JPH01130890A - Method for joining superconducting wave guides - Google Patents

Abstract

PURPOSE:To perform continuous diffusion joining with a smooth joining state without the change in quality of material on joining parts by pressing joining faces mutually and heating these at the temperature lower than the melting point of materials in a vacuum. CONSTITUTION:Two hollow single substances 2 and 2 of hollow resonators with both end faces opened having wall through holes 1 on the central part narrowed down toward the center of a circular cross section from the outside peripheral surface on the central part in the axial direction are manufactured from niobium rods. Annular flanges 3 and 3 are formed integrally on the outside peripheries on both ends of the hollow simple substances 2 and the squareness and flatness on the joining faces 4 of the flanges are finished with high accuracy and the surfaces are cleaned by fluorine and further, eight bolt holes 5 are provided at equal intervals on the flanges 3 and 3 and the joining faces 4 of one side of the two hollow substances 2 and 2 are pressed and fixed mutually by a bolt 6 and a nut 7. A connector 8 of these hollow resonators is at in a vacuum furnace and heated for one hour at 1500 deg.C with the degree of vacuum of 10<-5> Torr. The inside structures in the vicinities of the joining faces which are subjected to diffusion joining by this method are not changed and are homogeneous.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to waveguides for microwave transmission, particularly to ordinary waveguides such as disk load type waveguides and microwave cavity resonators. The present invention relates to a method of joining superconducting waveguides that can store a relatively large amount of microwave energy therein, and particularly reduces microwave power loss on the inner wall surface of the tube.

[Conventional technology]

The above-mentioned waveguides and cavity resonators are used as microwave amplifiers such as talistrons and particle accelerators for electrons, protons, etc.; An accelerator tube with a plurality of connected body resonators is used.

However, when storing microwave energy such as in a cavity resonator used in a particle accelerator, there is a large energy loss due to the electrical resistance of the tube wall, so the energy input to the microwave must be increased accordingly. There was a problem that efficiency was low.

In order to deal with this (recently, we have created a cavity as a cavity resonator that can obtain a large accelerating electric field with an extremely small amount of microphone power and a superconducting material, or Cavity resonators made by plating conductive materials are attracting attention.

With such a superconducting cavity resonator, the surface resistance of the inner wall surface of the cavity is very small, so it is expected that a very high Q value and a high electric field can be obtained compared to a normal conductive cavity resonator. .

[Problem that the invention seeks to solve]

However, such a superconducting cavity resonator cannot actually obtain an electric field as high as expected.

This is mainly due to surface defects on the inner wall surface of the cavity. Although this is a superconductor, there is a slight electrical resistance to microwaves, so it generates heat.
Normally, this heat is taken away by liquid helium, which maintains a superconducting state. However, if the above-mentioned surface defects exist, the surface resistance increases in those areas, and a large amount of heat is generated locally, which becomes a starting point and destroys the superconducting state. In general, such defective parts emit more electrons (field emission) under a high electric field than other parts, which can lead to destruction of superconductivity.

The above-mentioned surface defects include surface oxides, pinholes, etc., but the joint portion of the cavity resonator is particularly problematic. In other words, due to the difficulty in manufacturing the cavity as a single resonator, it is divided into many parts and joined together by electron beam welding or TIG welding, but these joining methods have many defects. Because it is easily introduced, the material changes in the joint and its heat-affected zone, resulting in non-uniformity in the material at the joint.
Another problem arises in that the superconducting properties change.

Means for Solving Problem C] In view of this, the present invention has conducted various studies, and has discovered that it is possible to use a technique for bonding materials by vacuum heating in a state where they are pressed together without any gaps, that is, a diffusion bonding technique. As a result, we developed a method for joining superconducting waveguides that can withstand high electric fields by eliminating surface defects caused by non-uniformity of the material at the joint.
A method for joining waveguides made of superconducting materials to each other, which is characterized by diffusion joining by pressing their joining surfaces together and heating them in a vacuum at a temperature lower than the melting point of the materials.

[For production]

According to diffusion bonding, in which the joining surfaces of waveguides are pressed against each other and the atoms on both sides of the joining surfaces are diffused into each other at a temperature below the melting point of the materials, there is no deterioration of the material at the joining part. This is because the bonded state becomes smooth and continuous, and good superconducting properties are maintained without surface defects.

The reason why the process is carried out in a vacuum is because if oxides or the like are generated or foreign substances are absorbed on the bonding surface, diffusion at the bonding surface will be hindered. .

Also, a cavity resonator, which is a type of waveguide with a structure in which disks with a through hole formed in the center are periodically provided in the longitudinal direction of a waveguide with a circular cross section, and a disk load-type traveling wave type. In the case of joining accelerator tubes, it is most effective to join the joint where the electric field is the smallest, that is, between the deck and the disc. This is because the electric field rises as more energy is stored in the cavity formed by the disks and the single disk, and is greatest at the center of the cross-section of the cavity and smallest at the outermost side of the cross-section. And this 9
The larger the electric field, the greater the field and emission from the air conditioning surface, and the more electrons fly out, taking away some of the energy and becoming one of the causes of lowering the electric field reaching the cavity. Furthermore, since the number of ejected electrons m increases as the cavity surface becomes rougher, it is undesirable to form a portion such as a bonding portion where the surface uniformity may be inhibited in a location where the electric field is strong.

〔Example〕

The present invention will be explained using an example.

A niobium rod has a cylindrical shape as shown in Figure 1, with both end faces open, and the central part in the axial direction narrows from the outer peripheral surface toward the center of the circular cross section, and has a small hole (1) passing through the central part. Two single cavities (2) and (2) of the cavity resonator were manufactured. A ring-shaped flange (3) C is provided on the outer periphery of both ends of the hollow heavy body.
3) are integrally formed, and the joint surface (4) of the flange is finished with high precision for squareness and flatness, and the surface is cleaned with hydrofluoric acid. By drilling several bolt holes (5), the two cavity carriers (2) (2) are pressed against each other by pressing one joint surface (4) of the two together with the bolt (6) and the seat (1). Fixed. The connected body (8) of the cavity resonators was placed in a vacuum furnace and heated at 1500° C. for 1 hour under a vacuum of 10 −5 torr.

In the vicinity of the joint surface where diffusion bonding was performed in this way, there was no change in the internal structure as in welding, and the structure was extremely homogeneous, and the superconducting properties were the same as those in the non-bonded area.

It is to be noted that it is most effective to perform the bonding of a single cavity at a portion of the cavity where the surface electric field is the smallest, since the influence of the bonding can be minimized.

〔Effect of the invention〕

As described above, according to the present invention, defects in the joints of superconducting waveguides and cavity resonators are extremely reduced, energy loss is extremely small, and therefore a high accelerating electric field can be obtained, which has remarkable industrial effects. It is.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a partial side cross section of an embodiment of the present invention. 1...Small hole 2...Single cavity 3...Ring-shaped 7 flange 4...Joint surface 5... ...Bolt hole 6 ...Bolt 7 ...Nut 8 ...Connection body

Claims (1)

[Claims] A method of bonding waveguides made of superconducting materials to each other, characterized in that diffusion bonding is performed by pressing their bonded surfaces together and heating them in a vacuum at a temperature lower than the melting point of the materials. How to join pipes.