JPS61201183A - Scintillation detector - Google Patents

Abstract

PURPOSE:To attempt uniform detection efficiency on the detecting surface by arranging so that he scintillators are different as to at least one of the plate thickness and material depending on the site of the detecting surface. CONSTITUTION:A casing 14 of a scintillation detector is box-shaped and has its one face opened as the detection surface. Starting from the surface, a light barrier film 11, four scintillators 12a, 12b, 12c and 12d with respectively different thicknesses and a light guide 13 are placed in intimate contact with one another and for closing this detecting surface. Photomultiplier 15a, 15b are arranged in opposition to the light guide 13 at the back side of the casing 14. The scintillators 12b, 12c arranged towards the center of the detecting surface are of reduced thickness while the scintillators 12a, 12d arranged towards the ends of the detecting surface are of larger thickness. Hence the light emitted at near the center of the detecting surface has a transmission efficiency larger because of the closer position of the scintillators to the photomultiplier. Such characteristics are corrected by reducing the luminous quantity by reducing the thicknesses of the scintillators 12b, 12c. Towards the ends, correction is made so as to enhance the luminous quantity to render the detection efficiency uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a scintillation detector for detecting radiation, and particularly to an improvement in the structure of a scintillator.

[Technical background of the invention and its problems]

As shown in FIG. 5, the scintillation detector is composed of a light-shielding film (2), a scintillator (2), a light guide (2), a case (A), and photomultiples (5a) and (5b).

Conventionally, scintillators (2), which emit light when radiation is incident and lose energy, have a plate-like structure with a uniform thickness relative to the detection surface.

Therefore, the light emitted near the photomultiples (5a) and (5b) has high light transmission efficiency because it is close to the photomultiplexes, and has high geometrical efficiency against radiation because it is located in the center of the detector. The detection efficiency distribution characteristics shown in FIG. 6 are shown.

In this way, even if the material and thickness of the scintillator are uniform over the entire detection surface, the photomultiplier (5a
), (5b) differs depending on the position of the detection surface, and the geometric efficiency of the radiation incidence surface depends on the location, so the detection efficiency on the detection surface is large at the center and at the edges. [Objective of the Invention] It is an object of the present invention to provide a scintillation detector in which the detection efficiency on the detection surface is uniform or has a specific distribution.

[Summary of the invention]

In a scintillation detector, the present invention makes the detection efficiency on the detection surface uniform or uniform by making the thickness of the scintillator different depending on the location on the detection surface, making the material different, or making both the thickness and the material different. This makes it possible to create a specific distribution consisting of:

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

A scintillation detector according to an embodiment of the present invention is shown in FIG. The case (14) is box-shaped and one side thereof is open as a detection surface. In order from the surface to block this detection surface, there is a light shielding film (11), four scintillators (12a), (12b), (12c), each having a different thickness.
(Three light guides (13) made of transparent resin, for example, are arranged in close contact with each other.) Opposing the light guides (13) are photomultiples (15a), (
15b) is arranged on the back side of the case (14).

A scintillator (12a) placed near the edge of the detection surface
), (12d) has a large thickness, and the scintillator (12b) is placed near the center of the detection surface.
(12c) has a small thickness.

Now, when radiation enters a scintillator, its energy is converted into light, and the amount of light at that time depends on the amount of energy lost by the radiation. The amount of light emitted also depends on the thickness of the scintillator. In the scintillation detector according to one embodiment of the present invention shown in FIG. 1, scintillators (12b) and (1
The scintillators 2e) are thin, and the scintillators (12a) and (12d) placed near the edges of the detection surface are thick, so that the light emitted near the center of the detection surface is photosensitive. By reducing the thickness of the scintillator, we can reduce the amount of light emitted by reducing the thickness of the scintillator. In addition, by increasing the thickness of the scintillator, the amount of light emitted is increased by increasing the thickness of the scintillator. Due to this effect, the detection efficiency on the detection surface can be made almost uniform by positively correcting it.

Next, FIG. 2 shows another embodiment of the scintillation detector according to the present invention. As shown in Figure 2.

The scintillator (22) is formed into a single plate that is thick at both ends of the detection surface, gradually decreases in thickness, and becomes thinner at the center.

