Influence of Preexcitation, High Temperature Magnetization and Combined Excitation Method on Screening Current Attenuation in Conduction-Cooled REBCO Coil

This article investigated a suitable excitation method for a conduction-cooled REBCO coil to reduce the temporal attenuation of the screening current induced field (screening field) for magnetic resonance imaging. We investigated the effect of the preexcitation of the coil and high temperature magnetization method on the screening field attenuation by measuring the variation rate of the magnetic field at the side surface of a conduction-cooled rare-earth barium copper oxide double pancake coil. Experimental results showed that the preexcitation of the coil and high temperature magnetization increased the temporal stability of the coil magnetic field when the preexcitation current is higher than the main operational current, or the temperature change of the high temperature magnetization is over 5 K, respectively. We also clarified that the combination of the preexcitation, overshooting, and high temperature magnetization method greatly suppressed the attenuation of the screening field and also the load factor of the coil than in the case when only the high temperature magnetization is applied.