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

技术摘要：利用自旋极化光电子能谱将高角度分辨率和能量分辨率与自旋分辨率相结合，对于达到用其他技术(例如X射线磁性圆二色谱、自旋极化中子散射)无法理解磁性固体和超导固体的电子结构的水平至关重要。通常，为了在能量和角度分辨率上获得高性能，自旋信息被牺牲(例如，通过自旋积分角度分辨光电子能谱)；相反，自旋分析(例如，使用自旋偏振光电子能谱)通常在较低的能量和角度分辨率下进行。新一代电子能量分析仪的高透过率和现代光源的插入设备提供的高通量使计数速率与分辨率的限制得以克服。该项目旨在获得一种将能量和动量分辨率与自旋分析结合在一起的仪器。目前的NSLS(国家同步加速器光源)或未来的NSLS II波荡器，以及聚焦光学(微光点大小)、大通量(比最知名的数量级增加)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确定增加了前所未有的能力。仅就NSLS的光束线U5UA上的这台仪器而言，它在北美将是独一无二的(±38度角模式，具有6 MeV的自旋分辨光电子分辨率)。当与升级的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很小(5微米)的磁性特征(提供元素特异性)，并具有高能量和高角度分辨率。从这台仪器中提取的基础科学将对发展轻质磁体、下一代超导体以及为未来的磁电子器件开发新的机制产生直接影响。由于该仪器被安置在一个联邦实验室，该实验室拥有优化用户波束时间的既定方法，最大的科学和科学家部门将获得这些独特的能力。外行人摘要：在了解超导和磁性材料方面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属性，它赋予了个人的磁矩，而“电子结构”可以描述固体的绝缘性或金属性，并可以提供线索，解释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有多紧密，以及电子自旋如何相互通信，从而提供关于自旋极化电子结构的信息。这台仪器(自旋分辨电子能量分析器)将与同步辐射光源耦合，在同步辐射光源中，同步加速器是专门的光源，因为它们提供的能量(或波长)范围很大，每一次每区域都有大量光子(即高强度)，而且因为它们是汇合的智力和物理中心，最多的人可能可以获得这种能力(仪器+同步加速器)。利用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，如内存、存储和处理组件。最后，作为该项目的一部分，将与布鲁克海文国家实验室的教师和学生团队计划(FAST)一起开发波束时间提案和项目应用程序，每年夏天，一名教员和最多三名本科生将使用所要求的仪器进行研究。FAST计划单独提供旅费和住宿费，并在夏季的十周内向学生和教职员工提供津贴，这使得这是一个非常现实的计划，可以从原本不会有这种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.