JP2899716B2 - Superconducting wiggler - Google Patents

Description

The present invention relates to a superconducting wiggler in which an electron beam accelerated by an electron accelerator is meandered by a superconducting coil, and more particularly, to a superconducting wiggler for cooling a superconducting coil. The present invention relates to a superconducting wiggler in which the amount of evaporation of a cryogenic liquid (such as liquid helium) is reduced.

2. Description of the Related Art A superconducting wiggler is a device in which an electron beam accelerated by an electron accelerator such as a linac or a synchrotron is abruptly meandered by a superconducting coil to extract a desired radiation. The outline of the superconducting wiggler is shown in FIG.

As shown in the drawing, a superconducting coil c for meandering the electron beam a in the duct b is arranged along the path of the vacuum duct b through which the electron beam a accelerated by the electron accelerator passes. These superconducting coils c are immersed in a cryostat d in which liquid helium (about 4.2 to 4.5K) is stored to maintain a superconducting state, and are in a very low temperature state.

[Problems to be Solved by the Invention] In such a superconducting wiggler, radiation (X-rays or the like) is generated when the electron beam a in the vacuum duct b meanders. This radiation passes through the vacuum duct b formed of stainless steel, aluminum, or the like, and enters a cryostat d in which liquid helium is stored.
Invading as energy.

Then, a large amount of liquid helium stored in the cryostat d in order to cool the superconducting coil c evaporates.

As a countermeasure against this, as shown in FIG. 6, the present applicant previously placed a tungsten plate e (plate thickness of 1 to 2 mm) having a large radiation shielding ability on the outside of the vacuum duct b so as to cover the duct b. It was developed to bend in a shape and cover the duct b.

However, as is well known, the workability of the tungsten plate e is extremely poor. Further, once bent into a U-shape as shown in FIG. 6, a springback phenomenon as shown by a broken line in the figure occurs. Therefore, bending the tungsten plate e into a U-shape so as to cover the vacuum duct b,
Due to the poor workability, the production cost is increased.

An object of the present invention, which has been made in consideration of the above circumstances, is to provide a superconducting wiggler that can shield radiation in a vacuum duct at low manufacturing cost and reduce the amount of evaporation of liquid helium (cryogenic liquid) in a cryostat. To provide.

Means for Solving the Problems In order to achieve the above object, the present invention provides a superconducting coil for meandering an electron beam outside a vacuum duct through which the electron beam passes, In a superconducting wiggler immersed in a cryostat filled with liquid, the vacuum duct is disposed so as to penetrate the center of the cryostat, and the outer periphery of the vacuum duct is wound with a heavy metal wire such as tungsten. A radiation shielding layer is formed, and the outer periphery of the radiation shielding layer is provided so as to cover an outer tube filled with water or a coolant.

[Operation] The electron beam in the vacuum duct meanders due to the electromagnetic field of the superconducting coil. At this time, radiation (such as X-rays) is generated from the meandering electron beam, and this radiation is shielded in the vacuum duct by a radiation shielding layer formed in the vacuum duct located at the center of the cryostat. Accordingly, the radiation is suppressed or prevented from entering the cryostat, and the temperature of the cryogenic liquid (liquid helium or the like) in the cryostat can be favorably maintained.

In addition, since the radiation shielding layer is formed by winding the outer periphery of the vacuum duct with a heavy metal wire having a large radiation shielding ability, the radiation shielding layer is not heat-resistant even in heavy metal (for example, tungsten or the like) having poor workability. By subjecting to interworking or the like, it can be easily wound and can be manufactured at low cost.

Further, the radiation shielding layer that generates heat by shielding radiation is cooled by water or a coolant filled in the outer tube.

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

As shown in FIG. 3, along a vacuum duct 2 through which an electron beam 1 accelerated to almost the speed of light by a linac or a synchrotron (not shown) passes,
Superconducting coil 3 for meandering electron beam 1 in duct 2
Is provided. These superconducting coils 3 are Nb-T
It is formed from i, Nb-Zr, etc., and is immersed in a cryostat 5 in which a cryogenic liquid such as liquid helium 4 (about 4.2 to 4.5K) is stored to maintain a superconducting state. I have.

On the other hand, the vacuum duct 2 is formed of stainless steel or aluminum, and as shown in FIG. 1, a radiation shielding layer 7 is formed by winding a tungsten wire 6 having a large radiation shielding ability around its outer periphery. I have. As shown in the figure, the tungsten wire 6 is wound tightly so that the adjacent wires 6 are in close contact with each other. Further, as shown in FIG. 3, the radiation shielding layer 7 is provided with a cryostat 5.
Is formed on the outer peripheral surface of the vacuum duct 2 located in the center of the vacuum duct. The radiation shielding layer 7 can be formed extremely easily by hot working at a predetermined atmospheric temperature when the tungsten wire 6 is wound around the vacuum duct 2.

