JPH0458570A - Neutron detector - Google Patents

Abstract

PURPOSE:To achieve detection positively and efficiently by forming a substance with a high reaction section area with a neutron on a surface of an alpha-rays detection part where storage information is inverted due to intrusion of the alpha-rays. CONSTITUTION:A MOS type transistor part Tr and a capacitor (charge accumulation part) C are provided on a P<-> substrate 1. In this case, the transistor part Tr consists of a pair of drain regions D and source region S as well as a gate G which is located at the middle. Then, a substance (B, B2O3, BN, B4C, etc.) which contains <10>B as a main constituent is formed as a reaction film 3 on a conduction layer 2 of the capacitor part C and a neutron deceleration material is formed as a layer 4 on a surface of the reaction film 3, thus enabling neutron to be changed into alpha-rays with a film made of a substance having a large reaction section area with the neutron and enabling it to be detected by the alpha-rays detection part for detecting neutron positively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a neutron detection device that detects neutrons using a phenomenon in which stored information (bits) is inverted due to the intrusion of alpha rays.

[Conventional technology]

Conventionally, dynamic memories such as DRAM (dynamic random access memory) or CCD (charge-coupled device) have been used to detect so-called soft errors, a phenomenon in which the take stored in the memory is reversed due to the intrusion of alpha rays. It has been proposed to detect alpha rays by
-18044 publication JP 63-40892 publication,
(See Japanese Patent Application Laid-Open No. 63-61983). Here, a soft error is defined as a single bit error that occurs randomly in memory and does not occur repeatedly, and the bit that caused the soft error is completely recovered by the next write cycle. It has the characteristic of being

[Problem to be solved by the invention]

On the other hand, since neutrons have no electric charge, they have the ability to ionize transparent substances and generate electron-hole pairs ('t4 dissociation ability).
Therefore, it is difficult to detect neutrons using the conventional detection device using the above-mentioned dynamic memory.

Therefore, as a device for detecting neutrons, it has been proposed that 10B is introduced into the radiation detection region as a holon or impurity that contains 10B at a higher concentration than its natural abundance (see Japanese Patent Application Laid-Open No. 1-204466). ). However, in this neutron detection device, there is a limit to the amount of B that can be introduced as an impurity, and a large amount of IOB, that is, a source of alpha rays, cannot be introduced, resulting in a problem of low detection efficiency.

The present invention has been made in view of the above circumstances, and its purpose is to be able to reliably detect neutrons,
Another object of the present invention is to provide a neutron detection device that can improve detection efficiency.

[Means to solve the problem]

In order to achieve the above object, claim 1 of the present invention is to form a film of a substance having a high cross section of reaction with neutrons on the surface of the alpha ray detection section where stored information is reversed by the intrusion of alpha rays. .

A second aspect of the present invention is that a layer of a neutron moderator material is formed on the surface of a film made of a material having a high reaction cross section with neutrons.

[Effect]

In the neutron detection device of the present invention, a film of a material having a high reaction cross section with neutrons formed on the surface of the alpha ray detection section converts neutrons into alpha rays, and these alpha rays are detected by the alpha ray detection section. to detect neutrons.

Furthermore, the layer of neutron moderator substance formed on the surface of the film slows down fast neutrons into thermal neutrons, increases the (n, α) reaction cross section in the film, and improves the reaction rate.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 to 3.

The basic configuration of this embodiment is as shown in FIGS. 2 and 3.
This is similar to the memory cell section of a conventional DRAM. That is, reference numeral 1 is a P-substrate, and on this P-substrate 1, M
O3O3 site 9fu2fu2 is there. It is composed of a pair of train regions and source regions S arranged on the P substrate 1 at a predetermined interval, and a gate G located between these regions.

Further, when alpha rays α enter the capacitor section C, the accumulated charges are affected, and an inversion phenomenon of stored information occurs. Furthermore, the bit line BL is connected to the train area, and the word line W is connected to the gate G.
L is connected.

Furthermore, a positive voltage +■ is applied to the conductor layer 2 of the capacitor section C. , are applied, and the substrate 1 is grounded.

As shown in FIG. 1, a material (B
, B, O, BN, B4C, etc.) are formed as the reaction film 3. Moreover, a neutron moderator is formed as a layer 4 on the surface of the reaction film 3. Suitable neutron moderators have a large neutron scattering cross section, a small neutron absorption cross section, and a small mass number. However, examples of compounds include organic compounds containing a large amount of hydrogen such as paraffin and polyethylene, metal hydrides, and metal hydroxides.

