JPH07176777A - Neutron detector and neutron monitor - Google Patents

Abstract

PURPOSE:To achieve the characteristics of detection sensitivity for incident neutron energy with a high sensitivity using one detection element by making thicker the effective thickness of a converter than the range of charged particles generated in the converter. CONSTITUTION:The neutron detector uses silicon semiconductor. P-type diffusion layer 2 and silicon insulation oxide film 3 are provided at the center region on the upper surface of a silicon detection element 1 and on the upper surface of the detection element 1 and the diffusion layer 2, respectively. Further, a granular converter 4 generating charged particles by reacting with thermal neutron and a proton radiator 5 generating protons by reacting with a high- speed neutron are provided on the upper surface of the insulation oxide film 3. Especially, the effective thickness of the converter 4 can be made thicker than the range of the charged particles generated in the converter 4, thus maintaining approximate x 50 sensitivity difference between low-energy and high-energy regions and achieving the response of 1cm dose equivalent wight using one detection element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neutron detector, and more particularly to a semiconductor type neutron detector suitable for use in a nuclear power plant, a reprocessing facility, an accelerator handling facility and the like.

[0002]

2. Description of the Related Art For dosimeters for neutron detection, I
CRP (International Committee on Radiological Prot
(1) dose equivalent response (characteristic of detection sensitivity to incident neutron energy)
Is required. This 1 cm dose equivalent response is 0.0
There is a sensitivity difference of about 50 times in the wide neutron energy range of 25 eV to 15 MeV (the sensitivity of the low energy region including thermal neutrons becomes about 1/50 of the high energy region at the boundary of 100 keV). It is necessary to maintain the response difference.

As a conventional personal dosimeter, the Radiatio
n Protection Dosimetory, Vol.27, No.3, p.145 ~ p.156 (1
989). In this known example, two individual semiconductor neutron detectors for detecting slow neutrons and for detecting fast neutrons are combined to form one personal radiation dosimeter. As another conventional example, International Publication No. WO91 / 174
There is one described in Japanese Patent No. 62-62. In this known example, a neutron detector is formed by forming a layer in which a converter for detecting slow neutrons and a proton radiator for detecting fast neutrons are mixed on the surface of one semiconductor neutron detecting element. In this known example, the effective thickness of the converter is set within a range that does not exceed the range of α rays within the converter.

[0004]

In the above-mentioned first conventional example, 1 cm in the energy range of 10 keV to 1 MeV.
There is a problem that the response of the dose equivalent is not satisfied, the processing circuit is complicated because two detectors are used, and the dosimeter becomes large.

Further, in the second conventional example, in order to have a sensitivity difference of about 50 times in the low energy region and the high energy region, the proton radiator of the proton radiator is made to correspond to the thickness of the converter which does not exceed the range of α rays. Since it is necessary to reduce the thickness, there is a problem that the sensitivity of detecting fast neutrons is reduced.

An object of the present invention is to provide a neutron detector which can realize a response of 1 cm dose equivalent with high sensitivity by using one detecting element.

[0007]

In order to achieve the above object, the present invention relates to a semiconductor radiation detecting element, a first substance which causes a nuclear reaction with a thermal neutron to generate a charged particle, and a fast neutron. A second substance that generates charged particles by the interaction with is provided, and the effective thickness of the first substance is thicker than the range of the charged particles generated in the substance.

Further, according to the present invention, on the surface of the semiconductor radiation detecting element, a first substance which causes a nuclear reaction with thermal neutrons to generate charged particles, and a second substance which generates charged particles by interaction with fast neutrons. And a third substance that absorbs the thermal neutrons is provided on the surface of or in the vicinity of the detection element, separately from the first substance, and the effective thickness of the first substance is It is thicker than the range of charged particles generated in the substance.

[0009]

According to the present invention, among the first substances, a substance having a thickness region equal to or less than the range of charged particles generated in the substance can be used for detecting thermal neutrons with the highest sensitivity, and The relative sensitivity of thermal neutrons to fast neutrons can be reduced by using the absorption effect of thermal neutrons by substances in the range exceeding the range. Further, by setting the thickness of the second substance to the maximum range of the charged particles generated in the substance, fast neutrons can be detected with the highest sensitivity. Therefore, the first
By adjusting the thickness of the substance, it is possible to maintain a sensitivity difference of about 50 times in the low energy region and the high energy region, and to realize a response of 1 cm dose equivalent with high sensitivity using one detection element. .

