JPH0533082U - Radiation detection optical transmission device - Google Patents

Abstract

(57) [Abstract] [Purpose] An optical transmission fiber can be easily attached to and detached from a radiation-sensitive emission wavelength converter. [Structure] An optical connector 9 is used instead of a microlens for connecting the end of the fluorescent plastic optical fiber 5 in the radiation-sensitive emission wavelength converter 1 and the optical transmission fiber 10, and a plurality of or one optical connector 9 The end of the fluorescent plastic optical fiber 5 and one optical transmission fiber 10 are connected.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a radioactivity detection optical transmission device used in a facility that handles radioactive substances.

[0002]

[Prior Art]

 Conventionally, in facilities that handle radioactive substances, such as nuclear power generation, radiation medicine, nondestructive inspection, and synchrotron radiation facilities, one of the things that measures the presence or absence of radiation and its extent is to convert the extent of radiation into an optical signal and There was a device that measured the radiation level based on the optical signal level.

This device is used as an inexpensive device that easily realizes the measurement when the radiation level cannot be converted into an electric signal in an electromagnetic environment or when the radiation measurement is performed in water. A radiation sensitive emission wavelength converter is placed at the end of the optical transmission fiber, and the optical signal obtained by this radiation sensitive emission wavelength converter is measured through the optical transmission fiber with an optical power meter as a counting unit. It has become.

The above-mentioned radiation-sensitive light emission wavelength converter is contained in a container of a translucent optical member and a reflective material, and emits light upon incidence of radiation, and a fluorescent plastic optical fiber which emits light upon receiving light from this scintillator. Is integrally configured by a casing composed of a reflection material and a light shielding member, and a microlens is attached between the end of the fluorescent plastic optical fiber and the end of the optical transmission fiber. It was connected.

This microlens is accompanied by absorption and scattering of ultraviolet light, as well as manufacturing difficulties such as adjustment of the optical axis and optical transmission loss. The structure is completely fixed to the optical fiber and the radiation-sensitive emission wavelength converter, and it was not possible to remove the radiation-sensitive emission wavelength converter from the optical transmission fiber.

However, depending on the conditions of use, the optical transmission fiber must be passed through a narrow space or through a thin wall, or a weak radiation-sensitive emission wavelength converter with a low radiation dose equivalent rate such as natural radiation level. In some cases, such as when the output optical signal of the above has to be transmitted over a long distance, the radiation-sensitive emission wavelength converter and the optical transmission fiber could not be attached and detached, which sometimes made measurement impossible. In addition, the microlenses described above have a problem in terms of vibration resistance, such that the transmission efficiency is easily reduced due to the shift of the optical axis due to a shock.

[0007]

[Problems to be solved by the device]

 As described above, the conventional radiation-sensitive emission wavelength converter may not be able to be measured depending on the usage conditions, and it is used for the connection between the radiation-sensitive emission wavelength converter and the optical transmission fiber. There was a problem that it was difficult to handle, such as a problem with microlenses in terms of vibration resistance.

The present invention has been made in view of the above circumstances, and an object thereof is to use a radiation-sensitive emission wavelength converter and an optical converter without using a microlens and without lowering transmission efficiency. An object of the present invention is to provide a radiation detection optical transmission device having a structure in which a transmission fiber can be easily attached and detached.

[0009]

[Means and Actions for Solving the Problems]

 That is, the present invention uses an optical connector instead of a microlens to connect the end of the fluorescent plastic optical fiber in the radiation-sensitive emission wavelength converter to the optical transmission fiber. Since the end portion of the plastic optical fiber is connected to one optical transmission fiber, it can be easily attached and detached, and there is no problem in terms of vibration resistance.

[0010]

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

FIG. 1 shows the structure, and the range indicated by 1 is a radiation-sensitive emission wavelength converter. The radiation-sensitive emission wavelength converter 1 is mainly composed of a scintillator 2 and a fluorescent plastic optical fiber 5.

In the scintillator 2, for example, the light reflection plates 3, 3 are provided on the upper and lower bottom surfaces of the cylindrical scintillator 2, and the translucent optical member 4 made of, for example, quartz glass encloses the scintillator 2 on the peripheral surface of the side wall. Thus, one or more fluorescent plastic optical fibers 5 are arranged so as to wind around the side wall surface of the translucent optical member 4. This figure shows an example in which two fluorescent plastic optical fibers 5 are arranged.

Although the scintillator 2 is described here as a cylindrical shape, the scintillator 2 is not limited to this and may be, for example, a flat shape. When the scintillator 2 has a flat plate shape, the same effect can be obtained by using two scintillators 2 and sandwiching a plurality of or one fluorescent plastic optical fiber 5.

When the scintillator 2 has an elongated cylindrical shape, the central axis portion of the scintillator 2 is perforated according to the diameter and length of the fluorescent plastic optical fiber 5, and the fluorescent plastic is provided in the hole portion. A structure in which the optical fiber 5 is inserted can be considered.

