Pulse Field Magnetization of GdBCO without Rapid Decrease in Magnetic Flux Density

Pulse field magnetization (PFM) method for high-temperature superconducting (HTS) bulks is attractive for promoting the use of HTS technology in various applications. Waveform control pulse field magnetization (WCPM) method is new techniques which has shown promising results so far in trapping strong magnetic fields by a single pulsed magnetic field. The cause of most of the magnetic field penetrating in the bulk by the application of a pulsed magnetic field not to be trapped is thought to be the local heat generated by the steep flux motion caused by the increase and decrease of that pulsed magnetic field. In this presentation, we show the results of magnetization under controlled conditions so that the magnetic flux that once entered the HTS bulk does not abruptly decrease. The penetration flux density measured on the surface of the GdBCO bulk was used as input to control the negative feedback as in previous studies. The bulk was placed between two vortex-type coils that replicated the internal structure of our previously developed axial-gap superconducting rotating2. At 40 K, by generating a pulsed magnetic field by negative-feedback-WCPM (NFB-WCPM) with a slight decrease in flux density, we applied almost constant magnitude magnetic flux density to the bulk sample for more than 1 s, and obtained a flux density nearly three times higher than the maximum flux density obtained with conventional PFM. NFB-WCPM worked effectively to obtain high trapped flux density even at 40 K. The bulk sample successfully trapped a flux density of nearly 4 T for less than two seconds by a single NFB-WCPM by adjusting the control conditions.