KR101060576B1 - Plastic scintillator and its manufacturing method - Google Patents

Abstract

The present invention relates to a plastic scintillator and a method of manufacturing the same, and simultaneously extrudes both an optical fiber, a scintillation cell and a reflective film, thereby greatly reducing the time and cost for the production of the plastic scintillator, and to produce the plastic scintillator in a desired dimension and shape. There is.

Scintillator, optical fiber, extrusion

Description

Plastic scintillator and manufacturing method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic scintillator and a method of manufacturing the same, and to a plastic scintillator and a method of manufacturing the same, which greatly reduce manufacturing time and cost by extrusion molding an optical fiber to be positioned at the center of the scintillation cell.

The plastic scintillator used for the detector of particles with high energy is a scintillator cell for converting the incident particles into light, and an optical fiber for capturing light from the scintillation cell inserted into the scintillator cell and transmitting it to the outside. It is composed.

As an example of a method of manufacturing such plastic scintillator, a manufacturing method using a polymerization method using an aluminum mold, 2,5-diphenyl oxazole (PPO) as a primary fluorescent additive per 100 g of the monomer styrene (STYRENE) solvent in the aluminum mold 1g, 0.05 g of 1,4-bis- [5-phenyl-2-oxazole] benzene (POPOP, 1,4-bis (5-phenyloxazol-2-yl) benzene) as a secondary fluorescent additive was added and mixed. In order to mix the styrene and the additive well, put it in a drier and leave it at about 100 ° C. for about 1 hour and then heat it to about 120 ° C., which is a temperature at which the polymerization reaction takes place. The polymerization takes place within a few hours, but the unreacted monomer styrene changes color and degrades the properties of the plastic scintillator, so that excess monomer styrene is heated for about 150 hours to react or evaporate. If the temperature is rapidly cooled after the polymerization reaction, a stress is generated in the polystyrene, and thus the plastic scintillator has a bad effect on the characteristics of the plastic scintillator. The plastic scintillator is removed from the mold and processed into a required shape using a milling machine, and the surface is polished using a high speed rotor made of coarse and soft cloth.

This polymerization takes about 6-7 days to polymerize, which takes a long time, requires high temperature work for polymerization, and secondary processing of the plastic scintillator from the mold to a desired size and shape (milling, polishing, etc.). This has been a major problem that is time consuming and costly.

In the above-described conventional scintillator manufacturing method, only the scintillation cell is manufactured and the optical fiber is not manufactured together with the scintillation cell. Therefore, the 'U' groove for mechanically arranging the optical fiber in the scintillation cell is mechanically processed on the surface of the scintillation cell, and then 'U' 'Because the optical fiber was inserted into the groove and fixed with Mylar tape, the reflective film was manually covered on the outer circumference of the scintillator. Therefore, each process of forming the groove, inserting the optical fiber and covering the reflective film takes extra time. Since the optical fiber is located only on one side of the scintillator, there is a problem that the light efficiency is lowered.

On the other hand, another example of the conventional plastic scintillator manufacturing method is an extrusion method, the extrusion method is that the optical fiber is inserted in the center in the extruder by mixing the polystyrene grains and the fluorescent additive while injecting an inert gas as shown in FIG. After extruding the scintillation cell to form the insertion hole, the optical fiber is inserted into the insertion hole and the reflective film is manually covered by the outer periphery of the scintillation cell. Also, the optical fiber insertion process and the reflective film covering process must be performed separately. There was a problem that it takes a lot, there is a problem that can not manufacture a precise scintillator because there is a limit to accurately fit the insertion hole and the size of the optical fiber into the insertion hole.

An object of the present invention for solving the above problems is to extrude both the optical fiber, the flash cell and the reflective film at the same time to significantly reduce the time and cost for the production of plastic scintillator, and to produce the plastic scintillator to the desired dimensions and shapes have.

A feature of the present invention for achieving the above object is, by simultaneously extruding the optical fiber, the flash cell and the reflective film to provide a plastic scintillator to form a flash cell integrally around the optical fiber, the outer periphery of the flash cell The reflective film may be further formed integrally, and the optical fiber may include only an optical fiber core or a cladding further formed on the outer periphery of the optical core.

