CN115755152A - Neutron detector and neutron detection method - Google Patents
Neutron detector and neutron detection method Download PDFInfo
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- CN115755152A CN115755152A CN202211225964.7A CN202211225964A CN115755152A CN 115755152 A CN115755152 A CN 115755152A CN 202211225964 A CN202211225964 A CN 202211225964A CN 115755152 A CN115755152 A CN 115755152A
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Abstract
The application relates to the technical field of neutron detection, and provides a neutron detector and a neutron detection method, wherein the neutron detector comprises a plurality of moderation units and a thermal neutron sensitive layer, and neutrons to be detected of a substance to be detected can be moderated by the moderation units to generate thermal neutrons; the thermal neutron sensitive layer is arranged on the outer side of the moderating units, thermal neutrons are captured by the thermal neutron sensitive layer to generate cascade gamma rays, the gamma rays in the gamma radiation field trigger a first number of moderating units to respond, and the gamma rays in the gamma radiation field and the cascade gamma rays trigger a second number of moderating units to respond together. The neutron detector and the neutron detection method can improve the neutron-gamma discrimination ratio.
Description
Technical Field
The application relates to the technical field of neutron detection, in particular to a neutron detector and a neutron detection method.
Background
Neutron gamma discrimination is a technology for rapidly and accurately realizing neutron detection in a gamma radiation field, and can be used for detecting radioactive substances and special nuclear fuel. The neutron gamma screening technology can detect the shielding transportation of special nuclear materials in a gamma radiation field, and avoids the interference of the gamma radiation field on a neutron detector, so that the problem to be solved urgently is solved by improving the neutron gamma screening ratio of the neutron detector.
Disclosure of Invention
In view of this, embodiments of the present application are expected to provide a neutron detector and a detection method, which can improve the neutron-gamma discrimination ratio.
In order to achieve the above purpose, the technical solution of the embodiment of the present application is implemented as follows:
an aspect of an embodiment of the present application discloses a neutron detector, including:
a plurality of moderating units, by which neutrons to be detected of a substance to be detected can be moderated to generate thermal neutrons;
the thermal neutron sensitive layer is arranged on the outer side of the slowing-down units, the thermal neutrons are captured by the thermal neutron sensitive layer to generate cascade gamma rays, gamma rays in a gamma radiation field trigger a first number of the slowing-down units to respond, and the gamma rays in the gamma radiation field and the cascade gamma rays trigger a second number of the slowing-down units to respond together.
In one embodiment, the neutron detector includes a plurality of photodetectors, and each of the moderating units is coupled to at least one of the photodetectors.
In one embodiment, the neutron detector includes a reflective layer, and the reflective layer is disposed on an outer peripheral surface of each of the moderating units.
In one embodiment, a plurality of the moderating units are arranged in a width direction of the neutron detector to form a moderating layer, and the plurality of the moderating layers are stacked in a thickness direction of the neutron detector.
In one embodiment, the thermal neutron sensitive layer is surrounded on the outer periphery of each moderating unit.
In one embodiment, the neutron detector includes a first protection layer, and the first protection layer is surrounded on the outer peripheral surface of the thermal neutron sensitive layer.
In one embodiment, one thermal neutron sensitive layer is laid between two of the plurality of moderating layers, or,
and one thermal neutron sensitive layer is paved on each two adjacent slowdown layers.
In one embodiment, the neutron detector includes a second protective layer, and the outer peripheral surface of each of the moderating units is provided with the second protective layer.
In an embodiment, the neutron detector includes a lead plate, and a layer of the lead plate is disposed between every two adjacent moderation layers.
In one embodiment, the number of the slowing-down layers is between 3 and 5.
In one embodiment, the thickness of the thermal neutron sensitive layer is 20 μm to 30 μm.
In another aspect, an embodiment of the present application discloses a neutron detection method, which is used for the neutron detector in any one of the above embodiments, and the detection method includes:
setting a first number of the slowing units responsive to gamma rays in the gamma radiation field to a threshold;
and determining that the substance to be tested has the neutrons to be tested under the condition that the total number of responses of the slowing-down units is larger than the threshold value.
