US20030030003A1 - Radiation detecting apparatus - Google Patents

Abstract

In a radiation detecting apparatus, an α ray and a β ray are transmitted through a light shielding film but an incident light is shielded. A first light is emitted from a first scintillator by the α ray transmitted through the light shielding film. The first scintillator has an emission center wavelength based on the α ray. A second light is emitted in a second scintillator by the β ray transmitted through the light shielding film. The second scintillator has an emission center wavelength based on the β ray. The first and second lights are detected by two photo-detectors, respectively. The first emission center wavelength and the second emission center wavelength are different from each other.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention[0001]
• The present invention relates to a radiation measurement technique used in a facility for handling radioactive material, such as a nuclear power plant or the like, and more particularly, to a radiation detecting apparatus which is capable of simultaneously and independently measuring radiations such as a and β rays at a same position, and is suitable to a practical use as a radiation monitor.[0002]
• 2. Description of the Prior Art[0003]
• FIG. 26 shows a phoswich detecting apparatus (phosphor sandwich detecting apparatus) as a conventional example of a radiation detecting apparatus for simultaneously detecting an α ray and a β ray.[0004]
• This radiation detecting apparatus is provided with a[0005]light shielding film1 through which the α and β rays are transmitted and for shielding light from the outside of the apparatus. The radiation detecting apparatus is also provided with afirst scintillator2 and asecond scintillator3 which are piled up below thelight shielding film1 shown in FIG. 26.
• There are many cases where ZnS (Ag) detecting an α ray is used as the[0006]first scintillator2, and plastic detecting α and β rays is used as thesecond scintillator3. The first andsecond scintillators2 and3 piled into two layers are directly mounted to aphoto detector5 so as to be received in acase6. In general, a photo-multiplier tube having a high speed response and a high sensitivity is used as the photo-detector5.
• A decay time constant of emission of ZnS (Ag) constituting the[0007]first scintillator2 is μsec order, but that of emission of plastic constituting thesecond scintillator3 is several tens of n sec order. Therefore, the decay time constant of emission of theplastic scintillator3 is considerably shorter as compared with that emission of the ZnS (Ag)first scintillator2. When an output current signal of the photo-detector5 is converted into a voltage signal by means of an RC integrating circuit having a sufficiently long time constant as compared with each decay time constant of emission of thescintillators2 and3, a pulse rise time is substantially equal to a decay time of emission, and shows an index decay waveform of a time constant determined by a resistor R and a capacity C. This signal converting process can be carried out in a pre-amplifier unit connected to the photo-multiplier tube and included in the photo-detector5.
• The converted voltage signal is amplified up to a voltage level which is capable of being analyzed by means of a waveform[0008]discrimination processing unit7, as the necessity arises. When the voltage signal is inputted in the waveformdiscrimination processing unit7, an analog-digital converter of theprocessing unit7, in order to output a pulse signal having a pulse height proportional to the rise time of the inputted signal, converts the pulse height of the inputted signal into a digital value so that a general analyzer of theprocessing unit7 measures a pulse height distribution (a spectrum data) on the basis of the converted digital value.
• It is possible to distinguish an emission of the[0009]first scintillator2 and that of thesecond scintillator3 on the basis of the spectrum data showing the rise time and obtained from the waveformdiscrimination processing unit7.
• FIG. 27 shows, as another conventional example, an α-β rays detecting apparatus using a[0010]sensor8 for measuring energy spectrum.
• For example, an Si semiconductor sensor is used as the[0011]sensor8 for measuring energy spectrum of the above apparatus. However, thesensor8 has a sensitivity to a room light and the like other than a radiation; for this reason, similarly to the above described radiation detecting apparatus, alight shielding film1 is mounted on thesensor8 so that thesensor8 is housed in acase6.
• An output signal of the[0012]sensor8 is analyzed by means of a pulseheight analysis system9, so as to be measured as an energy spectrum. In general, theanalysis system9 includes: a charge sensitive pre-amplifier for processing the sensor output signal; a linear amplifier, an analog-digital converter, a pulse height analyzer for analyzing multiple pulse heights and the like. In the energy spectrum data obtained by theanalysis system9, the α-ray data and the β-ray data show different distributions and peak shapes, respectively, and therefore, it is possible to distinguish the α ray and the β ray by processing these spectrum data corresponding to the α and β rays.
• However, the pulse height[0013]discrimination processing unit7 necessary for the conventional phoswich detecting apparatus shown in FIG. 16 is a processing unit for analyzing a pulse rise, and is very expensive. Therefore, this conventional detecting apparatus is useful to a study in an experimental level.
• However, as a detecting apparatus which is mounted in a monitoring device used in an actual nuclear facility or the like, there is a problem relating to a cost. Moreover, the waveform discrimination processing unit analyzes a rise time itself, and is an over specification in the case of discriminating signals having different rise times, respectively.[0014]
• Furthermore, in view of the principle, in order to obtain a rise time, for example, there is a need of carrying out a signal detection at a 10% level and a 90% level of an inputted pulse height value, so that there is a problem that it is impossible to analyze and measure a signal having a low pulse height value. This problem relates to a dynamic range of the pulse height value of the signal. For example, an emission of ZnS (Ag) scintillator generated by an α ray is considerably larger than that of the plastic scintillator generated by a β ray, and actually, the output signal of the photo-multiplier tube corresponding to the emission of ZnS (Ag) is larger 10 times or more as much as that of the photo-multiplier tube corresponding to the emission of β ray of the plastic scintillator at the point of time of being converted into the voltage signals.[0015]
• Therefore, since the β ray signal has a low pulse height value and is continuously distributed on a low energy side, the measurement of the β ray is disadvantageous as compared with that of the α ray. In particular, a component of the β ray having a low pulse height value is not analyzed and measured so that there is a problem that an effective β-ray sensitivity gets to be low. Especially, in the case where a thickness of the plastic scintillator is made thin in order to suppress a γ-ray sensitivity, the emission of the plastic scintillator is further lowered so that the aforesaid phenomenon of lowering the effective β-ray sensitivity is further accelerated.[0016]
• In addition, in the case of the radiation detecting apparatus using the energy[0017]spectrum measuring sensor8 as shown in FIG. 27, the pulse height analyzer which is substantially equal to the above waveform discrimination processing unit must be required; as a result, there is a problem that the cost of the radiation detecting apparatus gets to be high. Furthermore, since an effective atomic weight of a base material of the energyspectrum measuring sensor8 is larger than the plastic scintillator, a γ-ray sensitivity is high so that there is a problem that a γ-ray signal is mixed into a β-ray signal.
• Still furthermore, in the case where measurement is not carried out in a vacuum state, or in the case of measuring an α ray from an α-ray emission nuclide absorbed to a filter paper, an energy loss of the α-ray is high and a fluctuation of range is large. For this reason, a Gaussian peak as obtained in vacuum is not obtained so that there is the case where the energy spectrum of the α-ray overlaps with that of the β-ray, whereby, in spite of measuring the energy spectrums of the α and β rays, it is hard to clearly distinguish the α ray and the β ray.[0018]
SUMMARY OF THE INVENTION
• The present invention is directed to overcome the foregoing problems.[0019]
• Accordingly, it is an object of the present invention to provide a radiation detecting apparatus which is capable of practically being used as a detector for radiation monitor, and being manufactured at a low cost, and further is able to independently and simultaneously detect an α ray and a β ray while maintaining sensitivities of these rays at the utmost limit and sufficiently preventing a γ ray sensitivity.[0020]
• In addition, it is another object of the present invention to provide a radiation detecting apparatus having a rationally arrangement of first and second photo-detectors so as to make high an efficiency of detecting emissions of the first and second scintillators.[0021]
• That is, in the radiation detecting apparatus, as described above, a light emitted in the first scintillator for α ray transmits through the second scintillator for β ray, and then, is guided to at least one photo-detector by means of condensing means. In this case, conventionally, the waveform discrimination processing unit for analyzing a rise of pulse has been applied in view of a pulse rise time of a signal converted by an RC integrating circuit, wherein the pulse rise time is substantially equal to a decay time of emission of each scintillator.[0022]
• In view of this point of using the waveform discrimination processing unit, the inventors have a concept that it is possible to dispense with the waveform discrimination processing unit for analyzing a pulse rise, which is required for the conventional radiation detecting apparatus, by adjusting and optimizing the used scintillators, emission wavelengths of the scintillators and quantities of emission thereof.[0023]
• More specifically, it is preferable that a photo-multiplier tube is used as a photo-detector in view of a response speed and sensitivity.[0024]
• In other words, since the emission wavelength of the first scintillator is set to be different from that of the second scintillator, it is possible to adjust and optimize the scintillators, emission wavelengths of these scintillators and quantities of emission thereof in accordance with those. Furthermore, a detecting apparatus is constituted by intentionally varying the emission decay times of these scintillators and emission wavelengths thereof, whereby it is possible to provide means for optically discriminating between the emission wavelengths of these scintillators.[0025]
• Moreover, as means for independently and simultaneously detecting an α ray and a β ray while securing the maximum sensitivity of them, the inventors have a concept that a light is easy to be confined in the first and second scintillators so as to improve each condensing density of each of the first and second scintillators by an arrangement thereof. More specifically, the first scintillator emitting a light by an α ray is formed very thin so as to restrict β-ray and γ-ray sensitivities, and for example, there are many cases where the first scintillator is composed of a powder, a sintering body and other similar materials. Therefore, in the first scintillator, a diffuse reflection is made therein so that a light is emitted thereto. The emitted light transmits through the second scintillator for a β ray so as to be guided to the photo-detector by the condensing means.[0026]
• In this structure, in the case where an air is interposed between the first and second scintillators, when the light emitted from the first scintillator is transmitted through the second scintillator, though a probability of an occurrence of Fresnel reflection increases, since the second scintillator is surrounded by the air having a refractive index value lower than that of the second scintillator, it is easy to confirm the light emitted in the second scintillator. For this reason, as the condensing means for the second scintillator, it is easy to employ a method of using the emitted light condensed on the edge side of the second scintillator with a high density.[0027]
• In accordance with the above described conception, in order to achieve such objects, according to one aspect of the present invention, there is provided a radiation detecting apparatus comprising: a light shielding film for transmitting therethrough first and second radiations while shielding an incidence of light; a first scintillator for emitting a first light by the first radiation transmitted through the light shielding film, the first scintillator having an emission center wavelength based on the first radiation; a second scintillator for emitting a second light by the second radiation transmitted through the light shielding film, the second scintillator having an emission center wavelength based on the second radiation; and detection means having at least one photo-detector for detecting the first light emitted from the first scintillator and the second light emitted in the second scintillator, the first emission center wavelength and the second emission center wavelength being different from each other.[0028]
• In preferred embodiment of this one aspect, the first emission center wavelength is a wavelength of the first light emitted in the first scintillator and having a peak emission intensity in an emission wavelength band of the first scintillator, and the second emission center wavelength is a wavelength of the second light emitted in the second scintillator and having a peak emission intensity in an emission wavelength band of the second scintillator.[0029]
• In preferred embodiment of this one aspect, the first scintillator and second scintillator are arranged in parallel to each other so that the second scintillator is located away from the first scintillator at a predetermined distance, further comprising means for condensing the first light emitted from the first scintillator and the second light emitted in the second scintillator on the detection means; and an air layer interposed between the first and second scintillators, the first emission center wavelength of the first scintillator being set shorter than the second emission center wavelength of the second scintillator.[0030]
• According to the one aspect of the present invention described above, the air layer is interposed between the first and second scintillators, and thereby, the second scintillator is surrounded by the air layer having a refractive index value lower than itself, so that the second light is confined in the second scintillator. Therefore, it is easy to employ a method of using a light condensed on the edge side of the second scintillator with a high density. Furthermore, there is no need of providing an intermediate material required for bonding of these first and second scintillators and optically closely connecting them. In addition, the present invention is suitable for the case where there is an anxiety of alteration due to a chemical interaction of these intermediate materials and the first and second scintillators. Still furthermore, an independence of each scintillator is secured, making it possible to carry out maintenance, inspection and replacement with respect to only one of these scintillators.[0031]
• Moreover, the emission center wavelength of the first scintillator is set shorter than the emission center wavelength of the second scintillator, making it possible to also use means for optically identifying wavelengths of the first and second lights so as to dispense a waveform discrimination processing unit for analyzing pulse rise times.[0032]
• This one aspect of the present invention further has means for condensing the first light emitted from the first scintillator and the second light emitted in the second scintillator on the detection means, wherein the first scintillator and second scintillator are closely optically adhered with each other, the first emission center wavelength of the first scintillator being set shorter than the second emission center wavelength of the second scintillator.[0033]
• According to the one aspect of the present invention, the first and second scintillators are arranged so as to optically closely be adhered with each other, making it possible to reduce an internal capture by a Fresnel reflection based on a difference in refractive indexes due to the air layer and by a total internal reflection in the second scintillator, and thus improving a transmission probability of the first light of the first scintillator through the second scintillator. Therefore, it is easy to employ of using the second light from the back surface of the second scintillator which is not adhered with the first scintillator.[0034]