Therefore, a casing 6 is provided so as to cover the radiation-sensitive emission wavelength converter 1, and an optical connector for collectively connecting one end of the fluorescent plastic optical fiber 5 to the upper end surface of the casing 6. 9 is attached.

The optical connector 9 is the same as one generally used for general optical communication, and is used for connecting the optical transmission fiber 10 and the fluorescent plastic optical fiber 5, so that the optical connector 9 is inserted or twisted. By the inserting operation, the attachment to the casing 6 and the connection with the fluorescent plastic optical fiber 5 can be easily performed.

That is, the optical connector 9 has a large optical transmission loss and is not suitable for optical transmission. In order to avoid transmitting the individual signals by drawing the fluorescent plastic optical fiber 5 as it is to the outside of the casing 6, fluorescent light is transmitted. The optical plastic fiber 5 and the optical transmission fiber 10 are connected to each other.

When a plurality of fluorescent plastic optical fibers 5 are connected to the optical connector 9, the optical connector 9 converges the optical signal from each fluorescent plastic optical fiber 5 and transmits the optical signal to the optical transmission fiber 10.

By using the optical connector 9 as described above, the optical transmission fiber 10 and the fluorescent plastic optical fiber 5 in the casing 6 can be connected easily and detachably.

At the same time, by selecting the optical connector 9 to which the optical transmission fibers 10 having different lengths are connected and connecting it with the fluorescent plastic optical fiber 5 in the casing 6, it is possible to reduce the distance from the long distance. It becomes possible to freely select the optical transmission fiber 10 according to the distance up to a short distance.

As the optical connector 9, a commercially available optical connector for plastic optical fiber can be used as it is. The material of the optical transmission fiber 10 may be plastic or quartz. When used in water, a waterproof coating 13 is attached to cover the entire casing 6. The measurement operation in the above configuration will be described.

FIG. 2 shows an outline of the radiation detection process. When the scintillator 2 is irradiated with radiation, the scintillator 2 emits fluorescence. This fluorescence enters the side of the fluorescent plastic optical fiber 5, that is, the clad 22 with a vertical direction or at an inclination angle, excites the phosphor in the core 21 to emit light, and collects the emitted light. It emits light and transmits it to the end of the fiber for optical output.

Therefore, the emitted light with respect to the incident light in the fluorescent plastic optical fiber 5 is converted into light having a wavelength that is easily transmitted, and the output density is relatively increased.

FIG. 3 illustrates an emission wavelength spectrum of the scintillator 2. When γ-rays are incident on the Nal (Tl) scintillator 2 having an emission wavelength spectrum as shown in the figure, light is emitted with a wavelength of 410 nm as a peak.

The following FIG. 4 illustrates the emission wavelength spectrum of the fluorescent plastic optical fiber 5. When light having a spectrum having a peak wavelength of 410 nm of the scintillator 2 is incident, the core 21 of the fluorescent plastic optical fiber 5 is excited and emits light having a peak wavelength of 520 nm.

The radiation detection optical transmission device equipped with the optical connector 9 is extremely easy to manufacture, and the radiation-sensitive emission wavelength converter 1 and the optical transmission fiber 10 can be easily attached and detached, and electrical noise can be eliminated. It is possible to perform signal transmission without amplifying.

As a result, the optical transmission fiber 10 is once detached from the radiation-sensitive emission wavelength converter 1, passed through a narrow space or a thin through-hole in the wall, and then attached again to the radiation-sensitive emission wavelength converter 1, thereby making It is possible to largely separate the counting unit that easily picks up environmental noise such as from the measurement target. With such a configuration, it becomes possible to easily realize radiation measurement in an electromagnetic environment or in water, which was difficult in the past.

Since the optical transmission fiber 10 has a large transmission loss of the fluorescent plastic optical fiber 5 as described above and is not suitable for optical transmission, it is connected via the optical connector 9, so that it is inexpensive if the distance is short. Such a plastic optical fiber may be a silica-based optical fiber although it is expensive for a long distance.

FIG. 5 is a diagram illustrating the relationship between the wavelength of the plastic optical fiber and the transmission loss. The transmission loss is as high as 400 dB / km to 500 dB / km near the wavelength of 410 nm, but the transmission loss is about 150 dB / km near the emission wavelength of 520 nm of the fluorescent plastic optical fiber 5. It shows that signal transmission can be realized in a small wavelength range.

Therefore, it is understood that the emission wavelength of the fluorescent plastic optical fiber 5 is more suitable for signal transmission than the optical signal itself as the radiation intensity detection signal emitted by the scintillator 2.