In one embodiment, the threshold is between 2 and 4.
The embodiment of the application discloses a neutron detector and a neutron detection method, thermal neutrons are generated by slowing down neutrons emitted by a substance to be detected through a slowing unit, then the thermal neutrons are captured through a thermal neutron sensitive layer to generate cascade gamma rays, energy of the gamma rays in a gamma radiation field can be deposited in a plurality of slowing units to cause a response of the slowing units of a first number, the gamma rays and the cascade gamma rays in the gamma radiation field can deposit energy in the slowing units to cause a response of the slowing units of a second number, and therefore when the substance to be detected is detected, screening of the neutron gamma rays can be achieved through the response number of the slowing units; on the other hand, the interference influence of the gamma ray in the gamma radiation field on the neutron detector can be reduced, and the neutron-gamma discrimination ratio is improved.
Drawings
Fig. 1 is a schematic structural diagram of a neutron detector provided in an embodiment of the present application;
FIG. 2 is an enlarged view taken at A in FIG. 1;
FIG. 3 is an enlarged view at B in FIG. 2;
FIG. 4 is a schematic structural diagram of another neutron detector provided in an embodiment of the present application, in which a thermal neutron sensitive layer is surrounded on the outer periphery of each moderating unit;
FIG. 5 is a graph of the number of moderating layers versus the detection efficiency of neutrons to be detected;
FIG. 6 is a graph showing the relationship between the thickness of the thermal neutron sensitive layer and the detection efficiency of neutrons to be detected;
FIG. 7 is a schematic flow chart of a neutron detection method according to another embodiment of the present application;
FIG. 8 is a graph of the number of responses of the photodetector versus the number of signals.
Description of the reference numerals
A neutron detector 100; a slowing-down unit 1; a thermal neutron sensitive layer 2; a reflective layer 3; a first protective layer 4; a second protective layer 5.
Detailed Description
It should be noted that, in the present application, technical features in examples and embodiments may be combined with each other without conflict, and the detailed description in the specific embodiment should be understood as an explanation of the gist of the present application and should not be construed as an improper limitation to the present application.
The present application will be described in further detail with reference to the following drawings and specific embodiments. The descriptions of "first," "second," etc. in the embodiments of the present application are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly including at least one feature. In the description of the embodiments of the present application, "a plurality" means at least two, e.g., two, three, etc., unless explicitly specified otherwise.
In the related technology, when detecting whether a substance to be detected has neutrons to be detected, analysis and detection of a full energy peak and the like of the deposition energy of the substance to be detected are required, so that the steps are more, and the detection time is longer. Moreover, gamma rays in the gamma radiation field can directly deposit energy in the slowing unit to trigger response, so that misjudgment is caused, and inaccurate detection is caused.
In view of the above, in one aspect, the present embodiment provides a neutron detector, and referring to fig. 1 to 4, a neutron detector 100 includes a plurality of moderating units 1 and a thermal neutron sensitive layer 2. Neutrons to be measured of the substance to be measured can be moderated by the moderating unit 1 to generate thermal neutrons. The thermal neutron sensitive layer 2 is arranged on the outer side of the moderating units 1, thermal neutrons are captured by the thermal neutron sensitive layer 2 to generate cascade gamma rays, gamma rays in the gamma radiation field trigger a first number of moderating units 1 to respond, and gamma rays in the gamma radiation field and the cascade gamma rays trigger a second number of moderating units 1 to respond together.
In the embodiment, thermal neutrons are generated by slowing down neutrons emitted by a substance to be detected through the slowing-down unit 1, then the thermal neutrons are captured through the thermal neutron sensitive layer 2 to generate cascade gamma rays, energy can be deposited by the gamma rays in the gamma radiation field in the plurality of slowing-down units 1 to cause the first number of slowing-down units 1 to respond, and energy deposited by the gamma rays and the cascade gamma rays in the gamma radiation field in the plurality of slowing-down units 1 together can cause the second number of slowing-down units 1 to respond, so that when the substance to be detected is detected, neutron gamma can be discriminated through the response number of the slowing-down units 1, on one hand, detection steps can be simplified, detection time is short, the occurrence of misjudgment can be reduced, and the detection accuracy of the neutron to be detected is improved; on the other hand, the interference influence of the gamma rays in the gamma radiation field on the neutron detector 100 can be reduced, and the neutron-gamma discrimination ratio can be improved.