• This one aspect of the present invention further has means for condensing the first light emitted from the first scintillator and the second light emitted in the second scintillator on the detection means, wherein the first scintillator and second scintillator are closely optically adhered with each other, the first emission center wavelength of the first scintillator being set longer than the second emission center wavelength of the second scintillator.[0035]
• According to the one aspect of the present invention, the first and second scintillators are arranged so as to optically and closely be adhered with each other, making it possible to improve a transmission probability of the first light of the first scintillator through the second scintillator. Therefore, it is easy to employ a method of condensing the first light of the first scintillator from the back surface of the second scintillator, as the condensing means.[0036]
• One aspect of the present invention further has a condensing box for condensing the first and second lights on the detection means, the condensing box having an inner surface for diffusely reflecting the first and second lights and a side surface, the light shielding film being mounted on the side surface on which the first and second radiations incident, the first and second scintillators being arranged inside the light shielding film, and wherein the detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector, the first filter being adapted to transmit therethrough only the first light emitted from the first scintillator, the second filter being adapted to transmit therethrough only the second light emitted in the second scintillator.[0037]
• In the case of the one aspect of the present invention, the first and second lights having different emission wavelength bands are mixed to be filled in the condensing box while diffusely being reflected. The first filter is mounted on the sensitive surface of the first photo-detector, and the second filter is mounted on the sensitive surface of the second photo-detector. Because the first filter is adapted to transmit therethrough only the first light emitted from the first scintillator, and the second filter is adapted to transmit therethrough only the second light emitted in the second scintillator, it is possible to independently detect the first and second lights corresponding to the first and second radiations without using a specific electronic equipment for discrimination and identification. Furthermore, the condensing box is used so that it is easy to apply a large-area scintillator to the radiation detecting apparatus.[0038]
• In preferred embodiment of this one aspect, the second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, the detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector, the first filter being adapted to transmit therethrough only the first light emitted from the first scintillator, the second filter being adapted to transmit therethrough only the second light emitted in the second scintillator, and wherein the first filter and the second filter are closely optically adhered on the back surface of the second scintillator.[0039]
• In preferred embodiment of this one aspect, the second scintillator has a substantially rectangular shape, and wherein the first photo-detector and the second photo-detector are adjacently arranged so that a line is crossed to a longitudinal direction of the second scintillator, the line connecting a center point of the sensitive surface of the first photo-detector and that of the sensitive surface of the second photo-detector.[0040]
• According to the one aspect of the present invention, it is possible to extremely decrease a probability that, when the second light emitted in the second scintillator away from the second filter is propagated therein, the second light passes on the first filter so as to be absorbed therein.[0041]
• In preferred embodiment of this one aspect, the second scintillator has a substantially rectangular shape, and wherein the first photo-detector and the second photo-detector are arranged on both lateral sides of the second scintillator so that the first photo-detector is the most distant from the second photo-detector.[0042]
• According to the one aspect of the present invention, it is possible to extremely decrease a probability that, when the second light emitted in the second scintillator away from the second filter is propagated therein, the second light passes on the first filter so as to be absorbed therein.[0043]
• This one aspect of the present invention has an arrangement that the second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, the detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector, the first filter being adapted to transmit therethrough only the first light emitted from the first scintillator, the second filter being adapted to transmit therethrough only the second light emitted in the second scintillator, and wherein the first filter is arranged to be away from the back surface of the second scintillator at a predetermined interval so that an air layer is interposed between the back surface of the second scintillator and the first filter, and the second filter is closely optically adhered on the back surface of the second scintillator.[0044]
• According to the one aspect of the present invention, it is possible to, when the second light emitted in the second scintillator away from the second filter is propagated therein, prevent the second light from passing on the first filter so as to get rid of the absorbing function of the second light by the first filter.[0045]
• In preferred embodiment of this one aspect, the second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, the detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector, the first filter being adapted to transmit therethrough only the first light emitted from the first scintillator, the second filter being adapted to transmit therethrough only the second light emitted in the second scintillator, and wherein the first filter is arranged to be away from the back surface of the second scintillator at a predetermined interval, and the second filter is closely optically adhered on the back surface of the second scintillator, further comprising a surrounding box having an inner surface portion for surrounding a back surface side of the second scintillator so as to form a closed space therein, the back surface of the second scintillator and the first filter forming parts of the inner surface portion of the surrounding box, the inner surface portion of the surrounding box except for the back surface of the second scintillator and the first filter being processed to totally internally reflect diffusely the first light emitted from the first scintillator.[0046]
• According to the one aspect of the present invention, it is possible to get rid of a bad influence of the first filter with respect to the second light incident through the second filter into the second photo-detector and to increase a probability that the first light emitted from the first scintillator and transmitted through the second scintillator is diffusely reflected to be detected through the first filter by the first photo-detector.[0047]
• In preferred embodiment of this one aspect, the inner surface portion comprises a plurality of inner surfaces, each of the inner surfaces is inclined so that the diffusely reflecting directions on average of the first light on the inner surfaces of the surrounding box are substantially directed to a position of the second scintillator at which a center axis of the sensitive surface of the first photo-detector is crossed.[0048]
• According to the one aspect of the present invention, it is possible to get rid of a bad influence of the first filter with respect to the second light incident through the second filter into the second photo-detector, and to reflect on average the first light emitted from the first scintillator and transmitted through the second scintillator toward a position of the second scintillator at which a center axis of the sensitive surface (first filter) of the first photo-detector is crossed, thereby increasing the probability that the first light is detected by the first photo-detector as compared with the first light which is uniformly distributed in the closed space.[0049]
• This one aspect of the present invention further has a light guide in which the first light emitted from the first scintillator and the second light emitted in the second scintillator are incident, the light guide being adapted to condense the first and second lights on the detection means, and wherein the detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector, the first filter being adapted to transmit therethrough only the first light emitted from the first scintillator, the second filter being adapted to transmit therethrough only the second light emitted in the second scintillator.[0050]
• According to the one aspect of the present invention, the first and second lights having different wavelength bands are filled to be diffused in the light guide in a state of being mixed, and then, is propagated to the first and second photo-detectors. The first filter is mounted on the sensitive surface of the first photo-detector and the second filter is mounted on the sensitive surface of the second photo-detector. Because the first filter is adapted to transmit therethrough only the first light emitted from the first scintillator and the second filter is adapted to transmit therethrough only the second light emitted in the second scintillator, it is possible to independently detect the first and second lights corresponding to the first and second radiations without using a specific electronic equipment for discrimination and identification.[0051]
• In preferred embodiment of this one aspect, the first filter is arranged to be away from the back surface of the second scintillator at a predetermined interval, and the second filter is closely optically adhered on the back surface of the second scintillator, and wherein the light guide has an opening surface opposite to the back surface of the second scintillator, the light guide being arranged so that the opening surface thereof being away from the back surface of the second scintillator at a predetermined interval so as to interpose an air layer between the opening surface of the light guide and the back surface of the second scintillator, the opening surface thereof having an area which is larger than that of the first filter.[0052]
• According to the one aspect of the present invention, it is possible to get rid of a bad influence of the first filter with respect to the second light incident through the second filter into the second photo-detector. Moreover, since the first light emitted from the first scintillator and transmitted through the second scintillator is incident in the light guide so as to be guided through the first filter into the first photo-detector, it is possible to increase a probability that the first light is detected by the first photo-detector.[0053]
• This one aspect of the present invention further has a light guide connecting the at least one photo-detector to an edge portion of the second scintillator, the light guide being adapted to convert the second light to a fluorescent light.[0054]
• In the case of the one aspect of the present invention, an air is interposed between the first and second scintillators. Since the first scintillator is composed of, for example, a powder and a sintering substance or the like, a diffuse reflection is made in the first scintillator so that the diffusely reflected first light is emitted outside, thereby being once transmitted through the second scintillator, and thereafter, is filled in the condensing box. The first light filled in the condensing box is detected by means of, for example, a first photo-detector arranged in the condensing box. A component of the second light from the second scintillator is incident upon the condensing box; however, the second light is eliminated by, a filter provided on the first photo-detector.[0055]
• The second scintillator is surrounded by an air; for this reason, the second light is confined in the second scintillator by a total internal reflection effect. As a result, a scintillation light is condensed on the edge portion of the second scintillator with a high density. The second scintillator is provided at the edge portion side of the second scintillator with the light guide containing a fluorescent substance of absorbing a scintillation photon and emitting a fluorescent light having a longer wavelength as compared with the second light, and thereby, a re-emission light occurs by a fluorescence conversion in the second scintillator. Since the re-emitted light is propagated while being totally internally reflected in the light guide, it is possible to detect a fluorescence light induced by re-emitted scintillation light by means of the photo-detector arranged on the end side of the light guide. Incidentally, the light guide may includes an optical fiber having a clad (referred to a fluorescence fiber, a wavelength shift fiber or the like).[0056]
• In the condensing system on the edge side of the second scintillator, it is possible to condense the second light without depending upon an area of the second scintillator; and therefore, it is easy to apply the invention to a large-area scintillator together with the condensing box.[0057]
• In preferred embodiment of this one aspect, the second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, further comprising a fluorescent screen arranged on a back surface side of the second scintillator and opposite through an air layer to the back surface thereof, the fluorescent screen being adapted to convert the first light emitted from the first scintillator to a fluorescent light; and a light guide adapted to condense the converted fluorescent light on the at least one photo-detector, the converted fluorescent light being emitted from a surface of the fluorescent screen, the at least one photo-detector detecting the condensed fluorescent light.[0058]
• According to the one aspect of the present invention, the first light from the first scintillator is transmitted through the second scintillator so as to be absorbed in the fluorescent screen, so that a re-emission of the fluorescence having a longer wavelength as compared with the second light is generated in the fluorescent screen. The re-emitted light is guided to the photo-detector via the light guide. Whereby it is possible to detect the fluorescence light induced by the first light.[0059]
• In preferred embodiment of this one aspect, the second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, further comprising a fluorescent screen arranged on a back surface side of the second scintillator and opposite through an air layer to the back surface thereof, the fluorescent screen being adapted to convert the first light emitted from the first scintillator to a fluorescent light; and a second light guide having a fluorescent substance adapted to absorb the converted fluorescent light so as to emit a fluorescent light, the converted fluorescent light by the fluorescent screen being emitted from an edge portion of the fluorescent screen, the fluorescent light emitted from the light guide having a wavelength which is longer than that of the converted fluorescent light by the fluorescent screen, the at least one photo-detector detecting the fluorescent light emitted from the second light guide.[0060]
• According to the one aspect of the present invention, the first light from the first scintillator is transmitted through the second scintillator so as to be absorbed in the fluorescent screen so that a re-emission of the fluorescence having a longer wavelength is generated in the fluorescent screen. In this case, since the fluorescent screen is surrounded by an air, the first light is captured by the total internal reflection similarly to the second scintillator, and then, a fluorescence light is collected on the edge portion side of the fluorescent screen with a high density. Furthermore, since the fluorescent screen is provided with the second light guide for absorbing the fluorescent light generated in the fluorescent screen so as to emit a fluorescence light having a longer wavelength as compared with the fluorescent light generated in the florescence screen, it is possible to condense the emitted fluorescent light by a fluorescence conversion from the edge portion side of the fluorescent screen similarly to the second scintillator. Since the second light guide is provided at the edge portion of the second light guide with the photo-detector, it is possible to detect the first light of the first scintillator as a light which is double converted into a fluorescent light.[0061]
