JP7416298B2 - Radiation detection device - Google Patents

Description

The present invention relates to a radiation detection device.

Conventionally, detection devices for radiation such as alpha rays have a radiation detection element inside a case, and the radiation emitted from a measurement sample is passed through a transparent protective film provided in the case to the radiation detection element. (For example, see Patent Document 1). Furthermore, in this detection device, the operation is checked by irradiating the radiation detection element with light from the light source within the case.
Patent Document 1 Patent No. 4258145

However, when radiation enters the radiation detection element through the protective film, the energy of the radiation is attenuated and detection accuracy is reduced. On the other hand, if the radiation detection element is placed outside the case, the radiation detection element cannot be illuminated with light for checking its operation.

In order to solve the above problems, a radiation detection device is provided in a first aspect of the present invention. The radiation detection device may include a case portion that seals the inside. The radiation detection device may include a semiconductor radiation detection element in which at least a portion of the surface is exposed outside the case portion. The radiation detection device may include a light source that emits a light pulse for operation check. The case portion may have a protrusion that protrudes toward the measurement sample side from the surface of the radiation detection element. The case portion may include a light-transmitting portion that is provided on the protruding portion and transmits a light pulse from the light source toward the radiation detection element.

The light-transmitting portion may transmit the light pulse toward a region of the surface of the radiation detection element exposed to the outside of the case portion.

The protrusion may be provided on the side of at least a part of the side peripheral surface of the radiation detection element. The light-transmitting portion may be provided in a portion of the protruding portion on the side of the radiation detection element.

The protrusion may be provided in a ring shape around the radiation detection element. The light-transmitting portion may be provided over the entire inner circumference of the protrusion.

The transparent part may be a cylindrical member. The light source may be arranged within the protrusion toward the outer circumferential surface of the light-transmitting section.

The light-transmitting portion may be an annular light guide that guides the light pulses incident from the incident surface and outputs the light pulses from the output surface facing the radiation detection element. The light source may be placed toward the entrance plane.

The output surface may be provided on the inner circumference of the protrusion. The entrance surface may be provided at the proximal end of the protrusion so as to face the side opposite to the measurement sample.

The case portion may include a support plate that supports the radiation detection element from the back side. The case portion may include a transparent portion and an annular sealing member interposed between the support plate. The light-transmitting part may have a bent shape so that the inner diameter becomes smaller on the measurement sample side. The light-transmitting portion may be arranged to face the side peripheral surface of the support plate and the outer peripheral portion of the surface of the support plate.

The light-transmitting portion may have a groove portion into which a packing serving as a sealing member is removably fitted.

The radiation detection device may further include an amplifier circuit that is disposed inside the case and amplifies the electric pulse output from the radiation detection element.

The radiation detection element may detect alpha rays.

Note that the above summary of the invention does not list all the necessary features of the invention. Furthermore, subcombinations of these features may also constitute inventions.

1 shows a radiation detection device 1 according to this embodiment. The appearance of the transparent part 143 is shown. A radiation detection device 1A according to a modification is shown. The appearance of the light guide 144 is shown.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Furthermore, not all combinations of features described in the embodiments are essential to the solution of the invention.

[1. Radiation detection device 1]
FIG. 1 shows a radiation detection device 1 according to this embodiment.

The radiation detection device 1 may be a device that measures and monitors radiation (alpha rays as an example in this embodiment) emitted from a measurement sample, and for example, detects radionuclides contained in exhaust gas in a facility such as a nuclear power plant. It may be used for detection. The measurement sample may be a unit volume of air in the environment, or may be dust collected on the filter paper by passing the unit volume of air through the filter paper. The radiation detection device 1 includes a radiation detection element 10, an amplifier circuit 11, a control circuit 12, a connector 13, a case portion 14, and a light source 15.

[1-1. Radiation detection element 10]
The radiation detection element 10 detects radiation (alpha rays as an example in this embodiment) incident on the surface (the upper surface in the figure).

At least a portion of the surface of the radiation detection element 10 (in this embodiment, the entire surface, as an example) is exposed to the outside of the case portion 14 . The α rays from the measurement sample may enter the externally exposed region only through the air layer. A protective film (for example, a PET film) for preventing contamination of the surface of the radiation detection element 10 may not be provided between the radiation detection element 10 and the measurement sample. The radiation detection element 10 may face the measurement sample in an area exposed to the outside, and may receive α rays emitted from the measurement sample.

