JPH0676988A - Neutron shield device for particle accelerator - Google Patents

Abstract

PURPOSE:To keep a water bath free from the effect of the magnetic characteristics of a deflection electromagnet by forming the bath out of a nonmagnetic material, and enable space to be saved by using the bath as an electromagnet cooling water bath in common. CONSTITUTION:Water baths 20 containing water are so laid as to be adjacent to the peripheral side of deflection electromagnets 8 laid along the curved section of a storage ring 5. The water in the baths 20 is used as a shield body to isolate neutrons. In this case, the baths 20 are preferably formed out of a nonmagnetic material. Also, the water may practically be used as cooling water to cool the deflection electromagnets 8 or the like. As a result, the shield of neutrons can be ensured, regardless of simple constitution where the water baths 20 are simply laid at the peripheral side of the deflection electromagnets 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neutron shielding device for a particle accelerator such as a synchrotron.

[0002]

2. Description of the Related Art In recent years, a synchrotron, which is a relatively small particle accelerator having a diameter of 10 m or less, is being developed.
By using synchrotron radiation (SOR light) which is radiation emitted from such synchrotron, for example, various fields such as manufacturing of VLSI circuits, diagnosis in the medical field, molecular analysis, structural analysis, etc. Expected to be applied.

FIG. 2 shows an outline of the synchrotron. In this synchrotron, an electron beam generated by an electron generator 1 such as an electron gun is accelerated by a linear accelerator (linac) 2 to near the speed of light, deflected by a deflecting electromagnet 3 and then stored in a storage ring 5 via an inflector 4. Incident. The electron beam incident on the storage ring 5 is converged by the converging electromagnets 7 ... While being given energy by the high-frequency acceleration cavity 6 and is deflected by the deflection electromagnets 8 ... Then, when the SOR light is deflected by the deflection electromagnet 8, the SOR light is emitted and emitted to, for example, the exposure device 10 via the beam line 9 which is a light extraction line for use.

[0004]

By the way, neutrons are generated toward the outer peripheral side from the deflection portion of the synchrotron, that is, the curved portion of the storage ring 5 provided with the deflection electromagnet 8. Therefore, it is necessary to shield it. However, the neutron is X
Unlike rays and γ rays, it cannot be easily shielded with metallic materials such as lead or concrete, and therefore there has been a demand for the development of means that can reliably and easily shield neutrons.

[0005]

The present invention is an apparatus for shielding neutrons emitted from the curved portion of a storage ring in a particle accelerator such as a synchrotron and emitted to the outer peripheral side of the storage ring, It is characterized in that a water tank is provided adjacent to the outer circumference side of the bending electromagnet installed in the curved portion, and water as a neutron shield is held in the water tank. In this case, it is desirable that the water tank is made of a non-magnetic material. Further, it is conceivable that the water held in the water tank is cooling water for cooling the deflection electromagnet.

[0006]

[Function] Neutrons are generated from the curved portion of the storage ring and are emitted toward the outer periphery of the deflection electromagnet, and the neutrons enter the water tank provided on the outer periphery of the deflection electromagnet. Since it has a property of being difficult to permeate, the water held in the aquarium cannot be permeated and is blocked there. That is, the water in the water tank acts as a neutron shield.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a perspective view showing a state in which a neutron shielding device according to an embodiment of the present invention is installed in the synchrotron shown in FIG. 2, reference numeral 5 is a storage ring in the synchrotron, and 8 is a storage ring 5 thereof. A deflecting electromagnet installed in the curved portion of the storage ring 5 for deflecting the charged particles circulating therein, 9 is a beam line provided in the tangential direction of the storage ring 5 for extracting SOR light, and reference numeral 20 It is a water tank as a neutron shielding device of the present embodiment. In this embodiment, three independent water tanks 20 are installed on the outer peripheral side of each of the three divided bending electromagnets 8. Reference numeral 21 is a lid for internal inspection provided on the top plate of the water tank 20, and 22 is a radiation monitor for monitoring the contamination of the water held in the water tank.

The water tank 20 is formed of a non-magnetic material, for example, a non-magnetic metal plate such as fiber reinforced resin (FRP) or a copper plate, and the beam line 9 is passed between adjacent water tanks 20. The recess 20a is secured. Each of the water tanks 20 holds water as a shield for neutrons generated in the deflecting portion of the storage ring 5 and emitted to the outer peripheral side thereof in a substantially full state.

