JP2000193749A - alphabeta DETECTOR AND alphabeta DETECTING DEVICE USING IT - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an αβ detector and an αβ detection device using it that can be fully put into practical applications as a detector for monitoring radiation, at the same time, can be manufactured at low costs, and can independently and simultaneously detect α and β rays while fully suppressing γ-ray sensitivity and securing the maximum sensitivity. SOLUTION: A device is equipped with a glare protection film 12 where αand β rays can be transmitted and at the same time the incidence of light can be obstructed, first and second scintillators 14 and 15 that emit light by the α and β rays through the glare protection film 12, respectively, a condensation means 18 that condenses light emitted by the first and second scintillators 14 and 15, and one or more photo detectors 17 that detect light being condensed by the condensation means 18. In the device, air layer is included between the first and second scintillators 14 and 15, and at the same time, the light emission center wavelength of the first scintillator 14 is set shorter than that of the second one 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation measurement technique used in a facility for handling radioactive materials, such as a nuclear power plant, and more particularly to a technique capable of simultaneously and independently measuring α-rays and β-rays at the same position. The present invention relates to an αβ detector suitable for practical use as a radiation monitor and an αβ detector using the detector.

[0002]

2. Description of the Related Art FIG. 16 shows, as a conventional example, a ho switch type detection apparatus for simultaneous detection of α rays and β rays.

In this apparatus, a first scintillator 2 and a second scintillator 3 are superposed on a lower layer of a light-shielding film 1 which can transmit α and β rays and can block external light. The first scintillator 2 has ZnS for detecting α-rays.
(Ag) is applied, and β is applied to the second scintillator 2.
Plastic or the like is often applied to detect lines. The first and second scintillators 2 and 3 stacked on the two layers are directly mounted on the photodetector 5 and housed in a case 6. As the photodetector 5, a photomultiplier tube capable of high-speed response and high sensitivity is generally used.

[0004] ZnS constituting the first scintillator 2
The light emission decay time constant of (Ag) is on the order of μsec, but the light emission decay time constant of the plastic constituting the second scintillator 3 is on the order of tens of nanoseconds, and the light emission decay time constant of the plastic scintillator is much shorter. . When the output current signal of the photodetector 5 is converted into a voltage signal by an RC integrating circuit having a time constant sufficiently longer than the light emission decay time of each of the scintillators 2 and 3, the rising time of the pulse becomes substantially equal to the light emission decay time, 6 shows an exponential decay waveform of a time constant determined by a resistance R and a capacitance C. This signal conversion processing can be performed by, for example, a preamplifier unit included in the photodetector 5 and attached to the photomultiplier tube.

[0005] The signal is amplified to a voltage level that can be analyzed by the waveform discrimination processing device 7 as necessary. When the signal is input, the waveform discrimination processing device 7 outputs a signal having a pulse height proportional to the rise time, and converts the pulse height into a digital value by an analog-digital converter, and performs general multi-wave height analysis. The wave height distribution is measured by the device.

[0006] From the spectral data representing the rise time obtained by the waveform discriminating device 7, the light emission from the first scintillator 2 and the light emission from the second scintillator 2 can be distinguished.

FIG. 17 shows an αβ detecting device using an energy spectrum measuring sensor 8 as another conventional example.

As the energy spectrum measuring sensor 8 of this device, for example, a Si semiconductor sensor or the like is used. Since this sensor has sensitivity to room light other than radiation, the light shielding film 1 is mounted as described above. It is stored in the case 6.

The output signal of the energy spectrum measuring sensor 8 is subjected to signal processing in a pulse height analysis system 9 and measured as an energy spectrum. The pulse height analysis processing system 9 generally includes a charge-sensitive preamplifier for processing a sensor output signal, a linear amplifier, an analog-digital converter, a multiple wave height analyzer, and the like. On the energy spectrum obtained by the wave height analysis processing system 9, the α-ray signal and the β-ray signal show different distributions and peak shapes, and the data processing of these signals makes it possible to discriminate between the α-ray and the β-ray. It can be carried out.

[0010]

However, FIG.
The waveform discrimination processing device 7 required for the conventional Woswitch-type detection device shown in (1) is a waveform discrimination processing device for rising analysis, which is very expensive. For this reason, it is useful for research at the laboratory level, but as a detection device mounted on a monitor device used in actual nuclear facilities etc.,
There is a problem in cost. In addition, the rise time itself is originally analyzed, and when the purpose is to simply discriminate those having different rise times, it is overspecified.

From a more fundamental point of view, to determine the rise time, for example, 10% of the input peak value, 9%
It is necessary to perform signal detection at the 0% level, and there is a problem that a signal having a low peak value cannot be analyzed and measured. This is a problem related to the dynamic range of the peak value of the signal. For example, αS of ZnS (Ag)
The amount of light emitted by the X-rays is considerably larger than the amount of light emitted by the β-rays of the plastic scintillator.
nS (Ag) is larger.

For this reason, it is disadvantageous in measurement for a β-ray signal having a small peak value and being continuously distributed on the low energy side. In particular, a component having a small peak value is not analyzed and measured. There is a serious drawback that the β-ray sensitivity is low. In particular, when the thickness of the plastic scintillator is reduced in order to suppress the γ-ray sensitivity, the above phenomenon is further accelerated because the light emission amount is further reduced.

Also, in the case of the apparatus using the energy spectrum measuring sensor 8 shown in FIG. 17, there is a problem that the same wave height analyzing apparatus as described above is required and the cost is high. Since the effective atomic weight of the base material is larger than that of the plastic scintillator, there is a drawback that γ-ray sensitivity is high and γ-ray signals are mixed with β-ray signals.

Further, when the measurement is not performed in a vacuum or when α-rays from α-ray emitting nuclides adsorbed on filter paper are measured, the energy loss of α-rays is large and the fluctuation of the range is large. For this reason, a Gaussian peak as obtained in a vacuum cannot be obtained, and may overlap with the energy spectrum of β-rays. Despite the measurement of the energy spectrum, a clear separation between α-rays and β-rays Can be difficult.

The present invention has been made in view of such circumstances, and can be sufficiently used as a detector for radiation monitoring, can be manufactured at low cost, and can sufficiently suppress the γ-ray sensitivity. It is an object of the present invention to provide an αβ detector that can detect both α-rays and β-rays independently and simultaneously while ensuring maximum sensitivity, and an αβ detection device using the same. I do.

[0016]

Means for Solving the Problems In an αβ detector,
As described above, the light emitted from the first scintillator for α-rays passes through the second scintillator for β-rays, and is guided to the photodetector by the condensing means. In this case, conventionally, a waveform discriminating apparatus for rise analysis has been applied by focusing on the pulse rise time of the converted signal by the RC integration circuit, which is substantially equal to the light emission decay time of each scintillator.

In this regard, the inventor of the present invention adjusts and optimizes the scintillator to be used, the emission wavelength, and the amount of light emission, thereby eliminating the need for a waveform discrimination processing device for rising analysis, which has been conventionally required. It was inspired that it could be

That is, as the photodetector, a photomultiplier tube is preferably used in terms of response speed and sensitivity. In this case, the photomultiplier tube is so provided that the maximum sensitivity can be obtained at the emission wavelength of the first scintillator. Is selected, the sensitivity of the second scintillator in a longer wavelength band decreases. On the other hand, when a photomultiplier tube optimized for the second scintillator is used, the quantum efficiency of the first scintillator in a shorter wavelength band decreases. Conversely, if the emission wavelength of the first scintillator and the emission wavelength of the second scintillator are set differently, these are adjusted and optimized according to the scintillator to be used, the emission wavelength, and the emission amount. You can do it. Furthermore, not only the light emission decay time but also the light emission wavelength is intentionally changed to configure the sensor, so that means for optically identifying the wavelength can be used together.

