JP2003167062A - Neutron position detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect the neutron position with high resolving power in simple constitution using<SP>3</SP>He gas sealed in a container. <P>SOLUTION: This neutron position detector includes a sealed space container 42 where mixed gas containing<SP>3</SP>He gas and additive gas is sealed at gas pressure with 5 to 20 atms in the interior thereof, and a resistance core wire 43 stretched in the sealed space container 42 and having fixed resistance per unit length in the longitudinal direction. In the state where neutrons are incident on the sealed space container 42, the output charge at both ends of the resistance core wire 43 are measured to detect the neutron position. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neutron position detector for detecting irradiation positions of neutrons emitted from, for example, a nuclear reactor and neutrons scattered by a sample.

[0002]

2. Description of the Related Art Scattering experiments using various kinds of radiation have been conducted in order to analyze the structure of a substance, and among them, X-rays are widely used. FIG. 5 is a diagram showing a state in which the position of the diffracted X-ray is detected by the X-ray spectroscopic device 1. For example, in the X-ray spectroscope 1, the sample 3 is irradiated with the X-rays 6 emitted from the radiation source 2, and the scattered X-rays from the sample 3 are diffracted by a crystal such as lithium fluoride or germanium (LiF, Ge). The X-rays 7 and 8 diffracted by 4 are detected by the position detector 5. The wavelength or energy of the diffracted X-rays 7 and 8 is specified based on the position detected by the position detector 5, and the structural analysis and analysis of the substance are performed.

X-rays are used for structural analysis and the like by interacting with electrons in substances, and although they are effectively used for analyzing substances in which electrons are involved in the bonding of atoms, for example, living organisms. It is not suitable for structural analysis of materials and magnetic materials. On the other hand, neutrons (rays), which are a type of radiation and interact with the protons that make up the nuclei in a substance, and have a magnetic moment, especially thermal neutrons or cold neutrons with low kinetic energy, are used for structural analysis of the biomaterials and magnetic materials, etc. Suitable for

For detecting the position of neutrons (hereinafter simply referred to as position detection), ³ H, which is an isotope of helium ( ⁴ He), is used.
It is known that the interaction between e and neutrons can be used. ³ He has a large nuclear reaction cross section with neutrons, for example, it has about 5500 barn for 2 Å neutrons, so it has high neutron detection efficiency, and it also interacts with γ-rays that often accompany neutrons. It has the advantage that the action sensitivity is low and the influence of γ-rays on the detection of neutrons can be reduced.

Neutron (n) interacts with ³ He to generate one tritium ( ³ H: hereinafter referred to as ³ H) and one proton (p) as shown in formula (1). To be done. n + ³ He → ³ H + p (1)

The ³ H and protons produced by the reaction of the formula (1) are emitted in substantially opposite directions in the state of ions, and proceed while ionizing atoms and molecules of the surrounding substance. The position where the neutron reacts with ³ He, that is, the neutron position is ³
H and protons are given by the center of gravity of the generated ionization charge, but since the range of ³ H (the average distance until a charged particle ionizes a substance and stops it) and the amount of ionized charge and those of protons are greatly different, ^The position of the center of gravity of the ionizing charge formed by ³ H and the proton deviates from the position of the neutron.
This deviation deteriorates the position resolution of neutron position detection. 1
With ³ He gas at atmospheric pressure, the range of protons is as large as 48.5 mm, so the distance that the center of gravity of the ionized charge shifts to the range of protons is large, and the positional resolution is low, and the range of protons is about 0. It is 8 times as large as 39 mm.

[0007]

FIG. 6 shows the case of about 1 atm.
It is a figure which shows the state of the position detection by the conventional neutron position detector 10 using ³ He gas. In order to detect the neutron position corresponding to a coarse position resolution of about 39 mm, the diffraction plate 11 and the neutron position detector 10 are arranged with a large interval, and the diffraction source 11 passes from the source 12 to the sample 13 and is reflected by the diffraction plate 11. A neutron position detector 10 having a large area has to capture the neutron position which is largely spread. Therefore, in the conventional neutron position detector 10,
Since hundreds of proportional counters 14 having a diameter of about 1 to 2 cm and containing ³ He gas of about 1 atm are provided side by side, the neutron position detector 10 has a size of several meters. As described above, in the conventional neutron position detector 10, there is a problem that the scattering test device 15 for detecting the neutron position becomes enormous, and a large number of proportional counters 14 are used, which is extremely expensive.