FIG. 6 is a diagram illustrating the relationship between the wavelength and the transmission loss of a silica optical fiber. In the vicinity of the emission wavelength of 520 nm of the fluorescent plastic optical fiber 5, the transmission loss is about 10 dB / km, which shows that signal transmission can be realized in a wavelength range with very little transmission loss. Therefore, it can be seen that it is more suitable for long-distance signal transmission than the plastic optical fiber.

The use of an optical fiber as a signal transmission system does not pick up electrical noise unlike an electric signal cable, and the output of the radiation-sensitive emission wavelength converter 1 is an optical signal. This is advantageous in that it does not require a power source for signal amplification or transmission. Next, a prototype of a radiation detection optical transmission device using the radiation-sensitive emission wavelength converter 1 having the structure shown in FIG. 1 will be described.

FIG. 7 shows a device configuration of the measurement test, and FIG. 7A shows an external configuration thereof. However, the other end of the optical transmission fiber 10 made of, for example, a silica-based optical fiber having a length of 10 m, which is not connected to the radiation-sensitive emission wavelength converter 1, is connected to the optical power meter 23.

The optical power meter 23 converts an optical signal transmitted through the optical transmission fiber 10 into an electric signal and outputs the power level (unit [nW (nanowatt)]) for display.

FIG. 7B mainly shows a circuit configuration of the optical power meter 23. The optical power meter 23 is a photoelectric conversion unit 24 that converts an optical signal transmitted from the optical transmission fiber 10 into an electric signal, and calculates the power value of the electric signal obtained by the photoelectric conversion unit 24 by signal processing. It is composed of a processing unit 25 for digitizing the power value and a display unit 26 for displaying and outputting the power value obtained by the processing unit 25.

FIG. 8 shows the measurement results obtained by the equipment shown in FIG. 7, which shows that the radiation input [mSv / h] k to the radiation-sensitive emission wavelength converter 1 shown on the horizontal axis of the figure increases. , It was found that an output [nW] proportional to the output end of the radiation-sensitive emission wavelength converter on the vertical axis of the figure at a length of 10 m was obtained, and by setting the correlation, the radiation dose equivalent rate detector can be obtained. It can be confirmed that it is available.

[0037]

[Effect of the device]

 As described in detail above, according to the present invention, an optical connector, rather than a microlens, is used to connect the end of the fluorescent plastic optical fiber in the radiation-sensitive emission wavelength converter to the optical transmission fiber. Alternatively, since the end of one fluorescent plastic optical fiber is connected to one optical transmission fiber, it can be easily attached and detached, and there is no problem in terms of vibration resistance. A device can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing the structure of a radiation-sensitive emission wavelength converter according to an embodiment of the present invention.

FIG. 2 is a diagram showing an outline of a radiation detection process using the scintillator and the fluorescent plastic optical fiber of FIG.

FIG. 3 is a diagram illustrating an emission wavelength spectrum of the scintillator of FIG.

FIG. 4 is a diagram illustrating an emission wavelength spectrum of the fluorescent plastic optical fiber of FIG.

FIG. 5 is a diagram illustrating the relationship between the wavelength of a plastic optical fiber and the transmission loss.

FIG. 6 is a diagram illustrating a relationship between a wavelength of a silica-based optical fiber and transmission loss.

FIG. 7 is a diagram showing a device configuration of a measurement test using the radiation-sensitive emission wavelength converter of FIG.

FIG. 8 is a diagram showing a measurement result by the device shown in FIG. 7.

[Explanation of symbols]

1 ... Radiation sensitive emission wavelength converter, 2 ... Scintillator, 3
... light reflecting plate, 4 ... translucent optical member, 5 ... fluorescent plastic optical fiber, 6 ... casing, 9 ... optical connector, 1
0 ... Optical transmission fiber, 13 ... Waterproof coating, 21 ... Core, 2
2 ... Clad, 23 ... Optical power meter, 24 ... Photoelectric conversion part, 25 ... Processing part, 26 ... Indicator.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masanori Takebe 26-23, Aoyama, Taihaku-ku, Sendai City, Miyagi Prefecture (72) Inventor Yoshihiro Atsumi 2-4-1, Shiba Park, Minato-ku, Tokyo Mitsubishi Hara Inside Riki Kogyo Co., Ltd. (72) Inventor Katsumi Urayama 1-297 Kitabukuro-cho, Omiya-shi, Saitama Inside Omiya Research Center, Mitsubishi Nuclear Industry Co., Ltd. (72) Inventor Michio Wakahara 1-297 Kitabukuro-cho, Omiya-shi, Saitama Omiya Research Institute Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A scintillator which is contained in a container of a translucent optical member and a reflective material and emits light when radiation enters, a fluorescent plastic optical fiber which emits light when receiving light from the scintillator, and the fluorescent plastic optical fiber An optical connector connected to one end, and an optical transmission fiber connected to one end of the fluorescent plastic optical fiber through the optical connector and transmitting light emitted from the fluorescent plastic optical fiber to the outside. A radiation detection optical transmission device characterized in that