In addition to the above points, the inventor of the present invention has adopted a first scintillator and a second scintillator as means for independently and simultaneously detecting both α rays and β rays while ensuring maximum sensitivity. It was conceived to make it easier to confine the light inside the scintillator and increase the light-collecting density by the positional relationship between the two. That is, the first scintillator that emits light by α-rays is extremely thin in order to suppress the sensitivity to β-rays and γ-rays, and is often made of, for example, a powder or a sintered body. Thus, the first scintillator emits light as a result of diffuse reflection within itself. When this light emission passes through the second scintillator for β-rays and air is interposed between the first scintillator and the second scintillator guided to the photodetector by the condensing means, the first Although the probability of causing Fresnel reflection when the light of the scintillator passes through the second scintillator increases, the second scintillator is surrounded by air having a value lower than its own refractive index. It is easy to confine light. For this reason,
As a light collecting means for the second scintillator, there is obtained an advantage that it is easy to apply a method utilizing light gathered at a high density on the edge side.

Based on the above idea, according to the first aspect of the present invention, a light-shielding film capable of transmitting α-rays and β-rays and capable of blocking the incidence of light, A first scintillator and a second scintillator emitting light by β-rays; a light condensing means for condensing light emitted by the first and second scintillators; and a light detecting means for detecting light condensed by the light condensing means. And one or more photodetectors, and an air layer is interposed between the first and second scintillators, and the emission center wavelength of the first scintillator is shorter than the emission center wavelength of the second scintillator. Provided is an αβ detector characterized by the setting.

According to the present invention, since air is interposed between the first scintillator and the second scintillator, the periphery of the second scintillator is surrounded by air having a value lower than its own refractive index. In addition, since light is easily confined inside the scintillator, it is easy to apply a method of using light that gathers at a high density on the edge side as a light condensing means for the second scintillator. In addition, an intervening substance for scintillator adhesion and optical close bonding is not required, and a configuration suitable for a case where there is a concern that the intervening substance itself or alteration due to a chemical interaction with the scintillator and the like is concerned. be able to. Further, since the independence of each scintillator is maintained, advantages such as maintenance, inspection, and replacement of only one of the scintillators are obtained.

By setting the emission center wavelength of the first scintillator to be shorter than the emission center wavelength of the second scintillator, a means for optically identifying the wavelength can be used together, and the waveform for the rise analysis can be used. The discrimination processing device can be made unnecessary.

According to the second aspect of the present invention, a light-shielding film capable of transmitting α-rays and β-rays and blocking the incidence of light, a first scintillator and a β-ray which emit light by the α-rays transmitted through the light-shielding film A second scintillator emitting light by
Condensing means for condensing light emitted by the first and second scintillators; and 1 for detecting light condensed by the condensing means.
And one or more photodetectors, and an air layer is interposed between the first and second scintillators, and the emission center wavelength of the first scintillator is longer than the emission center wavelength of the second scintillator. Provided is an αβ detector characterized by the setting.

According to the present invention, similarly to the first aspect of the present invention, high-density light collection can be performed on the edge side of the second scintillator, and effects such as elimination of intervening substances between the scintillators and improvement of maintainability are obtained. And the effects of optimizing the solidification quantum efficiency and wavelength identification are also exhibited. In the case of the present embodiment, by making the emission wavelength of the first scintillator longer than that of the second scintillator, light of longer wavelength from the first scintillator, which generally has higher transmission efficiency in the scintillator, is further increased. The first scintillator is less likely to be absorbed in the second scintillator, and is less likely to be absorbed and emitted by the phosphor contained in the second scintillator, thereby preventing the influence of light of the first scintillator on the second scintillator. can do.

According to the third aspect of the present invention, a light-shielding film capable of transmitting α-rays and β-rays and blocking the incidence of light, a first scintillator and a β-ray which emit light by the α-rays transmitted through the light-shielding film A second scintillator emitting light by
Condensing means for condensing light emitted by the first and second scintillators; and 1 for detecting light condensed by the condensing means.
At least one photodetector, and optically contact each other without interposing an air layer between the first and second scintillators, and adjust the emission center wavelength of the first scintillator to the second scintillator.
An αβ detector characterized by being set to be shorter than the emission center wavelength of the scintillator.

According to the present invention, by bringing the first and second scintillators into optical close contact with each other, Fresnel reflection based on the difference in refractive index due to the interposition of the air layer, and internal reflection due to total reflection in the scintillator. Capture can be reduced and the probability of transmission of the light of the first scintillator through the second scintillator can be increased. For this reason, it becomes easy to apply a method of focusing on light from the surface of the second scintillator that is not joined to the first scintillator as the light collecting means.

According to the fourth aspect of the present invention, a light-shielding film capable of transmitting α-rays and β-rays and blocking the incidence of light, a first scintillator and a β-ray which emit light by α-rays transmitted through the light-shielding film A second scintillator emitting light by
Condensing means for condensing light emitted by the first and second scintillators; and 1 for detecting light condensed by the condensing means.
At least one photodetector, and optically contact each other without interposing an air layer between the first and second scintillators, and adjust the emission center wavelength of the first scintillator to the second scintillator.
An αβ detector characterized by being set longer than the emission center wavelength of the scintillator.

According to the present invention, the probability of light transmission of the first scintillator through the second scintillator can be increased by optically contacting the first and second scintillators. For this reason, it becomes easy to apply a method of condensing the light of the first scintillator from the surface of the second scintillator as the light condensing means.

According to a fifth aspect of the present invention, in the αβ detector according to any one of the first to fourth aspects, the light collecting means comprises a light collecting box having an irregular reflection surface of light on an inner surface thereof. A radiation incident port having a light-shielding film is provided on one surface, and a scintillator layer comprising first and second scintillators and a photodetector for detecting light from the scintillator layer are arranged inside the radiation incident port, On the sensitive surface of the detector,
Provided is an αβ detector including a filter that selectively transmits only light in a target wavelength band.

In the first to fourth aspects of the present invention, the light of the first and second scintillators is transmitted to the reflection surface side of the second scintillator which is not facing the first scintillator side. In the case of the invention, light of two different wavelength bands is mixed and filled into the light collecting box by irregular reflection. Therefore, a filter capable of transmitting only the light of the first scintillator or a filter capable of transmitting only the light of the second scintillator is attached to each detector, and the filter is specially installed in the light collecting box. Light emission by α-rays and β-rays can be detected separately without using an electronic device for discrimination / identification. Further, the use of the light collecting box facilitates application to a large-area scintillator.

According to a sixth aspect of the present invention, in the αβ detector according to any one of the first to fourth aspects, both the light emitted from the first scintillator and the light emitted from the second scintillator can be incident as the light collecting means. , And a light guide made of a transparent material for any emission wavelength band,
An αβ detector is provided, wherein a filter that selectively transmits only light in a target wavelength band from incident light is provided between a sensitive surface of each photodetector and the light guide.

In the present invention, light of two different wavelength bands is propagated to the photodetector while being filled and diffused in the light guide in a mixed state. It is necessary to use a special electronic device for discrimination / identification by mounting a filter that can transmit only the light of the first scintillator and a filter that can transmit only the light of the second scintillator on each detector. In addition, it is possible to individually detect the light emission due to α-rays and β-rays.

According to a seventh aspect of the present invention, in the αβ detector according to any one of the first to sixth aspects, at least one of the photodetectors has a fluorescence conversion function at an edge of the second scintillator. An αβ detector characterized by being connected via a light guide is provided.

