Preliminary Tests and Margin Estimate for a REBCO Insulated 10 T Insert under High Magnetic Field

Our project is to build a high-temperature superconductor (HTS) insert generating 10 T in its center and expected to work inside a 20 T background field. In the first step, the background field is provided by a resistive magnet to avoid major coupling issues. Nevertheless, the final goal is to have the insert operating inside an LTS magnet to yield a 30 T-class all-superconducting magnet. The insert is designed as a stack of pancakes and double pancakes wound with REBCO tapes. Preliminary tests are performed on a deposited polyimide insulated coil, although design has started with metallic-insulation coils. This paper presents results obtained on a double pancake insulated HTS coil that was tested inside both a resistive coil at LNCMI and a superconducting magnet at Tohoku University. The electrical and mechanical behaviors of the sample coil are discussed, and margins are estimated taking into account the field distribution on each point of the coil. Results are encouraging as the coil passes 370 A (82.9% lc) self-field and 260 A (68.6% lc) under 8 T. Moreover, the coil is still working even after the outer magnet quench.