Research and Developments of High Current Joint with Low Resistance at Cryogenic Temperature

开展了低温下低电阻大电流接头的研究与开发。结果表明：(1)研究了接触金属之间的电压降与冷却液温度、接触片压力和/或电流密度的关系。使用残余电阻比大的纯铜对大电流接头是有效的，因为它可以增加热传导，降低焦耳热损失。(2)开发了两种30ka接头母线；一种是埋入SC线的固定Cu母线，另一种是利用NbTi/Cu超导体制成的柔性接头。这些接头母线应用于实验聚变装置LHD的SC馈电系统中。(3)研制了适用于大型超导线圈系统的高Tc超导电流馈线。YBCO块状导体原型的载流试验成功地进行了高达25 kA的载流试验。

Research and developments of the high-current joint with low resistance at the cryogenic temperature have been conducted. The results are concluded as follows : (1) The voltage drop between the contact metals was studied as a function of the temperature of the coolant, the pressure of the contacting pieces and/or the current density. The use of the pure copper with large RRR (residual resistance ratio) is effective for the high-current splices, because it leads to increase of the thermal conduction, and to decrease of the Joule heat loss. (2) Two types of the 30 kA joint bus-bars have been developed ; one is stationary Cu bus-bar embedded of the SC wire, and another is a flexible joint by using NbTi/Cu superconductor. These joint bus-bars are applied in the SC current feeder system of the experimental fusion device, LHD.(3) We have developing the high Tc SC current feeders for the large scale SC coil system. The current carrying test of the prototype of the YBCO bulk conductor was successfully demonstrated up to 25 kA.