The water held in the water tank 20 serving as a neutron shield is also used as cooling water for the deflection electromagnet 8, and a circulating supply device (not shown) is provided from the water tank 20 to the deflection electromagnet 8 adjacent thereto. By the supplied water being supplied and returned as cooling water, the deflection electromagnet 8 is forcibly cooled and its overheat is prevented. Further, although the temperature of the retained water is increased by cooling the deflection electromagnet 8, the retained water is supplied to the cooling source device (not shown) through the pipe line 23 in order to always maintain the temperature of the retained water in the water tank 20 at a low temperature. It is circulated between and to be cooled.

As described above, by providing the water tank 20 adjacent to the outer circumference of the deflection electromagnet 8, the neutrons generated in the curved portion of the storage ring 5 and emitted to the outer circumference pass through the wall surface of the water tank 20. Then, it will be incident on the inside of the water tank 20, but since neutrons have a property of being difficult to penetrate through water,
It is prevented that the retained water acts as a shield and the neutrons are shielded there, and penetrate the water tank 20 to be released to the outside. The width d of the water tank 20 may be set so that neutrons can be effectively shielded by the retained water, but a sufficient shielding effect is usually obtained at about 30 cm.

The apparatus having the above-mentioned structure has a very simple structure in which the water tank 20 is simply provided on the outer peripheral side of the deflecting electromagnet 8, but can reliably shield neutrons. The water held in the water tank is also used as the cooling water for the deflection electromagnet 8, that is, the water tank 20 also serves as a cooling water tank for cooling the deflection electromagnet 8. There is an advantage that the cooling water tank installed at the position can be omitted to save space and the piping length of the cooling water pipe connecting them can be minimized.

Further, since the water tank 20 is installed adjacent to the deflection electromagnet 8, when the water tank 20 is made of a magnetic material such as an iron plate, the magnetic characteristics of the deflection electromagnet 8 are affected. If the water tank 20 is made of a non-magnetic material as described above, such a problem does not occur. In particular, when the water tank 20 is made of fiber reinforced resin (FRP), even a water tank having a complicated shape having the recess 20a can be easily and inexpensively manufactured.

The water in the water tank 20 is not always used as cooling water, and may be simply retained as a neutron shield without any use, or used for other purposes if possible. Is also good. Also, when used as cooling water, it may be used not only as cooling water for the deflection electromagnet 8 but also for cooling other devices such as an ion pump for evacuation. Further, in the above-described embodiment, the water in the water tank 20 is forcibly cooled and maintained at a low temperature, but sufficient natural heat dissipation from the water tank 20 can be expected, and there is a concern that the temperature of the stored water will rise excessively. For example, the water held is not necessarily forcedly cooled. Of course, aquarium 2
The shape and size of 0 may be arbitrarily changed according to the shape and size of the deflection electromagnet 8, the presence or absence of the beam line 9 and its position, and the like.

[0014]

As described above, according to the neutron shielding apparatus of the present invention, the water held in the water tank serves as a shield due to the extremely simple construction in which the water tank is provided adjacent to the outer periphery of the deflection electromagnet. There is an effect that the neutron can be surely shielded by acting. And, in particular, by forming the water tank with a non-magnetic material, the magnetic characteristics of the deflection electromagnet are not affected, and if the water held in the water tank is used as cooling water for cooling the deflection electromagnet, There is an advantage that the cooling water tank, which is conventionally installed at a position away from the bending electromagnet, can be omitted, and the space can be saved.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a neutron shielding device which is an embodiment of the present invention.

FIG. 2 is a diagram showing an outline of a synchrotron.

[Explanation of symbols]

 5 Storage ring 8 Bending electromagnet 20 Water tank 20a Recess 21 Lid 22 Radiation monitor.

Claims (3)

[Claims] 1. A device for shielding neutrons generated from a curved portion of a storage ring in a particle accelerator such as a synchrotron and emitted to the outer peripheral side of the storage ring, the deflection being installed in the curved portion. A neutron shielding apparatus in a particle accelerator, characterized in that a water tank is provided adjacent to the outer periphery of an electromagnet, and water as a neutron shield is held in the water tank. 2. The neutron shielding device in a particle accelerator according to claim 1, wherein the water tank is made of a non-magnetic material. 3. The neutron shielding device for a particle accelerator according to claim 1, wherein the water held in the water tank is cooling water for cooling the deflection electromagnet.