Further, according to the present invention, among the first substances, a substance in a thickness region below the range of charged particles generated in the substance can be used for detecting thermal neutrons with the highest sensitivity. The relative sensitivity of thermal neutrons to fast neutrons can be reduced by using the action of thermal neutrons absorbed by the substance in the region exceeding the range and the third substance. Furthermore, by setting the thickness of the second substance to the maximum range of the charged particles generated in the substance, fast neutrons can be detected with the highest sensitivity. Therefore, by adjusting the thicknesses of the first substance and the third substance, it is possible to realize a response of 1 cm dose equivalent with high sensitivity using one detection element.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment in which the present invention is applied to a semiconductor type neutron monitor. This neutron monitor is a neutron detector that detects neutrons and outputs a detection signal, a preamplifier 11 and a proportional amplifier 12 that input and amplify the output signal of the neutron detector through a coupling capacitor 10, and a proportional amplifier 12. The counter circuit 13 for counting the output signals of the above, and the operation display 14 for converting the count signal of the counter circuit 13 into the neutron amount and displaying it.

The neutron detector of this embodiment uses a silicon semiconductor. A P-type diffusion layer 2 is formed in the central region of the upper surface of the silicon detection element 1, and a silicon oxide insulating film is formed on the upper surfaces of the detection element 1 and the diffusion layer 2. (SiO ₂ film) 3 is provided. Further, a granular converter 4 that reacts with thermal neutrons to generate charged particles and a proton radiator 5 that reacts with fast neutrons to generate protons are provided on the upper surface of the oxide insulating film 3. The converter 4 may be boron or lithium that reacts with thermal neutrons to generate α rays, and the proton radiator 5 may be a hydrogen compound such as paraffin, polyethylene, or epoxy resin. Further, the signal extraction electrode 6 is electrically connected to a part of the diffusion layer 2 through the oxide insulating film 3, and the counter electrode provided on the lower surface of the detection element 1 is provided.
A reverse bias (-V) is applied to the signal extraction electrode 6 from the terminal 8 with respect to the (ground electrode) 7 to form a depletion layer 9 below the diffusion layer 2. When neutrons enter the detector, the charged particles generated by the reaction of the thermal neutron and the converter 4 and the protons generated by the reaction of the fast neutron and the proton radiator 5 enter the depletion layer 9 and the electron (e) -hole. (h) A pair of charges is generated, which becomes a neutron detection signal. Hereinafter, in this embodiment, an example in which boron is used for the converter 4 will be described.

Next, the details of the neutron detector will be described with reference to FIG. In FIG. 2, the signal extraction electrode 6, the counter electrode 7 and the like are omitted. In this detector, the detector body shown in FIG. 1 is provided in the center of the neutron moderator 20, and a thermal neutron absorber 21 having an opening is provided outside the neutron moderator 20. The neutron moderator (also referred to as a moderator) 20 may be paraffin, polyethylene, or the like, and the thermal neutron absorber 21 may be, in addition to boron or lithium, cadmium that absorbs thermal neutrons and does not generate charged particles. .

Thermal neutrons n _th incident on the detector from the outside
Passes through the opening ratio of the thermal neutron absorber 21 (ratio of the openings to the total surface area of the thermal neutron absorber), is decelerated by the neutron moderator 20, and reaches the detector body. On the other hand, the fast neutrons n _f are not absorbed by the thermal neutron absorber 21,
Only the neutron moderator 20 decelerates and reaches the detector body.

Here, the response characteristic of 1 cm dose equivalent required for the neutron monitor will be described with reference to FIG. 1 cm
The dose equivalent response is 10 keV to 1 as shown in FIG.
A sensitivity difference of about 50 times is required between MeV. The response R of the neutron monitor is the nuclear reaction cross section σ and the neutron flux φ.
And the following equation.

