Understanding radiation damage mechanisms in high temperature superconductors for fusion applications

REBCO（稀土钡铜氧化物）第二代涂层导体带是紧凑型托卡马克聚变反应堆中磁体材料的最佳竞争者，因为它们具有优异的上级载流/磁场产生性能。辐射将各种类型的缺陷引入到REBCO晶格中，并且已知这些微结构的变化会影响关键的超导性能，例如临界电流密度和临界温度。最初，在低剂量下，辐照倾向于稍微提高超导体的临界电流密度，因为引入的缺陷充当磁通线的有效钉扎位点，使得在产生电阻之前能够承载更高的电流。然而，随着辐照剂量的增加和缺陷浓度的增加，超导性能迅速下降，最终导致超导性的完全丧失。该项目的主要目的是提高对高能粒子辐照引起的微观结构变化如何影响商业REBCO涂层导体中的磁通钉扎的理解。这对未来聚变磁体的设计者来说是至关重要的工程信息。该项目将涉及比较在伯明翰的NNUF新设施中用中子辐照的样品与在坎布里亚郡和萨里的道尔顿离子束设施中用离子辐照的替代样品。将使用位于卡勒姆聚变能中心材料研究设施的最先进的物理性能测量系统对辐照前后的超导性能进行详细表征。这是英国唯一一个可以在广泛的温度和磁场范围内测量活性超导体样品的电和磁特性的设施，所获得的结果将与STEP计划的磁体设计直接相关。先进的微观结构表征技术，包括原子分辨率透射电子显微镜，X射线衍射和X射线光谱（在钻石光源）的组合，也将用于推断辐射引入的缺陷的性质，并将辐射损伤与超导性能的变化相关联。将调查的实际相关的关键参数是辐照温度（包括在低温下的辐照）和辐照后退火的影响，以及用于评估离子辐照作为昂贵的中子损伤实验的代理的适用性的射弹类型。该项目涵盖EPSRC能源主题（磁聚变，能源材料，制造技术）和工程主题（制造技术，材料工程，工程设计）。该项目与英国原子能管理局（UKAEA）卡勒姆聚变能中心的冬青坎贝尔博士合作，其中50%的资金由UKAEA提供。这是一个为期4年的“聚变CDT”学生奖学金（部分课程费用由牛津材料基金支付）

REBCO (rare-earth barium copper oxide) 2nd generation coated conductor tapes are a top contender for the magnet material in compact tokamak fusion reactors because of their superior current carrying/magnetic field generating properties. Radiation introduces various types of defect to the REBCO crystal lattice and these changes in microstructure are known to affect key superconducting properties such as critical current density and critical temperature. Initially, at low doses, irradiation tends to improve the critical current density of the superconductor slightly because the defects introduced act as efficient pinning sites for magnetic flux lines, enabling higher currents to be carried before resistance is generated. However, as the irradiation dose increases and the defect concentration increases, the superconducting properties degrade rapidly, eventually resulting in the complete loss of superconductivity. The main aim of this project is to improve understanding of how changes in microstructure induced by irradiation with energetic particles affects flux pinning in commercial REBCO coated conductors. This is vital engineering information for the designers of future fusion magnets. The project will involve comparing samples irradiated with neutrons at the new NNUF facilities in Birmingham with proxy samples ion-irradiated at the Dalton Cumbrian and Surrey Ion Beam Facilities. Detailed characterisation of the superconducting properties pre- and post-irradiation will be carried out using a state-of-the-art Physical Properties Measurement System situated in the Materials Research Facility at Culham Centre for Fusion Energy. This is the only facility in the UK where the electrical and magnetic properties of active superconductor samples can be measured over a wide range of temperatures and magnetic fields, and the results obtained will be of direct relevance to the design of magnets for the STEP programme. A combination of advanced microstructural characterisation techniques including atomic resolution transmission electron microscopy, X-ray diffraction and X-ray spectroscopy (at Diamond Light Source), will also be used to deduce the nature of the defects introduced by irradiation and correlate irradiation damage with changes in superconducting properties. Key parameters of practical relevance that will be investigated are the effects of irradiation temperature (including irradiation at cryogenic temperatures) and post irradiation annealing, as well as the type of projectile for assessing the suitability of ion-irradiation as a proxy for expensive neutron damage experiments. This project spans the EPSRC Energy Theme (Magnetic Fusion, Materials for Energy, Manufacturing Technology) and the Engineering Theme (Manufacturing Technology, Materials Engineering, Engineering Design). The project is in collaboration with Dr Holly Campbell at the UK Atomic Energy Authority (UKAEA), Culham Centre for Fusion Energy, with 50% of the funding being provided by UKAEA.This is a 4-year 'Fusion CDT' Studentship (part of the course fee paid from Oxford Materials funds)