Research on a novel HTS double pancake coil based on CORC: used for kA-level SMES of accelerator

Abstract

Large-scale complex needs high performance SMES system with 5 kA-level current carrying and kA s−1 current ramping rate (such as particle accelerator complex), the inductance of which should be as small as possible (≪1 H) to reduce the terminal voltage and realize ideal energy evacuation. This paper introduces the world’s first application of double pancake (DP) coil with conductor on round core cable (CORC) cable, which can be a unit of MJ-level SMES system with a total inductance of 125 mH and 4 kA current carrying (@30 K, 4 T). The combination of low inductance and high current capacity guarantee the safety during kA s−1 operating condition. The CORC wound with highly anisotropic YBCO tape can realize quasi-isotropy with critical properties. The performance of the CORC with 11 layers and three tapes in each layer has been fully validated with excitation test at 77 K and the critical current can reach 2906 A at 77 K, self-field. The skeleton of the DP coil is specially designed with semi-circular spiral groove and the climbing-layer area is supported by two symmetrical blocks, which can provide reasonable support to the CORC cable. The measured critical current of DP coil can realize 1750 A at 77 K (theoretical value is 1800 A). It means that the coil winding method is feasible to avoid performance degradation during winding. The DP coil based on CORC cable is fully suitable for the SMES system which needs to realize ∼4 kA current carrying and fast energy conversion. It also provides a good practice for the engineering application of CORC cable.