In the case of the present invention, the first scintillator and the second scintillator
Air is interposed between the scintillator and the scintillator. Since the first scintillator is made of a powder, a sintered body, or the like, light is emitted to the outside as a result of irregular reflection inside the scintillator itself. Thus, once this light has passed through the second scintillator, it is filled into the collection box and detected by a photodetector located in the collection box. Some of the light from the second scintillator also enters the collection box, which is rejected by a filter mounted on the photodetector.

In the second scintillator, since the surroundings are surrounded by air, the light is confined in the scintillator by the total reflection, and as a result, the scintillator light is collected at a high density on the edge side. By arranging a light guide including a phosphor that absorbs scintillation photons and emits light of a longer wavelength on the edge side of the second scintillator, re-emission occurs internally by fluorescence conversion. Then, as a result of the propagation action of these light guides due to total reflection, the fluorescence induced in the light of the second scintillator can be detected by the photodetectors arranged on their end faces. In the present invention, the light guide includes an optical fiber having a clad (a so-called fluorescent fiber, a wavelength shift fiber, etc.).

Further, in the light condensing method on the edge side, since the light can be condensed without largely depending on the area of the scintillator, it can be easily applied to a large area scintillator together with the light condensing box.

According to an eighth aspect of the present invention, in the αβ detector according to any one of the first to seventh aspects, the light condensing means is disposed to face the second scintillator opposite to the light-shielding film via an air layer. A fluorescent plate for condensing the light of the first scintillator by a fluorescence conversion effect; and a light guide for condensing the fluorescent light from the plate surface side of the fluorescent plate. At least one of the photodetectors includes a fluorescent light from the light guide. Is provided, and an αβ detector is provided.

According to the present invention, the light from the first scintillator is absorbed by the fluorescent plate after passing through the second scintillator, and re-emission of longer wavelength fluorescence occurs in the fluorescent plate. The re-emitted fluorescence is further guided to the photodetector via the light guide. This makes it possible to detect the induced fluorescence of the light of the first scintillator.

According to a ninth aspect of the present invention, in the αβ detector according to any one of the first to seventh aspects, the light condensing means is disposed opposite to the second scintillator on the side opposite to the light shielding film via an air layer. A fluorescent plate for condensing the light of the first scintillator by a fluorescence conversion effect, and a second light guide including a fluorescent substance that absorbs fluorescent light from an edge portion of the fluorescent plate and emits fluorescent light of a longer wavelength, At least one of the light detectors detects the fluorescence from the guide light, thereby providing an αβ detector.

According to the present invention, the light from the first scintillator is absorbed by the fluorescent plate after passing through the second scintillator, and the fluorescent light of longer wavelength is contained therein. Re-emission occurs. In this case, since the periphery of the fluorescent plate is surrounded by air, light is captured by total reflection as in the case of the second scintillator, and fluorescent light is collected at a high density on the edge side. Absorb the fluorescence generated by this fluorescent plate,
By arranging the second light guide that emits fluorescence of a longer wavelength on the side surface, it is possible to perform light collection by fluorescence conversion from the side surface similarly to the second scintillator. By arranging a photodetector at the end of the second light guide, it is possible to detect the light of the first scintillator as light that has undergone double fluorescence conversion.

According to a tenth aspect of the present invention, there is provided an αβ detecting apparatus using the αβ detector according to any one of the first to ninth aspects, wherein a signal is taken from the αβ detector light detector, and An αβ detection device comprising: a signal processing circuit that recognizes a signal having the above peak value as an optical signal from the first or second scintillator and eliminates a signal having a peak value less than the above as noise. I will provide a.

In the present invention, each photodetector is configured to separate and measure optical signals from the first and second scintillators by an optical method. However, even when there is no light input to the photodetector, there is a dark current component which may be called internal noise, and appears as a signal having a very small peak as an output electric signal. For this reason,
In the signal processing circuit, a pulse signal having a peak value equal to or higher than a certain value is recognized as an optical signal from the first scintillator or the second scintillator, and a signal less than the signal is excluded as noise, so that the optical signal and the noise are separated. Can be identified.

According to an eleventh aspect of the present invention, there is provided an αβ detector using the β detector according to any one of the first to ninth aspects, wherein a plurality of photodetectors corresponding to the same scintillator of the αβ detector are provided. A signal processing circuit that recognizes a signal corresponding to a light emitting event of the scintillator when two or more signals are detected at the same time, and eliminates the signal as noise when a single signal is detected. Provided is an αβ detection device provided with the above.

In the tenth aspect of the present invention, when the light from the scintillator is weak, the peak value and the difference of the noise may not be clearly recognized. On the other hand, in the present invention, a simultaneous counting process is performed on a plurality of photodetectors for detecting light from the same scintillator, and when signals are output simultaneously from two or more detectors, the optical signal from the scintillator is output. As a result, the optical signal and the noise can be surely distinguished by signal processing that recognizes that the signal is effective and excludes the other as noise.

According to the twelfth aspect of the present invention, the first or second aspect is provided.
A detection device using the αβ detector according to the above, wherein the αβ
The detector further includes a light attenuator between the first scintillator and the second scintillator, the second scintillator being capable of transmitting radiation to be detected and reducing the light intensity of the first scintillator. With a filter,
The light collecting means includes a light collecting box having an irregular reflection surface of light on its inner surface, and the first scintillator and the second scintillator differ depending on the difference in the signal output waveform of one or more of the αβ detectors. And a light signal discriminating means for discriminating whether the light signal is emitted from any of the scintillators.

In the apparatus of the present invention, by using the light collecting box, a scintillator having a larger area can be used as compared with the conventional switch type detector. At this time,
By interposing a light amount adjusting filter between the first scintillator and the second scintillator, the difference in light amount, which has been a problem in the related art, can be eliminated, and the light amount can be flattened. That is, when this filter is mounted on the photodetector, the amount of light is attenuated for both the first and second lights. However, with the above arrangement, only the light of the first scintillator can be attenuated. . The light of both the first and second scintillators enters the photodetector provided in the light collection box,
The signal of a large amount of light from the first α-ray scintillator is attenuated by the above-described filter, so that the signal can be adjusted to be substantially the same as the β-ray signal from the second scintillator.
As a result, the output signal of the photodetector can be input to the waveform discriminator without any adverse effect due to the difference in light amount between the first and second scintillators.
The signals of both lines can be handled with the same dynamic range, and high-sensitivity analysis can be performed.

According to the thirteenth aspect, the first or second aspect is provided.
A detection device using the αβ detector according to the above, wherein the αβ
The detector further includes a light attenuator between the first scintillator and the second scintillator, the second scintillator being capable of transmitting radiation to be detected and reducing the light intensity of the first scintillator. With a filter,
The light converging means is provided with a light guide made of a substance capable of receiving both the light emitted from the first scintillator and the second scintillator and transparent to any of the light emission wavelengths. The first scintillator and the second scintillator are separated by a difference in signal output waveform of one or more photodetectors for detecting light from the light guide of the detector.
And a signal discriminating means for discriminating whether the signal is an optical signal emitted from any of the scintillators.

In the present invention, as in the twelfth aspect,
A signal of a large light amount from the first scintillator is attenuated by an optical attenuation filter in advance, and adjusted so as to be approximately equal to a β-ray signal from the second scintillator. Differences can be flattened.

According to the fourteenth aspect of the present invention, a β-ray detecting section, a sealed air layer of a fixed volume secured on the β-ray incident surface side, and an ionization current of air due to α-rays arranged in the air layer. , A power supply device for applying a voltage to the electrode, and a microcurrent measuring means for measuring the ionization current itself.