• The one aspect of the present invention further has means for capturing a signal outputted from the detection means so as to recognize a signal having a predetermined pulse height value and over as an optical signal thereby eliminating a signal less than the predetermined pulse height value as a noise, the optical signal corresponding to at least one of the first and second lights emitted from the first and second scintillators.[0062]
• According to the one aspect of the present invention, a signal outputted from the detection means is captured so that a signal having a predetermined pulse height value and over is recognized as an optical signal. On the other hand, a signal less than the predetermined pulse height value is eliminated as a noise.[0063]
• In preferred embodiment of this one aspect, the detection means comprises a plurality of photo-detectors, a first group of the photo-detectors being adapted to detect the first light emitted from the first scintillator, a second group thereof being adapted to detect the second light emitted from the second scintillators, further comprising means for capturing signals outputted each of the first and second groups of the photo-detectors and, in a case of detecting signals outputted from at least one of the first and second groups of the photo-detectors, for recognizing detected signals corresponding to at least one of the first and second lights emitted from the first and second scintillators and, in a case where only one signal is outputted from at least one of the first and second groups of the photo-detectors, for eliminating the only one signal as a noise.[0064]
• According to the one aspect of the present invention, the first lights are detected by the first group of the photo-detectors and the second lights are detected by the second group thereof. Each signal of each of the first and second groups of the photo-detectors is captured by the capturing means so that, in the case where signals outputted from at least one of the first and second groups of the photo-detectors are detected, it is recognized that the detected signals correspond to the first and second lights emitted from the first and second scintillators and, in a case where only one signal is outputted from at least one of the first and second groups of the photo-detectors, the signal is eliminated as a noise.[0065]
• This one aspect of the present invention further has an optical attenuation filter for transmitting therethrough the first and second radiations and attenuating an intensity of the first light emitted from the first scintillator, the optical attenuation filter being interposed between the first and second scintillators; a condensing box for condensing the first and second lights on the detection means, the condensing box having an inner surface for diffusely reflecting the first and second lights; and means for inputting signals detected by the detection means so as to discriminate, according to a difference of waveforms of the inputted signals, between an optical signal corresponding to the first light emitted from the first scintillator and an optical signal corresponding to the second light emitted from the second scintillator.[0066]
• The one aspect of the present invention further has an optical attenuation filter for transmitting therethrough the first and second radiations and attenuating an intensity of the first light emitted from the first scintillator, the optical attenuation filter being interposed between the first and second scintillators; a light guide in which the first light emitted from the first scintillator and the second light emitted in the second scintillator are incident, the light guide being adapted to condense the first and second lights on the detection means; and means for inputting signals outputted from the detection means so as to discriminate, according to a difference of waveforms of the inputted signals, between an optical signal corresponding to the first light emitted from the first scintillator and an optical signal corresponding to the second light emitted from the second scintillator.[0067]
• In accordance with the one aspect of the present invention, the first and second radiations are transmitted through the optical attenuation so that the intensity of the first light is attenuated. The signals detected by the detection means are inputted to the discriminating means so that the detected signals are discriminated, according to a difference of waveforms of the inputted signals, between the optical signal corresponding to the first light emitted from the first scintillator and the optical signal corresponding to the second light emitted from the second scintillator.[0068]
BRIEF DESCRIPTION OF THE DRAWINGS
• Other objects and aspects of the present invention will become apparent from the following description of embodiments with reference to the accompanying drawings in which:[0069]
• FIG. 1 is an elevational view partially in section showing a radiation detecting apparatus according to a first embodiment of the present invention;[0070]
• FIG. 2 is an elevational view partially in section showing a radiation detecting apparatus according to a second embodiment of the present invention;[0071]
• FIG. 3 is an elevational view partially in section showing a radiation detecting apparatus according to a third embodiment of the present invention;[0072]
• FIG. 4A is an elevational view partially in section showing a radiation detecting apparatus according to a fourth embodiment of the present invention;[0073]
• FIG. 4B is a plan view of the radiation detecting apparatus shown in FIG. 4A in the case of viewing the radiation detecting apparatus from an incident side of radiations;[0074]
• FIG. 5A is an elevational view partially in section showing a radiation detecting apparatus according to a fifth embodiment of the present invention;[0075]
• FIG. 5B is a plan view of the radiation detecting apparatus shown in FIG. 5A in the case of viewing the radiation detecting apparatus from an incident side of radiations.[0076]
• FIG. 6A is an elevational view partially in section showing a radiation detecting apparatus according to a sixth embodiment of the present invention;[0077]
• FIG. 6B is a plan view of the radiation detecting apparatus shown in FIG. 6A in the case of viewing the radiation detecting apparatus from an incident side of radiations;[0078]
• FIG. 6C is a plan view of the radiation detecting apparatus shown in FIG. 6A in the case of viewing the radiation detecting apparatus from an incident side of radiations according to a modification of the sixth embodiment;[0079]
• FIG. 7 is an elevational view partially in section showing a radiation detecting apparatus according to a seventh embodiment of the present invention;[0080]
• FIG. 8A is an elevational view partially in section showing a radiation detecting apparatus according to an eighth embodiment of the present invention;[0081]
• FIG. 8B is a cross sectional view taken on line VIII-VIII in FIG. 8A;[0082]
• FIG. 9A is an elevational view partially in section showing a radiation detecting apparatus in the case of viewing the radiation detecting apparatus from a lateral side of first and second scintillators thereof according to a ninth embodiment of the present invention;[0083]
• FIG. 9B is an elevational view partially in section showing a radiation detecting apparatus in the case of viewing the radiation detecting apparatus from a longitudinal side of the first and second scintillators thereof according to the ninth embodiment;[0084]
• FIG. 10A is an elevational view partially in section showing a radiation detecting apparatus according to a tenth embodiment of the present invention;[0085]
• FIG. 10B is a plan view of the radiation detecting apparatus shown in FIG. 10A in the case of viewing the radiation detecting apparatus from an incident side of radiations;[0086]
• FIG. 11 is an elevational view partially in section showing a radiation detecting apparatus according to an eleventh embodiment of the present invention;[0087]
• FIG. 12 is an elevational view partially in section showing a radiation detecting apparatus according to a twelfth embodiment of the present invention;[0088]
• FIG. 13 is a plan view showing a second scintillator in FIG. 12;[0089]
• FIG. 14 is an elevational view partially in section showing a radiation detecting apparatus according to a thirteenth embodiment of the present invention;[0090]
• FIG. 15 is an elevational view partially in section showing a radiation detecting apparatus according to a fourteenth embodiment of the present invention;[0091]
• FIG. 16 is a view schematically showing a radiation detecting system according to a fifteenth embodiment of the present invention;[0092]
• FIG. 17 s a view schematically showing a radiation detecting system according to a sixteenth embodiment of the present invention;[0093]
• FIG. 18 is a view showing a radiation detecting system according to a seventeenth embodiment of the present invention;[0094]
• FIG. 19 is a view showing a radiation detecting system according to an eighteenth embodiment of the present invention;[0095]
• FIG. 20 is a view showing a phoswich detecting apparatus as a conventional example of a radiation detecting apparatus; and[0096]
• FIG. 21 is a view showing, as another conventional example, an α-β rays detecting apparatus.[0097]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Embodiments of the present invention will be described hereinafter according to FIGS.[0098]1 to19. It is noted that same or equivalent elements are denoted by the same or similar reference numerals throughout the drawings and that repetition descriptions of the elements are omitted or simplified.
First Embodiment (FIG.1)
• This first embodiment relates to a radiation detecting apparatus, and FIG. 1 is an elevational view partially in section showing a structure of the radiation detecting apparatus.[0099]
• As shown in FIG. 1, a[0100]radiation detecting apparatus11 according to this first embodiment comprises acase13 having, for example, a substantially box-like shape. Thecase13 is provided with an incident surface (upper surface in FIG. 1) on which radiations having different wavelengths, such as α and β rays are incident. The incident surface of thecase13 is formed with alight shielding film12 capable of transmitting the α and β rays therethrough and shielding an incidence of light. Theradiation detecting apparatus11 also comprises afirst scintillator14 which is sensitive to an α ray and has, for example, a substantially plate-like and rectangular shape.
• The[0101]first scintillator14 has an incident surface on which the α ray and a β ray are incident (an upper surface in FIG. 1) and a back surface (lower surface in FIG. 1) opposite to the incident surface thereof. Thefirst scintillator14 is arranged on the inner side of thelight shielding film12 so that the incident surface of thefirst scintillator14 is in parallel with a back surface (lower surface, inner surface in FIG. 1) of thelight shielding film12 opposite to the incident surface thereof. As described above, thefirst scintillator14 and thesecond scintillator15 are arranged in parallel with each other so that thefirst scintillator14 and thesecond scintillator15 have a two-layer structure.
• Furthermore, the[0102]radiation detecting apparatus11 comprises asecond scintillator15 which is sensitive to a β ray and has, for example, a substantially plate-like and rectangular shape.
• The[0103]second scintillator15 has an incident surface (an upper surface in FIG. 1) on which the β ray is incident and a back surface (lower surface in FIG. 1). Thesecond scintillator15 is arranged inwardly in thecase13 so that the incident surface of thesecond scintillator15 is in parallel with the back surface of thefirst scintillator14 whereby thesecond scintillator15 is located away from thefirst scintillator14 at a predetermined distance (interval).
• The[0104]radiation detecting apparatus11 also comprises an air which exists in thecase13 so that anair layer16 is formed between the first andsecond scintillators14 and15.
• In addition, the[0105]radiation detecting apparatus11 comprises one or more photo-detector17 arranged in thecase13 at a lower position opposite to thelight shielding film12 side (inner bottom surface side of thecase13 in FIG. 1). Theradiation detecting apparatus11 is also provided with a condensingunit18 interposed between thesecond scintillator15 and the photo-detector17 so that lights emitted from the first andsecond scintillators14 and15 are condensed by means of the condensingunit18 so as to be guided onto a sensitive surface of the photo-detector17 which is sensitive to the lights.
• As the[0106]first scintillator14 for α ray, ZnS (Ag), ZnCdS (Ag) or Gd₂O₂S and Y₂O₂S powder to which Tb, Eu, Pr are added, are used. As thesecond scintillator15 for β ray, a thin plastic scintillator or a thin scintillator made of other similar materials, which is capable of detecting the a and β rays while suppressing a γ-ray sensitivity and of transmitting therethrough the light emitted from thefirst scintillator14 is permitted to be used. For example, the plastic scintillator has a thickness of approximately 1 mm. In this case, the thickness of the second scintillator is determined by taking account of a quantity of emission required for a photo-detector system including the photo-detector17, a target β-ray energy, a γ-ray sensitivity or the like, so that the thickness of the second scintillator is differently set depending upon the usage.
• In addition, all peripheral surfaces of the[0107]second scintillator15 are optically polished.
• This first embodiment includes the following two characteristic structures; more specifically,[0108]
• (1) an emission center wavelength (first emission center wavelength λ1) of the[0109]first scintillator14 is set shorter than an emission center wavelength (second emission center wavelength λ2) of the second scintillator15 (first characteristic structure); and
• (2) conversely, the first emission center wavelength λ1 of the[0110]first scintillator14 is set longer than the second emission center wavelength λ2 of the second scintillator15 (second characteristic structure).
• Then, the expression “emission center wavelength of a scintillator” used herein is employed to mean “wavelength of the emission (light) which is emitted in the scintillator and has the peak emission intensity in the emission wavelength band of the scintillator”.[0111]
• That is, the first emission center wavelength λ1 of the[0112]first scintillator14 means “wavelength of the emission (light) which is emitted in thefirst scintillator14 and has the peak emission intensity in the emission wavelength band of thefirst scintillator14”, and the second emission center wavelength λ2 of the second scintillator means “wavelength of the emission (light) which is emitted in thesecond scintillator15 and has the peak emission intensity in the emission wavelength band of thesecond scintillator15”. In these first and second characteristic structures, that is, in mutual relationships between the long and short wavelengths λ1 and λ2 of the first andsecond scintillators14 and15, there are individual features. Either of the first and second characteristics is able to be selectively used in relation to a balance of the accompanying condensing unit, a light transmission characteristic of each scintillator, the maximum sensitivity wavelength of the photo-detector, a quantum efficiency or the like.
• According to the aforesaid structure, because the air (air layer[0113]16) is interposed between the first andsecond scintillators14 and15, the surrounding of thesecond scintillator15 is surrounded by the air having a refractive index lower than that of thesecond scintillator15 itself so that it is easy to confine in thesecond scintillator15 the light emitted therein. As a result, it is easy to employ, as the condensing unit with respect to thesecond scintillator15, a method of using the light highly densely condensed on an edge side in thesecond scintillator15. Incidentally, this method will be described in the later embodiment.
• According to the above structure of this first embodiment, unlike the conventional structure, it is possible to dispense with an intermediate substance for bonding and optically closely coupling the first and second scintillators so that the above structure is suitable for the case where there is a fear of a deterioration in quantity of the intermediate substance itself or another deterioration in quantity of a chemical interaction between the intermediate substance and the scintillators or the like. Furthermore, each independence of the[0114]scintillators14 and15 is secured, making it possible to carry out maintenance, inspection and replacement of only one of the scintillators.