Then, it is placed with its flat surface facing the side that contacts the light shielding film (11). Therefore, the surface of the light guide (23) in contact with the scintillator (22) is formed to match the curved surface of the scintillator (22). In a scintillation detector configured in this way, by reducing the amount of light emission and the probability of light emission in the center, the light transmission efficiency and the geometric efficiency against radiation are compensated, and the entire detection surface becomes as shown in Figure 3. Uniform characteristics.

Note that the present invention is not limited to the two embodiments described above, and can be implemented with the following modifications.

[a] The configuration of the scintillator whose thickness differs from place to place with respect to the detection surface can be appropriately determined depending on whether the detection efficiency on the detection surface is uniform or has a specific distribution. That is, in the example of FIG. 4(a).

There are four scintillators with different thicknesses, a thin one (22b) and (22c) in the center, and a thick one (22c) at both ends.
22a) and (22d), and a light guide (3a) with a uniform thickness divided for each scintillator.
) , (3b) v (3c) - (3d) are arranged, and the surface in contact with the light shielding film of the scintillator has a step. In addition, in the example shown in FIG. 4(b), scintillators (32a
), (32b) from one end side of the detection surface (32a).

(32b), (32a), and (32b), in which thick and thin pieces are arranged alternately. Furthermore, in the example shown in FIG. 4(c), the number of stacked scintillators (42) of the same thickness is changed so that two scintillators are stacked at both ends and one scintillator is stacked at the center. of uniform thickness divided into
3a), (3b), (3c), and (3d), and a light guide (23) having the thickness of one scintillator (42) is placed as a spacer for the single-layer scintillator in the center. This is the configuration inserted as .

(b) Instead of varying the thickness of the scintillator with respect to the detection surface, the scintillator may be constructed by arranging the scintillator with different materials at different locations on the detection surface.

A scintillator has characteristics in which the amount of light emitted and the absorption coefficient of radiation and light differ depending on the material. therefore,
By arranging scintillators made of various materials on the detection surface, the same effect as when arranging scintillators with different plate thicknesses can be obtained.

(c) A plate-shaped scintillator may be used in which both the thickness and the material of the scintillator differ depending on the location on the detection surface.

This allows the detection efficiency on the detection surface to be made uniform or to have a specific distribution.

(The shape of the dl light guide, the arrangement and number of photomultiples are not limited to those illustrated.

〔Effect of the invention〕

As detailed above, according to the present invention, in a scintillation detector, the thickness of the scintillator is made different depending on the location on the detection surface, the material is made different, or both the thickness and the material are made different. This makes it possible to make the detection efficiency on the detection surface uniform or have a specific distribution depending on the purpose.

Therefore, the scintillation detector according to the invention comprises:
For example, it can be used in a device that measures surface contamination of human bodies or articles, and can evenly measure surface contamination of objects to be measured. In addition, even when the distance between the object to be measured and the detector cannot be kept constant, or when multiple detectors are used and there is a joint between the detection surfaces, it is possible to adjust the detection efficiency distribution of the detection surface to the desired distribution. Therefore, the surface contamination of the entire object to be measured can be accurately measured under the same measurement conditions.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a scintillation detector according to one embodiment of the present invention, FIG. 2 is a sectional view showing a scintillation detector according to another embodiment of the present invention, and FIG. 3 is a sectional view of the scintillation detector of FIG. Graph showing detection characteristics on the detection surface, 4th
Figures (a), (b), and (c) are cross-sectional views showing different modifications of the structure of the scintillator according to the present invention, respectively;
FIG. 5 is a sectional view showing a conventional scintillation detector.
FIG. 6 is a graph showing the detection characteristics of the scintillation detector of FIG. 5 on the detection surface. 11... Light shielding films 12a, 12b, 12c, 12d...Scintillators 13 each having a different thickness...Light guide 14.
...Case 15a, 15b...Photomaru 2
2...Scintillator 23...Light guide

Claims (1)

[Claims] One side of the box-shaped case is open as a detection surface, and this detection surface is closed and a light-shielding film, a scintillator, and a light guide are arranged in order from the surface. 1. A scintillation detector disposed on the side, wherein the scintillator has a plate-like structure in which at least one of plate thickness and material differs depending on the location of the detection surface.