FIG. 7 is a schematic view showing the structure of another conventional neutron position detector 16. As a technique for solving the above-mentioned problem, there is another conventional neutron position detector 16 using a printed circuit board as shown below. Another conventional neutron position detector 16 is a container 19 in which high-pressure ³ He gas is introduced into its internal space 18.
And an upper cathode 20, an anode 21, and a lower cathode 22 composed of the printed circuit board provided in the container 19. Here, the lower cathode 22 is a so-called multi-cathode in which a plurality of conductors 23 are arranged in parallel on a substrate as a printed circuit board. Adjacent conductor 23 of lower cathode 22
A Delay-Line 25 is provided in each of the circuits 24 connecting the two.

[0009] In another conventional neutron position detector 16, neutron (n) is incident through the window 26 into the container 19, ³
When reacted with He, ³ H and a proton (p) are produced by the nuclear reaction formula (1). The electrons (e) generated by this ionization are accelerated by the electric field formed by the high voltage applied between the upper cathode 20 and the anode 21 to ionize other molecules. Such ionization is repeated, and electron avalanche occurs at a position corresponding to the neutron position on the anode 21 and a negative (−) charge 29 is accumulated. A positive (+) charge 30 is induced in the lower electrode 22 corresponding to the negative charge accumulated on the anode 21. When the + charge 30 induced in the lower electrode 22 is taken out from both ends 27 and 28 of the lower electrode 22, a De provided between adjacent conductors 23 is provided.
The lay-Line 25 causes a time difference in the charge output at the end 27 and the end 28. The neutron position is detected by converting this time difference into a position.

Another conventional neutron position detector 16
Shows the possibility of shortening the range of protons and increasing the position resolution by using high-pressure ³ He gas for detecting the neutron position, but there are the following problems. A pollutant gas is easily generated from the printed circuit board which is the lower electrode 22. Since this polluted gas interferes with the operation mechanism of the detector and lowers the detection sensitivity of the neutron position, the polluted gas must be continuously removed during the neutron position detection. Therefore, the other conventional neutron position detector 16 is provided with the gas circulation system 32 for circulating the gas in the container 19 by the pump 31, and the gas circulation system 3
A gas purifying device 33 for removing the contaminated gas must be provided in 2.

As described above, in another conventional neutron position detector 16, the gas circulation system 32 can be filled with only ³ gas.
Since He gas must be prepared, the cost of ³ He gas becomes large. Further, since the gas circulation system 32 equipped with the gas purifying device 33 is indispensable, it is difficult to move the scattering test device to a large size and move freely, and most of the neutron position detection is performed by a desired sample at a desired place. It is impossible.

It is an object of the present invention to have a ³ H sealed in a container.
It is an object of the present invention to provide a neutron position detector that can detect a neutron position with high resolution by using e gas and having a simple configuration.

[0013]

[Means for Solving the Problems] The present invention has ³ He inside.
A sealed space container in which a mixed gas containing a gas and an additive gas is sealed at a gas pressure of 5 to 20 atm, and a resistance core wire that is stretched in the sealed space container and has a constant resistance per unit length in the length direction. A neutron position detector including: and measuring output charge at both ends of a resistance core wire in a state where neutrons are incident on a sealed space container.

According to the present invention, the gas pressure of the mixed gas containing ³ He and the additive gas sealed in the sealed space container is set to 5
By increasing the pressure to -20 atm, the range of protons generated by the reaction of ³ He and neutrons can be shortened, so that the position resolution of neutron position detection can be improved. Further, it is possible to detect the neutron position with high positional resolution with a simple configuration in which the resistance core wire is stretched in the sealed space container and the output charge from the resistance core wire is measured when the neutron reacts with ³ He.

Moreover, since the neutron position can be detected by sealing off the expensive ³ He gas in the sealed space container, the running cost for neutron position detection can be suppressed at low cost. Furthermore, since a gas circulating system is not required and the detector can be downsized by the simple configuration as described above, it is possible to move the neutron position detector to a desired place and perform a neutron scattering test. Therefore, the versatility of the neutron scattering test in the structural analysis of substances can be remarkably enhanced.

The present invention is also characterized in that the resistance core wire has a resistance value of 10 to 200 kΩ.