• In the aforesaid first characteristic structure, because the first emission center wavelength λ1 of the[0115]first scintillator14 is set shorter than the second emission center wavelength λ2 of thesecond scintillator15, the emission wavelength band of thefirst scintillator14 and that of thesecond scintillator15 are substantially separated so that it is possible to use together means for optically identifying the emission wavelengths of the lights emitted in the first andsecond scintillators14 and15, thereby dispensing the waveform discrimination processing unit for analyzing pulse rises.
• Moreover, in the aforesaid second characteristic structure, the first emission center wavelength λ1 of the[0116]first scintillator14 is set longer than the second emission center wavelength λ2 of thesecond scintillator15, and thereby, in general, a light having a long wavelength and emitted from thefirst scintillator14 having a high transmission efficiency in the scintillator is hard to be absorbed in thesecond scintillator15. Therefore, it is possible to make small a probability of receiving absorption and emission by a fluorescent substance contained in thesecond scintillator15, thus to prevent an influence of the light emitted from thefirst scintillator14 with respect to thesecond scintillator15.
• As described above, according to the first embodiment, since the first and second scintillators having first and second different emission center wavelengths λ1 and λ2 are formed to have the two-layer structure, there is no need of measuring pulse height distributions based on the emissions from the first and second scintillators, making it possible to simultaneously and independently measure the α ray and the β ray with the use of the difference in their wavelengths.[0117]
• Moreover, in this first embodiment, powder is used as the[0118]first scintillator14, and for example, the powder may be applied to be fixed to the back surface of thelight shielding film12, that is, an inner surface of thelight shielding film12 facing thesecond scintillator15 side. Whereby the α ray transmitted through thelight shielding film12 is incident upon thefirst scintillator14 without being incident upon an extra air layer so as to be emitted in thefirst scintillator14. In addition, because thefirst scintillator14 is fixed on the back surface of thelight shielding film12, theair layer16 is interposed between the first andsecond scintillators14 and15.
• As a result, because there is a difference between the refractive index of the[0119]second scintillator15 and that of air so that the difference causes a light capture effect by the total internal reflection of the emitted light in thesecond scintillator15. Thus, the emitted light in thesecond scintillator15 is confined in thesecond scintillator15 itself so as to be propagated therein, making it possible to condense on the side of thesecond scintillator15 the light propagated therein with a high density.
Second Embodiment (FIG.2)
• FIG. 2 is an elevational view partially in section showing a radiation detecting apparatus according to a second embodiment of the present invention.[0120]
• In this second embodiment, similar to the first embodiment, a[0121]radiation detecting apparatus11A includes thecase13 whose one surface (incident surface) is covered with thelight shielding film12 capable of transmitting an α ray and a β ray therethrough and shielding an incidence of light. In thecase13, thefirst scintillator14 emitting a light by an α ray and thesecond scintillator15 emitting a light by a β ray are arranged in a state of being closely optically coupled (adhered) without interposing an air layer between thesescintillators14 and15.
• That is, the back surface of the[0122]first scintillator14 and the incident surface of thesecond scintillator15 are closely and optically adhered with each other.
• Furthermore, in the[0123]case13, a condensingunit18 is provided in combination with these first andsecond scintillator14 and15 so as to effectively condense the lights emitted from each of the first andsecond scintillators14 and15 to a photo-detector17.
• Similar to the first embodiment, this second embodiment includes the following two characteristic structures; more specifically,[0124]
• (1) the first emission center wavelength λ1 of the[0125]first scintillator14 is set shorter than the second emission center wavelength λ2 of the second scintillator15 (first characteristic structure); and
• (2) conversely, the first emission center wavelength λ1 of the[0126]first scintillator14 is set longer than the second emission center wavelength λ2 of the second scintillator15 (second characteristic structure).
• In accordance with their individual features of mutual relationships between the long and short wavelengths λ1 and λ2 of the first and[0127]second scintillators14 and15, either of the first and second characteristics is able to be selectively employed in relation to a balance of the accompanying condensing unit, a light transmission characteristic of each scintillator, the maximum sensitivity wavelength of the photo-detector, a quantum efficiency or the like.
• According to this second embodiment, the first and[0128]second scintillators14 and15 are optically closely adhered with each other, thereby making it possible to reduce an internal capture by a Fresnel reflection based on a difference in refractive indexes of thesecond scintillator15 and an interposed air layer and by a total internal reflection in thesecond scintillator15, so as to improve a transmission probability of the light emitted from thefirst scintillator14 through thesecond scintillator15. Therefore, it is easy to employ a condense unit having a condensing method of using a light from the back surface of thesecond scintillator15 which is not adhered to thefirst scintillator14.
• As described above, since the first and second scintillators having first and second different emission center wavelengths λ1 and λ2 are formed to have a two-layer structure, there is no need of measuring pulse height distributions based on the emissions from the first and second scintillators, thereby making it possible to simultaneously and independently measure the α ray and the β ray with the use of the difference in their wavelengths.[0129]
• Incidentally, this second embodiment is suitable for the case of applying the condensing unit based on a concept such that the emission lights from the respective first and[0130]second scintillators14 and15 are once mixed, and thereafter, optically or electrically separated. Conversely, the first embodiment is suitable for the case of applying the condensing unit based on a concept such that the emission lights from respective first andsecond scintillators14 and15 are not made into a state of being mixed as much as possible.
Third Embodiment (FIG.3)
• FIG. 3 is an elevational view partially in section showing a radiation detecting apparatus according to a third embodiment of the present invention.[0131]
• In the[0132]radiation detecting apparatus11B of this third embodiment, a condensingunit18 is formed as acondensing box19 which is served as acase13, and aninner surface19aof thecondensing box19 is a diffuse reflection surface onto which a diffuse reflection material is applied. One surface of thecondensing box19 is opened so as to be used as an incident port. To the incident port, alight shielding film12 is mounted for transmitting therethrough an α ray and a β ray while shielding light from the outside.
• The[0133]condensing box19 is provided with a scintillator layer20 which has a two-layer structure comprising the same first andsecond scintillators14 and15 as the aforesaid first or second embodiment, on the back side of thelight shielding film12. Lights emitted from the first andsecond scintillators14 and15 as the scintillator layer20 are diffusely reflected by theinner surface19aof thecondensing box19 so as to be mixed, thereby being filled therein.
• Inside of the[0134]condensing box19, two photo-detectors17 (first and second photo-detectors17a,17b) are arranged in a line on the backside of the scintillator layer20. A photo-multiplier tube is permitted to be used as each photo-detector17. The first photo-detector17ais provided with a sensitive surface to which afirst filter21ais mounted. Thefirst filter21ais adapted to transmit therethrough only light having the first emission wavelength band including the first emission center wavelength λ1 of thefirst scintillator14 from the mixed and filled light.
• On the other hand, the second photo-[0135]detector17bis provided with a sensitive surface to which asecond filter21bis mounted. Thesecond filter21bis adapted to transmit therethrough only light having a second emission wavelength band including the second emission center wavelength λ2 of thesecond scintillator15 from the mixed and filled light.
• That is, because the light emitted from the[0136]first scintillator14 is not transmitted through thesecond filter21bof the photo-detector17b,the light emitted from thefirst scintillator14 and filled in thecondensing box19 is transmitted only through thefirst filter21aof the photo-detector17aso as to be detected thereby, so that a signal based on the emitted light from thefirst scintillator14 is outputted only from the photo-detector17a.
• Similarly, because the light emitted from the[0137]second scintillator15 is not transmitted through thefirst filter21aof the first photo-detector17a,the light emitted from thesecond scintillator15 and filled in thecondensing box19 is transmitted only through thesecond filter21bof the second photo-detector17bso as to be detected thereby, so that a signal based on the emitted light from thesecond scintillator15 is outputted only from the photo-detector17b.
• Namely, in this third embodiment, the optical wavelength discrimination is carried out so that independent signals are outputted from the individual photo-[0138]detectors17aand17bwithout using a special separating circuit.
• According to the above structure, two lights having the first and second wavelength bands which are substantially separated from each other are diffusely reflected to the[0139]inner surface19aof thecondensing box19 so as to be mixed and filled therein, differently from the aforesaid first and second embodiments in which each light emitted from each of the first andsecond scintillators14 and15 is transmitted on the back surface side of thesecond scintillator15 which does not face to thefirst scintillator14 side.
• Therefore, since the[0140]first filter21afor transmitting therethrough only light emitted from thefirst scintillator14 is mounted to the first individual photo-detector17aarranged in thecondensing box19 and thesecond filter21bfor transmitting therethrough only light emitted from thesecond scintillator15 is mounted to the second individual photo-detector17barranged in thecondensing box19, it is possible to individually detect each of the emitted lights based on each of the α and β rays without using a specific electronic device for discrimination and identification of the emitted lights. In addition, since the condensing box is used, it is easy to be applicable to scintillators each having a large area.
• Thus, in this third embodiment, as described above, the first and second scintillators are made into a two-layer structure so that there is no need of measuring pulse height distributions and carrying out a waveform discrimination, making it possible to simultaneously and independently measure the α ray and the β ray with the use of the difference in their wavelengths, and to provide a radiation detecting apparatus including scintillators each having large area.[0141]
Fourth Embodiment (FIGS.4A,4B)
• FIG. 4A is an elevational view partially in section showing a radiation detecting apparatus according to a fourth embodiment of the present invention. FIG. 4B is a plan view of the radiation detecting apparatus shown in FIG. 4A in the case of viewing the radiation detecting apparatus from an incident side of radiations.[0142]
• In the[0143]radiation detecting apparatus11C of this fourth embodiment, since the structures of thecase13, thelight shielding film12, thefirst scintillator14 and thesecond scintillator15 are the same with those of the radiation detecting apparatus of the first embodiment, descriptions of the structures of thecase13, thelight shielding film12, thefirst scintillator14 and thesecond scintillator15 are omitted or simplified.
• The[0144]radiation detecting apparatus11C of the fourth embodiment comprises two photo-detectors25 (first and second photo-detectors25a,25b) mounted in thecase13 on the backside of thesecond scintillator15. A photo-multiplier tube is permitted to be used as each photo-detector25.
• The first and second photo-[0145]detectors25aand25bare arranged in parallel with a longitudinal direction of thesecond scintillator15 and located away from each other at a predetermined interval.
• The first photo-[0146]detector25aof the photo-detectors25 is provided with a sensitive surface to which afirst filter26ahaving a predetermined color (for example, red) is integrally mounted. The sensitive surface of the first photo-detector25aand thefirst filter26ahave, for example, a substantially circular shape so that thefirst photo detector25aand thefirst filter26aare coaxially arranged.
• The[0147]first filter26aof the first photo-detector25ais optically closely adhered to the back surface of thesecond scintillator15.
• The[0148]first filter26ais adapted to transmit therethrough only light emitted from thefirst scintillator14 and to absorb therein light emitted from thesecond scintillator15.
• Similarly, the second photo-[0149]detector25bof the photo-detectors25 is provided with a sensitive surface to which asecond filter26bhaving a predetermined color (for example, blue) is integrally mounted. The sensitive surface of the second photo-detector25band thesecond filter26bhave, for example, a substantially circular shape so that thesecond photo detector25band thesecond filter26bare coaxially arranged.
• The[0150]second filter26bof the second photo-detector25bis optically closely adhered to the back surface of thesecond scintillator15.
• The[0151]second filter26bis adapted to transmit therethrough only light emitted in thesecond scintillator15 and to absorb therein light emitted from thefirst scintillator14.
• The[0152]radiation detecting apparatus11C also comprises an air which exists in thecase13 so that anair layer27 is formed thereby surrounding thesecond filter15.
• According to the above structure, because the light emitted from the[0153]first scintillator14 is not transmitted through thesecond filter26bof the photo-detector25bto be absorbed therein, the light emitted from thefirst scintillator14 is transmitted only through thefirst filter26aof the photo-detector25aso as to be detected by the photo-detector25a,so that a signal based on the emitted light from thefirst scintillator14 is outputted only from the photo-detector25a.
• Similarly, because the light emitted from the[0154]second scintillator15 is not transmitted through thefirst filter25aof the photo-detector26ato be absorbed therein, the light emitted from thesecond scintillator15 is transmitted only through thesecond filter26bof the photo-detector25bso as to be detected by the photo-detector25b,so that a signal based on the emitted light from thesecond scintillator15 is outputted only from the photo-detector25b.
• Particularly, because the[0155]second scintillator15 is surrounded by theair layer27 having the refractive index which is lower than that of thesecond scintillator15 itself, as shown in FIGS. 4A and 4B, the light L2 emitted in thesecond scintillator15 is totally internally reflected on the surroundingair layer27 so as to be diffused in thesecond scintillator15 while being captured therein.
• Because the light L[0156]2 emitted in thesecond scintillator15 is diffused while being captured therein, the light L2aemitted at a portion in thesecond scintillator15 close to thesecond filter26bis directly incident into thesecond filter26band, in the case where the light L2bis emitted at a position in thesecond scintillator15 away from thesecond filter26b,the emitted light L2bis efficiently propagated to be incident into thesecond filter26b.
• Therefore, it is possible to efficiently detect the light L[0157]2 emitted in thesecond scintillator15 by the second photo-detector25b.
Fifth Embodiment (FIGS.5A to5C)
• FIG. 5A is an elevational view partially in section showing a radiation detecting apparatus according to a fifth embodiment of the present invention. FIG. 5B is a plan view of the radiation detecting apparatus shown in FIG. 5A in the case of viewing the radiation detecting apparatus from an incident side of radiations.[0158]
• In the structure of the[0159]radiation detecting apparatus11C according to the fourth embodiment, the first and second photo-detectors25aand25bare arranged in parallel with the longitudinal direction of thesecond scintillator15 and located away from each other at a predetermined interval.