The radiation detection element 10 is a semiconductor type detection element, and may be formed into a plate shape. In addition, although the radiation detection element 10 is disk-shaped as an example in this embodiment, other shapes may be sufficient. The radiation detection element 10 has a pn junction or a heterojunction formed on one side of a high-resistivity single-crystal silicon wafer, and a reverse bias is applied to this junction to form depletion layers on both sides of the junction. It's okay. The region where the depletion layer is formed may be a radiation sensitive region and may be exposed to the outside of the case portion 14. Note that when the radiation detection element 10 is a pn junction type, the region where the pn junction is formed may be this sensitive region, and when the radiation detection element 10 is a heterojunction type made of amorphous silicon. In this case, the area of the electrode formed on the amorphous silicon may be substantially the sensitive area.

The sensitive area may be formed in the center of the radiation detection element 10 in a plan view, and may have, for example, a circular shape (for example, a circular shape with a diameter of 50 mm). The radiation detection element 10 may have a light-receiving region for the light pulse emitted from the light source 15 in the sensitive region for checking the operation of the radiation detection device 1 . In other words, the radiation detection element 10 does not need to have a light-receiving region for light pulses for operation check, separate from the sensitive region.

Here, when the α ray moves in a substance (in the case of the radiation detection element 10, in silicon), high-density electron-hole pairs are generated in the movement path due to the interaction between the substance and the α ray. When the region where these electron-hole pairs are generated is a high electric field region such as a depletion layer, the electron-hole pairs are separated into electrons and holes by the high electric field, and the holes are taken out to the negative electrode side. As a result, electrons are extracted to the positive electrode side. Since the extracted holes and electrons are charged particles, by measuring the amount of charge extracted from the electrode, the number of holes or electrons extracted and, in turn, the energy of the α rays lost in the substance can be calculated. The thickness of the depletion layer of the radiation detection element 10 is designed to be larger (thicker) than the range of the α-rays to be measured, so the amount of charge taken out from the electrode is equal to the energy of the α-rays incident on the depletion layer. corresponds to The charge extracted from the electrode may be supplied to the amplifier circuit 11 as an electric pulse.

[1-2. Amplifier circuit 11]
The amplifier circuit 11 is arranged inside the case part 14 and amplifies the electric pulse output from the radiation detection element 10. The amplifier circuit 11 may generate a voltage pulse having a peak value proportional to the amount of charge of the input electric pulse. Note that since the electric pulse inputted to the amplifier circuit 11 is a minute current pulse, the amplifier circuit 11 may be configured with a high impedance circuit from the viewpoint of improving the accuracy of amplification. Amplifier circuit 11 may supply voltage pulses to control circuit 12 .

[1-3. Control circuit 12]
The control circuit 12 controls each part of the radiation detection device 1. The control circuit 12 may perform various calculations based on the voltage pulses from the amplifier circuit 11. For example, the control circuit 12 may calculate the energy of α-rays based on the voltage pulse from the amplifier circuit 11. The control circuit 12 may generate an energy spectrum by using the number of pulses falling within a reference energy width within a reference time as a histogram. The control circuit 12 may calculate the radionuclides contained in the measurement sample and their concentration from the energy spectrum. The control circuit 12 may output the calculation result to the outside of the radiation detection device 1 via the connector 13.

[1-4. Connector 13]
The connector 13 is an interface for connecting the radiation detection device 1 to external equipment. The connector 13 may be provided outside the case portion 14.

[1-5. Case part 14]
The case portion 14 seals the inside. The case portion 14 may house at least the amplifier circuit 11 therein. As a result, even if the amplifier circuit 11 is constituted by a high impedance circuit as described above, a decrease in insulation performance and a change in characteristics due to fluctuations in humidity in the atmosphere can be prevented. In this embodiment, as an example, the case portion 14 may further house the control circuit 12 and the light source 15 therein.

The case portion 14 includes a case portion main body 140, a support plate 141, a protruding portion 142, and a light-transmitting portion 143. Among these, the case body 140, the support plate 141, and the protrusion 142 may be made of brass or aluminum. In this case, the case portion 14 may have the function of a shield box that prevents noise from entering from the outside.

[1-5-1. Case body 140]
The case main body 140 is a cylindrical member that has an opening 1400 on the side of the measurement sample (upper side in the figure) and a bottom 1401 on the side opposite to the measurement sample (lower side in the figure). A housing space for the amplifier circuit 11 and the like is formed. The bottom part 1401 may be provided with a connector 13.

[1-5-2. Support plate 141]
The support plate 141 supports the radiation detection element 10 from the back side (lower side in the figure). The support plate 141 may be disposed at the center of the opening 1400 of the case main body 140 and supported by the case main body 140 via the protrusion 142 and the transparent part 143. Wiring that electrically connects between the radiation detection element 10 and the amplifier circuit 11 may be provided to pass through the support plate 141 .

