Current status and prospects of national project on coated conductors in Japan

Three years of the current 5-year national project since 2003, for development of coated conductors using Y-system superconductors have passed and lots of remarkable results have been achieved. In this paper, the current status and the future prospects of the national project are reviewed. The group of Fujikura Ltd. and SRL has worked on the long tape with high performance in the PLD-YBCO superconducting tapes on the IBAD-GZO buffered substrates. The highest I-c x L value of the tape is over 50 kAm, which consists of 212 m in length and 245 A of critical current (I-c). Additionally, a 500 m long IBAD-buffered tape with a reasonable in-plane texture was produced using a large scale IBAD apparatus by Fujikura. In the other group, long tape processings have been developed focusing on lowering its production cost. The extremely high I-c value of 735 A/cm-w was obtained in a short sample by the advanced TFA-MOD method on a CeO2(PLD)/GZO(IBAD)/Hastelloy substrate. In the efforts for the long tape processing, an 86 m long tape with an average I-c value of 300 A by a continuous reel-to-reel system and a 40 m long tape with 155 A by a batch system were realized. One hundred meter class long tapes were also obtained by the MOCVD and PLD-HoBCO processes. Both groups are aiming at the final goals of 500 m long tapes with a high I, value of 300 A/cm-w by and of a production rate of 5 m/h. Furthermore, the feasibility studies for applications using coated conductors have already started according to the above mentioned success of long tape production. Multifilamentarization of coated conductors has been performed for AC loss reduction and it was practically confirmed that a tape with a narrower width results in smaller AC losses not only in short samples but also in a coil winding. Several kinds of coils using long coated conductors such as a solenoid and a pancake types and spiral shaped conductors for the cable were firstly made. Reasonable high performance results were confirmed even in the trials. New approaches on the preliminary studies for the applications of cables, transformers, motors and current limiters, etc. are planned in this project. (C) 2007 Elsevier B.V. All rights reserved.