In the present invention, attention is paid to air existing in front of the β-ray detecting section, and a minimum electrode for measuring ionization current for measuring the ionization is provided. The electrode does not need to be plate-shaped and can be made of a thin conductive wire, so that the effect of interfering with the incidence of β-rays can be minimized. By applying a potential difference to the electrodes and measuring the minute current flowing by the ionized air with a minute ammeter, a signal corresponding to the amount of α-rays can be obtained. Since the ionizing ability of β-rays is extremely small for α-rays, the contribution of β-rays to this ionization current can be neglected.

According to a fifteenth aspect of the present invention, a β-ray detecting section, an air layer of a fixed volume secured on the β-ray incident surface side, a means for sucking ionized air by α-ray at a fixed flow rate or a fixed volume, An electrode for measuring the ionization current of the air, a power supply for applying an applied voltage to the electrode, and a minute current measuring means for measuring the ionization current itself. I do.

Also in the present invention, in the same manner as in the fourteenth aspect of the present invention, it is considered that an object that interferes with the incidence of β-rays is not disposed as much as possible on the front surface of the optimized β-ray detector. The electrodes are arranged in another container, the container is connected to the closed space in front of the β-ray detector, and the ionization current is measured while sucking the air in the closed space. According to this configuration, it is not necessary to dispose any additional material on the β-ray incident surface, and the collected electric charge is always integrated while being sucked during the measurement time, so that the leakage current of the current measurement system is reduced. The effect of suppressing the influence is obtained.

According to a sixteenth aspect of the present invention, in the αβ detecting apparatus according to the fifteenth aspect, dust is adsorbed to a ventilation port of air newly introduced from the outside into a fixed volume forming an air layer serving as an α-ray detecting phase. Provided is an αβ detection device including a filter.

According to the present invention, in the structure of claim 15,
If daily and seasonal fluctuations of the natural radionuclide radon and thoron contained in the external air ventilated by suction become a problem, attach a filter to the ventilating port and install floating dust with radon and thoron attached. By absorbing and not taking in the enclosed space, alpha rays from Radon Tron,
The effect of suppressing the influence of the β-ray contribution can be obtained.

[0055]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an αβ detector according to the present invention and an αβ detection apparatus using the same will be described below with reference to the drawings.

First Embodiment (FIG. 1) The present embodiment relates to an αβ detector, and FIG. 1 is a sectional view showing the configuration.

As shown in FIG. 1, as shown in FIG.
The detector 11 has a light-shielding film 12 that can transmit α-rays and β-rays and that blocks the incidence of light on one surface (the upper surface in FIG. 1).
Is provided. This case 1
A first scintillator 14 sensitive to α-rays is disposed in parallel with the third light-shielding film 12 at a position inside the light-shielding film 3. In parallel, a second scintillator 15 sensitive to β rays is arranged. Air is present in the case 13, whereby an air layer 16 is interposed between the first and second scintillators 14 and 15.

One or more photodetectors 17 are arranged at a position (the lower part in FIG. 1) opposite to the light-shielding plate 12 in the case 13, and the first and the second photodetectors 17 are disposed on the sensitive surfaces of these photodetectors 17. The light emitted from the second scintillators 14 and 15 is
Is condensed and guided.

As the first α-ray scintillator 14,
Gd ₂ O ₂ or Y ₂ O to which ZnS (Ag), ZnCdS (Ag), Tb, Eu, Pr, or the like is added.
Such as ₂ S powder is used. As the second scintillator 15, a thin plastic scintillator of about 1 mm or the like can be used as a material that detects β-rays while suppressing the γ-ray sensitivity and transmits the light of the first scintillator 14. The thickness is determined by the amount of light required by the light detection system,
It is determined by the target β-ray energy, γ-ray sensitivity, etc., and is set differently depending on the application.

Here, in the present embodiment, (1) the emission center wavelength of the first scintillator 14 is
5 is set shorter than the emission center wavelength (first configuration example), and conversely, (2) the emission center wavelength of the first scintillator 14 is set longer than the emission center wavelength of the second scintillator 15. And a configuration (second configuration example). The first or second configuration example, that is, the relationship between the lengths of the wavelengths of the first scintillator 14 and the second scintillator 15 has individual characteristics. Any one of them can be selected and used in relation to its own light transmission characteristics, the maximum sensitivity wavelength of the photodetector, the quantum efficiency and the like.

According to such a configuration, since air is interposed between the first scintillator 14 and the second scintillator 15, the periphery of the second scintillator 15 has a value lower than its own refractive index. And the light is easily confined inside the scintillator, so that it is easy to apply a method of using the light collected at a high density on the edge side as a light condensing means for the second scintillator 15. This method will be described in a later embodiment.

Further, according to the configuration of the present embodiment, unlike the conventional configuration, an intervening substance for bonding the scintillator and optically tightly bonding is not required, and the intervening substance itself and a chemical between the intervening substance and the scintillator are not required. A structure suitable for a case where deterioration due to interaction or the like is concerned can be obtained. Further, since the independence of each of the scintillators 14 and 15 is maintained, advantages such as maintenance, inspection, and replacement of only one of the scintillators are obtained.

In the above-described first configuration example, the emission center wavelength of the scintillator 14 is changed to the second scintillator 1.
By setting the emission center wavelength to be shorter than 5, the means for optically identifying the wavelength can be used in combination, and the waveform discriminating apparatus for rise analysis can be dispensed with.

Further, in the second configuration example, by making the emission wavelength of the first scintillator 14 longer than that of the second scintillator 15, the first scintillator 14 which generally has a high transmission efficiency in the scintillator is provided. , The light having a longer wavelength is hardly absorbed by the second scintillator 15, and the probability of being absorbed and emitted by the phosphor contained in the second scintillator 15 can be reduced. 15 can be prevented from being affected by light from the first scintillator 15.

As described above, according to the present embodiment, the scintillator having different emission wavelengths has a two-layer structure, so that it is not necessary to use pulse height distribution measurement, and α and β are simultaneously and independently utilized by utilizing the difference in wavelength. Line measurements can be made.

In the present embodiment, the first scintillator 14 is powdered and applied and fixed to, for example, the back side of the light shielding film 12, that is, the inner surface of the light shielding film 12 facing the second scintillator 15 side. be able to. As a result, the α-ray transmitted through the light shielding film 12 encounters the first scintillator 14 without an extra air layer and emits light. Further, since the first scintillator 14 is fixed on the back side of the light shielding film 12,
An air layer 16 can be interposed between the second scintillator 15 and the second scintillator 15. As a result, the second scintillator 15 has a refractive index difference from air, so that a light capturing effect by total reflection occurs, and Light emitted in the scintillator 15 is confined in the scintillator, propagates, and can be collected at high density on the side surface.

Second Embodiment (FIG. 2) FIG. 2 shows an αβ detector according to a second embodiment of the present invention.

In the present embodiment, similar to the first embodiment,
A case 13 is provided, the surface of which is covered with a light-shielding film 12 that is capable of transmitting α-rays and β-rays and that blocks light from entering.
Inside the case 13, a first scintillator 14 that emits light by α-rays and a second scintillator 15 that emits light by β-ray are provided in close contact with each other without an air layer. In addition, in the case 13, the first
Focusing means 18 for effectively collecting the light of the scintillator 14 and the second scintillator 15 to the photodetector 17
Are combined.

In this embodiment, as in the first embodiment, (1) a configuration in which the emission center wavelength of the first scintillator 14 is set shorter than the emission center wavelength of the second scintillator 15 (first configuration example) ) And conversely, (2) setting the emission center wavelength of the first scintillator 14 to the second scintillator 1
5 (second configuration example), and two types of configurations are included. The first configuration example or the second configuration example has a balance with the light collecting means to be attached according to the individual characteristics of the long and short wavelengths of the first scintillator 14 and the second scintillator 15, The light transmission characteristics of the scintillator itself, or the light detector 1
7 is selected and used in relation to the maximum sensitivity wavelength of 7 and the quantum efficiency.

