Speaker
Description
The High-Temperature Superconducting (HTS) magnet is being developed for the fusion reactor magnets. One of the options for the large-current HTS conductor is a simple stacking type in which REBCO tapes are stacked without twisting or transposing.
The Stacked Tapes Assembled in Rigid Structure (STARS) conductor has been developed at the National Institute for Fusion Science (NIFS) since 2007. A stack of REBCO tapes is embedded in a copper stabilizer and a stainless-steel jacket sealed with laser-beam welding. A 20-kA-class conductor sample was successfully tested in a 6-m long, 3-turn coil configuration in an 8-T magnetic field and 20-K temperature. While it is possible to wind this conductor into a three-dimensional (3-D) shape by plastically deforming the stainless-steel jacket, the “Joint-Winding” method with a prefabricated jacket and a mechanical bridge-type lap joint facilitates an on-site winding of large coils. Non-uniform current distribution in the stacked tapes is analyzed by numerical simulation, which shows good comparison with experiments. The internal electrical insulation is helpful to be used in case of a fast coil discharge.
The Wound and Impregnated Stacked Elastic tapes (WISE) conductor has been developed at Helical Fusion (HF) through a public-private partnership with NIFS. An on-site 3-D winding is easy due to its flexibility, and later the winding conductors will be mechanically fixed by impregnation using low-temperature melting metal to form a non-insulation coil. A transport current of 40 kA has been achieved at 8 T, 20 K with a hairpin-shape conductor sample tested at NIFS. A double pancake coil is planned to be fabricated and tested in 2025. Another type of low-resistive mechanical lap joint is also being developed for this conductor.
