Screening currents are field-induced dynamic phenomena which occur in superconducting materials, leading to persistent magnetization. Such currents are of importance in ReBCO tapes, where the large size of the superconducting filaments gives rise to strong magnetization phenomena. In consequence, superconducting accelerator magnets based on ReBCO tapes might experience a relevant degradation of the magnetic field quality in the magnet aperture, eventually leading to particle beam instabilities. Thus, persistent magnetization phenomena need to be accurately evaluated. In this paper, the 2D finite element model of the Feather-M2.1-2 magnet is presented. The model is used to analyze the influence of the screening current-induced magnetic field on the field quality in the magnet aperture. The model relies on a coupled field formulation for eddy current problems in time-domain. The formulation is introduced and verified against theoretical references. Then, the numerical model of the Feather-M2.1-2 magnet is detailed, highlighting the key assumptions and simplifications. The numerical results are discussed and validated with available magnetic measurements. A satisfactory agreement is found, showing the capability of the numerical tool in providing accurate analysis of the dynamic behavior of the Feather-M2.1-2 magnet.

中文翻译：

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HTS插入偶极磁铁Feather-M2.1-2中屏蔽电流感应磁场的数值分析

屏蔽电流是发生在超导材料中的场致动态现象，导致持续磁化。这种电流在 ReBCO 带中很重要，其中超导丝的大尺寸会产生强磁化现象。因此，基于 ReBCO 带的超导加速器磁体可能会经历磁体孔径中磁场质量的相关退化，最终导致粒子束不稳定。因此，需要准确评估持续磁化现象。在本文中，介绍了 Feather-M2.1-2 磁铁的二维有限元模型。该模型用于分析屏蔽电流感应磁场对磁体孔径内磁场质量的影响。该模型依赖于时域涡流问题的耦合场公式。介绍了配方并对照理论参考进行了验证。然后，详细介绍了 Feather-M2.1-2 磁铁的数值模型，突出了关键假设和简化。数值结果通过可用的磁测量进行讨论和验证。找到了令人满意的一致性，表明该数值工具能够准确分析 Feather-M2.1-2 磁体的动态行为。