JPS6130222Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plastic scintillation detector.

In general, plastic scintillators can be easily manufactured in relatively large areas. For this reason, plastic scintillation detectors are used for radiation measurements on large areas, such as the human body, the surface of objects, or clothing.

By the way, this plastic scintillation detector consists of a plate-shaped plastic scintillator, a flat light guide that is placed in close contact with one plane of the plastic scintillator and transmits light from that plane, and a light-receiving surface that is closely attached to the surface of the light guide. The detection section is constituted by a member that shields the optical system from the photomultiplier tube and the plate-shaped plastic scintillator to the photomultiplier tube from external light. Since the photomultiplier tube has a cylindrical shape and a light-receiving surface is formed at its tip, the external appearance of the detection section has a depth equal to the longitudinal dimension of the photomultiplier tube.

This plastic scintillation detector is used as a human body surface contamination measurement device.
Suppose that it is applied to Since plastic scintillation detectors 1 will be placed at the front and rear of the human body, the width W of each human body surface contamination measurement device is the distance between the surfaces of both plastic scintillation detectors and the plastic scintillation detection. It is the sum of the value obtained by doubling the depth of the vessel. Therefore, if multiple human body surface contamination measurement devices are connected and arranged in the width direction, there will be no problem as long as there is a large space, but if a large number of human body surface contamination measurement devices are stored in a limited space, human body surface contamination may be a problem. It is necessary to narrow the width of the measuring device.

Based on the above, an object of the present application is to obtain a plate-shaped plastic scintillation detector with a small depth.

The outline of how to achieve this purpose is to place a photomultiplier tube horizontally without making it almost perpendicular to the surface of the plastic scintillator, and use a light guide to multiply the light on the surface of the plastic scintillator. Make the light incident on the light-receiving surface of the tube.

With this configuration, the depth of the plastic scintillation detector can be made slightly larger than the sum of the diameter of the photomultiplier tube and the thickness of the plastic scintillator. In addition, since the light from the entire surface of the plastic scintillator is transmitted to the light-receiving surface of the photomultiplier tube using a light guide, it does not detect only direct light like the conventional method, so there is little difference in detection sensitivity depending on the position of the detection surface. Approximately average output characteristics can be obtained no matter where on the entire surface the radiation is incident.

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

In FIG. 2 showing the detection section, a is a plan view of the detection section, and b is a sectional view of the detection section taken along line A-A.
12 is a plate-shaped plastic scintillator that emits light upon incidence of radiation. A light shielding film 13 for blocking external light is disposed on the lower surface. Reference numeral 14 denotes a light guide that transmits light using an air layer or a transparent member.The lower surface is brought into close contact with the upper surface of the plate-shaped plastic scintillator to form an entrance window 14a, and the light from the entrance window is transmitted to both ends, and the upper surface Recess 14 formed in
It is discharged from the outlet side 14c of the vertical wall surface of b. The depth of this recess is a predetermined value. Reference numeral 15 denotes a photomultiplier tube, which is disposed horizontally within the concave portion of the light guide 14 with its light-receiving surface in close contact with the exit side thereof. The depth of the recess is approximately equal to the diameter of the photomultiplier tube 15 so that the photomultiplier tube 15 does not protrude from the recess of the light guide 14. 16 is
It is a container, the opening of which is covered with the light-shielding film, and a plate-shaped plastic scintillator and a photomultiplier tube light guide are housed inside.

