KR101267542B1 - a hihg efficient Monochromator coated with Supermirror or reflecting wall - Google Patents

Abstract

A high efficiency FADG monochromator coated with a mirror or reflector is disclosed. The FADG monochromator is characterized in that the upper and lower surfaces of each of a plurality of Si single crystal slabs is coated with nickel or neutron supermirror, which is a material having excellent neutron reflection.

Description

Highly efficient monochromator coated with Supermirror or reflecting wall}

The present invention relates to a neutron monochromator, and more particularly to a high efficiency monochromator coated with a mirror or reflector.

1 is an exemplary diagram showing diffraction by a single crystal, FIG. 2 is a graph showing a diffraction beam measurement of a general powder form material, and FIG. 3 is a shape of a drawing beam according to homogeneity of small crystals after mosaicing a crystal. 4 is an exemplary view showing a planar monochromator and a monochromator bent into a spherical surface, FIG. 5 is an exemplary view showing full asymmetric diffraction (FADG), and FIG. 6 is a view of a neutron beam according to a mosaic structure of a single crystal of FADG. An illustration showing the output form.

1 to 6, the repeating structure of the periodic crystal planes is used to diffract neutrons, electrons, X-rays, etc. (bragg peaks), and to extract one wavelength (crystal monochromator). There are several choices in this step determination, and the conditions under which diffraction is possible depending on the length of each grating plane is determined by bragg's law. That is, diffraction occurs when the difference in path way between beams diffracted between crystal planes is a multiple of incident wavelength. In the case of a single crystal, only one wavelength can be extracted by fixing the incident angle.

On the other hand, when the crystallized material is made into a powder form and incident on one wavelength, several diffraction beams can be observed by various crystal planes.

In order to extract a part of the white beam of a large energy region by the single crystal, it is necessary to apply temperature and pressure to the single crystal to form a mosaic crystal. A perfect crystal would not be available due to its low intensity because it only draws a single wavelength beam. In general, the crystal used as a monochromator is crushed into a mosaic, and simultaneously diffracts some wavelength regions around the wavelength to be extracted.

A good single crystal should have a uniform degree of mosaicing so that there is no beam separation in the form of a Gaussian in the shape of the outgoing beam.

Dr. Mikula, Czech, introduced a method of artificially giving a single crystal structure to a monochromatic structure to give a natural mosaic structure by bending a single crystal slab.

In this method, parallel beams can be generated by focusing the beam or suppressing dispersion depending on the degree of bending of the crystal plane.

Another idea, says Dr. Mikula, is that the diffraction beam travels along a single crystal by asymmetrically diffracting the crystal plane. In this case, not all single crystals are possible, but only Si, Zr, Al, etc. having a low neutron absorption coefficient are possible.

If the wavelength is 0.2nm, 39% of the incident neutrons are transmitted even though 95cm of Si is passed. Dr. Mikula predicts that even if a neutron with a wide line width is incident, the diffraction beam will have a narrower line width and thus a higher intensity.

However, in both methods, beams generated from neutral resources are not point or parallel beams, and when mosaicity is given to single crystals due to bending, additional dispersion is caused by heterogeneous mosaic structures, resulting in large beam loss.

The disadvantage of Dr. Mikula's asymmetric single crystals is that nickel on the surface of a commercially available thin Si-wafer (approximately 0.25 mm) can be easily obtained if the surface of the single crystal used as a monochromator is coated with a material such as nickel, which has excellent neutron reflection, or is rough. It is possible to increase the beam intensity by coating (Ni) or supermirror and applying it on the front and back of the monochromator.

In general, diffraction of beams in single crystal slabs is known to occur a lot on the front and back surfaces of the slab. In other words, when using a slab of 4 ~ 5mm thickness stacking multiple sheets of about 1mm there is an advantage of strength.

