Flux trapping characteristics of YBCO bulks using pulse magnetization [superconducting magnets]

The authors have studied the magnetization characteristics of an array of high Tc superconductor (HTS) bulks. Experiments using pulsed field magnetization were carried out at 77 K. In the experiment, the width of the applied pulse current was varied; i.e.: (1) the wave-front length of the pulse magnetization current; and (2) the wave-tail length of the pulse magnetization current were changed independently. The authors measured the magnetization pattern of single HTS bulks and that of arrayed HTS bulks. Furthermore, several HTS bulks were arranged in array and inserted into a pulse magnetization coil wound by copper wire. The measured trapped magnetic flux distribution in this experimental setup was compared with experimental results from "field cooling". The experimental result shows that the trapped magnetic flux density is lower in the pulse magnetization than in the "field cooling". Also, the flux density pattern of pulse magnetization shows a conspicuous sag in the center of the bulk. As for the effect of the width of the applied pulse wave, the wave-front length affects strongly the trapped magnetic flux density. Meanwhile, the effect of the wave-tail length was very mild.