Options for the use of high temperature superconductor in tokamak fusion reactor designs

The use of high temperature superconductors (HTS) in long term tokamak fusi on reactors is analyzed in this paper. The well-documented physical al prop erties of high temperature superconductors are used in the evaluation. Shor t-sample wires and tapes of Bi2Sr2CanCun+1Oy. materials, with n = 1, 2 (ref erred to as BSCCO), and YBCO (YBa2CuO7-x) tapes approach their single-cryst al performance limits. They provide a useful reference frame as well as a s tarting point of what may be possible in the future. In this paper, the des ign issues that arise when this technology is used in tokamak magnet applic ations will be investigated by extrapolating the properties of short sample YBCO thick films and BSCCO tapes to longer lengths. The properties of YBCO operating at elevated temperatures ( > 10 K) will also be summarized. The limitations imposed on the performance and lifetime of the HTS materials be cause of the fusion environment will be reviewed. The consequences of imple menting an HTS configuration in a fusion environment will then be described . The use of I-ITS material may offer an opportunity for a fundamentally di fferent approach to magnet design and construction leading to either lower cost or reduced maintenance. Reduced cost magnets requiring decreased shiel ding, with better access and easier maintenance may be feasible. (C) 2001 E lsevier Science B.V. All rights reserved.