However, even in this case, when the dispersion is high, the diffracted beam does not completely diffraction but transmits. In the same manner as the above method, the surface of each slab is coated with a mirror or nickel, which is a reflective film, to increase the beam intensity through continuous reflection. Similarly, considering the surface roughness of the slab, a thin film of Si-wafer is coated with a reflective film and then placed in a reflector-coated portion.

The reflector coating is a monochromatic beam drawn according to the reflector selection such that M = 2 supermirror is twice the reflectivity of nickel and M = 3 supermirror is 3 times the reflectivity of nickel when the total reflection angle of nickel is 1. The angle of dispersion can be adjusted.

The problem to be solved by the present invention is that the beam generated from the neutral resource is not a point or parallel beam, and when the single crystal mosaicity due to bending gives additional dispersion caused by the heterogeneous mosaic structure, the second can block the beam loss To provide a high efficiency monochromator coated with a mirror or reflector.

In addition, another problem to be solved by the present invention is an ultra-mirror or reflector that can improve the intensity (intensity) by the reflection of the beam by coating a neutron reflector nickel (Ni) or a supermirror on the upper and lower single crystals of the FADG It is to provide a high efficiency monochromator coated with.

FADG monochromator according to an embodiment of the present invention for solving the above problems is continuously diffracted in the respective Si single crystal slab on the upper and lower surfaces of each of the plurality of Si single crystal slabs are stacked at regular intervals for beam extraction using diffraction Nickel or neutron mirror, which is a neutron reflector for diffraction beam non-transmission, is coated to prevent the beam from being transmitted from the upper and lower surfaces of each Si single crystal slab to the outside.

FADG monochromator according to another embodiment of the present invention for solving the above problems is formed with a mosaic structure each of the plurality of Si single crystal slabs having a different size, each of the plurality of Si single crystal slabs for beam extraction using diffraction Nickel or ultra-mirror for non-transmissive neutron reflector for diffraction beam to prevent the beam from being transmitted from the upper and lower surfaces of each Si single crystal slab to the outside so that the beam is continuously diffracted in each Si single crystal slab on the upper and lower surfaces This coated silicon wafer is characterized in that it is inserted.

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According to the present invention, when nickel (Ni) or a supermirror, which is a neutron reflector, is coated on and under a single crystal of the FADG, the intensity of the reflection of the beam is improved.

1 is an exemplary view showing diffraction by a single crystal.
2 is a graph showing a diffraction beam measurement of a general powder form material.
Figure 3 is an exemplary view showing the shape of the extraction beam according to the homogeneity of the small crystals after the mosaic of the crystal.
4 is an exemplary view showing a flat monochromator and a monochromator bent into a spherical surface.
5 is an exemplary view showing perfect asymmetric diffraction (FADG).
6 is an exemplary view showing an output form of a neutron beam according to a mosaic structure of a single crystal of FADG.
Figure 7 is an exemplary view showing a multi-slab monochromator coated with nickel or neutron mirror, which is a neutron reflector according to an embodiment of the present invention.
8 is an exemplary view showing a slab monochromator coated with nickel or a neutron mirror, which is a neutron reflector according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise.

In order to fully understand the present invention, operational advantages of the present invention, and objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the accompanying drawings which illustrate preferred embodiments of the present invention.

Before describing the present invention, reference is made to neutron mirrors.

Neutrons have a positive scattering length density for most elements except for some substances (Gd, Mn). This means that, unlike electromagnetic waves (visible line region), the angle of incidence between the direction of incidence of neutrons and the material plane is larger than the angle of refraction in the medium. This special property of neutrons and X-rays means that they can totally reflect when they enter the ideal material surface within critical angles.

Using this total reflection property of neutrons, the German Heinz Maier-Leibnitz, the first director of the institut Laue-Langevin, in 1963, introduced the basic concept of a 58Ni guide tube capable of transporting or transporting neutrons. Proposed for the first time. Since then, LLB, ILL, HMI, KURRI, and JAERI, the world's leading neutron scattering laboratories, have established neutron flow tubes using natural nickel (58Ni: 68%) and later established super mirror induction tubes to take the lead in the study of physical properties. have.

