BEAMLINE OPTICAL COMPONENTS & DETECTOR CHARACTERIZATION: SYNCHROTRON RADIATION

在第一次发光后的第一年（第三年的五年）， 项目），我们证明了BioCAT波荡器线是一个极好的 生物纤维衍射仪 最近的大部分 活动的目的是使其具有类似的高性能， X射线吸收光谱仪。 我们取得了 在实现这一目标方面取得了重大进展。 技术发展 包括APS调试窗口的移除， 在光谱的低能量端获得良好的通量。 另一 低能耗运行的关键发展是 低温冷却的Si（111）第一单色晶体具有 能量范围为3.4 KeV至14.6 KeV。 测量了X射线通量 在1到3 × 1013光子/秒/100毫安的范围内。 第二 单色器采用水冷Si 400晶体， 提供从7.9到33.8 keV的高能量分辨率。 我们将 在接下来的几个月里把它升级成低温晶体 获得 从稀释的样品中获得好的XAS数据是一个难题。 我们的大部分 过去一年的努力集中在提高稳定性上， 单色性和X射线探测器响应的线性。 最近，我们使用莱特尔记录了0.5 mM碳酸铜的XAS 荧光X射线检测器，具有过滤器和索勒狭缝。 我们 能够从该系统中获得良好的统计数据，在1 s/点。 多层分析仪检测器（设计用于获取数据 从稀释的样品在全通量的APS）需要X射线束 聚焦到100微米或更小，并稳定到~10 微米。 我们已接近实现这一目标。 最近的另一 显影是回转扫描，由此单色能量被 用编码的直流伺服电机连续扫描并记录数据 以防止光束中的样品劣化。 的 目前的方法允许我们在80秒内记录1000 eV的XAS扫描 分辨率约为2 eV。

In the first year since first light (year three of five for the project) we demonstrated that the BioCAT undulator line is a superb instrument for Biological fiber diffraction. The bulk of recent activities have aimed towards making it a similarly high performance instrument for X-ray absorption spectroscopy. We have made significant progress towards this goal. Technological developments that have occurred include removal of the APS commissioning window to obtain good flux at the low energy end of the spectrum. Another development essential for low energy operation was commissioning of the cryogenically cooled Si(111) first monochromator crystal with an energy range of 3.4 KeV to 14.6 KeV. The x-ray flus has been measured in the range of 1 to 3 x 1013 photons/sec/100 ma. The second monochromator was commissioned with water cooled Si 400 crystals to provide high energy resolution from 7.9 to 33.8 keV. We will be upgrading this to cryo-crystals in the next few months. Obtaining good XAS data from dilute specimens has been a struggle. Much of our effort over the past year has been focussed on improving the stability of the monochromator and linearity of response of the X-ray detectors. Recently, we recorded XAS form 0.5 mM Cu-Carbonate using a Lytle fluorescence X-ray detector with a filter and soller slits. We were able to obtain good statistics from this system in a single scan at 1 s/point. The Multilayer analyzer detector (designed to obtain data from dilute specimens at full flux of the APS) requires the X-ray beam to be focused to 100 micrometers or less and to be stable to ~10 micrometers. We are close to achieving this goal. Another recent development is slew-scanning whereby the monochromator energy is scanned continuously with an encoded DC-servo motor and data recorded on the fly to prevent deterioration of specimens in the beam. The current approach allows us to record a 1000 eV XAS scans in 80 seconds with approximately 2 eV resolution.