2G-HTS Wire Research at Faraday Factory Japan

Over the past few years, the world has experienced a steadily increasing demand for high-temperature superconducting wires of the second generation (2G-HTS wires). A significant proportion of wires require the exceptional performance under moderate to strong magnetic fields at reduced temperatures of 4-65K. These wires are primarily used in applications such as fusion magnets, rotating machines, and accelerators. Among these, fusion applications are a key driver for the development and manufacturing of 2G-HTS wires, having specific property requirements at 20K and in 15-20T magnetic fields.<br/>In 2023, Faraday Factory Japan (FFJ) supplied over 2,000 kilometers of 4mm wide wires. The technology utilizes an electropolished Hastelloy substrate, alongside technologies involving the formation of an ion-beam assisted MgO (IBAD-MgO) textured buffer layer and pulsed laser deposition (PLD) of superconducting materials. Our research activities aim at improving the deposition process in all stages of the tape fabrication. This presentation will focus on our current research efforts to enhance the quality of the buffer substrate, improve the performance of superconducting materials in strong magnetic fields, and achieve higher uniformity in the Cu and solder layers. Our results have led to produce wires with an engineering critical current density (Je) at 20K and 20T of approximately 900-950 A/mm², with an average piece length of 350 meters. We will also discuss further practical improvements in our 2G-HTS fabrication process, which includes development of the new equipment, improvement of quality management, and addressing the challenges related to the scaling up of daily production.