To describe the function and effect of the detection section configured in this way, the plate-shaped plastic scintillator 12, light guide 14, and photomultiplier tube 15 are completely isolated from external light by the light-shielding film 13 and the container 16.
In this state, when radiation passes through the light-shielding film with low radiation absorption and enters the plate-shaped plastic scintillator, a light emission phenomenon occurs at the point of incidence.
The light generated there passes through the light guide 14 to the photomultiplier tube 1
5 is guided to the light receiving surface. The photomultiplier tube converts an electrical signal corresponding to the amount of radiation incident on the light-receiving surface of the plastic scintillator 12 into an output from the detection section. Furthermore, since the photomultiplier tube 15 housed in the recess of the light guide does not protrude from this recess, the depth of the detection section is approximately the same as the diameter of the photomultiplier tube, which is 1/1/2 compared to the conventional one.
It can be made to about 3 to 1/2 the length. Furthermore, since the light emitted within the wide-area plastic scintillator plate is guided to the light guide and incident on the light receiving surface of the photomultiplier tube, no matter where on the detection surface of the plate plastic scintillator the radiation is incident. The light can be reliably transmitted to the light-receiving surface of the photomultiplier tube. Therefore, compared to a conventional structure that handles only direct light, the detection distribution of the plate-shaped plastic scintillator in the present invention is almost uniform.

Next, the electric circuit of the detection section is shown in FIG. A photomultiplier tube 15 disposed on the output side of the light guide 14 into which light from the plate-shaped plastic scintillator 12 is input.
Depending on the surface area of the plate-shaped plastic scintillator 12, there may be one or more scintillators. In the figure, 2
Use items. The output of each photomultiplier tube is fed to an amplifier 17.
and are each amplified and connected to the input side of the coincidence counting circuit 18. Then, only when both photomultiplier tubes output simultaneously, the signal appearing on the output side of the coincidence circuit is counted by the counter 19, and the radiation incident on the surface of the plate-shaped plastic scintillator is calculated from the counted value. Measure.

FIG. 4 shows a case where the plate-shaped plastic scintillator detector of the present invention is applied to a human body surface contamination measuring device. The depth of the detection part is smaller than that of conventional ones.
Since the dimension value is about 1/2 to 1/4 times larger, the width W is used for human body surface contamination measurement equipment that can measure the front and back of the human body simultaneously.
The space is now 1/2 to 1/3 times narrower than before, making it possible to store three machines in a space that could previously only accommodate two. It is effective in terms of effective use of space.

As described above, in the present invention, a photomultiplier tube is placed horizontally on the surface of a plate-shaped plastic scintillator, and the surface of the plate-shaped plastic scintillator and the light-receiving surface of the photomultiplier tube are optically coupled by a light guide.
The depth of the plastic scintillation detector can be reduced to approximately the diameter of a photomultiplier tube, and by using a light guide, the detection sensitivity can be made constant at any point on the surface of the plastic scintillator. It is possible to obtain the averaged detection distribution characteristics.

Therefore, if the present invention is used in a human body surface contamination measurement device, significant effects can be achieved in terms of measurement accuracy and installation location.

In one embodiment of the present invention, the light guide is described as having a concave portion formed in the center, but the light guide is not limited to this, and may have a convex portion formed in the center.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an overview of a detector of a conventional human body surface contamination measuring device, FIG. 2 is a diagram showing the configuration of a plate-shaped plastic scintillation detector of the present application, and FIG.
The figure is an electric circuit diagram of a plate-shaped plastic scintillation detector, and FIG. 4 is an overview diagram of the detector of a human body surface contamination measuring device equipped with the plate-shaped plastic scintillation detector of the present application. 12...Plate plastic scintillator, 13
... Light shielding film, 14 ... Light guide, 15 ... Photomultiplier tube, 16 ... Container, 17 ... Amplifier, 18 ...
...coincidence circuit, 19...counter.

Claims (1)

[Scope of utility model registration request] a plate-shaped plastic scintillator, a photomultiplier tube having a light-receiving surface at an end thereof, a recess for accommodating the photomultiplier tube in a horizontal state, an entrance window that guides the light emission of the plate-shaped plastic scintillator to a lower surface, and an inside of the recess. a light guide in which an exit for emitting light from the entrance window is formed on a vertical wall surface, and a light shielding member for shielding an optical system from the plate-shaped plastic scintillator to the photomultiplier tube from external light. The plastic scintillation detector is characterized in that the photomultiplier tube is disposed laterally within the recess of the light guide with its light-receiving surface aligned with the exit of the recess.