Modelling of high temperature superconductor magnetic systems to enable low carbon advancements in science and technology

该项目将通过创建新的耦合电磁和热模型来探索高温超导体（HTS）线圈中的淬火起始和传播。为了在4.2开尔文的工作温度下实现超过大约20特斯拉的磁场，必须利用高温超导。通常，它们被用作低温超导（LTS）“外壳”内的插入件。已经探索了在LTS线圈中精确模拟淬火行为的能力，但是由于HTS材料的行为差异，这些技术不能直接适用于HTS插入线圈。该领域的精确建模能力将有助于设计紧凑、高场磁体、量子材料分析、高分辨率核磁共振和聚变等能源应用。模型必须耦合材料的电磁和热行为及其与环境的相互作用，包括与LTS磁铁的相互作用。超导线圈内的传热由偏微分方程控制，其中第一项表示热扩散，其他项表示热产生机制，包括电阻加热和交流损耗，以响应电流密度和磁场的变化。高温超导插入线圈中的电流由线圈的电感-电阻（LR）电路和线圈之间的互感保护电路控制，而高温超导线圈中的电阻是由电磁和热效应产生的。磁场由线圈电流的二维比奥-萨瓦积分决定。在高温超导中，在淬火起始瞬间之前，问题是轴对称的。在淬火瞬间，轴对称被打破，淬火传播的模拟必须切换到三维空间。在确定淬火起始位置时，需要考虑材料性能随机变化的作用。在这个项目中，将创建新的模型来探索这种行为。将建立一个二维轴对称模型来预测高温超导线圈在淬火前的行为。超导体在临界状态下的最小猝灭能量的概念将被用来确定猝灭开始传播的时间。然后通过应用傅立叶级数在三维空间中求解淬火在周向上的传播，并行处理应用于独立求解每个傅立叶系数。该项目将重点研究在~10T的LTS背景场中工作的HTS测试线圈的情况。这将使实验得以进行，以检验模型的预测。这些实验是这个项目的补充，而不是它的一部分。

This project will explore Quench initiation and propagation in a high temperature superconductor (HTS) coil by creating new coupled electromagnetic and thermal models. In order to achieve magnetic fields in excess of approximately 20 Tesla at an operating temperature of 4.2 Kelvin, HTS must be utilised. Typically, these are used as inserts within low temperature superconducting (LTS) 'outserts'. The ability to model quench behaviour accurately in LTS coils has been explored, however due to the differences in behaviour of HTS materials these techniques are not directly applicable to HTS insert coils. Accurate modelling capability in this area will aid the design of compact, high field magnets quantum materials analysis, high-resolution NMR and energy applications such as fusion. Models must couple Electromagnetic and thermal behaviour of the material, and its interaction with its environment, including with LTS magnets. Heat transfer within a superconducting coil is governed by a partial differential equation with a first term representing heat diffusion and other terms representing mechanisms of heat generation including resistive heating and AC losses in response to changes in current density and magnetic field. Current in the HTS insert coil is governed by an inductor-resistor (LR) circuit of coils and protection circuit with mutual inductance with between the coils and resistance in the HTS coils arising from EM and thermal effects. The magnetic field is determined by two-dimensional Biot-Savart integration of the coil currents. Before the instant of quench initiation in the HTS the problem is axisymmetric. At the instant of quench, the axial symmetry is broken and the simulation of quench propagation must then be switched to three dimensions. The role of random variations in the material properties in determining the location of the quench initiation will need to be considered. In this project new models will be created to explore this behaviour. A two-dimensional axisymmetric model will be created to predict the behaviour of the HTS coil in the lead up to the quench. The concept of Minimum Quench Energy for a superconductor at critical state will be exploited to determine the time at which the quench begins to propagate. The propagation of the quench in the circumferential direction will then be solved in three dimensions by application of a Fourier series, with parallel processing applied to solve for each Fourier coefficient independently.The project will focus on the case of a HTS test coil operating in a LTS background field of ~10T. This will enable experiments to be carried out to test the predictions of the model. These experiments are in addition to this project, not part of it.