MRI: Acquisition of a High Energy Resolution Angle Resolved SpinPolarized Photoemission Instrument

技术总结：利用自旋极化光谱学，将高角分辨率和高能量分辨率与自旋分辨率相结合，对于达到对磁性和超导固体电子结构的理解水平至关重要，这是其他技术（例如，x射线磁性圆二色性，自旋极化中子散射）所无法实现的。通常为了获得较高的能量和角分辨率，会牺牲自旋信息（例如，通过自旋积分角分辨光谱学）；相反，自旋分析（例如，使用自旋极化光谱学）通常在较低的能量和角分辨率下进行。新一代电子能量分析仪的高传输率和现代光源插入装置的高通量使计数率到分辨率的限制得以克服。该项目旨在获得一种结合了能量和动量分辨率以及自旋分析的最佳通量的仪器。目前的NSLS（国家同步加速器光源）或未来的NSLS II波动器，该分析仪将附加，以及聚焦光学（微光斑尺寸），大通量（数量级比最知名的增加）和能量范围（10至4500 eV）相结合，为采集仪器和由此产生的自旋分辨电子结构测定增加了前所未有的能力。仅在NSLS的U5UA光束线上，这台仪器在北美将是独一无二的（±38º角模式，6 meV自旋分辨光电子分辨率）。当与升级后的NSLS II相结合时，该仪器将是世界上独一无二的，能够在大能量范围内探测物理上小（5微米）的磁性特征（提供元素特异性），同时具有高能量和角分辨率。从该仪器中提取的基础科学将对推进轻量化磁体、下一代超导体和开发未来磁电子设备的新机制产生直接影响。由于该仪器位于联邦实验室，拥有优化用户波束时间的既定方法，因此最大的科学和科学家将获得这些独特的功能。摘要：了解超导和磁性材料的主要进展需要了解它们的自旋极化电子结构。“自旋”是电子的一种量子力学性质，它赋予了个体磁矩，而“电子结构”可以描述固体的绝缘或金属性，并可以提供线索，说明为什么固体表现出某些物理、光学、电学或化学性质。该项目旨在获得一种最先进的仪器，可以直接探测电子与固体的结合紧密程度以及电子自旋如何相互交流，从而提供自旋极化电子结构的信息。该仪器（自旋分辨电子能量分析仪）将与同步加速器辐射源耦合，其中“同步加速器”是专门的光源，具有优势，因为它们具有较大的能量（或波长）范围，每个区域每次提供大量光子（即高强度），并且因为它们是智力和物理汇聚中心，最多的人可以使用这种能力（仪器+同步加速器）。该仪器收集的信息将有助于下一代设备中使用的材料的进步，例如内存，存储和处理组件。最后，作为该项目的一部分，波束时间提案和项目申请将与布鲁克海文国家实验室的师生团队（FaST）计划一起开发，每年夏天，一名教师和最多三名本科生将使用所要求的仪器进行研究。FaST项目分别提供旅行和住房资金，以及在夏季的十周内为学生和教师提供津贴，这使得它成为一个非常现实的项目，可以从其他没有机会的机构获得新用户。

Technical Summary: The combination of high angular- and energy-resolution with spin resolution, using spin polarized photoemission spectroscopy, is crucial for reaching a level of understanding of the electronic structure of magnetic and superconducting solids not possible with other techniques (e.g., x-ray magnetic circular dichroism, spin-polarized neutron scattering). Usually to obtain high performance in energy and angular resolution, spin information is sacrificed (e.g., by spin-integrated angle-resolved photoemission spectroscopy); conversely, spin analysis (e.g., using spin-polarized photoemission spectroscopy) is usually carried out at lower energy and angular resolution. The high transmission of the new generation of electron energy analyzers and the high fluxes available from insertion devices at modern Light Sources enables count rate-to-resolution limitations to be overcome. This project aims to acquire an instrument that combines the best possible throughput in addition to both energy and momentum resolution with spin analysis. The present NSLS (National Synchrotron Light Source) or future NSLS II undulator to which this analyzer will be attached, as well as focusing optics (micro spot size), large flux (order of magnitude increase over best known) and energy range (10 to 4500 eV) combined, add unprecedented capabilities to the acquisition instrument and resultant spin-resolved electronic structure determinations. For this instrument alone at beamline U5UA of the NSLS, it will be unique within North America (±38º angular mode, with 6 meV spin resolved photoelectron resolution). When coupled to the upgraded NSLS II, this instrument will be unique within the world, with the ability to probe physically small (5 microns) magnetic features over a large energy range (providing elemental specificity) with both high energy and angular resolution. The basic science extracted from this instrument will have direct impact in advancing lightweight magnets, next generation superconductors and in developing new mechanisms for future magnetoelectronic devices. As the instrument is housed at a federal laboratory with established methods for optimizing user beamtime, the largest cross section of science and scientists will gain access to these unique capabilities. Layman Summary: Major advances in understanding superconducting and magnetic materials require understanding their spin-polarized electronic structure. 'Spin' is a quantum mechanical property of electrons that endows an individual magnetic moment while the 'electronic structure' can describe how insulating or metallic a solid is and can provide clues as to why the solid exhibits certain physical, optical, electrical, or chemical properties. This project aims to acquire a state-of-the-art instrument that can directly probe how tightly bound electrons are to a solid and how the electron spins communicate amongst each other, hence giving information about the spin polarized electronic structure. This instrument (a spin-resolved electron energy analyzer) will be coupled to a synchrotron radiation source, where 'synchrotrons' are specialized light sources that are advantageous because of the large energy (or wavelength) ranges they provide with a large number of photons per area per time (i.e., high intensity) and because they are intellectual and physical centers of confluence where the greatest number of people may have access to such a capability (instrument + synchrotron). The information gathered with this instrument will help in the advance of materials used in next-generation devices, such as memory, storage, and processing components. Lastly, as part of this project, beamtime proposals and project applications will be developed with the Faculty and Student Teams (FaST) Program at Brookhaven National Laboratory, where each summer, one faculty member and up to three undergraduates will perform studies using the requested instrument. The FaST program separately provides both travel and housing funds, as well as a stipend to both the students and faculty during the ten weeks in summer, making this a very realistic program for obtaining new users from institutions that would otherwise not have had this opportunity.