Characterization of In-Field Critical Currents in REBCO Tapes Over Wide Temperature Range by Pulsed Current Source With Supercapacitor

The field and temperature dependence of the critical current <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> is a vital factor in designing the superconducting magnets. The standard method of measuring <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> involves applying a dc current and measuring voltage. However, when assessing the field dependence of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , the high magnetic field's space constraints and cooling power limit the injection of dc current into the sample. To address this, we have developed a method using pulsed current to significantly reduce heat generation. Our previous research reported an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> measurement system capable of handling up to 19 T and variable temperatures with a pulse current up to 500 A. In this study, we have enhanced the system with electric double layer capacitors, known as supercapacitors, allowing currents up to 2 kA. This upgrade enables the measurement of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> in the high-temperature superconducting REBCO tapes, which are 4 mm wide, at cryogenic temperatures as low as 4.2 K in magnetic fields or 20 K even under a self-field. We have verified the system's reliability by comparing measurements of dc and pulsed currents. Additionally, we contrasted the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> values of full width samples with those of samples containing micro-bridges.