JPH01191501A - Joint method for superconducting waveguide - Google Patents

Abstract

PURPOSE:To obtain a uniform surface without defect by inserting a metal having a lower melting point than that of a superconducting material between joint faces of the superconducting waveguide, pressing the metal and bonding the faces with diffusion under vacuum or inactive gas atmosphere. CONSTITUTION:A thin tin plate 2 as an insert metal is clipped between joint faces being flange end faces, each being one of two cavity single bodies 1 made of niobium opposite to each other, flanges 5 are tightened by using a bolt 3 and a nut 4 to press the thin tin plate 2 between the end faces, and the joint body 6 being the result of incorporating the two cavity single bodies is heated for 3 hours at 600 deg.C. Then the surface is chemical-polished by using a mixture of liquids comprising hydrofluoric acid, nitric acid and phosphoric acid for finish. Since atoms of both are diffused mutually at the contact part between the insert metal and the superconducting material in this way, the joint is attained in a short time and the defect of surface is avoided.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides waveguides for microwave transmission, particularly disk-load type traveling wave accelerator tubes, microwave cavity co-containers, etc., using superconductors. The present invention relates to a method for connecting superconducting waveguides formed to reduce microwave power loss.

(Prior technology) Disc-load type traveling wave tubes and cavity resonators are microwave amplifiers such as klystrons and electronics.

It is used as a 7Jtl detector for particles such as protons. Unlike simple waveguides, these special three-dimensional circuit components store more microwave energy, and since it is not possible to reduce power loss sufficiently with copper, aluminum, etc., they are made with superconductors. is proposed. In other words, since the surface resistance of a superconductor is much smaller than that of a normal conductor, it is expected that a high electric field can be generated with a small amount of electric power.

For example, as shown in Figure 2, a superconducting resonator as such a waveguide is made by constricting the axial center of a cylindrical superconducting material and making a through hole (7) with a small cross-sectional area inside. established,
A plurality of hollow bodies (1) each having a flange (5) with a plurality of bolt holes (8) drilled in the circumferential direction on the outer periphery of both ends are prepared by cutting, etc., and these empty shoulder blades (1) are Joint surface (9)
Tighten the respective flange end faces closely together with bolts (3) and nuts (4),
1G) are fixed by electron beam welding or TIG welding, and a plurality of these single cavities (1) are connected.

A superconducting state is achieved and maintained by immersing such a waveguide in liquid helium, or by closely adhering a pipe through which liquid helium passes to the outer circumferential surface of the waveguide.

(Problems to be Solved by the Invention) However, such a superconducting waveguide cannot actually obtain as high an electric field as expected.

This is mainly due to surface defects on the inner wall of the waveguide. Even if the waveguide is a superconductor, it generates heat due to the presence of some resistance in the microwave, but this heat is usually removed by liquid helium, which is immersed in the waveguide to maintain it in a superconducting state. be done. However, if there is a surface defect, the surface resistance increases in that area, and a large amount of heat is generated locally, which becomes the starting point for the superconducting state to be destroyed. Such surface defects are particularly likely to occur at bonded parts. That is, for example, for joining superconducting waveguides made of simple niobium, electron beam (electron beam) welding is usually used.

However, with this method, weld beads may occur at the joint,
Since thermal distortion occurs near the joint, it is necessary to remove the thermal distortion by grinding or annealing the bead after welding, and it is difficult to obtain a uniform surface without defects.

In this way, the method of joining superconducting waveguides has been a hindrance to its practical use.

(Means for deciding if/I') In view of this, the present invention is the result of various studies and has developed a method for joining superconducting waveguides with fewer defects. In a method of manufacturing a superconducting waveguide by joining a single cavity or a plurality of single cavities whose inner surfaces are formed of a superconducting thin film, a metal having a melting point lower than that of the superconducting material is inserted between the joining surfaces. This method is characterized in that the single cavities are diffusion bonded to each other by being compressed and then heated at h0 in a vacuum or an inert gas atmosphere.

(Function) In this way, a metal with a melting point lower than that of the superconducting material is inserted between the bonding surfaces, compressed, and heated to cause the atoms of both to be heated at the contact area between the metal (hereinafter referred to as the insert metal) and the superconducting material. Using the diffusion bonding method, which involves bonding by mutually diffusing and alloying, it is possible to bond at a lower temperature and in a shorter time than simply diffusion bonding two superconducting materials, and the surface of the bonded part is smooth and continuous. This is because it has the advantage of eliminating defects.

The heating temperature is preferably near or above the melting point of the insert metal and below the melting point of the superconducting material.

(Example〕 Next, examples of the present invention will be described.

As shown in Fig. 1, a thin tin plate (2) is inserted as an insert metal between the joint surfaces of two niobium hollow bodies (1), each with one of the seven flange end faces facing each other.
), the seven flanges (5) are tightened with nuts (4) to compress the thin tin plate (2) between the joint surfaces, and then the connecting body (6) that integrates the two single cavities is vacuumed. 600°C inside
It was heated for 3 hours. Thereafter, the surface was chemically polished using a 1:1:1 mixture of hydrofluoric acid, nitric acid, and phosphoric acid. The characteristics of such a connected body in a superconducting state were investigated, and it was found that it had the same characteristics as that of the above-mentioned connected body having no joints and whose inner surface was completely finished by cutting.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to bond single cavities at relatively low temperatures, so there is little deterioration or defects in the base material, and it is possible to produce high-quality superconducting waveguides, especially superconducting cavity co-containers. It has significant industrial effects such as improving productivity.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a joined state of an empty 111iil core according to an embodiment of the present invention, and FIG. 2 is a partially sectional side view showing a conventional example. 1... Single cavity 2... Thin tin plate 3... Bolt 4... Nut 5... ...Flange 6...Connection body 7...Through hole 8...Bolt hole 9...Joint surface 10...・・・・・・Joint part diagram 1

Claims (1)

[Claims] (1) In a method of manufacturing a superconducting waveguide by joining a single cavity formed of a superconductor or a plurality of single cavities whose inner surfaces are formed of a superconducting thin film, the above-mentioned A method for manufacturing a superconducting waveguide, which comprises inserting and compressing a metal having a melting point lower than that of a conductive material, and then heating the cavities in a vacuum or an inert gas atmosphere to diffusion bond the cavities to each other.