To explain the thickness of the reaction film 3 in detail, first, the reaction between neutrons and 10B is n + 10B-1-α+7L i + 2. 7
8Me V, and the energy key emitted by alpha rays is monochromatic.

From the above reaction formula, the alpha radiation released is Si
The amount of charge created inside is 0.123 pC.

Further, the range of 2.78 MeV alpha ray α in Si is 123 μπ.

Here, let the rate at which generated electrons are collected in the memory cell be Q, and the amount of charge stored in the memory capacitor be Q.
s + The amount of charge generated by the incidence of alpha rays is Q
If α is 1/2X Q s <Qα, the stored information will be inverted. Here, Q
s is expressed as QS=CsxV, Cs is the capacitor capacity, and ■ is the write voltage. Therefore, we set the memory capacitor capacity to 2QfF, the write voltage to 5μ, and the collection efficiency to 50%.
%, the left side of the above equation is 50 fC, and the right side is 62 fC, and the amount of charge generated upon incidence of alpha rays is sufficient to invert the stored information. Therefore, the possible value of the right side of the above equation is 50
It is thicker than fC and up to 62fC.

By the way, as is well known, alpha rays with a certain amount of energy attenuate in matter and eventually lose all their energy. In this case, 2,78 generated in the reaction membrane 3
It is necessary to quantify whether the energy of MeV alpha rays can be attenuated to a certain extent depending on the film thickness.

Therefore, if alpha rays are generated on the top surface of the reaction membrane and are incident perpendicularly to the sensitive part of the detector as the minimum value, and alpha rays generated on the bottom surface are the maximum value, then The energy range of alpha rays is expressed as the amount of charge,
Electron-hole pairs can be generated at temperatures greater than 100 fC and up to 123 fC, and when converted into energy (determining stopping power), it is 2.25 to 2.78 MeV. Therefore, it is possible to recognize attenuation up to an energy of approximately Q, OM e~. The thickness is up to about 2 μm.

In the neutron detection device configured as above, “
The reaction film 3 containing B reacts with neutrons, generates alpha rays, and the alpha rays are absorbed into the capacitor section C of the memory cell.
By reaching this point and inverting the stored information, neutrons can be detected smoothly.

In addition, at this time, by forming the neutron attenuation layer 4 on the surface of the reaction membrane 3, the (n, α) reaction cross section with the reaction membrane 3 can be increased, and as a result, the reaction rate can be increased, and the neutron Detection sensitivity can be improved.

In the above embodiment, "B" was used as the substance that reacts with neutrons, but the material is not limited to this, and 8Li may be used, for example, LiF containing a large amount of @Li may be used.

〔Effect of the invention〕

As explained above, claim 1 of the present invention is that a material having a high cross section of reaction with neutrons is formed as a film on the surface of the alpha ray detection part whose stored information is reversed by the intrusion of alpha rays. A film of a substance with a high cross section of reaction with neutrons formed on the surface of the alpha ray detection section allows
By converting neutrons into alpha rays and detecting the alpha rays by the alpha ray detector, neutrons can be reliably detected and the detection efficiency can be improved.

In addition, claim 2 of the present invention is that a layer of a neutron moderator substance is formed on the surface of a film formed of a substance having a high reaction cross section with neutrons. By slowing down fast neutrons and turning them into thermal neutrons, the (n+α) reaction cross section in the film can be increased, and the reaction rate can be improved.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention,
Figure 1 is an explanatory diagram, Figure 2 is an explanatory diagram of the memory cell section, and Figure 3 is an explanatory diagram of the memory cell section.
The figure is an equivalent circuit diagram of the memory cell section. C. Capacitor section (charge storage section), 3 reaction membranes, 4-. Neutron moderation layer.

Claims (2)

[Claims] (1) A neutron detection device characterized in that a film of a substance having a high cross section of reaction with neutrons is formed on the surface of an alpha ray detection part whose stored information is reversed by the penetration of alpha rays. (2) A neutron detection device according to claim 1, characterized in that a layer of a neutron moderator material is formed on the surface of the film formed of a material having a high reaction cross section with neutrons.