AC losses in HTS bulk and their influence on trapped magnetic field

Zushi, Yasuyuki; Asaba, I.; Ogawa, J.; Yamagishi, K.; Tsukamoto, O.

doi:10.1016/j.cryogenics.2004.06.007

Cited by 23 publications

(17 citation statements)

References 6 publications

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“…This differs from previous studies in which the sample is magnetized permanently prior to the application of the AC field [22][23][24]. The alternating magnetic field is applied (9)].…”

Section: Methodscontrasting

confidence: 42%

“…The temperature rise of a bulk superconductor subjected to an applied AC magnetic field, as usually observed in experiments [24,25] is shown schematically in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

“…Previous works have shown the importance of thermal boundary conditions [35]. For simplicity, we assume that the heat transfer rate Q out between the superconductor and the cryogenic environment (at temperature T 0 ) is given by [22,24] ( )…”

Section: Magneto-thermal Effects For An Infinitely Long Superconductormentioning

confidence: 99%

“…Thermal runaway occurs on increasing the field amplitude further that results in a sharp temperature increase up to an equilibrium value close to T c . The experimentally observed temperature rise of a bulk sample subjected to AC fields of varying amplitude can be described successfully by a simple analysis based on the Bean model [31] applied to a type-II superconducting cylinder assuming a linear temperature dependence of the critical current density J c (T) [22,32] and a constant convective heat transfer coefficient between the sample and the coolant [24]. In such studies performed, however, the theoretical T(t) curves are obtained for a given set of material parameters and heat transfer characteristics that are representative of the superconducting sample under study.…”

Section: Introductionmentioning

confidence: 99%

“…In this case, the material is likely to experience transient or periodic variations of the applied magnetic field that are due, for example, to vibrations, lateral movement or irregular magnetization of a permanent magnet that may interact with the superconductor [13,14]. Although the most severe damages arise when the time-varying field perturbations are perpendicular to the initial magnetization [15][16][17], the vortex motion in parallel configuration may also cause large hysteresis losses and possibly considerable self-heating which, in turn, may have a detrimental effect on the initial trapped flux of the bulk superconductor [18][19][20][21][22][23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

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Magneto-thermal phenomena in bulk high temperature superconductors subjected to applied AC magnetic fields

Vanderbemden¹,

Laurent²,

Fagnard³

et al. 2010

Supercond. Sci. Technol.

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Abstract.In the present work we study, both theoretically and experimentally, the temperature increase in a bulk high-temperature superconductor subjected to applied AC magnetic fields of large amplitude. We calculate analytically the equilibrium temperatures of the bulk sample as a function of the experimental parameters using a simple critical-state model for an infinitely long type-II superconducting slab or cylinder. The results show the existence of a limit heat transfer coefficient (AU lim ) separating two thermal regimes with different characteristics. The theoretical analysis predicts a "forbidden" temperature window within which the temperature of the superconductor can never stabilize when the heat transfer coefficient is small. In addition, we determine an analytical expression of two threshold fields H tr1 and H tr2 characterizing the importance of magneto-thermal effects and show that a thermal runaway always occurs when the field amplitude is larger than H tr2 . The theoretical predictions of the temperature evolution of the bulk sample during a self-heating process agree well with the experimental data. The simple analytical study presented in this paper enables order of magnitude thermal effects to be estimated for simple superconductor geometries under applied AC magnetic fields and can be used to predict the influence of experimental parameters on the self-heating characteristics of bulk type-II superconductors.

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“…This differs from previous studies in which the sample is magnetized permanently prior to the application of the AC field [22][23][24]. The alternating magnetic field is applied (9)].…”

Section: Methodscontrasting

confidence: 42%

“…The temperature rise of a bulk superconductor subjected to an applied AC magnetic field, as usually observed in experiments [24,25] is shown schematically in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%