According to the present invention, since the resistance value of the resistance core wire is selected in an appropriate range, fluctuation due to thermal noise from the resistance core wire can be sufficiently suppressed, and the position resolution in neutron position detection can be increased to 1 mm or less. it can.

According to the present invention, the resistance core wire has a diameter of 5
It is characterized in that it is a carbon wire of -20 μm.

According to the invention, the resistance core has a diameter of 5
A carbon wire of ~ 20 μm is selected. Carbon wire has a larger resistance per unit length than metal wire, so
By forming it so as to have a diameter of μm, it is possible to realize a resistance value suitable for measuring the output charge.

The present invention also provides the addition contained in the mixed gas.
The gas is composed of atoms with an atomic number of 18 or less.
Is a monoatomic molecular gas or a polyatomic molecular gas,
Argon (Ar), neon (Ne), methane (C
H_Four), Hydrogen (H₂), Carbon dioxide (CO₂),helium(^Four
He), ethane (CH₃CH₃), Propane (CH₃CH₂
CH ₃) And butane (CH₃(CH₂)₂CH₃) From
Contain one or more gases selected from the group
Is characterized by.

According to the present invention, the additive gas contained in the mixed gas is a monoatomic gas or a polyatomic molecular gas whose molecules are composed of atoms having an atomic number of 18 or less. It is possible to reduce the influence of γ-rays and reduce the range of protons to improve the position resolution of neutron position detection.

[0022]

1 is a partial sectional view showing a simplified structure of a neutron position detector 41 which is an embodiment of the present invention. The neutron position detector 41 has ³ He inside.
A sealed space container 42 in which a mixed gas containing a gas and an additive gas is sealed at a gas pressure of 5 to 20 atm, and a sealed space container 4
2 and a resistance core wire 43 which is stretched in 2 and has a constant resistance per unit length in the length direction.

The sealed space container 42 is a hollow container having a substantially cylindrical shape, and has flange portions 44a and 44b at both ends.
Of the outer layer container 45, the inner layer container 46 inscribed in the outer layer container 45, and the flange portions 44a, 4
4b, each of which is provided in contact with the inner flange plate 47a,
47b, and cover bodies 48a and 48b provided outside in contact with the middle flange plates 47a and 47b, respectively.

The outer layer container 45 is a stainless steel tube having the flange portions 44a and 44b formed at both ends thereof. A substantially rectangular opening 49 (hereinafter referred to as a window 49) extending in the axial direction is formed in the outer layer container 45, and neutrons enter the sealed space container 42 through the window 49. The inner layer container 46 has a thickness of about 1 to 2 mm and an inner diameter of 2.
It is an aluminum tube having a length of 0 cm and a length of about 10 cm. The aluminum inner layer container 46 is used as a cathode in the neutron position detector 41.

The middle flange plates 47a, 47b are ring-shaped members made of stainless steel, and the protrusions 50 are formed on the inner edges thereof. The lids 48a and 48b are made of stainless steel, and are members each having a flange portion formed on the periphery thereof and having a substantially C-shaped cross section. A gas supply pipe 51 for introducing the mixed gas into the sealed space container 42 is attached to the one lid 48 a. The supply port of the gas supply pipe 51 is configured to be able to close the mixed gas after being supplied into the sealed space container 42.

The outer layer container 45 and the middle flange plates 47a, 47
"b" is attached by a bolt 52 which is inserted through the through holes formed in the flange portions 44a, 44b of the outer layer container 45 and is screwed into the female screw portions formed in the middle flange plates 47a, 47b. When the outer layer container 45 and the middle flange plates 47a, 47b are mounted, the inner layer container 46 is pressed against the middle flange plates 47a, 47b via the first sealing material 53 made of polytetrafluoroethylene (PTFE). The mixture gas is prevented from leaking between the inner flange plates 47a and 47b and the inner layer container 46.

The middle flange plates 47a and 47b and the lid 4
8a and 48b are intermediate flange plates 47a and 4b through which the through holes 54 formed in the flange portions of the lids 48a and 48b are inserted.
It is mounted by a bolt 56 that is screwed with a female screw portion 55 formed on 7b. When the middle flange plates 47a, 47b and the lids 48a, 48b are attached, they are pressed against each other via the second seal member 58 made of PTFE, so that the middle flange plates 47a, 47b and the lids 48a, 48b are attached. Leakage of the mixed gas during the period is prevented. Thus, the inner and outer layer containers 45, 46, the middle flange plates 47a, 47b and the lid 4
An inner space 57 for sealing the mixed gas is formed by 8a and 48b.

