Multifilament coated conductors are intrinsically inferior to monofilament coated conductors from the viewpoint of the robustness against quench / thermal runaway. When one filament of a coated conductor becomes normal, inter-filament current sharing is essential to reduce Joule heating and to prevent the entire coated conductor against burn-out. We experimentally studied normal transition characteristics of multifilament coated conductors from the two points of view: 1. Static inter-filament current sharing when increasing transport current slowly; 2. Dynamic inter-filament current sharing during quench process.

Both experiments were carried out in a conduction-cooled cryostat, in which temperature can be controlled to be 10 – 70 K. A coated conductor was attached onto a GFRP sample holder, which was installed in the cryostat. Magnetic field (m₀H up to 5 T) can be applied perpendicular to wide face of tape-shaped coated conductor. A current was supplied to the coated conductor through copper terminals soldered at the ends of the coated conductor.

With respect to static inter-filament current sharing, currents in filaments are not always same due to the different contact resistances between copper terminals and filaments. Also, critical currents of filaments are not always same. When the current in one filament exceeds its critical current, static inter-filament current sharing occurs through the copper plated over filaments. We attached pairs of voltage taps across the width of the coated conductor in order to measure the transverse voltage caused by the current sharing. The current supplied to the sample was increased slowly and measured by the longitudinal and transverse voltages. With respect to dynamic inter-filament current sharing, similar voltage measurements will be done when quench is initiated by a small resistive heater with which we can apply local and transient thermal disturbance.