is diffused while being captured. For this reason, in addition to the light that is emitted near the second color filter 5 and is incident on the second color filter as direct light, the second color filter 5
Even when light emission occurs at a position distant from, there is a probability that the light will be incident on the second color filter 5 after being efficiently propagated.

Regarding the actual arrangement of the photodetectors, as shown in FIG. 3C, in order to obtain more direct light emitted from the surfaces of the first and second scintillators 1 and 2, it is preferable to use two light detectors.
It is often performed to center the light detection system of the system.

However, in the case of FIG. 8C, the first color filter 3 having the function of absorbing the light of the second scintillator 2 adjacent to the second scintillator 2 is closely attached to the second scintillator 2. I have. First color filter 3 and second color filter 3
Are arranged in parallel in the longitudinal direction of the detection surface, that is, the long side.

For this reason, for example, while light emitted on the left side of the detection surface in FIG. 8C propagates inside the second scintillator 2 to the position of the second color filter 5, there is a high probability. It can be foreseen that the light will pass and encounter the portion where the first color filter 3 is in contact, and will be absorbed there. For this reason, the detection efficiency in the left half decreases,
There is a problem that the uniformity of sensitivity is reduced.

FIG. 9 shows a conventional optical (optical fiber transmission type) radiation detector using a method of guiding an optical signal to a photodetector 15 using an optical fiber 10, wherein the optical fiber 10 is optically coupled. The state where it is connected to the light receiving surface 14 of the photodetector 15 via the material 12 is partially shown.

In many cases, PMT is used for the photodetector 15. In this case, the photocathode corresponding to the photodetection surface 14 is also glass, and the optical coupling material 12 such as optical grease is used.
The reflection at the boundary can be suppressed as long as the bonding is performed through the interface.

However, the layer following the photocathode is a vacuum layer, and large Fresnel reflection eventually occurs here. In particular, a component perpendicularly incident on the photocathode not only causes large Fresnel reflection, but also propagates in the optical fiber 10 in the opposite direction because the reflected light itself has an angle at which the reflected light itself can re-enter the optical fiber 10. This corresponds to a light amount loss when viewed from the photodetector 15 side, but may have a further adverse effect depending on the signal processing method.

FIG. 10 is a system diagram showing a radiation detector in which photodetectors 15 are connected to both ends of the optical fiber 10. In FIG. 10, a radiation sensor 16 is provided in the middle of the optical fiber 10, photodetectors 15 and 15 are connected to both ends of the optical fiber 10, and the output side of each photodetector 15 and 15 is connected to the data processing device 17. are doing.

There is also known an arrangement in which the core of the optical fiber 10 is doped with a substance emitting light by radiation, or a radiation sensor 16 for sending out a light pulse upon incidence of radiation is connected in the middle of the optical fiber 10.

In the data processing device 17, the photodetectors 15 at both ends are used.
From the time difference of the optical pulse detected in the from which position of the optical fiber 10 to identify the signal sent toward both ends,
The light emission position, that is, the incident position of the radiation is identified.

[0019]

SUMMARY OF THE INVENTION A photodetector as described above
When reflection occurs at the connection between the optical fiber 15 and the optical fiber 10, there is a possibility that the reflected pulse propagated in the opposite direction is captured by the other photodetector 15. This signal is erroneously recognized as a signal having the light emitting position at the end of the optical fiber 10. Since this erroneous signal has a different generation and influence depending on the intensity of the radiation to be measured and its distribution, there is no method of simply correcting and canceling the influence.

Therefore, in a radiation detector for measuring the difference in arrival time of a pulse as shown in FIG. 10, generation of such a reflected pulse is fatal, and from the viewpoint of ensuring measurement accuracy, the above-mentioned reflection pulse is generated. A method to prevent this was essential.

In the general field of optical communication, since reflected pulses do not pose a serious problem in data processing, measures are taken from the viewpoint of light loss. As an anti-reflection method, a method of processing an end face of an optical fiber such as spherical processing or oblique polishing of an end face or anti-reflection coating is generally put into practical use.

