Low Resistance Soldering and Installation for a kA Level HTS Flux Pump

The HTS flux pump is a promising device which can charge the HTS magnet for various high field applications. In an HTS flux pump, the superconducting tapes are the circuit connections between the charging loop and the load circuit, and using soldering joints between the superconducting layers is a general method. For a large scale HTS flux pump, the joints should endure the electrical current over kA level, and with durable mechanical structures. In our kA level HTS flux pump, the HTS-copper joint was used to connect the charging loop, the HTS bridge and the potential HTS load. Three methods of HTS-copper soldering were tested and compared for a simple HTS-copper circuit: pure indium wire pre-tinning, IN52/SN48 ribbon direct soldering, and IN52/SN48 ribbon pre-tinning. Experiments show the soldering of IN52/SN48 ribbon pre-tinning archived the lowest joint resistance among these three methods, and the individual resistances were determined. This method was used to solder the joint for the kA level HTS flux pump, and acceptably low resistance was achieved.