Quench properties of Au/YBCO meander lines under AC fault current

Abstract

We investigated quench properties of Au/YBa 2Cu 3O 7 (YBCO) meander lines on sapphire substrates under AC fault current. It was done by analyzing behavior of the oscillatory component of meander-line resistance during quenches. The 300 nm thick YBCO film was coated with a gold layer of 200 nm thickness, and patterned into a meander line. The meander line was subjected to simulated AC fault current for resistance measurements. It was immersed in liquid nitrogen during the experiment for effective cooling. The oscillatory component was much smaller than the background component, and was nearly constant. It lagged behind the dissipated power by 43° in phase angle throughout quenches. This behavior was universal for all Au/YBCO meander lines on sapphire substrates. It was observed at different field strength and on meander lines of different sizes. The behavior was explained quantitatively with the concept of heat transfer within the meander line/substrate and to surroundings. Difference in phase and amplitude between resistance and power of meander lines was related only with the thermal properties and the dimension of the meander line/substrate. Thus, thermal properties of meander lines/substrate could be investigated effectively by studying behavior of the oscillatory component of meander-line resistance.