However, since the optical fiber 10 used in radiation measurement as described in FIG. 10 is a plastic fiber or a polymer cladding quartz core fiber having a large diameter, such a processing is applied. There is a problem that cannot be done and there is no simple and effective method.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. In a wavelength identification type optical radiation detector, uniform and high detection efficiency can be obtained by rational arrangement of photodetectors. In addition, in a radiation detector of an optical fiber transmission type, to provide a radiation detector capable of suppressing occurrence of an erroneous signal due to Fresnel reflected light at an end face of an optical fiber and improving data accuracy and reliability. It is in.

[0024]

According to a first aspect of the present invention, there are provided a first scintillator and a second scintillator arranged in two layers and having mutually different emission wavelength bands, and two types of light in the emission wavelength band are mixed. A first photodetector having a first color filter for selectively extracting light from the first scintillator; and a second color filter for selectively extracting light from the second scintillator. An optical wavelength discrimination type radiation detector including a second photodetector,
A direction connecting the center of the first color filter and the center of the second color filter and a longitudinal direction of each of the scintillators are perpendicular or oblique, and are arranged at positions which can be closest to each other.

According to the present invention, the light of the second scintillator is generated at a position separated from the second color filter,
When the light propagates through the scintillator, the propagation path is geometrically blocked by the first color filter, and the probability of absorbing light can be reduced.

According to a second aspect of the present invention, the first scintillator and the second scintillator which are arranged in two layers and have mutually different emission wavelength bands, and the first scintillator includes two types of light in the emission wavelength band. A first photodetector having a first color filter for selectively extracting light from the scintillator and a second photodetector having a second color filter for selectively extracting light from the second scintillator An optical wavelength discrimination type radiation detector including a detector, wherein the first color filter and the second color filter are located at positions that can be disposed with respect to the first scintillator and the second scintillator. , Are arranged at positions farthest from each other.

According to the present invention, the light of the second scintillator is generated at a position distant from the second color filter,
When the light propagates through the scintillator, the propagation path is geometrically blocked by the first color filter, and the probability of absorbing light can be reduced.

According to a third aspect of the present invention, the first scintillator and the second scintillator which are arranged in two layers and have mutually different emission wavelength bands, and the first scintillator includes two types of light in the emission wavelength band. A first photodetector having a first color filter for selectively extracting light from the scintillator and a second photodetector having a second color filter for selectively extracting light from the second scintillator An optical wavelength discrimination type radiation detector including a detector, wherein the second scintillator is disposed on a lower layer side of a photodetector, and air is provided between the first color filter and the second scintillator. Are arranged so as to intervene, and the second color filter and the second scintillator are coupled so as to be in close contact with each other optically.

According to the present invention, the light of the second scintillator is generated at a position separated from the second color filter,
When the light propagates through the scintillator, the first color filter does not exist on the propagation path, thereby eliminating the effect of depriving the total reflection effect and absorbing light.

According to a fourth aspect of the present invention, the first scintillator and the second scintillator which are arranged in two layers and have mutually different emission wavelength bands, and the first scintillator having two types of light in the emission wavelength band are mixed. A first photodetector having a first color filter for selectively extracting light from the scintillator; and a second light having a second color filter for selectively extracting light from the second scintillator. An optical wavelength discrimination type radiation detector including a detector, wherein the second scintillator is disposed on a lower layer side of a photodetector side, and is disposed between the first color filter and the second scintillator. The second color filter and the second scintillator are optically connected to each other so that air is interposed therebetween, and the first color filter and the second scintillator are coupled to each other.
Is provided as a part of the inner surface, and a closed space in which a treatment capable of reflecting light is performed on a treatable portion other than the first color filter and the second scintillator is provided.

According to the present invention, the light collecting effect of the second scintillator is not adversely affected, and the light generated by the first scintillator and transmitted through the second scintillator is irregularly reflected, so that the first scintillator is not reflected. The probability of detection by the first photodetector via the color filter can be increased.

According to a fifth aspect of the present invention, the first scintillator and the second scintillator which are arranged in two layers and have mutually different emission wavelength bands, and the first scintillator includes two types of light in the emission wavelength band. A first photodetector having a first color filter for selectively extracting light from the scintillator and a second photodetector having a second color filter for selectively extracting light from the second scintillator An optical wavelength discrimination type radiation detector including a detector, wherein the second scintillator is disposed on a lower layer side of a photodetector side, and an optical path between the second color filter and the second scintillator is provided. The first color filter and the first photodetector, which are in close contact with each other and have the first color filter and the first photodetector in close contact with the second scintillator with air interposed therebetween. Opening area Ri also characterized by providing a light guide having a large opening area.

