The Superconducting Revolution

Phase 4

Towards further technological evolution.

Japan surpassed the United States by extending the cable length by 100m, and became the world leader in IcL value, the product of critical current and length.

In 2004, Fujikura was preparing to create the world's first 100m-long wire with a critical current of over 100A. That year was also the year of the Applied Superconductivity Conference, an international conference on superconductivity held every two years. As this conference attracts many superconductivity researchers, the company planned to present the results of the 100m-long wire at the conference, and began preparations in July. To create a superconducting wire, it is necessary to deposit an intermediate layer, a superconducting layer, and a stabilizing layer, and then to carry out heat treatment. The deposition equipment at the time was small-scale and had low output compared to today's equipment, so it took more than two months to complete the entire process.

Just as they were about to complete the intermediate layer and form the superconducting layer, a critical part in the excimer laser they were relying on broke down. They inquired about the same part to the manufacturer's agent and other research institutes, but they couldn't find it anywhere. Just when it seemed all was lost, they had an idea that they could somehow make 100m of wire by using the excimer laser they had been using for basic experiments. However, this method would require not only moving the position of the laser, but also re-installing the piping for the laser's raw gas and the cooling water piping. Counting backwards from the date of the conference presentation, they only had a few dozen hours to complete the work. Fujikura's engineering team immediately took measurements on the spot, and construction began the next morning. They prepared the paper for the conference presentation so that they only had to enter the characteristic values at the end, and they ended up obtaining the characteristics of the superconducting wire two days before the conference presentation, and successfully made it to the conference.
At the time, a project had just begun in the United States with the goal of developing a 100m superconducting wire in four years. When they heard from Japan that their goal had been achieved, American researchers could hardly believe their ears. Unbelievable! It is not hard to imagine that this caused considerable jealousy and resentment.

Six months after developing the 100A, 100m superconducting wire, Fujikura started developing a 200A, 200m long wire. They faced many difficulties, but overcame them all. They achieved a 200m long wire in 2006. The NEDO project was to develop a 300A, 500m long wire by the end of 2007. Fujikura then set out to lengthen the superconducting layer as a challenge, and through trial and error. They worked on the first wire production in the summer of 2007, and as a result, they established the basic production technology for long wires. The continuous length was 368m, exceeding 300A, and the lowest critical current was 305A. Incidentally, the IcL value, which is the product of the critical current and length, was 112,000A. It took only four months, but they maintained their position as the world's best. After that, they continued to refine the manufacturing process of the superconducting layer to improve the superconducting properties, and after forming an intermediate layer, they finally completed a 500m superconducting wire. The critical current for the entire length was 350A over 504m. The IcL value at this time was 176,000A, once again taking the number one spot in the world.