JPH09127246A - Radiation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a radiation detector which can be used under high or low temperature environment deviating from a possible temperature range by forming a fluid channel of a material transmitting radiation easily and feeding a fluid for keeping a scintillation fiber within a predetermined usable temperature range through the channel. SOLUTION: A channel forming means 4 is formed of a thin aluminum material which transmits a radiation to be measured easily and can be bent easily at the time of installing a scintillation fiber 1. Consequently, a heat insulation fluid, e.g. water or air, can be employed easily and the radiation is transmitted easily and measured. When the fiber 1 is laid at a site where the temperature is 50 deg.C or above, the temperature of the heat insulation fluid is raised through the means 4 but the fluid is circulated through the channel by a fluid transfer means 7 and cooled by a heat-exchanger 6. Consequently, the fluid is kept constantly at a temperature of 50 deg.C or below thus keeping the temperature of fiber 1 constantly at 50 deg.C or below. When the ambient temperature is -20 deg.C or below, the heat insulation fluid is heated by the heat-exchanger 6 thus keeping the temperature of fiber 1 constantly at -20 deg.C or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distribution type radiation detector using a scintillation fiber for detecting the incident position of radiation or the radiation intensity.
In particular, the present invention relates to a radiation detector used in a high temperature environment or a low temperature environment.

[0002]

2. Description of the Related Art FIG. 8 is a block diagram showing a conventional distributed radiation detector using a conventional scintillation fiber shown in page 44 of the proceedings of the next generation radiation measurement system research group. In the figure, 1 is a scintillation fiber, 12 is radiation incident on the scintillation fiber 1, 13a and 13b are optical pulses generated by fluorescence in the scintillation fiber 1 by the incident radiation 12, and 14a and 14b are provided at both ends of the scintillation fiber 1. Light receiving elements, 15a and 15
b is a preamplifier for amplifying the signals from the light receiving elements 14a and 14b, and 16a and 16b are preamplifiers 15a and 15b.
The constant fraction discriminator for adjusting the waveform of the signal amplified by 17, the signal delay circuit 17 for delaying the signal from the constant fraction discriminator 16a, and the reference numeral 18 for the signal from the constant fraction discriminator 16b and the signal delay circuit 17 , And a time wave height converter that outputs electric pulses having wave heights proportional to the time difference between these signals, 19 is an analog-digital converter that converts the electric pulse from the time wave height converter 18 into a digital signal, 20 Is a multi-channel wave height analyzer that analyzes the signal from the analog-digital converter 19.

Next, the operation will be described. When the radiation 12 is incident on the scintillation fiber 1, fluorescence is generated in the scintillation fiber 1, and the optical pulses 13a and 13b due to this fluorescence propagate toward both ends of the scintillation fiber 1, respectively. These light pulses 13a and 13b are incident on the light receiving elements 14a and 14b provided at both ends of the scintillation fiber 1, respectively, and converted into electric pulse signals. These electric pulse signals pass through the preamplifiers 15a and 15b, the constant fraction discriminators 16a and 16b, and the signal delay circuit 17, respectively, and are subjected to signal processing, and input to the time-to-peak converter 18. The time-to-wave height converter 18 outputs an electric pulse signal having a wave height proportional to the time difference between the optical pulses 13a and 13b reaching the respective light receiving elements 14a and 14b from these input signals, and the analog-to-digital converter 19 is output. It is input to the multi-channel wave height analyzer 20 via. The input position of the radiation 12 can be known by discriminating the pulse height of the input signal by the multi-channel pulse height analyzer 20, and the radiation dose rate can be detected from the count number of the signal.

[0004]

The conventional radiation detector of distribution type using scintillation fiber is constructed as described above, and the scintillation fiber generally has a core material 2 made of polystyrene as shown in a sectional view in FIG. It is made of polymethylmethacrylate clad material 3, and the usable temperature range of these materials is from -20 ° C to 50 ° C. Therefore, in a low temperature environment of -20 ° C or lower or high temperature of 50 ° C or higher. There is a problem that the scintillation fiber 1 cannot be installed and used in the environment.

The present invention has been made to solve the above problems, and obtains a radiation detector which can be used in a low temperature or high temperature environment outside the usable temperature range determined by the material of the scintillation fiber. With the goal.

[0006]

A radiation detector according to claim 1 of the present invention forms a fluid passage around a scintillation fiber with a material that easily transmits radiation, and the scintillation fiber is provided in this passage. A heat-retaining fluid that keeps the temperature within a predetermined usable temperature range is made to flow.

According to a second aspect of the present invention, there is provided a radiation detector comprising:
It is a fluid having a refractive index lower than that of light of scintillation fibers such as water or air circulating in a closed circuit via a heat exchanger.

Further, the radiation detector according to claim 3 of the present invention is provided with a heat insulating material surrounding the scintillation fiber.