In one embodiment, the neutron detector 100 includes a plurality of photodetectors. Illustratively, neutrons to be measured of a substance to be measured can be moderated by the moderating unit 1 to generate thermal neutrons. The thermal neutron sensitive layer 2 is arranged on the outer side of the moderating unit 1, thermal neutrons are captured by the thermal neutron sensitive layer 2 to generate cascade gamma rays, the gamma radiation field deposits energy in the moderating unit 1 to generate first scintillation light, and the gamma rays of the gamma radiation field and the cascade gamma rays deposit energy in the moderating unit 1 together to generate second scintillation light. Each of the moderator cells 1 is coupled to at least one photodetector, which is capable of responding to the first scintillation light or the second scintillation light.
In this embodiment, a neutron to be detected emitted by a substance to be detected is first slowed by the slowing unit 1 to generate a thermal neutron, then the thermal neutron is captured by the thermal neutron sensitive layer 2 to generate a cascade gamma ray, the gamma ray in the gamma radiation field can deposit energy in the slowing unit 1 and emit first scintillation light, the gamma ray and the cascade gamma ray in the gamma radiation field together deposit energy in the slowing unit 1 to emit second scintillation light, and finally the first scintillation light or the second scintillation light is responded by the photodetector, that is, the gamma ray in the gamma radiation field is detected by the neutron detector 100 along with the neutron to be detected emitted by the substance to be detected, the gamma ray in the gamma radiation field directly penetrates through the neutron sensitive layer to directly deposit energy in the slowing unit 1 to emit the first scintillation light, the neutron to be detected also penetrates the neutron sensitive layer first, then the thermal neutron is slowed by the slowing unit 1 and is scattered in a direction away from the slowing layer, the scattered thermal neutron is captured by the thermal sensitive layer 2 located outside the slowing unit 1 to generate the cascade gamma ray, the slow ray escapes to the gamma ray deposition unit 1, and finally the cascade gamma ray and the thermal neutron radiation unit can generate the cascade gamma ray and generate the gamma ray, so that the thermal neutron radiation field and the cascade gamma ray can generate the gamma ray and the cascade gamma ray 1 and the cascade gamma ray can generate the gamma ray, and the cascade gamma ray can generate the gamma ray. Therefore, when a substance to be detected is detected, the neutron gamma is discriminated through the neutron detector 100 consisting of the plurality of slowing units 1, the thermal neutron sensitive layer 2 and the plurality of photoelectric detectors, so that on one hand, the detection steps can be simplified, the detection time is short, the occurrence of misjudgment can be reduced, and the detection accuracy of the neutron to be detected is improved; on the other hand, the interference influence of the gamma rays in the gamma radiation field on the neutron detector 100 can be reduced, and the neutron-gamma discrimination ratio is improved.
It should be noted that the neutron-gamma discrimination ratio is a ratio of neutron detection efficiency to finger-gamma detection efficiency.
It should be noted that, the gamma ray in the gamma radiation field herein refers to a high-energy gamma ray, such as a gamma ray with energy greater than 300 keV.
It is understood that the misjudgment described herein refers to the slowing down response caused by the gamma ray in the gamma radiation field and the response caused by the photo detector as the neutron to be measured,
for example, in an embodiment, the shape of the slowing-down unit 1 is not limited, and may be, for example, a rectangular parallelepiped, a cube, or another shape.
For example, in an embodiment, the photodetector may be a photomultiplier tube, for example, a silicon photomultiplier tube, so that by receiving the first scintillator and the second scintillator, an electrical signal may be emitted, and finally detecting and analyzing the electrical signal, the type of particles emitted by the substance to be detected and the detection efficiency may be obtained.
