Reconstruction of critical current density profiles from AC loss measurements

Magnetic Flux Dynamics in HTS Bulks with Levitation Techniques

“…Measuring the parameters of forced oscillations of a PM one can obtain information about structure and electromagnetic properties of explored HTS samples. Figure 3 represents a basic system [24][25][26], which has been used with granular [27][28][29][30][31][32] and composite [30,32] YBCO and BSCCO ceramics, and, in a slight modification, with the meltprocessed YBCO quasi-single crystals [11,[32][33][34][35][36]. Here, the forced oscillations of the permanent magnet with mass m, magnetic moment , and diameter d, which levitates on the distance of x 0 over the surface of the HTS sample, have been induced by the AC coil, and their amplitude has been measured by the microscope with 5 m accuracy.…”

“…13, are observed for the samples just after manufacturing. With ageing of samples that firstly affects undersurface layers, these dependences become non-linear [36]. This means that the critical current density J c becomes spatially nonuniform.…”

“…0.7910 4 A/cm 2 . In [36] we have found the correlations between J c (x) and Q 1 (A) functions and developed a technique to recover the critical current density profiles J c (x) in thin undersurface layer. The similar approach for reconstruction of critical current density profiles from AC susceptibility measurements have been proposed by Campbell [74].…”

“…In the AC magnetic field the energy dissipated per period per unit of surface area in non-uniform superconductor (J c (B)  const, J c (x)  const) is [36] …”

Vortex Dynamics in Bulk HTS with Levitation Techniques

“…The basic system was used to investigate the granular [8][9][10][11][12][13][14] and composite [12] YBCO and BSCCO ceramics. To investigate the melt-textured YBCO samples the slight modification of it was used [15][16][17][18]. Scheme of such a basic system is represented in Fig.1.…”