[1-5-3. Projection 142]
The protrusion 142 is provided so as to protrude from the surface of the radiation detection element 10 supported by the support plate 141 toward the measurement sample side (upper side in the figure). The protrusion 142 may be provided in an annular shape around the radiation detection element 10 . For example, the protrusion 142 protrudes from the edge of the case main body 140 on the measurement sample side, that is, the peripheral edge of the opening 1400, toward the measurement sample, and has a bent shape such that the inner diameter becomes smaller at the end on the measurement sample side. may have.

[1-5-4. Transparent part 143]
The light transmitting portion 143 is provided on the protruding portion 142 and transmits the light pulse from the light source 15 toward the radiation detection element 10 (see the white arrow in the figure). The light transmitting section 143 may transmit the light pulse toward a region of the surface of the radiation detection element 10 that is exposed to the outside of the case section 14 .

The light-transmitting portion 143 may be provided over the entire inner circumference of the protrusion 142 . The transparent part 143 may be a cylindrical member, and is in close contact with the inner peripheral edge of the tip of the protruding part 142 (the end opposite to the case main body 140) and the outer peripheral edge of the support plate 141. It may be provided as follows. In the present embodiment, as an example, the light-transmitting portion 143 is provided in close contact with the bottom surface of the inner peripheral edge of the tip portion of the protrusion 142, but may be in close contact with the inner peripheral surface of the inner peripheral edge. Further, in this embodiment, as an example, the light-transmitting portion 143 is provided in close contact with the surface of the support plate 141, but may be provided in close contact with the side peripheral surface of the support plate 141. The light-transmitting portion 143 may be in close contact with the protruding portion 142 and the support plate 141 via a sealant or adhesive.

The light-transmitting part 143 may be formed of a transparent material that transmits the light pulse, and in this embodiment, it is formed of transparent plastic such as PET or acrylic resin, but it may be formed of other materials such as glass. may be formed.

[1-6. Light source 15]
The light source 15 emits a light pulse for operation check. The light pulses emitted from the light source 15 may form electron-hole pairs when they enter the radiation detection element 10, similar to alpha rays. As a result, an electric pulse of charge corresponding to an electron-hole pair generated in the depletion layer of the radiation detection element 10 is output from the radiation detection element 10 to the amplifier circuit 11, and the operation of the radiation detection device 1 is checked. .

The light source 15 may be disposed within the protrusion 142 toward the outer circumferential surface of the cylindrical transparent portion 143 . Furthermore, the light source 15 may be arranged to be inclined toward the side opposite to the measurement sample (lower side in the figure) so that the surface of the radiation detection element 10 is irradiated with a light pulse.

The light source 15 may be a light emitter or a light emitter that emits light by itself, and may emit light in response to a pulsed input signal supplied from the control circuit 12. Although only one light source 15 is illustrated in FIG. 1, a plurality of light sources 15 may be arranged in line in the circumferential direction within the protrusion 142.

According to the radiation detection device 1 described above, at least a part of the surface of the semiconductor type radiation detection element 10 is exposed to the outside of the case part, so that the radiation detection element 10 is housed inside the case part 14 and is transparent. Unlike the case where the measurement sample is covered with a protective film or the like, it is possible to prevent the energy of radiation (in this embodiment, alpha rays as an example) from the measurement sample from being attenuated by the protective film. Therefore, by increasing the energy resolution, the accuracy of identifying the nuclide of the radiation source (in this embodiment, as an example, plutonium nuclide (Pu-239) which is an α-ray source, and uranium nuclide (U-238) which is another α-ray source) ) and americium nuclide (Am-241)).
Further, the case portion 14 is provided with a protrusion 142 that protrudes from the surface of the radiation detection element 10 toward the measurement sample side, and the protrusion 142 transmits the light pulse from the light source 15 toward the radiation detection element 10. Since the transparent portion 143 is provided, even if the radiation detection element 10 is provided outside the case portion 14, the operation of the radiation detection device 1 can be checked.

Furthermore, since the light-transmitting part 143 transmits the light pulse toward the area of the surface of the radiation detection element 10 that is exposed to the outside of the case part 14, the light-receiving area of the light pulse for operation check is transmitted to the radiation detection element 10. can be within the radiation sensitive area. Therefore, unlike the case where the sensitive area and the light-receiving area are separate areas, the accuracy of the operation check can be improved. Moreover, since there is no need to provide a light pulse receiving area separately from the sensitive area, the radiation detection element 10 and, by extension, the radiation detection apparatus 1 can be downsized.

