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Kyoji Tachikawa

Kyoji Tachikawa

January 5, 1927 to December 7, 2018

December 19, 2018 (PO67).  Kyoji Tachikawa was born and raised in Tokyo, Japan. He received his BEng (1950) and Dr. Eng. (1961), both on Permanent Magnets, from the Faculty of Engineering, University of Tokyo, and joined the scientific staff of the University of Tokyo as a research associate in 1954. His first scientific papers date back to that year and refer to cold working studies of permanent magnet alloys and later on to high-C and high-Zr steels. In 1962 Tachikawa moved to the National Research Institute of Metals (NRIM) in Tsukuba, where he spent almost his entire scientific career until his “first” official retirement in 1987. He began there as the Head of the Electric and Magnetic Materials Laboratory in 1962, became Director of the Electric and Magnetic Materials Division in 1974, Director of the Superconducting and Cryogenic Materials Division in 1980, and Director of the entire Tsukuba Laboratories in 1985.

His first paper on superconducting materials appeared in 1964 and dealt with the Nb-Zr system. Only three years later he developed V3Ga tapes with a very attractive high-field performance using Cu as a catalyst for the diffusion reaction. Again, three years later, he made an epoch-making invention of the so-called bronze process enabling the production of multifilamentary type V3Ga conductors starting from V/Cu-Ga composites. He constructed the first magnet wound from multifilamentary type A-15 conductors in 1974, which was quite stable under time-varying fields. The bronze process was then successfully applied to the production of multifilamentary Nb3Sn conductors, a workhorse for present-day high-field applications of superconductivity. The next seminal improvement came in 1982 when he developed Nb3Sn conductors, doped by a few at% of Ti, which is incorporated into the Nb3Sn layer and enhances the upper critical field from 20 to 25 T at 4.2 K by the mean-free-path effect. These materials are being used for one of the most demanding magnets ever designed, i.e. the toroidal field coils of the ITER nuclear fusion device.

After his retirement from the Tsukuba Laboratories, Tachikawa started his second career as a full professor at the Faculty of Engineering of Tokai University in April 1987. Substantial improvements of the A-15’s by new processing techniques, the development of other high-field superconductors, such as V2Hf, the development of ultra-thin filaments for ac applications, substantial contributions to the processing of Bi and Tl-based high temperature superconductors, and finally research on the enhancement of critical currents in MgB2 superconductors represent the highlights of Tachikawa’s work in “retirement”.

Professor Tachikawa’s scientific achievements are documented by four books and the editing of seven conference proceedings, around 400 scientific publications in refereed journals (among them 47 in CEC/ICMC Proceedings), and frequent seminar and conference presentations all around the world. He spent sabbaticals at the Francis Bitter National Magnet Lab at MIT, the University of Lausanne in Switzerland, and the University of Wisconsin at Madison. Numerous awards and honors bear testimony of the esteem and the international reputation gained by Tachikawa over the years, among them numerous best paper awards from the Japan Institute of Metals and from ICMC, the National Decoration from the Emperor of Japan in 1997, and the Prize for Distinguished Achievements in Research from the Cryogenic Society in Japan in May 2008. In 2000, along with Prof. David Larbalestier, he was one of the first two recipients of the award for lifetime achievement in Materials from the IEEE Council on Superconductivity Additionally, in 2009, Prof. Tachikawa was the third ever recipient of the ICMC Lifetime Achievement Award. The citation read: “The Lifetime Achievement Award for his outstanding work and contributions to the science and technology of superconducting materials achieved during a distinguished career is presented to Kyoji Tachikawa”.