Portable, high magnetic field charging of bulk superconductors for practical engineering applications

用于实际工程应用的块状超导体的便携式高磁场充电

• 批准号: EP/P020313/1
• 负责人: Mark Ainslie
• 金额: $ 114.97万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FP020313%2F1
• 关键词: Portable; magnetic; field; charging; bulk

Bulk superconductors can be used, when cooled to cryogenic temperatures, as super-strength, stable permanent magnets generating fields of several Tesla, compared to the 1.5-2 Tesla limit for conventional permanent magnets, such as neodymium magnets (Nd-Fe-B). This makes them attractive for a number of engineering applications that rely on high magnetic fields, including compact and energy-efficient motors/generators with unprecedented power densities and compact and portable magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) systems. It is now also possible for scientists to use high magnetic fields to exploit the magnetism of a material for controlling chemical and physical processes, which is attractive for magnetic separation and magnetic drug delivery systems (MDDS), for example. The chief advantage of a bulk superconductor magnet is that the available field can be up to an order of magnitude higher than conventional permanent magnets (bulk high-temperature superconductors have been shown to be capable of trapping magnetic fields greater than 17 Tesla) and no power supply and direct connection is necessary to supply the current producing the magnetic field, as in electromagnets.The magnetisation process of a bulk superconductor essentially involves the application and removal of a large magnetic field that induces a circulating supercurrent in the material that flows without resistance. However, one significantly challenging problem currently faced is achieving a simple, reliable and portable charging technique to magnetise such superconductors, and this is crucial to producing competitive and compact designs for high-field, trapped flux-type superconducting applications. The current, best-known method for magnetising bulk superconductors practically is the pulsed field magnetisation (PFM) technique, whereby a large magnetic field is applied via a pulse on the order of milliseconds. However, the world record using PFM is only 5.2 Tesla at 29 K, which is much less than the true capability of these materials. The PFM technique has many design considerations: the magnitude and duration of the pulse(s), the number of applied pulses, the type and shape of the magnetising coil/fixture, how the bulk superconductor is cooled, and the temperature(s) at which the pulse(s) are applied. All of these considerations will be analysed through numerical modelling in order to thoroughly optimise the PFM setup in view of a portable, high-field magnet system. Numerical modelling, validated by experimental results, is a particularly important and cost-effective method to interpret experimental results and the physical mechanisms of the material during the magnetisation process. Such modelling tools can also be used to predict and propose new magnetising techniques, which is more difficult to achieve experimentally. The primary objective of this research programme is to develop portable, high magnetic field charging of bulk superconductors for practical engineering applications, with an end goal of producing portable and commercially-viable high-field magnet systems. This will be underpinned by the tailoring the material processing and properties of bulk superconductors and magnet geometry for high field applications, developing numerical models for complete electromagnetic-thermal-mechanical analysis to avoid potential mechanical fracture when high magnetic fields are involved (> 6-7 Tesla) and carrying out experiments to validate such models, and the development of an optimised PFM technique that takes into account all of the design considerations above. Two types of pulsed charging systems will be developed around solenoid- and split-type magnetising coils, which will be used to achieve trapped fields in excess of 5 Tesla, the current record, at temperatures greater than 40 K and as a proof-of-concept for bespoke designs for specific applications.

当冷却至低温时，块状超导体可用作超强度、稳定的永磁体，产生数特斯拉的磁场，而传统永磁体（如钕磁体 (Nd-Fe-B)）的磁场限制为 1.5-2 特斯拉。这使得它们对许多依赖高磁场的工程应用具有吸引力，包括具有前所未有的功率密度的紧凑型节能电机/发电机以及紧凑型便携式磁共振成像 (MRI) 和核磁共振 (NMR) 系统。现在，科学家还可以使用强磁场来利用材料的磁性来控制化学和物理过程，这对于磁分离和磁性药物输送系统 (MDDS) 等来说很有吸引力。块状超导磁体的主要优点是，可用磁场比传统永磁体高出一个数量级（块状高温超导体已被证明能够捕获大于 17 特斯拉的磁场），并且不需要电源和直接连接来提供产生磁场的电流，如电磁体。块状超导体的磁化过程本质上涉及应用和 去除大磁场，该磁场会在材料中感应出无阻力流动的循环超电流。然而，目前面临的一个重大挑战是实现一种简单、可靠和便携式的充电技术来磁化此类超导体，这对于为高场、俘获通量型超导应用生产有竞争力的紧凑设计至关重要。目前最著名的磁化体超导体的方法实际上是脉冲场磁化（PFM）技术，通过毫秒量级的脉冲施加大磁场。然而，使用 PFM 的世界纪录在 29 K 时仅为 5.2 特斯拉，远低于这些材料的真实能力。 PFM 技术有许多设计考虑因素：脉冲的幅度和持续时间、施加的脉冲数量、磁化线圈/夹具的类型和形状、体超导体的冷却方式以及施加脉冲的温度。所有这些考虑因素都将通过数值建模进行分析，以便针对便携式高场磁体系统彻底优化 PFM 设置。通过实验结果验证的数值模型是解释实验结果和材料在磁化过程中的物理机制的一种特别重要且具有成本效益的方法。这种建模工具还可用于预测和提出新的磁化技术，而这在实验上更难以实现。该研究计划的主要目标是开发用于实际工程应用的便携式高磁场充电体超导体，最终目标是生产便携式且商业上可行的高磁场磁体系统。这将通过以下方式支撑：针对高场应用定制块状超导体和磁体几何形状的材料加工和性能，开发用于完整电磁热机械分析的数值模型，以避免在涉及高磁场（> 6-7特斯拉）时潜在的机械断裂，并进行实验来验证此类模型，以及开发考虑所有设计考虑因素的优化PFM技术 多于。将围绕螺线管型和分体式磁化线圈开发两种类型的脉冲充电系统，这些系统将用于在高于 40 K 的温度下实现超过 5 特斯拉（当前记录）的俘获磁场，并作为针对特定应用的定制设计的概念验证。

项目成果

A new benchmark problem for electromagnetic modelling of superconductors: the high-T$_{c}$ superconducting dynamo

超导体电磁建模的新基准问题：高T$_{c}$超导发电机

• DOI: 10.5445/ir/1000123320
• 发表时间: 2020
• 作者: Ainslie M

A new benchmark problem for electromagnetic modelling of superconductors: the high- T c superconducting dynamo

超导体电磁建模的新基准问题：高温超导发电机

• DOI: 10.17863/cam.56979
• 发表时间: 2020
• 作者: Ainslie M

A new benchmark problem for electromagnetic modelling of superconductors: The high-T csuperconducting dynamo

超导体电磁建模的新基准问题：高温超导发电机

• DOI: 10.17863/cam.81461
• 发表时间: 2020
• 作者: Ainslie M

Corrigendum: A new benchmark problem for electromagnetic modelling of superconductors: the high-T c superconducting dynamo (2020 Supercond. Sci. Technol. 33 105009)

勘误表：超导体电磁建模的新基准问题：高温超导发电机（2020 Supercond. Sci. Technol. 33 105009）

• DOI: 10.1088/1361-6668/abd522
• 发表时间: 2021
• 期刊: Superconductor Science and Technology
• 影响因子: 3.6
• 作者: Ainslie M

An Explanation for Observed Flux Creep in Opposite Direction to Lorentz Force in Partially-Magnetized Bulk Superconductors

对在部分磁化体超导体中观察到的与洛伦兹力相反方向的磁通蠕变的解释

• DOI: 10.17863/cam.37221
• 发表时间: 2019
• 作者: Ainslie M