JP7519964B2 - Self-powered radiation detector - Google Patents

Description

The present invention relates to a self-powered radiation detector that monitors dose rate.

As an example of a self-powered radiation detector, Patent Document 1 describes a gamma-ray flux-sensitive self-powered radiation detector that includes a conductive emitter in the center, insulating means disposed around the emitter, and a substantially tubular conductive collector exterior disposed around the insulating means, with the emitter being a tubular member with the insulating means disposed inside.

Japanese Patent Application Publication No. 55-499

A self-powered radiation detector is a radiation detector that does not require a power supply such as applying a voltage, but measures the current value that flows when the number of electrons in the material that makes up the detector changes due to exposure to radiation.

Depending on the type of radiation they measure, they are called self-powered gamma ray detectors (SPGDs) or self-powered neutron detectors (SPNDs). Here, we will mainly use SPGDs as an example, but the basic concept and structure are the same for SPNDs.

When exposed to gamma rays, SPGDs eject electrons from the emitter, which is part of the detector, reducing the number of electrons in the emitter. To compensate for this, electrons are supplied to the emitter via a conductor connected to the emitter. An electric current flows as the electrons move through this conductor.

SPGDs do not have the electron amplification mechanism found in ionization chambers, etc. For this reason, they need to measure minute currents. In general, the current value is proportional to the dose rate, so their range of application has been limited to high dose rate environments. To apply them to low dose rate environments, it is necessary to either increase the number of electrons emitted from the emitter or reduce the number of electrons absorbed by the emitter. Patent Document 1 shows a structure that reduces the number of electrons absorbed by the emitter.

Patent Document 1 discloses a structure that suppresses the decrease in current value relative to the frequency of gamma ray interactions by using an SPGD consisting of a tubular emitter, surrounding insulating material, and a collector exterior, which reduces the probability that electrons ejected by the emitter will be absorbed by the emitter again.

If the SPGD could be used in a wide range of dose rate environments, the range of applications as a dose rate monitoring device would be expanded, since no voltage application is required and few auxiliary devices are required. When applying the SPGD to low dose rates, high sensitivity is required.

The principle by which current is generated by the self-output of an SPGD is the exchange of electrons at the emitter. When electrons are released from the emitter, a positive current flows, and when electrons are absorbed by the emitter, a negative current flows.

One of the factors that reduces the sensitivity of SPGD is the self-absorption of electrons in the emitter. Electrons generated in the emitter by gamma rays are absorbed in the emitter due to their short range, and do not contribute to changes in the emitter's charge. For this reason, there were many events in which no current was generated despite the interaction between gamma rays and the emitter.

Therefore, to improve sensitivity, it is necessary to either increase the number of electrons emitted from the emitter or decrease the number of electrons absorbed by the emitter.

If the volume or surface area of the emitter is reduced to suppress electron absorption in the emitter, the distance that the gamma rays travel through the emitter is also shortened, reducing the probability of interaction, which may result in a decrease in the number of electrons generated in the emitter and an increase in the number of electrons generated in the insulator, which causes negative current.

The present invention provides a self-powered radiation detector that is more sensitive than conventional detectors and has a wider range of applications.

The present invention includes a number of means for solving the above problems, and one example thereof is characterized in that it comprises a metallic emitter and a metallic collector, the emitter being formed of at least two layers, the collector being formed of at least two layers so as to sandwich the emitter by having an internal collector layer between two or more of the emitters , the collector and the emitter being electrically insulated by the presence of an insulating material between them , the emitter, the internal collector layer, and the insulating material being shaped as an integral plate, and the plate being rolled up to form a spiral shape .

The present invention provides a self-powered radiation detector that is more sensitive and has a wider range of application than conventional detectors, and can expand the range of applications to include lower dose rates. Problems, configurations, and effects other than those described above will become clear from the explanation of the following examples.

1 is a diagram showing a self-powered gamma ray detector according to a first embodiment of the present invention; FIG. 11 is a diagram showing a self-powered gamma ray detector according to a second embodiment of the present invention. FIG. 11 is a diagram showing a self-powered gamma ray detector according to a third embodiment of the present invention. FIG. 11 is a diagram showing a self-powered gamma ray detector according to a fourth embodiment of the present invention. FIG. 11 is a diagram showing a self-powered gamma ray detector according to a fifth embodiment of the present invention. FIG. 13 is a diagram showing a self-powered gamma ray detector according to a sixth embodiment of the present invention.

