JP3746611B2 - Method for assembling charged particle accelerator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for assembling a charged particle acceleration device that accelerates charged particles such as electrons and protons using a superconducting acceleration cavity.
[0002]
[Prior art]
The charged particle accelerator introduces microwaves into a resonant superconducting acceleration cavity maintained in a superconducting state from an input coupler, generates a high electric field in the cavity, and uses the potential difference to generate electrons, protons, etc. It is a device that accelerates charged particles.
[0003]
Superconducting accelerating cavities consume very little microwave power in the cavity wall compared to normal cavities, so they are energy saving and can store a large amount of energy in the cavities, resulting in a high accelerating electric field. Further, since there is no cavity heat generation, the continuous operation is possible.
[0004]
However, it is necessary to keep the hollow body at an extremely low temperature of −269 ° C. or lower, and the hollow body is generally immersed and cooled with liquid helium. For this reason, a cryogenic container (cryostat) for storing the liquid helium of the cryogenic bear is required.
[0005]
In the superconducting accelerating cavity, as described above, the material constituting the cavity wall (generally niobium material) is in a superconducting state. If chemical residue, dust from washing the cavity, or dust from the assembly of the cavity adheres, heat is generated by the surface current and superconducting breakdown (quenching) occurs, or a high electric field is generated in the cavity. Therefore, the garbage and dust become a discharge source. For this reason, the inner surface of the superconducting acceleration cavity is required to be as clean as a semiconductor.
[0006]
FIG. 11 shows a conventional charged particle accelerator, which includes a pair of superconducting accelerating cavities 1 arranged in series. These superconducting accelerating cavities 1 include a cavity body 2. The structure is cooled with liquid helium 3. Specifically, the cavity main body 2 is accommodated in a container 4 containing liquid helium 3, and the cavity main body 2 is cooled by the liquid helium 3 in the container 4.
[0007]
The hollow body 2 is generally formed by welding a plurality of (two in the example of FIG. 11) units 2a. Beam pipes 5 and 6 are provided at both ends of the cavity main body 2, and ports 7 and 8 are attached to the beam pipes 5 and 6, respectively.
[0008]
An input coupler 9 for injecting microwaves into the cavity body 2 is flange-joined to the port 7 of one beam pipe 5, and the port 8 of the other beam pipe 6 is excited into the cavity body 2. A harmonic coupler 10 for releasing an electric field unfavorable for accelerating charged particles to the outside of the cavity body 2 is flange-joined. Furthermore, a gate valve 11 is connected to the tip of the other beam pipe 6.
[0009]
The container 4 containing the liquid helium 3 is designed to reduce the amount of heat entering the liquid helium container 4 to a minimum from the viewpoint of suppressing the evaporation amount of the helium 3 to the liquid. For this reason, FRP having a low thermal conductivity is often adopted as a support material for the liquid helium container 4. For the same reason, the outer periphery of the liquid helium container 4 is covered with radiant heat shield plates 12 and 13 cooled at a low temperature around −250 ° C. or around −196 ° C., and the penetration of radiant heat is suppressed. The entire liquid helium container 4 is housed in a vacuum container 14 and is vacuum insulated. Both end portions of the vacuum vessel 14 are sealed by the end plate 15.
[0010]
As described above, the charged particle accelerator is composed of several layers of components, and therefore, many processes are required for the assembly thereof, and many problems are involved in managing and maintaining the high cleanliness of the inner surface of the cavity body 2. There is.
[0011]
The specific assembly procedure of the conventional charged particle accelerator will be described. First, as shown in FIG. 12, the cavity body 2 is housed in a container 4 containing liquid helium 3 and integrated as a superconducting acceleration cavity 1. It has become. The inner surface of the cavity body 2 is subjected to electric field polishing or chemical polishing.
[0012]
After polishing the inner surface of the hollow body 2, a sealing plate 16 is attached to the opening at the tip of the port 7 in one beam pipe 5 and the opening at the tip of the other beam pipe 6 in the clean room. A harmonic coupler 10 is attached to an opening at the tip of the port 8 in the pipe 6 to seal the inside of the cavity body 2.
