BEAMLINE OPTICAL COMPONENTS & DETECTOR CHARACTERIZATION: SYNCHROTRON RADIATION

从第一道光开始的第一年(五年中的第三年 项目)我们展示了BioCAT波荡器系列是一流的 生物纤维衍射仪。最近的大部分时间 活动的目标是让它获得同样高的表现 X射线吸收光谱仪。我们已经做出了 在实现这一目标方面取得重大进展。技术发展 已发生的情况包括删除APS调试窗口以 在光谱的低能端获得良好的通量。另一个 低能耗运行的发展关键是试运行 低温冷却的Si(111)第一单色器晶体 能量范围为3.4keV至14.6keV。已经测量了x射线微晕。 在1到3×1013光子/秒/100毫安的范围内。第二 单色仪用水冷的硅400晶体试运行 提供7.9至33.8keV的高能量分辨率。我们会的 在接下来的几个月里把它升级成低温晶体。获取 从稀薄的样品中获得良好的XAS数据一直是一项艰巨的任务。我们的大部分人 过去一年的努力集中在提高稳定性上。 单色仪和X射线探测器的响应线性度。 最近，我们使用Lytle记录了0.5 mm铜碳酸盐的XAS 带有滤光片和索勒狭缝的荧光X射线探测器。我们是在 能够在一次扫描中从该系统获得良好的统计数据，速度为1 S/分。多层分析仪检测器(设计用于获取数据 APS全通量下的稀释样品)需要X射线束 聚焦到100微米或更小，并稳定在~10 微米。我们已经接近实现这一目标。最近的另一次 显影是回转扫描，单色仪的能量是 用编码的直流伺服电机连续扫描并记录数据 在飞行中，以防止梁中的样品变质。这个 目前的方法允许我们在80秒内记录1000 EV 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.