According to the present invention, the light guide which does not adversely affect the light condensing action of the second scintillator and which is generated by the first scintillator and transmitted through the second scintillator has a large aperture area. And the light of the light guide is guided to the first photodetector via the first color filter, so that the probability of detecting the light of the first scintillator can be increased.

According to a sixth aspect of the present invention, there is provided the inner surface forming the closed space subjected to the reflection treatment according to the fourth aspect, wherein the second surface comprises
And the first color filter is set to the lower direction, and the average reflection direction from the side is set to coincide with the position where the perpendicular line of the first color filter and the second scintillator intersect. The angle may be inclined or a light reflecting plate may be inserted at the angle.

According to the present invention, the light generated by the first scintillator and transmitted through the second scintillator does not adversely affect the light-collecting action of the second scintillator, and the probability of being captured by the first color filter High position, ie the first
Are unevenly distributed so as to be averagely reflected toward the upper position of the color filter. For this reason, the probability of detecting the light of the first scintillator can be increased as compared with the case where the photons are uniformly distributed in the reflected closed space.

According to a seventh aspect of the present invention, the optical fiber is interposed between a photodetector and an optical fiber, is optically attached to the end face of the optical fiber, and can transmit light having a maximum critical angle that can be transmitted by the optical fiber. A light waveguide having an emission end face to the photodetector having an area larger than the end face of the optical fiber; and a light-receiving surface of the light detector, a waveguide or the light-receiving surface and an emission surface of the waveguide. Taking a measure to absorb or scatter light propagating to a portion corresponding to a central axis extension of the core of the optical fiber at a position between the optical fiber and the optical fiber to guide the light incident on the photodetector to the optical fiber. It is characterized by.

According to the present invention, the portion treated to absorb or diffusely reflect light absorbs or scatters only the component propagating in the optical fiber near the reflection angle of 0 ° including the straight component. In addition, the probability that strong Fresnel reflected light (backscattered light) re-enters the optical fiber, propagates, and is erroneously detected by another photodetector can be reduced.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a radiation detector according to the present invention will be described with reference to FIGS. In this embodiment, as shown in FIG. 1A, a first scintillator 1 and a second scintillator 2 are arranged vertically and a first scintillator 2 having a first color filter 3 on a lower surface of the second scintillator 2. A second photodetector 6 having one photodetector 4 and a second color filter 5 is arranged. Although not shown, the whole is housed in a light-shielding case, and the upper layer side of the first scintillator 1 in the figure is a radiation incident surface, which is an incident film which can transmit target radiation and shield external light. Covered with.

FIGS. 1B and 1C are top views of the radiation detector in FIG. 1A. FIG. 1B shows a first example, and FIG.
Shows a second example. The first example of FIG.
The color filter 3 and the first photodetector 4 are integrated with the second color filter 5 and the second photodetector 6, respectively. These are integrated into the first and second scintillators 1 and 2, respectively. On the other hand, it is a pattern orthogonal to the longitudinal direction. The second example of FIG. 1C is a pattern in which the photodetectors 4 and 6 are arranged not obliquely but obliquely at a certain angle depending on the size of the photodetectors 4 and 6.

According to the present embodiment, the light emitted on the left side of the second scintillator 2 in the drawing
Is propagated by total internal reflection, but the lower the probability that the light passes through the first color filter 1 in the propagation paths from all directions, the more the light detection efficiency with respect to the second scintillator 2 is improved. For this reason, it is effective to arrange at 90 degrees with respect to the longitudinal direction which is the main propagation direction, or at an angle close to 90 degrees when there is a trade-off with the size.

Next, referring to FIGS.
A second embodiment of the radiation detector according to the present invention will be described. In this embodiment, as shown in FIG. 2A, a first scintillator 1 and a second scintillator 2 are vertically arranged, and a first scintillator 2 having a first color filter 3 on a lower surface of the second scintillator 2. A second photodetector 6 having one photodetector 4 and a second color filter 5 is arranged at both ends with an interval. Note that, in the present embodiment, similarly to the first embodiment, the light shielding case and the incident film are not particularly illustrated.

