Chapter 17: Sapphire-Based SFCL Conductors

We review briefly some of the properties of the superconducting fault current limiter (SFCL) elements prepared on EFG sapphire ribbons. It turns out that high quality YBCO layers can be grown without polishing these ribbons, with a single and thin YSZ buffer layer. SFCL elements comprising a thin Au shunt about 100 nm thick have been tested. The voltage restored upon switching approaches 1 kV/m. The maximum power that can be dissipated without burnout at the time of switching is of the order of 1000 W/cm², 1–2 orders of magnitude larger than that for conventional coated conductors. This allows a large reduction in the amount of conductor necessary for a given device, thus reducing its footprint and eventually its cost.