In this chapter we study the magnetization of Type II superconductors by using a phenomenological theory of magnetization developed in 1962 by Bean [5.1]. As remarked in CHAPTER 1, over the field range of interest (above 0.5 T) for most magnet applications, a Type II uperconductor is in the mixed state, consisting of normal state islands in a sea of superconductivity. When a Type II superconductor is subjected to a time varying magnetic field or transport current, dissipation takes place in these islands and manifests either as "flux jumping," a transitory phenomenon, or AC losses. Known as Bean's critical state model, the theory, pertinent to LTS and HTS, has been successfully applied to formulate requirements in closed-form expressions to eradicate flux jumping and minimize AC losses.
Today, well-established methods of producing LTS wires and cables that virtually eradicate flux jumps are available. As we will study in this chapter, flux jumping is not an overriding concern with HTS as it is for LTS. Thus, if magnetization were important only for eradication of flux jumping, for HTS applications, it might be appropriate to regard it as a minor topic. However, because it also plays a crucial role in AC losses in both LTS and HTS, we are devoting an entire chapter here to study magnetization; AC losses will be addressed in more detail in CHAPTER 7.
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References
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Iwasa, Y. (2009). MAGNETIZATION. In: Case Studies in Superconducting Magnets. Springer, Boston, MA. https://doi.org/10.1007/b112047_5
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DOI: https://doi.org/10.1007/b112047_5
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