And another feature of the present invention is a plurality of hoppers each of the material of each layer of the scintillator including the optical fiber and the scintillation cell, an extrusion die having a plurality of outlets so that the scintillation cells are formed at the outer periphery of the optical fiber, and the hopper Using an extruder comprising a cylinder connecting the respective hopper and the outlet of the extrusion die so that the material is discharged to a corresponding one of the plurality of outlets of the extrusion die, and a screw provided inside the cylinder to discharge the material injected into the hopper And extruding the optical fiber and the scintillation cell simultaneously to form the scintillator so that the scintillation cell is located on the outer periphery of the optical fiber, and the sizing step of the scintillator passing through the extruder step to have a correct dimension and shape while passing through the sizing machine; A pressure comprising the step of passing the extrudate having passed through the sizing machine through a cooler; It's on the way to get out.

In the above configuration, the flash cell and the optical fiber use a material having the same to similar refractive index, and the cladding of the optical fiber uses a material having a smaller refractive index than the optical fiber core.

According to the present invention, the optical fiber and the scintillation cell are simultaneously formed in the extrusion process, thereby greatly reducing the production cost of the scintillator including the optical fiber. In addition, since the optical fiber and the scintillation cell are formed at the same time during the extrusion process, the scintillator can be made in any shape and size desired, and the excessive time and process problems occurring in the extrusion method of inserting the conventional optical fiber separately, and the additional optical fiber It solves all the defects of the scintillator due to the dimensional mismatch caused by the insertion of the gasket, thereby greatly reducing the cost of the scintillator manufacturing, improving the productivity, and forming the desired dimensions, thereby improving the formability. It is effective.

In addition, since the reflective film is integrally extruded on the outer circumference of the flash cell, productivity is improved as compared with a method of manually covering the conventional reflective film manually.

Since the formability is improved and the production cost is greatly reduced, the production cost of various devices using conventional flash cells, for example, a gamma ray detector and a neutron detector, can be reduced, and the performance of these detectors can be improved. There is.

An embodiment of the present invention is described in more detail below.

Figure 2 is a block diagram showing a flasher extrusion system according to the present invention, Figure 3 is a view showing the structure of the extruder, Figure 4 is a cross-sectional view showing the extrusion die structure, Figure 5 is a cross-sectional view showing a plastic flasher according to the present invention. to be.

Extrusion system according to the present invention is largely composed of an extruder 100 and a sizing machine 200, a cooler 300, a drawer 400 and a cutter 500 and a winding machine 600, such an extrusion system is known Since the extrusion system is modified to fit the shape of the flash cell of the present invention, a detailed description thereof will be omitted.

In the above configuration, the extruder 100 includes a plurality of hoppers 112, 122, 132, 142 and 152 into which the material of each layer of the scintillator including the optical fiber core and the cladding, the scintillation cell, and the reflective film is respectively injected. Extrusion die 160 having a plurality of outlets corresponding to the respective shapes so that the cladding, the flash cell, and the reflective film are formed outwardly around the core, and the hoppers 112, 122, 132, 142, and 152 described above. Cylinders connecting the outlets of each of the hoppers 112, 122, 132, 142 and 152 and the extrusion die 160 so that the material injected into the outlet is discharged to the corresponding one of the multiple outlets of the extrusion die 160. (114) 124, 134, 144, 154 and the cylinders 114, 124, 134, 144, 154 are provided inside the hopper 112, 122, 132 And a screw for discharging the material introduced into the (142) and (152).

In addition, the sizing machine 200 has a vacuum inside, a through passage through which the scintillator discharged from the extruder 100 is formed, and the through passage is designed according to the exact shape and dimensions of the scintillator.

In addition, the cooler 300 is installed in series with the sizing machine 200, and the extractor 400 and the cutting machine 500 are provided at the rear of the cooler 300.

As shown in FIG. 3, the extrusion die 160 has the outlet 162 for the optical fiber core in the center, and the first and second cladding outlets 164 on the outside of the outlet 162 for the optical fiber core. 165 is formed, a flash cell discharge port 167 is formed outside the second cladding discharge port 165, and a reflective film discharge port 169 is formed outside the flash cell discharge port 167.

The extrusion method of the present invention using the extrusion system as described above will be described below.

First, look at the material used in the present invention.

Polystyrene (PS) and fluorescent additives are used as materials for scintillation cells and optical fibers.

In the above, the fluorescent additives for the scintillation cell are classified into primary fluorescent additives and secondary fluorescent additives, and primary fluorescent additives use paraphenyl (PT) or 2,5-diphenyloxazole (PPO). Secondary fluorescent additives, that is, wavelength transfer agents, use POPOP or 4-bis (2-methylstyryl) benzene (4-bis (2-Methylstyryl) benzene) (bis-MSB).

