Fusion supercondcucting magnet development in Japan started in 1976 as it also did in Western countries. After a quarter-century, 13T was successfully achieved in a bore of 2m and in pulsed operation for plasma current transformer in JAERI (Japan Atomic Energy Research Institute). Thus it is a good occasion to describe the chronological evolution of the development work in order to transmit this history to the 21st century. After explanation of the Japanese circumstances around 1970 in cryogenic and high field technologies, the paper introduces the technical report, published in 1977 by section of superconducting magnet of the Fusion Council, on the development of tokamak magnet system for experimental reactor. The each decision making of every step in the real projects evolved later is described here. The international collaborations and the application of resulting techniques to new facilities in other laboratories are represented.

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The design and development of the International Thermonuclear Experiment Reactor (ITER) have been under way since 1992, based on the international agreement of the Engineering Design Activities (EDA). The design of the main machine and the development of key components were successfully completed by July 2001. The technical specifications of the ITER machine are being prepared for the order of its fabrications in the Coordinated Technical Activities (CTA). The construction of ITER is expected to start by 2005. The ITER machine uses superconducting coils to confine and shape the plasma, and the coil system must be reliably operated to perform the plasma experiment. The system accounts for 28% of the direct ITER capital costs and requires a long manufacturing period (6 years and 6 months). The strand for the superconducting conductor is the first procurement component in the ITER. This paper explains the present design and status of the ITER project and its superconducting coils.

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The recent developments of superconducting magnet technology allow us to construct a small and medium-scale SMES (Superconducting Magnetic Energy Storage System), which would be effectively used for electric power management and quality control because of its high convergence efficiency and its simultaneously quick response of real and reactive power. Since a SMES of this kind should be situated in a power substation or near a demand site, a stray field from superconducting coils restricts its use. The stray field outside a solenoid is analyzed by a series of Legendre polynomials; therefore the results are applied to various coil configurations. We derived the stray fields from various SMES configurations as a function of R_p, where R_p is distance from the coil. In this paper we analyzed the stray fields from single solenoid coil and toroidal coil arrangements, as functions of stored energy E and maximum magnetic field B_m, which are the main parameters of superconducting coil. The stray field from the single solenoid coil configuration decreases as E/B_m, and that from the toroidal coil configuration decreases as (E⁽ⁿ⁺²⁾/B_m⁽²ⁿ⁺¹⁾)^1/3, where n is the number of coils.

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