Further, the protrusion 142 is provided in an annular shape around the radiation detection element 10, and the light-transmitting portion 143 is provided over the entire inner circumference of the protrusion 142, so that the light-transmitting portion 143 covers part of the inner circumference. Compared to the case where the radiation detection device 1 is provided only in the case portion, the case portion 14 can be easily sealed, and the radiation detection device 1 can be manufactured more easily.

Further, the light transmitting portion 143 is a cylindrical member, and the light source 15 is disposed within the protruding portion 142 toward the outer peripheral surface of the light transmitting portion 143. Therefore, the light pulse from the light source 15 is reliably transmitted to the radiation detection element 10. can be irradiated.

Further, since the amplifier circuit 11 that amplifies the electric pulse output from the radiation detection element 10 is arranged inside the case portion 14, the humidity around the amplifier circuit 11 can be maintained constant. Therefore, it is possible to prevent the electrical characteristics of the amplifier circuit 11 from changing due to humidity fluctuations, and improve the accuracy of radiation measurement.

[1-7. Appearance of transparent part 143]
FIG. 2 shows the appearance of the light-transmitting section 143. As shown in this figure, the light transmitting portion 143 may be formed in a cylindrical shape.

[2. Modified example]
FIG. 3 shows a radiation detection device 1A according to a modification.

The radiation detection device 1A includes a case portion 14A and a light source 15A.
The case portion 14A includes a light guide 144 and a packing 145.

The light guide 144 is an example of a transparent part, and is provided on the protruding part 142, and transmits the light pulse from the light source 15A toward the radiation detection element 10 (see the white arrow in the figure). The light guide 144 is formed in an annular shape and guides the light pulses incident from the entrance surface 1441 and outputs them from the exit surface 1442 facing the radiation detection element 10 . The output surface 1442 may be provided at the inner circumference of the protrusion 142, and the incidence surface 1441 may be provided at the proximal end (lower end in the figure) of the protrusion 142 to face the side opposite to the measurement sample. good. Light guide 144 may have at least one reflective surface therein. The light guide 144 may have a bent shape such that the inner diameter becomes smaller on the measurement sample side, and may have an output surface 1442 on the inner periphery of the end on the measurement sample side. The light guide 144 may be arranged to face the side peripheral surface of the support plate 141 and the outer peripheral portion of the surface of the support plate 141. For example, the light guide 144 may have a hole of the same type as the support plate 141, and the support plate 141 may be fitted therein.

The light guide 144 may have a groove 1440 into which the packing 145 is removably fitted. In this embodiment, as an example, the light guide 144 has a groove 1440 on the surface facing the surface of the support plate 141, but in addition/instead of this, the light guide 144 has a groove 1440 on the surface facing the side peripheral surface of the support plate 141. The groove portion 1440 may be provided on the protruding portion 142 or the surface facing the inner circumferential surface of the case body 140.

The light guide 144 may be formed of a transparent material that allows light pulses to pass through, and in this embodiment, as an example, it is formed of transparent plastic such as PET or acrylic resin, but it may be formed of other materials such as glass. may be done.

The packing 145 is an example of a sealing member and is formed in an annular shape. The packing 145 may be an O-ring, and may have a size of about 55 mmφ, for example. The packing 145 may be interposed between the support plate 141 and the light guide 144. When the light guide 144 is provided with a groove 1440, the packing 145 may be fitted into the groove 1440 to perform sealing.

The light source 15A is arranged toward the entrance surface 1441 of the light guide 144. In this embodiment, as an example, the light source 15A may be arranged inside the case main body 140. Although only one light source 15A is shown in FIG. 3, a plurality of light sources 15A may be arranged circumferentially inside the case main body 140.

According to the radiation detection device 1A described above, the annular light guide 144 serving as the light-transmitting portion guides the light pulses incident from the entrance surface 1441 and outputs them from the exit surface 1442 facing the radiation detection element 10. , the radiation detection element 10 can be reliably irradiated with the light pulse from the light source 15A.

Furthermore, since the output surface 1442 is provided on the inner circumference of the protrusion 142 and the incidence surface 1441 is provided on the proximal end of the protrusion 142 facing away from the measurement sample, the light source 15A is placed inside the protrusion 142. Since there is no need to provide the light source 15A, the degree of freedom in arranging the light source 15A can be increased.

Further, since the annular packing 145 is interposed between the light guide 144 and the support plate 141, the inside of the case portion 14 can be reliably sealed.

Further, since the light guide 144 is provided with a groove 1440 into which the packing 145 is removably fitted, the case portion 14 can be easily sealed.

