Simulation of temperature and magnetic field distribution in superconducting bulk during pulsed field magnetization

A theoretical simulation of electromagnetic and thermal fields was performed for a cryocooled superconducting bulk disc after applying a magnetic pulse. The results of the simulation qualitatively reproduced the experimental ones for the time and applied field dependences of the trapped field B(z) and the temperature T on the bulk surface. For magnetic pulse application with a rise time of tau = 0.01 s, the magnetic flux propagation was about two orders of magnitude faster than the heat propagation because of the low thermal conductivity of the bulk. The results show that the intruding magnetic flux escaped because of the delayed temperature rise. For a longer magnetic pulse application with tau = 1 or 10 s, the flux propagation speed becomes slow and approaches the heat propagation speed. In this case, the magnetic flux escape attributable to the flux creep becomes small and a higher trapped field can be achieved. The method of exploring the enhancement of the trapped field using pulsed field magnetization is discussed.