Below, an embodiment of the self-powered radiation detector of the present invention will be described with reference to the drawings. Note that in the drawings used in this specification, identical or corresponding components are given the same or similar reference numerals, and repeated explanations of these components may be omitted.

Example 1
A self-powered radiation detector according to a first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a diagram showing the basic concept of a self-powered gamma ray detector (SPGD) according to the first embodiment.

As shown in FIG. 1, the self-powered radiation detector 1 includes an emitter 11 made of lead (Pb) inside the detector, an insulating material 12 made of Al ₂ O ₃ that covers the emitter 11 except for a connecting conductor portion 14, a collector 13 made of stainless steel on the outside of the insulating material 12, and an internal collector 101 made of Al at the radial center of the detector.

The emitter 11 has a multi-layer structure of at least two layers and is dedicated to detecting either neutrons or gamma rays (for gamma rays in this embodiment), and is preferably made of a high-density metal (Pb, Bi, etc.). This emitter 11 is electrically connected to the connection conductor 14. The connection conductor 14 is electrically connected to the core 15 of the MI cable 16, and is further electrically connected to the measurement device 18 beyond.

As described above, in the self-powered radiation detector 1 of this embodiment, in addition to the collector 13 on the outermost circumference, an inner collector 101 is provided at the radial center of the detector, and is formed of at least two layers sandwiching the emitter 11. The inner collector 101 and the outer collector 13 do not need to be made of the same material, but for example, a light metal with low density (such as Al) is used.

The collector 13 is connected to earth or ground, and is also electrically connected to the internal collector 101. In contrast, the collector 13 and the internal collector 101 are not in contact with the emitter 11 and are electrically insulated.

The insulating material 12 is an insulating material that insulates the emitter 11 from the collector 13, or between the emitter 11 and the internal collector 101. This insulating material 12 is also arranged between the emitters 11.

The measuring device 18 measures the value of the current flowing and calculates the gamma ray intensity and neutron intensity in the space in which the collector 13 and other components are placed.

When the self-powered radiation detector 1 is irradiated with gamma rays, electrons are ejected from the emitter 11. The ejected electrons are absorbed by the insulator 12, collector 13, or internal collector 101. At this time, electrons are lost from the emitter 11, so to compensate for this, electrons move from the measuring device 18 located further ahead of the core wire 15, causing a current to flow.

In addition, when gamma rays are irradiated and electrons emitted from the collector 13, the insulating material 12, or the internal collector 101 are absorbed by the emitter 11, the charge increases, causing a current to flow in the reverse direction through the core wire 15.

When electrons generated in emitter 11 are absorbed by emitter 11, there is no increase or decrease in charge in emitter 11, so no current flows. This is also the case when electrons generated in emitter 11 pass through insulating material 12 and are absorbed again by emitter 11.

The internal collector 101 suppresses the occurrence of an event called self-absorption, in which electrons generated in the emitter 11 pass through the insulating layer and are absorbed again by the emitter 11. Because electrons are easily absorbed by metals, the internal collector 101 is made of a metal, Al in this example.

If the internal collector 101 is thick, gamma ray interaction will occur in the internal collector 101 more than in the emitter 11, which will cause a reverse current to flow, so it is desirable to determine the material and thickness of the internal collector 101 so that the interaction probability is lower than that in the emitter 11.

Next, we will explain the effects of this embodiment.

The self-powered radiation detector 1 of the first embodiment of the present invention described above includes a metallic emitter 11 and a metallic collector 13. The collector is formed of at least two layers sandwiching the emitter 11, and the collector 13 and the emitter 11 are electrically insulated.

This makes it possible to suppress the reduction in the volume of the emitter 11, which affects the probability of interaction with gamma rays, while increasing the proportion of electrons ejected from the emitter 11 that are absorbed by the two or more layers of collector 13 and reducing the proportion that are absorbed again by the emitter 11, resulting in a highly sensitive self-powered gamma ray detector. Therefore, the range of situations in which the SPGD can be applied can be expanded to the low dose rate side.

In addition, the presence of insulating material 12 between the emitter 11 and the internal collector 101 minimizes the possibility of the emitter 11 and the internal collector 101 becoming electrically connected, making it possible to more reliably achieve high-sensitivity detection.

Furthermore, the internal collector 101 and the collector 13 are electrically connected, and the collector 13 is connected to earth or ground, thereby preventing charge accumulation in the collector.

Example 2
Second Embodiment A self-powered radiation detector according to a second embodiment of the present invention will be described with reference to Fig. 2. Fig. 2 is a diagram showing the basic concept of a self-powered gamma ray detector (SPGD) according to the second embodiment.