Fluorescent additives for optical fibers are based on K27 or US National Diagnostics BBQ (7H-benzimidazo [2,1-a] benz [de] isoquinoline-7-one) and BASF's Lumogen. Existing photomultiplier tube (PMT) or silicon photoelectron multiplier using all wavelengths from 411nm to 613nm by adding fluorescent additives of red, orange, yellow, green, blue, violet and other colors of pink It can also be used for Silicon photomultipliers (SiPM) or Multi Pixel Photon Counters (MPPC).

In addition, looking at the material to be used as the cladding of the optical fiber, the primary cladding of the optical fiber uses a poly methyl methacrylate (PMMA) when using PS as the optical fiber core, the PMMA has a refractive index of 1.59 and a density of 1.19. The secondary cladding coated on the outer circumference of the primary cladding may use any material having a lower refractive index than PMMA (for example, PTFE and PEFE), and in some cases, the secondary cladding may be omitted.

On the other hand, when the optical fiber core is used as PMMA, the refractive index of PTFE, PEFE, etc., which is smaller than PMMA is used as cladding.

The reflective film positioned outside the flash cell is made of aluminum or titanium dioxide (TiO ₂ ).

And look at the manufacturing method using the above materials.

First, the PS granules are dried at 60-90 ° C. for 4-8 hours. Then add a fluorescent additive to the dried PS and mix for 10-30 minutes.

The mixing process can be done in two different ways. One is to mix the polystyrene grains and the fluorescent additives in advance to the hopper of the extruder, the other is to inject the polystyrene and the fluorescent additives into the plurality of extruder hoppers respectively to be mixed in the cylinder of the extruder, the practice of the present invention In the example, a method of mixing in advance is used. In this case, pay attention to mixing so that the fluorescent additives are evenly distributed.

Then, the prepared material is put into a hopper corresponding to each outlet, and the optical fiber core, the cladding, the flash cell, and the reflective film are simultaneously extruded, and the optical fiber core, the cladding (primary / secondary), the flash cell, and the reflective film Position them sequentially.

The scintillator passed through the extrusion step has a precise dimension and shape while passing through the sizing machine. The extrusion die of the extruder has a size slightly larger than that of the desired scintillator, and the sizing machine can obtain a desired dimension through a plurality of steps. A number of sizing dies are provided.

The scintillator formed to the desired dimension is cooled through the cooler, and the scintillator drawn through the takeover machine is cut into the desired size by the cutter.

The scintillator thus formed has square, hexagonal, and rectangular shapes, and as shown in FIG. 5 from the inside, the optical fiber core 172, the half-clad cladding 174, 175, the flash cell 177, and the reflective film 179. The diameter of the optical fiber is determined as necessary.

1 is a view showing a manufacturing process of a plastic scintillator by a conventional extrusion method

2 is a view showing an extrusion system according to the present invention;

Figure 3 shows a schematic structure of an extruder according to the invention

4 is a cross-sectional view showing the structure of an extrusion die according to the present invention.

5 is a cross-sectional view showing a plastic scintillator according to the present invention

Claims (5)

The flash cell is composed of a polystyrene and a fluorescent additive to convert the incident particles into light, and is located in the center of the flash cell, and consists of an optical fiber for collecting light from the flash cell and transmitting it to the outside. Plastic scintillator, characterized in that the optical fiber is simultaneously extruded to be configured integrally. The plastic scintillator according to claim 1, wherein a reflective film is further formed integrally with the outer circumference of the scintillation cell. 3. The plastic scintillator according to claim 1 or 2, wherein the optical fiber is selected from the group consisting of a core alone, or a cladding layer having a smaller refractive index than the optical fiber core is integrally formed between the optical fiber and the flash cell. A plurality of hoppers into which the material of each layer of the scintillator including the plastic flash cell material and the plastic optical fiber material composed of polystyrene and the fluorescent additive is respectively injected, and an extrusion die having a plurality of outlets to simultaneously form the scintillation cell on the outer periphery of the optical fiber; A cylinder connecting each hopper and an outlet of the extrusion die so that the material injected into the hopper is discharged to a corresponding one of the plurality of outlets of the extrusion die, and a screw provided inside the cylinder to discharge the material injected into the hopper. Using an extruder, An extrusion step of simultaneously extruding the optical fiber and the scintillation cell so that an optical fiber for collecting the light from the scintillation cell and transmitting it to the outside is located inside the scintillation cell for converting the incident particles into light; A sizing step in which the scintillator passing through the extrusion step has a correct dimension and shape while passing through a sizing machine; And a step of cooling the extrudate passing through the sizing machine through a cooler. The method of claim 4, wherein the scintillation cell and the optical fiber use a material having the same to similar refractive index.

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