FIGS. 2 (b) and 2 (c) are top views of the radiation detector of FIG. 2 (a) as viewed from above, and FIG.
(C) shows a second example. Although the first color filter 3 and the first light detector 4 are integrated with the second color filter 5 and the second light detector 6, respectively,
These are arranged so as to be able to keep the distance from each other with respect to the sensitive surfaces of the first scintillator 1 and the second scintillator 2, that is, are separated from each other.

In the first example of (b), the first scintillator 1 and the second scintillator 2 are each rectangular, and the width thereof is substantially the same as the diameter of the first and second color filters 3 and 5 to be used. Shows the case. In this case, they are arranged on both sides in the longitudinal direction.

The second example of (c) is the first color filter 3
Also, the case where the width and length of the first scintillator 1 and the second scintillator 2 are larger than the diameter of the second color filter 5 is shown, and in this case, it is preferable to arrange them at diagonal positions.

In this positional relationship, for example, the light that has propagated to the position of the second color filter 5 does not propagate and reach the position of the first color filter 3 again even if the color filter 5 is not provided. Can be considered. That is, it can be said that the arrangements do not interfere with each other in the propagation path.

Next, a third embodiment of the radiation detector according to the present invention will be described with reference to FIG. In this embodiment, as shown in FIG. 3, a first scintillator 1 and a second scintillator 2 are vertically arranged, and an air layer 18 is provided below the second scintillator 2 to form a first collar. A first photodetector 4 having a filter 3 is arranged, and a second photodetector 6 having a second color filter 5 is arranged on the lower surface of the second scintillator 2. In this embodiment, as in the first embodiment, the light shielding case and the incident film are not particularly illustrated.

In the present embodiment, the first color filter 3 and the first photodetector 4 are integrated, but the first color filter 3 itself does not adhere to the second scintillator 2 and An air layer 18 is interposed between the second scintillator 2 and the second scintillator 2.

According to the present embodiment, the light generated by the second scintillator 2 is diffused and propagated while being trapped inside the second scintillator 2 by the total reflection effect. One color filter 3 has no influence. Thereby, light collection utilizing the total reflection effect of the second scintillator 2 is ideally performed.

Next, FIG. 4 (a) and FIG.
A fourth embodiment of the radiation detector according to the present invention will be described. FIG. 4B is a cross-sectional view taken along the line AA of FIG.

In this embodiment, as shown in FIG. 4A, a first scintillator 1 and a second scintillator 2 are vertically arranged, and a closed space 19 is provided below the second scintillator 2.
The first color filter 3 is provided on the reflection surface 7 surrounding the closed space 19, and the first photodetector 4 is disposed at an end thereof, and the second color filter 3 is in contact with the second scintillator 2. A second photodetector 6 having a color filter 5 is arranged. Note that, in the present embodiment, similarly to the first embodiment, the light-shielding case and the incident film are not particularly illustrated.

The reflection surface 7 is treated so that light is reflected on all possible parts. As an example of the treatment, there is a method of applying a material that irregularly reflects the light of the scintillator more efficiently than the material forming the reflection surface 7, for example, titanium oxide.

The closed space 19 has a detection case on the side and a second case on the top.
The scintillator 2 can be created by adding one reflector having a hole in which the first color filter 3 is embedded in the bottom surface and through which the second photodetector 2 can penetrate. Then, this reflecting plate forms the reflecting surface 7.

According to the present embodiment, the light generated by the second scintillator 2 is diffused and propagated while being trapped inside the second scintillator 2 by the total reflection effect. One color filter 3 has no effect. Furthermore, by filling the light emitted from the first scintillator 1 into the reflection surface 7 which is a closed space, the probability of reaching the first color filter 3 is increased.

Generally, assuming that photons are uniformly distributed due to irregular reflection in the reflecting surface 7, the ratio of the area of the color filter 3 effective for light detection to the inner surface area of the reflecting surface 7 is closed. Is larger, the probability of light collection increases.

Next, FIG. 5A and FIG.
A fifth embodiment of the radiation detector according to the present invention will be described. In the present embodiment, as shown in FIGS. 5A and 5B, the first scintillator 1 and the second scintillator 2 are arranged vertically, and the reflecting plate 8 is arranged on the lower surface of the second scintillator 2. The first photodetector 4 having the first color filter 3 is arranged on the lower surface of the reflection plate 8, and the second
A second photodetector 6 having a second color filter 5 is arranged on the lower surface of the scintillator 2. Note that, in the present embodiment, similarly to the first embodiment, the light-shielding case and the incident film are not particularly illustrated.