According to the present embodiment, by bringing the first and second scintillators 14 and 15 into close contact with each other optically, Fresnel reflection based on the difference in the refractive index due to the interposition of the air layer and the scintillator internal Internal capture due to total reflection can be reduced, and the probability of transmission of the light of the first scintillator 14 through the second scintillator 15 can be increased. For this reason, it becomes easy to apply a method that focuses on light from the surface of the second scintillator 15 that is not joined to the first scintillator 14 as the light collecting means. With such a two-layer structure, measurement of α and β can be performed simultaneously and independently using the difference in wavelength without using pulse height distribution or waveform discrimination measurement.

In this embodiment, the light collecting means based on the idea of mixing the optical outputs of the first scintillator 14 and the second scintillator 15 once and then separating them optically or electrically is used. Are suitable. Conversely, the first embodiment is suitable when it is desired to minimize the mixing.

Third Embodiment (FIG. 3) FIG. 3 shows an αβ detector according to a third embodiment of the present invention.

In this embodiment, the light collecting means 18 is formed as a light collecting box 19 which also serves as the case 13, and the inner surface 19a of the light collecting box 19 is a diffuse reflection surface coated with a diffuse reflection material. One surface of the light-collecting box 19 is opened to serve as an entrance, and α-rays, β-
A light-shielding film 12 capable of transmitting light is mounted.

Then, a scintillator layer 20 having a two-layer structure composed of the first and second scintillators 14 and 15 similar to the above-described first or second embodiment is provided on the back surface of the light-shielding film 12 in the light-collecting box 19. Is arranged. Light emitted from the first and second scintillators 14 and 15 as the scintillator layer 20 is mixed and filled by irregular reflection on the inner surface 19 a of the light collecting box 19.

The scintillator layer 2 is provided inside the light collecting box 19.
Two photodetectors 17 are arranged on the parallel droplet at the back side of the zero. As the photodetectors 17, for example, photomultiplier tubes are used. On the sensitive surface of one of the photodetectors 17a, a filter 21b that transmits only light in the emission wavelength band of the first scintillator 14 from among the mixed and filled light is mounted, and the other photodetector 17b is On the sensitive surface, a filter 21b that transmits only light in the emission wavelength band of the second scintillator 15 is mounted.

In this embodiment, optical wavelength discrimination is also performed, and the output of each photodetector 17 is used to separate the first scintillator 14 and the second scintillator 15 without using a special separation circuit. An independent signal is obtained.

According to such a configuration, the light of the first and second scintillators 14 and 15 is transmitted to the reflection surface side of the second scintillator 15 not facing the first scintillator 14 side. Different from the first and second embodiments, light having two different wavelength bands is mixed and filled in the light collecting box 19 by irregular reflection.

Therefore, the individual detectors 17a, 17b
A filter 21a that can transmit only the light of the first scintillator 14 or a filter 21b that can transmit only the light of the second scintillator 15 is mounted on the filter 21 and the filter 21a is disposed in the light collecting box 19, so that special discrimination / Emissions of α-rays and β-rays can be separately detected without using an electronic device for identification. Further, the use of the light collecting box facilitates application to a large-area scintillator.

Therefore, according to the present embodiment, α-rays and β-rays can be measured at the same time without using pulse height distribution and waveform discrimination measurement by the two-layer structure, and a large-area detector is constructed. be able to.

Fourth Embodiment (FIG. 4) FIG. 4 shows an αβ detector according to a fourth embodiment of the present invention.

In the present embodiment, one surface of the case 13 is made of the same scintillator layer 20 as in the third embodiment, and its incident surface side is formed by blocking alpha rays while blocking external light.
A light-shielding film 12 capable of transmitting β rays is mounted. A light guide 22 is provided inside the case 13 so as to be in close contact with the second scintillator 15 in the scintillator layer 20.

Further, in the state of being in close contact with the light guide 22, the photodetectors 17 individually provided with the filters 21 that transmit only one of the emission wavelength bands of the first scintillator 14 and the second scintillator 15 are provided. There are two deployed. As in the third embodiment, one of the two photodetectors 17 is for α detection and the other is for β detection. In this way, the first scintillator 14 and the second Discrimination from the scintillator 15 is performed.

In the third embodiment described above, light is filled inside the light collecting box 19 whose inner surface is a diffusely reflecting surface, but in the fourth embodiment, light is filled inside the light guide 22. Has become. Therefore, the light guide 22
The shape and size of the light detector 17 can be arbitrarily set.
Can be applied.

In some cases, it is also effective to polish the outer peripheral surface that is not joined to the second scintillator 15 so as to be capable of total reflection, or to process it so that it is specularly reflected or irregularly reflected.

FIG. 4 shows a configuration in which the photodetector 17 is disposed in close contact with the outside of the light guide 22.
A concave portion is provided in the light guide 22 and the light detector 1 is provided therein.
Embedding 7 is also effective in some cases.

According to the present embodiment, α-ray and β-ray can be measured simultaneously without using pulse height distribution and waveform discrimination measurement by forming a two-layer structure.
The application of a small-sized photodetector becomes possible, and the size of the device can be reduced.

Fifth Embodiment (FIGS. 5 and 6) FIG. 5 shows an αβ detector according to a fifth embodiment of the present invention, and FIG. 6 shows a plan configuration of the second scintillator 15 in FIG. .

In this embodiment, as in the third embodiment,
A light collecting box 19 serving also as the case 13 is provided.
On the incident surface side of one of the
A light-shielding film 12 capable of transmitting rays and β rays is mounted. Inside the light shielding film 12, a first scintillator 14 and a second scintillator 15 separated from each other by an air layer 16 are arranged.

In the light collecting box 19, the second scintillator 1
5, two detectors 17 are accommodated, and these light detectors 17 are equipped with a filter 21 for selectively transmitting light from the first scintillator 14,
The treatment is performed so as to be insensitive to light emitted from the second scintillator 15 after escaping the internal capture.

On the other hand, fluorescent conversion light guides and the like are attached to both side edges of the second scintillator 15 so that light collection using the fluorescent conversion action of the second scintillator 15 is performed.

That is, as shown in FIGS. 5 and 6,
Fluorescence conversion light guides 23 are provided on the edges of the second scintillator 15 that are parallel to each other, and a photodetector 17c is attached to one end of each of the fluorescence conversion light guides 23. The fluorescence conversion light guide 23 is a material obtained by adding a phosphor to a resin or the like, and absorbs scintillation light,
It has the function of re-emitting long-wavelength light (fluorescence). Note that the fluorescence conversion light guide 23 may be a fiber-like material (a so-called fluorescent fiber, a wavelength shift fiber, or the like) in which a similar phosphor is added to the core.
It can be used appropriately according to the joining method and the like.

According to such a configuration, the air layer 16 is provided between the first scintillator 14 and the second scintillator 15.
The first scintillator 14 is made of a powder, a sintered body, or the like, so that light is emitted to the outside as a result of irregular reflection inside the scintillator itself. Therefore, the light from the first scintillator 14 once passes through the second scintillator 15 and then fills the light collecting box 19 and is detected by the photodetector 17 arranged in the light collecting box 19. . Part of the light from the second scintillator 15 also enters the light collection box 17, but is excluded by the filter 21 mounted on the light detector 17.

In the second scintillator 15, since the surroundings are surrounded by air, the light is confined in the scintillator by the total reflection, and as a result, more than half of the light is collected at a high density on the edge side. . A fluorescence conversion light guide 23 is arranged on the edge side of the second scintillator 15, and in this fluorescence conversion light guide 23, re-emission occurs inside due to fluorescence conversion. As a result, the fluorescence induced by the light of the second scintillator 15 can be detected by the photodetectors 17c arranged on those end faces.