Further, in the radiation detector according to the fourth aspect of the present invention, a plurality of scintillation fibers are arranged in parallel, and the scintillation fibers are provided so that their outer circumferences are in contact with each other to form a flow path for forming a fluid passage. Means, a heat-retaining fluid which is guided to the flow path and keeps the scintillation fiber within a predetermined usable temperature range, and a heat insulating material which surrounds the flow path forming means and the plurality of scintillation fibers are provided.

Further, in a radiation detector according to a fifth aspect of the present invention, the material of the flow path forming means of the radiation detector in the fourth aspect is formed of a material such as copper which hardly transmits radiation.

A radiation detector according to a sixth aspect of the present invention is such that the outer periphery of the flow path forming means of the radiation detector according to the fourth aspect is formed in surface contact with the outer periphery of a plurality of scintillation fibers. .

[0012]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1 is a configuration diagram showing the overall configuration of the radiation detector of the present invention. In the figure, 1 is a scintillation fiber, 4 is a flow path forming means for forming a flow path of a fluid around the scintillation fiber 1, and its mounting details are shown in sectional views in FIGS. 6 is a heat exchanger for making the temperature of the fluid flowing in the flow channel a predetermined temperature at which the scintillation fiber 1 can be used, and 7 is a fluid such as a pump provided for guiding the fluid into the flow channel forming means 4. It is a transfer means. In addition, in FIG. 2 and FIG.
The scintillation fiber 1 is composed of a core material 2 and a clad material 3 made of the same material as the conventional one. The flow path forming means 4 is made of a material such as an aluminum tube through which radiation can easily pass, and the scintillation fiber 1 is fixed to a substantially central portion thereof by a holding material 5 of the same material. Reference numeral 8 is a packing provided in the passage of the scintillation fiber 1 of the flow passage forming means 4 to prevent the fluid from leaking in the flow passage, and 9 is a fluid transfer means into the flow passage formed by the flow passage forming means 4. It is a heat-retaining fluid guided by 7, and is water or air heated or cooled to a predetermined temperature at which the scintillation fiber 1 can be used in the heat exchanger 6. Since the light receiving elements 14a and 14b and the subsequent elements are the same as the conventional ones, description thereof will be omitted.

Next, the operation will be described. The flow path forming means 4 is formed of a thin aluminum material, and easily transmits the radiation to be measured, and at the same time, when the scintillation fiber 1 is installed, it is easily bent.
The heat-retaining fluid 9 is also water or air, and the radiation to be measured is easily transmitted. Therefore, it can be installed in the same manner as the conventional one and the radiation can be measured. Here, for example, when the ambient temperature of the place where the scintillation fiber 1 is installed is 50 ° C. or higher, the temperature of the heat retaining fluid 9 rises via the flow path forming means 4, but the heat retaining fluid 9 is transferred to the fluid transfer means 7. Circulates in the flow path due to, is guided to the heat exchanger 6 and is cooled,
The heat-retaining fluid 9 is always 50 ° C. or lower, and the temperature of the scintillation fiber 1 can be always kept at 50 ° C. or lower. When the ambient temperature of the installation site is -20 ° C or lower, the heat retaining fluid 9 is heated by the heat exchanger 6 and the temperature of the scintillation fiber 1 is always kept at -20 ° C or higher, as described above. be able to.

Embodiment 2 FIG. Further, in FIG. 3, the scintillation fiber 1 is composed of a core material 2 and a clad material 3 surrounding the core material 2. Here, the material of the core material 2 is polystyrene having a light refractive index of 1.59, the material of the clad material 3 is polymethylmethacrylate having a light refractive index of 1.49, and the heat retaining fluid 9 is the core material 2 of the scintillation fiber 1 and A material having a light refractive index lower than that of the clad material 3, for example, water having a light refractive index of 1.33 or air having a light refractive index of 1.00 is used.

When the radiation enters the core material 2 of the scintillation fiber 1, fluorescence is generated there, and the core material 2
The light is reflected at the interface between the core material 2 and the clad material 3, and the light propagates in the core material 2 toward both ends of the scintillation fiber 1. The clad material 3 passes through the interface between the core material 2 and the clad material 3.
The light leaked into the core material 2 is reflected at the interface between the clad material 3 and the heat retaining fluid 9 and returned to the core material 2. Therefore, the clad material 3
As compared with the case where there is no reflection at the interface between the heat-retaining fluid 9 and the heat-retaining fluid 9, the transmission loss is reduced, and the transmission efficiency is improved accordingly, so that the sensitivity of the detector is improved and the detection length and the transmission distance can be lengthened. This is because the heat-retaining fluid 9 has a light refractive index lower than that of the core material 2 and the clad material 3 of the scintillation fiber 1 and the heat-retaining fluid 9 circulates in the closed circuit. This occurs because the interface between the heat insulating fluid 3 and the heat insulating fluid 9 is not contaminated by dust or the like. In this example, as shown in FIG. 4, for example, even if the clad material 3 is omitted, light can be propagated by being reflected at the interface between the core material 2 and the heat retaining fluid 9, so that the clad material 3 is inexpensive and economical. It is also possible to make the device excellent in