In this embodiment, similar to the fourth embodiment,
The same applies to the use of the diffuse reflection action in a closed space having the second scintillator 2 as the upper surface. However, the first
In order to increase the probability of light entering from the first scintillator 1 to the color filter 3, the oblique reflection is performed such that the average reflection direction of the irregularly reflected light on the side surface is concentrated at the upper position of the first color filter 3. The feature is that the plate 8 is provided.

FIGS. 5A and 5B show that the reflection plate 8 is applied to all four side surfaces. (B)
FIG. 3A is an elevation view of FIG. 3A as viewed from the second color filter 5 and the second photodetector 6 side.

It is known as Lambert's law that the reflection angle distribution of the irregular reflection surface has a cosine distribution. For this reason, if the side surface is irregularly reflected toward the second scintillator 2 obliquely above the first scintillator 2 than the side surface is arranged perpendicular to the first color filter 3, then the second scintillator 2 or the first scintillator 2 The light irregularly reflected by the scintillator 1 of
That is, it becomes easy to face the direction of the first color filter 3.

A part or all of the four side surfaces are angled so that the average reflection direction is directed to the vicinity of a point where a perpendicular line extending from the center of the first color filter 3 and the second scintillator intersect. Attach In reality, it can be easily realized by adjusting the angle of the reflector 8 in the detector case.

According to the present embodiment, light collection utilizing the total reflection effect of the second scintillator 2 is ideally performed, and the amount of light collected by the first scintillator can be increased.

Next, a sixth embodiment of the radiation detector according to the present invention will be described with reference to FIG. In this embodiment, as shown in FIG. 6, a first scintillator 1 and a second scintillator 2 are vertically arranged, and a light guide 9 having an air layer 18 on the lower surface of the second scintillator 2 is provided.
Is disposed, and a first photodetector 4 having a first color filter 3 is disposed on a lower surface of the light guide 9.
The second color filter 5 directly on the lower surface of the scintillator 2
And a second photodetector 6. In this embodiment, as in the first embodiment, the light-shielding case and the incident film are not particularly illustrated.

In the present embodiment, the second scintillator 2
Has only the second color filter 5 attached in close contact with it,
It is accompanied by a second photodetector 6. The first color filter 3 is mounted in close contact with the light guide 9 and has a first photodetector 4 attached thereto.

Although the light guide 9 partially penetrates through the second photodetector 6, the upper surface has the same opening surface as the second scintillator 2, and this opening surface is formed in the second scintillator 2. On the other hand, it faces through the air layer 18 and can take in light from the first scintillator 1.

The bottom surface of the light guide 9 is narrowed down to a size sufficient to mount the first color filter 3. The light guide 9 having a large opening area enables the first
The light emitted from the surface of the scintillator 1 and the second scintillator 2 is efficiently taken in, and the wavelength is selected by the first color filter 3 therefrom, so that only the light of the first scintillator 1 can be efficiently taken out. it can.

According to the present embodiment, light collection utilizing the total reflection effect of the second scintillator 2 is ideally performed, and the amount of light collected by the first scintillator can be increased.

Next, a radiation detector according to a seventh embodiment of the present invention will be described with reference to FIG. In the present embodiment, as shown in FIG.
11 and a photodetector 15 having a light-sensitive surface 14 are arranged in series, and these are connected in series via an optical coupling material 12 that is brought into optical close contact. Note that a reflection suppression spot 13 is provided between the light-exiting end face of the waveguide 11 and the light-sensitive surface 14.

The optical coupling material 12 is used to prevent a large difference in the refractive index between the components, that is, the connection portion with the optical fiber 10, the waveguide 11, and the light-sensitive surface 14. As the optical grease, silicon grease or the like is used. As an example of the reflection suppressing spot 13, there is a method of applying black paint or the like on the light receiving surface 14 or the waveguide 11 side.

The light transmitted by the optical fiber 10 uses a waveguide 11 having such a parameter that light rays of any angle (mode) can propagate by total internal reflection. Generally, a cylinder or a prism made of glass, transparent resin, or the like is applicable. Thereby, the optical waveguide 11 has an action of expanding the sectional area of the propagating light.

