Magnetization properties for Gd–Ba–Cu–O bulk superconductors with a couple of pulsed-field vortex-type coils

Pulsed-field magnetization was studied for field-free cooled high-temperature superconductor (HTS) bulk cylindrical disks of melt-textured Gd–Ba–Cu–O samples at the liquid nitrogen temperature. A bulk sample was inserted in between disks of vortex-type pulsed-field copper coil immersed in the liquid nitrogen. The flux was trapped in the centre of the sample surface under the smaller pulsed peak field than the magnetization with a conventional solenoid coil. With intensifying the pulsed-field, the trapped flux density for the maximum peak remanent value in the field cooling process increases monotonously to the liquid nitrogen temperature. In the samples with strong pinning force, which shows large remanent flux on field cooling, the deviation from the conical profile of trapped field distribution was observed. This is attributed to the transient flux motion, which possibly drives temperature increase resulting in the decrease of the trapped field in the growth sector. However, the subsequent single pulsed-field remarkably compensates the formation of a well-dressed conical field density profile. Employing a couple of vortex-type coils enables us to magnetize the HTS bulk cryo-magnets effectively with reduced electric energy per pulsed-current for the magnetization with a pulsed-field solenoid. The present magnetization geometry is acceptable for application of the HTS bulk to the rotor magnet magnetized with an armature in the synchronous rotating machines.