Multi-pulse current technique used for I c and thermal stability assessment of HTS superconductors

Abstract Multi-pulse current (MPC) technique has been developed for advanced characterization of critical currents and electro-thermal stability of composite superconductors especially under conditions, where the critical current magnitude is large and electrothermal stability is relatively low. Short current pulses of 30 ms duration enable the measurement of high critical currents in composite superconductors without undesirable heating. The resulting E–I characteristics were compared with those obtained using the conventional DC method under various cooling conditions. Transport characterization of a 4 mm-wide REBCO tape with a filamentary structure was performed over a wide temperature range down to 20 K under applied magnetic fields up to 10 T and transport currents up to 350 A. Longer current pulses (of up to 1 s) enable the analysis of the electro-thermal stability of the same sample in liquid nitrogen (LN 2 ) at 77 K and in subcooled water (H 2 O) ice at temperatures below 77 K. Investigations of the electrothermal stability confirmed enhanced heat extraction capabilities of H 2 O ice compare to conventional LN 2 bath cooling. The tape exhibits advanced stability performances at lower temperature despite was exposed to magnetic field up to 1 T, at temperature of 62.5 K the energy required to initiate a quench was approximately 8 times higher compared to experiment performed at 75 K, assuming the same I c value.