The internal space 57 formed as described above.
A resistance core wire 43 is stretched in the axial direction of the sealed space container 42 and extends in the axial direction. The resistance core wire 43 is
It is used as an anode in the neutron position detector 41.
The end 59 of the resistance core wire 43 to be stretched is connected to the connector terminal 6
Connected to 0. The connector terminal 60 is the middle flange plate 4
It is supported by an insulating member 61 provided on 7a and 47b. A terminal cover 62 is provided on the connector terminal 60 arranged substantially in the center of the lids 48a and 48b so as to cover the connector terminal 60, and the internal space 57 is sealed with the mixed gas and the terminal cover 62 is interposed therebetween. Thus, the output charge at both ends of the resistance core wire 43 can be measured.

In the internal space 57 of the sealed space container 42,³
The mixed gas containing the He gas and the additive gas has a pressure of 5 to 20 atm.
It is sealed with gas pressure. The pressure range of the mixed gas is 5 to 2
The reason why it is limited to 0 atm is as follows. Sealed space container
With the neutrons that are injected into 42 ³It is generated by reacting with He
Protons collide with other gas molecules existing in the internal space 57.
Hit and lose energy. Therefore, in the internal space 57
The higher the density of gas molecules present in the
It can be shortened to improve the position resolution of neutron position detection.
Wear. If the pressure of the mixed gas is less than 5 atm, the internal space 57
The density of gas molecules inside is low and the range of protons is sufficient.
It cannot be shortened. The pressure of the mixed gas exceeds 20 atm
Although it is suitable for shortening the range of protons,
The operation mechanism of the detector is disturbed (electron avalanche in the gas
It does not generate normally). Therefore, the pressure of the mixed gas should be 5
-20 atm.

The additive gas contained together with ³ He in the mixed gas includes argon (Ar) and neon (Ne), which are monoatomic gas or polyatomic molecular gas whose molecules are composed of atoms having an atomic number Z of 18 or less. , Methane (CH ₄ ), hydrogen (H ₂ ), carbon dioxide (CO ₂ ), helium ( ⁴ He),
Ethane (CH ₃ CH _3), propane (CH ₃ CH ₂ CH ₃₎
One or more gases selected from the group consisting of and butane (CH ₃ (CH ₂ ) ₂ CH ₃ ) are preferably used.

The protons generated by the reaction between neutrons and ³ He lose their energy while ionizing the atoms and molecules existing around the protons, and stop their movement. That is, the range of protons is affected by the atoms and molecules existing around the protons when they move. Since the effect of stopping the movement of protons by colliding with protons is generally remarkable in atoms with a large atomic number Z, even if the gas pressure of the mixed gas is increased by only ³ He with a small atomic number Z, the protons The effect of shortening the range of can not be fully obtained.

In order to reduce the range of protons produced by the reaction between neutrons and ³ He, it is effective that an atom having a large atomic number Z is present around the moving proton. Since an atom with a large Z easily interacts with γ-rays, coexistence of an atom with a large atomic number Z and ³ He increases the background count due to γ-rays and interferes with the counting of neutrons. Such interaction with γ-rays (photoelectric effect) increases sharply in proportion to the 5th power of the atomic number Z, so that the atomic number Z can actually be used as the additive gas for the neutron position detector. Is an atom of 18 or less. However, an atom having a small atomic number Z is not sufficient to obtain the effect of reducing the range of protons as described above.

Therefore, the inventor has studied the phenomenon of loss of energy due to collision of moving protons with atoms / molecules, and has obtained the following findings. The protons lose their energy and stop their movement by colliding with the nuclear electrons of the atoms and electrons of the atoms constituting the molecule, which are around the atomic nucleus rather than the atomic nucleus. By selecting a monoatomic gas or a polyatomic molecular gas in which a molecule is composed of 18 or less atoms with an atomic number Z and the total number of extranuclear electrons of the molecule is at least ³ He or more as an additive gas,
It is possible to obtain a sufficient effect to reduce the range of protons. Since the total number of extranuclear electrons of the monoatomic gas or polyatomic molecular gas effectively acts to stop the movement of protons, the total number of extranuclear electrons of the molecule is hereinafter referred to as the effective atomic number Ze. To do. One example is methane (CH
The effective atomic number Ze of ₄ ) is 6 as the number of extraneous electrons of carbon (C) which constitutes methane, and 1 as the number of extraneous electrons of hydrogen (H).
It is 10 given by the sum of × 4 = 4. For example, when the additive gas includes n kinds of gases, the effective atomic number Ze of the additive gas is represented by Zei and the partial pressure ratio is represented by Ri on behalf of each kind of gas. It can be determined by 2).