In such a light condensing method on the edge side of the second scintillator 15, light can be condensed without largely depending on the area of the scintillator. Becomes easier.

According to the present embodiment, by forming a two-layer structure, it is possible to simultaneously measure α-rays and β-rays without using pulse height distribution or waveform discrimination measurement, and to use a detector having a larger area. Can be configured.

Although not shown, the second scintillator 15 can be provided with the fluorescence conversion light guide 23 not only on two parallel sides but also on the entire periphery. In addition, measures such as specular reflection or irregular reflection may be performed on an unused end of the fluorescence conversion light guide 23 or two unused sides of the second scintillator 15 where the light guide 23 is not mounted. With these configurations, light use efficiency can be improved.

Sixth Embodiment (FIG. 7) FIG. 7 shows an αβ detector according to a sixth embodiment of the present invention.

In this embodiment, a first scintillator 14 and a second scintillator, which are separated from each other by an air layer, are arranged on one surface of a non-reflective case 13.
In this device, a fluorescent plate 24 is provided at a position where light from the first scintillator 14 that has passed through the second scintillator 15 can enter, and the photodetector 17 is provided in close contact with the fluorescent plate 24. The photodetector 17 is provided with a filter 21 for blocking light components from the second scintillator 15 incident on the light guide 22.

The second scintillator 15 and the fluorescent screen 2
4, an air layer is interposed. Further, as in the fifth embodiment, a fluorescence conversion light guide 24 and a photodetector 17c are mounted on the edge of the second scintillator 15, and a light-collecting structure by fluorescence conversion on the edge is adopted. .

Thus, the light from the first scintillator 14 passes through the second scintillator 15, enters the fluorescent screen 24, and undergoes fluorescence conversion. The emitted fluorescent light is the fluorescent plate 2
The light enters the light guide 22 provided in close contact with the light guide 4, reaches the light detector 17, and is detected there. The light from the second scintillator 15 is detected by the fluorescence conversion light guide 23 provided on the edge and the photodetector 17c mounted on the end.

According to the present embodiment also, by forming a two-layer structure, pulse height distribution and waveform discrimination measurement are not used.
At the same time, measurement of α-rays and β-rays can be performed, and downsizing of the photodetector 17 to be used, and further downsizing of the αβ detection device can be achieved.

Note that the shape of the fluorescent plate 24 is
2, the light guide 22 can be omitted.

Seventh Embodiment (FIG. 8) FIG. 8 shows an αβ detector according to a seventh embodiment of the present invention.

In this embodiment, similarly to the sixth embodiment, the first scintillator 14 and the second scintillator 15 separated from each other by the air layer 16 in the non-reflective case 13.
And a fluorescence conversion light guide 23 and a photodetector 17c are attached to the edge of the second scintillator 15,
A light-collecting structure based on fluorescence conversion on the edge side is employed.

Further, a fluorescent plate 24 is provided at a position where light from the first scintillator 14 that has passed through the second scintillator 15 can enter.

In this case, the second light guide 25 and the photodetector 17d are mounted on the edge of the fluorescent plate 24 in the same manner as the edge of the second scintillator 15, and the light is collected by fluorescence conversion on the edge. An optical structure is employed. That is, the light of the first scintillator 14 is converted into fluorescent light inside the fluorescent plate 24, and the fluorescent light is further double-converted into fluorescent light having a longer wavelength on the side edge side.

However, the phosphor contained in the second fluorescent conversion light guide 25 for the fluorescent plate 24 is different from that used for the second scintillator 15. That is, a fluorescent substance that absorbs light from the second scintillator 15 and converts the fluorescent light is applied to the fluorescent substance provided in the second scintillator 15, and the fluorescent substance from the fluorescent plate 24 is fluorescent light that is provided in the fluorescent screen 24. Those containing phosphors that can be absorbed and converted to longer wavelength fluorescence have been selected and applied.

According to such a configuration, the first scintillator 14 radiates into the air and the second scintillator 1
The light incident on 5 is hardly captured inside the second scintillator 15. Even when the light from the first scintillator 14 is directly incident on the fluorescence conversion light guide 23 provided in the second scintillator 15, the fluorescence signal as an erroneous signal may not be generated because the absorption wavelength bands are different. Absent.

According to the present embodiment also, by forming a two-layer structure, the pulse height distribution and the waveform discrimination measurement are not used.
At the same time, the measurement of α-rays and β-rays can be performed, and the light is condensed on both side edges of the fluorescent screen 24, so that a large-area and thin detector can be configured.

Eighth Embodiment (FIG. 9) This embodiment is the same as the αβ shown in the first to seventh embodiments.
FIG. 9 shows a schematic configuration of an αβ detection apparatus using a detector.

As shown in FIG. 9, in this embodiment, αβ
An output signal of the photodetector 17 of the detector 11 is processed through a wave height discrimination device 26 as a signal processing circuit. That is, if at least one photodetector 17 corresponding to each scintillator of the above-described scintillator having a two-layer structure is used, signal detection can be performed by this method. The pulse height discrimination device 26 recognizes a pulse signal having a peak value equal to or higher than a predetermined value as an optical signal from the first or second scintillator, and removes a signal lower than the pulse signal as noise.

According to the present embodiment, an optical signal can be identified only when a signal equal to or higher than the dark current noise of the photodetector 17 arrives.

Ninth Embodiment (FIG. 10) This embodiment also relates to an αβ detector using the αβ detector, and FIG. 10 shows the configuration.

In the present embodiment, the output signals of the plurality of photodetectors 17 are converted to the coincidence identification device 2 as a signal processing circuit.
7 to be processed. That is, in the photodetector 17 corresponding to a scintillator having a two-layer structure, an analog adder circuit having a band capable of amplifying a signal is required when a plurality of detectors are used or when signals from the respective detectors are added. However, it is simpler to employ a coincidence circuit that detects the establishment of the logical product of the logical signals of the detection signals.

In the example of FIG. 10, three input signals A, B, C
In contrast, when a logical product of any two input signals is established, the input signal is identified as a signal.

According to the present embodiment adopting such a method, it is possible to exclude the counting of mutually uncorrelated dark current noise generated in the ordinary photodetector 17 and to extract only the signal.

Tenth Embodiment (FIG. 11) FIG. 11 shows an αβ detecting apparatus according to a tenth embodiment of the present invention.

In the present embodiment, two types of scintillators 14 and 15 having different emission wavelengths are used, and an inner reflection type light collecting box 19 is provided. On the incident surface side of the light-collecting box 19, a light-shielding film 12 capable of transmitting α-rays and β-rays while shielding light from the outside is provided inside the first and first light-shielding films.
Second scintillators 14, 15 are arranged.

The light from the first scintillator 14 and the light from the second scintillator 15 are mixed and filled in the light collecting box 19. In the example of FIG. 11, two photodetectors 17 are arranged inside the light collection box 19, and a photomultiplier tube is used as the photodetector 17.

[0120] An optical attenuation filter 28 is interposed between the first scintillator 14 and the second scintillator 15. As a material capable of attenuating light and transmitting β-rays, the same material as that of the light-shielding film 12 can be used. For example, the material can be adjusted by adjusting the thickness of aluminum concentrated on a thin polyester film. it can. The first scintillator 14 and the optical attenuation filter 2
8 and between them and the second scintillator 15, an air layer may be interposed therebetween, or they may be optically adhered to each other.

According to such a configuration, due to the presence of the optical attenuating filter 28, the emission of α-rays emitted from the first scintillator 14 is weakened, and the light collecting box 19 is filled. Note that the output of the second scintillator 15 is not attenuated.