[0016]

[Equation 1] R (E) ∝N _B ∫ {σ _B (E) ・ φ (E)} dE + N _P ∫ {σ _P (E) ・ φ (E)} dE (Equation 1) where E is Neutron energy (MeV), N _B , N _P are the numbers of boron and hydrogen atoms contributing to detection, σ _B (E), σ _P (E)
Is the nuclear reaction cross section of boron and hydrogen. When E is 1 MeV or more, the proton beam generated by the proton radiator is the main component of the detection signal, and when E is 10 KeV or less, the α ray generated by the nuclear reaction of boron is the main component. In addition, a region of 1 MeV or more and 1
The region below 0 keV has a substantially flat response. In order to realize this response with the semiconductor detector having the structure shown in FIG. 2, the thickness of boron is important.

The relationship between the thickness of boron provided on the surface of the detecting element and the thermal neutron flux on the surface of the detecting element is as shown in FIG. As shown in the figure, as the boron thickness increases, the thermal neutron flux on the detection element surface decreases, and when the boron thickness increases to 30 μm or more, the neutron flux on the detection element surface decreases to a fraction. Furthermore,
When the thickness of boron is about 100 μm, the neutron flux on the detector surface is 1
/ 10 or less. Strictly speaking, the response characteristic varies somewhat depending on the structure of the neutron monitor. For example, the thickness of the proton radiator is set to the maximum energy of 15 Me of the response characteristic shown in FIG.
When the maximum range of protons corresponding to V is about 2 mm, a range of boron thickness of 30 μm to 200 μm is effective for obtaining a response characteristic of 1 cm dose equivalent while maintaining the mechanical strength as a detection element. It becomes a range.

That is, by setting the thickness of the proton radiator for detecting fast neutrons to about 2 mm, the detection sensitivity to fast neutrons is maintained at the highest sensitivity, and among the boron provided on the surface of the detection element, α rays in boron ( The relative sensitivity of thermal neutrons to fast neutrons can be adjusted to about 1/50 by using a portion with a thickness of more than about 10 μm, which is a range of 1.47 MeV), as a response of 1 cm dose equivalent. The characteristics can be achieved. At this time, in addition to the thickness of boron, by adjusting the thickness and aperture ratio of the thermal neutron absorber 21 and the thickness of the neutron moderator 20 of FIG. Can be achieved.

As described above, conventionally, it has been considered that the boron, which is provided thicker than the maximum range of α rays in boron, about 10 μm, is meaningless because it does not contribute to the detection of thermal neutrons. It can be seen that the present invention plays a very important role in adjusting the response of 1 cm dose equivalent. The above-mentioned boron thickness means the effective thickness of boron, and when it is mixed with the proton radiator 5, which is another substance, as shown in FIG. 2, it has a thickness corresponding to the mixing ratio. That is,
Assuming that the apparent thickness of boron is t ₀ and the porosity is ε, the effective thickness t of boron can be expressed by t = t ₀ (1-ε). Here, the porosity ε represents the ratio of the volume occupied by substances (including gas) other than boron within the apparent thickness t ₀ of boron. In other words, the boron thickness described here is 100%
It is the thickness converted to the thickness of ¹⁰ B. Also, when using a nuclear reaction substance (such as uranium) other than boron as the converter, it is necessary to make the effective thickness of the converter equal to or larger than the range of the charged particles generated by the substance.

FIG. 5 shows an example of measuring the response characteristics of the neutron monitor that realizes the first embodiment. From the figure, it can be seen that a neutron monitor having characteristics that match the response of 1 cm dose equivalent with high accuracy can be realized.

Next, a second embodiment in which the present invention is applied to a semiconductor type neutron detector will be described with reference to FIG. In this embodiment, a converter 4 and a proton radiator 5 are provided on the surface of the detection element 1, and a thermal neutron absorber 22 different from boron (for example,
Lithium and uranium). In the figure, the basic configuration of the neutron detector is schematically shown, and other detailed configurations including the neutron moderator 20 and the thermal neutron absorber 21 shown in FIG. 2 are omitted.