Illustratively, in one embodiment, the moderating unit 1 may be a plastic scintillator, so that the neutron detector 100 is inexpensive to manufacture, and the moderating unit 1 may be manufactured in various shapes according to the manufacturing requirements. In some embodiments, the plastic scintillator is not limited to the model, and may be EJ-200, for example, so that the light emitting efficiency of the first scintillation light and the second scintillation light may be improved, the photoelectric conversion by the photodetector may be facilitated, the accuracy is high, and the response rate is high. Of course, other models are possible, such as EJ-204 or EJ-208, etc.
It is understood that the moderating unit 1 moderates the neutrons to be measured by the hydrogen atoms inside.
Illustratively, in an embodiment, two end faces of the slowing unit 1 along the length direction thereof are coupled with a photodetector, so that the loss of light can be reduced to improve the detection accuracy of the neutron detector 100.
In one embodiment, the neutrons to be detected are fast neutrons. Therefore, the nuclear material with radioactivity can be conveniently detected, and the safety is high.
The fast neutrons are neutrons with energy between 0.1Mev and 20 Mev.
Thermal neutrons are neutrons with energies less than 1 keV.
In the prior art, the thermal neutron sensitive layer 2 of the neutron detector 100 is 3 He tube, due to 3 The shortage of He gas causes the price to be continuously increased, and therefore, the manufacturing cost of the neutron detector 100 is greatly increased.
For example, in one embodiment, the thermal neutron sensitive layer 2 may be made of a material nat Gd 2 O 3 (gadolinium oxide), the manufacturing cost is low. It will be appreciated that the above-described, nat Gd 2 O 3 in (1) 155 Gd (60900 barns) and 157 gd (25400 barns) has a very large thermal neutron reaction cross section, and therefore, can be used for fast neutron detection.
In one embodiment, referring to fig. 4, the neutron detector 100 includes a reflective layer 3, and the reflective layer 3 is disposed on the outer periphery of each of the slowing units 1. Illustratively, the slowing-down unit 1 is in the shape of a rectangular parallelepiped, the reflective layer 3 includes 4 side faces among 6 faces of the slowing-down unit 1, and the other 2 end faces are used for coupling the photodetectors, so that the first scintillation light and the second scintillation light scattered outwards by the slowing-down unit 1 can be reflected back to the slowing-down unit 1 through the reflective layer 3 located outside the slowing-down unit 1, thereby avoiding the situation that the photodetectors affecting other slowing-down units 1 generate false responses, and the detection accuracy is good.
For example, in an embodiment, the position of the reflection layer 3 is not limited, and for example, the reflection layer may be disposed between the thermal neutron sensitive layer 2 and the slowing unit 1.
Illustratively, in one embodiment, the reflective layer 3 may be Mylar (Mylar film), for example, an aluminized Mylar film.
In one embodiment, referring to fig. 1, a plurality of moderating units 1 are arranged along the width direction of a neutron detector 100 to form a moderating layer. Illustratively, the number of the slowing-down units 1 is not limited, and for example, the number may be 16, and 16 slowing-down units 1 are arranged along the width direction of the neutron detector 100 to form a slowing-down layer. A plurality of moderating layers are stacked in the thickness direction of the neutron detector 100.
For example, in an embodiment, the incident surface of the neutron detector 100 is not limited, for example, the incident surface may be one of two side surfaces along the thickness direction of the neutron detector 100, so that the capture area for the gamma rays in the gamma radiation field and the neutrons to be detected may be increased, and the detection efficiency is high.
In one embodiment, the number of the slowing-down layers is between 3 and 5. Illustratively, the number of the slowing-down layers is 4, so that the cost can be saved, and meanwhile, the detection efficiency of the neutrons to be detected can be improved.