• Therefore, there is the probability that, while the light L[0160]2 emitted at one side portion (a left side portion as one faces in FIG. 4A) in thesecond scintillator15 away from thesecond filter26bis propagated in thesecond scintillator15 toward thesecond filter26b,the light L2 passes through a portion of thesecond scintillator15 on which thefirst filter26ais contacted so as to be absorbed in thefirst filter26a.Therefore, there is the possibility that the efficiency of detecting the light emitted at the one side portion in the second scintillator away from thesecond filter26bis deteriorated whereby decreasing the uniformity of the sensitivity of the radiation detecting apparatus.
• However, in this fifth embodiment, by devising the arrangement of the two photo-detectors including the filters it is possible to improve the efficiency of detecting the light emitted at the one side portion in the second scintillator away from the second filter and to improve the uniformity of the sensitivity of the radiation detecting apparatus.[0161]
• In view of the aforesaid circumstances with respect to the structure of the radiation detecting apparatus according to the fourth embodiment, the[0162]radiation detecting apparatus11D of this fifth embodiment has a characteristic structure in that, in the case where a first center point of thefirst filter26a(the sensitive surface of the first photo-detector25a) of theradiation detecting apparatus11D is referred as O1 and a second center point of thesecond filter26b(the sensitive surface of the second photo-detector25b) thereof is referred as O2, the first photo-detector25aintegrally including thefirst filter26aand the second photo-detector25bintegrally including thesecond filter26bare adjacently arranged so that a line M1 connecting the first center point O1 and the second center point O2 is orthogonal to the longitudinal direction of thesecond scintillator15.
• Incidentally, other structures of the[0163]radiation detecting apparatus11D of this fifth embodiment is substantially the same as the structures of theradiation detecting apparatus11C of the fourth embodiment, and therefore, the descriptions about the other structures of theradiation detecting apparatus11D are omitted.
• In this fifth embodiment, the light L[0164]2bemitted at one side portion (a left side portion as one faces in FIGS. 5A and 5B) in thesecond scintillator15 away from thesecond filter26bis propagated in thesecond scintillator15 toward thesecond filter26bwhile being totally internally reflected on theair layer27.
• Then, because the first photo-[0165]detector25aincluding thefirst filter26aand the second photo-detector25bincluding thesecond filter26bare arranged so that the line M1 connecting the first center point O1 and the second center point O2 is orthogonal to the longitudinal direction of thesecond scintillator15, the probability that the light L2bpasses on thefirst filter26ais decreased as compared with the fourth embodiment so that it is possible to improve the efficiency of detecting the light L2 emitted in thesecond scintillator15.
• Therefore, it is possible to efficiently detect the light L[0166]2 emitted in thesecond scintillator15 by the second photo-detector25b.
• Incidentally, in this fifth embodiment, the first photo-[0167]detector25aincluding thefirst filter26aand the second photo-detector25bincluding thesecond filter26bare arranged so that the line M1 connecting the first center point O1 and the second center point O2 is orthogonal to the longitudinal direction of thesecond scintillator15. However, the present invention is not limited to the structure. That is, as shown in FIG. 5C, the first photo-detector25aincluding thefirst filter26aand the second photo-detector25bincluding thesecond filter26bare arranged so that the line M2 connecting the first center point O1 and the second center point O2 may be crossed to the longitudinal direction of thesecond scintillator15 at a given angle. It is preferable that the given angle is set close to a right angle.
Sixth Embodiment (FIGS.6A to6C)
• FIG. 6A is an elevational view partially in section showing a radiation detecting apparatus according to a sixth embodiment of the present invention. FIG. 6B is a plan view of the radiation detecting apparatus shown in FIG. 6A in the case of viewing the radiation detecting apparatus from an incident side of radiations. Moreover, FIG. 6C is a plan view of the radiation detecting apparatus shown in FIG. 6A in the case of viewing the radiation detecting apparatus from an incident side of radiations according to a modification of the sixth embodiment.[0168]
• In view of the aforesaid circumstances with respect to the structure of the radiation detecting apparatus according to the fourth embodiment, the[0169]radiation detecting apparatus11E of this sixth embodiment has a characteristic structure in that the first photo-detector25aintegrally including thefirst filter26aand the second photo-detector25bintegrally including thesecond filter26bare arranged on both lateral end sides of thesecond scintillator15 at a predetermined interval so that the first photo-detector25ais the most distant from the second photo-detector25bin thecase13.
• That is, in the case where each lateral width of each of the first and[0170]second scintillators14,15 is substantially similar to each diameter of eachfilter26a,26b,as shown in FIG. 6B, thefirst filter26aintegrated with the first photo-detector25ais optically closely adhered to one side edge portion (a left side portion as one faces in FIGS. 6A and 6B) of thesecond scintillator15, and thesecond filter26bintegrated with the second photo-detector25bis optically closely adhered to other side edge portion of thesecond scintillator15.
• In the case where each lateral width of each of the first and[0171]second scintillators14,15 is longer than each diameter of eachfilter26a,26b,as shown in FIG. 6C, thefirst filter26aintegrated with the first photo-detector25ais optically closely adhered to one of corner portions of thesecond scintillator15 and thesecond filter26bintegrated with the second photo-detector25bis optically closely adhered to another one of the corner portions of thesecond scintillator15, wherein another one of the corner portions of thesecond scintillator15 is diagonally arranged to one of the corner portions thereof.
• Incidentally, other structures of the[0172]radiation detecting apparatus11E of this sixth embodiment is substantially the same as the structures of theradiation detecting apparatus11C of the fourth embodiment, and therefore, the descriptions about the other structures of theradiation detecting apparatus11E are omitted.
• In this sixth embodiment, the light L[0173]2b1 emitted at a portion except for the one side portion to which thefirst filter26ais adhered is propagated in thesecond scintillator15 toward thesecond filter26bwhile being totally internally reflected on theair layer27.
• Then, because the first photo-[0174]detector25aintegrally including thefirst filter26aand the second photo-detector25bintegrally including thesecond filter26bare arranged on both lateral sides of thesecond scintillator15 at a predetermined interval so that the first photo-detector25ais the most distant from the second photo-detector25bin thecase13, the probability that the emitted light L2b1 passes on thefirst filter26ais extremely decreased as compared with the fifth embodiment.
• Furthermore, in this structure, when the emitted light L[0175]2b1 is propagated to a portion to which thesecond filter26bis adhered, even if the emitted light L2b1 does not pass on thesecond filter26b,it is possible to prevent the emitted light L2b1 from being propagated to the portion to which thefirst filter26ais adhered. That is, by this arrangement of the first photo-detector25aincluding thefirst filter26aand the second photo-detector25bincluding thesecond filter26b,the propagating route of the light emitted from thefirst scintillator14 and that of the light emitted in thesecond scintillator15 are not interrupted with each other.
Seventh Embodiment (FIG.7)
• FIG. 7 is an elevational view partially in section showing a radiation detecting apparatus according to a seventh embodiment of the present invention.[0176]
• In view of the aforesaid circumstances with respect to the structure of the radiation detecting apparatus according to the fourth embodiment, the[0177]radiation detecting apparatus11F of this seventh embodiment has a characteristic structure in that thefirst filter26aof the first photo-detector25ais not optically adhered to the back surface of thesecond scintillator5. That is, thefirst filter26ais arranged so as to be away from the back surface of thesecond scintillator15 at a predetermined interval so that an air which exists in thecase13 whereby anair layer30 is formed between the back surface of thesecond scintillator15 and thefirst filter26aof the first photo-detector25a.
• Incidentally, other structures of the[0178]radiation detecting apparatus11F of this seventh embodiment is substantially the same as the structures of theradiation detecting apparatus11C of the fourth embodiment, and therefore, the descriptions about the other structures of theradiation detecting apparatus11F are omitted.
• In this structure, because the[0179]second scintillator15 is surrounded by the air layers27 and30 each having the refractive index which is lower than that of thesecond scintillator15 itself, the light L2 emitted in thesecond scintillator15 is totally internally reflected on the surrounding air layers27 and30 so as to be diffused in thesecond scintillator15 while being captured therein.
• Therefore, in the case where the light L[0180]2bis emitted at a position in thesecond scintillator15 away from thesecond filter26b,the emitted light L2bdoes not pass on thefirst filter26aof the first photo-detector25aso that the emitted light L2bis efficiently propagated to be ideally incident into thesecond filter26bwithout any influence of thefirst filter26a.
• Therefore, it is possible to efficiently detect the light L[0181]2 emitted in thesecond scintillator15 by the second photo-detector25b.
Eighth Embodiment (FIGS.8A,8B)
• FIG. 8A is an elevational view partially in section showing a radiation detecting apparatus according to an eighth embodiment of the present invention. FIG. 8B is a cross sectional view taken on line VIIIB-VIIIB in FIG. 8A.[0182]
• In view of the aforesaid circumstances with respect to the structure of the radiation detecting apparatus according to the fourth embodiment, the[0183]radiation detecting apparatus11G of this eighth embodiment further comprises a reflectingbox31 attached to thesecond scintillator15 for totally internally reflecting diffusely the emitted light from thefirst scintillator14.
• Incidentally, in this embodiment, the[0184]light shielding file12 and thecase13 are omitted in FIG. 7.
• The reflecting[0185]box31 is provided with an opening upper surface and abottom wall31ahaving a substantially rectangular shape which is substantially the same with the back surface of thesecond scintillator15 and arranged in parallel with the back surface thereof. Thebottom wall31ais formed with two apertures31b1,31b2. The two apertures31b1 and31b2 are arranged in parallel with the longitudinal direction of thesecond scintillator15 at a predetermined interval. One31b1 of the apertures is formed on a center portion of thebottom wall31aand the other31b2 thereof is formed on one end portion thereof.
• The[0186]first filter26aof the first photo-detector25ais buried in the aperture31b1 so that thefirst filter26ais arranged so as to be away from the back surface of thesecond scintillator15 at the distance between the back surface thereof and thebottom wall31a.
• The second photo-[0187]detector25bincluding thesecond filter26bis penetrated through the aperture31b2 so that thesecond filter26bis optically closely adhered to the back surface of thesecond scintillator15.
• The reflecting[0188]box31 is also provided with fourside walls31cattached to thebottom wall31aso as to extend four side edge portions thereof to the back surface of thesecond scintillator15 thereby being closely connected thereto, and therefore, aclosed space32 is formed among the back surface of thesecond scintillator15, theside walls31cof the reflectingbox31 and thebottom wall31athereof. That is, the closedspace32 is surrounded by the back surface of thesecond scintillator15, theside walls31cand thebottom wall31aso that an air exists in the closedspace32 whereby anair layer32ais formed therein.
• In addition, inner surfaces (reflection surfaces)[0189]31dof the bottom andside walls31aand31care processed so as to totally internally reflect diffusely the light emitted from thefirst scintillator14. For example, a material capable of effectively diffusely reflecting the light than a material of which the reflectingbox31 is made, such as a titanium oxide or other similar materials is applied on theinner surfaces31dof the bottom andside walls31aand31c.
• Incidentally, other structures of the[0190]radiation detecting apparatus11G of this eighth embodiment is substantially the same as the structures of theradiation detecting apparatus11C of the fourth embodiment, and therefore, the descriptions about the other structures of theradiation detecting apparatus11G are omitted.
• In this structure, because the[0191]second scintillator15 is surrounded by theair layer32aexisting in the closedspace32 having the refractive index which is lower than that of thesecond scintillator15 itself, the light L2 emitted in thesecond scintillator15 is totally internally reflected on theair layer32aso as to be diffused in thesecond scintillator15 while being captured therein.
• Therefore, in the case where the light L[0192]2bis emitted at a position in thesecond scintillator15 away from thesecond filter26b,the emitted light L2bdoes not pass on thefirst filter26aof the first photo-detector25aso that the emitted light L2bis efficiently propagated to be ideally incident into thesecond filter26bwithout any influence of thefirst filter26a.
• Therefore, it is possible to efficiently detect the light L[0193]2 emitted in thesecond scintillator15 by the second photo-detector25b.
• In addition, the emitted light from the[0194]first scintillator14 is transmitted through thesecond scintillator15 to be filled in the closedspace32 while being totally internally reflected diffusely on the reflection surfaces31d.Therefore, it is possible to improve the probability that the emitted light from thefirst scintillator14 is reached to thefirst filter26ato be incident thereinto.
• In general, assuming that photons are uniformly distributed by the diffused reflection, the longer is the percentage of the sensitive area of the[0195]first filter26asensitive to the emitted light in all inner surface areas of the reflection surfaces31d,the more it is possible to improve the probability that the emitted light from thefirst scintillator14 is condensed on thefirst filter26a.
Ninth Embodiment (FIGS.9A,9B)
• FIG. 9A is an elevational view partially in section showing a radiation detecting apparatus in the case of viewing the radiation detecting apparatus from a lateral side of first and second scintillators thereof according to a ninth embodiment of the present invention. FIG. 9B is an elevational view partially in section showing a radiation detecting apparatus in the case of viewing the radiation detecting apparatus from a longitudinal side of the first and second scintillators thereof according to the ninth embodiment.[0196]
• In view of the aforesaid circumstances with respect to the structure of the radiation detecting apparatus according to the fourth embodiment, the[0197]radiation detecting apparatus11H of this ninth embodiment further comprises, in order to improve an incident probability of the light emitted from thefirst scintillator14 into thefirst filter26a,a reflecting plate (reflecting box)40 having four reflecting walls40a1 to40a4 for diffusely and totally internally reflecting on the four inclined reflecting walls40a1 to40a4 the emitted light from thefirst scintillator14 so that reflecting directions on average of the diffusely reflected lights on the four reflecting walls40a1 to40a4 are directed to a first scintillator side of thefirst filter26a.
• The four reflecting walls[0198]40a1 to40a4 of the reflectingplate40 are attached to four edge portions of the back surface of thesecond scintillator15 and to thefirst filter26aof the first photo-detector25awhich is arranged so as to be away from the back surface of thesecond scintillator15 at a predetermined interval.
• On back side of the[0199]second scintillator15, aclosed space41 is formed among the back surface of thesecond scintillator15 and the four reflecting walls40a1 to40a4. That is, the closedspace41 is surrounded by the back surface of thesecond scintillator15 and the four reflecting walls40a1 to40a4 so that an air exists in the closedspace41 whereby anair layer41ais formed therein.
• In addition, inner surfaces (reflection surfaces)[0200]42 of the reflecting walls40a1 to40a4 are processed so as to totally internally reflect diffusely the light emitted from thefirst scintillator14, similar to the fourth embodiment.