In the case of the detector having the structure of FIG. 6, thermal neutrons actually enter from both the left and right sides, so the thermal neutrons incident on the detector are absorbed by the converter 4 and the thermal neutron absorber 22, and the thermal neutron flux Has the most attenuated (distorted) distribution in the vicinity of the converter 4 and the thermal neutron absorber 22 as shown by the curve 23. In the figure, in order to explain the sensitivity adjustment according to the second embodiment, it is assumed that thermal neutrons are incident only from the left side of the detector, and the change of the thermal neutron flux with respect to the position of the detector structural material is shown. Thermal neutron flux phi ₀ incident from the left side of the detector is absorbed by the thermal neutron absorber 22 and the converter 4 decayed to phi _1, reaches the detecting element 1.

In the present embodiment, boron is used as the converter 4, its thickness is 10 μm, the thickness of the proton radiator 5 is 2 mm, and the total thickness of the converter 4 and the thermal neutron absorber 22 is 30 μm to 200 μm. In this configuration, the range of the charged particles generated by the reaction between the thermal neutrons and the thermal neutron absorber 22 is sufficiently smaller than the thickness of the proton radiator 5, so that the thermal neutron absorber 22 uses the thermal neutrons generated by the detection element 1. Does not contribute to detection. That is, according to the present embodiment, the thicknesses of the converter 4 and the proton radiator 5 are set to the maximum sensitivity of thermal neutrons and fast neutrons, respectively, and the fast neutrons are absorbed by the thermal neutron absorber 22. Relative sensitivity of thermal neutrons to
By adjusting to 50, the response of 1 cm dose equivalent can be easily realized. In FIG. 6, the thermal neutron absorber 22 and the proton radiator 5 are shown separately.
They may be provided in contact with each other, or cadmium or the like may be used as the thermal neutron absorber 22.

Next, a third embodiment in which the present invention is applied to a semiconductor type neutron detector will be described with reference to FIG. In the present embodiment, a thermal neutron absorber 25 made of the same material as the thermal neutron absorber 22 is provided in the vicinity of a predetermined distance from the back surface of the detection element 1 of the second embodiment shown in FIG. . Figure 7
6 also schematically shows the basic configuration of the neutron detector as in FIG. 6, and other detailed configurations including the neutron moderator 20 and the thermal neutron absorber 21 shown in FIG. 2 are omitted. .
Further, in order to explain the sensitivity adjustment according to the third embodiment,
Assuming that thermal neutrons are incident only from the left side of the detector,
The change in thermal neutron flux with respect to the position of the detector structure is shown. Thermal neutron flux phi ₀ incident from the left side of the detector, the heat is absorbed by neutron absorbers 22 and converter 4 attenuated to phi ₁ reaches the detector element 1, to ₂ phi is further absorbed by the thermal neutron absorber 25 Decay.

Also in this embodiment, boron is used as the converter 4, the thickness thereof is 10 μm, the thickness of the proton radiator 5 is 2 mm, and the converter 4 and the thermal neutron absorbers 22 and 2 are used.
The sum of the thicknesses of 5 is 30 μm to 200 μm. In this configuration, charged particles are also generated by the reaction between the thermal neutrons and the thermal neutron absorber 25, but the range thereof is sufficiently smaller than the thickness of the detection element 1, so the thermal neutron absorbers 22 and 25
Does not contribute to thermal neutron detection by the detection element 1. That is, according to the present embodiment, the thicknesses of the converter 4 and the proton radiator 5 are set to the maximum sensitivity of thermal neutrons and fast neutrons, respectively, and the thermal neutron absorbers 22 and 25 absorb the thermal neutrons. By adjusting the relative sensitivity of thermal neutrons to fast neutrons to about 1/50,
A response of 1 cm dose equivalent can be easily realized. Of course, the thickness of the thermal neutron absorbers 22 and 25 needs to be set in consideration of the nuclear reaction cross section of the material.

Although the thermal neutron absorber 22 and the proton radiator 5 are separated from each other and the detection element 1 and the thermal neutron absorber 25 are separated from each other in FIG. 7, they may be provided so as to be in contact with each other. However, cadmium or the like can be used as the thermal neutron absorbers 22 and 25.

In the above embodiment, the number of atoms N _B and N _P corresponding to the thicknesses of the neutron converter and the proton radiator that contribute to neutron detection in the number 1 are kept constant under the condition of the highest sensitivity, and the low energy is maintained. Neutron flux φ
By lowering (E), a large difference in sensitivity between the low energy region and the high energy region of neutrons is formed.