The signal from the photodetector 17 is input to a signal processing circuit 29, and is separately or added to each other.
Alternatively, a waveform is discriminated from an output signal of a photodetector which is gated by coincidence counting information and passes only a signal derived from an optical signal. Conventionally, the signal level due to α-rays is large, and sufficient waveform discrimination cannot be obtained by waveform discrimination optimized for this. However, according to the present embodiment, the light amount is adjusted using the optical attenuation filter 28. By doing
The input voltage range to a signal processing circuit such as a waveform discriminating circuit can be optimized and used.

Eleventh Embodiment (FIG. 12) FIG. 12 shows an αβ detector according to an eleventh embodiment of the present invention.

In this embodiment, the light attenuating filter 28 is disposed between the first scintillator 14 and the second scintillator 15, but the light guide 22 is provided so as to be in close contact with the second scintillator 15. A photodetector 17 is provided in close contact with the photodetector 17.

With such a configuration as well, the presence of the optical attenuation filter 28 weakens the emission of α-rays emitted from the first scintillator 14 and fills the light guide 22. Therefore, also in the present embodiment, since the light amount can be adjusted as in the tenth embodiment, the input voltage range to the signal processing circuit 29 such as the waveform discrimination circuit can be optimized and used.

Twelfth Embodiment (FIG. 13) FIG. 13 shows an αβ detector according to a twelfth embodiment of the present invention.

In the present embodiment, the β-ray detector 30 is housed in the case 13, and the light-shielding film 12 is mounted on the incident surface of the case 13 for the α-ray and the β-ray. And a closed space formed by the case 13. This space is filled with air 31 and two or more electrodes 32 are set.

A voltage is applied to these electrodes 32 by a bias power supply 33 so that a polarity necessary for collecting positively ionized ions, ionized electrons or negatively ionized ions is formed. Then, ions or electrons are collected by the electrode 33, and the induced current is measured by the minute ammeter 34.

Although the air ionization ability of β-rays is extremely low and generates only an induced current that is less than the leakage current level of a general microammeter 34, the ionization ability of α-rays is much larger than that of β-rays. The measurement can be performed by the minute ammeter 34.
In two cases, the electrodes 32 are unipolar with respect to the ground potential, but in three cases they can act as positive and negative collecting electrodes.

According to the present embodiment, the α-rays are emitted from the β-ray detector 3
It can be measured from the ionization current of air on the 0 incident surface side, and β-ray detection can be independently measured by a dedicated detector. In addition, since the α-ray detection layer is basically made of air, the energy lost when β-rays pass through the α-ray detection layer can be kept to a minimum.

Thirteenth Embodiment (FIG. 14) FIG. 14 shows an αβ detector according to a thirteenth embodiment of the present invention.

This embodiment is different from the twelfth embodiment in that the ionization current in a constant volume in a closed space is measured.
In this method, measurement is performed outside the case 13 while sucking air.

That is, also in the present embodiment, some β-ray detector 30 is housed in the case 13 and the α-ray
The light-shielding film 12 is mounted on the β-ray incident surface, and a space formed by the β-ray detector 30, the light-shielding film 12 and the case 13 is provided. The case 13 is provided with a ventilation port 35 through which air can be taken in from the outside. A suction device 36 disposed outside and the case 13 are connected by an intake line 37. Between the suction device 36 and the suction line 37, two or more electrodes 3 for measuring the ionization current of air are provided.
A voltage 8 having a required polarity is applied to the electrode 38 from a bias power supply 39, and a minute ammeter 34 for measuring the flowing ionization current is connected to the electrode 38.

According to such a configuration, since the ionization current of air having a volume equal to or larger than the volume of the closed space can be measured, the effective α-ray detection limit value can be improved. Also,
Compared with the twelfth embodiment, although an additional device is required, since there is no electrode in the β-ray passage portion, the energy loss when β-ray passes through the α-ray detection layer is reduced to a minimum value by air. You can keep it.

Fourteenth Embodiment (FIG. 15) In the present embodiment, a replaceable adsorption filter 40 for adsorbing fine particles is mounted on the portion of the ventilation port 35 in the fourteenth embodiment.

As the adsorption filter 40, a general filter for adsorbing floating dust similar to that used in a dust collecting apparatus for radiation dust can be used. Other configurations are the same as those in FIG.

According to this structure, the daughter nuclide radon-throne originating from the radioactive nuclide from the natural uranium-thorium series contained in the air taken into the outside, or the dust ionized and adsorbed by the nuclide is absorbed. It can be filtered by the filter 40.

Therefore, according to the present embodiment, it is possible to suppress the influence of the fluctuation of the α-ray background in the air layer on the intake side.

[0139]

As described in detail above, claims 1 to 11
According to the invention of the above, by disposing in two layers using scintillators having two different wavelengths and independently condensing light from each scintillator by wavelength discrimination or fluorescence conversion, both α rays and β rays Without using a complex wave height analyzer or waveform discriminator,
With a simple counting device, it is possible to separately and separately measure the α battle and the β battle. Further, since the sensitive portions of α-ray and β-ray can be handled independently, the sensitivity maintenance of β-ray and the suppression of the sensitivity of γ-ray can be optimized without considering the influence of α-ray.
In addition, αβ detection can be performed well even with a large area product detector.

According to the twelfth and thirteenth aspects of the present invention, since the signal amplitude levels of α-rays and β-rays can be adjusted within the same level range, the large optical output level of the conventional α-rays is It is possible to solve the problem that it is difficult to optimize the sensitivity to β-rays and γ-rays by determining the range or the like, or the sensitivity itself of β-rays decreases.

Further, according to the present invention, air is used as the α-ray detecting layer through which β-rays must be transmitted simultaneously and independently for independent measurement, and α-rays are detected by air ionization. By using a structure that combines
Extra energy loss of β rays can be eliminated.
In addition, since the sensitive portions for α-rays and β-rays can be handled independently, it is possible to optimize the maintenance of the sensitivity of β-rays and the suppression of the sensitivity of γ-rays without considering the influence of α-rays.

[Brief description of the drawings]

FIG. 1 is a diagram showing an αβ detector according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an αβ detector according to a second embodiment of the present invention.

FIG. 3 is a diagram showing an αβ detector according to a third embodiment of the present invention.

FIG. 4 is a diagram showing an αβ detector according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing an αβ detector according to a fifth embodiment of the present invention.

FIG. 6 is a plan view of a second scintillator in FIG. 5;

FIG. 7 is a diagram showing an αβ detector according to a sixth embodiment of the present invention.

FIG. 8 is a diagram showing an αβ detector according to a seventh embodiment of the present invention.

FIG. 9 is a diagram showing an αβ detection device according to an eighth embodiment of the present invention.

FIG. 10 is a diagram showing an αβ detection device according to a ninth embodiment of the present invention.

FIG. 11 is a diagram showing an αβ detection device according to a tenth embodiment of the present invention.

FIG. 12 is a diagram showing an αβ detection device according to an eleventh embodiment of the present invention.

FIG. 13 is a diagram showing an αβ detection device according to a twelfth embodiment of the present invention.

FIG. 14 is a diagram showing an αβ detection device according to a thirteenth embodiment of the present invention.

FIG. 15 is a diagram showing an αβ detection device according to a fourteenth embodiment of the present invention.

FIG. 16 is a diagram showing an example of a conventional technique.

