NIFS-445

FULL TEXT (PDF, 544 KB)


Author(s):

O. Motojima, N. Yanagi, S. Imagawa, K. Takahata, S. Yamada, A. Iwamoto, H. Chikaraishi, S. Kitagawa, R. Maekawa, S. Masuzaki, T. Mito, T. Morisaki, A. Nishimura, S. Sakakibara, S. Satoh, T. Satow, H. Tamura, S. Tanahashi, K. Watanabe, S. Yamaguchi, J. Yamamoto, M.Fujiwara and A. Iiyoshi

Title:

Superconducting Magnet Design and Construction of LHD

Date of publication:

Sep. 1996

Key words:

Large Helical Device, LHD, currentless toroidal system, superconducting coil, helical coil, poloidal coil, SC bus line, divertor, disruption free system

Abstract:

The Large Helical Device project is now successfully executing its 7th year program of 8 years construction period. Superconducting (SC) Research and Development tasks for the LHD SC coil construction have been already completed, and we have now accomplished more than 75% of the whole construction schedule. In this paper, we report the recent progress of SC R&D obtained, and the fabrication technology developed for a huge and reliable SC coil systern. These results are applicable to a future experimental reactor In the next decade with a much larger SC coil system. The LHD is called heliotron and has l/m = 2/10 SC helical coils and three sets of SC poloidal coils, of which coil currents are 7.8 MA, 5.0 MA, -4.5 MA, and -4.5 MA, respectively. The major radius, minor helical coil radius, minor plasma radius, and plasma volume are 3.9 m, 0.975 m, 0.5~0.65 m, and 20~30 m^3, respectively. In addition to an SC coil system, the main body of the LHD consists of huge supporting structures for the electromagnetic force, a vacuum chamber, an outer cryostat, and a machine base. The total weight is about 1,500 tons, in which LHe cooled mass is 850 tons. The LHD has a maximum stored energy of 1.6 GJ (4 T at the plasma center). The major goal of the LHD project is to demonstrate the high potentiality of the helical-type device producing currentless-steady-state plasmas with an enough large Lawson parameter in absence of any danger of a plasma current-disruption. It provides a useful and reliable data base making it possible to predict a fusion reactor condition. The realization of the steady-state operation requires a large extent of engineering innovations, primarily in the areas of superconducting technology, plasma facing materials and water cooling systems, and heating systems. It also contributes to building up the engineering scenario required for a long-pulse regulated plasma operation necessary for the fusion research.

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