After winding the vacuum duct 2 with a tungsten wire 6, as shown in FIG.
By applying a metal plating 8 of r, Ni, Cu or the like, the adjacent wires 6 of the wound tungsten wires 6 are fixed to each other. Since the tungsten wire 6 is for forming the radiation shielding layer 7 and is not a strength member,
There is no need for such a large fixing strength.
Is sufficient.

More specifically, in the present embodiment, as shown in FIG. 4, a wire 6 made of tungsten is wound around the outer periphery of a vacuum duct with a predetermined gap 9 between the duct 2 so that the radiation shielding layer 7 is evacuated. The duct 2 is formed with a predetermined gap 9 therebetween, and this is covered with an outer tube 11 filled with water or a coolant 10. The radiation shielding layer 7 is provided with a passage 12 for guiding water or the coolant 10 on the outer tube 11 outside the layer to the vacuum duct 2 side in the layer.

 The operation of the present embodiment having the above configuration will be described.

The electron beam 1 in the vacuum duct 2 meanders due to the electromagnetic field of the superconducting coil 3. At this time, the meandering electron beam 1
(E.g., X-rays) are generated from the radiation, but the radiation is shielded in the vacuum duct 2 by the radiation shielding layer 7 formed in the vacuum duct 2 located at the center of the cryostat 5.

Therefore, the radiation is suppressed and prevented from entering the cryostat 5 as energy. Therefore,
The temperature of the liquid helium 4 in the cryostat 5 can be favorably maintained, and the evaporation of the liquid helium 4 is reduced.

Further, since the radiation shielding layer 7 is formed by winding the outer periphery of the vacuum duct 2 with a tungsten wire 6, it is easily wound by performing hot working at a predetermined atmospheric temperature. It can be turned and can be manufactured at low cost.

Radiation such as X-rays generated is shielded by the radiation shielding layer 7 to not only reduce the evaporation of the liquid helium 4 in the cryostat 5 shown in FIG. 3 but also to generate heat by shielding the radiation. The layer 7 is actively cooled by water or the coolant 10 from the outside and the inside of the layer as shown in FIG.

In this embodiment, the wire 6 made of tungsten is used to form the radiation shielding layer 7, but the invention is not limited to this, and a wire made of heavy metal such as lead having a radiation shielding effect may be used. Further, the cross section of the wire 6 may be square instead of round. In this case, the gap between the adjacent wires after winding can be reduced, and the radiation shielding effect is enhanced. Further, the radiation shielding effect may be enhanced by winding the wire in multiple layers such as double and triple instead of single winding.

[Effects of the Invention] As described above, according to the present invention, the following excellent effects can be exhibited.

Since the radiation shielding layer is formed by winding a heavy metal wire such as tungsten around the outer periphery of the vacuum duct where the cryostat is located, the radiation shielding layer can be formed at low manufacturing cost, and the electron beam in the vacuum duct is Radiation generated during meandering can be shielded in the vacuum duct, and the amount of evaporation of the cryogenic liquid (liquid helium or the like) in the cryostat can be reduced. Further, the radiation shielding layer that generates heat by shielding the radiation is cooled by the water or the coolant filled in the outer tube, so that the thermal influence from the radiation shielding layer on the cryostat can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part showing a state of winding a tungsten wire wound around a vacuum duct of a superconducting wiggler according to one embodiment of the present invention, and FIG. 2 is a vacuum duct obtained by applying a metal plating to the tungsten wire. 3 is a schematic view of the superconducting wiggler, FIG. 4 is a sectional view of a vacuum duct of the superconducting wiggler of a modified embodiment of the present invention, and FIG. FIG. 6 is a schematic view of the superconducting wiggler obtained, and FIG. 6 is a cross-sectional view showing a tungsten plate coated on the vacuum duct shown in FIG. In the figure, 1 is an electron beam, 2 is a vacuum duct, 3 is a superconducting coil, 4 is liquid helium as a cryogenic liquid, 5 is a cryostat, 6 is a tungsten wire, and 7 is a radiation shielding layer.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) H05H 13/04 G21K 1/08-1/093 G21F 3/00

Claims (1)

(57) [Claims] A superconducting wiggler in which a superconducting coil for meandering an electron beam is provided outside a vacuum duct through which the electron beam passes, and the superconducting coil is immersed in a cryostat filled with a cryogenic liquid, The vacuum duct is disposed so as to penetrate the center of the cryostat, and a radiation shielding layer is formed by winding a heavy metal wire such as tungsten on the outer periphery of the vacuum duct, and on the outer periphery of the radiation shielding layer, A superconducting wiggler provided so as to cover an outer tube filled with water or coolant.