As another means for realizing a 1 cm dose equivalent response, the number of atoms N _B and N _{P of the} neutron converter and the proton radiator contributing to the detection of neutrons of the number 1 is so different that the detection element surface is greatly different. It is also possible to form a large difference in sensitivity between the low energy region and the high energy region of neutrons by adjusting the thicknesses of the neutron converter and the proton radiator provided in.

The other means will be described with an example in which boron is used as the neutron converter. In order to maintain the 50-fold sensitivity difference by making the thickness of the proton radiator thinner than 2 mm, (1) the thickness of boron contributing to the detection signal is set to 1
It should be sufficiently thinner than 0 μm, and no boron that absorbs thermal neutrons should not be provided outside the detection element, or (2) the boron provided outside the detection element should be thickened to distort the thermal neutron flux. Needs to be large enough.

FIG. 8 shows the boron thickness design conditions that satisfy the response of 1 cm dose equivalent with the thickness of the proton radiator provided in the detection element as a parameter. The relationship satisfying the response of 1 cm dose equivalent under the condition of (1) is the straight line 30 in FIG.
The relationship satisfying the response of 1 cm dose equivalent under the condition of is the curve 31 in FIG. A straight line 30 in FIG. 8 represents a condition for providing a thin boron film in proportion to the proton radiator thickness, and a curve 31 represents a condition for providing a thick boron film in inverse proportion to the proton radiator thickness. Although these conditions reduce the absolute sensitivity of the neutron monitor, they are 1 cm
The dose equivalent response is fully satisfactory. The condition of (1) above requires a technique for uniformly providing a thin film boron of about 100 to 1000 Å, so that it is difficult to manufacture a detector and it is also difficult to finely adjust the response. On the other hand, the condition (2) is technically easy to manufacture and flexible in terms of response adjustment.

Next, a fourth embodiment in which the present invention is applied to a semiconductor type neutron detector will be described with reference to FIG. In general,
In order to eliminate the directivity of neutron detection, it is best to make the detector shape spherical, but this increases the number of manufacturing steps and increases the cost. For this reason, in this embodiment, a cylindrical shape close to a sphere is adopted as the detector shape. That is, the disc-shaped detection element 1
The converter 4 and the proton radiator 5 are provided in a layered form on the surface of, and the periphery thereof is covered with a hollow cylindrical neutron moderator 20 and a thermal neutron absorber 21 having an opening.

In this embodiment, the thickness of the proton radiator 5 is set to about 0.3 mm or more, which is the lower limit determined by the mechanical strength, and about 2 mm or less, which is the upper limit corresponding to the maximum range of protons in the proton radiator 5. At the same time, boron is used as the converter 4 and the thermal neutron absorber 21, and the sum of the thicknesses of the proton radiator 5 is within the range of 30 μm to 200 μm.
Set according to the thickness of. A response of 1 cm dose equivalent can be achieved by using the relationship of FIG. 8 as a setting criterion of thickness. Further, the diameter D and the height L of the detector are made equal, and the wall thicknesses of the neutron moderator 20 in the radial direction and the height direction and the wall thicknesses of the thermal neutron absorber 21 in the radial direction and the height direction are the same. By doing so, a simple and non-directional detector can be easily realized.

In this embodiment, boron is used as the thermal neutron absorber 21, but lithium, uranium, cadmium or the like may be used instead of boron. In this case, these absorbers are used. In consideration of the absorption amount of thermal neutrons due to, the relationship between the thickness of the boron and the thickness of the proton radiator in FIG. 8 is corrected, and by setting the thickness of the converter 4 accordingly, a response of 1 cm dose equivalent can be achieved. it can. Further, as the converter 4, a granular one as shown in FIG. 1 may be used, and in this case, the sensitivity may be adjusted by the effective thickness.

Next, FIG. 10 shows a fifth embodiment in which the present invention is applied to a survey meter. This survey meter has a neutron moderator 20 that incorporates the neutron detector described above, a measurement system that measures the detection signal of the detector, and a calculator that calculates the value of 1 cm dose equivalent using the measurement signal of the measurement system. The measurement / calculation unit 32 and the display 33 for displaying the calculation result of the measurement / calculation unit 32 are provided. Thus, by using the neutron detector to which the present invention is applied in the survey meter,
A practical neutron survey meter that can obtain a cm dose equivalent response with high sensitivity can be easily realized.

