IMPROVEMENT OF X-RAY BEAM POSITION STABILITY FOR BL4-2

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 在BL4-2启动和初步调试后，连续几天测量了x射线束在炉壳焦点处的位置。测量表明，光束的水平位置稳定在140微米以内，垂直位置移动到400微米，具有明显的昼夜特征。因此，与聚焦光束的大小(水平1.2 mm，垂直0.3 mm)相比，水平运动可以忽略不计，但需要处理垂直光束位置的变化。聚焦镜的节距变化被认为是对观察到的光束运动的主要贡献。2008年初夏安装了镜面冷却水的局部温度控制，以减少镜面冷却水的温度变化，从而最大限度地减少由于热漂移而可能对镜面位置的依赖。确实观察到了减少(到250微米)，但没有达到所需的水平。目前的方法包括实现镜面俯仰运动的电子主动反馈。

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. After the start-up and initial commissioning of BL4-2, the position of the x-ray beam at the focal point in the hutch was measured for several days. The measurements showed that the horizontal beam position was stable within 140 microns and the vertical position of the beam moved up to 400 microns with clear diurnal characteristics. Thus, compared to the size of the focused beam (1.2 mm horizontal and 0.3 mm vertical) the horizontal movement is negligible, but the changes in the vertical beam position needed to be addressed. Variations in the pitch of the focusing mirror were identified as the major contributor to the observed beam motion. Local temperature control of the mirror cooling water was installed in early summer 2008 to reduce the temperature variation of the mirror cooling water and thus minimize the possible dependence of the mirror position due to thermal drift. A reduction was indeed observed (to 250 microns) but not to the required level. Current approaches include implementation of electronic active feedback of the mirror pitch motion.