As shown in FIG. 2, the self-powered radiation detector 1A of this embodiment is provided with a multi-layer emitter 11, and by forming the emitter 11 thin, the probability of self-absorption in the emitter 11 is further reduced.

Here, as an example, the emitter 11 is set to 0.2 mm or less. There is an optimal value for this thickness depending on the expected energy of the gamma rays, so 0.2 mm is not necessarily optimal. Since gamma rays have penetrating power, the probability of interaction with an emitter 11 that is 0.2 mm or less is not high. For this reason, the probability of electrons being generated by gamma rays is also reduced.

Therefore, a multi-layer emitter 11 is provided as shown in Figure 2 so that the gamma rays cross the thin emitter 11 multiple times while passing through the SPGD.

The emitter 11 is made of Pb, the insulating material 12 is made of Al ₂ O ₃ , the collector 13 is made of stainless steel, and the inner collector 101A is made of Al. The materials also make it highly likely that the emitter 11 will interact with gamma rays.

In this embodiment, the radial center of the self-powered radiation detector 1A is the emitter 11, and an internal collector 101A exists between the emitters 11. In addition, all of the emitters 11 are connected to the connection conductor portion 14A.

Here, an insulating material 12 is placed between the emitter 11 and the internal collector 101A, but if there is no electrical connection between the emitter 11 and the internal collector 101A or between the emitter 11 and the collector 13, the insulating material 12 may not be necessary.

The rest of the configuration and operation are substantially the same as those of the self-powered radiation detector 1 of the first embodiment described above, and details are omitted.

As in the self-powered radiation detector 1A of the second embodiment of the present invention, by providing an internal collector 101A as part of the collector 13 between two or more emitters 11, it is possible to improve the probability of interaction between gamma rays and the emitters 11 while reducing the rate of self-absorption of electrons in the emitters 11, thereby providing a highly sensitive detector.
Example 3
A self-powered radiation detector according to a third embodiment of the present invention will be described with reference to Fig. 3. Fig. 3 is a diagram showing the basic concept of a self-powered gamma ray detector (SPGD) according to the third embodiment.

The self-powered radiation detector 1B of this embodiment shown in Figure 3 has an emitter 11B spirally shaped so that when a straight line L perpendicular to the surface of the emitter 11B is drawn, the straight line L intersects the emitter 11B three or more times. In addition, the emitter 11B, the internal collector 101B, and the insulating material 12B are shaped as an integrated plate, and the spiral shape is constructed by rolling up this plate.

When the emitter 11 and the internal collector 101A are multi-layered as in the self-powered radiation detector 1A of the second embodiment described above, it becomes difficult to install the connection conductor 14A, which may limit the thickness of the emitter. As a structure to avoid such problems, the emitter 11B and the internal collector 101B can be made into a spiral shape as shown in FIG. 3.

Since the connection conductor portion 14B only needs to be connected to the emitter 11B at at least one point, there is no need to construct complex connection conductor portions 14, 14A, and restrictions on making the emitter 11B thinner are relaxed.

As an example of this structure, the emitter 11B and the inner collector 101B are formed as a single layer with the insulating material 12B sandwiched between them, and then rolled up.

In FIG. 3, the innermost layer is the insulating material 12B, the outer layer is the internal collector 101B, the outer layer is the insulating material 12B, and the outer layer is the emitter 11B, which is wound three times, but there is no limit to the number of turns.

If there is no electrical contact between the emitter 11B and the internal collector 101B, the order of the layers is arbitrary, and the order of the layers does not necessarily have to be the order shown in FIG. 3. For example, the internal collector 101B and the emitter 11B may be reversed, and the order from the inside can be emitter 11B, insulating material 12B, internal collector 101B, insulating material 12B.

What is important is that the emitter 11B and the internal collector 101B are not electrically connected, and for this reason an insulating material 12B is provided between the emitter 11B and the internal collector 101B.

In FIG. 3, insulating material 12B1 is also provided on the inner surface side of collector 13, which constitutes the outermost layer. This is to prevent electrical contact between emitter 11B of the outermost layer of the spiral and collector 13. If electrical connection between collector 13 and emitter 11B is avoided by a different method, there is no need to provide insulating material 12B1 on the inner surface of collector 13.

In FIG. 3, the radial center of the self-powered radiation detector 1B is hollow, but from the viewpoint of sensitivity, it is preferable to form a spiral in this region as well.

The rest of the configuration and operation are substantially the same as those of the self-powered radiation detector 1 of the first embodiment described above, and details are omitted.