Furthermore, FIG. 11 shows a sixth embodiment in which the present invention is applied to a neutron individual exposure dosimeter. The present dosimeter is a neutron detector 37 described above, a radiation measurement circuit 38 that amplifies and counts the detection signal of the detector 37, a calculator 39 that calculates the exposure dose using the measurement signal of the measurement circuit 38, Display 40 for displaying the dose of radiation obtained by the calculator 39 on an LCD or the like
A battery 34 for supplying electric power to the radiation measuring circuit 38, the computing unit 39 and the display 40, a carrying case 35 for housing these, and a clip 36 for fixing the carrying case 35 to the chest of the human body. Here, the radiation measuring circuit 32 is the coupling capacitor 1 shown in FIG.
0, preamplifier 11, proportional amplifier 12, and counting circuit 1
Built-in 3. The personal dosimeter cannot carry a large neutron moderator around the detector because it is portable. But,
Since the human body itself acts as a neutron moderator, 1 cm
The dose equivalent response can be easily maintained. As described above, by using the neutron detector to which the present invention is applied in the personal radiation dosimeter, it becomes possible to more accurately manage the personal radiation dose equivalent.

As described above, by using the present invention, the response characteristic of 1 cm dose equivalent having a difference of about 50 times in the low energy region and the high energy region can be easily and highly sensitively achieved with one semiconductor detector. However, various practical neutron monitors can be realized. In the above embodiments, an example using a silicon semiconductor has been described, but it can be easily applied to a neutron detector using another semiconductor material or a compound semiconductor.

[0037]

According to the present invention, it is possible to provide a neutron detector which realizes a response of 1 cm dose equivalent with high sensitivity by using one detecting element.

[Brief description of drawings]

FIG. 1 is a first example in which the present invention is applied to a semiconductor type neutron monitor.
FIG.

FIG. 2 is a detailed explanatory view of the neutron detector of FIG.

FIG. 3 is an explanatory view of a response characteristic of 1 cm dose equivalent.

FIG. 4 is a diagram showing the relationship between the thickness of boron provided on the surface of the detection element and the thermal neutron flux on the surface of the detection element.

FIG. 5 is a diagram showing an example of measurement of response characteristics of a neutron monitor that realizes the first embodiment.

FIG. 6 is a second example in which the present invention is applied to a semiconductor type neutron monitor.
FIG.

FIG. 7 is a third example in which the present invention is applied to a semiconductor type neutron monitor.
FIG.

FIG. 8 is a diagram showing conditions of boron thickness with respect to proton radiator thickness for satisfying a response of 1 cm dose equivalent.

FIG. 9 is a fourth example in which the present invention is applied to a semiconductor type neutron monitor.
FIG.

FIG. 10 is a diagram showing a fifth embodiment in which the present invention is applied to a survey meter.

FIG. 11 is a diagram showing a sixth embodiment in which the present invention is applied to a neutron individual exposure dosimeter.

[Explanation of Codes] 1 ... Detector element, 2 ... P-type diffusion layer, 3 ... Oxide insulating film, 4 ...
Converter, 5 ... Proton radiator, 6 ... Signal extraction electrode, 7 ... Counter electrode, 8 ... Terminal, 9 ... Depletion layer, 10 ... Coupling capacitor, 11 ... Preamplifier, 12 ... Proportional amplifier, 13 ... Counting circuit, 14 ... Calculation display device, 20 ... Neutron moderator, 21, 22, 25 ... Thermal neutron absorber, 32
… Measurement and calculation unit, 33… Display, 34… Battery, 35
... carrying case, 36 ... clip, 37 ... neutron detector, 38 ... measurement circuit, 39 ... arithmetic unit, 40 ... indicator.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Akihisa Umihara 5-2-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Omika factory

Claims (12)