Embodiment 3 FIG. 5 shows another embodiment of the present invention. Reference numeral 10 is a heat insulating material made of a material such as glass wool or urethane foam, which has a low density and a low natural radioactivity, which transmits radiation well, and scintillation. It surrounds the periphery of the fiber 1. Reference numeral 11 denotes a cable case that protects the heat insulating material 10, and may be made of any material as long as it can easily transmit radiation.
With this configuration, the heat exchanger 6 and the fluid transfer means 7 described in the first embodiment are unnecessary, and particularly when the scintillation fiber 1 is installed in a place outside the usable temperature range for a short time, or when radiation is applied. It is possible to provide a simple and inexpensive configuration, which is most suitable for the case where the apparatus is moved to the measurement location only for measurement and installed.

Embodiment 4 FIG. 6 shows still another embodiment of the present invention, in which 41 is a flow path forming means for forming a flow path of the heat retaining fluid 9, and a plurality of scintillation fibers 1 are arranged in contact with the outer peripheral surface thereof. And
For example, it is formed of a material such as copper that is difficult to transmit radiation and is easily bent. 10 is a heat insulating material which also functions as a filling material, and 11 is a cable case. With this configuration, the radiation detector is easy to install and is most suitable for detecting directional radiation.

Embodiment 5 FIG. 7 shows the flow path forming means 42 in the fourth embodiment so that the plurality of scintillation fibers 1 are surely kept within the usable temperature range.
The outer circumference of is shaped so as to make surface contact with the scintillation fiber 1. Therefore, in this embodiment, the flow path forming means 42 may have any shape as long as it can flow the heat retaining fluid 9 and is in surface contact with the plurality of scintillation fibers 1.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a radiation detector of the present invention.

FIG. 2 is a detailed cross-sectional view showing an attachment portion of the flow path forming means of the present invention to a scintillation fiber.

FIG. 3 is a sectional view showing a section of a scintillation fiber portion of the present invention.

FIG. 4 is a sectional view showing a section of a scintillation fiber portion according to another embodiment of the present invention.

FIG. 5 is a sectional view showing a section of a scintillation fiber portion according to a third embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a cross section of a scintillation fiber portion according to a fourth embodiment of the present invention.

FIG. 7 is a cross sectional view showing a cross section of a scintillation fiber portion according to a fifth embodiment of the present invention.

FIG. 8 is a schematic configuration diagram showing a conventional radiation detector.

FIG. 9 is a cross-sectional view showing a cross section of a conventional scintillation fiber portion.

[Explanation of symbols]

1 scintillation fiber, 2 core material, 3 clad material, 4 flow passage forming means, 6 heat exchanger, 7 fluid transfer means, 9 heat retaining fluid, 10 heat insulating material

Claims (6)

[Claims] 1. A scintillation fiber for generating an optical pulse by incident radiation, and light-receiving elements provided at both ends of the scintillation fiber for detecting the optical pulse, and determining an incident position of the radiation or a radiation dose rate. In the radiation detector, a flow path forming means made of a material that easily transmits radiation to form a fluid passage around the scintillation fiber, and the scintillation fiber guided to the flow path to keep the scintillation fiber within a predetermined usable temperature range. A radiation detector comprising a heat retaining fluid. 2. The heat insulating fluid is a fluid having a refractive index lower than that of light of scintillation fibers such as water or air circulating in a closed circuit via a heat exchanger. The radiation detector described. 3. A scintillation fiber for generating an optical pulse by incident radiation, and light-receiving elements provided at both ends of the scintillation fiber for detecting the optical pulse, and determining an incident position of the radiation or a radiation dose rate. A radiation detector comprising a heat insulating material surrounding the scintillation fiber. 4. A scintillation fiber for generating an optical pulse by incident radiation and light-receiving elements provided at both ends of the scintillation fiber for detecting the optical pulse, and determining an incident position of the radiation or a radiation dose rate. In the radiation detector, a plurality of the scintillation fibers are arranged in parallel, a flow path forming means is provided so that the outer periphery of the scintillation fibers is in contact with the scintillation fibers, and a scintillation fiber guided to the flow path. A radiation detector, comprising: a heat-retaining fluid that keeps the temperature within a predetermined usable temperature range; and a heat insulating material that surrounds the flow path forming means and the plurality of scintillation fibers. 5. The radiation detector according to claim 4, wherein the flow path forming means is formed of a material such as copper that does not easily transmit radiation. 6. The radiation detector according to claim 4, wherein the outer circumference of the flow path forming means is formed so as to make surface contact with the outer circumferences of the plurality of scintillation fibers.