The neutron refractive index can be expressed by Equation 1 below, and the neutrons incident at an angle smaller than the critical angle are totally reflected as shown in the figure.

[Equation 1]

Above is an exemplary view showing reflectance spectra by FeCo alloy coated on an organic substrate.

The repeating structure of the periodic crystal planes is used to diffract neutrons, electrons, X-rays, etc., and to use them to extract one wavelength (crystalline monochromator). In addition to the repetition of the crystal plane in crystals of atomic units, this diffraction phenomenon can be seen in thin film structures in which two different materials are artificially repeated periodically. In 1976, Hungarian scientist FerencMezei introduced the theory that it is possible to widen the diffracted line width to the critical angle through repeated thickness changes of multilayer thin films. The mirror, which can extend the nickel's total reflection angle more than twice, was called a super mirror.

Figure 7 is an exemplary view showing a multi-FADG monochromator coated with a neutron reflector nickel or neutron mirror according to an embodiment of the present invention, Figure 8 is a neutron reflector nickel or neutron mirror according to another embodiment of the present invention Exemplary diagram showing a coated FADG monochromator.

As shown in FIG. 7, the FDGA monochromator 100 is coated with nickel or neutron supermirror, which is a material having excellent neutron reflection, on the upper and lower surfaces of each of the plurality of Si single crystal slabs 10 and 20.

As shown in FIG. 8, the FDGA monochromator 200 is a silicon wafer reflecting film 15 coated with nickel or an ultra mirror, which is a neutron reflector, on the upper and lower surfaces of each of a plurality of Si single crystal slabs 10 and 20. Is inserted.

In general, diffraction of beams in single crystal layers is known to occur a lot on the front and back surfaces of the layers. That is, when using a plurality of slabs of about 1mm overlapping than when using a sheet of 4 ~ 5 mm thick slab has the advantage of strength (intensity) (see Fig. 7).

However, even in this case, when the dispersion is high, the diffracted beam does not completely diffraction but transmits.

Therefore, the present invention can increase the intensity (intensity) of the neutron beam through the continuous reflection by coating the surface of each slab (10, 20) is coated with a mirror or a super mirror or nickel.

The silicon wafer reflective film 15 may have a thickness of 0.25 mm, and a thickness of each of the plurality of Si single crystal slabs 10 and 20 may be between 0.9 mm and 1 mm.

Therefore, according to the present invention, when nickel (Ni) or a supermirror, which is a neutron reflector, is coated on upper and lower surfaces of a single crystal of FADG, the intensity of the reflection of the beam is improved.

These effects are presented in the graphs inserted below, TEM measurement photos and ultra-reflective specular graphs.

(Bragg peak caused by repeatedly stacking nickel and titanium)

(TEM measurement photo of thin film lamination of ultra mirror)

(Super Mirror Reflectance Suppression)

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

10, 20: Si-slab 15: silicon wafer
100, 200: FADG Monochromator

Claims (2)

The beam is transmitted from the upper and lower surfaces of the respective Si single crystal slabs to the outside so that the beam is continuously diffracted in the respective Si single crystal slabs on the upper and lower surfaces of each of the plurality of Si single crystal slabs stacked at regular intervals and used for beam extraction using diffraction. FADG monochromator coated with nickel or neutron mirror, which is a neutron reflector for diffraction beam impermeability to prevent it from becoming.
Each of the plurality of Si single crystal slabs is formed in a mosaic structure having a different size, and each of the plurality of Si single crystal slabs for beam extraction using diffraction is continuously diffracted by the beam in each of the Si single crystal slabs on the upper and lower surfaces thereof. And a silicon wafer coated with a nickel or super mirror, which is a neutron reflector for diffraction beam impermeability, to prevent the beam from being transmitted from the upper and lower surfaces of each Si single crystal slab to the outside.

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