[0034]

[Equation 1]

As the monoatomic gas or polyatomic molecular gas, which is composed of atoms having an atomic number Z of 18 or less and has an effective atomic number Ze of at least ³ He (Ze = 2) or more, and which is preferably used as an additive gas, the above-mentioned examples are given. Like neon (N
e: Ze = 10), methane (CH4: Ze = 10), argon (Ar: Ze = 18), hydrogen (H _2: Ze =
2), carbon dioxide (CO ₂ : Ze = 22), helium ( ⁴ H
e: Ze = 2), ethane (CH ₃ CH ₃ : Ze = 18),
There are propane (CH ₃ CH ₂ CH ₃ : Ze = 26), butane (CH ₃ (CH ₂ ) ₂ CH ₃ : Ze = 34) and the like. By using one or more gases selected from these groups as additive gas, it is possible to shorten the range of protons generated by the reaction between neutrons and ³ He and to enhance the neutron positional resolution. .

The resistance core wire 43 has a resistance of 10 to 200 kΩ.
The resistance value of is selected. The range of the resistance value of the resistance core wire 43 is limited to 10 to 200 kΩ for the following reason. FIG. 2 is a diagram for explaining the outline of the charge division method. FIG. 2 shows a resistance core wire 43 of length L (= L1 + L2) which is an anode stretched in the sealed space container 42. The neutrons entering the sealed space container 42 react with ³ He to generate protons and ³ H, and the generated particles ionize the surrounding gas to generate a large number of electrons. These electrons are accelerated by the electric field formed by the voltage applied between the cathode that also serves as the inner layer container 46 and the anode of the resistance core wire 43 to ionize other molecules, and such ionization is successively induced. Forming a so-called electron avalanche 65. Electronic avalanche 6
Since the electrons in 5 have a negative charge, the resistance core wire 4
3 integrated into the anode. The center of gravity 66 of the charge accumulated in the resistance core wire 43 is the neutron position where the neutron and ³ He react.

The charges accumulated in the resistance core wire 43 are measured as output charges at both ends of the resistance core wire 43. At this time, the electric charge Q1 measured at one end 67 of the resistance core wire 43 located at a distance L1 from the charge center of gravity 66 and the other end 68 of the resistance core wire 43 located at a distance L2 from the charge center of gravity 66 are measured. A relationship is established between the electric charge Q2 and the electric charge Q2, which is given by the equation (3). Q1: Q2 = L2: L1 (3)

From the relationship shown in equation (3), the ratio (Q1 / Q2) of the output charges measured at both ends 67, 68 of the resistance core wire 43 is replaced with the distance ratio (L2 / L1),
The charge center of gravity 66, that is, the neutron position, in the length L direction of the resistance core wire 43 can be obtained. Such a method is called a charge division method. The lower the resistance value of the resistance core wire 43 is, the more the fluctuation of the output charge due to the thermal noise is increased, and the resistance value is 10 kΩ.
If it is less than, it becomes practically difficult to detect and specify the charge center of gravity 66. When the resistance value of the resistance core wire 43 becomes large, the time spread of the output charge appearing at both ends of the resistance core wire 43 becomes large, and when the resistance value exceeds about 200 kΩ, this time spread exceeds the processing capacity of the constituent electronic circuit, which is obvious. The position resolution is deteriorated. Further, since it takes a long time to measure the output charge and the time required to detect the charge center of gravity 66 becomes long, the time resolution of the measurement is lowered and the practicality as a neutron position detector is lost. Therefore, the resistance value of the resistance core wire 43 is set in the range of 10 to 200 kΩ.