FIG. 17 is a diagram showing another example of the related art.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 αβ detector 12 light shielding film 13 case 14 first scintillator 15 second scintillator 16 air layer 17, 17a, 17b, 17c, 17d photodetector 18 light collector 19 light collector box 19a inner surface 20 scintillator layer 21 filter 22 Light Guide 23 Fluorescence Conversion Light Guide 24 Fluorescent Plate 25 Second Fluorescence Conversion Light Guide 26 Wave Height Discrimination Device 27 Simultaneous Counting Identification Device 28 Optical Attenuation Filter 29 Signal Processing Circuit 30 β-ray Detector 31 Air 32 Electrode 33 Power Supply for Bias 34 Microcurrent Total 35 Ventilation port 36 Suction device 37 Intake line 38 Electrode 39 Power supply for bias 40 Adsorption filter

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01T 1/185 G01T 1/185 A 7/04 7/04 (72) Inventor Yoshiaki Ohara Fuchu-shi, Tokyo 1 Toshiba Town Fuchu Plant, Toshiba Corporation (72) Inventor Soichiro Morimoto 8 Shingsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture F-term (reference) 2G088 EE06 EE12 FF05 FF06 GG01 GG09 GG11 GG13 GG14 GG16 HH03 JJ01 JJ31 KK01 KK02 KK15 KK28 KK29

Claims (16)

[Claims] 1. A light-shielding film capable of transmitting α-rays and β-rays and blocking the incidence of light, a first scintillator emitting light by α-rays passing through the light-shielding film, and a second scintillator emitting light by β-rays. A scintillator, a light condensing means for condensing light emitted by the first and second scintillators, and one or more photodetectors for detecting light condensed by the light condensing means, An αβ detector characterized in that an air layer is interposed between the first and second scintillators, and the emission center wavelength of the first scintillator is set shorter than the emission center wavelength of the second scintillator. 2. A light-shielding film capable of transmitting α-rays and β-rays and capable of blocking the incidence of light, a first scintillator emitting light by α-rays passing through the light-shielding film, and a second scintillator emitting light by β-rays. A scintillator, a light condensing means for condensing light emitted by the first and second scintillators, and one or more photodetectors for detecting light condensed by the light condensing means, An αβ detector characterized in that an air layer is interposed between the first and second scintillators, and the emission center wavelength of the first scintillator is set longer than the emission center wavelength of the second scintillator. 3. A light-shielding film capable of transmitting α-rays and β-rays and blocking the incidence of light, a first scintillator emitting light by α-rays passing through the light-shielding film, and a second scintillator emitting light by β-rays. A scintillator, a light condensing means for condensing light emitted by the first and second scintillators, and one or more photodetectors for detecting light condensed by the light condensing means, The first and second scintillators are optically adhered to each other without an air layer therebetween, and the emission center wavelength of the first scintillator is set shorter than the emission center wavelength of the second scintillator. Αβ detector. 4. A light-shielding film capable of transmitting α-rays and β-rays and capable of blocking the incidence of light, a first scintillator emitting light by α-rays passing through the light-shielding film, and a second scintillator emitting light by β-rays. A scintillator, a light condensing means for condensing light emitted by the first and second scintillators, and one or more photodetectors for detecting light condensed by the light condensing means, The first and second scintillators are optically adhered to each other without an air layer therebetween, and the emission center wavelength of the first scintillator is set longer than the emission center wavelength of the second scintillator. Αβ detector. 5. The αβ detector according to claim 1, further comprising a light-collecting unit having a light-reflecting surface on its inner surface as a light-condensing means, and a light-shielding film on one surface of the light-collecting box. A scintillator layer composed of first and second scintillators and a photodetector for detecting light from the scintillator layer are arranged inside the radiation entrance, and the sensitivity of each of the photodetectors is increased. An αβ detector characterized in that a filter for selectively transmitting only light in a target wavelength band is provided on a surface. 6. The αβ detector according to claim 1, wherein both light emitted from the first scintillator and the light emitted from the second scintillator can be incident, and any one of the light emitted from the first scintillator and the second scintillator can be used as the light condensing means. A light guide made of a material that is also transparent to the wavelength band is provided, and only light in the target wavelength band from incident light is selectively transmitted between the sensitive surface of each photodetector and the light guide. An αβ detector comprising a filter. 7. The αβ detector according to claim 1, wherein at least one of the photodetectors is provided at an edge of the second scintillator via a light guide having a fluorescence conversion function. Αβ characterized by being connected
Detector. 8. The αβ detector according to any one of claims 1 to 7, wherein the light condensing means includes a first scintillator, which is opposed to the second scintillator on the side opposite to the light-shielding film via an air layer. A fluorescent plate for condensing light by a fluorescence conversion action, and a light guide for condensing fluorescence from the plate surface side of the fluorescent plate; at least one of the photodetectors detects fluorescence from the light guide; Αβ detector characterized by the following. 9. The αβ detector according to claim 1, wherein the light condensing means includes a first scintillator disposed opposite to the second scintillator on the side opposite to the light-shielding film via an air layer. A fluorescent plate for condensing light by a fluorescent conversion function, and a second light guide including a fluorescent substance that absorbs fluorescent light from an edge portion of the fluorescent plate and emits fluorescent light of a longer wavelength, and includes at least a light detector At least one of the αβ detectors detects fluorescence from the guide light. 10. An αβ detector using the αβ detector according to claim 1, wherein the αβ detector
A signal which takes in a signal from a detector of detector light, recognizes a signal having a peak value equal to or higher than a certain value as an optical signal from the first or second scintillator, and eliminates a signal having a peak value lower than the above as noise. An αβ detection device comprising a processing circuit. 11. An αβ detection device using the β detector according to any one of claims 1 to 9, wherein signals are taken from a plurality of photodetectors corresponding to the same scintillator of the αβ detector, When two or more signals are detected at the same time, it is recognized as corresponding to a light emitting event of the scintillator,
A signal processing circuit for removing a signal as noise when a single signal is detected.
Detection device. 12. A detection apparatus using the αβ detector according to claim 1 or 2, wherein the αβ detector further includes a second scintillator between the first scintillator and the second scintillator. A light-absorbing filter capable of transmitting radiation to be detected and reducing the light intensity of the first scintillator, and having a light-collecting box having an irregular reflection surface of light on the inner surface as light-collecting means And an optical signal identification for identifying whether the optical signal is emitted from one of the first scintillator and the second scintillator based on a difference in signal output waveform of one or more photodetectors of the αβ detector. An αβ detection device comprising means. 13. A detecting apparatus using the αβ detector according to claim 1 or 2, wherein the αβ detector further comprises a second scintillator between the first scintillator and the second scintillator. It has a light attenuating filter that can transmit radiation to be detected and reduces the intensity of light of the first scintillator, and emits light from the first scintillator and the second scintillator as focusing means. And at least one light detector for detecting light from the light guide of the αβ detector. And a signal discriminating means for discriminating whether the light signal is emitted from one of the first scintillator and the second scintillator based on a difference in the signal output waveform. Αβ detection device. 14. A β-ray detecting section, a sealed air layer of a fixed volume secured on the β-ray incident surface side, and arranged in the air layer, for measuring the ionization current of air due to α-rays. An αβ detection device comprising: an electrode; a power supply device for applying a voltage to the electrode; and a minute current measuring means for measuring an ionization current itself. 15. A β-ray detecting section, an air layer having a constant volume secured on the β-ray incident surface side, means for sucking ionized air by α-ray at a constant flow rate or a constant volume, and an ionization current of the sucked air. Characterized by comprising an electrode for measuring the ionization current, a power supply device for applying an applied voltage to the electrode, and a minute current measuring means for measuring the ionization current itself.
Detection device. 16. The αβ detection device according to claim 15, further comprising a filter for adsorbing dust to a ventilation port of air newly introduced from the outside in a fixed volume forming an air layer serving as an α-ray detection phase. An αβ detection device characterized by the above-mentioned.