In some embodiments, please refer to fig. 5, where fig. 5 is a graph of a relation between the number of layers of the slowness layer and the detection efficiency of the neutrons to be detected, it can be seen that the detection efficiency of the neutrons to be detected exponentially increases with the increase of the number of layers of the slowness layer when 1 to 3 layers are provided, when 3 to 5 layers are provided, the increase becomes slow, and when 5 layers are exceeded, the detection of the neutrons to be detected remains approximately unchanged, therefore, when the number of layers of the slowness layer is 1 to 3 layers, because the total thickness of the slowness layer is thin, the gamma radiation field and the neutrons to be detected may directly penetrate through the multiple layers, resulting in low detection efficiency and inaccurate detection; when the number of layers of the slowdown layer reaches 5 layers, since the detection efficiency reaches the maximum, the cost is increased and the economical efficiency is poor due to the increase of the number of layers again.
In one embodiment, referring to fig. 4, a thermal neutron sensitive layer 2 is disposed around the outer periphery of each moderating unit 1. Exemplarily, taking the formation of the moderation units 1 as a cuboid as an example, 4 side surfaces of 6 surfaces of each moderation unit 1 are wrapped by one thermal neutron sensitive layer 2, so that thermal neutrons can be captured from multiple directions to improve the detection efficiency of neutrons to be detected.
In some embodiments, referring to fig. 6, fig. 6 is a graph of a relationship between a thickness of the thermal neutron sensitive layer 2 and a detection efficiency of neutrons to be detected, an abscissa in the graph is the thickness of the thermal neutron sensitive layer 2, and an ordinate is the detection efficiency of neutrons to be detected, where a curve with a square in the graph is a relationship between the detection efficiency of neutrons to be detected of the thermal neutron sensitive layer 2 around the outer peripheral surface of each moderating unit 1 and the thermal neutron sensitive layer 2, and it can be seen from fig. 6 that the detection efficiency of neutrons to be detected of the placement manner in which the thermal neutron sensitive layer 2 is arranged around the outer peripheral surface of each moderating unit 1 is the highest.
In an embodiment, referring to fig. 4, the neutron detector 100 includes a first protection layer 4, and the first protection layer 4 is disposed around the outer periphery of the thermal neutron sensitive layer 2. Illustratively, the first protection layer 4 is disposed on the surface of the thermal neutron sensitive layer 2 far from the reflection layer 3, so that the thermal neutron sensitive layer 2 can be protected from being scratched to influence the detection accuracy.
In an exemplary embodiment, the material of the first protection layer 4 may be Tedlar (polyvinyl fluoride).
In one embodiment, a thermal neutron sensitive layer 2 is laid between two of the plurality of slowdown layers. Exemplarily, taking 4 slowing-down layers as an example, a thermal neutron sensitive layer 2 can be placed between two of the 4 slowing-down layers, so that the usage amount of the thermal neutron sensitive layer 2 can be reduced, and the cost can be saved.
In one embodiment, referring to fig. 1 and 2, a thermal neutron sensitive layer 2 is disposed on each of two adjacent moderating layers. Exemplarily, taking 4 moderation layers as an example, one thermal neutron sensitive layer 2 may be laid in each two adjacent layers of the 4 moderation layers, that is, 3 thermal neutron sensitive layers 2 are laid in the 4 moderation layers, so that the amount of the thermal neutron sensitive layer 2 may be reduced, and the detection efficiency of the neutron to be detected may also be ensured.
For example, in an embodiment, referring to fig. 6, different placement manners of the thermal neutron sensitive layer 2 may be selected according to the requirement of the detection efficiency of the neutrons to be detected. For example, for a scene with a high detection efficiency requirement of neutrons to be detected, a placement mode that the thermal neutron sensitive layer 2 is arranged around the outer peripheral surface of each moderating unit 1 can be selected; for the scene needing to reduce the use cost, a placing mode of laying a thermal neutron sensitive layer 2 in a plurality of moderation layers can be selected; for the scene with requirements on the use cost and the detection efficiency of neutrons to be detected, a placing mode that one thermal neutron sensitive layer 2 is laid between every two adjacent slowdown layers can be selected. The selectivity is high.
