JP2002333482A - High sensitivity fast neutron fluorescence converter - Google Patents

Abstract

(57) [Summary] [PROBLEMS] By separating a part that emits fluorescence by reacting with fast neutrons and a part that propagates this fluorescence to an observation surface, even if the converter is thickened, light emission inside the converter can be observed. Since the light can be propagated with little loss, the amount of light emission can be increased. SOLUTION: A fiber sheet in which wavelength converting fibers having a light wavelength converting function are arranged and adhered, and a converter sheet which emits fluorescent light by high-speed neutron incidence are alternately brought into close contact with each other and then fixed, fixed and light-shielded except for the end face on the observation side. This is a high-sensitivity high-speed neutron fluorescence converter, which causes fluorescence that is excited at different places in the longitudinal direction of the same wavelength conversion fiber to be treated as light emission at the same point on the image, causing image degradation. It is possible to increase the brightness without the need.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-sensitivity high-speed neutron fluorescent converter which can be used as a high-speed neutron radiography fluorescent converter used as a nondestructive inspection technique.

[0002]

2. Description of the Related Art Conventional fluorescent converters for high-speed neutron radiography generally emit light using a recoil proton generated by a reaction between high-speed neutrons and hydrogen. And Z with high luminous efficiency
A plate obtained by mixing nS (Ag) and molding into a plate shape has been used (for example, see JP-A-6-167598).

[0003]

In a conventional fluorescent converter for fast neutron radiography, in order to increase the amount of light emission, a reaction between fast neutrons and hydrogen in a resin in a fast neutron passage in the converter. The converter needed to be thicker to increase the volume and was chosen to be transparent to the emission from the phosphor relative to the resin. However, as the thickness of the converter increases, the phosphor content increases, and the scattering of light increases the opacity of the converter. Has a problem that it tends to be saturated.

[0004]

In order to solve the above-mentioned problems, in the present invention, a converter which reacts with fast neutrons to emit fluorescence and a portion which propagates the fluorescence to an observation surface are separated from each other. Even when the thickness is increased, the light emission inside the converter can be transmitted to the observation surface with little loss, so that the light emission amount can be increased.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a high-sensitivity high-speed neutron fluorescence converter according to the present invention, a fiber sheet in which wavelength conversion fibers having a light wavelength conversion function are arranged and bonded is alternately provided with a converter sheet which emits fluorescence for incident high-speed neutrons. After being closely adhered and laminated, they are fixed and shielded from light except for the end face on the observation side.

[0006] A part of the fluorescent light generated in the converter sheet enters the adjacent fiber sheet, and excites a scintillation die in a core fiber in the wavelength conversion fiber to emit fluorescent light. This fluorescence propagates through the wavelength conversion fiber to the end face under conditions determined by the aperture ratio of the used wavelength conversion fiber.

[0007] Since the wavelength conversion fibers are arranged in parallel to the direction of entry of high-speed neutrons, each one of the wavelength conversion fibers corresponds to each point of the image obtained by the high-sensitivity high-speed neutron fluorescence converter. Fluorescence excited at different locations in the longitudinal direction of the wavelength conversion fiber is also treated as emission at the same point on the image. Therefore, the luminance can be increased without causing the image to deteriorate. Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0008]

FIG. 1 conceptually shows a partially enlarged view of a high-sensitivity high-speed neutron fluorescence converter according to the present invention. A wavelength conversion fiber 1 is composed of a core fiber 2 and a cladding material 3 at a central portion. The converter sheet 4 is in close contact with the upper part. A reflective material 5 is attached to the end faces on the fast neutron incidence side.
In this example, polystyrene was used as the core fiber material and polymethyl methacrylate was used as the cladding material.

According to the high-sensitivity high-speed neutron fluorescent converter of the present invention having the above-described structure, when high-speed neutrons 6 enter the converter sheet 4, they emit fluorescent light 7. Is excited to generate light emission 8.
Part of this light emission propagates through the wavelength conversion fiber as it is, and is emitted from the observation side end face opposite to the fast neutron incidence side. A part of the light emitted in the direction opposite to the observation side end face is reversed in direction by the reflective material 5, propagates through the wavelength conversion fiber, and is emitted from the observation side end face.