[0013]
Next, the superconducting acceleration cavity 1 is unloaded from the clean room, and as shown in FIG. 13, the unloaded superconducting acceleration cavity 1 is inside the vacuum container 14 in which the radiation heat shield plates 12 and 13 are integrally attached in advance. Insert it from the side and assemble it.
[0014]
After that, as shown in FIG. 14, the tower bellows 17 is assembled, the sealing plate 16 of the port 7 for the input coupler is removed, and the input coupler 10 is flange-joined to the port 7. At this time, since the entire accelerator is in a normal atmosphere such as a factory or a general laboratory, the flange fastening portion is covered with a simple clean booth, but the inside of the cavity body 2 is in an atmosphere containing dust. Opened and the inner surface of the cavity body 2 is contaminated.
[0015]
Finally, as shown in FIG. 15, end plates 15 are attached to openings at both ends of the vacuum vessel 14, and the gate valve 11 and the tuning device 18 are attached to the beam pipe 6. When the gate valve 11 is mounted, the sealing plate 16 attached to the beam pipe 6 is removed. Accordingly, at this time, the inside of the hollow body 2 is opened to the atmosphere containing dust.
[0016]
[Problems to be solved by the invention]
As described above, conventionally, when the acceleration device is assembled, the inside of the cavity main body 2 is opened to the atmosphere containing dust twice, so that the inner surface of the cavity main body 2 is contaminated by dust and dust in the atmosphere. The expected performance cannot be obtained.
[0017]
The present invention has been made paying attention to such points, and an object of the present invention is to provide a method for assembling a charged particle acceleration device that can prevent contamination of the inner surface of the cavity body and always obtain initial performance. It is to provide.
[0018]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a superconducting accelerating cavity having beam pipes at both ends, an input coupler being attached to one of the beam pipes, and a harmonic coupler and a gate valve being attached to the other beam pipe. A method of assembling a charged particle acceleration device comprising a vacuum vessel containing an acceleration cavity , wherein the body of the vacuum vessel is composed of a plurality of detachable drums, and a superconducting acceleration cavity is formed in a clean room While inserting into one of the drums and assembling the drum, an input coupler, a harmonic coupler and a gate valve are attached to each beam pipe of the superconducting accelerating cavity so that the inside of the superconducting accelerating cavity body is inside. After sealing, the superconducting acceleration cavity assembled to the drum is taken out of the clean room, and after this delivery, the remaining drums are assembled to the drum. It is characterized by composing the vacuum containers sealed put.
[0019]
The invention according to claim 2 is characterized in that the superconducting acceleration cavity of the charged particle accelerator has a structure in which the cavity main body is housed in a liquid helium container and integrated.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
1 is a sectional view of the assembled charged particle accelerator, FIG. 2 is a partially broken plan view, FIG. 3 is a sectional view taken along line AA in FIG. 1, and FIG. FIG. 2 is a sectional view taken along line BB in FIG.
[0023]
In the figure, reference numeral 21 denotes a superconducting acceleration cavity. The superconducting acceleration cavity 21 is formed by integrating a cavity main body 22 in a liquid helium container 23. The hollow body 22 has beam pipes 25 and 26 at both ends, and a reservoir tank 24 is connected to the liquid helium container 23.
[0024]
27 is a harmonic coupler, 28 is a gate valve, 29 is a 20K radiant heat shield plate, 30 is an 80K radiant heat shield plate, 31 is an input coupler, 32 is a liquid nitrogen supply / discharge pipe, 33 is a liquid helium supply / discharge pipe, 34 Is a vacuum vessel, 35 is a cavity support, and 36 is a cavity receiver.
[0025]
The vacuum vessel 34 has a large-diameter barrel portion 37 composed of a plurality of, for example, three drums 37a, 37b, and 37c that can be divided in the longitudinal direction, and end plates 38a attached to openings at both ends of the barrel portion 37. 38b.
