High Temperature Superconductors for Fusion Technologies

核聚变--氢等轻元素的原子核结合在一起形成更大的原子核--是在像太阳这样的恒星中产生大量能量的过程。如果它能够在地球上被利用，它就有可能提供一种几乎无限和安全的能源，而不会产生燃烧传统化石燃料所释放的对环境有害的二氧化碳排放。然而，要发生核聚变，需要极高的温度和压力，因为等离子体中带正电的原子核必须以足够的能量相互碰撞，以克服极强的静电斥力。要在地球上的一台机器上实现核聚变，需要大约1.5亿摄氏度的极高温度，大约比太阳核心的温度高10倍。这排除了使用传统材料来限制等离子体的可能性，在最常见的聚变反应堆托卡马克中，取而代之的是强磁场。由于托卡马克的特定几何形状的功率密度与磁场的4次方成比例，因此使用高场磁铁进行等离子体约束有巨大的好处。高温超导体--可以在没有任何电阻的情况下导电的材料--是新一代紧凑型核聚变反应堆的一项使能技术，人们普遍认为，这将为聚变发电的商业化打开大门。这是因为最先进的高温超导带可以携带极高的电流，即使在巨大的磁场下，完全摧毁了最好的低温超导体的超导电性。然而，尽管具有奇妙性能的高温超导材料现在可以以被称为涂层导体的软带的形式出现，其长度可达约1公里，但这种材料极其复杂，对损坏非常敏感，这使得它们在聚变设备的磁体中的实际部署成为一个重大挑战。这项研究计划涉及使用先进材料表征和建模技术的独特组合来确定高温超导体在聚变反应堆的恶劣环境中将如何退化，在那里它们将不断受到高能中子的轰击。重点是在最现实的条件下了解这些复杂功能陶瓷的潜在损伤和恢复机制。由于在运行中，超导体在低温下处于超导状态时将受到中子的照射，因此将进行创新的现场实验，以了解常温和低温辐射损伤的区别。实验方案将得到超导化合物中原始和缺陷结构的第一性原理建模的支持，其结果将用于验证更大范围的辐射损伤模拟，并提供关于退化的关键数据，以便为下一代聚变磁体的材料选择和磁体设计决策提供依据。在这项研究中开发的先进表征方法也将用于了解更广泛的聚变相关材料中的辐射损害。

Nuclear fusion - the joining together of atomic nuclei of light elements such as hydrogen to form larger nuclei - is the process by which vast amounts of energy is produced in stars like our sun. If it can be harnessed on Earth it has the potential deliver a nearly unlimited and safe source of energy which does not produce the environmentally damaging CO2 emissions that are released by burning traditional fossil fuels. However, for nuclear fusion to occur, extremely high temperatures and pressures are required because positively charged atomic nuclei within a plasma have to collide with each other with sufficient energy to overcome the immensely strong electrostatic repulsion forces. To achieve nuclear fusion in a machine on Earth, extraordinarily high temperatures of around 150 million degrees Celsius are needed, about 10 times higher than the temperature of the sun's core. This precludes the use of traditional materials to confine the plasma, and in the most common type of fusion reactor called a tokamak, strong magnetic fields are used instead. Since the power density of a particular geometry of tokamak scales with the strength of the magnetic field to the power of four, there is a huge benefit to using higher field magnets for plasma confinement.High temperature superconductors - materials that can conduct electricity without any resistance - are an enabling technology for a new generation of compact nuclear fusion reactors that are widely believed will open the door to commercialisation of fusion for energy generation. This is because state-of-the-art high temperature superconducting tapes can carry extremely high electrical currents, even when subjected to enormous magnetic fields that completely destroy superconductivity in the best low temperature superconductors. However, although high temperature superconducting materials with fantastic properties are now available in lengths up to about 1 km in the form of flexible tapes known as coated conductors, the materials are incredibly complex and sensitive to damage, making their practical deployment in magnets for fusion devices a major challenge. This programme of research involves using a unique combination of advanced materials characterisation and modelling techniques to determine how high temperature superconductors will degrade in the harsh environment of a fusion reactor where they will be continually bombarded by high energy neutrons. The focus will be on understanding the underlying damage and recovery mechanisms in these complex functional ceramics under the most realistic conditions possible. Since in operation the superconductors will be irradiated by neutrons whilst in their superconducting state at cryogenic temperatures, innovative in situ experiments will be performed to understand the differences between room temperature and low temperature radiation damage. The experimental programme will be supported by first principles modelling of pristine and defect structures in the superconducting compounds, and the outcomes will be used to validate larger scale simulations of radiation damage as well as providing key data on degradation to feed into materials selection and magnet design decisions for the next generation of fusion magnets. The advanced characterisation methodologies developed in this fellowship will also be applied to understanding radiation damage in a wider range of fusion relevant materials.