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Description
We study to increase a trapped magnetic field of HTS bulk magnet activated by pulsed field magnetization (PFM). Although various methods to enhance the trapped field are considered, they can be broadly divided into two approaches; one is improvement of magnetizing method and another is modification of exciting equipment. In the latter, a pulse width was expanded by changing an inductance of the coil and a capacitance of condenser which was current source. However, it costs a lot for the modification. In an exciting system of PFM, soft-iron yokes are used in order to expose the bulk to the magnetic field for a long time. It can be predicted that that trapped field is improved because magnetic flux hold in a soft-iron is increased when the size of yoke is increased qualitatively. On the other hand, an effect of the size of soft-iron yoke on trapped field performance has not been evaluated quantitatively. In this paper, a GdBCO bulk 60 mm in diameter and 20 mm thick is magnetized by applying a single pulsed field with varying an amplitude of applied field and temperature when soft-iron yokes of 40, 64 and 80 mm in diameter are used, and these trapped field characteristics are compared. This method is useful for practical use because the trapped field can be enhanced only by changing a soft-iron yoke.