[0026]
The drums 37a, 37b, and 37c constituting the body portion 37 are joined to each other by flange joining, and one end plate 38a is flange joined to the opening edge of the drum 37a on one end side, and the drum 37c on the other end side is joined. The other end plate 38b is flange-joined to the opening edge.
[0027]
The superconducting accelerating cavity 21 and the reservoir tank 24 are housed inside the large-diameter vacuum container 34, and a 20K radiation heat shield plate 29 is placed inside the vacuum container 34 so as to cover the superconducting accelerating cavity 21 and the reservoir tank 24. And an 80K radiant heat shield plate 30 is attached.
[0028]
The reservoir tank 24 communicates with the liquid helium container 23 through the communication pipe 39, and a sufficient amount of liquid helium 40 is accommodated from the reservoir tank 24 to the liquid helium container 23. A liquid helium supply / discharge pipe 32 is connected to the reservoir tank 24.
[0029]
As shown in FIG. 3, the cavity receiver 36 is disposed below the liquid helium container 23, and the cavity support member 35 is inserted from the upper part of the intermediate drum 37 b constituting the vacuum container 34 to the lower side in the interior thereof. The lower ends of the cavity support members 35 are connected to the cavity receiver 36, and the superconducting acceleration cavity 21 is horizontally supported by the cavity support member 35 and the cavity receiver 36.
[0030]
The assembly procedure of this charged particle acceleration device will be described. First, as shown in FIG. 5, the cavity body 22 and the liquid helium vessel 23 are integrally assembled in advance as a superconducting acceleration cavity 21. Under this condition, in the clean room, as shown in FIG. 6, a reservoir tank 24 is attached to the liquid helium container 23, and a harmonic coupler 27 and a gate valve 28 are attached to the beam pipe 26 of the superconducting acceleration cavity 21. Then, after the reservoir tank 24, the harmonic coupler 27, and the gate valve 28 are attached, the superconducting acceleration cavity 21 is placed on the cavity receiver 36.
[0031]
Reference numeral 42 shown in FIG. 7 denotes a transport mechanism. On the transport mechanism 42, one of drums 37 a, 37 b, and 37 c constituting the body 27 of the vacuum vessel 34, that is, an intermediate part of the body 27 is formed. A drum 37b is arranged in advance. Then, the superconducting acceleration cavity 21 disposed on the cavity receiver 36 is inserted into the drum 37b together with the cavity receiver 36 through the transport mechanism 42 as shown in FIG.
[0032]
Then, the input coupler 31 is inserted from the outside of the drum 37b to the inside thereof, and the lower end portion thereof is connected to the port 43 of the beam pipe 25, and the cavity support member 35 is inserted from the outside of the drum 37b to the inside thereof, and the lower end portion thereof is The superconducting acceleration cavity 21 is lifted and supported horizontally by the cavity support 36 and the cavity support 35 and the cavity support 36. At this point, the cavity body 22 is completely sealed. The procedure may be such that the harmonic coupler 27 and the gate valve 28 are attached to the beam pipe 26 after the superconducting acceleration cavity 21 is inserted and assembled into the drum 37b.
[0033]
Thus, after the inside of the cavity main body 22 is sealed and the entire superconducting acceleration cavity 21 is assembled to the drum 27c, this assembly is cleaned with a crane 44 or the like as shown in FIG. The remaining drums 27a and 27c are attached to both ends of the drum 27b by flange joining in a normal atmosphere such as a factory or laboratory, and the body 27 of the vacuum vessel 34 is assembled. The 20K radiant heat shield plate 29 and the 80K radiant heat shield plate 30 are assembled on the inside.
[0034]
After that, as shown in FIG. 9, end plates 38a and 38b are attached to the openings at both ends of the body portion 27 and sealed, and the liquid nitrogen supply pipe 33 is supplied to one end plate 38a and the liquid helium is supplied to the other end plate 38b. The pipes 33 are respectively attached, and finally the end plates 38a and 38b are sealed and welded, whereby the assembly is completed.
[0035]
According to such an assembling procedure, the inside of the hollow body 22 is completely sealed in the clean room, and after the sealing, the vacuum container 34 is assembled in a normal atmosphere such as a factory or a laboratory. Also, it is not opened to the atmosphere containing dust, so that contamination of the inner surface of the cavity body 22 can be reliably prevented and the initial performance can always be maintained.
