Speaker
Description
High-temperature superconducting (HTS) tapes are promising materials for developing high-field magnets for fields exceeding 30 T. Therefore, it is important to characterize their properties at high fields, in particular, the critical current, $I_{\rm c}$. One of the promising types of HTS tape is produced by THEVA where the architecture of the tape is unique and simple. Nowadays, these tapes show self-field $I_{\rm c}$ at 77 K of about 600 A/cm-width, among the highest reported. Moreover, since the microstructure of GdBCO in these tapes has a tilted orientation, maximum $I_{\rm c}$ can be achieved around 60$^\circ$ from the normal direction. However, the transport properties at low temperatures are not easily available due to the large current requirements. In this work, the field and angle dependence of the transport $I_{\rm c}$ at 4.2 K and magnetic fields up to 29 T is measured for the first time.
A 4 mm-wide THEVA Pro-Line HTS tape and pinning-improved tapes are characterized. The standard tape has a self-field $I_{\rm c}$ of 240 A at 77 K, and a similar value is obtained at 4.2 K and 15 T for $B\parallel c$. For $B\perp$tape, $I_{\rm c}$ is 180 A at 29 T and about 460 A at 5 T. These are already competitive results when compared to the present high values at 4.2 K of 4-mm wide tapes. The parameter $\alpha$ based on the field dependence of $I_{\rm c}$ given by $I_{\rm c}(B)\propto B^{-\alpha}$, is around 0.5 within the angular range of -45$^\circ$ to 50$^\circ$ and decreases to 0.3 for $B\parallel ab$. The pinning force per unit length, $F_{\rm p}$ continuously increases up to 29 T, and no maximum was observed for all angles. With the good in-field properties obtained in the standard THEVA tape, further investigations on tapes with additional pinning centers are conducted to explore how $I_{\rm c}$ would further improve at very high fields.
We acknowledge the support of LNCMI-CNRS, member of the European Magnetic Field Laboratory (EMFL).