[Claims] 1. A semiconductor radiation detection element is provided with a first substance that causes a nuclear reaction with thermal neutrons to generate charged particles, and a second substance that generates charged particles by an interaction with fast neutrons. In the neutron detector that detects the neutrons by detecting the charged particles, the effective thickness of the first substance is thicker than the range of the charged particles generated in the substance. Neutron detector. 2. The neutron detector according to claim 1, wherein
The neutron detector characterized in that the effective thickness t is expressed by t = t ₀ (1-ε) using the apparent thickness t _{0 of} the first substance and the porosity ε. 3. A semiconductor radiation detecting element is provided with a first substance that causes a nuclear reaction with thermal neutrons to generate charged particles, and a second substance that generates charged particles by interaction with fast neutrons. A neutron detector for detecting the neutrons by detecting the charged particles, wherein an effective thickness of the first substance is 30 μm to 200 μm
Neutron detector characterized by being in the range of. 4. A semiconductor radiation detecting element is provided with a first substance that causes a nuclear reaction with thermal neutrons to generate charged particles, and a second substance that generates charged particles by interaction with fast neutrons. A neutron detector for detecting the neutrons by detecting the charged particles, wherein the effective thickness of the first substance is thicker than the range of the charged particles generated in the substance, A neutron detector characterized in that the thickness of the substance is set to the maximum range of charged particles generated in the substance. 5. A semiconductor radiation detecting element is provided with a first substance that causes a nuclear reaction with thermal neutrons to generate charged particles, and a second substance that generates charged particles by interaction with fast neutrons. A neutron detector for detecting the neutrons by detecting the charged particles, wherein an effective thickness of the first substance is 30 μm to 200 μm
And a thickness of the second substance is about 2 mm. 6. A semiconductor radiation detecting element is provided with a first substance that causes a nuclear reaction with thermal neutrons to generate charged particles, and a second substance that generates charged particles by interaction with fast neutrons. A neutron detector for detecting the neutrons by detecting the charged particles, the third neutron detector absorbing the thermal neutrons separately from the first substance.
The substance is provided on or near the surface of the detection element, and the effective thickness of the first substance is made thicker than the range of the charged particles generated in the substance. The sum of the effective thicknesses of substances is
A neutron detector having a range of 30 μm to 200 μm. 7. A semiconductor radiation detecting element is provided with a first substance that causes a nuclear reaction with thermal neutrons to generate charged particles, and a second substance that generates charged particles by an interaction with fast neutrons. A neutron detector for detecting the neutrons by detecting the charged particles, the third neutron detector absorbing the thermal neutrons separately from the first substance.
The substance is provided on or near the surface of the detection element, and the effective thickness of the first substance is made thicker than the range of the charged particles generated in the substance. The sum of the effective thicknesses of substances is
The neutron detector is in the range of 30 μm to 200 μm, and the thickness of the second substance is set to a maximum range of charged particles generated in the substance. 8. A semiconductor radiation detecting element is provided with a first substance that causes a nuclear reaction with thermal neutrons to generate charged particles and a second substance that generates charged particles by interaction with fast neutrons. A neutron detector for detecting the neutrons by detecting the charged particles, the third neutron detector absorbing the thermal neutrons separately from the first substance.
The substance is provided on or near the surface of the detection element, and the effective thickness of the first substance is made thicker than the range of the charged particles generated in the substance. The sum of the effective thicknesses of substances is
The neutron detector is in the range of 30 μm to 200 μm, and the thickness of the second substance is about 2 mm. 9. A semiconductor radiation detecting element is provided with a first substance that causes a nuclear reaction with thermal neutrons to generate charged particles, and a second substance that generates charged particles by interaction with fast neutrons. In the neutron detector for detecting the neutrons by detecting the charged particles, the first substance is boron, and the effective thickness is 30 μm.
To 200 μm, wherein the second substance is a hydrogen compound, and the thickness thereof is about 2 mm. 10. The neutron detector according to claim 1, wherein the detector is covered with a neutron moderator and / or a thermal neutron absorber on both sides of the detector. Detector. 11. A neutron detector according to claim 1, an amplifier for amplifying a detection signal of the detector, a counting circuit for counting an output signal of the amplifier, and an output of the counting circuit. A neutron monitor, comprising: a calculation display for calculating a signal and displaying a calculation result. 12. A neutron individual exposure dosimeter comprising the neutron detector according to any one of claims 1 to 9.