The self-powered radiation detector 1B of the third embodiment of the present invention also provides substantially the same effects as the self-powered radiation detector 1 of the second embodiment described above.

In addition, emitter 11B is spiral-shaped so that when a straight line L perpendicular to the surface of emitter 11B is drawn, the straight line intersects emitter 11B three or more times, thereby improving the probability of interaction between gamma rays and emitter 11B and achieving even higher sensitivity.

Furthermore, the emitter 11B, the internal collector 101B, and the insulating material 12B are shaped as a single plate, and the plate is rolled up to form a spiral shape, so that the electrical connection between the emitter 11B and the connecting conductor portion 14B can be made from a single point, which avoids the difficulty of wiring and provides a highly sensitive self-powered gamma ray detector that improves the probability of interaction between the gamma rays and the emitter 11B while reducing the rate of self-absorption of electrons in the emitter 11B.

Example 4
A self-powered radiation detector according to a fourth embodiment of the present invention will be described with reference to Fig. 4. Fig. 4 is a diagram showing the basic concept of a self-powered gamma ray detector (SPGD) according to the fourth embodiment.

The self-powered radiation detector 1C of this embodiment shown in Figure 4 has a structure in which a metallic core rod emitter 201 that functions as an emitter is located at the center inside the spiral structure.

In FIG. 4, the core rod emitter 201 is made of Pb. The core rod emitter 201 and the emitter 11C are electrically connected, and are connected to the measuring device 18 by the connection conductor portion 14C.

In FIG. 4, emitter 11C and core rod emitter 201 are connected by metal wire 17, but the emitter 11C may be electrically connected by wrapping the inside of the spiral layer structure around core rod emitter 201, or the core rod emitter 201 may be split in half and the ends of the spiral may be sandwiched between the emitter 11C and core rod emitter 201 to electrically connect the emitter 11C and core rod emitter 201 as the inside or outside of the layer. In this case, the core rod emitter 201 is insulated from the internal collector 101C and collector 13, just like emitter 11C.

The emitter 11C and the core rod emitter 201 do not need to be made of the same material, but if measurement accuracy is important, the same Pb is preferably used, and if ease of production is important, different materials are preferably used, for example Pb for the emitter 11C and SUS for the core rod emitter 201.

The rest of the configuration and operation are substantially the same as those of the self-powered radiation detector 1B of the third embodiment described above, and details are omitted.

The self-powered radiation detector 1C of the fourth embodiment of the present invention also provides substantially the same effects as the self-powered radiation detector 1B of the third embodiment described above.

In addition to the spiral emitter 11C, a core rod emitter 201 is provided at the center of the self-powered radiation detector 1C. The core rod emitter 201 and emitter 11C are electrically connected, so that the core rod emitter 201 can be connected to the core wire 15 via the connection conductor 14C as shown in FIG. 2. This eliminates the need to directly connect the emitter 11B formed of layers to the connection conductor 14B as in Example 3, making manufacturing easier.

Example 5
A self-powered radiation detector according to a fifth embodiment of the present invention will be described with reference to Fig. 5. Fig. 5 is a diagram showing the basic concept of a self-powered gamma ray detector (SPGD) according to the fifth embodiment.

The self-powered radiation detector 1D of this embodiment shown in Figure 5 has a structure in which a collector is provided on the inner core rod of the spiral structure instead of the core rod emitter 201 as in Example 4.

As shown in FIG. 5, an aluminum core rod collector 202 is located at the center of the self-powered radiation detector 1D. The core rod collector 202 and the internal collector 101 are electrically connected.

In FIG. 5, the internal collector 101D and the core rod collector 202 are electrically connected by a metal wire 17, but the internal collector 101D may be electrically connected by wrapping the internal collector 101D around the core rod collector 202 as the inner side of the spiral layer structure, or the core rod collector 202 may be split in half and the internal collector 101D and the core rod collector 202 may be electrically connected as the inner or outer side of the layer by sandwiching the ends of the spiral.

The collector 13 is electrically connected to the inner collector 101D and the core rod collector 202D by a collector connection wire 301. The core rod collector 202 and the like are insulated from the emitter 11D.

The rest of the configuration and operation are substantially the same as those of the self-powered radiation detector 1B of the third embodiment or the self-powered radiation detector 1C of the fourth embodiment, and details are omitted.

The self-powered radiation detector 1D of the fifth embodiment of the present invention also provides substantially the same effects as the self-powered radiation detectors 1B and 1C of the third and fourth embodiments described above.