In one embodiment, the thickness of the thermal neutron sensitive layer 2 is 20 μm to 30 μm. For example, referring to fig. 6, fig. 6 shows three different placement methods of the thermal neutron sensitive layer 2, and as can be seen from fig. 6, when the thickness of the thermal neutron sensitive layer 2 may be 20 μm to 30 μm, such as 25 μm, the cost is considered, and at the same time, the detection efficiency during measurement is improved, for example, the placement method of the thermal neutron sensitive layer 2 around the outer circumferential surface of each moderating unit 1, and when the thickness of the thermal neutron sensitive layer 2 is 25 μm, the detection efficiency of neutrons during measurement can reach about 65%; if a placement mode that one thermal neutron sensitive layer 2 is laid on each two adjacent slowdown layers is adopted, when the thermal neutron sensitive layer 2 is 25 micrometers, the detection efficiency of neutrons to be detected can reach about 55%; and as for the placement mode of laying a thermal neutron sensitive layer 2 between two of the plurality of slowdown layers, when the thermal neutron sensitive layer 2 is 25 mu m, the detection efficiency of the neutrons to be detected can reach about 47 percent.
It can be understood that, the thickness of the thermal neutron sensitive layer 2 described herein refers to the thickness of a single layer and does not refer to the total thickness of the thermal neutron sensitive layer 2, and for example, four moderation layers are taken, each thermal neutron sensitive layer 2 is 25 μm, for example, the total thickness of the thermal neutron sensitive layer 2 in the placement method of the thermal neutron sensitive layer 2 around the outer peripheral surface of each moderation unit 1 is 200 μm, the total thickness of the thermal neutron sensitive layer 2 in the placement method of one thermal neutron sensitive layer 2 between two of the plurality of moderation layers is 25 μm, and the total thickness of the thermal neutron sensitive layer 2 in which one thermal neutron sensitive layer 2 is laid between each two adjacent moderation layers is 75 μm.
In an embodiment, referring to fig. 3, the neutron detector 100 includes a second protective layer 5, and the second protective layer 5 is disposed on the outer periphery of each slowing unit 1. In this way, the thermal neutron sensitive layer 2 can be protected from being scratched to influence the detection accuracy.
In an exemplary embodiment, the material of the second protection layer 5 may be polyvinyl fluoride.
In one embodiment, the neutron detector 100 includes a lead plate, and a lead plate is disposed between each two adjacent moderation layers. Thus, gamma rays of a gamma radiation field of gamma scattering can be effectively shielded, so as to further improve the neutron-gamma discrimination ratio, and taking the placement mode that the thermal neutron sensitive layer 2 is arranged around the outer peripheral surface of each moderating unit 1 as an example, when no lead plate is placed, the neutron-gamma discrimination ratio is 390; after the lead plate is placed, the gamma discrimination ratio of the neutron can reach 802, and the influence of gamma rays in a gamma radiation field on the detection efficiency of the neutrons to be detected can be greatly reduced.
In one embodiment, the thickness of the lead plate is not limited, for example, each layer of lead plate may have a thickness of 3mm.
In another aspect, referring to fig. 7, a neutron detection method is provided in any embodiment of the neutron detector 100, where the neutron detection method includes:
s1, setting a first number of the slowing-down units responding to gamma rays in the gamma radiation field as a threshold value;
s2, determining that the substance to be detected has the neutrons to be detected under the condition that the total response quantity of the slowing-down units is larger than the threshold value.
In the embodiment, the first number of the moderating units 1 responding to the gamma rays in the gamma radiation field is set as the threshold, and the matter to be detected is determined to have the neutrons to be detected under the condition that the total response number of the moderating units 1 is greater than the threshold, so that on one hand, the detection steps can be simplified, the detection time is short, the occurrence of misjudgment is reduced, and the detection accuracy of the neutrons to be detected is improved; on the other hand, the influence of the gamma rays in the gamma radiation field on the detection efficiency of the neutrons to be detected can be reduced, and the neutron-gamma discrimination is improved.
