Development of superconducting joint for TOKAMAK feeder busbar

• Published in: Fusion engineering and design 2019-01, Vol.138, p.41-47
• Main Authors: Rong, Jian, Lu, Kun, Zou, Chunlong, Wen, Xinjie, Song, Yuntao, Yang, Haojun, Huang, Xiongyi
• Format: Article
• Language: English
• Subjects: AC losses; Busbars; Cables; Copper; Indium; Insulators; Lap joints; Plasma currents; Plasma physics; Resistance; Sub-cable overlap joint; Superconductivity; Temperature rise; Tokamak devices
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2018.11.005

In this study, we improved twin-box joint, for smaller volume, lower resistance and more uniform tension insulators, a sub-cable overlap joint design was proposed. For sub-cable overlap joint resistance calculation, a model for joint resistance calculation was developed, the resistance of twin-box joint was calculated 0.201 nΩ, which was close to the test resistance, thus the model was acceptable, and the resistance of sub-cable overlap joint was calculated 0.0776 nΩ. A model was developed for AC losses calculation of two type joints, AC losses of sub-cable overlap joint were smaller than that of twin-box joint. Thermo-hydraulic simulations of the respective busbar cables with twin-box joints and sub-cable overlap joints were carried out with THEA code in 15 MA reference scenario, the temperature margin of busbar with sub-cable overlap joints was high than that with twin-box joints, and the temperature rise added by sub-cable overlap joints was lower than that value added by twin-box joints. [Display omitted] •Improved twin-box joint, for smaller volume, lower resistance and more uniform tension insulators, a sub-cable overlap joint design was proposed.•Developed a model to calculate resistance of twin-box joint and sub-cable overlap joint.•Developed a model to calculated AC losses of twin-box joint and sub-cable overlap joint.•Analyzed busbar cables with twin-box joints and sub-cable overlap joints in 15 MA reference scenario, calculated temperature margins of cables with two type joints, and calculated temperature rises of cables added by two type joints. Typically, the superconducting busbar of TOKAMAK feeder system is divided into different segments, which are connected by superconducting joints. ASIPP (Institute of Plasma Physics, Chinese Academy of Sciences) feeder team has improved the twin-box for ITER (International Thermonuclear Experimental Reactor) feeder systems. In the twin-box joint, the two cables were connected by two compressed against copper soles, and the pure indium was used as solder. For superconducting joint improvement, ASIPP feeder teams design a sub-cable overlap joint with smaller volume, lower resistance and more uniform tension insulators. In the sub-cable overlap joint, the cable is untwisted at the sub-cable stage, and sub-cables of two cables are connected by indium-coated copper soles. A brief analysis including resistance, AC losses and temperature rise produced by joints of the respective busbar with twin-box and sub-cab