JPH07245199A - Superconducting accelerator - Google Patents

Abstract

PURPOSE:To enhance the reliance upon the leak-tightness of the joint part at the time of cooling or through heat cycles and provide a sufficient endurance against the high temp. annealing of the joint part by welding a superconducting acceleration cavity made of niobium to an ultra-low temp. vessel made of titanium into a single piece structure. CONSTITUTION:A superconducting acceleration cavity 1 made of niobium accelerating a charged particle beam 2 is embodied in a 10-gang (5-gang X2) structure, and a boss-equipped ring 3 made of niobium is welded to each end of the cavity. The part of cavity furnished with the ring 3 undergoes an edge preparation, and an ultra-low temp. vessel 4 made of titanium is joined rigidly by means of electron beam welding. The vessel 4 is equipped with a port 5 for injection of liquid He and a port 6 for exhaust of He gas. An input coupler 7 as a port to feed in microwaves for acceleration of the beam 2 is welded to the edge prepared part of the vessel 4 through the ring 3. The area around the cavity 1 is filled with liquid He.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting accelerator as a superconducting device used in a charged particle beam accelerator system.

[0002]

2. Description of the Related Art Conventionally, as a superconducting accelerator in which a superconducting accelerating cavity and a cryogenic container are integrated, for example, one shown in FIG. 2 or 3 is known. (1) In the superconducting accelerator shown in FIG. 2, the superconducting accelerating cavity 21 and the cryogenic container 22 are integrated by a flange / indium assembly. The superconducting acceleration cavity 21 is made of niobium, and
A cavity having a structure of 2 × 10 stations is shown. The superconducting acceleration cavity
21 is housed inside a cryogenic container 22 made of stainless steel. Here, liquid helium 23 is immersed in the cryogenic container 22 to bring the superconducting acceleration cavity 21 to a cryogenic temperature and keep it in the superconducting state. At the joint between the superconducting acceleration cavity 21 and the cryogenic container 22, an indium material 24 is gasketed as shown in FIG. 4 to keep airtightness. Note that reference numeral 25 in the figure is a vacuum container.

As shown in FIG. 6, the superconducting accelerating cavity 21 has a superconducting accelerating cavity in which the niobium purity of the inner surface and the surface layer of the inner surface is superconducting.
It affects the performance of 21, that is, the strength of the electric field 27 that accelerates the charged particle beam 26 (an electron beam is shown as an example in the figure).
That is, the superconducting acceleration cavity 21 having a high niobium purity obtains a high acceleration electric field 27. Among the elements contained in the niobium material, hydrogen is the element that particularly deteriorates the performance of the superconducting acceleration cavity 21. Therefore, the superconducting accelerating cavity 21 is annealed for the purpose of dehydrogenation after the charged particle beam is accelerated in the manufacturing stage or for a long time (generally 1 to 2 years). At this time, in order to perform dehydrogenation more efficiently, hydrogen is adsorbed in the titanium container to increase the purity of the inner surface of the superconducting acceleration cavity 21 and the surface layer of the inner surface. In recent years, this annealing temperature has been increased to 130
When the temperature is raised to 0 ℃, the performance of superconducting accelerating cavity, that is, accelerating electric field
It turns out that 27 gets higher.

(2) As shown in FIG. 5, the superconducting accelerator shown in FIG. 3 is obtained by assembling and integrating a superconducting accelerating cavity 21 and a cryogenic container 22 with a brazing material 31. However, the same members as those in FIG. 2 are denoted by the same reference numerals and the description thereof will be omitted. In this superconducting accelerator, a superconducting acceleration cavity 21 made of niobium (four continuous structure in FIG. 3) is housed inside a cryogenic container 22 made of stainless steel, and a superconducting acceleration cavity 21 made of niobium and a cryogenic container 22 made of stainless steel are contained. The brazing material 31 is used to join the dissimilar metals to maintain airtightness.
The outside of the cryogenic container 22 is covered with a vacuum container 25 for heat insulation, liquid helium 23 is immersed in the cryogenic container 22,
The superconducting accelerating cavity 21 is kept at a cryogenic temperature to maintain the superconducting state.

[0005]

However, the conventional technique has the following problems. (1) In the case of FIG. 2, since the connecting portion secures the airtightness by the flange and the indium material 24, the airtightness is maintained by the deformation due to the thermal strain of the stainless cryogenic container 22 generated during the cooling of the container and the heat cycle. Liquid helium 23 inside cryogenic container 22 damaged
Leaks to the vacuum container 25, and many problems occur that the vacuum heat insulation cannot be maintained, and the equipment is disassembled and reassembled each time to restore the equipment.

(2) As shown in FIGS. 3 and 5, the superconducting acceleration cavity
Since it is impossible to weld the niobium material and the stainless steel material to the stainless cryogenic container 22 by welding, when the brazing material 31 is used, the thermal strain during cooling may be caused by insufficient bonding force at the interface. Due to the deformation and heat cycle caused by the cracks in the brazing material 31, the airtightness of the cryogenic container 22 is impaired. Also, a brazing material 31 for joining dissimilar metals such as niobium and stainless steel
(Generally, gold-based, palladium-based, and copper-based are used.)
Then, the melting point is around 1000 ° C., and the superconducting acceleration cavity 21
Annealing at high temperature (1300 ° C) to improve performance
Since it cannot be performed after the integral assembly with the brazing material, it is difficult to measure the performance of the superconducting acceleration cavity 21 whose performance has once deteriorated.

