ADVANCED ARRAY DETECTOR FOR XRAY SPECTROSCOPY

x射线吸收光谱（XAS）是研究生物系统中各种金属位点的一种有价值的技术。该技术测量金属的核心电子态向激发态或连续态的转变。电子跃迁附近的光谱分析（x射线吸收近边结构或XANES）提供了有关金属电荷状态和几何形状的信息。吸收边缘以上的光谱分析（从边缘到边缘以上10- 15%的能量），称为扩展x射线吸收精细结构或EXAFS，提供互补的结构信息，如配体或邻近原子的数量、类型和距离。阿尔伯特·爱因斯坦同步加速器生物科学中心是美国国立卫生研究院在国家同步加速器光源的一个资源中心，它运行一条束线（X9B），并提供全面的用户支持，为美国国立卫生研究院资助的研究人员提供了10多年的x射线光谱实验。该提案要求一种先进的x射线光谱阵列探测器，其计数速度比我们现有的探测器快3倍。光束线X9B的最新改进使当前的XAS实验效率低下。现有XAS探测器的陈旧电子设备无法充分处理XAS实验中增加的4倍x射线通量。XAS是提案中列出的7个主要用户的NIH资助项目的主要组成部分。这些用户有13项NIH拨款，将从该仪器中受益。这些用户在过去三年中还使用资源中心的设施和当前的检测器发表了60多篇XAS出版物。此外，这些主要用户确定了18位NIH资助的合作者（与该提案相关的20个NIH额外拨款项目），他们将从购买该仪器中受益。XAS在X9B波束线上的可用波束时间是超额订阅的2倍。这些NIH资助的用户和他们的合作者几乎没有其他选择来完成他们的实验项目。使用新仪器将吞吐量提高三倍，对于这个生产力高、资金充足的用户群体来说将是一个巨大的好处。

X-ray absorption spectroscopy (XAS) is a valuable technique for studying a variety of metal sites in biological systems. The technique measures the transition of core electronic states of the metal to excited electronic states or continuum states. Spectral analysis near the electronic transition (x-ray absorption near-edge structure or XANES) provides information on the metal's charge state and geometry. Spectral analysis above the absorption edge (from the edge to 10-15 percent above the edge in energy), so called Extended X-ray Absorption Fine Structure or EXAFS, provides complementary structural information like, numbers, types, and distances of ligands or neighboring atoms. The Albert Einstein Center for Synchrotron Biosciences, an NIH Resource Center at the National Synchrotron Light Source, operates a beamline (X9B) and provides comprehensive user support that has provided access to x-ray spectroscopy experiments for NIH funded investigators for over 10 years. This proposal requests an Advanced Array Detector for X-ray spectroscopy that can count 3 times faster than our existing detector. Recent improvements in beamline X9B make current XAS experiments inefficient. The 4 fold increased x-ray flux now available for XAS experiments cannot be adequately handled by the antiquated electronics of the existing XAS detector. XAS is a major component of the NIH funded programs of each of the 7 major users listed in the proposal. These users have 13 NIH grants that will benefit from this instrument. These users also have over 60 XAS publications in the last three years using the facilities and current detector of the Resource Center. In addition, these major users identify 18 NIH funded collaborators (with 20 additional NIH grant programs pertinent to the proposal) who will benefit from the acquisition of this instrument. The available beamtime for XAS on the X9B beamline is 2-fold oversubscribed. These NIH funded users and their collaborators have few alternatives for completing their experimental programs. Increasing throughput by a factor of three using the new instrument would be an extraordinary benefit to this productive and well-funded user community.