• In this embodiment, each of the reflecting walls[0201]40a1 to40a4 is inclined at a predetermined angle with respect to a direction of a center axis (a line vertically extending from a center of thefirst filter26a) of thefirst filter26aso that the reflecting directions on average of the diffusely reflected lights on the four reflecting walls40a1 to40a4 are directed to a position of thesecond scintillator15 at which the center axis of thefirst filter26ais crossed.
• Actually, it is possible to easily realize the structure of the[0202]radiation detecting apparatus11H according to the ninth embodiment by providing the reflecting walls40a1 to40a4 of the reflectingplate40 in thecase13 with the angles of the reflecting walls40a1 to40a4 with respect to the center axial direction of thefirst scintillator26abeing adjusted, respectively.
• Incidentally, other structures of the[0203]radiation detecting apparatus11H of this ninth embodiment is substantially the same as the structures of theradiation detecting apparatus11C of the fourth embodiment, and therefore, the descriptions about the other structures of theradiation detecting apparatus11H are omitted.
• In this structure, similar to the eighth embodiment, in the case where the light L[0204]2bis emitted at a position in thesecond scintillator15 away from thesecond filter26b,the emitted light L2bdoes not pass on thefirst filter26aof the first photo-detector25aso that the emitted light L2bis efficiently propagated to be ideally incident into thesecond filter26bwithout any influence of thefirst filter26a.
• Therefore, it is possible to efficiently detect the light L[0205]2 emitted in thesecond scintillator15 by the second photo-detector25b.
• In addition, it is noted that a reflection angle on the diffusion reflection surfaces is distributed like a cosine distribution by the Lambert's law.[0206]
• For this reason, because each of the reflecting walls[0207]40a1 to40a4 is inclined so that the reflecting directions on average of the diffusely reflected lights on the four reflecting walls40a1 to40a4 are directed toward thesecond scintillator14 side, the emitted light from thefirst scintillator14 transmitted through thesecond scintillator15 and filled in the closedspace41 is diffusely reflected to each reflection surface42 of each of the reflecting walls40a1 to40a4 so as to be transmitted toward thesecond scintillator15 and thefirst scintillator14.
• Then, the transmitted light emitted from the[0208]first scintillator14 is diffusely reflected on thesecond scintillator15 or thefirst scintillator14 so as to be directed to thefirst filter26a.
• Therefore, it is possible to increase a quantity of the emitted light from the[0209]first scintillator14 which is condensed on thefirst filter26a.
• Incidentally, in this structure, the reflecting plate has four reflecting walls, but the present invention is not limited to the structure. That is, the reflecting plate may have a peripheral wall whose normal lines are directed to the position of the second scintillator at which the center axis of the first filter is crossed.[0210]
Tenth Embodiment (FIGS.10A,10B)
• FIG. 10A is an elevational view partially in section showing a radiation detecting apparatus according to a tenth embodiment of the present invention. FIG. 10B is a plan view of the radiation detecting apparatus shown in FIG. 10A in the case of viewing the radiation detecting apparatus from an incident side of radiations.[0211]
• In this tenth embodiment, since the structures of the[0212]case13, thelight shielding film12 and the scintillator layer20 (thefirst scintillator14 and the second scintillator15) are the same with those of the radiation detecting apparatus of the third embodiment, descriptions of the structures of thecase13, thelight shielding film12 and the scintillator layer20 (thefirst scintillator14 and the second scintillator15) are omitted or simplified.
• The radiation detecting apparatus[0213]11I of the tenth embodiment comprises two photo-detectors45 (first and second photo-detectors45a,45b) mounted on the inner bottom surface of thecase13 so that the first photo-detector45aand the second photo-detector45bare distant from thesecond scintillator15.
• Similar to some of the above embodiments, as shown in FIG. 10B, the first and second photo-[0214]detectors45aand45bare arranged in parallel with a longitudinal direction of thesecond scintillator15 and located adjacent to each other.
• The first photo-[0215]detector45ais provided with a sensitive surface to which afirst filter46ais integrally mounted.
• The[0216]first filter46ais adapted to transmit therethrough only light emitted from thefirst scintillator14 and to absorb therein light emitted from thesecond scintillator15.
• Similarly, the second photo-[0217]detector45bis provided with a sensitive surface to which asecond filter46bis integrally mounted. Thesecond filter46bis adapted to transmit therethrough only light emitted in thesecond scintillator15 and to absorb therein light emitted from thefirst scintillator14.
• In addition, the radiation detecting apparatus[0218]11I further comprises alight guide50 interposed between thesecond scintillator15, and the first andsecond filters46aand46bfor guiding the light emitted from thefirst scintillator14 and the light emitted from the second scintillator onto the first andsecond filters46aand46b.
• The[0219]light guide50 is made of a material which is transparent to each of the emission wavelength bands of each of the first andsecond scintillators14 and15.
• The[0220]light guide50 has a substantially a truncated cone shape having an opening top surface, a bottom surface forming therewith two apertures and a side peripheral wall.
• The opening top surface of the[0221]light guide50 has a substantially rectangular shape which is substantially the same with the back surface of thesecond scintillator15 so that thelight guide50 is closely adhered at its opening top surface to the back surface of thesecond scintillator15.
• The peripheral surface of the[0222]light guide50 is tapered toward the bottom inner surface of thecase13 so that an area of each of the apertures is sufficiently small corresponding to an area of each of the first andsecond filters46a,46b.
• That is, the apertures are arranged in parallel with the longitudinal direction of the[0223]second scintillator15 at a predetermined interval corresponding to the arrangement of the first and second photo-detectors45aand45bso that the first and second photo-detectors45aand45bare inserted in the apertures, respectively.
• In the third embodiment, the lights emitted from the first and[0224]second scintillators14 and15 are filled in thecondensing box19 having the diffusion reflection surface as theinner surface19a.
• On the contrary, in this tenth embodiment, the lights emitted from the first and[0225]second scintillators14 and15 are filled in thelight guide50 so that the light emitted from thefirst scintillator14 and filled in thelight guide50 is guided so as to be transmitted only through thefirst filter46aof the photo-detector45athereby being detected by the photo-detector45a.
• Similarly, the light emitted from the[0226]second scintillator15 and filled in thecondensing box19 is guided so as to be transmitted only through thesecond filter46bof the photo-detector45bthereby being detected by the photo-detector45b.
• Therefore, it is possible to obtain the above effect according to the third embodiment.[0227]
• In addition, in the structure of this tenth embodiment, because the lights emitted from the first and[0228]second scintillators14 and15 are filled in thelight guide50, it is possible to arbitrarily set a shape and size of thelight guide50, thereby applying a photo-detector having a small size as each of the photo-detectors45aand45b.
• Moreover, similar to the above embodiments, it may be effective to process an outer surface of the side peripheral wall of the[0229]light guide50 so that the outer surface is polished so as to totally internally reflect the light emitted from thefirst scintillator14. Furthermore, it may be also effective to process the outer surface of the side peripheral wall of thelight guide50 so as to mirror or diffusely reflect the light emitted from thefirst scintillator14.
• Incidentally, in this structure, the photo-[0230]detectors45a,45bare arranged so as to closely be coupled with the outer side of thelight guide50. However, the present invention is not limited to the above structure. That is, similar to the above embodiments, the side peripheral wall of thelight guide50 may be formed with two concave portions in which the photo-detectors45a,45bare closely embed, as the case may be.
• According to this tenth embodiment, as described above, the first and second scintillators are made into a two-layer structure so that there is no need of measuring pulse height distributions and carrying out a waveform discrimination, making it possible to simultaneously and independently measure the α ray and the β ray with the use of the difference in their wavelengths, and to apply a photo-detector having a small size as each of the photo-detectors, thereby making the radiation detecting apparatus compact.[0231]
Eleventh Embodiment (FIG.11)
• FIG. 11 is an elevational view partially in section showing a radiation detecting apparatus according to an eleventh embodiment of the present invention.[0232]
• In view of the aforesaid circumstances with respect to the structure of the radiation detecting apparatus according to the fourth embodiment, in the[0233]radiation detecting apparatus11J of this embodiment, the arrangement of the first and second photo-detectors including the first and second filters, the shape of thelight guide50aand the arrangement thereof are modified as compared with those of the radiation detecting apparatus of the tenth embodiment.
• That is, in this structure, the[0234]light guide50ais arranged so as to be away from the back surface of thesecond scintillator15 at a predetermined interval and an air exists in thecase13 so that anair layer51 is formed between the back surface of thesecond scintillator15 and the top opening surface of thelight guide50a.
• The bottom surface of the[0235]light guide50ais formed with one aperture52a1 and other aperture52a2 is formed on one edge portion of the peripheral wall on the longitudinal edge side of thesecond scintillator15.
• The first filter[0236]46a1 of the first photo-detector45ais buried in the aperture52a1 so that thefirst filter46ais arranged so as to be away from the back surface of thesecond scintillator15 at the distance between the back surface thereof and the bottom surface of thelight guide50a.
• The second photo-[0237]detector45bincluding thesecond filter46bis penetrated through the aperture52a2 so that thesecond filter46bis optically closely adhered to the back surface of thesecond scintillator15.
• Incidentally, other structures of the[0238]radiation detecting apparatus11J of this eleventh is substantially the same as the structures of theradiation detecting apparatus11C of the fourth embodiment, and therefore, the descriptions about the other structures of theradiation detecting apparatus11J are omitted.
• In this structure, similarly to the above embodiments, because the[0239]second scintillator15 is surrounded by theair layer51, the light L2 emitted in thesecond scintillator15 is totally internally reflected on the surrounding air layers27 and30 so as to be diffused in thesecond scintillator15 while being captured therein.
• Therefore, the emitted light L[0240]2 does not pass on thefirst filter46aof the first photo-detector45aso that the emitted light L2 is efficiently propagated to be ideally incident into thesecond filter46bwithout any influence of thefirst filter46a.
• In addition, because the opening top surface of the[0241]light guide50ahas wide area and the aperture52a1 of the bottom surface of thelight guide50ais narrowed sufficiently to fit the first filter46a1 to the aperture52a1, the lights emitted from the first andsecond scintillators14 and15 are effectively guided and condensed to thefirst filter46aof the first photo-detector45aso that the only light emitted from thefirst scintillator14 is selected by thefirst filter46ato be transmitted therethrough so that the light emitted from thefirst scintillator14 is detected by the photo-detector45a.
• As described above, in this embodiment, it is possible to ideally condense the light emitted in the[0242]second scintillator15 by the total internal reflection, and to increase a quantity of the emitted light from thefirst scintillator14 which is condensed on thefirst filter46a.
Twelfth Embodiment (FIG.12)
• FIG. 12 is an elevational view partially in section showing a radiation detecting apparatus according to a twelfth embodiment of the present invention. FIG. 13 is a plan view showing a second scintillator in FIG. 12.[0243]
• In this twelfth embodiment, similar to the third embodiment, the[0244]radiation detecting apparatus11K includes thecondensing box19 used as thecase13, and one incident side of thecondensing box19 is mounted with thelight shielding film12 capable of transmitting therethrough an α ray and a β ray while shielding light from the outside. The first andsecond scintillators14 and15 are arranged on an inside of thelight shielding film12 so that theair layer16 is interposed therebetween.
• In the[0245]condensing box19, two photo-detectors17 (first photo-detectors17a) are arranged on the backside of thesecond scintillator15.
• Each of the photo-detectors[0246]17(17a) is provided with the filter21(21a) adapted to selectively transmit therethrough only light emitted from thefirst scintillator14 without sensing the light emitted in thesecond scintillator15.
• On the other hand, the[0247]second scintillator15 is provided at both lateral side edges with fluorescence converting light guides60 so that the light emitted in thesecond scintillator15 is condensed by using a fluorescence converting effect of the fluorescence convertinglight guide60 of thesecond scintillator15.
• That is, as shown in FIG. 12 and FIG. 13, to the lateral side edge portions of the[0248]second scintillator15 the fluorescence converting light guides60 are attached, and each one lateral end of each of the fluorescence converting light guides60 is provided with a photo-detector61. The fluorescence convertinglight guide60 is formed by adding a fluorescent substance to a resin or the like, and has an effect of absorbing a scintillation light emitted in thesecond scintillator15 and re-emitting a light (fluorescence) having a longer wavelength. Moreover, the fluorescence convertinglight guide60 may be formed of a fiber made by adding the fluorescent substance to a core, (that is, a fluorescent fiber, a wavelength shift fiber, etc.), and is able to be used in accordance with its diameter and a joining method or the like.
• Incidentally, other structures of the[0249]radiation detecting apparatus11K of this twelfth embodiment is substantially the same as the structures of theradiation detecting apparatus11B of the third embodiment, and therefore, the descriptions about the other structures of theradiation detecting apparatus11K are omitted.
• According to the aforesaid structure, the[0250]air layer16 is interposed between the first andsecond scintillators14 and15, and thefirst scintillator14 is, for example, composed of a powder or sintered body. Thus, a diffuse reflection is made in thesecond scintillator15 itself so that the light is emitted outside. Therefore, the light emitted from thefirst scintillator14 is once transmitted through thesecond scintillator15, and thereafter, is filled in thecondensing box19, and thus, is detected by means of the photo-detector17 arranged in thecondensing box19. A component of the light from thesecond scintillator15 is incident in thecondensing box19; however, the incident light in thecondensing box19 is eliminated by means of thefilter21 provided on the photo-detector17.
• The surrounding of the[0251]second scintillator15 is surrounded with an air so that a confinement effect of the light emitted in thesecond scintillator15 is caused by the total internal reflection therein. As a result, half components or more of the emitted light in thesecond scintillator15 are condensed on the lateral edge portion side of thesecond scintillator15 with a high density. Since the fluorescence convertinglight guide60 is arranged on the lateral edge portion side of thesecond scintillator15, and in the fluorescence convertinglight guide60, the light emitted in thesecond scintillator15 is totally internally reflected in thelight guide60 while being guided therein so as to be converted (re-emitted) into the fluorescence light.
• As a result, it is possible to detect the re-emitted fluorescence light by means of the photo-[0252]detector61 provided on the lateral end surface of thelight guide60.
• In the aforesaid condensing system on the lateral edge side of the[0253]second scintillator15, the light emitted in thesecond scintillator15 is condensed without greatly depending upon an area of the scintillator so that it is possible to apply this condensing system to a large-area scintillator together with thecondensing box19.
