Acquisition of a Multilayer Monochromator for a Synchrotron X-ray Microtomography Station and Education

该补助金用于为路易斯安那州立大学先进微结构和器件中心（CAMD）的同步加速器显微断层扫描站购买多层单色器。一个SXM站最近在同步加速器设施组装了一个多学科小组的物理学家，化学家和工程师。SXM站已安装在CAMD弯曲磁铁的最大能量约为15千电子伏。预计在2002年，该站将置于7.3 T摆动器光束线上，该光束线将提供50千电子伏的可用光子。虽然早期的结果非常成功，但对数据的分析突出了对单色光束的需求。当多色X射线束穿过样品时，能谱的形状随着入射能谱的较低端比较高端被吸收更多而改变。这种特性被称为射束硬化。对于在环境和生物样品中发现的较低Z元素，单色光束将有助于优化对比度，从而最大限度地减少来自光束硬化效应的图像伪影。此外，单色光束还将通过明智地选择高于和低于核心激发阈值的能量而产生的对比度来帮助化学鉴别。CAMD SXM光束线似乎是目前世界上唯一没有单色器的SXM光束线。同步辐射X射线显微层析成像（SXM）在材料、生物学、物理学、地质学和环境科学的研究中发挥着越来越重要的作用。许多应用使用层析成像技术来产生样品的三维表示。自2000年10月以来，路易斯安那州立大学的SXM站已被用于获取化学，物理，生物，海洋学，材料科学和工程等学科的图像。由于CAMD与路易斯安那州和路易斯安那州立大学的密切联系，教育和推广得到了大力强调。SXM研究项目的参与者包括当地高中生、本科研究助理（通过NSF赞助的多个REU项目）、研究生、博士后研究员以及路易斯安那州立大学和南方大学的教职员工。

This grant is for the acquisition of a multilayer monochromator for the synchrotron microtomography station at the Louisiana State University Center for Advance Microstructures and Devices (CAMD). A SXM station has recently been assembled at the synchrotron facility by a multidisciplinary group of physicists, chemists, and engineers. The SXM station has been installed on a CAMD bending magnet with a maximum energy of about 15 keV. It is anticipated that in 2002, the station will be placed on a 7.3T wiggler beamline, which will provide usable photons to 50 keV. While the early results have been highly successful, analysis of the data has highlighted the need for the monochromatic beam. As a polychromatic x-ray beam traverses a sample, the shape of the energy spectrum changes with the lower end of the incident energy spectrum absorbed more than the higher end. This property is known as beam hardening. For the lower Z elements found in environmental and biological samples, a monochromatic beam will aid in optimizing the contrast and thus minimizing the image artifacts from beam hardening effects. In addition, a monochromatic beam will also aid in chemical identification through contrast arising from a judicious choice of energies above and below core-excitation thresholds. The CAMD SXM beamline appears to be the only SXM beamline in the world currently without a monochromator. Synchrotron x-ray microtomography (SXM) is playing an increasingly important role in research in materials, biology, physics, geology, and environmental sciences. Many applications use tomographic imaging techniques to produce a three-dimensional representation of a sample. Since October 2000, the SXM station at LSU has been used to acquire images from such disciplines as chemistry, physics, biology, oceanography, material science, and engineering. Because of CAMD's close association with the state of Louisiana and LSU, education and outreach are strongly emphasized. Participants in the SXM research program include local high school students, undergraduate research assistants (through several NSF-sponsored REU programs), graduate students, post-doctoral associates, and both LSU and Southern University faculty and staff.