FIG. 2 shows a high-sensitivity, high-speed neutron fluorescence converter main body assembled from the one shown in FIG. Converter sheet 4 has a thickness of 0.1 to 0.5.
mm, the width of which is equivalent to the thickness of the high-sensitivity high-speed neutron fluorescent converter, and the length of which is equal to the width of the high-sensitivity high-speed neutron fluorescent converter.

The width of the fiber sheet in which the wavelength conversion fibers are arranged and adhered corresponds to the thickness of the high-sensitivity high-speed neutron fluorescent converter, and the length thereof corresponds to the width of the high-sensitivity high-speed neutron fluorescent converter. It is processed into a sheet having.

The cross section of the wavelength conversion fiber is preferably rectangular as shown in FIG. 3 from the viewpoint of the adhesion between the fibers and the converter sheet, but a circular cross section may be used. At this time, the mutual fibers may be fixed with a transparent adhesive or with a transparent adhesive tape.

The fiber sheet and the converter sheet are vertically stacked to form a high-sensitivity high-speed neutron fluorescence converter main body. The converter sheet and the fiber sheet may be bonded with a transparent adhesive, but may be formed with a frame made of Teflon (R) or the like on the outside, and may be closely contacted and fixed so as to hold down. A reflective material is attached to the end face on the fast neutron incidence side, or a reflective surface is formed by vapor deposition or the like.

[0014]

As described above, according to the present invention,
Even if the converter is thickened, the fluorescence can be taken out well, so that the detection sensitivity to high-speed neutrons can be greatly increased and high brightness can be achieved.

That is, according to the present invention, since the wavelength conversion fibers are arranged in parallel to the direction of entry of the fast neutrons, one of the wavelength conversion fibers is used for each of the images obtained by the high-sensitivity fast neutron fluorescence converter. Is equivalent to a point,
Fluorescence excited at different locations in the longitudinal direction of the same wavelength conversion fiber is also treated as light emission at the same point on the image, so that the brightness can be increased without causing image degradation.

According to the present invention, as shown in FIG. 3, by increasing the thickness of the high-sensitivity high-speed neutron fluorescence converter, the high-speed neutron sensitivity can be further increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing details of a single cell of a sensitive fast neutron fluorescence converter.

FIG. 2 is a diagram illustrating details of a high-sensitivity fast neutron fluorescence converter.

FIG. 3 is an enlarged view of a portion surrounded by a circle in FIG. 2; (The portion of the reflective material illustrated in FIG. 2 is omitted to make it easier to see the state of the cross section.)

FIG. 4 is a graph showing the relationship between the thickness of a high sensitivity fast neutron fluorescence converter and the fast neutron beam sensitivity ratio.

[Explanation of symbols]

 1: Wavelength conversion fiber 2: Core fiber 3: Cladding material 4: Converter sheet 5: Reflective material 6: High-speed neutron beam 7: Fluorescence 8: Emission 9: High-sensitivity high-speed neutron fluorescence converter

Claims (5)

[Claims] 1. A fiber sheet in which wavelength conversion fibers having a light wavelength conversion function are arranged and adhered, and a converter sheet which emits fluorescence by high-speed neutron incidence are alternately closely adhered and laminated, and then fixed and light is shielded except for an end face on the observation side. A high-sensitivity, high-speed neutron fluorescence converter characterized by: 2. The fiber sheet has a length of 1 to 5 cm.
2. The high-sensitivity high-speed neutron converter according to claim 1, wherein the high-speed neutron converter comprises a wavelength conversion fiber. 3. The high-sensitivity high-speed neutron fluorescence converter according to claim 1, wherein the high-speed neutron incidence side end face of the wavelength conversion fiber has a reflection layer. 4. A method according to claim 1, wherein said converter sheet has a thickness of 0.1 to 0.1.
2. A sheet having a size of 0.5 mm.
High sensitivity fast neutron fluorescence converter as described. 5. The converter sheet, wherein the substance sensitive to fast neutrons is a hydrogen-containing resin, and the substance sensitive to recoil protons generated by the reaction between fast neutrons and hydrogen is ZnS.
2. The high-sensitivity high-speed neutron fluorescence converter according to claim 1, wherein (Ag) is used.