Recent development and mass production of high Je 2G-HTS tapes by using thin hastelloy substrate at Shanghai Superconductor Technology

Over the past few years, emerging applications such as high current conductors for magnets in compact fusion systems and ultra-high field insert magnets require higher engineering current density (J(e)) of the second generation high temperature superconductor (2G-HTS) tapes. In this paper, the state-of-art of 2G-HTS tapes with 30 mu m Hastelloy substrate at Shanghai Superconductor Technology (SST) are presented. RE1Ba2Cu3O7 (REBCO, RE = rare earth) films with strong artificial pinning centers (APCs) are deposited on 30 mu m thick Hastelloy substrate. Compared to those with 50 mu m thick substrate, higher average critical current (I-c), better I-c homogeneity and better I-c linearity with film thickness increase are also achieved at 77 K self-field for tapes with 30 mu m substrate, where piece lengths are up to 1 km. For a 4 mm wide tape with a total thickness of 35 mu m, I-c and non-copper J(e) values reach 600 A and 450 kA cm(-2) at 4.2 K, 10 T (B//c), respectively. Transmission electron microscopy observation reveals formation of mixed landscape defects mainly including high density of splayed nanoroads and stacking faults in the REBCO film thickness direction, which is attributed to the extremely high REBCO growth rate of over 50 nm s(-1). The pinning force density (F-p) at 4.2 K, 12 T (B//c) reaches over 800 GN m(-3), and the lift factors (defined as the ratio of I-c at 4.2 K, 10 T to I-c at 77 K, self-field) of tapes with large I-c range (100 to 500 A cm(-1)-w at 77 K, self-field) also show good consistency. The annual production of 10 mm wide tapes with such pinning centers can exceed 200 km for a single set of facility at SST. No significant I-c reduction is observed at bending diameter of 3 mm and the proof strength (R-p0.2_0) is 812 MPa, both measured at liquid nitrogen temperature.