The Science and Fundamental Understanding of the Radio Frequency Surface Resistance of Nitrogen Doped SRF cavities

由该奖项促成的研究将提高对决定并可能最终限制未来粒子加速器性能的物理过程之一的理解。粒子加速器用途广泛，从用于基础粒子物理基础研究的基础研究机器，到从工业焊接到医疗诊断和治疗的工具和仪器。粒子加速器的关键限制因素之一可能是用于加速带电粒子的超导射频腔的性能。通过发现目前在这种腔内造成能量耗散的机制，我们可以将这项技术推向下一代超导粒子加速器的理论极限。该研究项目涉及培养研究生作为下一代研究领导者，拥有加速器科学和技术以及用于粒子加速器的超导材料物理和相关技术的专业知识。该奖项支持超导、射频(RF)加速器科学领域的研究和研究生教育。该奖项支持的研究旨在对用于粒子加速器最先进的射频腔中的掺氮Nb超导体的场穿透区域的物理过程有一个基本的了解。这项研究包括在亚纳米尺度上对真空-超导界面附近的亚微米深表面层进行物理和化学表征，射频屏蔽电流流经该界面。将进行从亚纳米到微米长度的表面轮廓表征，并结合通过原子探针重建、核磁共振光谱和正常金属相中的输运测量获得的局部电子和磁性。表面和屏蔽区的详细原子尺度结构将与高场条件下射频电流的最新理论建模和计算理论相结合。首要目标是将下一代超导射频腔的性能推向理论极限。

The research enabled by this award will improve the understanding of one of the physical processes that determine, and may ultimately limit, the performance of future particle accelerators. Particle accelerators have a wide variety of uses, from basic research machines for fundamental studies of elementary particle physics to tools and instruments ranging from industrial welding to medical diagnostics and treatment. One of the key limiting factors for particle accelerators can be the performance of superconducting, radio-frequency cavities that are used to accelerate the electrically charged particles. By discovering the mechanisms presently contributing to energy dissipation within such cavities, we can push the technology to theoretical limits for the next generation of superconducting particle accelerators. This research project involves the training of graduate students as the next generation of research leaders with expertise in accelerator science and technology, as well as the physics of superconducting materials for particle accelerators and related technologies.This award supports research and graduate education in the field of superconducting, radio-frequency (RF) accelerator science. The research supported by this award is directed towards a fundamental understanding of the physical processes governing the region of field penetration into Nitrogen-doped Niobium superconductors used in state-of-the-art RF cavities for particle accelerators. The research involves physical and chemical characterization, on the sub-nanometer scale, of the sub-micron deep surface layer near the vacuum-superconducting interface where the RF screening currents flow. Surface profile characterization, from sub-nano-meter to micron length scales, will be carried out, and combined with local electronic and magnetic properties obtained from atom-probe reconstruction, nuclear magnetic resonance spectroscopy, and transport measurements in the normal metallic phase of Niobium. The detailed atomic-scale structure of the surface and screening region will be combined with state-of-the-art theoretical modeling and computational theory for the RF currents under high-field conditions. The overarching goal is to push performance of next-generation superconducting RF cavities to theoretical limits.