[2-1. Appearance of light guide 144]
FIG. 4 shows the appearance of the light guide 144. As shown in this figure, the light guide 144 may be formed in an annular shape and bent such that the inner diameter becomes smaller on one side (upper side in the figure). The light guide 144 may have an exit surface 1442 on the inner peripheral portion of one side and an entrance surface 1441 on the other side.

[3. Other variations]
Note that in the above embodiment, the protrusion 142 has been described as being provided in an annular shape around the radiation detection element 10; You can. In this case, the light transmitting portion 143 (or the light guide 144) may be provided in a portion of the protruding portion 142 on the radiation detection element 10 side. Even in this case, the radiation detection element 10 can be reliably irradiated with a light pulse to check its operation. When the protrusion 142 is not provided in an annular shape, the support plate 141 is provided integrally with the case main body 140 in a portion of the opening 1400 of the case main body 140 where the protrusion 142 is not provided. Good too.

In addition, although the explanation has been made assuming that the light pulses emitted from the light source 15 enter the radiation detection element 10 through the transparent part 143 and the light guide 144, there is a collimator on the optical path from the light source 15 to the radiation detection element 10. Other optical members such as mirrors or mirrors may be further arranged.

Further, although the light sources 15 and 15A have been described as light emitters, they may be the ends of optical fibers that emit light supplied from the light emitters. In this case, the light emitter may be provided outside the case portions 14, 14A. Thereby, the interior of the case parts 14, 14A can be simplified and malfunctions and failures can be reduced. Further, compared to the case where a light emitting body is used as the light sources 15, 15A, the light sources 15, 15A can be made smaller, and the degree of freedom in arrangement can be increased. As an example, when the light source 15A in the modified example explained using FIG. may be provided.

Furthermore, although the groove 1440 into which the packing 145 is fitted has been described as being provided in the light guide 144, it may be provided in the support plate 141, the protrusion 142, or the surface of the case main body 140 that faces the light guide 144.

Furthermore, although the radiation detection device 1 has been described as being equipped with the amplifier circuit 11, the control circuit 12, and the connector 13, at least one of these may be included in an external device connected to the radiation detection device 1.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the range described in the above embodiments. It will be apparent to those skilled in the art that various changes or improvements can be made to the embodiments described above. It is clear from the claims that such modifications or improvements may be included within the technical scope of the present invention.

The execution order of each process such as an operation, a procedure, a step, and a stage in the apparatus, system, program, and method shown in the claims, specification, and drawings is specifically defined as "before" or "before". It should be noted that they can be implemented in any order unless the output of the previous process is used in the subsequent process. Even if the claims, specifications, and operational flows in the drawings are explained using "first," "next," etc. for convenience, it means that it is essential to carry out the operations in this order. It's not a thing.

1 radiation detection device, 10 radiation detection element, 11 amplifier circuit, 12 control circuit, 13 connector, 14 case part, 15 light source, 140 case part main body, 141 support plate, 142 protrusion part, 143 transparent part, 144 light guide, 145 Packing, 1400 Opening, 1401 Bottom, 1440 Groove, 1441 Incident surface, 1442 Output surface

Claims (8)

A case part that seals the inside,
a semiconductor-type radiation detection element whose surface is at least partially exposed to the outside of the case portion;
a light source that emits light pulses for operation checking;
a light-transmitting part that is provided closer to the measurement sample than the surface of the radiation detection element and transmits the light pulse from the light source toward the radiation detection element;
A radiation detection device comprising: The radiation detection device according to claim 1, wherein the light-transmitting section transmits the light pulse toward a region of the surface of the radiation detection element exposed to the outside of the case section. The transparent part is a cylindrical member,
The radiation detection device according to claim 1 or 2, wherein the light source is arranged toward an outer peripheral surface of the light-transmitting section. The light-transmitting part is an annular light guide that guides the light pulse incident from the incident surface and outputs it from the output surface facing the radiation detection element,
The radiation detection device according to claim 1 or 2, wherein the light source is arranged facing the incident surface. The case portion includes a support plate that supports the radiation detection element from the back side;
an annular sealing member interposed between the light-transmitting part and the support plate;
The light-transmitting part has a bent shape so that the inner diameter becomes smaller on the measurement sample side, and is arranged to face a side peripheral surface of the support plate and an outer peripheral part of the surface of the support plate. The radiation detection device according to item 4. The radiation detection device according to claim 5, wherein the light-transmitting portion has a groove portion into which a packing serving as the sealing member is removably fitted. The radiation detection device according to any one of claims 1 to 6, further comprising an amplifier circuit disposed inside the case portion and amplifying an electric pulse output from the radiation detection element. The radiation detection device according to any one of claims 1 to 7, wherein the radiation detection element detects alpha rays.