CHARACERIZATION OF X-RAY WINDOW SCATTERING AND FLUORESCENCE FOR SAXS STUDIES

SAXS 研究中 X 射线窗口散射和荧光的表征

• 批准号: 7722067
• 负责人: MARC NIEBUHR
• 金额: $ 0.57万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-03-01 至 2009-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7722067
• 关键词: Air; Area; Beryllium; Blood capillaries; Cells; Class; Cleaved cell; Computer Retrieval of Information on Scientific Projects Database; Containment; Effectiveness; Fluorescence; Funding; Glass; Grant; Institution; Mica; Platelet Factor 4; Quartz; Range; Research; Research Personnel; Resources; Roentgen Rays; Sampling; Silicon Dioxide; Source; Surface; Thick; United States National Institutes of Health; Vacuum; Water; capillary; detector; improved; pressure; silicon nitride; submicron

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. For the most challenging class of SAXS studies all sources of background scattering need to be eliminated or minimized, with the inevitable exception of water scattering. Sample cell x-ray windows for sample containment and vacuum path separation are primary sources of background. In order to improve the x-ray scattering facility, we have studied x-ray scattering from a variety of window materials, including silicon nitride foils, muscovite mica sheets, beryllium foils and three types of thin-wall x-ray capillaries on an absolute scale over a wide Q-range (0.01-1.2 A-1). Water and air scattering have also been recorded to re-evaluate the effectiveness of the BL4-2 in-vacuum capillary cell. The results indicate that Si3N4 is by far the best performer giving the least x-ray scattering in the entire Q range by two orders of magnitude compared to capillaries, likely due to its submicron thickness. We have verified that a 200-nm thick Si(3)N(4) window with 1 mm x1 mm area can withstand a 1 bar pressure difference, making it usable as a vacuum window. Borosilicate capillaries give slightly weaker x-ray scattering than quartz and glass capillaries, but all capillaries in particular quartz scatter relatively strongly at higher angles. X-ray scattering of 10 micron thick mica is comparable to capillaries at very small angles, but much weaker by a factor of 4 to 20 at intermediary to high scattering angles, thus making it a good choice for higher angle studies. Freshly cleaved mica scatters much less than untreated mica at small angles while sanded mica scatters orders of magnitude more strongly, indicating mica sheets should be cleaved to expose fresh surface prior to their use as an x-ray window. The use of energy-resolving Vortex detector allowed us to evaluate the contribution of x-ray fluorescence from contaminating metallic impurities within the window.

该副本是利用众多研究子项目之一 由NIH/NCRR资助的中心赠款提供的资源。子弹和 调查员（PI）可能已经从其他NIH来源获得了主要资金， 因此可以在其他清晰的条目中代表。列出的机构是 对于中心，这不一定是调查员的机构。 对于最具挑战性的SAXS研究，需要消除或最小化背景散射的所有来源，除了不可避免的水散射外。样品单元格X射线窗口用于样品遏制和真空路径分离是背景的主要来源。 为了改善X射线散射设施，我们研究了从各种窗户材料中研究的X射线散射，包括氮化硅箔，Muscovite云母云母，铍箔和三种类型的薄壁X射线毛细管在绝对尺度上以绝对尺度（0.01-1.2 A-1）（0.01-1.2 a-1）。还记录了水和空气散射，以重新评估BL4-2胶合毛细管细胞的有效性。结果表明，与毛细血管相比，SI3N4是迄今为止表现最好的X射线散射，在整个Q范围内散射最少两个数量级，这可能是由于其亚微米厚度所致。我们已经证实，具有1毫米x1毫米面积的200 nm厚的Si（3）N（4）窗口可以承受1条压力差，使其可作为真空窗口可用。硼硅酸盐毛细血管比石英和玻璃毛细血管的X射线散射略弱，但所有毛细血管尤其在较高角度相对较高。 10微米厚的云母的X射线散射在很小的角度与毛细血管相当，但在中间至高散射角度的毛细血管散射较小的毛细血管散射4至20倍，从而使其成为更高角度研究的理想选择。新鲜切割的云母的散射远小于未处理的云母，而砂云母散布的散布更强的数量级，表明应在用作X射线窗口之前切开云母片以在其使用前暴露新的表面。使用能量解析涡流检测器使我们能够评估窗户内污染金属杂质的X射线荧光的贡献。