In the expanded cross section, particularly a straight ray hitting a limited portion at the center and a component having a small propagation angle close to the straight ray generate particularly strong Fresnel reflection. Moreover, the Fresnel light is returned into the optical fiber 10 again as backscattered light.

However, according to the present embodiment, by providing a reflection suppressing spot 13 between the waveguide 11 and the optical coupling material 12 to perform absorption, scattering, and the like, the specifically strong Fresnel reflection component can be reduced. The optical fiber 10 can be prevented from returning.

Since the reflection suppressing spot 13 may be a very small spot, the ratio of the masking area to the cross-sectional area of the propagating light can be kept small.
For this reason, the original signal is not significantly weakened. Therefore, the influence of the reflected pulse, which is a major problem in the optical radiation detector of the optical fiber transmission type, can be extremely reduced, reduced, and suppressed.

[0072]

According to the first and second aspects of the present invention, in the wavelength identification type radiation detector, the amount of light collected by the scintillator is increased by reducing the influence of light absorption between the color filters, thereby detecting radiation. Efficiency and its uniformity can be increased.

According to the third aspect of the present invention, in the wavelength discrimination type radiation detector, when light is collected by total reflection by the scintillator of the second layer out of the two layers, the light from the first scintillator is collected. By providing a method that is not affected by the light emitting means, it is possible to increase the amount of light collected by the second scintillator, thereby increasing the radiation detection efficiency and its uniformity.

According to the fourth to sixth aspects of the present invention, in the wavelength discrimination type radiation detector, when light is collected by total reflection by the scintillator of the second layer out of the two layers, the light from the first scintillator is used. By providing a method that is not affected by the means for condensing light, the amount of light condensed by the second scintillator can be increased, thereby increasing the radiation detection efficiency and uniformity.

In addition, as for the light of the first scintillator, the light condensing amount of the first scintillator can be reduced by using a reflection space, a reflector, or a light guide having a large aperture area as a means for improving the light condensing amount of the irregularly reflected light. And thereby the radiation detection efficiency and its uniformity can be increased.

According to the seventh aspect of the present invention, in an optical transmission type radiation detector having means for transmitting light to an optical detector by an optical fiber, an error caused by Fresnel reflection generated between the optical fiber and the optical detector. By providing connection means for suppressing or reducing signals, the accuracy of the radiation detector and the reliability of data can be improved.

[Brief description of the drawings]

FIG. 1A is an elevation view showing a first embodiment of a radiation detector according to the present invention, FIG. 1B is a top view showing a first example of FIG. 1A, and FIG. FIG. 4A is a top view illustrating a second example of FIG.

FIG. 2A is an elevation view showing a second embodiment of the radiation detector according to the present invention, FIG. 2B is a top view showing the first example of FIG. 2A, and FIG. FIG. 4A is a top view illustrating a second example of FIG.

FIG. 3 is an elevation view showing a third embodiment of the radiation detector according to the present invention.

FIG. 4A is an elevation view illustrating a fourth embodiment of the radiation detector according to the present invention, and FIG. 4B is a cross-sectional view taken along the line AA of FIG.

5A is an elevational view showing a fifth embodiment of the radiation detector according to the present invention, and FIG. 5B is an elevational view as seen from the second color filter side in FIG.

FIG. 6 is an elevation view showing a sixth embodiment of the radiation detector according to the present invention.

FIG. 7 is a side view showing a seventh embodiment of the radiation detector according to the present invention.

FIG. 8A is an elevation view showing a first example for explaining a conventional radiation detector, FIG. 8B is an elevation view showing a second example, and FIG. (B) Top view.

FIG. 9 is a side view showing a main part of a radiation detector using a conventional optical fiber.