A carbon wire having a diameter of 5 to 15 μm is preferably used for the resistance core wire 43 having a resistance value of 10 to 200 kΩ as described above. The resistance core wire 43 as an anode in the neutron position detector to which the charge division method is applied needs to be a conductive material and has an appropriate resistance. In order to impart resistance to the conductive material, it is effective to reduce the diameter to reduce the cross-sectional area and increase the length. Although a metal can be cited as a material that can be easily thinned, for example, a kaluma wire (70% Ni-20% Cr-7% Al-Fe) having a diameter of 10 μm, which is an alloy thin wire of metal, has a resistance per unit length. 0.17 kΩ / cm, Nichrome wire with a diameter of 10 μm (80% Ni-20%
Cr) is only 0.12 kΩ / cm, which is a long anode to satisfy the above-mentioned resistance value range, and the neutron position detector becomes large in size and loses practicality.

The carbon wire has a well-established technology for thinning it as a so-called carbon fiber, and not only is it easily available, but the thinned wire has a resistance per unit length suitable as an anode. For example, with a carbon wire having a diameter of 7 μm, the resistance per unit length is 4.2 kΩ / cm, and a resistance value of 42 kΩ can be realized with a length of only 10 cm.

The diameter range of the carbon wire is 5 to 20 μm.
The reason for being limited to m is as follows. Diameter of carbon wire is 5
When the thickness is less than μm, it is difficult to handle the carbon wire and it is difficult to stretch the carbon wire in the internal space 57 of the sealed space container 42. If the diameter of the carbon wire exceeds 20 μm, the resistance per unit length decreases due to the increase in the cross-sectional area, so a long length is required to obtain the desired resistance value. Therefore,
The diameter of the carbon wire was in the range of 5 to 20 μm.

(Examples) Examples of the present invention will be described below. FIG. 3 is a diagram showing an outline of a neutron position detection test by the neutron position detector 41. An aluminum tube having a thickness of 1.5 mm and a length of 10 cm is used for the cathode which is the inner layer container 46, and a carbon wire having a diameter of 7.0 μm and a length of 10 cm is used for the anode which is the resistance core wire 43. Then, a neutron position detector 41 using 0.34 atm of ³ He gas and 10.04 atm of additive gas was prepared as the mixed gas.

The resistance value of the carbon wire used as the anode is 42 k.
It was Ω. The additive gas is composed of Ar gas, which is a monatomic gas composed of argon (Ar) having an atomic number Z of 18, and carbon (C) having an atomic number Z of 6 and hydrogen (H) of 1. Methane (CH, which is a polyatomic molecule gas)
₄ ) Gas was used by mixing 90% Ar and 10% CH ₄ in volume ratio. The effective atomic number Ze of the additive gas based on the formula (2) was about 16.6.

In the neutron position detector 41, three cadmium (Cd) plates 71, 72, 73 are provided at the window 49 portion, respectively.
The two slits 74 and 75 were formed by adhering so that a gap G of 5 mm was formed. Neutrons emitted from the neutron source 76 were made to enter the neutron position detector 41 from the slits 74 and 75, the output charge at both ends of the carbon wire 43, which was an anode, was measured, and the neutron position was detected by the charge division method. . The position resolution of the neutron position was evaluated by the full width at half maximum of the measured charge.

FIG. 4 is a diagram showing the results of the neutron position detection test. The channel number shown on the horizontal axis of FIG. 4 is a number assigned to each divided section for convenience in dividing the anode in the length direction so that the charge detection position in the length direction of the anode can be specified. Say that. Therefore, the channel number indicates the position in the length direction of the anode, and the horizontal axis indicates the distance.
The vertical axis in FIG. 4 represents the neutron count value.

Peaks 78 and 79 were detected at the position where the two slits 74 and 75 were formed, that is, at the neutron position in the line 77 that connects the count values in each channel. The half width obtained at the two peaks 78 and 79 was used as the position resolution of the neutron position. The position resolution at peak 78 was 0.93 mm, and the position resolution at peak 79 was 0.94 mm. 1 atmosphere of ³ H
The position resolution was remarkably improved by the neutron position detector 41 of the present invention as compared with the position resolution of 39 mm by e-gas.

In this neutron position detection test, the slits 74 and 7 formed by the Cd plates 71, 72 and 73 are used.
Since 5 was provided in a single layer, some neutrons were obliquely incident on the neutron position detector 41. As a result, the neutron position resolution remains at 0.93 to 0.94 mm. For example, it is judged that the position resolution of the neutron position detector 41 can be 0.5 mm or less by providing multiple slits and injecting neutrons into the neutron position detector 41 at an angle closer to vertical.