In addition to the spiral-shaped internal collector 101D, a core rod collector 202 is provided at the center of the self-powered radiation detector 1D, and the core rod collector 202 and the internal collector 101D are electrically connected, thereby preventing electric charge from accumulating in the internal collector 101D.

Example 6
A self-powered radiation detector according to a sixth embodiment of the present invention will be described with reference to Fig. 6. Fig. 6 is a diagram showing the basic concept of a self-powered gamma ray detector (SPGD) according to the sixth embodiment.

The self-powered radiation detector 1E of this embodiment shown in Figure 6 is configured such that, when the inside of the spiral layer is a core rod emitter 201 as in the self-powered radiation detector 1C shown in Figure 4, the inner collector 101E and the collector 13 are electrically connected by a collector connection wire 301 as in the self-powered radiation detector 1D shown in Figure 5.

When the outermost layer of the spiral structure is the internal collector 101E, it is sufficient to make contact with the collector 13, in which case the collector connection wire 301 is not necessary.

The rest of the configuration and operation are substantially the same as those of the self-powered radiation detector 1C of the fourth embodiment or the self-powered radiation detector 1D of the fifth embodiment, and details are omitted.

The self-powered radiation detector 1E of the sixth embodiment of the present invention also has substantially the same effect as the self-powered radiation detectors 1C and 1D of the fourth and fifth embodiments described above, that is, it is possible to further reduce the probability that the electrons emitted from the emitter 11 are again self-absorbed by the emitter 11, and it is also possible to further prevent the accumulation of electric charge in the internal collector 101.

＜Other＞
The present invention is not limited to the above-mentioned embodiment, but includes various modified examples. The above-mentioned embodiment has been described in detail to explain the present invention in an easily understandable manner, and the present invention is not necessarily limited to the embodiment having all of the described configurations.

It is also possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

For example, when the self-powered radiation detector is cylindrical as shown in Figure 1, the direction in which the emitters and collectors are stacked does not need to be radial to the central axis, and multiple collectors and emitters can be stacked in the vertical direction of the cylinder.

1, 1A, 1B, 1C, 1D, 1E: Self-powered radiation detector 11, 11B, 11C, 11D, 11E: Emitter 12, 12B, 12B1, 12C, 12C1, 12D, 12D1, 12E, 12E1: Insulating material 13: Collector 14, 14A, 14B, 14C, 14D, 14E: Connection conductor 15: Core wire 16: MI cable 17: Metal wire 18: Measuring device 101, 101A, 101B, 101C, 101D, 101E: Inner collector 201: Core rod emitter 202: Core rod collector 301: Collector connection wire

Claims (6)

A metallic emitter;
A collector made of metal,
The emitter is formed of at least two layers,
The collector is formed of at least two layers having two or more of the emitters and an internal collector layer between the emitters, so as to sandwich the emitters therebetween,
The collector and the emitter are electrically insulated from each other by the presence of an insulating material between them ,
11. A self-powered radiation detector, comprising : said emitter, said inner collector layer, and said insulating material formed as an integral plate, said plate being rolled to form a spiral shape . A metallic emitter;
A collector made of metal,
the emitter is spirally shaped such that, when a straight line perpendicular to a surface of the emitter is drawn, the straight line intersects the emitter three or more times ;
the collector is formed of at least two layers so as to sandwich the emitters by having two or more of the emitters and an internal collector layer between the emitters,
The collector and the emitter are electrically insulated from each other by the presence of an insulating material between them,
11. A self-powered radiation detector, comprising : said emitter, said inner collector layer, and said insulating material formed as an integral plate, said plate being rolled to form a spiral shape . 3. The self-powered radiation detector according to claim 1 ,
In addition to the spiral emitter, a core rod emitter is provided at the center of the self-powered radiation detector,
A self-powered radiation detector, characterized in that the core rod emitter and the emitter are electrically connected to each other. 3. The self-powered radiation detector according to claim 1 ,
in addition to the spiral inner collector layer, a core rod collector is provided at the center of the self-powered radiation detector;
A self-powered radiation detector, characterized in that the core rod collector and the inner collector layer are electrically connected to each other. 3. The self-powered radiation detector according to claim 1 ,
a collector layer formed on an outermost periphery of the collector and electrically connected to the inner collector layer, the collector being electrically connected to the inner collector layer and an outermost periphery of the collector. 3. The self-powered radiation detector according to claim 1 ,
A self-powered radiation detector, wherein the collector is connected to earth or ground.

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