FIG. 10 is a system diagram showing a conventional radiation detector in which photodetectors are connected to both ends of an optical fiber.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st scintillator, 2 ... 2nd scintillator, 3
, A first color filter, 4 ... a first photodetector, 5 ... a second color filter, 6 ... a second photodetector, 7 ... a reflection surface, 8 ... a reflection plate, 9 ... a light guide, 10 ... Optical fiber,
11 ... waveguide, 12 ... optical coupling material, 13 ... reflection suppression spot,
14 ... light receiving surface, 15 ... photodetector, 16 ... radiation sensor, 17 ...
Data processing device, 18 ... air space, 19 ... closed space.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Kazumi Watanabe 1-term, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term in Toshiba R & D Center (reference) 2G088 AA01 GG14 GG15 GG16 JJ01 KK28 KK29

Claims (7)

[Claims] 1. A first scintillator and a second scintillator arranged in two layers and having mutually different emission wavelength bands, and light from the first scintillator in which two types of light in the emission wavelength band are mixed is selectively selected. Comprising: a first photodetector having a first color filter for extracting light from the second scintillator; and a second photodetector having a second color filter for selectively extracting light from the second scintillator. In the wavelength discrimination type radiation detector, the first color filter and the second
A direction connecting the centers of the color filters and a longitudinal direction of each of the scintillators is at a right angle or obliquely, and is arranged at a position which can be approached most. 2. A first scintillator and a second scintillator arranged in two layers and having mutually different emission wavelength bands, and light from the first scintillator is selected from two types of light in the emission wavelength band. A first photodetector having a first color filter for selectively extracting light; and a second photodetector having a second color filter for selectively extracting light from the second scintillator. In a radiation detector of an optical wavelength discrimination type, the first color filter and the second color filter are the most distant from each other among positions that can be arranged with respect to the first scintillator and the second scintillator. A radiation detector, which is arranged at a position. 3. A first scintillator and a second scintillator arranged in two layers and having mutually different light emission wavelength bands, and light from the first scintillator is selected from two types of light in the light emission wavelength band. A first photodetector having a first color filter for selectively extracting light; and a second photodetector having a second color filter for selectively extracting light from the second scintillator. In a radiation detector of an optical wavelength discrimination type, the second scintillator is disposed on a lower layer side of a photodetector, and air is interposed between the first color filter and the second scintillator. A radiation detector, wherein the radiation detector is arranged and coupled so that the second color filter and the second scintillator are brought into optical close contact with each other. 4. A first scintillator and a second scintillator arranged in two layers and having mutually different emission wavelength bands, and light from the first scintillator is selected from a mixture of two types of light in the emission wavelength band. A first photodetector having a first color filter for selectively extracting light, and a second photodetector having a second color filter for selectively extracting light from the second scintillator. In the optical wavelength discrimination type radiation detector described above, the second scintillator is disposed on a lower layer side of the photodetector, and air is interposed between the first color filter and the second scintillator. And the second color filter and the second scintillator are coupled so as to be in close contact with each other optically, and the first color filter and the second scintillator are part of an inner surface. A radiation detector provided with a closed space in which a treatment capable of reflecting light is performed on a treatable portion other than the first color filter and the second scintillator. 5. A first scintillator and a second scintillator arranged in two layers and having mutually different light emission wavelength bands, and light from the first scintillator is selected from two types of light in the light emission wavelength band. A first photodetector having a first color filter for selectively extracting light; and a second photodetector having a second color filter for selectively extracting light from the second scintillator. In a radiation detector of an optical wavelength discrimination type, the second scintillator is arranged on a lower layer side of the first scintillator side, and optically adheres between the second color filter and the second scintillator. Opening area of the first color filter in which the first color filter and the first photodetector are in close contact with each other at a position where air is interposed between the second scintillator and the second scintillator. A radiation detector comprising a light guide having a larger opening area. 6. An average reflection direction from a side surface of the inner surface constituting the closed space subjected to the reflection treatment according to claim 4, wherein the second scintillator is an upper surface direction, the first color filter is a lower surface direction. 5. The method according to claim 4, wherein the angle of the side surface is inclined so that the angle of the light is coincident with the intersection of the perpendicular line of the first color filter and the second scintillator, or a light reflecting plate is inserted at the angle. Radiation detector. 7. An optical fiber interposed between a photodetector and an optical fiber, optically adhered to an end face of the optical fiber, and capable of transmitting light having a maximum critical angle that can be transmitted by the optical fiber. A light waveguide having an emission end face to the photodetector having a larger area than an end face, and a light receiving surface of the light detector, a waveguide or a position between the light receiving surface and the light emission surface of the waveguide. And performing a treatment for absorbing or scattering light propagating to a portion corresponding to a central axis extension of the core of the optical fiber to guide incident light to the photodetector to the optical fiber. Detector.