[0036]
Conventionally, when an input coupler or gate valve is attached to the beam pipe of the cavity body, the interior of the cavity body is opened to the atmosphere containing dust, and the dust in the atmosphere enters the cavity body. As a heat source, the cavity performance is reduced.
[0037]
In the present invention, once the input coupler 31 and the gate valve 28 are once attached to the beam pipes 25 and 26 of the cavity body 22 in the clean room, the interior of the cavity body 22 is then opened to the atmosphere containing dust. Therefore, it is possible to move to the final assembly and thus prevent contamination in the cavity body 22 and obtain high cavity performance.
[0038]
In addition, the vacuum container 34 is configured to have a large diameter, and therefore, a reservoir tank 24 for storing liquid helium 40 can be stored separately from the liquid helium container 23, and the liquid helium is stored via the reservoir tank 24. 40 can be stored abundantly, and even if there is a heat generation of the cavity main body 22 or a large amount of intrusion heat into the liquid helium container 23 due to an unexpected trouble, the liquid level of the liquid helium 40 in which the cavity main body 22 is immersed is The cavity body 22 can continue to be effectively cooled without being lowered, and the operational reliability of the apparatus is improved.
[0039]
【The invention's effect】
As described above, according to the present invention, the interior of the cavity body can be transferred to the final assembly process without being opened to the atmosphere containing dust, and therefore, contamination of the inner surface of the cavity body can be surely prevented and The performance can be maintained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a charged particle acceleration apparatus according to an embodiment of the present invention.
FIG. 2 is a partially broken plan view of the charged particle acceleration device.
3 is a cross-sectional view taken along line AA in FIG.
4 is a cross-sectional view taken along line BB in FIG. 1. FIG.
FIG. 5 is an explanatory diagram showing a first stage of a procedure for assembling the charged particle acceleration device.
FIG. 6 is an explanatory view showing the second stage in the same manner.
FIG. 7 is an explanatory view showing the third stage.
FIG. 8 is an explanatory view showing the fourth stage.
FIG. 9 is an explanatory view showing the fifth stage.
FIG. 10 is an explanatory view showing the final stage.
FIG. 11 is a cross-sectional view of a conventional charged particle acceleration device.
FIG. 12 is an explanatory view showing a first stage of a procedure for assembling the charged particle acceleration device.
FIG. 13 is an explanatory view showing the second stage in the same manner.
FIG. 14 is an explanatory view showing the third stage.
FIG. 15 is an explanatory view showing the fourth stage.
[Explanation of symbols]
21 ... Superconducting acceleration cavity 22 ... Cavity body 23 ... Liquid helium vessel 24 ... Reservoir tank 25, 26 ... Beam pipe 31 ... Input coupler 34 ... Vacuum vessel 35 ... Cavity support 36 ... Cavity receptacles 37a, 37b, 37c ... Drum 38a, 38b ... end plate 40 ... liquid helium

Claims (2)

A superconducting accelerating cavity having a beam pipe at both ends, an input coupler in one of the beam pipes, a harmonic coupler and a gate valve attached to the other beam pipe, and a vacuum vessel containing the superconducting accelerating cavity A method for assembling a charged particle accelerator comprising:
The body of the vacuum vessel is composed of a plurality of detachable drums, and a superconducting acceleration cavity is inserted into one of the plurality of drums and assembled to the drum in a clean room, while the superconducting An input coupler, a harmonic coupler, and a gate valve are attached to each beam pipe of the accelerating cavity to seal the inside of the superconducting accelerating cavity, and then the superconducting accelerating cavity assembled to the drum is taken out of the clean room. A method of assembling a charged particle accelerating device, wherein after the unloading, the remaining drum is assembled to the drum to constitute a sealed vacuum container.   The charged particle acceleration device assembling method according to claim 1, wherein the superconducting acceleration cavity has a structure in which the cavity main body is housed in a liquid helium container and integrated.

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