PSFC/JA-99-13 Options for the Use of High Temperature Superconductor in Tokamak Fusion Reactor Designs

The application of high temperature superconductors in long term tokamak fusion reactors is analyzed in this paper. Properties of high temperature superconductors have been well documented that make them ideal for this application. Short-sample BSSCO wires and YBCO tapes approach their single-crystal performance limits. This provides a useful reference frame as well as a starting point of what may be possible in the future. In this paper, the design issues involved in the use of this technology for tokamak magnet applications will be investigated by extrapolating the properties of short sample YBCO thick films to longer lengths. The properties of YBCO operating at elevated temperatures (> 10 K) are also summarized. The limitations imposed on the performance and lifetime of the HTS materials because of the fusion environment are reviewed. The consequences of implementing the HTS design requirements in a fusion environment are then described. The HTS material may offer an opportunity for a fundamentally different magnet approach leading to either a lower cost or reduced maintenance. High field toroidal magnets with decreased shielding and with better access and easier maintenance may be feasible.