The present invention has been made in consideration of such circumstances, and a superconducting accelerating cavity made of niobium and a cryogenic container made of titanium are integrally joined by welding, so that cooling or thermal cycling can be achieved. It is an object of the present invention to provide a superconducting accelerator in which the reliability of leaktightness of a joint due to the above is improved and the joint can sufficiently withstand high temperature annealing.

[0008]

The present invention is directed to a superconducting acceleration cavity made of niobium for accelerating a charged particle beam, a superconducting acceleration cavity cooled to a cryogenic temperature, and liquid helium filling the outer periphery of the superconducting acceleration cavity. A superconducting accelerator, comprising: a cryogenic container made of titanium for maintaining a state, wherein the superconducting accelerating cavity and the cryogenic container are integrally joined by welding.

[0009]

In the present invention, the superconducting accelerating cavity made of niobium and the cryogenic container made of titanium are welded and joined,
Compared to flanged joints and brazing material joints, the reliability of Lertite at the joint during cooling and thermal cycle is improved. Further, the melting point of niobium material: 2467 ° C., the melting point of titanium is 167.
Since both of them are high melting point materials at 0 ° C., their joints can sufficiently withstand high temperature annealing at 1300 ° C.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to (B). Here, FIG. 1 (A) is an overall view, and FIG. 1 (B) is an enlarged view of a main part X of FIG. 1 (A).
Reference numeral 1 in the figure is a niobium superconducting acceleration cavity for accelerating the charged particle beam 2. This superconducting accelerating cavity 1 has a structure of 5 stations × 2 = 10 stations, and niobium-made protrusion rings 3 are joined to both ends by welding. A cryogenic container 4 made of titanium is integrally joined to the superconducting accelerating cavity 1 by electron beam welding, with the portion of the ring with protrusion 3 being a groove. In this cryogenic container 4, liquid helium (LH
e) An injection port 5 and a He gas discharge port 6 are provided respectively. An input coupler 7, which is a port for inputting a microwave for accelerating the charged particle beam 2, is joined to the groove portion of the cryogenic container by welding via the ring with protrusions 3. Also, although not shown,
The above-mentioned integrated structure is thermally insulated using a vacuum container or the like. Note that reference numeral 8 in the figure is liquid helium (LHe) filled in the outer periphery of the superconducting acceleration cavity 1.

As described above, the superconducting accelerator according to the above-mentioned embodiment has a structure in which the superconducting accelerating cavity 1 made of niobium and the cryogenic container 4 made of titanium are integrally joined by welding. The number of parts during assembly is reduced, and the number of assembly steps can be reduced. In addition, the reliability of leaktightness at the joint can be improved, and LHe8 during cooling and thermal cycling can be improved.
Can be avoided, and the number of reassembly steps required for restoration can be reduced.

Furthermore, since high-temperature annealing can be performed, the high performance of the superconducting accelerating cavity 1 can be maintained, and the cryogenic container 4 itself can be used as a hydrogen adsorbent during annealing, and a new titanium container can be added to the vacuum annealing furnace. There is no need to prepare it, and the cost of annealing equipment can be reduced.

[0013]

As described above in detail, according to the present invention,
The superconducting acceleration cavity made of niobium and the cryogenic container made of titanium are integrally joined by welding to improve the reliability of leaktightness of the joint due to cooling and thermal cycles, and It is possible to provide a superconducting accelerator that can withstand high-temperature annealing sufficiently and therefore does not need to newly prepare a titanium container in a vacuum annealing furnace and can reduce the cost of annealing equipment.

[Brief description of drawings]

FIG. 1 is an explanatory view of a superconducting accelerator according to an embodiment of the present invention, FIG. 1 (A) is an overall view, and FIG. 1 (B) is FIG.
The enlarged view of the principal part of (A).

FIG. 2 is an explanatory view of a conventional superconducting accelerator, in which a superconducting accelerating cavity and a cryogenic container are integrated by a flange / indium assembly.

FIG. 3 is an explanatory view of another conventional superconducting accelerator,
A superconducting accelerating cavity and a cryogenic container are assembled and integrated with a brazing material.

FIG. 4 is an enlarged view of a main part X of FIG.

5 is an enlarged view of a main part X of FIG.

FIG. 6 is a diagram showing a principle of accelerating a charged particle beam in a superconducting acceleration cavity.

[Explanation of symbols]

1 ... Superconducting acceleration cavity, 2 ... Charged particle beam, 3
… Rings with protrusions, 4… Cryogenic containers, 5… LHe
Injection port, 6 ... He discharge port, 7 ... Input coupler, 8 ... Liquid helium.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuya Seniri 1-1-1, Wadasaki-cho, Hyogo-ku, Kobe-shi, Hyogo Mitsubishi Heavy Industries Ltd. Kobe Shipyard

Claims (1)

[Claims] 1. A superconducting acceleration cavity made of niobium for accelerating a charged particle beam, and a cryogenic cryogenic titanium for keeping the superconducting state by cooling the superconducting acceleration cavity to a cryogenic temperature and filling the outer periphery of the superconducting acceleration cavity with liquid helium. A superconducting accelerator, comprising: a container, wherein the superconducting accelerating cavity and the cryogenic container are integrally joined by welding.