• In this twelfth embodiment, as described above, the first and second scintillators are made into a two-layer structure so that there is no need of measuring pulse height distributions and carrying out a waveform discrimination, making it possible to simultaneously and independently measure the α ray and the β ray with the use of the difference in their wavelengths, and to provide a radiation detecting apparatus including scintillators each having still more large area.[0254]
• Although not illustrated, the entire peripheral edges of the[0255]second scintillator15 may be provided with the fluorescence convertinglight guide60, in addition to parallel two lateral side edges of thesecond scintillator15. Machining may be carried out with respect to no-use end of thefluorescence converting guide60 and two longitudinal side edges which are provided with nolight guide60 of thesecond scintillator15 so as to a mirror reflection and a diffuse reflection. By the aforesaid structures of the modifications, it is possible to improve an efficiency of using the light.
Thirteenth Embodiment (FIG.14)
• FIG. 14 is an elevational view partially in section showing a radiation detecting apparatus according to a thirteenth embodiment of the present invention.[0256]
• In this thirteenth embodiment, the first and[0257]second scintillators14 and15 of theradiation detecting apparatus11L are arranged on one side of anon-reflection type case13 so that theair layer16 is interposed therebetween. In thecase13, afluorescent screen65 is located on a position where the light emitted from thefirst scintillator14 transmitting through thesecond scintillator15 is capable of being incident. Thefluorescent screen65 is provided with the photo-detector17 (17a) which closely couples therewith. The photo-detector17 is provided with the filter21 (21a) for shielding a component of light emitted from thesecond scintillator15, which is incident upon thelight guide50.
• Incidentally, an air layer is interposed between the[0258]second scintillator15 and thefluorescent screen65. Moreover, like the twelfth embodiment, at lateral edge portions, thesecond scintillator15 is provided with fluorescence converting light guides60 and the photo-detectors61, respectively, and thus, the condensing structure by the fluorescence conversion according to the twelfth embodiment is employed on the lateral edge portion sides of thesecond scintillator15.
• Incidentally, other structures of the[0259]radiation detecting apparatus11L of this thirteenth embodiment is substantially the same as the structures of the radiation detecting apparatus11I of the tenth embodiment, and therefore, the descriptions about the other structures of theradiation detecting apparatus11L are omitted.
• In this structure, the light emitted from the[0260]first scintillator14 transmits through thesecond scintillator15, and then, is incident upon thefluorescent screen65, and thus, converted into a fluorescence light so that the converted fluorescence light are emitted therein. The emitted fluorescence light is incident upon thelight guide50 provided so as to be closely coupled with thefluorescent screen65, and then, reaches the photo-detector17 so as to be detected hereto. Moreover, the light emitted in thesecond scintillator15 is detected by means of the fluorescence convertinglight guide60 provided on each lateral edge side portion of thesecond scintillator15 and the photo-detector61 attached to each lateral end portion of thelight guide61.
• According to this thirteenth embodiment, as described above, the first and second scintillators are made into a two-layer structure so that there is no need of measuring pulse height distributions and carrying out a waveform discrimination, making it possible to simultaneously and independently measure the α ray and the β ray with the use of the difference in their wavelengths, and to make compact the size of the photo-[0261]detector17 to be used, thereby making the size of the radiation detecting apparatus compact.
• Incidentally, the[0262]fluorescent screen65 may be formed into the same shape as thelight guide50 so as to dispense thelight guide50.
Fourteenth Embodiment (FIG.15)
• FIG. 15 is an elevational view partially in section showing a radiation detecting apparatus according to a fourteenth embodiment of the present invention.[0263]
• In this fourteenth embodiment, similar to the above thirteenth embodiment, the first and[0264]second scintillators14 and15 of theradiation detecting apparatus11K are arranged on one side of anon-reflection type case13 so that theair layer16 is interposed therebetween. Thesecond scintillator15 is provided at each lateral edge portion with the fluorescence convertinglight guide60 and the photo-detector61, and thus, the condensing structure by the fluorescence conversion is employed on each lateral edge portion side of thesecond scintillator15.
• Moreover, the[0265]fluorescent screen65 is located on a position where the light emitted from thefirst scintillator14 transmitting through thesecond scintillator15 is capable of being incident.
• The[0266]fluorescent screen65 is provided at each lateral edge portion side with a secondlight guide70 and a photo-detector71, similar to each lateral edge portion side of thesecond scintillator15, and thus, the condensing structure by the fluorescence conversion is employed on each lateral edge portion side of the secondlight guide70. That is, the light emitted from thefirst scintillator14 is converted into the a first fluorescence light in thefluorescent screen65, and further, the first fluorescence light is doubly converted into a second fluorescence light having a longer wavelength as compared with the first fluorescence light on each lateral edge side of thefluorescent screen65.
• In this case, a fluorescent substance contained in the second fluorescence converting[0267]light guide70 for thefluorescent screen65 is different from that used for thesecond scintillator15. Namely, a fluorescent substance is selectively applied to thesecond scintillator15 and thefluorescent screen65. That is, thesecond scintillator15 includes a fluorescent substance, which absorbs a light from thesecond scintillator15 and converts it into a fluorescence light, and thefluorescent screen65 includes a fluorescent substance which is capable of absorbing a fluorescence light from thefluorescent screen65 and converting it into a fluorescence light having a longer wavelength as compared with the fluorescence light converted by thesecond scintillator15.
• Incidentally, other structures of the[0268]radiation detecting apparatus11M of this fourteenth embodiment is substantially the same as the structures of theradiation detecting apparatus11L of the thirteenth embodiment, and therefore, the descriptions about the other structures of theradiation detecting apparatus11M are omitted.
• With the above structure, the light radiated into an air from the[0269]first scintillator14 and incident upon thesecond scintillator15 is not substantially captured in thesecond scintillator15. In addition, in the case where the light emitted from thefirst scintillator14 is directly incident upon the fluorescence convertinglight guide60 provided on thesecond scintillator15, because an absorbed wavelength band of thelight guide60 is different from the incident light emitted from thefirst scintillator14. Therefore, no fluorescence signal is generated as an error signal by the photo-detector17.
• According to this fourteenth embodiment, as described above, the first and second scintillators are made into a two-layer structure so that there is no need of measuring pulse height distributions and carrying out a waveform discrimination, making it possible to simultaneously and independently measure the α ray and the β ray with the use of the difference in their wavelengths.[0270]
• In addition, because the light emitted from the first scintillator is condensed on each lateral edge portion of the[0271]fluorescent screen65, it is possible to make the width of the radiation detecting apparatus thin and to increase the area thereof.
Fifteenth Embodiment (FIG.16)
• This fifteenth embodiment relates to a radiation detecting system having one of the radiation detecting apparatuses described in the above first to fourteenth embodiments, and FIG. 16 is a view schematically showing a structure of the radiation detecting system. Incidentally, in this embodiment, for example, the radiation detecting system includes the[0272]radiation detecting apparatus11 described in the first embodiment. Incidentally, otherradiation detecting apparatuses11A˜11M are able to be used in the radiation detecting system according to the fifteenth embodiment, as in the case of using theradiation detecting apparatus11.
• As shown in FIG. 16, in this fifteenth embodiment, a signal outputted from the photo-[0273]detector17 of theradiation detecting apparatus11 is processed by means of a pulseheight discrimination unit75 as a signal processing unit. More specifically, in the case where at least one of the photo-detector17 corresponding to each of the aforesaid scintillators constituting a two-layer structure, the signal outputted from the photo-detector17 is inputted in the pulseheight discrimination unit75.
• The pulse[0274]height discrimination unit75 recognizes a pulse signal having a predetermined pulse height value or more as the signal corresponding to the light from the first or second scintillator according to the inputted signal so as to carry out a process of eliminating a signal less than the predetermined pulse height value as a noise.
• According to this fifteenth embodiment, only when a signal more than a dark current noise of the photo-[0275]detector17 is transmitted to the pulseheight discrimination unit75, it is possible to recognize the signal corresponding to the light from the first or second scintillator by the pulseheight discrimination unit75.
Sixteenth Embodiment (FIG.17)
• This sixteenth embodiment relates to a radiation detecting system having one of the radiation detecting apparatuses described in the above first to fourteenth embodiments, and FIG. 17 is a view schematically showing a structure of the radiation detecting system. Incidentally, in this embodiment, for example, the radiation detecting system includes the[0276]radiation detecting apparatus11 described in the first embodiment. Incidentally, otherradiation detecting apparatuses11A˜11M are able to be used in the radiation detecting system according to the sixteenth embodiment, as in the case of using theradiation detecting apparatus11.
• In this sixteenth embodiment, signals outputted from the plurality of photo-[0277]detectors17 are processed by means of asignal processing unit77. More specifically, in the case where the plurality of the photo-detectors17 corresponding to each of the scintillator having a two-layer structure are used, or in the case of adding each signal from each photo-detector, an analog adder having a band capable of amplifying a signal is required. However, by using thesignal processing unit77 for detecting an establishment of a logic product by using logic signals corresponding to the detected signals of the photo-detectors17, it is possible to easily discriminate the signals corresponding to the lights from each of the first and second scintillators except for the noises.
• As shown in FIG. 17, for example, in the case where three signals A, B and C outputted from the photo-[0278]detectors17 corresponding to each scintillator are inputted in thesignal processing unit77, thesignal processing unit77 executes the logic product by using any two inputted signals of them, and, when the logic product is established, thesignal processing unit77 discriminates the signals A, B and C as the signals corresponding to the lights from the first and second scintillators.
• According to this sixteenth embodiment, employing the aforesaid system, it is possible to eliminate mutually non-correlative dark current noises generated in the photo-[0279]detectors17 so as to extract only the signals corresponding to the lights from the first and second scintillators.
Seventeenth Embodiment (FIG.18)
• FIG. 18 is a view showing a radiation detecting system according to a seventeenth embodiment of the present invention.[0280]
• In this seventeenth embodiment, the radiation detecting system comprises a[0281]radiation detecting apparatus11N having a substantially the same structure of theradiation detecting apparatus11 without having the condensingunit18.
• That is, the[0282]radiation detecting apparatus11N is provided with the two kinds ofscintillators14 and15 having the different emission center wavelengths with each other, and with thecondensing box19 having a reflecting inner surface. On a radiation incident side of thecondensing box19, thelight shielding film12 is provided. Thelight shielding film12 is capable of transmitting therethrough an α ray and a β ray and shielding light from the outside. The first andsecond scintillators14 and15 are arranged on the inside of thelight shielding film12 in thecondensing box19.
• The lights emitted from the first and[0283]second scintillators14 and15 are mixed to be filled in thecondensing box19. In the example shown in FIG. 18, two photo-detectors17 are arranged in thecondensing box19, and the photo-multiplier tube is used as each photo-detector17.
• In this embodiment, the[0284]radiation detecting apparatus11N also comprises anoptical attenuation filter80 interposed between the first andsecond scintillators14 and15. The same material as thelight shielding film12 may be used as a material capable of attenuating light and transmitting therethrough a β ray. For example, a thickness of the aluminum focused on a thin polyester film is adjusted to apply to the material of theoptical attenuation filter80. An air layer may be interposed between thefirst scintillator14 and theoptical attenuation filter80 and between thesecond scintillator15 and the same, and these components may be optically closely adhered with each other.
• Signals outputted from the photo-[0285]detectors17 are adapted to be inputted to asignal processing unit81.
• With the above structure, by the[0286]optical attenuation filter80, the light emitted from thefirst scintillator14 based on the α ray is attenuated to be filled in thecondensing box19. In this case, the light emitted from thesecond scintillator15 is not attenuated and weakened.
• The signals outputted from the photo-[0287]detectors17 are inputted in thesignal processing unit81. The signals inputted in thesignal processing unit81 are individually processed, or added, or gated by the simultaneous counting information so as to extract the signals corresponding to the lights from the first andsecond scintillators14 and15 except for noises.
• Then, according to the extracted signals, the[0288]signal processing unit81 discriminates between the signal corresponding to the emitted light from thefirst scintillator14 on the basis of the α ray, and the signal corresponding to the emitted light from thesecond scintillator15 on the basis of the β ray.
• That is, conventionally, because a signal level based on the α ray is high, in the waveform discrimination process for optimizing the signal level, a sensitivity relating to the β ray has not sufficiently been obtained. However, according to this seventeenth embodiment, a quantity of light emitted from the[0289]first scintillator14 corresponding to the α ray is adjusted through theoptical attenuation filter81 so that it is possible to optimize and use an input voltage range in the signal processing unit82 for discriminating a waveform.
Eighteenth Embodiment (FIG.19)
• FIG. 19 is a view showing a radiation detecting system according to an eighteenth embodiment.[0290]
• In this eighteenth embodiment, the radiation detecting system comprises a[0291]radiation detecting apparatus110 having a substantially the same structure of theradiation detecting apparatus11L except that the photo-detector17 is single.
• In this eighteenth embodiment, the[0292]optical attenuation filter80 is interposed between the first andsecond scintillators14 and15, and thelight guide50 is arranged so as to closely be coupled with thesecond scintillator15. Furthermore, thelight guide50 is closely be coupled with the photo-detector17.
• With the above construction, by the[0293]optical attenuation filter80, the light emitted from thefirst scintillator14 based on the α ray is attenuated to be filled in thelight guide50. Therefore, in this eighteenth embodiment, similar to the seventeenth embodiment, a quantity of light emitted from thefirst scintillator14 corresponding to the α ray is adjusted through theoptical attenuation filter81 so that it is possible to optimize and use an input voltage range in thesignal processing unit81 for discriminating a waveform.
• While there has been described what is at present considered to be the preferred embodiments and modifications of the present invention. It will be understood that various modifications which are not described yet may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.[0294]