In one embodiment, the threshold is between 2 and 4. For example, the threshold may be 3, please refer to fig. 8, fig. 8 is a relationship diagram between the response number of the slowing unit 1 and the number of signals, the abscissa of the diagram is the response number of the slowing unit 1, the ordinate of the diagram is the number of signals emitted by the photodetector after detecting neutrons to be detected and gamma rays in a gamma radiation field, it can be seen from fig. 8 that the response number of the slowing unit 1 caused by the incidence of the neutrons to be detected is about 1 to 14, the response number of the slowing unit 1 caused by the gamma rays in the gamma radiation field is about 1 to 4, and after setting the threshold to 3, gamma ray signals in most gamma radiation fields can be shielded to improve the neutron-gamma discrimination ratio.
Illustratively, in one embodiment, the gamma ray signals in the majority of the gamma radiation field may be shielded by controlling the number of responses of the photodetectors.
It should be noted that, because each of the slowing units 1 is connected with two photodetectors, it can be determined that the slowing unit 1 has responded only if the two photodetectors corresponding to each of the slowing units 1 have responses, for example, if the number of responses of the slowing units 1 is 2 to 4, the number of responses of the corresponding photodetectors is 4 to 8, so that the detection influence of the gamma ray in the gamma radiation field on the detection can be reduced, and the detection accuracy can be improved.
The above description is only a preferred embodiment of the present application, and is not intended to limit the present application, and it is obvious to those skilled in the art that various modifications and variations can be made in the present application. All changes, equivalents, modifications and the like which come within the spirit and principle of the application are intended to be embraced therein.
Claims (13)
1. A neutron detector, comprising:
a plurality of moderating units, by which neutrons to be detected of a substance to be detected can be moderated to generate thermal neutrons;
the thermal neutron sensitive layer is arranged on the outer side of the slowing-down units, the thermal neutron is captured by the thermal neutron sensitive layer to generate cascade gamma rays, gamma rays in a gamma radiation field trigger a first number of the slowing-down units to respond, and the gamma rays in the gamma radiation field and the cascade gamma rays trigger a second number of the slowing-down units to respond together.
2. The neutron detector of claim 1, wherein the neutron detector comprises a plurality of photodetectors, and each of the moderating units is coupled to at least one of the photodetectors.
3. The neutron detector of claim 1, wherein the neutron detector comprises a reflective layer, the reflective layer being disposed on an outer peripheral surface of each of the moderating units.
4. The neutron detector of claim 1, wherein a plurality of the moderating units are arranged in a width direction of the neutron detector to form a moderating layer, and a plurality of the moderating layers are stacked in a thickness direction of the neutron detector.
5. The neutron detector of claim 4, wherein an outer periphery of each of the moderating units is surrounded by the thermal neutron sensitive layer.
6. The neutron detector of claim 5, wherein the neutron detector comprises a first protective layer, the first protective layer being surrounded by an outer peripheral surface of the thermal neutron sensitive layer.
7. The neutron detector of claim 4, wherein one of the thermal neutron sensitive layers is disposed between two of the plurality of moderating layers, or,
and one thermal neutron sensitive layer is paved on each two adjacent slowdown layers.
8. The neutron detector of claim 7, wherein the neutron detector comprises a second protective layer, the outer circumferential surface of each of the moderating units being provided with the second protective layer.
9. The neutron detector of claim 4, wherein the neutron detector comprises a lead plate, and a layer of the lead plate is disposed between each two adjacent moderating layers.
10. The neutron detector of claim 4, wherein the number of moderating layers is between 3 and 5.
11. The neutron detector of claim 1, wherein the thermal neutron sensitive layer has a thickness between 20 μ ι η and 30 μ ι η.
12. A neutron detection method, which is used for the neutron detector according to any one of claims 1 to 11, the detection method comprising:
setting a first number of the slowing-down units responsive to gamma rays in the gamma radiation field to a threshold value;
and determining that the substance to be detected has the neutrons to be detected under the condition that the total response number of the slowing-down units is larger than the threshold value.
13. The detection method according to claim 12, wherein the threshold value is between 2 and 4.
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