Investigation of the Mechanical Properties of N50H Jacket for CFETR High-Temperature Superconducting Application

The China Fusion Engineering Test Reactor (CFETR) proposes the use of high-temperature superconductors as next-generation central solenoid coil magnets to excite a stronger magnetic field. Currently, REBCO and Bi-2212 are two candidate materials for high-temperature superconductors. For some time to come, the fusion reactor superconducting magnet system will keep using a Cable-In-Conduit Conductors (CICC) structure. The strength of current jacket materials can not meet the current requirements of CFETR central solenoid (CS) magnets at 4.2 K. The jacket of CICC has been prepared by N50H material in China, and some research and development work has been carried out. However, in the Bi-2212 magnet manufacturing process, the N50H jacket should undergo a series of procedures, especially the 890 degrees C heat treatment process may cause its mechanical properties to decline. This article introduces the mechanical properties of N50H jackets before and after aging heat treatment at different temperatures and discusses its influence on mechanical properties at low temperatures. The results show that the elongation is only about 15% at 4.2 K, which temporarily does not meet the requirements, N50H can not be used as jacket of Bi2212 wires at present.