Stability of a (2G) Coated, Thin-Film YBaCuO 123 Superconductor: Intermediate Summary
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REVIEW
Stability of a (2G) Coated, Thin-Film YBaCuO 123 Superconductor: Intermediate Summary Harald Reiss 1 Received: 28 April 2020 / Accepted: 30 June 2020 / Published online: 17 September 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract This paper summarises results obtained with stability calculations of thin films and multi-filamentary superconductors. In a series of papers, all the contributions have been published in this journal. We now extend our previous investigations to the temporal aspect of the internal heat transfer and to the material homogeneity problem. Within multi-component heat transfer (solid conduction, radiation), the standard theory of radiative transfer in a coated, thin-film, YBaCuO3 123 superconductor correctly treats the energetic aspects of radiation propagation; this is the actual core of stability models. But a rigorous solution of the temporal aspect still is missing. It is the study of this aspect that would provide a new access to the physics of superconductor stability, in particular if after a disturbance the system is already close to a phase transition. A matrix formulation, using a combination of Monte Carlo and radiative transfer calculations, is suggested to circumvent the temporal solid conduction/ radiative transfer problem in multi-component heat flow. As an important result, quench is not an event that proceeds instantaneously. Instead, it is a process the speed of which decreases the more, the closer the superconductor temperature approaches critical temperature until the residual number of electron pairs becomes too small to support critical current. The stability of superconductors and thermal fluctuations might reflect a common background: the relaxation time of the density of electron pairs after disturbances. Keywords Short time physics . Radiative transfer . YBaCuO . BSCCO . Non-transparency . Stability . Homogeneity . Thermal fluctuations . Physical time . Entanglement . Entropy
1 Survey: Superconductor Stability Models Standard, analytic stability models of how to avoid quench of superconductors are thoroughly described by Wilson [1], Dresner [2] and Seeger [3] and in a large number of other contributions; see citations to original literature in these three references. When applied to superconductor magnet design and operation, the success of these stability models is impressive and uncontested. But the traditional models, without modifications, assume worst-case scenarios and stationary conditions, while quench of superconductors proceeds on very small timescales. Since critical current density, JCrit(x, y, t), in the superconductor (x, y-) cross section strongly depends on temperature, thorough
analysis of temperature fields, T(x, y, t) and their short-time, transient development after disturbances becomes mandatory. This is important if superconductor temperature, or the other critical superconductor parameters, during or after a disturbance, approach their critical values. This situation, the superconductor already close t
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