The trapped field B T and temperature rise T on a large GdBaCuO superconducting bulk (65 mm in diameter) have been investigated during pulse field magnetization (PFM), and compared with those on GdBaCuO bulk with a diameter of 45 mm. The maximum trapped field at the bulk center B T (C) on the φ 65 mm bulk is as small as 1.9 T at T s = 40 K for the single pulse field application of B ex = 6.7 T, which is smaller than that of the φ 45 mm bulk (B T (C) = 3.2 T). The total trapped flux T on the φ 65 mm bulk is, however, about twice as large as that on the φ 45 mm bulk. The magnetic fluxes cannot sufficiently intrude into the center of the φ 65 mm bulk at T s = 40 K for pulse field applications up to 6.7 T, whereas a large number of the magnetic fluxes are trapped at the peripheral region of the bulk. The trapped field characteristics for both bulks with different diameters can be roughly interpreted by a simple critical state model under zero field cooling (ZFC).
We have investigated the total trapped flux Φ T (z) on the φ65 mm GdBaCuO superconducting bulk as a function of distance z from the bulk surface magnetized by a successive pulse field application (SPA) with identical magnitude and subsequent iterative pulsed-field magnetization method with reducing the amplitude (IMRA) at various temperatures T s . The Φ T (z) value was enhanced by the IMRA process and reached 5.02 mWb on the bulk surface at T s =40 K, which was about 1.7 times larger than that at the end of SPA. The Φ T (4 mm) value at 40 K by the SPA+IMRA method was as high as Φ T FC (4 mm) by field cooled magnetization under B ex =3 T at 48 K. The IMRA method is quite effective to enhance the Φ T value for large superconducting bulks.(125 words)
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The time dependence of the temperatures T(z, t) has been measured along the thickness direction z in several drilled holes in a superconducting bulk during pulsed field magnetization (PFM) and the heat generation and heat transfer in the bulk have been discussed. In the previous paper (Supercond. Sci. Technol. 19 (2006) S540), we calculated the T(z, t) profiles in the bulk by solving a three-dimensional heat-diffusion equation to reproduce the measured T(t) on the bulk surface; the heat generation took place adiabatically and the calculated T(z, t) was isothermal along the z direction. In this study, the measured T(z, t) at the top surface was higher than that at the bottom surface just after the pulse field application at t<0.5 s, and then became isothermal with increasing time. These results suggest that the magnetic flux intrudes inhomogeneously into the bulk from the edge of the top surface and the periphery at the early stage. The
ACCEPTED MANUSCRIPTinhomogeneous magnetic flux intrusion and the flux trap during PFM change depending on the strength of the pulsed field and the pulse number in the successive pulse field application. (184 words)
Trapped field profiles of the GdBaCuO superconducting bulk of 65 mm in diameter have been measured as magnetized using a successive pulsed-field application (SPA) and a subsequent iterative pulsed-field magnetization with reducing amplitude (IMRA). The trapped field gradient dB T /dx on the bulk periphery increases concomitantly with increasing pulse number in the IMRA part. The dB T /dx value on the bulk magnetized by field-cooled magnetization (FCM) was also measured at each temperature T F. The maximum temperature T max for each pulse was estimated by comparing the dB T /dx value for the IMRA part with that for the FCM at each temperature. Furthermore, T max was measured directly for the SPA part in the drilled hole in the bulk. The estimated T max was nearly equal to the measured T max , which thereby confirmed that T max after applying the pulsed field can be estimated using the dB T /dx value in the bulk periphery. The enhancement of the total trapped flux P T in the IMRA part with increasing pulse number results from enhancement of the critical current density J c because of the reduction in T max .
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