As described above, in the present embodiment,
Although carbon wire is used for the resistance core wire 43, the resistance core wire 43 is not limited to this and may be made of other material. In addition, as the additive gas, Ar,
Ne, CH ₄ , H ₂ , CO ₂ , ⁴ He, CH ₃ CH ₃ , CH ₃
CH ₂ CH ₃ and CH ₃ (CH ₂ ) ₂ CH ₃ are listed, but are not limited to the gases listed here, but other monoatomic gas or polyatomic gas composed of atoms having an atomic number Z of 18 or less. Atomic gas can be used.

[0049]

According to the present invention, ³ He reacts with neutrons by increasing the gas pressure of the mixed gas containing ³ He and the additive gas sealed in the sealed space container to 5 to 20 atm. Since it is possible to reduce the range of the protons that are generated, the position resolution of neutron position detection can be improved. Further, it is possible to detect the neutron position with high positional resolution with a simple configuration in which the resistance core wire is stretched in the sealed space container and the output charge from the resistance core wire is measured when the neutron reacts with ³ He.

Further, since the expensive ³ He gas can be sealed in the hermetically sealed space container to detect the neutron position, the running cost for detecting the neutron position can be suppressed at a low cost. Furthermore, since a gas circulating system is not required and the detector can be downsized by the simple configuration as described above, it is possible to move the neutron position detector to a desired place and perform a neutron scattering test. Therefore, the versatility of the neutron scattering test in the structural analysis of substances can be remarkably enhanced.

Further, according to the present invention, since the resistance value of the resistance core wire is selected in an appropriate range, the position resolution in neutron position detection can be increased to 1 mm or less.

Further, according to the present invention, a carbon wire having a diameter of 5 to 20 μm is selected as the resistance core wire. Carbon wire has a larger resistance per unit length than metal wire, so
By forming it so as to have a diameter of 20 μm, a resistance value suitable for measuring the output charge can be realized.

Further, according to the present invention, since the additive gas contained in the mixed gas is a monoatomic gas or a polyatomic molecular gas whose molecule is composed of atoms having an atomic number of 18 or less, a neutron position is detected. It is possible to reduce the influence of γ-rays at the same time and reduce the range of protons to improve the position resolution of neutron position detection.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a simplified configuration of a neutron position detector 41 which is an embodiment of the present invention.

FIG. 2 is a diagram illustrating an outline of a charge division method.

FIG. 3 is a diagram showing an outline of a neutron position detection test by a neutron position detector 41.

FIG. 4 is a diagram showing a neutron position detection test result.

FIG. 5 is a diagram showing a state in which the position of a diffracted X-ray is detected by the X-ray spectroscopic device 1.

FIG. 6 is a diagram showing a state of position detection by a conventional neutron position detector 10 using ³ He gas at about 1 atm.

FIG. 7 is a diagram showing a simplified configuration of another conventional neutron position detector 16.

[Explanation of symbols]

41 Neutron position detector 42 sealed space container 43 Resistance core wire (anode) 45 Outer layer container 46 Inner layer container (cathode) 49 windows

Claims (5)

[Claims] 1. A hermetically sealed space container in which a mixed gas containing ³ He gas and an additive gas is sealed at a gas pressure of 5 to 20 atm, and a unit length in the longitudinal direction stretched in the hermetically sealed space container. A neutron position detector including a resistance core wire having a constant resistance per unit, and measuring an output charge at both ends of the resistance core wire in a state where neutrons are incident on the sealed space container. 2. The neutron position detector according to claim 1, wherein the resistance core wire has a resistance value of 10 to 200 kΩ. 3. The neutron position detector according to claim 1, wherein the resistance core wire is a carbon wire having a diameter of 5 to 20 μm. 4. The additive gas contained in the mixed gas is a monoatomic gas or a polyatomic molecular gas whose molecule is composed of atoms having an atomic number of 18 or less. A neutron position detector according to claim 2. 5. The additive gas is argon (Ar), neon (Ne), methane (C).
H ₄ ), hydrogen (H ₂ ), carbon dioxide (CO ₂ ), helium ( ⁴
The He), ethane (CH ₃ CH _3), propane (CH ₃ CH ₂
The neutron position detector according to claim 4, which contains one or more gases selected from the group consisting of CH ₃ ) and butane (CH ₃ (CH ₂ ) ₂ CH ₃ ).