The Research Of Key Technology Of The East Low Temperature Superconducting Busbar

EAST superconducting tokamak is made up of the ninth five-year plan of the national important scientific project. Its scientific goal is to build a large-scale superconducting tokamak device. Construction of the EAST has very important scientific significance. It is not only a full superconducting tokamak, But also improving the plasma constraint conditions of large elongated non-circular cross-section of the plasma position. The completion of EAST make our country become the world’s few countries which have this type superconducting tokamak device. It also keep our country still into the world frontier through the magnetic confinement fusion research.So far, EAST devise have plasma discharged more than tens of thousands of times. Along with the plasma operation parameters gradually increased. The existing high temperature superconducting current lead can not satisfied the next current operation requirements. The current vacuum partition has been insufficient strength margin. In order to maintain and repair the problems which have been found, Ruled out safety factors of the devices at the same time. Decided to move current lead to the New power hall which 30 meters away from the EAST hall. So we need a new Low temperature superconducting transmission line. One connect the EAST device and the other connect Current lead tank. Superconducting joint bearing two important tasks, one is to connect the electric circuit and the other is the cooling circuit. It is widely concerned that the superconducting joint has been as a crucial technique in EAST superconducting transmission lines.This paper main describe the superconducting joint double box lap structure. Using the theory of resistivity and resistance of the conversion formula to estimate the dc resistance of superconducting joint. Using Faraday electromagnetic induction principle to estimate the eddy current loss. Using the Bernoulli equation to estimate the helium flow pressure drop of joint box. It is concluded that the superconducting joint of electrical performance is mainly affected by the dc resistance. After the further analyzed of the dc resistance of the superconducting joint. It is concluded that the composition mainly has three part. The resistance of the copper base plate. The second one is the joint box superconducting cable and connector box copper contact resistance. The third one is the connection resistance between the two joint boxs. The first part of the resistance value mainly decided by the material itself. The second and third parts resistance is closely related to the choice of manufacturing process.The manufacturing technology of superconducting joint. Removing nickel layer on the surface of the superconducting cable Adopt through the mechanical polishing method or the electroplating method. Through plating tin or plating silver on the surface of nickel, improving the connection between the superconducting cable and copper. Connecting two joint box by brazing method. Reducing the contact resistance between the two joint boxs. We make a reasonable process procedures by optimizing the technical parameters of solder. The result is that the contact resistance between superconducting cables and copper effectively reduced. Reasonable superconducting joint processing technology has provided the safeguard for superconducting joint electrical performance.The test results show that the dc resistance is about 4.9nQ between the superconducting cable and copper. It is fully meeting the design requirements of EAST dc resistance is less than 10nΩ. The results solved Key technical problems of superconducting line and improved the EAST device running stability. It has an important value in Superconducting electrician and fusion nuclear energy. Author:Zhang Zhirong (School of Mechanical and Automotive Engineering)...