Claims (21)

What is claimed is:

1. A radiation detecting apparatus comprising:

a light shielding film for transmitting therethrough first and second radiations while shielding an incidence of light;

a first scintillator for emitting a first light by the first radiation transmitted through the light shielding film, said first scintillator having an emission center wavelength based on the first radiation;

a second scintillator for emitting a second light by the second radiation transmitted through the light shielding film, said second scintillator having an emission center wavelength based on the second radiation; and

detection means having at least one photo-detector for detecting the first light emitted from the first scintillator and the second light emitted in the second scintillator,

said first emission center wavelength and said second emission center wavelength being different from each other.

2. A radiation detecting apparatus according toclaim 1, wherein said first emission center wavelength is a wavelength of the first light emitted in the first scintillator and having a peak emission intensity in an emission wavelength band of the first scintillator, and said second emission center wavelength is a wavelength of the second light emitted in the second scintillator and having a peak emission intensity in an emission wavelength band of the second scintillator.

3. A radiation detecting apparatus according toclaim 2, wherein said first scintillator and second scintillator are arranged in parallel to each other so that the second scintillator is located away from the first scintillator at a predetermined distance, further comprising means for condensing the first light emitted from the first scintillator and the second light emitted in the second scintillator on the detection means; and an air layer interposed between the first and second scintillators,

said first emission center wavelength of the first scintillator being set shorter than the second emission center wavelength of the second scintillator.

4. A radiation detecting apparatus according toclaim 2, further comprising means for condensing the first light emitted from the first scintillator and the second light emitted in the second scintillator on the detection means, wherein said first scintillator and second scintillator are closely optically adhered with each other,

said first emission center wavelength of the first scintillator being set shorter than the second emission center wavelength of the second scintillator.

5. A radiation detecting apparatus according toclaim 2, further comprising means for condensing the first light emitted from the first scintillator and the second light emitted in the second scintillator on the detection means, wherein said first scintillator and second scintillator are closely optically adhered with each other,

said first emission center wavelength of the first scintillator being set longer than the second emission center wavelength of the second scintillator.

6. A radiation detecting apparatus according toclaim 2, further comprising a condensing box for condensing the first and second lights on the detection means, said condensing box having an inner surface for diffusely reflecting the first and second lights and a side surface, said light shielding film being mounted on the side surface on which the first and second radiations incident, said first and second scintillators being arranged inside the light shielding film, and wherein said detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector,

said first filter being adapted to transmit therethrough only the first light emitted from the first scintillator,

said second filter being adapted to transmit therethrough only the second light emitted in the second scintillator.

7. A radiation detecting apparatus according toclaim 2, wherein said second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, said detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector,

said first filter being adapted to transmit therethrough only the first light emitted from the first scintillator,

said second filter being adapted to transmit therethrough only the second light emitted in the second scintillator, and

wherein said first filter and the second filter are closely optically adhered on the back surface of the second scintillator.

8. A radiation detecting apparatus according toclaim 2, wherein said second scintillator has a substantially rectangular shape, and wherein said first photo-detector and the second photo-detector are adjacently arranged so that a line is crossed to a longitudinal direction of the second scintillator, said line connecting a center point of the sensitive surface of the first photo-detector and that of the sensitive surface of the second photo-detector.

9. A radiation detecting apparatus according toclaim 2, wherein said second scintillator has a substantially rectangular shape, and wherein said first photo-detector and the second photo-detector are arranged on both lateral sides of the second scintillator so that the first photo-detector is the most distant from the second photo-detector.

10. A radiation detecting apparatus according toclaim 2, wherein said second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, said detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector,

said first filter being adapted to transmit therethrough only the first light emitted from the first scintillator,

said second filter being adapted to transmit therethrough only the second light emitted in the second scintillator, and

wherein said first filter is arranged to be away from the back surface of the second scintillator at a predetermined interval so that an air layer is interposed between the back surface of the second scintillator and the first filter, and said second filter is closely optically adhered on the back surface of the second scintillator.

11. A radiation detecting apparatus according toclaim 2, wherein said second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, said detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector,

said first filter being adapted to transmit therethrough only the first light emitted from the first scintillator,

said second filter being adapted to transmit therethrough only the second light emitted in the second scintillator, and

wherein said first filter is arranged to be away from the back surface of the second scintillator at a predetermined interval, and said second filter is closely optically adhered on the back surface of the second scintillator, further comprising a surrounding box having an inner surface portion for surrounding a back surface side of the second scintillator so as to form a closed space therein, said back surface of the second scintillator and said first filter forming parts of the inner surface portion of the surrounding box, said inner surface portion of the surrounding box except for the back surface of the second scintillator and the first filter being processed to totally internally reflect diffusely the first light emitted from the first scintillator.

12. A radiation detecting apparatus according toclaim 11, wherein said inner surface portion comprises a plurality of inner surfaces, each of said inner surfaces is inclined so that the diffusely reflecting directions on average of the first light on the inner surfaces of the surrounding box are substantially directed to a position of the second scintillator at which a center axis of the sensitive surface of the first photo-detector is crossed.

13. A radiation detecting apparatus according toclaim 2, further comprising a light guide in which the first light emitted from the first scintillator and the second light emitted in the second scintillator are incident, said light guide being adapted to condense the first and second lights on the detection means, and wherein said detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector,

said first filter being adapted to transmit therethrough only the first light emitted from the first scintillator,

said second filter being adapted to transmit therethrough only the second light emitted in the second scintillator.

14. A radiation detecting apparatus according toclaim 13, wherein said first filter is arranged to be away from the back surface of the second scintillator at a predetermined interval, and said second filter is closely optically adhered on the back surface of the second scintillator, and wherein said light guide has an opening surface opposite to the back surface of the second scintillator, said light guide being arranged so that the opening surface thereof being away from the back surface of the second scintillator at a predetermined interval so as to interpose an air layer between the opening surface of the light guide and the back surface of the second scintillator, said opening surface thereof having an area which is larger than that of the first filter.

15. A radiation detecting apparatus according toclaim 2, further comprising a light guide connecting the at least one photo-detector to an edge portion of the second scintillator, said light guide being adapted to convert the second light to a fluorescent light.

16. A radiation detecting apparatus according toclaim 2, wherein said second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, further comprising a fluorescent screen arranged on a back surface side of the second scintillator and opposite through an air layer to the back surface thereof, said fluorescent screen being adapted to convert the first light emitted from the first scintillator to a fluorescent light; and a light guide adapted to condense the converted fluorescent light on the at least one photo-detector, said converted fluorescent light being emitted from a surface of the fluorescent screen, said at least one photo-detector detecting the condensed fluorescent light.

17. A radiation detecting apparatus according toclaim 2, wherein said second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, further comprising a fluorescent screen arranged on a back surface side of the second scintillator and opposite through an air layer to the back surface thereof, said fluorescent screen being adapted to convert the first light emitted from the first scintillator to a fluorescent light; and a second light guide having a fluorescent substance adapted to absorb the converted fluorescent light so as to emit a fluorescent light, said converted fluorescent light by the fluorescent screen being emitted from an edge portion of the fluorescent screen, said fluorescent light emitted from the light guide having a wavelength which is longer than that of the converted fluorescent light by the fluorescent screen, said at least one photo-detector detecting the fluorescent light emitted from the second light guide.

18. A radiation detecting apparatus according toclaim 2, further comprising means for capturing a signal outputted from the detection means so as to recognize a signal having a predetermined pulse height value and over as an optical signal thereby eliminating a signal less than the predetermined pulse height value as a noise, said optical signal corresponding to at least one of the first and second lights emitted from the first and second scintillators.

19. A radiation detecting apparatus according toclaim 2, wherein said detection means comprises a plurality of photo-detectors, a first group of the photo-detectors being adapted to detect the first light emitted from the first scintillator, a second group thereof being adapted to detect the second light emitted from the second scintillators, further comprising means for capturing signals outputted each of the first and second groups of the photo-detectors and, in a case of detecting signals outputted from at least one of the first and second groups of the photo-detectors, for recognizing detected signals corresponding to at least one of the first and second lights emitted from the first and second scintillators and, in a case where only one signal is outputted from at least one of the first and second groups of the photo-detectors, for eliminating the only one signal as a noise.

20. A radiation detecting apparatus according toclaim 2, further comprising an optical attenuation filter for transmitting therethrough the first and second radiations and attenuating an intensity of the first light emitted from the first scintillator, said optical attenuation filter being interposed between the first and second scintillators; a condensing box for condensing the first and second lights on the detection means, said condensing box having an inner surface for diffusely reflecting the first and second lights; and means for inputting signals detected by the detection means so as to discriminate, according to a difference of waveforms of the inputted signals, between an optical signal corresponding to the first light emitted from the first scintillator and an optical signal corresponding to the second light emitted from the second scintillator.

21. A radiation detecting apparatus according toclaim 2, further comprising an optical attenuation filter for transmitting therethrough the first and second radiations and attenuating an intensity of the first light emitted from the first scintillator, said optical attenuation filter being interposed between the first and second scintillators; a light guide in which the first light emitted from the first scintillator and the second light emitted in the second scintillator are incident, said light guide being adapted to condense the first and second lights on the detection means; and means for inputting signals outputted from the detection means so as to discriminate, according to a difference of waveforms of the inputted signals, between an optical signal corresponding to the first light emitted from the first scintillator and an optical signal corresponding to the second light emitted from the second scintillator.

Images